If you were going to give amp designs a taxonomy, how would you do it?

[Nickerz]

Today was an interesting discussion that boiled down metal amp transformer styles into SLO, Marshall & Mesa(fender\marshall hybrid). Not specs obviously, which are infinite. Also discussion about negative feedback as a metric and tube bias (e.g. 5150).

[Xander8280]

One commonality to what constitutes a CS (cold gain stage, "cold clipping" stage, etc) is that there is no cathode bypass. So the gain stage is biased at a cold Q point but also there is heavy cathode degeneration. With the typical attenuation between stages these "CS" stages are not used for voltage gain, mostly just for their DC offset when clipping causing even order harmonics and duty cycle change as the note decays through a high gain preamp.

I really like the block diagram concept with giving the general topology of the preamp stages for the different amps.

This thread is super cool

[roberto]

One commonality to what constitutes a CS (cold gain stage, "cold clipping" stage, etc) is that there is no cathode bypass.

I'm sorry again, but it's not true. Think about VHT, Fryette, CAE/CAA, SIR and many more.

[Xander8280]

You're right Roberto

[Nickerz]

One commonality to what constitutes a CS (cold gain stage, "cold clipping" stage, etc) is that there is no cathode bypass. So the gain stage is biased at a cold Q point but also there is heavy cathode degeneration. With the typical attenuation between stages these "CS" stages are not used for voltage gain, mostly just for their DC offset when clipping causing even order harmonics and duty cycle change as the note decays through a high gain preamp.

I really like the block diagram concept with giving the general topology of the preamp stages for the different amps.

This thread is super cool

Which cold clipping amps don't have cathode bypass?

[Colossal]

Which cold clipping amps don't have cathode bypass?

To name a few...

JCM800
Trainwreck Express
Trainwreck Liverpool
Soldano SLO

You might include the Komet K50 in there with its 3k3 cool clipping stage

[Nickerz]

In the last 6 months I've learned, that at least for high gain metal, the technical taxonomy is less important at the preamp level.

So far I'm fairly satisfied with the explanation that once gain is high enough, amps can be categorized something like this.

• 1. Cathode cap
  2. Transformer style (Fender, Marshall, HiFi (Soldano, VHT), "Mesa" Marshall/Fender hybrid) with my doubts than any notable high gain amp is designed with a Fender style transformer.
  3. Transformer size (e.g. "big iron" amps)\Wattage design
  4. Amount of gain
  5. Power section tube choice

e.g. I am able to replicate a Mark IV fairly closely with a Fender cathode cap, Soldano preamp and HiFi transformer (though it lacks the liquidity darkness that it gains with the Mesa transformer style)

I am able to replicate an Orange amp fairly closely with a Fender cap, Marshall or Soldano preamp (vary only by gain amount) and HiFi or Marshall transformer.

I am able to replicate a Hiwatt fairly closely with a Soldano cathode cap and a low gain Marshall preamp with either Hifi or Marshall transformer style.

I am able to replicate a VH4 very closely with a Marshall style cathode cap with a hot rod marshall circuit and a Mesa transformer style.

The differences between an XTC circuit and for instance a Deliverence circuit become a lot more minor than I'd have thought. And so at this point, it becomes important to even be able to describe the differences in feel and playability and ultimately what those influences in the circuit may be.

e.g. In these two circuits, the differences are primarily the "woodiness" of the XTC vs the "hollow\dry" sound of the XTC. Both have similar levels of gain and low mid hump.

Basically I think we can actually deliniate something like this some more.

[sluckey]

Thankfully you haven't just been wasting your time.

[Nickerz]

After much contemplation, I've desided it's going to be important to deliniate preamp and tonestack. From a layperson's perspective, tonestack simply isn't given the importance it actually holds in design.

So in that regard, I think tonestack as a taxonomy warrants some discussion.

What's more important? The fact an amp is plate driven? Or that it's "british" in terms of it's voicing? They are almost equal in terms of their absolute imprint on the amp's tone.

e.g. The Silver Jubilee is obviously Marshall, and a 5153 el34 is kind of Marshall. But both are definatly plate driven in terms of sound and feel. So it would almost seem as though tonestack should be the primary taxonomy.

So something like this so far.

Platedriven>Wattage>Voicing>Preamp Description

So a Jubilee is a

Plate Driven 100w British saturated midgain amp w/ high mid placement.

We can expound on the preamp design a bit, but my bet is that any amp that meets that description is going to be fairly interchangeable to the Jubilee, I'd love to hear an amp that fits that description that is not really interchangeable. Poweramp description is something I'll have to give some thought to as well.

e.g. The recto poweramp is very significant in the amp design, as it actually seperates it from the SLO. So something like saggy vs bold, hot vs cold bias (SLO vs 5150), saturated vs dry (most vs VHT\Fryette).

[R.G.]

I admit to a certain amount of confusion about the question that's the topic of this thread.

I'm heavily into the technology of amps, tube and otherwise. I have actually constructed a taxonomy of amplifier structures for the Thomas Organ and UK Vox amplifiers in the past. It's the basis of some of my explanation of how these amps work in the booklets I've published on them. But, being heavily technical, it's a taxonomy on a technical level, categorizing the various stages of the amps as gain stages with their implied frequency range limitations, distortion, feedback natures, and so on, and frequency response shaping items, like filtering, tone controls, and so on. If you've spent long enough studying circuits, a glance at the schematic of an amp and some scribbling and calculations will let you taxonimize most amps in seconds.

If I were to construct a taxonomy of amp designs, I would base it on a description of the gain stages, loss stages, frequency shaping at each point, and distortion characteristics for stages that can get driven into distortion. It's reasonably simple to do.

Constructing a taxonomy of who descended from whom, who influenced whom, who talked to or copied subcircuits from/to, yada, yada, doesn't strike me as very descriptive of how an amp sounds. But then I'm limited by my technical background.

[roberto]

Taxonomy (from the greek τάξιϚ "order" and -νομία "suddivision") implies itself that the "taxonomer" has a deep background on the argument, otherwise it's a "pour parler".
The risk is to do an animal taxonomy where cats and crocodiles are together because they both have a tail, and justify this choice because you love animals.

[brewdude]

Taxonomy (from the greek τάξιϚ "order" and -νομία "suddivision") implies itself that the "taxonomer" has a deep background on the argument, otherwise it's a "pour parler".
The risk is to do an animal taxonomy where cats and crocodiles are together because they both have a tail, and justify this choice because you love animals.

+1
Well said