Current Feedback Class D examples?

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#41
mcspack said:
I think there was some discussion in that thread of a variable output? But that would have to be figured out and added to the schematic.
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Volume Knob? or Rail Voltage to the amplifier.
You wont drive a class D to clipping. So variable power is a old gimmick for tube amps.

They cant seem to figure out guitar speakers are 100 to 108 dB at 1 watt
So even with 1 watt they exceed the 75 to 85 dB home listening levels pretty much instantly.

Why home use and recording is all done with software.
It finally took that to realize you just turn the volume knob to your listening level.
And you just use normal 85 to 88 dB monitors.
It is possible to make a 3 to 5 watt amplifier and not use a 108 dB speaker.
 
#43
Trace Elliot already did variable output impedance and numerous others.
Was by far the worst amp ever made for numerous reasons. It failed often for many reasons.
But when it did work was a spongy piece of junk.

Genz Benz and Mesa Poopie use numerous series resistors for their class D amps
with a control circuit for " Tube emulation" to kick in at different voltages.
Same old stuff, preamp with a ice power. And switch mode power with excessive
safety features to keep them from blowing up.......boring

Tube Emulation is done in the preamp rather a solid state or class D
specially with Class D the nonsense amount of limiters you need to use will cause
plenty of " tube emulation" aka compression / limiters, excluding some sort of tube preamp as well.
Peavey with DDT and actually GK got it right with limiters that actually worked, then sounded darn
good driven to distortion. Peavey has patents for numerous limiters and are rather genius.

Just because output impedance of a tube amp is poor doesnt mean you want to emulate it.
Has nothing to do with the " magic"
You can set bias on a A/B tube amp for more voltage swing or " Watts"
But you get plenty of crossover distortion. Which nobody bothered to "emulate"
and is by far nothing magical regardless either.

Especially with bass amps the great thing about solid state was the impedance didnt suck.
And was a nice clean snap.
Same with Jazz players who want clean tone, actually are rather impressed how immediate
and snappy a solid state amp is compared to tube.
 
#44
Gentlemen, Even order harmonic distortion. The kind the ear/brain like. SS Class AB current source amp is what Joe R is doing for hifi. If I can get variable output so I can maybe also use it with guitar? I dunno, makes it more interesting to me.
 
#45
@WhiteDragon

topic subject seems to sound like

Current Feedback Class D examples?​

negating the (subjective) need for current feedback in class D amps for guitar use is something I can understand, but a different kind of contribute to the conversation would be more useful.

If you know an example of class D guitar power amp, apart of Quilter's, that truly replicate the "junk" sponginess of Fender Blackfaces, Vox AC30s and tons of boutique tube amps, please tell us because I'll go buy one immediately.

cheers
 
#46
mcspack said:
Gentlemen, Even order harmonic distortion. The kind the ear/brain like. SS Class AB current source amp is what Joe R is doing for hifi. If I can get variable output so I can maybe also use it with guitar? I dunno, makes it more interesting to me.
Click to expand...
Even order harmonics or a Harmonic profile with strong second harmonic. Is talked about and done with many many solid state amps here.
And just being a " tube" amp doesn't guarantee a strong second harmonic. Most push pull into clipping not even close to even order.
Guitar distortion will be far into 15 to 27% distortion and at high frequency the third harmonic will rise no matter what.
If you can make the 2nd and 3rd remotely even, then your doing good.

A string being strummed is already a asymmetrical waveform, and depending on the player, palm muting, pinch harmonics and various
other tones you get with your hands and technique. Can be asymmetrical or symmetrical and change quickly anyways within milliseconds.
Not including speaker distortion is a major contribution to guitar " tone" and a speaker will have very very dominant second harmonics.

So the actual guitar itself and the speaker are already very very " even order" in "distortion" or even "clean" unclipped waveform

Ironically very high sustain and good " crunch" distortion tone from palm muting is completely opposite and very odd order.
And has been shown many many times oddly enough. Good crunch is odd order distortion.

Even order works well for bass frequency and even very very basic solid state amps can have rather strong Second harmonic below 450 Hz.

So the even order magic myth gets old, it is not the magic secret to guitar, and half the crazy and vibrant sounds you can make with guitar
and actual playing technique. Sound Cool and interesting because they are not "even order" at all.

Just a basic follower circuit done with a Fet or Bjt transistor or a tube will make " even order distortion"
And nobody will know the difference because it wont be the usual 18 to 20% distortion that guitarist like from = clipping distortion.
Clipping is Clipping, guitarist like the gain and sustain. And most the magic is gain stages how much or how little. And the FILTERS
pre and post filters that make it actually sound good.
 
#47
Teo said:
If you know an example of class D guitar power amp, apart of Quilter's, that truly replicate the "junk" sponginess of Fender Blackfaces, Vox AC30s and tons of boutique tube amps, please tell us because I'll go buy one immediately.
Click to expand...
There is none and will never be one. It is just a power amp and a poor one at best for MI applications.

Far as emulating any numerous complicated waveforms you would get from any classic amp or classic effect.
Already done. Including any classic speaker.
Well done over 25 years ago, and with modern processor power, very very well done.
Being with even very basic VST, We went through every stage of every amp and effect
and matched the waveform = Exactly more than 20 years ago.

You just run that signal to a amp.
No current drive or amplifier damping emulation needed.

But But But it doesnt have a tube though how can it be? buy a tube amp then.

We play in real time with note attack and real speakers.
Can I emulate the recording you will get with any microphone or any amp = yup

Will a class D amp sound like a Transformer coupled amp, through a real speaker
NO. Why I still own mine and play in a actual band with real amps. Not emulations.
In the studio on a recording, yup the same.

Does my old junk solid state Quasi output sound " tube" yes.
With ancient junk transistor everyone will make fun of , yes
Do I care what they think? no
Does my tube amp sound tube lol = yes
Does it still sound tube with odd order distortion = yes
 
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#51
You would have to use a sense resistor and an opamp before the module. Unlike WhiteDragon I can see the use of current to make the amplifier sound more tube like. More power going into a speaker at resonance and in the high frequencies where the speaker impedance rises. Some speakers sound blah until the output impedance of the amp increases.
 
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