Quilter Labs?

[olddawg]

Does anyone know anything about their "proprietary" technology. Their amps seem to to sound ok in small light packages. They just can't seem to get their shit together with small things like a clean/dirty footswitch. The 101 model is interesting.
Quilter Performance Amplification
http://www.quilterlabs.com/index.php.../101-mini-head

[nickb]

Does anyone know anything about their "proprietary" technology. Their amps seem to to sound ok in small light packages. They just can't seem to get their shit together with small things like a clean/dirty footswitch. The 101 model is interesting.
Quilter Performance Amplification
Quilter Amps

Almost certainly a class D amplifier with a switch mode power supply. You don't need to change much to call it 'proprietary'.

[olddawg]

Almost certainly a class D amplifier with a switch mode power supply. You don't need to change much to call it 'proprietary'.

I know that the power amp topology would have to be Class D. The difference will be in the preamp section. They say it's all analog but different from the common designs.

[nickb]

I know that the power amp topology would have to be Class D. The difference will be in the preamp section. They say it's all analog but different from the common designs.

I can see that the preamp filtering ( tone shaping) takes a very different approach. The treble middle bass stack have been replaced by the TRI-Q, Hi-Cut and VOICE knobs. That's pretty original. Sorry I don't know about any internal specifics.

[mhuss]

Quilter is also QSC, so he likely knows a thing or two about building sturdy solid state amps.

[olddawg]

Quilter is also QSC, so he likely knows a thing or two about building sturdy solid state amps.

They deleted me from the "Comments" on their Tone Block advert because I was asking if it was just a conventional master volume going into a 200 watt Class D amp or they were using some kind of power scaling because there were "wattage" selections and if it was just a modeling preamp mated to a blaring Class D output stage. I mean who really needs 200 watts for guitar anymore?..... Even if it fits on your pedal board. They said that it was discrete analog and proprietary. Kind of annoyed me. But I have been hearing good things about them. Supposedly, they have a more "tubelike" glassy sound. But every SS amp maker has said that for 50 years. If it is new and different technology and more portable, I'm all for it.

[teemuk]

Compiled from their patent:


It's a power amp emulation. So far I haven't found anything about their preamp technology.

Function of asymmetric clipping cell is obvious, the "zero crossing processor" generates crossover distortion and "soft clipping cell" peak clipping, both made dynamically variant by "sag controller", which is practically just a voltage regulator driven by "enveloped" presentation of the signal. Overall the clipping characteristics should very much resemble those of a transformer coupled push-pull tube amp, including characteristics like "sag". Global current feedback is used to increase output Z, similarly to tube amps. An analog error amplifier is incorporated as an insertion point for GCFB.

Works. The circuit's overdrive characteristics are very similar to typical push-pull tube amps found from instrument amps. Quilter has probably fine tuned the design even more but as is it very closely emulates certain "tube amp" characteristics people expect to hear.

Reminds a circuit Line 6 incorporated to some of their amps several years ago. It worked exactly on same principles as this one but the circuit arrangement to achieve that goal was a bit different. The power amps, IIRC, were also just analog chip amps so in respect to Quilter they did have a headroom lack.

BTW, I don't know if Quilter engineers have accounted fo it in the final design, but the sought after characteristics of current feedback is that it makes power amp gain variable. With "preclipping" solutions this introduces problems: If you set the output level so that system "soft clips" at certain input signal level (because signal is "pre" soft-clipped before power amp stage), that same input signal level will at different frequencies result to different output signal levels due to variable gain. These will most likely cause the final stage(s) of the power amp to clip, probably with less favourable characteristics. Additionally, the global feedback chain becomes ineffective due to clipping.

I would "clamp" the power amp with some sort of diode clipping circuit that works right below power amp's own inherent clipping threshold. Of course this uses a class-D amplifier, and some of them already incorporate various "soft clipping" mechanisms simply because clipping in class-D is often due to overmodulation and avoidable at all costs. At that point its worthwhile to tamper the modulation system and at the same time achieve characteristics such as much less obtrusive overdrive.

Though Quilter is on the stage right now we should remind ourselves these kinds of circuits have been around for years. Peavey is a good example, so is Roland, Hughes&Kettner, Korg/Vox, aforementioned Line 6, that Pritchard guy has also for long time introduced fascinating concepts and ideas about tube modeling. All have introduced us analog circuits that emulate push-pull tube power amps to admirable degree. Personally I find the whole topic more exciting overall than ideas of a single company, which I unfortunately can not consider that "proprietary" given the degree of competition.

[Mike Sulzer]

BTW, I don't know if Quilter engineers have accounted fo it in the final design, but the sought after characteristics of current feedback is that it makes power amp gain variable. With "preclipping" solutions this introduces problems: If you set the output level so that system "soft clips" at certain input signal level (because signal is "pre" soft-clipped before power amp stage), that same input signal level will at different frequencies result to different output signal levels due to variable gain. These will most likely cause the final stage(s) of the power amp to clip, probably with less favourable characteristics. Additionally, the global feedback chain becomes ineffective due to clipping.

A tube output stage, in addition to having a high dynamic output impedance (that is, behaving more like a current source than a voltage source when operating in the linear range) is "current starved"; that is, when it hits its limit, it is not able to supply much more current, rather than connecting the speaker to the power supply rail, which is know of what most SS amps do.

So if you are using current feedback in an SS design to obtain a relatively high output impedance, limiting the input voltage (pre-clipping) limits the output current, and so is similar to what a tube stage does.

I do not understand your comment about the frequency dependence.