Simul-Class v Non-Simul-Class

[macstrat]

Hi everyone,
I'm looking for a Mark III combo here in the UK (why must Boogies be SO expensive here ?) and wanted people's opinions on Simul-class. Is it significantly better than a non-Simul-class amp, and what are the differences tonally ?
Also, I saw another post which described the Mk III clean tone as being similar to a DC-5. This worries me a bit as I sold a DC-3 because I wasn't crazy about the clean tone. Is the DC-3 clean the same as the DC-5 (6L6s v EL84s would make a difference I think) and is the other post accurate ?
Thanks for any advice,
MacStrat

 

[AdmiralB]

I'd be extremely surprised to see someone pass a double-blind test with SC versus non-SC on an amp operating at "moderate" and below volume.

All SC is, is two tubes out of the four wired as triodes into a slightly different load. The bias for them is different (at least in the amps built for EL34s). It's really a misnomer, it has nothing to do with operating class.

You could take a non-SC amp and convert it to 95% identical to SC fairly simply.

 

[Elpelotero]

Simul-Class on a Mesa allows a few things:

1. You can run on Class A by flicking a switch. Class A only uses two tubes and pushes them hard all the time. Thus, you wear out the tubes faster, but you get a great crunch tone at lower volumes (about 15 watts I think).

2. You can run in Simul-Class, which allows you to combine both el34's and 6l6's at the same time. You get to hear the sonic characteristics of both tubes combined, instead of only 6l6.

3. You can put all 6l6 and get a fat bottom with sweet highs.

 

[dancullinane]

I actually prefer the 60/100 to my simulclass. I have a IIB simul and a 60/100 and I like the clean on the 60/100 better. I just can't dial out the grit on the simulclass for my clean tone. I think it does add more gain so it might be better for heavier stuff and on the clean channel it is nice for a dirty blues tyupe of tone but it just can't give me the clean "gimme shelter" /Stones tone I like with the band. The 60/100 just sounds more punchy/clean. The leads are good on both, I done't notice alot of difference on the lead channel

Thats my 2 cents

DC

 

[AdmiralB]

1. You can run on Class A by flicking a switch. Class A only uses two tubes and pushes them hard all the time. Thus, you wear out the tubes faster, but you get a great crunch tone at lower volumes (about 15 watts I think).

That's what Randall wants us to believe. They don't run anywhere near class A. They run in triode mode, which cuts the power roughly in half (and add a midrange tone emphasis, to my ears). If you use 6L6s in those sockets, they do run hotter than usual but not approaching class A (class A is impossible at those voltages). If you use EL34s, they run cold, like any other Mesa.

If you run only two tubes, you also have an impedance mismatch, which further cuts the power, so the 15W number is probably pretty accurate.

 

[Elpelotero]

another thing I've noticed is that a straight up 60 watter C+ has much more of a "raw" in your face tone as opposed to a Simul-Class, which I find to sound smoother.

 

[Platypus]

**** it I want a C+ badly :?

 

[macstrat]

Thanks for the info. A really clean channel with lots of headroom is important for me for snappy country style licks and funk, so maybe I shouldn't discount the non-Simul-Class amps. Hmmm...

 

[Boogiebabies]

1. You can run on Class A by flicking a switch. Class A only uses two tubes and pushes them hard all the time. Thus, you wear out the tubes faster, but you get a great crunch tone at lower volumes (about 15 watts I think).

That's what Randall wants us to believe. They don't run anywhere near class A. They run in triode mode, which cuts the power roughly in half (and add a midrange tone emphasis, to my ears). If you use 6L6s in those sockets, they do run hotter than usual but not approaching class A (class A is impossible at those voltages). If you use EL34s, they run cold, like any other Mesa.

If you run only two tubes, you also have an impedance mismatch, which further cuts the power, so the 15W number is probably pretty accurate.

True, but the SC OT has dual primaries which have two different impedence readings. The primary for the outer pair is not effected using EL34's as per se a speaker mismatch. It has much more of an audible mismatch when using 6L6's, inhrently giving it a fatter tone. Running the outer sockets in triode does offset the typical high mid sizzle of a high gain 6L6. Using EL34's offsets the highs in a slightly different frequency and tames the high amount of bass when using four 6L6's in the 60/100 output section. Slaving a Simul out to a 2:100 power amp, or a Recto will allow those to hear the difference. I feel the opposite would suffice for 60/100 owners slaving into a 2:95. From experience, the Simul's are smoother and have a less over the top nature in relation to the agressive 60/100's. Which one sounds better is up to you, but in the Boogie tradition an option will usually drive the price up.

 

[AdmiralB]

They're not dual primaries, they're ultralinear OTs. And they wire them up 'backwards'...EL34s have slightly lower impedances relative to 6L6s, so you would expect them to sit on the UL taps...but they don't, they put them at the full windings.

EXCEPT for the Series 300 amps...for some reason, on those the EL34 sockets are on the UL windings.

 

[AdmiralB]

First of all, Vox amps aren't class A. Very very few amps are truly class A.

Any single ended amp is 99% likely to be (Vibro Champs are an exception, they slide into AB at high volumes), but you can't get EL34s or 6L6s into class A at much over about 275V.

The only Mesa amps that do single-ended are the new ones with the 5W option - Lone Star Special, Express - they turn off the signal drive to one side of the OT. I would still wager that they go into AB at high volumes - again, the voltages are just too high.

 

[AdmiralB]

Yeah, false advertising, although Mesa is hardly the only company that's calling something "class A" that is not.

You will find that Randall Smith is not thought of in a very positive light in technical circles, mainly because he claims to invent - and then patents - things that have been around for a long time.

I like a lot of Mesa amps, and there are some I don't like. I think as far as service to the owner goes, they're a great company. But that doesn't mean that all their marketing hype is truth.

Simulclass as originally conceived - two different tube types, one operating in triode mode - is pretty cool, and the fact that they called it "class A" when it is nothing of the sort doesn't take away any coolness, IMO. But it does make me take most anything they claim with a largish grain of salt.

 

[JOEY B.]

True, but the SC OT has dual primaries which have two different impedence readings. The primary for the outer pair is not effected using EL34's as per se a speaker mismatch. It has much more of an audible mismatch when using 6L6's, inhrently giving it a fatter tone. Running the outer sockets in triode does offset the typical high mid sizzle of a high gain 6L6. Using EL34's offsets the highs in a slightly different frequency and tames the high amount of bass when using four 6L6's in the 60/100 output section. Slaving a Simul out to a 2:100 power amp, or a Recto will allow those to hear the difference. I feel the opposite would suffice for 60/100 owners slaving into a 2:95. From experience, the Simul's are smoother and have a less over the top nature in relation to the agressive 60/100's. Which one sounds better is up to you, but in the Boogie tradition an option will usually drive the price up.

So very well put, Ed. For me the Simul-Class is all about the upper mids. They tend to help round out the tone. The 100 watt C+ models can get a bit unruly in volume when trying to dial in the lead channel. The clean sounds are not as much of an issue. My 60/100 MkI sounds better as the volume and heat increases, and this is why it has been used as a slave amp as of late. Medical science has yet to produce an artificial ear to my liking .

 

[AdmiralB]

For me the Simul-Class is all about the upper mids.

That's a hallmark of triode operation. If you set a 100W Marshall up in triode mode, it's almost "Boston in a box". Cool, but not the tone I'd want all the time.

 

[JOEY B.]

For me the Simul-Class is all about the upper mids.

That's a hallmark of triode operation. If you set a 100W Marshall up in triode mode, it's almost "Boston in a box". Cool, but not the tone I'd want all the time.

If one wants the punchy, aggressive sound , I will agree the 60/100 delivers with authority. A Fulltone Fulldrive 2 (on clean boost mode) combined with a "Ayan Smooth-n-Slim" filter thru my MkI will turn the headroom monster loose. This same amp set up clean will bite HARD. It just all depends on what tone you're after.

 

[jvk]

What makes simulclass special (like BB said) is really how the tonal characteristics combine and that's why I like the idea behind it. I'm not sure I care so much about the true class the el34s are running though, it's been discussed to death on the interweb

I definetely hear the blurry/smooth quality that simulclass brings. 60/100 does rip but it sounds just too... raw.

 

[AdmiralB]

you must demonstrate/proove before you get the patent...

That's not how the process works.

You make a claim, and there is a period of time given for the world to comment. If no one comments, the patent is granted.

The concept of running audio tubes in different classes, in parallel, can be found in texts as early as 1950.

Mesa has a patent on the 5W single-ended switching in the LSS andExpress...Kevin O'Connor describes the concept in his Ultimate Tone books, at least seven years ago.

They patented the overdrive circuit in the Mark IIs...despite the fact that it's identical to that in the Dumble ODS.

Patents are overturned frequently. The fact that Randall's patents stand (not all of them are...questionable, for sure) means that nobody really cares enough to spend the money to challenge them.

The Fender Prosonic technically violated Randall's patent on switchable rectifier types. I suspect that Randall left them alone becuase they can afford a lot more legal fees than he can.

 

[Boogiebabies]

They're not dual primaries, they're ultralinear OTs. And they wire them up 'backwards'...EL34s have slightly lower impedances relative to 6L6s, so you would expect them to sit on the UL taps...but they don't, they put them at the full windings.

EXCEPT for the Series 300 amps...for some reason, on those the EL34 sockets are on the UL windings.

?

 

[macstrat]

I second that : it IS interesting, and mind-bending too.

 

[JOEY B.]

All technical jargon aside, (no offense) it is possible to tame down a 180 watt C+ Coliseum to sound very much like a Simul C+ (outfitted with the clean channel brightness mod). The Coliseum needed a boost in the mids and a cut in the highs on the front panel knobs (both of the "Pull Bright" knobs pushed in), a switch to half power (triode), as well as a wild EQ 2200Hz move (for the lead channel only). This made for more of the guitars' natural thick sound to ring through, rather that just the preamp fizz (on the lead channel). The mid boost and high cut also helped to warm up the cleans, which had way to much "bite" before the adjustments .