Adding a tonestack to Tubescreamer

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Adding a tonestack to Tubescreamer

Postby caspercody » 02 Jan 2010, 03:08

Has anyone tried adding a tonestack to the Tubescreamer? I tried adding a Baxandell, but lost any unity gain. I would like to add it before the buffer, and make the buffer into a gain stage?

Thanks
Rob
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Re: Adding a tonestack to Tubescreamer

Postby ansil » 02 Jan 2010, 05:38

yes i have done so but you need to make sure you set the impedance right before the tonestack if you are using duncans tsc otherwise it will not respond in the same way. have you tried building a "tube" tubescreamer works quite nicely

ed
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Re: Adding a tonestack to Tubescreamer

Postby caspercody » 02 Jan 2010, 05:52

I have an extra Tubescreamer build laying around, and I wanted to try this. I added the tonestack, and it works. But the volume needs to be turned to max and not quite unity gain. I added some componets, like in the Gus pedal, to give it a x2 added clean gain using the second op amp but did not add much extra gain. So,does anyone have a diagram showing how to wire up the second op amp as a recovery stage?
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Re: Adding a tonestack to Tubescreamer

Postby ansil » 02 Jan 2010, 06:14

well it depends on how you are putting it in. if its after the first gain stage. you should lift the cap to ground that rolls off the 720hz high end and let it hit the baxandall without the attenuation. then if you look at duncans tsc the baxandall as shown flat "ie in the middle position on both sliders you are aproximately -22db in the hole. so you need to convert the second gain stage to around 25db gain to get roughly unity. utilizing the calculator online at muzique.com

figuring something around 12.6 gain is going to get you there unless i did my math wrong. it looks as if to me though if i were doing this i would remove the 1k resistor in the feedback loop of second opamp and add a small trimpot there at around 100k. and keep the 220 ohm from the original tone control circuit. and dial it in when you like where it is set it with some hot glue and call it a day.
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Re: Adding a tonestack to Tubescreamer

Postby caspercody » 02 Jan 2010, 17:08

Thanks Ansil, I will give this a try.

Just to confirm, remove C5 (0.22) to get rid of the roll off. Replace R17 with a trim pot. I already removed R20 (tone pot), C9, and R11. But you say to keep R11? These component values are from the schematic from GGG web site.

I thought I would need to add more components to get a bigger gain from the second opamp?
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Re: Adding a tonestack to Tubescreamer

Postby ansil » 02 Jan 2010, 17:14

well you can use any value keeping r11 will give you a divisor of 100000/220 max gain of 454 which would be ridiculous amount of gain but if you have already removed it try a 1k
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Re: Adding a tonestack to Tubescreamer

Postby caspercody » 02 Jan 2010, 17:40

Something like this? But change the 14k pot to a 100k pot?
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Re: Adding a tonestack to Tubescreamer

Postby caspercody » 02 Jan 2010, 17:43

And also, the R11 in this is connected to 4.5v. In the schematic for the TS it is to ground?
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Re: Adding a tonestack to Tubescreamer

Postby ansil » 02 Jan 2010, 18:01

yep that is it. keeping it from 4.5v keeps you from having to put a cap on it.
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Re: Adding a tonestack to Tubescreamer

Postby Dirk_Hendrik » 02 Jan 2010, 19:04

caspercody wrote:Something like this? But change the 14k pot to a 100k pot?



Won't work. You'll need a cap in series with that 1k resistor to 4.5 volt or you'll clip against the Vcc in no time. You're amplifying the DC now as well. That means that with an amplification of 2 you're at 9 volts already.
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Re: Adding a tonestack to Tubescreamer

Postby caspercody » 02 Jan 2010, 21:54

This is what I added already (the X2 added clean gain after the 10n cap). But did not help much. Is there a way to get more gain using this?

Thanks
Rob
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Re: Adding a tonestack to Tubescreamer

Postby ansil » 03 Jan 2010, 05:29

in this schematic you show the last stage is a unity buffer it provides not voltage gain may i suggest a reading of the basic fundamentals of the tube screamer at geofex.com.

and dirk my friend i think he knows he posted a scheme connected to 4.5v and was planning o rectifying that to ground at least that is what i was getting out of it anyway.

a unity gain opamp isn't going to give you a lot of signal to play with. you need 25db of signal gain.

Image

this shows how far below the zero db line it is. now i am not sure how hot the output of a pedal is but most of mine will drive line level this is the "flat" setting.

Image

here is the total sweep of the tone stack you see how in depth the movements are there is a ton of sweep range going on here.

you will need something like 10 to 20x to give you some gain back. that is why i recommended leaving the stock setup and simply adding the trimpot across the terminals where the resistor once was.
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Re: Adding a tonestack to Tubescreamer

Postby caspercody » 04 Jan 2010, 00:14

Got it working. I read up more on the TS circuit, and I did not remove R6, and C5. I removed these components and just left R10 on the second op amp and I have unity gain. Now I need to look into why when I turn the bass control to zero I get a awful high treble shorted sound? I am wondering what R3, and C3 have anything to do with this?? I used a baxandell tone stack.

Thanks!
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Re: Adding a tonestack to Tubescreamer

Postby ansil » 04 Jan 2010, 01:34

r3 is the 10k emitter resistor shouldn't be effecting it at all

r6 c3 form a notch filter which is set at 720hz aproximately. which is 6.28*.047*.0047 which gives up 720hz high pass filter

c5 and r8 together form a lpf which is set at 723hz

6.28*.001 * .22
r10 is part of the bias circuit. what schematic are you using???? you said you were using GGG schematic. but your no.s are way way off.

http://www.generalguitargadgets.com/pdf/ggg_its8_sc.pdf
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Re: Adding a tonestack to Tubescreamer

Postby Dirk_Hendrik » 04 Jan 2010, 10:32

Maybe this one might help ye too:
http://www.dirk-hendrik.com/cm_heavy_drive.pdf
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Re: Adding a tonestack to Tubescreamer

Postby caspercody » 04 Jan 2010, 19:44

Sorry, you are right I did look at the wrong schematic when I wrote those component names.

What I did is remove the input and output buffers. So my input comes into R3, which I changed to 1M (but this still clicks when I hit the bypass switch??) I removed C4, R8, C5, R20, C9, R11, and R18. I changed C3 to 220n, R6 to 1k, and C8 to 15uf. And output from lug 2 on R21.

I added a three way switch to switch between mosfets, leds, and diodes for the clipping.

I added a baxandall tone stack between pin 1, and pin 5 of the IC.

I got this to work, with unity gain now. But when I turn the bass control to zero I get a high treble kind of shorted sound??

Thanks Dirk, I will look at that schematic and look for ideas.

I am just doing all this to experiment. I have mage about 20 some distortion pedals from layouts, and pcb found on these forums. Now I want to try different values, and adding one part here and another part there.

Thanks for all your help with this!!!
Rob
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Re: Adding a tonestack to Tubescreamer

Postby ansil » 05 Jan 2010, 05:57

well if you look at the graphs i posted above with bass all the way down you have a giant treble spike at around -6db or so and your bass is around -44db so that would make some sense

ok more gain out of first stage i like it.. same resonant freq response though the .22uf and the 1k still makes 723.8hz though so no increase in low end into the tone stack.

what about the output i can only assume you have r17 the same but don't have a source to ground now or at least by what i read anyway. so it sin't contributing much in the way of recovery gain.

however the 15uf output should beef it up nice
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Re: Adding a tonestack to Tubescreamer

Postby caspercody » 06 Jan 2010, 04:24

Yes, R17 is the 1K. It is just connected between pins 6 and 7 and than pin 7 to the 15uf cap.
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Re: Adding a tonestack to Tubescreamer

Postby pedalgrinder » 15 Dec 2011, 01:55

hello everyone here is a neat way to add a midrange control to your tubescreamer without affecting the original baxandall tone control section you have modded in to your tubescreamer so here is the circuit enjoy!!!!!!!


Mid frequency tone control.jpg
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