Author Topic: some help with this 4049 based preamp..  (Read 3103 times)

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dschwartz

some help with this 4049 based preamp..
« on: September 20, 2008, 01:13:37 PM »
Since i absolutely LOVE 4049īs based distortions, i started to design my own preamp using these devices..

i want it to be a 3 channel, independent gain, volume and tone control for each channel (AMZ BMP tone + presence control)..

the basic idea (i took mark hammerīs advices) is an opamp gain stage as a first stage for all channels, with a gain of 10 or more--
channel one is a single inverter, with little gain, then tone control..

channel 2 is basically an opamp boosted red llama, with tone control at the end..

channel 3 will have 3 inverters..iīm still working on channel 2..
now.. my doubts:

this is the schem of the 2 first channels:



the output of the 2nd channel, before the tone control looks like this:



wich looks so pretty- tube-ish compressed smooth top wave...

BUT..the wave after the tone control looks like this


yikes!!!that wave looks to me like fizzy fuzzy splatty farts

the frequency response before (green)vand after the tone control :



if i change the "body" control the post tone wave turns soooooo ugly!!!!!
now.. is that normal on tone controls or effectively the tone control is affecting the inverter so the output turns so ugly??



« Last Edit: September 20, 2008, 01:27:03 PM by dschwartz »
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Tubes are overrated!!

http://dsmnoisemaker.blogspot.com

bioroids

Re: some help with this 4049 based preamp..
« Reply #1 on: September 20, 2008, 04:35:14 PM »
I think any change the tone control could introduce to the inverter stage, would be visible right at the inverter output.

Are you sure that's not how the waveform should look after that particular filtering you are applying?

Greetings

Miguel
Eramos tan pobres!

dschwartz

Re: some help with this 4049 based preamp..
« Reply #2 on: September 20, 2008, 05:16:43 PM »
I think any change the tone control could introduce to the inverter stage, would be visible right at the inverter output.

Are you sure that's not how the waveform should look after that particular filtering you are applying?

Greetings

Miguel
iīm not sure..thatīs what i am asking..
i put the input signal through only the tone control, and the sinewave only changed its amplitute,

maybe clipped waves change forms with this filtering?
----------------------------------------------------------
Tubes are overrated!!

http://dsmnoisemaker.blogspot.com

bioroids

Re: some help with this 4049 based preamp..
« Reply #3 on: September 20, 2008, 05:38:40 PM »
i put the input signal through only the tone control, and the sinewave only changed its amplitute,

So that seems to be working ok. Weird
Eramos tan pobres!

zencafe

Re: some help with this 4049 based preamp..
« Reply #4 on: September 24, 2008, 11:32:53 PM »
Did u try buffering? The input impedance of the tonestack looks pretty low to me...

Nos vemos el Viernes!

D.
Long Life to Cmos

snap

Re: some help with this 4049 based preamp..
« Reply #5 on: September 25, 2008, 02:14:05 AM »
there is a DC path from the outputs of U1 and U3 towards ground, if that matters?

dschwartz

Re: some help with this 4049 based preamp..
« Reply #6 on: September 25, 2008, 04:05:04 PM »
Doug.. yes i used a buffer, and the same result..finally..since everything looks OK, i made a simple diode overdrive ( a la mxr dist+), and had the same kind od response..

i concluded that thatīs the way the wave looks when is clipped and then filtered..only sinusoidal curves were unaffected in shape..

strange....
----------------------------------------------------------
Tubes are overrated!!

http://dsmnoisemaker.blogspot.com

bioroids

Re: some help with this 4049 based preamp..
« Reply #7 on: September 25, 2008, 04:14:01 PM »
Does the weird waveform change in different positions of the filter?

That DC path, I don't know if it may cause this behaviour, but I'd try blocking it with a big cap going to the low-pass part of the filter

Saludos!

Miguel
Eramos tan pobres!

dschwartz

Re: some help with this 4049 based preamp..
« Reply #8 on: September 25, 2008, 05:02:16 PM »
dc bias shouldnt affect, apart from scratchy pots.. i tried blocking dc and the result is the same..

iīm working on a "cmos-lab" buard i designed, that includes the BMP tone control and the opamp gain stage..maybe in real life it still sounds good..
----------------------------------------------------------
Tubes are overrated!!

http://dsmnoisemaker.blogspot.com

grapefruit

Re: some help with this 4049 based preamp..
« Reply #9 on: September 25, 2008, 05:07:22 PM »
That DC path, I don't know if it may cause this behaviour, but I'd try blocking it with a big cap going to the low-pass part of the filter

Saludos!

Miguel

Yes, I'd definitely put a DC blocking cap on the output of the inverter.

The signal on the output of the inverter IS pretty square. It's possible that the waveform should look like that after the tone control, depending on the tone control settings.
Is this all simulation? The frequency response looks reasonable for that type of tone control (without calculating the response).

If you vary the level and/or frequency of the sine wave I think you'll find that the output waveform changes. Is the input a 1kHz sine wave? If you turn the tone control to the bass end and have the body control so it's not scooping the output should look closer to a sine wave.
You really need ears to test a tone control. I reckon if you build it and have a DC blocking cap there it will work fine.

Cheers,
Stew.

earthtonesaudio

Re: some help with this 4049 based preamp..
« Reply #10 on: September 25, 2008, 05:23:03 PM »
That waveform look just about right for a differentiator or high-pass circuit, assuming a square or rounded square input waveform.  I'd reckon it looks a lot different when you turn the control toward the bass side.

dschwartz

Re: some help with this 4049 based preamp..
« Reply #11 on: September 25, 2008, 05:26:45 PM »
That waveform look just about right for a differentiator or high-pass circuit, assuming a square or rounded square input waveform.  I'd reckon it looks a lot different when you turn the control toward the bass side.

on the bass side it looks like a triangle wave (integrator)

grape fruit..the schem posted here is just for proof of concept.. on the real thing there will be dc blocking caps
----------------------------------------------------------
Tubes are overrated!!

http://dsmnoisemaker.blogspot.com

grapefruit

Re: some help with this 4049 based preamp..
« Reply #12 on: September 25, 2008, 05:33:55 PM »
Well congratulations, you have a perfectly working tone control :)
Since what you are putting in is pretty close to a square wave you have the correct output.

Cheers,
Stew.

puretube

Re: some help with this 4049 based preamp..
« Reply #13 on: September 25, 2008, 05:46:05 PM »
Yes, those "tubelike" rounded-tops waveforms can look soft,
but: watch the slopes...

grapefruit

Re: some help with this 4049 based preamp..
« Reply #14 on: September 25, 2008, 05:46:12 PM »
Daniel,

What software are you using for the simulation? I've been looking for something like that.

Stew.

grapefruit

Re: some help with this 4049 based preamp..
« Reply #15 on: September 25, 2008, 05:50:16 PM »
Indeed, if you decrease the time divisions on the scope it becomes more obvious how square it really is.

Stew.

dschwartz

Re: some help with this 4049 based preamp..
« Reply #16 on: September 25, 2008, 06:10:07 PM »
iīm using LTspice..itīs cool, itīs easy to use, and itīs FREE!!!

itīs like pspice, but free..you can simulate any kind of ckts..even tube amps
----------------------------------------------------------
Tubes are overrated!!

http://dsmnoisemaker.blogspot.com

rankot

Re: some help with this 4049 based preamp..
« Reply #17 on: December 09, 2017, 02:51:21 AM »
I know it's quite old thread, but I don't where else to ask: what parameters did you use to simulate CD4049B as amplifier? I tried similar schematic with default parameters (VDD=9  SPEED=1  TRIPDT=5e-8), but I get only HF oscillations.
Ampegulator, Bassballs, Bazz Fuss, Bearhug Compressor, Bronx Cheer, Clean Sweep, Demeter Compulator, Electra Distortion, Engineer's Thumb, Hybrid Fuzz, Orange Squeezer, ProCo Rat, Ross Compressor, Valvecaster, 6J6, SFT 2, Ugly Face, more to come...

rankot

Re: some help with this 4049 based preamp..
« Reply #18 on: January 01, 2018, 02:33:24 PM »
I've found this model in Super Spice, so if anyone needs it, download Super Spice and it is there, listed as AINVERTOR_BUFFERED1_XN.
Ampegulator, Bassballs, Bazz Fuss, Bearhug Compressor, Bronx Cheer, Clean Sweep, Demeter Compulator, Electra Distortion, Engineer's Thumb, Hybrid Fuzz, Orange Squeezer, ProCo Rat, Ross Compressor, Valvecaster, 6J6, SFT 2, Ugly Face, more to come...

DDD

Re: some help with this 4049 based preamp..
« Reply #19 on: January 06, 2018, 12:46:01 AM »
Some new design ideas aimed to improve CD4007UB-based overdrives.
***The article is in Russian. But, there are some sensitive items, so I think if somebody can translate it ...

http://forum.guitartonelab.ru/cgi-bin/yabb2/YaBB.pl?num=1514838111

Too old to rock'n'roll, too young to die