What's the distortion adding feature of the new $$L console?

[Kev]

[quote author="mediatechnology"]And where's Kev today?
And PRR to throw cold water on everyone?[/quote]

had big trouble with access yesterday and so have missed your changes

I have a CM simulation going of the pre modified version and although it works ... operates
:roll:
it doesn't simulate they way you wanted it to ... changes R5 to get lower voltages than kilovolts and 10.5K makes U2 approximately unity gain.

a quote from Dad
" From the "x2 or x3 gain power" switch I 'deduce' that the intention was to go "x - log - times two - antilog" expecting to get "x squared" out the far end and, presumably, from "times 3" to get "x cubed". ... but that aint so ..! ?? "

it looks that there could be a misunderstanding with the so-called "log-law" of a PN junction.
It might be that there is a relationship between current through to voltage across that follows a log law but it doesn't perform a squaring operation. ... this a gain controlled amplifier (via the U2 feedback resistor) ?
:roll:

I've rushed the above reply , just in case I have access trouble again so don't pick me up in simple typing/thinking errors or word choices ...
and haven't had time to think about the recent stuff so much but your simulator results could be getting some squaring via headroom/voltage rail effects and so the harmonics
... 'cause our CM model using ideal opamps didn't produce this sort of stuff

for what it's worth and
even though the file is a couple of mods/page old now here is the CM file
http://www.diyfactory.com/data/discussion/Strange.CKT

being in the different time zone and net troubles I probably can't keep up with the thread.
please do look at the simple two operator simulate on my previous post as it highlights the problem of mixing the effect back in with the original.
I feel this is what is wrong with ALL(most) of the saturation style effect units.
To emulate the tube sort of thing I feel that the effect circuit should handle the signal as one signal stream unless the effect stream can have the same phase and group delay.

also I would have liked to spend more time on analysing a distorted waveform to see where and what part of the waveform produces the required sounds we like. I don't think this has ever been done acurately enough before. Also the simulations of Tubes in spice have never been detailed enough to acurately predict the waveform shape of the real thing. Yeah there help to predict that a circuit works but they don't draw the waveform right and so the harmonic predictions are way off.

:sad:
as I've said the simplicity of that two operator mix to simulate a single 2nd harmonic and two very different resultant waveforms say so much about future problems of any simulation or actual completed circuit.

shut up Kev

 

[recnsci]

Ok, here we go again.
To clear some issues first. We are trying to build circuit with static
nonlinear transfer function of polynomial nature by adding various
powers of input to undistorted signal.
That is circuit should perform this:

Vout = A*Vin + B*(Vin)^2 + C*(Vin)^3

there seems to be some missunderstanding bout squaring therm:

For any real x, x^2 will give ONLY POSITIVE VALUE. Output of
squaring device will always give output of same polarity, for both
positive and negative inputs. My guess is thats what kevs dad is refering to

So lets put sine wave in our device:

(sinX)^2=0.5*(cos2X-1)

(sinX)^3=0.25*sin3X-0.75*sinX

so if Vin=sinX than Vout is:

Vout=(A-0.75C)sinX + 0.5Bcos2X + 0.25Csin3X + 0.5B

Now lets get back for the circuit I sent to mediatech. Take a look at
equation thats connecting Vout and Vin, and put some reasonable
values for R1, R2 and Is. You will see that Vout will hit the roof for Vin
in millivolts range. Solution is increasing R1 and finding diodes with Is in
microamper range. But there are bunch of other problems with that
circuit beside this one.

If resistors inside of loop are changed to R and 2R instead of R and 3R
output is Vout= -K*(Vin)^2 for positive value of Vin and Vout= K*(Vin)^2
for negative value of Vin. Output is swinging in polarity with input, so this
is not sqauring device. Solution is to simply put FWR before this
circuit.
With R and 2R we get that K=R2/(Is*(R1)^2). So squaring device
will work for resonable component values and reasonable input levels.

BUt there are several problems. We are operating diodes at very low
currents, which means slow and deviation from expo law for Si PN
junctions. And stability will be a bitch. And few other things.

There is more elegant solution it seems but more on that latter, Im
running home for lunch now.

cheerz
ypow

 

[Guest]

Hi fellow Professionals;

let me join the discussion from my first posting to this forum.

It was a joke initially, the "Ultimate Power Amp Simulator", but who knows? :grin:

 

[Kev]

thanks wavebourn
and that is pretty much what I said earlier about the references to Headwize and the many other simple saturation based ides with zener ladders to ground and in the feedback path.
various resistor/voltage combinations to control the onset point.
(we did look at transconductance amps for while and then the idea vanished )
my point about using the diode was that the onset point is instant... ish and is very amplitude dependant. It doesn't immediately give an opportunity to provide a front panel dial and odds or evens.

I'm still focused on the original thread topic title.

added to that
if it is used as an effect sidechain and mixed back in with the original we have a choice to make on the phase as it is mixed back in.

recnsci's schem is basically one of the variants from those discussions way back then but I do like the second implementation (need to think about it more)
I may come back later to the math and the way it is implemented here.

 

[Kit]

http://www.geocities.com/j4_student/electra.gif

 

[Kev]

that's a typical stomp box approach and suits guitar overdrive and distortion trick but a little hard for mixing desk duties

it doesn't pin point 2nd or 3rd and any control is all about amplitude in and out

 

[Kit]

it doesn't pin point 2nd or 3rd and any control is all about amplitude in and out

True.

a little hard for mixing desk duties

How do you mean?

Not linear enough distortion for you?
:razz:

 

[Svart]

how would using a soft recovery diode change things? what about actual voltage level flowing through the device, does that change in a linear fashion as the potential changes?

 

[Kev]

[quote author="Kit"]Not linear enough distortion for you?
:razz:[/quote]
:grin: everyone's a comedian

good for axe into your amp but I don't think it will bring the Motown sound to a vocal.
Needs to be implemented with a degree of softness and it may go someway there.

[quote author="Svart"]... would using a soft recovery diode change things?[/quote] gut feeling is that for a simpler circuit that make use of a components natural quirks is the way to go
other wise I think a full analog modeling ... reatime ... circuit will be overly complex.
DSP modelling is much easier physicaly but will have a latency issue.

Wayne I did notice the un-symetrical thing
again I'd like to go back to first principles to find if this IS genuinely what makes the harmonics we desire.
if so
a softer onset of this could be cool

 

[Kev]

[quote author="mediatechnology"]Even a multi-diode breakpoint circuit might work. Just as long as it works over a pretty wide range (maybe 40 dB?) without a sudden hard onset[/quote]
that's my gut feeling
ladder ... different zeners ... add the resistor for a softer onset

" The big surprise? Half-wave sounds better ! "
would still like to analyse why or what feature of the half/asymetric is the desired feature

 

[Kit]

a degree of softness and it may go someway there.....

......a softer onset of this could be cool

Ah, yes. But look at how the transistor is biased, Its a simple but clever circuit.

Its not only diode clipping.

The low impedance at diode conduction will alter the transistors gain........giving a "soft knee" behaviour.

 

[Kev]

ok ... interesting

breadboard it !!

as drawn, it is a rather static circuit with only the output control.
so it will be a mix ... wet/dry sort of effect and as I pointed out the phase as it's mixed back in with the original could be an issue

 

[Guest]

No need for ladder, try my drawing. Si diodes in feedback, Ge after.

 

[matthias]

ssl also implemented the basic feature in their new alpha channel

http://www.solid-state-logic.com/music/xlogic_achannel.html


and if you like plugins... there will be something out soon for exact that purpose...

http://www.fieldingdsp.com


but the most interesting point is... how does it sound and is it useful..??

 

[Svart]

yes breadboard it!

 

[Kev]

[quote author="mediatechnology"]Ok, this really cracks me up: Did you see the VHD knob goes to 11?[/quote]
yes I think it does
:green:
well at least I've finally seen the control for this one

‘Variable Harmonic Drive’ circuit; a Time Machine of distortion characteristics

just a single pot

 

[Svart]

Kev you saw the insides of this thing? Tell us more!

 

[Kev]

no I haven't seen in side ... yet
I did try
I had screw driver in hand but the man was not happy and look very uneasy so I backed off
I didn't want to cause him greif

trust me people do look at these forums and when knowledge gets out they do try to track the source

I think there could be a worthwhile thread in this subject
... just look at the recent Tape Op and see the usual suspects and the people that didn't have companies when Tech Talk started and see the new companies

anyway
as Wayne said
root feedback perhaps isn't to far off base
not that I'd expect a great variant from any of the very many versions of this that we have see or talked about in the past

the main point I wanted to get to was that initially someone said there was 2nd and 3rd control ... and at one stage I though someone had suggested it wasn't level dependant

and it is very likely to be a simple circuit otherwise it would take up money and space inside the channel strip

 

[Svart]

very cool.

$$L is very fond of using opamps in wise situations. I assume that it's not only an opamp circuit but a unique and simple design that works well.

Much like where we are now with the group's versions.

 

[Svart]

hmm maybe we are over analyzing the logo, It does indeed look like a sqrt sign but it also looks like a futuristic VD, with the letters very angular.

Who knows, but I think the group version is cool and can't wait to try it myself.