Recto Mods

[afu]

A couple of notes with information for everyone:

1) I was reading about negative feedback, PI operation, and power tubes a bit over the weekend to brush up. Some user applicable things came to light in regards to the modes of a Rectifier. A push-pull class AB amp cancels out the second harmonic, due to the relationship of the phase of each half of the signal being split. It happens in the PI and in the power tubes. Canceling out the second harmonic gives the 3rd harmonic room to be heard clearly.

In the Rectos, each mode affects this differently. Negative feedback stabilizes a power amp by reducing gain and harmonic distortion in the power section and it flattens response. Modern has no NFB, so it has the most 3rd harmonic. Vintage has variable NFB with the Presence control, so the distorting 3rd harmonic can be spanked and set down on the naughty chair at the lowest Presence settings. Raw has the most NFB and basically hits the 3rd over the head with a club and buries it. From this perspective, Raw has the cleanest power amp performance of all the dirt modes.

But don't make NFB the core decision maker for your Presence settings. All class AB amps produce more 3rd H and the Rectos actually have relatively clean power amps, even in Modern. The preamp determines most of the distortion level and it produces a ton of 2nd H. That leaves its mark.

2) I looked at a schematic for the Stiletto. It has the ability to to reduce the gain of the first stage and remove the cold clipping stage when set to "Crunch". This contributes to a sort of Plexi voicing. The voicing options for the other modes do a lot of things which I had been thinking about. It might benefit a person who isn't in love with a stock Recto to check out the Stiletto, especially if they are coming over from Marshalls.

 

[JCDenton6]

Awesome, keep up the stellar work here!

 

[afu]

Awhile back, I turned off the loop and set the channels. I then turned the loop back on, turned Output to Noon and turned the Send up until the volume was pretty close to the "bypass" sound (between 2 and 3 o'clock). I used Solo to complete the volume difference and to change the bottom. I really like the difference from my normal settings.

Usually, I'd turn all the channel volumes up in response to the loss when the loop is engaged, but I always heard a difference in the tone of the amp. Keeping the volumes lower and making the Send stronger changed it. I'm not sure if the difference was the sound of the loop overdriving or PI response, but it's tamed. I feel like I'm getting the best sounds since I bought it.

Awesome, keep up the stellar work here!

Thanks.

 

[afu]

https://warpedmusician.wordpress.com/2015/11/25/channels-2-and-3-part-1-mesa-rectifier-design-concepts

Channels 2 and 3 design concepts pt 1.

 

[afu]

I'm discontinuing discussions about modifications on my blog. I can't test them for a couple of reasons, mainly because of my health, but also because I keep finding different ways to modify the sound just by using the Solo and FX Send for tone shaping. Also, the power amp is such a huge factor that preamp changes will only get a person so far. If a person is dissatisfied or bored, slaving out to another power amp might be the cure for what is ailing them.

I do have an idea though: I think it would be cool to have a Recto with the voicing options independent of each other. The mode names mostly refer to the power amp's negative feedback options. However, Raw actually does have less bass response through its preamp voicing and it would be cool to use it with the power amp options of Modern or Vintage. Throw in a switch to enable/disable the cold clipping stage and it would be quite a versatile amplifier. I also wouldn't mind a way to defeat the treble roll off in Vintage that gets left behind from the Modern presence circuit. The Vintage Presence control would then actually make a much greater difference on the sound.

That said, most of these things are possible with a second amplifier and slaving. So, like, if Screaming Daisy were to have two Roadsters, he could play around with the modes to get different responses. A person with a Recto and a Stiletto could do all of those things by slaving the Stiletto into the Recto (except the treble roll off being defeated). There is also the advantage of allowing EL34 and 6L6 being used simultaneously with one preamp by using the effects loops for the connection instead of the Slave Out.

Also, little lunchbox amps can be used to get a good sound at reasonable volumes if they have an effects loop. That would solve the problems people can have trying to play a Recto at home. The TA and Mark series come to mind as options from Mesa which would also offer a different sound on their own than buying a Mini Rec/'Verb 25. Other options from Peavey and H&K exist with loops and DI boxes. Lots of options......

 

[afu]

https://warpedmusician.wordpress.com/2015/11/29/dual-rectifier-classic-rock-2

I know I over-think things sometimes, but study of the circuit has given me some insight to the way everything interacts. The above is an example of settings I've been using for 60s and early 70s Classic Rock. It utilizes all the circuit info I've uncovered. If someone tries it out, let me know if you get similar results.

 

[screamingdaisy]

I also wouldn't mind a way to defeat the treble roll off in Vintage that gets left behind from the Modern presence circuit. The Vintage Presence control would then actually make a much greater difference on the sound.

This is the way channel cloning on the two channel worked when set to Red cloned Orange (channel 2 on vintage). The channel 1 presence control would control the negative feedback on channel 2, and the channel 2 presence acted as a secondary treble control.

Red cloned Orange is my favourite setting on the old 2 channel. It was brighter and more aggressive than the actual orange channel.

(FWIW, vintage on all the newer heads I've heard sounds more like the brighter and more aggressive red cloned orange and not like the original, much darker orange channel)

 

[screamingdaisy]

https://warpedmusician.wordpress.com/2015/11/29/dual-rectifier-classic-rock-2

I know I over-think things sometimes, but study of the circuit has given me some insight to the way everything interacts. The above is an example of settings I've been using for 60s and early 70s Classic Rock. It utilizes all the circuit info I've uncovered. If someone tries it out, let me know if you get similar results.

Your Raw settings were are pretty similar to mine, except I run the treble and presence lower (12:00). I'm also using a brighter, PAF style pickups (Burstbucker 1 & 2) and my Recto 2x12 produces more top end than the Recto 4x12, so I'm not sure how much either would factor into things.

What I did a couple days ago is took your comments about how the Raw channel was somewhat Plexi-ish and decided to push it like one. I brought the gain up and set it at the edge of where it saturates (which for me is about 2:30), so when I dig in a little it sizzles and if I back off a bit it's overdriven. If I back off the guitar's volume a bit I can use my pick attack to shift between clean and overdrive, and if I hit it with a boost (Mesa Tone Burst) I have more saturation.

The other thing I did was start experimenting with the manual's suggested settings again. I used to think that the suggestions with the mids super low were a joke, or meant to pacify the Metal Zone crowd, but I thought your comments on the EQ having two midrange knobs was intriguing so I decided to experiment with them. Basically, I set the mids on Vintage and Raw to zero and left it there for a couple days so that my mind would get used to the sound. Then, instead of compensating for the hollow, scooped sound by adding midrange I started cutting bass and presence to bring it back into balance. Then I'd periodically sweep the treble knob to set the overall voice of the amp (I seem to prefer it just a hair above 12:00).

At the moment raw is still sitting with it's mids on zero and vintage is mids at 9:00, but I'm not done tweaking. As it is I've managed a really good transition from raw to vintage in that they have the same relative feel and tonality, with vintage having a bit more gain, midrange and top end for playing lead. And, as a consequence of running the mids lower the overall feel is more compressed, which helps make playing lead a little more enjoyable vs the stiff, boxy sound I had previously with the mids up around 11:30.

In the past I'd periodically see a picture that showed a major touring guitarist with his mids low and/or bass high and I'd wonder how he was getting away with those settings, particularly when the guy was known for having good a live sound. Now I think I understand a little bit better.

On a different note, I've tried fiddling with the FX loop send levels and seem to like it around 1:00-1:30. I tried going higher and the sound started to loose clarity, and I tried going below 12:00 and the sound just got thinner and weaker.

Lastly, I've noticed in a few spots where you state that channel 2 has more presence than channel 3, so the modes on channel 3 need much higher presence settings than channel 2. My Roadster is the opposite: I need the presence on channel 4 to be above about 4:00 before it's even noticeable on raw or vintage modes. I thought the standard for Rectos (prior to the Multi-Watt) was the Orange channel is optimized for Raw/Vintage and the Red channel is optimized for Modern, but yours seems to be opposite (or, maybe I've understood things incorrectly).

 

[afu]

No, 3 has more presence and it's set higher. You're right about that. I did write about Modern 3 having more mids than 2. At 9:00, the Modern middle is the same as Vintage or Raw at 12:00. I use my Mids in a similar fashion, right now, as what you described and I'm in love with Raw mode for its versatility.

The Mids suggestion from the manual works when the Bass is kept at bay, just like you're saying. I think the higher suggested Mid settings work well when pushing all the controls or, at least, when the bass is set to "kill".

With the Send, I had similar problems at first. I ended up setting a sound with Channel 2 with the loop bypassed and then turned it on. After the volume dropped, I adjusted it without touching the Channel Volume and relied on the Send to bring it back up with Output on 12:00. It sounded more like "bypass" that way.

 

[afu]

https://warpedmusician.wordpress.co...-and-3-part-2-mesa-rectifier-design-concepts/

Been working on this for a few days to make sure I was not blabbing and so it covered a lot of complex interactions, but didn't read like deciphering the hieroglyphs with a Spanish For Dummies book. Also, I'm not well and it's hard to thunk when my thinker is on the fritz.

This covers V2. The cold clipping stage is included in this and I explain more about the way it creates the asymmetrical distortion, that effect on the harmonics, and just possibly why some people don't like Rectos for soloing. That part is definitely not nerded up too much. Scroll down to the middle of the page and look for the underscored sentence fragment if interested.

Some information relating to mods are there too.

Let me know if something is really weird, because I'm beat and my proofreading might be off. I was going to cover V3, but 1400+ words is enough for one blog post.

(12/2/15) I edited it slightly to clear up some points being made, but the information is basically the same.
(12/4/15) I edited it heavily to flow from one idea to the other more easily. What kind of crack was I smoking?

 

[afu]

It occurred to me that putting a drive stage and EQ together in the loop of a 3 Channel Recto set to Ch1 is a heck of a lot like a Mark Series amp. It'd be Tube - EQ - Volume- Tube - Tube - Volume - Drive - EQ - Volume. It won't sound the same, but...... lol

 

[afu]

While editing the final section of my look at the preamp, I realized I miscalculated the 2nd harmonic produced by V2b. I stated 46% when it reaches its limit. It's actually 90%. The grid headroom is 4.75 volts which can be easily achieved.

For example, a decent humbucker might output 500 mV for a note. With Gain at Noon, 39 volts is entering V2b, but the grid can't allow more than 4.5 volts. It would be clipping immediately and then less so as it decays. Now, make it an EMG 81 and the input voltage is about 78 volts. Still has the maximum of 90% and retains for a longer period. Whether that is desirable is up to the player.

 

[screamingdaisy]

Rectos do love the EMG 81.

It's like being punched by a giant fist... a giant fist gripping a sledgehammer... punching holes in your face.

 

[afu]

Rectos do love the EMG 81.

It's like being punched by a giant fist... a giant fist gripping a sledgehammer... punching holes in your face.

This! Using active pickups is about the same as using a boost with a PAF. Incredibly, the Het Set has twice the output of the 81 and it slams my amp like it's visiting Shanghai.

 

[afu]

https://warpedmusician.wordpress.co...-and-3-part-3-mesa-rectifier-design-concepts/

Channels 2 and 3 Part 3.

 

[barryswanson]

Rectos do love the EMG 81.

It's like being punched by a giant fist... a giant fist gripping a sledgehammer... punching holes in your face.

This! Using active pickups is about the same as using a boost with a PAF. Incredibly, the Het Set has twice the output of the 81 and it slams my amp like it's visiting Shanghai.

I'm a huge fan and long time user of the Het Set, they are very very good pick ups. I currently have a set of Fishman Modern Fluences sitting under the Christmas tree with my name on it. So after 25th I will swap the Het Set out of my ESP eclipse to give them a try. Apparently even hotter in Active mode. I'm fortunate enough to be on speaking terms Will Adler from Lamb of God and he recently changed all his guitars over to them and reckons they are just incredible with his Mark IV's

 

[afu]

Rectos do love the EMG 81.

It's like being punched by a giant fist... a giant fist gripping a sledgehammer... punching holes in your face.

This! Using active pickups is about the same as using a boost with a PAF. Incredibly, the Het Set has twice the output of the 81 and it slams my amp like it's visiting Shanghai.

I'm a huge fan and long time user of the Het Set, they are very very good pick ups. I currently have a set of Fishman Modern Fluences sitting under the Christmas tree with my name on it. So after 25th I will swap the Het Set out of my ESP eclipse to give them a try. Apparently even hotter in Active mode. I'm fortunate enough to be on speaking terms Will Adler from Lamb of God and he recently changed all his guitars over to them and reckons they are just incredible with his Mark IV's

Sweet! On all counts. Let me know how those Fishman pickups work. They look cool and the description was intriguing.

It's funny, I'm heading in the opposite direction. After years of trying to be brootal, I'm getting more into Bluesy, Classic Rock/Stoner sounds. I'm going to keep one guitar with a Het Set for when I need that, but my circumstances are sending me to slower playing.

I was thinking about it over the last few days: Rectos were designed back before vintage gear totally took off into the stratosphere as a trend. While there have been revisions to the Recto, I speculate that the design was expecting overwound passive pickups or actives, since it was going to be marketed to (Thrash) Metal and Hard Rock bands. The early cleans weren't awesome, so it wasn't meant to be a Country amp.

When I use JB, Blackouts, or EMG 81 or the Hets, a boost in front seems redundant. Using medium or vintage output pickups would require a boost to get to the threshold the amp was designed for, if my guess is correct. When I used a Tele with it, I was underwhelmed. I later destroyed that Tele, but that was for a different reason.

 

[screamingdaisy]

Doug West has written in various places that users will get better results with overwound pickups, and the Anderson that he uses is loaded with an H3 in the bridge, which is a high output ceramic pickup. Since that's one of the guitars that he uses when they're voicing an amp, there's a pretty good chance that a super Strat with an H3 will sound good.

That said, I've noticed Mesa mixes it up pretty good with their demo videos... P90s, Tele, Strat, Semi-Hollow w/ Humbukers (possibly w/ PAF?), PRS (possibly w/ HFS?), Gretch w/ Filtertrons, etc.

For myself, I've been using P90s and PAF for the last 9 years. PAF (mine all have Alnico 2) struggle a little with aggressive rhythm due to the spongy attack, but man are they ever sweet for lead.

Personally, I've never been into boosting a Recto for rhythm. If that's the sound that's required I'd rather use EMGs.

 

[afu]

I did not know that about Doug West. Thanks for the info.

I have modded the circuitry around my JB to make a big offset between the coils. It's almost like a Duncan Custom 5, now, but the bass is still low. It did drop the output to be like the semi-hot, overwound PAFs. I had to cut the mids before the modding. Now, it's more lenient for settings.

My next bridge pickup will be either a Custom 5 or a 59/Custom Hybrid. I'm hoping to get a LTD EC-1000 Amberburst with a JB/59 set and my current guitar will get a pup change. I have fallen in love with the ESP style thin U and tall frets.

I was trying out boosting for rhythm with different pedals (EQ, overdrive, light distortion, fuzz turned down). I can see the value in it, but it doesn't work for a lot of what I'm doing. My bass frequencies ended up sounding like they were ripping bedsheets at unity volume.

I do have to say that for $20 that Fab overdrive is a cool little pedal. It sounds really nice as an overdrive; On Clean and my Harmony amp, it was great. On Raw it was awesome for leads and a pushed Classic Rock sound. It was less useful on the high gain modes. Not enough control over the frequencies on its own and I don't have a pedal switcher to pair it with other pedals effectively as a spice.

I pushed a couple of fuzz pedals with it and it was awesome. One is old school, loading the previous source, and it was grungy. The buffered fuzz was like the slasher film of guitar playing.

 

[afu]

I've been thinking about rewiring my guitar for a long time. Screamingdaisy's current conversation in the other topic had me thinking about what I want to do and I wanted to share it in case it's helpful to anyone.

This morning, I started looking at part values. It occurred to me that instead of using a 250 k volume pot to darken the treble, I could use a 250 k tone pot and use a cap that makes it easy to tune the guitar's tone with the Recto. Using an audio taper for the pot will make fine-tuning the first half of the tone control easier. Since Rectos have cuts at 1.6 kHz and Modern's presence filter is 2.2 kHz, that's a general target zone for the tone pot.

Considering the way the parallel pots will reduce in value, a 250 k and 500 k will make each other act like 166.7 k pots. With a .047 uf cap, the filter cutoff at 9 would be about 2 kHz; Tone on 8 would be about 1 kHz. Actual value will vary in the real world.

It would make a darker tone overall and needs bright or midrange-focused pickups to work effectively (to not make mud). I'm switching to a series/parallel wiring for a Duncan JB. The resistance of the pickup won't change drastically like it does for a split coil. That makes the filters work well in either setting.