Tech-savy people: What is really the same on a Recto and an SLO?

Rex Rocker

Rex Rocker

Well-known member
We all know they sound radically different, but that the Recto is a blatant rippoff, apparently.

I've heard it's just the poweramp that's different, but I doubt that's the case. I do know the Recto poweramp is very unique, especially in Modern mode, right?

But the Recto has like a thousand other modes/sounds in it. Wonder what's the one sound that's based on an SLO. Vintage? Modern?

I'd be willing to bet the tonestack values are pretty different as well, but I don't really know. At least in Modern mode. Anyone care to elaborate?

Thank you!
 
EyesOfTheSouth! said:
Not much at all if you talk to a “real” tech/amp builder.
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The preamps are pretty close. The main difference is the power section and the NFB section. People want to overlook the importance of the power section, which I think is a huge portion of the tone and especially the feel. But yeah, if you strip away the nonsensical options of the recto, it's clearly based on the SLO.
 
scottosan said:
The preamps are pretty close. The main difference is the power section and the NFB section. People want to overlook the importance of the power section, which I think is a huge portion of the tone and especially the feel. But yeah, if you strip away the nonsensical options of the recto, it's clearly based on the SLO.
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Agreed. The power section and the transformer “is” the amp in most cases when played loud as designed. When it comes to those components, they aren’t close.
 
The early recto compared to a slo is nearly identical in terms of the preamp from best I can tell, and no way two different guys came to the exact same preamp configuration. The only real difference I could find was no input grid on v1 in the recto an an additional resistor on the cathode of v1.

So out of call it 21 components 1 was not included on the recto and 1 had an additional resistor, all else being basically identical. If you want to get nitpicky there we’re minute additions in terms caps the recto. Tonestacks are identical. Fair warning I didn’t study either super intently so I might be off.
 
The thing is what's the same is the preamp, but a Recto has several modes which all sound different. What preamp? I'm pretty sure the tone stack is different on Modern vs Vintage mode. And Pushed mode is what... an SLO's Crunch? And then Modern mode brings the Presence control into the preamp itself, no?

And I agree, the trannies are part of the SLO's magic. Mesa trannies are way undersized by comparison. But even if they're different, wouldn't that bring the Recto in the ballpark of the SLO, just sounding worse?
 
Look up the episode of Tone Talk with Mike Soldano. At one point a viewer asks this question, Soldano politely defers and then Dave Friedman chimes in and explains exactly what is the same and what Mesa changed. Rest of the episode is pretty cool as well, lots of great info.

Edit: Found it and queued it up for you - https://www.youtube.com/live/0N_UpOeYGVo?feature=share&t=8231
 
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The main difference is that Mesa put the tonestack where the effects loop is on a regular SLO and the effects loop in a Mesa recto is where the tonestack is in a SLO. The gain stages are similar but they are architecturally different which is why the tonestacks in rectos are so different in dialing them in. Essentially Mesa took a page out of fenders book in terms of early tonestacks for tone shaping. Fortin made a career out of resonance and presence controls early in the preamp and Bogner did something similar in the twin jet.

These amps are so touchy to design that small things make large tonal impacts which is why we say make small changes one at a time when tuning an amplifier.
 
I think it’s important to specify which Rectifier is so close to an SLO. My understanding is that it was in the first early revisions (somewhere between C to F?) of the two channel DR. Not the later Rev G that they sold a gazillion of, or the Tremoverb, or single rectifiers, or 3-channel versions that came even later.
 
retrorack said:
I think it’s important to specify which Rectifier is so close to an SLO. My understanding is that it was in the first early revisions (somewhere between C to F?) of the two channel DR. Not the later Rev G that they sold a gazillion of, or the Tremoverb, or single rectifiers, or 3-channel versions that came even later.
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My Rev C is very SLOish with its bouncy, liquid feel. It’s got a similarly thick and saturated gain structure, the C being tighter and more aggressive of course. The C also has a powerhouse of a power section that becomes a next level beast at volume, bloom and all. The C is the most similar to an SLO with every revision after that being less so imo
 
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Not really sure how much (or if) it affects the tone, but the SLO also never disengages the clean channel when the overdrive channel is engaged which doesn't happen on the Recto. There's been debate about how much this matters, however, considering the output of the overdrive channel likely overwhelms the clean channel signal when both are present.
 
Rex Rocker said:
Anyone?
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The question you are asking are not as simple as they seem there are many things that can change tones
From cap values to voltages and bias
The Modern mode removes the NFB completely but that is in the power amp
I believe the preamp mode was the orange and it was closest on the earlier Rectos , every rev changed it more
There is one key smoking gun and it’s the value of the cold clipper
Cold clippers are not unique Marshall have them but the SLO value that 39k resistor is such a random value that no one would just guess at that
 
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