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tone control questions for ts9, SOS, and SB3

8/21/2000 8:33 PM
Gord tone control questions for ts9, SOS, and SB3
I had this problem-  
I wired up a Shaka Braddah 3 (a while ago) and threw in a ts9 tone control, opamp and all. It sounded great! There was something wrong with it, though. It had nowhere near the volume it should have had. You guys might remember the threads about this a while ago.  
I just noticed something today on the ts9 and Son of Screamer schematics. On the ts9 there is a 10k resistor, connecting the input of the ts9 tone control to 4.5v. That resistor is not on the SOS. What is the purpose of that resistor? Why did Jack Orman get rid of it in designing the SOS?  
The reason I'm asking is because in building my SB3, I left that resistor out. Could this be the reason that I'm getting such a massive volume drop?  
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8/21/2000 8:43 PM

That's a biasing resistor. The SOS doesn't need it because the first stage is biased with 4.5 volts. There's no coupling cap between the 2 stages so it "carries over". At least that's how I understand it to be. I asked about this very thing a little while ago.  
Now with the SB3, you may very well need it. If you don't have it, your op amp would have a crackly sound - very weak.  
Try it and let us know.  
8/22/2000 2:07 AM
How to connect opamp for the TS tone?
Thanks for the report, Gord. I'm now trying to do the same using a TL061. I have a couple of questions about hooking up the opamp that I was hoping someone could help out with .  
Here's what I've done.  
1. (Offset Null 1) unconnected  
2. (Inverting input) going to tone pot  
3. (Non-invrt. input) 4.5V bias and input signal coupled with the .1uF form MB.  
4. (Vcc-) ??  
5. (Offsent Null 2) unconnected  
6. (Ouput) ouput  
7. (Vcc+) 9V  
8. (N.C.) unconnected  
My questions are: Did I correctly connect the opamap and does pin four go to Ground (0V)?  
8/22/2000 3:19 AM
I don't quite understand the technical side of these things, but I do know pin numbers, so I can tell you how I hooked it up!  
1&2- Feedback loop. Pin 1 is also the opamp output.  
3- Guitar input  
4- Ground  
5- Goes to the tone pot input & the grounded .22uf cap  
6&7- jumpered with 1k resistor  
8- 9v supply  
I know for sure that this works for a ts9 type pedal, but with the Shaka3, I don't get nearly enough volume. If you hook up the tone control after the minibooster, then you'll have the same problem for sure.  
I hooked up the clipping opamp to the MB, with a .1cap and 1Meg resistor to ground.  
From the MB I went into the 1k res, .22uf to ground, and the rest is tube screamer.  
I forgot to hook up the 10k resistor in parallel with the .22uf cap, because the Son of Screamer didn't have it. If you try doing all this, make sure you try putting the 10k res in place, because that's the only place I believe I could have gone wrong.  
Get back to me, and we'll figure this thing out together.  
8/22/2000 11:27 PM

The 1k .22uf lowpass might be loading down the circuit if I understand the post. Opamps can often drive under 2k loads the output stages are often push pull with low z out. Gain stages have an output z ~= the Drain resistor or the drain resistor. A simple rule is that for good voltage gain the load should be >= 10x the drive z
8/22/2000 4:48 AM

>1. (Offset Null 1) unconnected  
2. (Inverting input) going to tone pot  
3. (Non-invrt. input) 4.5V bias and input signal coupled with the .1uF from MB.  
4. (Vcc-) ??  
This goes to ground.  
5. (Offsent Null 2) unconnected  
6. (Ouput) output  
7. (Vcc+) 9V  
8. (N.C.) unconnected  
It should work.  
You ARE taking everything from the TS from after the 1K resistor (everything from the .22uF and after) right?
8/22/2000 11:18 AM
>>You ARE taking everything from the TS from after the 1K resistor (everything from the .22uF and after) right?  
Yes, thanks. I'm going to finish up this afternoon and try it out. I'll get back to you guys.  
Thanks Aron and Gord!

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