Power Scaling??!?

[YellowJacket]

Can we preserve the recto roar without fizzies? Are the fizzies merely a biproduct of not running the amp hot enough?

I saw some internet literature on power scaling and I thought it was worth a discussion at least. Of course, it isn't terribly applicable to Master Volume High Gain heads where most of the tone is shaped in the pre-amp section of the amp. At best, it would be a more efficient and customizable version of a multiwatt amp. At worst, it would be just another component to break. While it may ore may not be feasible, I think it is a terribly interesting idea worth at least looking into.

In a nutshell, power scaling allows a player to adjust the 'maximum power output' of an amplifier via an extra knob. With the model I looked at, the output power can theoretically be adjusted from 100watts down to 0.01watts. The idea is that you can put your amp in the 'sweet spot' of tube saturation and turn down the 'volume' of your amp instead of the 'tone'. Great idea in theory.

As many people on a forum (Listed below) pointed out, some potential considerations are:

1) Speaker Response: Basically, you need sufficient power going through the speakers to get a certain tone. If you like the sound of speakers working and moving air, power scaling won't help you with that.

2) As you turn the wattage down, you'll end up with a 'small amp cranked' sound where you loose the power and thump you get with a 100watt high gain head, even at lower volumes. For example, when you adjust the variac switch on a Recto, it affects the tone and 'feel' of the amp. On Spongy--which is a lower wattage setting--the tight and thumpy gain tone becomes much more squishy, elastic, and anemic. Now, I noticed that Spongy can give tube growl at lower volumes but this is at the expense of raw power and a HUGE tone. Bold just sounds so much more phat and aggressive. Why would a guitarist need yet another button that tears the testicles off of his amplifier?

3) Fletcher-Munson Curve: As everyone here knows, loud music sounds different than quiet music because of how we perceive sound. As we turn our gear up louder, we will hear more bass and treble as well as less mids. Does this means that a power scaling kit is making a promise it is simply impossible to deliver.

4)On the plus side, people "CLAIM" that these things sound better than power attenuators while simultaneously being far more effective. I'd have to hear one for myself . . .

I don't know about others here but I am personally interested in any sort of good tone / ultra low volume solution because I have been in utterly paralyzing situations that require that sort of a drastic solution. I personally do not like having my amp turned down so far that the cleans are sterile and the gain is almost as fizzy and grainy as a solid state amp. I paid $$$$$$s for it, and it should sound that way. Just to have tube crunch is all I really NEED for what I mostly do with guitar, so it doesn't matter if it sounds thunderous and thumpy or not, as long as it crunches. Maybe I should just concentrate on playing instead?

Here are a few links I checked out.

From an amp builder.
http://www.londonpower.com/pscaling.htm

Of course forumites know EVERYTHING ALWAYS. **hurrhurr**
http://music-electronics-forum.com/t2996-2/

Of course I know nothing about amp building and electronics beyond how to work out impedance and how to wire a speaker cab / how to change tubes, but I think the idea is interesting.

Devils Advocate: Another point to consider - Why have I not seen any attempts to make a much less efficient guitar speaker? Would this work far better than an attenuator? I know nothing about the physics of guitar loudspeaker manufacture and I do not know if the specific (pleasing) distortion characteristics of guitar speakers can be preserved while drastically reducing the sensitivity. I just find it odd that there I don't see a record of this being attempted. Perhaps I have not looked hard enough. Basically, a 4 x 12 with 4 12" speakers putting out 86db/watt/metre would be almost as effective as running an attenuator on a fairly high setting. In this case, the inefficiency of the speaker would instead be sucking power. I can speculate that a floppy speaker cone a la greenback in a low efficiency speaker may work to replicate 'more' of a cranked tone at low volumes, especially when operating in tandem with a low power amp. The only potential problem is that perhaps the physical behavior of a guitar speaker is contingent on its high sensitivity and therefor, in this scenario, the task of engineering a guitar loudspeaker without this property would be an impossible task. Only way to find out would be to talk to a speaker builder.

As an aside: I consider that I had a valvestate minimarshall cab back in the day and the 35watt 93db/watt/metre sounded eerily similar to G12T-75s but warmer and with more cone breakup. I don't recall that they were all that quieter. I also notice that cheap computer speakers distort at surprisingly low volumes. Perhaps I am on to something here?

 

[domct203]

Devils Advocate: Another point to consider - Why have I not seen any attempts to make a much less efficient guitar speaker? Would this work far better than an attenuator? I know nothing about the physics of guitar loudspeaker manufacture and I do not know if the specific (pleasing) distortion characteristics of guitar speakers can be preserved while drastically reducing the sensitivity. I just find it odd that there I don't see a record of this being attempted. Perhaps I have not looked hard enough...................

Never heard them in person:
http://eminence.com/fdm.asp

Dom

 

[94Tremoverb]

I fitted Power Scaling to an amp once. It worked perfectly well - but to me it sounded much more like a superior form of master volume control than reducing the actual final *volume* of the amp, which is what an attenuator does (however imperfectly). I'm guessing that this is because, although you're reducing the power output, you're still keeping the big transformers and power supply components, which are now being pushed less hard. This is much more like what a master volume does than what an attenuator does. I didn't find it useless, but it wasn't the silver bullet either. I still find I get more of what I want about the sound of a big amp, quieter, using a combination of a normal MV and an attenuator. This bugs me in some ways, because I'm a tech and I don't like running components near their stress limit if I can avoid it, which is what using an attenuator does. (And IMO, what makes the sound most like that of a cranked amp, of course!) And I still think that the speakers are a big factor which no form of volume control in the amp or between the amp and cab addresses.

The variable-sensitivity speaker thing is a new one to me, and does look interesting... if you can believe the frequency response graph. I'm inherently suspicious because speaker companies all produce these things which usually look very similar, and speakers don't all sound very similar! So I wouldn't be surprised if the tone does change as you reduce the sensitivity... which may be good, or not. I've certainly tried quite a few ordinary low-sensitivity speakers, and always been disappointed in the tone once you get below about 95dB. But maybe that's just because they were crap speakers.

 

[YellowJacket]

Never heard them in person:
http://eminence.com/fdm.asp

Dom

Some youtube clips of them sound awesome and other sound like Garbage. I've read some reviews and most people opine that the low efficiency mode is a far more effective method of 'attenuation' than an attenuator. Of course, since you're just changing the efficiency of the speaker, the mechanics of it simply absorb power.
It is tempting but the price of admission seems high. Basically, it will cost probably ca. $230 for one of these units in Canada, so $460 to respeaker a 2 x 12. Another option is to outfit a 1 x 12 with one of these and I happen to have one. The only problem is that the 1 x 12 sounds like buzzy *** so I don't know if a $230 speaker can help that whatsoever. My other concern is that I dislike all of eminence's sound clips on their site. I just don't know if they do what I like.

I fitted Power Scaling to an amp once. It worked perfectly well - but to me it sounded much more like a superior form of master volume control than reducing the actual final *volume* of the amp, which is what an attenuator does (however imperfectly). I'm guessing that this is because, although you're reducing the power output, you're still keeping the big transformers and power supply components, which are now being pushed less hard. This is much more like what a master volume does than what an attenuator does. I didn't find it useless, but it wasn't the silver bullet either.

Care to elaborate? What do you mean 'superior form of master volume control'? What I dislike is fizzy buzzy bedroom recto tone. What I like is phat 'cranked' recto tone, which I find is available on my old 2 channel when the volume pot is as low as 9:00. Nothing aggravates me more than owning a high quality tube amp and being forced to run the volume so low that it sounds like a buzzy boss distortion box. If power scaling can help me with this, I'm interested. The 2 channel recto also only has a 'loop master' on it so having power scaling to use as a master volume might be helpful. Then again, the question is whether I should even bother dumping whatever $$$s into modding an amp instead of simply buying something else that does what I need. Keep in mind I run my Dual at 50watts most times (two power tubes) or even 18watts with yellow jackets.

Thoughts?

I still find I get more of what I want about the sound of a big amp, quieter, using a combination of a normal MV and an attenuator. This bugs me in some ways, because I'm a tech and I don't like running components near their stress limit if I can avoid it, which is what using an attenuator does. (And IMO, what makes the sound most like that of a cranked amp, of course!) And I still think that the speakers are a big factor which no form of volume control in the amp or between the amp and cab addresses.

Precisely. This is why eminence' new technology is so interesting. Now, I'd prefer speakers designed specifically for low sensitivity. See, it is kind of like changing tires on a car to customize the handling for different terrains. Using a dial to spin and change volume by moving internal components just seems like a compromise. i.e. paying more for a feature that I wouldn't even use.

Speaker questions: I personally don't notice a huge volume difference between a greenback and a v30. I mean it is there somewhat, but it doesn't slap me across the face. I was thinking of swapping the v30 in my small cab for another speaker. I was considering a G12H 30 but I am also strongly considering another greenback.
My one greenback is the uber expensive g12m Heritage. I'm wondering how these compare with the typical G12m 25 greenback reissue for tone. I mean I've heard that the difference is huge but I don't think I notice it all THAT much. I simply don't have funds for another $200 speaker. (MSRP of $300, those thieves) My main reason for considering Celestion is that the sensitivity of their greenbacks is 96db/watt/metre for the heritage vs the WGS Green Beret with a sensitivity of 99db / watt / metre and the Eminence version, which we won't even talk about. There are also Scumbacks which are $$$$s compared to a student budget. Since my oversized 2 x 12 does that tight modern tone, the smart thing to do is to run the other cab for a vintage vibe. I just would like to run as low sensitivity speakers as possible since my vintage unit is also specialized for low volume situations.
So, is the Greenback Reissue worth putting next to the G12m Heritage in a cab? Would I be better off with another Heritage? If I was to go with a G12H I would definitely get the WGS model instead since it is so much less $$$s new. I know this sounds like I am arguing with myself in my head but keep in mind that I often encounter situations where I am trying to turn volume both up and down by a hair on the knob, and it is in that picky range where the amp goes from off to on.

The variable-sensitivity speaker thing is a new one to me, and does look interesting... if you can believe the frequency response graph. I'm inherently suspicious because speaker companies all produce these things which usually look very similar, and speakers don't all sound very similar! So I wouldn't be surprised if the tone does change as you reduce the sensitivity... which may be good, or not. I've certainly tried quite a few ordinary low-sensitivity speakers, and always been disappointed in the tone once you get below about 95dB. But maybe that's just because they were crap speakers.

The one complaint I heard was that this particular speaker became bass heavy at low volumes. Guess you have to run them with a bright sounding cab or at least dial down the lows for those quiet tones.


So, is it worth what will balloon to probably $400 at the end of the day to quiet down my setup further or would it be better to invest in a separate amp for low volume playing? i.e. 18watt plexi clone with high gain mod and power scaling in a 1 x 12 combo with an Eminence Reignmaker speaker. =-/

 

[94Tremoverb]

Care to elaborate? What do you mean 'superior form of master volume control'? What I dislike is fizzy buzzy bedroom recto tone. What I like is phat 'cranked' recto tone, which I find is available on my old 2 channel when the volume pot is as low as 9:00. Nothing aggravates me more than owning a high quality tube amp and being forced to run the volume so low that it sounds like a buzzy boss distortion box. If power scaling can help me with this, I'm interested. The 2 channel recto also only has a 'loop master' on it so having power scaling to use as a master volume might be helpful. Then again, the question is whether I should even bother dumping whatever $$$s into modding an amp instead of simply buying something else that does what I need. Keep in mind I run my Dual at 50watts most times (two power tubes) or even 18watts with yellow jackets.

Thoughts?

Basically I thought it gave a better sound than a master volume (no low-volume fizzy tone) but lacked the depth, dynamics and 'breathy' character of a cranked-up amp, so in that sense it still sounded more like a MV than an attenuator, to me. Whether that's what you want, I don't know - it might be, since I seem to remember you're looking for a tighter hard-rock/metal tone anyway (whereas I'm really looking for a looser high gain vintage-type tone). However, it's still a lot of money for a permanent modification to your amp that you then can't use with any other amp, so not very flexible.

The actual cause of the poor low-volume tone may even be as simple as the MV pot itself, when it's turned down that far - the resistance to ground gets low and the series resistance above it gets high, which means it starts to interact with other components and stray capacitance in ways that don't sound good. I modded my old DC-5 to smooth out the taper of the pot and that removed the 'step' in the response to a great extent, but since that was *removing* an extra component that the Rectifiers don't have, it may not be possible to achieve the same thing.

Speaker questions: I personally don't notice a huge volume difference between a greenback and a v30. I mean it is there somewhat, but it doesn't slap me across the face.

I hear it, but it doesn't quite sound like 3dB to me - maybe 1 or 2.

I was considering a G12H 30 but I am also strongly considering another greenback.

I don't hear even that much volume difference between the G12M-25 and the G12H-30, due to the H30's much cleaner sound I think - they sound almost the same volume. I would definitely stick with two different speakers though.

My one greenback is the uber expensive g12m Heritage. I'm wondering how these compare with the typical G12m 25 greenback reissue for tone. I mean I've heard that the difference is huge but I don't think I notice it all THAT much.

It's there, but I wouldn't describe it as huge. I'm also not sure now much of it is due to break-in - the Chinese 25s are really tight out of the box, but I think part of the Heritage thing is that they're broken in a bit at the factory (although I could be wrong on this). I've never compared a brand new Heritage to a brand new Reissue yet.

My main reason for considering Celestion is that the sensitivity of their greenbacks is 96db/watt/metre for the heritage vs the WGS Green Beret with a sensitivity of 99db / watt / metre and the Eminence version, which we won't even talk about.

Be careful with different makers' dB figures - they don't always seem to equate to each other. I haven't tried any WGS speakers but my impression from hearing Eminences is that their sensitivity figures are quite optimistic compared to Celestion's - they just don't sound any louder than a Celestion with apparently 2 or 3dB less quoted sensitivity. I also think the same about their power ratings - Celestions are really conservatively rated and will take a cranked amp of the quoted power, usually. Eminences... won't. (Nor Jensens.)

Personally, I've never really liked any Eminence speaker I've ever heard except for those huge vented magnet "Fender Special Design" jobs that Fender put in the Red-Knob Twin and and other amps like that. But maybe it's just me.

I know this sounds like I am arguing with myself in my head but keep in mind that I often encounter situations where I am trying to turn volume both up and down by a hair on the knob, and it is in that picky range where the amp goes from off to on.

That's exactly why I use an attenuator even when I'm not cranking the amp fully. You can knock off just a small amount with it, well within the range it doesn't much (if at all) affect the tone.

The one complaint I heard was that this particular speaker became bass heavy at low volumes. Guess you have to run them with a bright sounding cab or at least dial down the lows for those quiet tones.

Given the way it works, that doesn't surprise me at all. More of a compromise than an attenuator, or a master volume? Or just different? I don't know... but more expensive than an attenuator if you need more than one, and still less flexible.

So, is it worth what will balloon to probably $400 at the end of the day to quiet down my setup further or would it be better to invest in a separate amp for low volume playing? i.e. 18watt plexi clone with high gain mod and power scaling in a 1 x 12 combo with an Eminence Reignmaker speaker. =-/

Bear in mind that no kind of 18W amp sounds like a 100W amp but quieter, no matter that they all go on about "Plexi tone at lower levels".

To me, still nothing sounds more like a big amp, but quieter, than a big amp run through a good attenuator does - at least if you're not trying to crank a big non-MV amp fully then reduce it to bedroom level. It's certainly closer than a lower-powered amp.

 

[YellowJacket]

Basically I thought it gave a better sound than a master volume (no low-volume fizzy tone) but lacked the depth, dynamics and 'breathy' character of a cranked-up amp, so in that sense it still sounded more like a MV than an attenuator, to me. Whether that's what you want, I don't know - it might be, since I seem to remember you're looking for a tighter hard-rock/metal tone anyway (whereas I'm really looking for a looser high gain vintage-type tone). However, it's still a lot of money for a permanent modification to your amp that you then can't use with any other amp, so not very flexible.

You are correct. I definitely like what can be described as a tight hard-rock / undergained metal tone, for one of my applications. (Metal tone proper sounds oversaturated to me) The other tone I like is a more mid heavy almost punk rock crunch, although it still sounds fairly modern. The sound of every component in an amp straining under pressure is not my thing. Instead, I prefer angry, GROWLING tubes!!!

See, now we are getting somewhere. Non fizzy low volume tone sounds great and I should mention that I prefer the tightness of running a Dual at 50watts with 2 power tubes or even at 20watts with 2 YellowJackets / EL-84s. (I haven't ran 100watts for guitar in AGES) Of course I realize that there is no 'silver bullet' for cranked tones in an apartment but what I am really going for is a tube amp that still SOUNDS like a tube amp, even with the volume set to 1 or 0.5.

The situation I am in basically disallows the sort of volume one gets from the Red channel running on the modern voicing. Only the red channel set to vintage with the variac set to spongy can even come close to giving me the tube breakup I desire. It causes me ample frustration and makes such solutions as an AxeFX or even a POD seem preferable. I'm still holding off because I just prefer a proper tube amp to any other option!

Some Questions:

1) Would I be able to run 2 EL-34s or 2 YellowJackets / EL-84s with power scaling?

2) Does power scaling basically make the variac switch irrelevant? As far as I understand it, power scaling is like a "variac knob" instead of a "variac switch". The way the Mesa Manual explains the variac switch, it seems to me that the switch lowers the plate voltage which lowers the output of the power section thereby allowing power tube breakup at lower volumes. i.e. if you add a power scaling knob, it turns down from bold on 10 to spongy on 7; then to very spongy on 4; and then all the way to 'marshmallow' on 3 or 2. Of course I know nothing of how tube amp circuitry actually works so I could be way off on this.

3) How much is EXPENSIVE? They have a kit available at London Power for $79 CAD. Of course a Tech would need to do the work since PCB amp + Me + Soldering Iron = Disaster.

4) How much do severely underpowered speakers contribute to fizzy low volume tones? Are we potentially all looking at the wrong piece of equipment as the culprit?

The actual cause of the poor low-volume tone may even be as simple as the MV pot itself, when it's turned down that far - the resistance to ground gets low and the series resistance above it gets high, which means it starts to interact with other components and stray capacitance in ways that don't sound good. I modded my old DC-5 to smooth out the taper of the pot and that removed the 'step' in the response to a great extent, but since that was *removing* an extra component that the Rectifiers don't have, it may not be possible to achieve the same thing.

VERY interesting. I noticed that no matter what tube configuration I use (Yellowjackets, 2 EL-34s, 2 6L6s, 4 6L6s), good tone is always possible starting at the same position on the Master Volume pot on both the Orange and the Red channel. This definitely could be why. As you mentioned, having an overall master volume as well as independent channel volumes does not correct the fizziness problem. If power scaling removes this, it would definitely be ideal for my purposes. Of course, if there is a less expensive way to accomplish this feat, that would be preferable. The only potential drawback to this solution would be that Red channel set to Modern is still unusable because of that extra gain stage smoking the power section. It basically is either 'OFF' or 'Too **** LOUD' and there is no middle ground. This really sucks since Red to Modern is my preferred rhythm tone by far.

At any rate, this definitely nails down either the speakers and/or something in the preamp architecture as a potential culprit.

I hear it, but it doesn't quite sound like 3dB to me - maybe 1 or 2.

Agreed.

I don't hear even that much volume difference between the G12M-25 and the G12H-30, due to the H30's much cleaner sound I think - they sound almost the same volume. I would definitely stick with two different speakers though.

Hmm. I've just got this thing for that G12m midrange crunch. In fact, when I record my theile, I'm always trying to turn 'up' that distinctive G12m crunch while turning down the v30. Now that I have the modern tone covered, speaker selection is definitely a VERY tough call for me. Still on the fence waffling between a G12H 30 or a second G12m. (the added bite and low end tightness of a G12H 30 could be profitable but what about that creamy crunch?)

It's there, but I wouldn't describe it as huge. I'm also not sure now much of it is due to break-in - the Chinese 25s are really tight out of the box, but I think part of the Heritage thing is that they're broken in a bit at the factory (although I could be wrong on this). I've never compared a brand new Heritage to a brand new Reissue yet.

I have a G12m Reissue and a G12m Heritage. The trouble is that the G12m Reissue is in a Gawd Awful Peavey 1 x 12 cab and EVERYTHING sounds awful in there. In spite of the different cabs, the speakers still sound surprisingly similar. The number of hours on a speaker is definitely a confounding variable for differences between vintage and new gear, something guitarists often overlook. The whole 'heritage' thing really sounds like a cash grab on the part of Celestion.

Be careful with different makers' dB figures - they don't always seem to equate to each other. I haven't tried any WGS speakers but my impression from hearing Eminences is that their sensitivity figures are quite optimistic compared to Celestion's - they just don't sound any louder than a Celestion with apparently 2 or 3dB less quoted sensitivity. I also think the same about their power ratings - Celestions are really conservatively rated and will take a cranked amp of the quoted power, usually. Eminences... won't. (Nor Jensens.)

Interesting . . . and not surprising.
WGS rates many of their models at 99db/watt/metre including the Green Beret (greenback, but with a 105Hz cone instead of am 85Hz one) Reaper 30 (G12H 30 Anniversary) Reaper 55Hz (G12H Heritage). Surprisingly, the Veteran 30 (v30 minus the upper mid spike) is rated much lower than a Celestion Vintage 30 at 98 DB/watt/metre. (the Retro 30, a high power V30 clone, puts out 100DB/Watt/Metre)

Personally, I've never really liked any Eminence speaker I've ever heard except for those huge vented magnet "Fender Special Design" jobs that Fender put in the Red-Knob Twin and and other amps like that. But maybe it's just me.

Agreed. All eminence sound clips I have heard sound terrible. The WGS ones, by comparison, are definitely on par with Celestion in terms of tonal quality. The WGS speakers often are slighly 'tweaked' to remove the annoying characteristics of the originals. Personally, I think the Reaper HP (50watt version of G12H) is an astounding speaker from them but it just doesn't do what I want from this cab. I was suitably impressed when I loaded a 2 x 12 with them for my brother, almost enough to provoke me into making a third cab . . .

The one complaint I heard was that this particular speaker became bass heavy at low volumes. Guess you have to run them with a bright sounding cab or at least dial down the lows for those quiet tones.

Given the way it works, that doesn't surprise me at all. More of a compromise than an attenuator, or a master volume? Or just different? I don't know... but more expensive than an attenuator if you need more than one, and still less flexible.

The reviews (if they are to be trusted) state that the low efficiency speaker is a better alternative than an Attenuator, power scaling, and basically all other methods used to neuter amps. The argument is that there is no potential tone sucking in the signal chain; and since the amp interacts directly with the speaker, no dynamic interaction between the amp and speaker are lost. Yes, it definitely sounds too good to be true. The biggest issue I have is that I generally do not like Eminence speakers.

So, is it worth what will balloon to probably $400 at the end of the day to quiet down my setup further or would it be better to invest in a separate amp for low volume playing? i.e. 18watt plexi clone with high gain mod and power scaling in a 1 x 12 combo with an Eminence Reignmaker speaker. =-/

Bear in mind that no kind of 18W amp sounds like a 100W amp but quieter, no matter that they all go on about "Plexi tone at lower levels".

To me, still nothing sounds more like a big amp, but quieter, than a big amp run through a good attenuator does - at least if you're not trying to crank a big non-MV amp fully then reduce it to bedroom level. It's certainly closer than a lower-powered amp.

Ya, if you want a big amp use a big amp. I think the issue is that I want a big amp for big things and a small amp for small things but I have a shortage of $$$s. Furthermore, I generally like the voicing of a Dual Recto and I totally would love to have that preamp available for low volume applications as well.

 

[94Tremoverb]

The sound of every component in an amp straining under pressure is not my thing. Instead, I prefer angry, GROWLING tubes!!!

I like both. Imagine what Neil Young would sound like playing a Tremoverb. (From a safe distance, probably .)

Some Questions:

1) Would I be able to run 2 EL-34s or 2 YellowJackets / EL-84s with power scaling?

Yes - EL34s definitely. Power scaling works simply by varying the HT voltage - and bias voltage, in a fixed-bias amp - but Yellowjackets ignore the bias voltage, so they won't be affected by that. But there is a possibility that they might not work when the plate voltage goes below a certain threshold - they contain some extra circuitry to reduce the voltage anyway, so combining the two things will certainly work when the plate voltage is in the region of the normal amp voltage, but maybe not once it gets down to about the amount the Yellowjacket is reducing it by, if that makes sense. I don't know for sure, and although I can't see why it would do any harm even if it doesn't work, it may be worth calling THD to check.

2) Does power scaling basically make the variac switch irrelevant? As far as I understand it, power scaling is like a "variac knob" instead of a "variac switch". The way the Mesa Manual explains the variac switch, it seems to me that the switch lowers the plate voltage which lowers the output of the power section thereby allowing power tube breakup at lower volumes. i.e. if you add a power scaling knob, it turns down from bold on 10 to spongy on 7; then to very spongy on 4; and then all the way to 'marshmallow' on 3 or 2. Of course I know nothing of how tube amp circuitry actually works so I could be way off on this.

No, you're dead right. The difference is that the 'variac' switch affects every voltage in the amp, including the tube filaments and the bias (but not in a controllable way, just by the same ratio as the plate voltage) whereas power scaling affects only the plate voltage and the bias (but in a controllable way) - so one problem of the Spongy mode is that the tube filaments run too cold (less cathode emission) and the bias actually doesn't drop far *enough*, so the tubes now run much too cold. Power scaling can avoid that by how you set the ratio of the bias compensation circuit. You could actually use both, but there would be no real point and it would be better to use power scaling on the Bold setting to keep the filaments at the proper voltage.

3) How much is EXPENSIVE? They have a kit available at London Power for $79 CAD. Of course a Tech would need to do the work since PCB amp + Me + Soldering Iron = Disaster.

The one I did - which was the simplest version, on a cathode-bias amp, so only about two-thirds of the work - was about a $150 job, five or so years ago. I would guess a full job on a fixed-bias amp would run at around $200 or more.

4) How much do severely underpowered speakers contribute to fizzy low volume tones? Are we potentially all looking at the wrong piece of equipment as the culprit?

I'm not sure, but I don't think very much - I once had a ZVex Nano amp (half a watt fully cranked!) which sounded fine through a 4x12", although that's actually still maybe not far off the 9 o'clock level, half a watt is surprisingly loud...! I had to make a little attenuator for it, and no I'm not joking .

As you mentioned, having an overall master volume as well as independent channel volumes does not correct the fizziness problem. If power scaling removes this, it would definitely be ideal for my purposes. Of course, if there is a less expensive way to accomplish this feat, that would be preferable. The only potential drawback to this solution would be that Red channel set to Modern is still unusable because of that extra gain stage smoking the power section. It basically is either 'OFF' or 'Too **** LOUD' and there is no middle ground. This really sucks since Red to Modern is my preferred rhythm tone by far.

This is exactly why I ended up with the attenuator as the solution - you can just set the amp where you want, then knock off the excess volume. It definitely *doesn't* mean you have to crank up the amp loud, if you don't want to (contrary to what every attenuator manual seems to say).

At any rate, this definitely nails down either the speakers and/or something in the preamp architecture as a potential culprit.

I do actually think it's more do with the preamp, but I could be wrong.

Still on the fence waffling between a G12H 30 or a second G12m. (the added bite and low end tightness of a G12H 30 could be profitable but what about that creamy crunch?)

The H30 is certainly more 'vintage' than 'modern' sounding, even though it doesn't have the same 'dirty' tone as the 25.

The whole 'heritage' thing really sounds like a cash grab on the part of Celestion.

Sadly, even though I would love to support British industry and to believe that there is a huge and valuable difference between them, I think I may have to agree. I just can't see where there could be enough differences in the construction to make *that* much difference to the sound.

Surprisingly, the Veteran 30 (v30 minus the upper mid spike) is rated much lower than a Celestion Vintage 30 at 98 DB/watt/metre. (the Retro 30, a high power V30 clone, puts out 100DB/Watt/Metre)

I wonder if the Veteran has a more heavily doped cone? That might give both results...

The reviews (if they are to be trusted) state that the low efficiency speaker is a better alternative than an Attenuator, power scaling, and basically all other methods used to neuter amps. The argument is that there is no potential tone sucking in the signal chain; and since the amp interacts directly with the speaker, no dynamic interaction between the amp and speaker are lost.

This is where I get suspicious, where people start quoting theoretical reasons why something is "purer" and so cannot "suck tone".

In fact, by altering the magnetic characteristics of the speaker, it's almost a certainty that the tone *will* be changed, and quite possibly by much more than by just adding a bit of resistance into the signal path or altering the amp's internal voltages. Essentially, if you change the magnetic field you're making a different speaker - that's exactly why M and H magnet speakers sound different from each other even with the same cone types. The trick will be to try to *stop* that happening - if they've been able to achieve it it's quite a feat and may explain the cost of the speakers.

The biggest issue I have is that I generally do not like Eminence speakers.

Exactly.

Furthermore, I generally like the voicing of a Dual Recto and I totally would love to have that preamp available for low volume applications as well.

I have another idea...

If Yellowjackets operate in Class A - which they don't technically, but they may be close enough to it for this to work - you could try running just *one* in the amp - which should give you around 5W. (Not 10W - the power output is related to the square of the voltage output, which is halved if you take away one half of a push-pull power stage, so you get one-quarter of the power.) This is like how the Express amps do it, only manually! You can't do this with one 6L6 or EL34 because the bias point is wrong and the waveform will be too cut-off on one side (which sounds bad), but with a Yellowjacket you may be in with a chance. You will probably get some extra hum, because the OT will be a bit unbalanced (in the Express, they run the other tube at idle with no signal, to balance the current), but maybe not enough to be a problem. You should also run the amp at 4 ohms even with a 16-ohm cab, and certainly with an 8 - the impedance of just one EL84 is way too high otherwise.

 

[YellowJacket]

For the record, my 8 ohm G12m 25 reissue is made in England. According to the date stamp, it was made in 1990. I guess I can't comment on chinese made Greenbacks after all.

As for power scaling, I'm beginning to think it is a lot of money for something that really isn't necessary on a Dual Rectifier. If I had an Electra Dyne, I'd be more likely to have it modded this way, especially since the power amp is important to adding gain to that amp. An attenuator sounds like a better solution but it is still a lot of money, $400+ for a good one. I'm not quite sure what to do. Thinking of selling my Dual and buying a used roadster head . . . Not sure though. We'll see.

 

[screamingdaisy]

The most effective method I've ever found of reducing volume is running the amp into a dummy load with a line out, then running the line out into a second amp that's plugged into a cab. I did it with a Hotplate slaved into the power section of a separate tube head, but I've heard that the Ultimate Attenuator is based around this same principal... only using a built in solid state amp.

That said, I never did the above test with a Recto. And even though it worked well I never ran my rig that way because it seemed to be a waste running a two 100w power sections slaved into each other in an effort to get good low volume tone.... I stuck to using the MV because although it was a compromise I thought it was an effective compromise.

Also, how low exactly do you want to be able to play? When I said that the Roadster is better at lower volumes than my old Recto I wasn't kidding, but low volumes to me is somewhere around 9:00 on the master volume knob. It does fizz/sizzle a bit at that volume, but I don't mind it as much because the low end girth is there. I haven't actually tried to run it at mouse fart volumes yet so I don't know how it'll behave at those volumes.

 

[YellowJacket]

Hmmm. My Dual sounds awesome at 9:00 on the channel volume (I don't use the FX loop). This is where it really comes alive! It is at mouse fart volumes when I start to get mad at it. The Ho Ultimate Attenuator costs $400+ which just is not easy to afford right now.

I think the allure of the Roadster is the excellent clean channels as well as the low gain modes available. For instance, I think 'raw' sounds great! I get by with what I have but I can tell I really am not 100% satistified, something that sucks on a student budget!

 

[94Tremoverb]

I don't think you need to spend $400 on a Ho/Ultimate Attenuator (which as screamingdaisy said, isn't really an "attenuator" in the normal sense at all, but a dummy load/solid-state re-amp system built into one box) to do the job. I have both the Hotplate and the Marshall Powerbrake, and while both of them do have well-known limitations when you try to use them *on their own* to reduce for example a non-MV 100W amp down to bedroom volume, they work far better when used more moderately. I honestly don't think there is any very significant "tone loss" over the first few clicks on either of them - what you're really hearing is the psycho-acoustic effect of the volume reduction. But actually if you take those sounds, record them and play them back at the same level as a recording of the unattenuated sound, it's hard to hear a difference.

The way I do it for really low-volume playing is to get the amp up only just loud enough for it to start sounding good using the MV (ie the 9-10 o'clock position) and then attenuate down from there. This sounds so much better than cranking the amp up full and attenuating heavily that it's a mystery to me why this approach is not more widely known or popular - and even advised against in the Hotplate manual, they suggest to turn the MV up full.

Of the two, the Marshall actually sounds more 'linear' in terms of retaining the exact same sound as you turn it down (at least until it's more than about halfway down - it does get muffled/buzzy at very low settings) and is tighter; the Hotplate allows you to deliberately add bass and treble back in (kind of like a loudness button) and makes the amp sound more squashy and compressed, which I like - so I prefer the Hotplate for getting the cranked-up character at very low volume, but I suspect that it you want a more focused sound the Marshall might have the edge. Neither of them should cost anything like $400 - the Marshall is discontinued now so used is the only way.

 

[YellowJacket]

What is the deal with the different impedances listed for all the THD hotplate models?

For instance, I'm always running my amp with less tubes and my 2 2 x 12s have different impedances. It would be handy to be able to run both 16 ohms and 8 ohms with an attenuator. Could I get by with just an 8 ohm Hotplate or just a 16 ohm Hotplate?

If I got one, I would DEFINITELY run the amp just loud enough to sound good and knock off volume. Anything else smacks of sending my amp to an early grave.

 

[94Tremoverb]

The Hotplates are indeed impedance-specific, but what's useful to know is that they err on the low side compared to a real speaker - so it's safe to use a 16-ohm Hotplate with an 8-ohm amp, but not the other way round. The Marshall by comparison errs on the high side, although it does have both 8 and 16-ohm settings, but because of that I would not use it with a 4-ohm amp even on the 8-ohm setting.

An important thing about all attenuators is that once you get much beyond 3dB attenuation - which on most is the first click, and at which point the attenuator taking half the power from the amp - and certainly below 6dB where it's taking three-quarters of the power, the attenuator is the bulk of the load, and so you need to match the amp and the attenuator if possible, but matching the speaker is much less important. So you could for example run a 16-ohm amp into a 16-ohm attenuator, and as long as you were running at least 6dB of attenuation you could use a 4-ohm cab with no problem, because all the amp really sees is the attenuator.

Also, accurate impedance matching only matters when the power stage is being driven hard. At anything below half of full power (relative to the tubes, if you're running less than the full set) it really doesn't matter at all for safety, although it may a little for tone. But if you're only just turning up the amp far enough to sound good, it really doesn't matter at all.

So, if you have 8 and 16-ohm cabs I would get a 16-ohm Hotplate. I have a 16-ohm one, which I use with the amp at both 16 ohms and 8 ohms as the mood takes me - it sounds different, more compressed at 16 ohms, and tighter at 8 because the amp is being loaded less heavily. I don't use it at 16 ohms if I'm really cranking it because I know from the impedance curve of the Hotplate that it is really putting more stress on the tubes like that (and I have some very expensive power tubes in it!), but for low MV settings it sounds better at 16.

 

[Neptical]

YellowJacket,

You sound like you would be right at home with a Mark series amp. (IMO)



~Nep~

 

[YellowJacket]

The Hotplates are indeed impedance-specific, but what's useful to know is that they err on the low side compared to a real speaker - so it's safe to use a 16-ohm Hotplate with an 8-ohm amp, but not the other way round. The Marshall by comparison errs on the high side, although it does have both 8 and 16-ohm settings, but because of that I would not use it with a 4-ohm amp even on the 8-ohm setting.

An important thing about all attenuators is that once you get much beyond 3dB attenuation - which on most is the first click, and at which point the attenuator taking half the power from the amp - and certainly below 6dB where it's taking three-quarters of the power, the attenuator is the bulk of the load, and so you need to match the amp and the attenuator if possible, but matching the speaker is much less important. So you could for example run a 16-ohm amp into a 16-ohm attenuator, and as long as you were running at least 6dB of attenuation you could use a 4-ohm cab with no problem, because all the amp really sees is the attenuator.

Also, accurate impedance matching only matters when the power stage is being driven hard. At anything below half of full power (relative to the tubes, if you're running less than the full set) it really doesn't matter at all for safety, although it may a little for tone. But if you're only just turning up the amp far enough to sound good, it really doesn't matter at all.

So, if you have 8 and 16-ohm cabs I would get a 16-ohm Hotplate. I have a 16-ohm one, which I use with the amp at both 16 ohms and 8 ohms as the mood takes me - it sounds different, more compressed at 16 ohms, and tighter at 8 because the amp is being loaded less heavily. I don't use it at 16 ohms if I'm really cranking it because I know from the impedance curve of the Hotplate that it is really putting more stress on the tubes like that (and I have some very expensive power tubes in it!), but for low MV settings it sounds better at 16.

Interesting. How much did the hotplate run you? I'm seeing some stupid high used prices on Ebay, which is most likely indicative of a high demand. In Canuck dollars, the hotplate will cost in the neighbourhood of $325 before sales tax, which dumps an additional $45 or so on the price. **annoying**

YellowJacket,

You sound like you would be right at home with a Mark series amp. (IMO)



~Nep~

Well, this is my dill-lemon. *MY* tone is pretty much the Electra Dyne so ideally I'd want the feature set of a Mark V with the tone of an Electra Dyne. THAT would be my ideal amp. I happen to think Mark series amps are incredible but it just isn't *MY* tone, if you know what I mean. I'm much more in the Marshall crunch camp and I can get great tones out of JCM2000 heads, even though I know guys hate them. In fact, I dial in a very similar tone on a JCM2000 as I do on my Dual Recto loaded with EL-34s. Those tubes are pretty much a permanent fixture in that amp! The *problem* I keep running into is this volume issue. Now, you put a drum kit next to me and I need to recruit the full power of my rig, but for these inane low volume situations nothing works. That is really the problem. There is nothing that is worse than playing guitar when you hate your tone and this has generated no end of frustration for me, especially when I know how good it can sound one more clock hour over on the MV knob.

 

[94Tremoverb]

How much did the hotplate run you? I'm seeing some stupid high used prices on Ebay, which is most likely indicative of a high demand. In Canuck dollars, the hotplate will cost in the neighbourhood of $325 before sales tax, which dumps an additional $45 or so on the price. **annoying**

About that in the UK too. Someone I know who is getting theirs replaced (Marshall Super Bass blew it... yeah I know they're supposed to be rated for 180W!) says THD can't supply one just now, so I'm guessing they're back-ordered and that may account for the high used prices.

I would definitely look into the Powerbrake too, I think they should be cheaper. Yes, I know all about the very bad rap it gets all over the net... personally I have not found that and in fact I think it sounds as good or better than the Hotplate at most settings. (And miles better than the Weber Minimass I tried which everyone else seems to love. I also got good results from the Dr.Z Airbrake, if you can find one of those.) It's also more flexible in having 8 and 16-ohm input settings, and closer spaced attenuation steps (3dB not 4dB), but less in having no 'loudness' switches, continuously-variable very-low-volume setting, or line output. But if forced to keep just one, it would probably be the Powerbrake. And no I'm not going to sell you my Hotplate! - too expensive from over here anyway.

 

[YellowJacket]

About that in the UK too. Someone I know who is getting theirs replaced (Marshall Super Bass blew it... yeah I know they're supposed to be rated for 180W!) says THD can't supply one just now, so I'm guessing they're back-ordered and that may account for the high used prices.

I would definitely look into the Powerbrake too, I think they should be cheaper. Yes, I know all about the very bad rap it gets all over the net... personally I have not found that and in fact I think it sounds as good or better than the Hotplate at most settings. (And miles better than the Weber Minimass I tried which everyone else seems to love. I also got good results from the Dr.Z Airbrake, if you can find one of those.) It's also more flexible in having 8 and 16-ohm input settings, and closer spaced attenuation steps (3dB not 4dB), but less in having no 'loudness' switches, continuously-variable very-low-volume setting, or line output. But if forced to keep just one, it would probably be the Powerbrake. And no I'm not going to sell you my Hotplate! - too expensive from over here anyway.

This is when I wish you brits were alive and kicking this time of day. I forgot to ask what a reasonable used price was for a Marshall Power Brake!

I tried an amp that does power scaling today. It was a flavour of egnater that goes from 1 watt to 30 watts. Turning the power of the amp down didn't really make it sound mushy or squishy, and it really didn't lower the volume in a noticeable way. It basically made it easier to overdrive the power section of the amp at 'lower' volumes compared to when running at 30 watts. That being said, it still was BALLS LOUD! I was disappointed that the perceived volume only dropped about 1/4th or 1/3th of what it was and I couldn't even really tell the knob was working all that much. I understand that the units from London Power go from 100 watts all the way to 0.1 watts so I figure that this should make a slight bit bigger of a difference. I assume that 0.1 watts will sound 1/8th as loud as 100 watts. Overall, I was impressed with the lack of tonal decay I heard with the power scaling but I was really disappointed with the lack of drop in perceived volume. The overall bigness / grunt / aggression / thump of the amp never really changed, like how the tone of a Dual changes with the variac switch. THAT was encouraging.

While this feature is a different knob to dial different tones out of one's amp, it really wasn't as effective at the bedroom tones as I expected. The Electra Dyne we tried yesterday was capable of better tones at lower volumes on the 45 watt mode than what we were hearing here at 1 watt. =-/ I REALLY WISH I could test both power scaling and an attenuator with my Dual BEFORE spending cash on it . . . =-/

 

[94Tremoverb]

I forgot to ask what a reasonable used price was for a Marshall Power Brake!

Not sure, where you are. In the UK they're a little cheaper than a Hotplate, but that may be just because they were made here. Probably the best thing to do is to buy either a Hotplate or a Powerbrake used, and see what it sounds like - the Hotplate at least should be easy to re-sell if it doesn't do the job.

 

[screamingdaisy]

I've owned 3 Hotplates and each time I've sold them they've gone fast.

Buy used and you shouldn't take a loss on it.

 

[YellowJacket]

Good point. This way I won't have to have holes drilled in my amp's chassis for a procedure I may not like!