Roots Of The Recto?

[3124+]

Bassman -> Marshall -> SLO -> Recto.

There is a bit more to it then that, if Randall did not do cascading gain the SLO would have not been, so technically you have to put the Mark series between the Marshall and the SLO

No, the Mark Series gain architecture follows a different evolutionary path. It's based on Fender blackface circuitry and did not influence the Soldano/Recto design.

 

[screamingdaisy]

Bassman -> Marshall -> SLO -> Recto.

There is a bit more to it then that, if Randall did not do cascading gain the SLO would have not been, so technically you have to put the Mark series between the Marshall and the SLO

No, the Mark Series gain architecture follows a different evolutionary path. It's based on Fender blackface circuitry and did not influence the Soldano/Recto design.

According to Mike Soldano the Mark II influenced the SLO.

 

[siggy14]

Correct, here is a bit more on the topic of the SLO.

Michael Soldano originally worked with his head technician Bill Sundt at Stars Guitars (San Francisco, CA), modifying amps brought to him. He had built his first amp, a Fender Bassman clone, with the aid of books being discarded by a library. Michael worked on modifying his version of the Bassman for years, until he bought a Mesa/Boogie Mark II and began modifying this amp. The first three SLO amps were based upon this amp and the first one was sold to a female friend. The second one was sold to Howard Leese from the band Heart.

 

[3124+]

I'm looking at the schematics right now. The SLO/Recto preamp structure has absolutely nothing in common with a Mark II. The Mark II circuit did not influence the SLO/Recto design in any way. Michael Soldano must have gutted that Mark II right down to the bare chassis and wired his circuit in there from scratch.

 

[screamingdaisy]

I'm looking at the schematics right now. The SLO/Recto preamp structure has absolutely nothing in common with a Mark II. The Mark II circuit did not influence the SLO/Recto design in any way. Michael Soldano must have gutted that Mark II right down to the bare chassis and wired his circuit in there from scratch.

I'm not entirely sure the paragraph posted by siggy14 is entirely accurate as I've seen the same story worded different ways. In the version I'm familiar with the SLO wasn't a modified Mark II, but he used the knowledge he learned from modding/studying the Mark II when developing the SLO.

What he wanted was to get rid of pedals as he felt all the distortion should come from the amp itself, and at the time (early 80s) the Mark II was the highest gain amp on the market. After he got it he liked it but felt it had certain shortcomings (such as the shared tone controls and the position of the tone stack in the preamp). Whether he modded the actual Mark II or copied parts of the Mark II into his test bed I'm not sure of, but he eventually used what he learned to start modding Marshalls, and the knowledge he gained from modding eventually developed into the SLO.

 

[3124+]

If anything he used the Mark II as an example of what not to do.

 

[screamingdaisy]

Either way, you can either Google old interviews or search YouTube and get it straight from the horses mouth and decide for yourself.

 

[afu]

Jesus H. CHRIST!! If you're looking at the schematics, you can no doubt see there ARE differences between a DR and a SLO. I didn't start the discussion to have an old argument and the people ignoring that can go take a flying F. There are a number of differences, even if the preamps are similar. Does a Fender sound like a Marshall? They're pretty **** similar, but the design choices make them sound different.

First of all, the ferrite bead exhibits resistance and impedance. It creates a very small potential divider, but passes more than 99% of the input along. The resistance, in series with the grid resistance, attenuates radio frequencies without bringing the presence down when the grid interacts with the 12ax7's internal capacitance. It's fairly hi-fi for a guitar amp.

Then, the load to stage 1 is 2M2 with the grid resistor moved to after the load. This keeps the response rock solid and gives a slight boost to the low frequencies. The RC network also makes the grid resistor about 510k, creating a potential divider with whatever value your particular version of the Recto has as a gain pot. The Raw (or Blues) setting is even more different than a SLO for obvious reasons.

The LDRs or 100 ohm resistors not only change the cutoff for low frequencies, but interact with the cathode resistors to change the bias. There are three of them and it shifts the bias to make saturation more difficult. Stage 3 is the only completely unchanged part of the dirt channels, because it's biased into instant saturation and produces 2nd harmonics with very little effort. It is the heart of a "modern" high gain kind of amp.

The passive RC network off of the treble wiper works differently by mode, but lets use Vintage mode as a comparison to a SLO. The ground is placed between that network and lug 3 of the presence pot. They don't interact, because voltage takes the path of least resistance, but the RC network sets a permanent low pass filter that the SLO doesn't have, producing a darker sound. The Modern mode is completely different than a SLO, just by disconnecting the NFB and having that RC network (Vox-y).

Then, the DR loop is buffered to reduce input impedance and has less insertion loss. The SLO loop is primitive.

So, 1 mode out of 4 or 6 is very similar to a SLO throughout the preamp and people want to ***** about it, even though it's been refined by Mesa to sound very different. Whatever. By the time the output transformer smashes the speakers, the power amp has again changed the sound and that point is moot.

The intent of the discussion was about why they made those decisions and what kind of speculation a person might have as to the direction they took this design. They modified it enough to make it theirs and then added a whole slew of features that Soldano didn't even think about and that's what piqued my curiosity.

 

[siggy14]

I'm looking at the schematics right now. The SLO/Recto preamp structure has absolutely nothing in common with a Mark II. The Mark II circuit did not influence the SLO/Recto design in any way. Michael Soldano must have gutted that Mark II right down to the bare chassis and wired his circuit in there from scratch.

I'm not entirely sure the paragraph posted by siggy14 is entirely accurate as I've seen the same story worded different ways. In the version I'm familiar with the SLO wasn't a modified Mark II, but he used the knowledge he learned from modding/studying the Mark II when developing the SLO.

What he wanted was to get rid of pedals as he felt all the distortion should come from the amp itself, and at the time (early 80s) the Mark II was the highest gain amp on the market. After he got it he liked it but felt it had certain shortcomings (such as the shared tone controls and the position of the tone stack in the preamp). Whether he modded the actual Mark II or copied parts of the Mark II into his test bed I'm not sure of, but he eventually used what he learned to start modding Marshalls, and the knowledge he gained from modding eventually developed into the SLO.

I took it from Wiki but at the same time I have seen it posted in other forums as well. Either way any amp that uses cascading gain is based off Randall Smith design so yes the SLO is based off a boogie as much as the recto is based off the SLO. Take that statement how you want but AFU as basically said it best, there is enough changes that they are not the same but the recto was inspired by the slo just like the slo was inspired by the cascading gain that Randall Smith introduced to the world. Why dont we leave it at that and get this thread back on track.

 

[3124+]

Cascading gain was around long before Randall Smith's amps. In fact, every tube guitar amp in existence uses some form of cascaded triode staging. Even a Fender Champ uses two triodes in series. A single gain stage into a long tail phase inverter is technically cascaded gain staging. Randall's design utilized multiple preamp volume pots to control the signal between stages. He used relatively large (25uf) cathode bypass caps, and a plate driven tone stack like a Fender blackface.

The SLO preamp was not inspired by any of Randall Smith designs. Totally different approach. The SLO uses a cold clipper stage (39K cathode resistor) similar to the 10K cold clipper in a Marshall MKII Master Lead head. The cathode bypass caps are relatively small (1uf) and the tone stack is driven by a cathode follower at the end of the preamp chain again like a Marshall.

 

[OryCheyne]

I get it, just carrying on for fun. Sometimes I like to do that with my kids. Bit of fun is ok so long as everyone knows the rules. My turn.
What I can't believe is that every one in the business of amping guitars through a vacuum chooses to use 6L6's, 34's, 84's, 12A**'s, and why would they put these on PCBs, that's not their idea, wow, they even all use copper wire and tinned solder. OMG they are all so unoriginal. They should all go and hang their heads in shame!
How about you go plug in turn up and don't stop till you feel better.

Sorry, about adding to the dribble. I like the topic of the OP.
Friend of mine advised me recently to get a rec, i can say I have never plugged into one, but plan to sometime soon. Agree they do have an iconic sound. I suppose RD for fun stuff like designing guitar amps probably involves a bit of experimentation. Not like its going to kill someone if you get it wrong.
I have made plenty of circuit boards, none for fun stuff, none using valves sadly. It wouldn't be hard to go through countless iterations to get something unique sounding, then, further to control, that includes scratching or bridging tracks.
Interesting concept free one to fore plus! I guess sometimes people don't need an original thought to think! Other times they do! Now go plug in an play.

 

[afu]

In my rant I said the RC network in Vintage doesn't interact. It does, but not the same way as the Modern. I just wanted to correct that, but I'm too tired to go into detail. Also, I was ill and grumpy. I'm usually more reasonable, but the discussion is meant to talk about the ideas behind Mesa interpretation of a Bassman-to-JCM inspired, "modern", high gain amp. Saying they ripped off the SLO is simplifying it, especially by the time you get into the later revisions and then the 3 Channel.

I've been pouring over power amp schematics and I haven't found anything that is exactly the same, since this particular fixed bias arrangement is so different than most amps. Early 80s-Marshalls are close and some things are merely common to almost all class AB amps from that general period, but some of the details are unique to Mesa.

 

[screamingdaisy]

I'd be curious to know what you puzzle out or anything you find interesting. Like I said before, you're approaching the Recto from a different angle than anyone else I've see on this forum over the years. It would be nice to learn something new about it.

 

[Third Age Amps]

Funny how this topic is a quick divider ... After the smoke clears none of us, myself included, (aside from those that have worked at MB from the beginning) really knows for certain what these guys were/are thinking. The only thing we can really know is that the SLO was first designed in 1987, and a lot of subsequent amps borrowed from that topology. And in truth, they improved upon that simple design greatly.

Maybe Michael Soldano, Lee Jackson, Randall Smith, and the other high-gain Gurus simply had moments of clarity around the same time based on the changing musical needs, or maybe people flat-out ripped off designs. We'll likely never know the whole story but in the end, we all get to reap the benefits. I should really work on my ranting because in reality, it doesn't matter!

Let's all go drink a nice stout and agree that we love these amps no matter who did what. As far as the ranting goes - I'm trying Ringo, I'm trying real hard ...

 

[afu]

The words of Steven Johnson:

“This is how great intellectual breakthroughs usually happen in practice. It is rarely the isolated genius having a eureka moment alone in the lab. Nor is it merely a question of building on precedent, of standing on the shoulders of giants, in Newton's famous phrase. Great breakthroughs are closer to what happens in a flood plain: a dozen separate tributaries converge, and the rising waters lift the genius high enough that he or she can see around the conceptual obstructions of the age.”

“Old ideas can sometimes use new buildings. New ideas must use old buildings.”

“We have a natural tendency to romanticize breakthrough innovations, imagining momentous ideas transcending their surroundings, a gifted mind somehow seeing over the detritus of old ideas and ossified tradition. But ideas are works of bricolage; they’re built out of that detritus.”

“Innovations usually begin life with an attempt to solve a specific problem, but once they get into circulation, they end up triggering other changes that would have been extremely difficult to predict.”

The point is that innovating on an established technology requires taking old ideas and fusing it with new ideas to create something that is either better or new. The cold biased stage (stage 3) goes back to at least the JCM 800. Soldano took it, murdered that stage into instant distortion (pure awesomeness), borrowed the idea for channel switching from the Mark series, and had a breakthrough with the SLO. Mesa took the SLO preamp and changed it a bit, married it to a completely different power amp, buffered the fx loop, added voicing options, transformer tapping for spongy, rectification options, a brilliant switching system, impressive power filtering, and threw in Vox's ideas for using no negative feedback.

Ideas are never in a vacuum. They need a point of reference to ground them to reality. That Mesa used ideas from several sources, aside from themselves, is not a bad thing. It's necessary to get the ball rolling. If they pulled a Bugera and copied the SLO to a "T", I wouldn't support them, because that is what a rip-off is.

 

[user 21540]

It states on the Soldano Wikipedia page that Mike Soldano based his SLO design on a Mesa Mk II. I guess it's a bit like the blues -- everyone borrows from each other:

https://en.wikipedia.org/wiki/Soldano_Custom_Amplification

 

[3124+]

It states on the Soldano Wikipedia page that Mike Soldano based his SLO design on a Mesa Mk II. I guess it's a bit like the blues -- everyone borrows from each other:

https://en.wikipedia.org/wiki/Soldano_Custom_Amplification

Not accurate. The SLO circuit does not resemble the Mesa Mark II. The SLO is more like a Marshall MKII.

 

[screamingdaisy]

Not accurate. The SLO circuit does not resemble the Mesa Mark II. The SLO is more like a Marshall MKII.

I thought we already covered this...

 

[3124+]

Not accurate. The SLO circuit does not resemble the Mesa Mark II. The SLO is more like a Marshall MKII.

I thought we already covered this...

Yeah we did, the SLO is not based on the Mesa Mark II.

 

[user 21540]

Not accurate. The SLO circuit does not resemble the Mesa Mark II. The SLO is more like a Marshall MKII.

I thought we already covered this...

Yeah we did, the SLO is not based on the Mesa Mark II.

Someone should modify that wiki entry then.