how can i add a mids control to a tube screamer circuit?

[snow123]

i mapped out where i could find shorts (aside from the +9v-gnd and 4v5-gnd shorts)

[snow123]

Pics of the board

[snow123]

and 4v5 is also shorted to +9v

[snow123]

and it turns out that 9v and 4v5 only get shorted to ground when the pedal isnt powered or turned on.

[snow123]

update: now there is a little less distortion, and now the distortion is being caused by maxing out the tone control and the mids control, rather than the mids control and the volume control.

[GibsonGM]

Until whatever is going on w/your power is resolved, there's no point in doing anything further, man! No result will be the real result until then.  You have a lot going on with this (NOT beginner) build.   I was really envisioning you making each stage on a breadboard, testing and adjusting, BEFORE you made it permanent   I might consider doing that here... 

Without a solid workflow, a person is pretty likely to run into trouble on anything more than a fuzz face.

[snow123]

I was really envisioning you making each stage on a breadboard, testing and adjusting, BEFORE you made it permanent   I might consider doing that here... 

yea, i really thought the circuit would actually work after the breadboard, but then i encountered more issues when doing it on vero.

[Kevin Mitchell]

and it turns out that 9v and 4v5 only get shorted to ground when the pedal isnt powered or turned on.

I see you're getting better at building and debugging. That's awesome!
However, does this make sense to you? If so I suggest you backtrack a bit so you don't continue to provide yourself and the folks here with incorrect conclusions.

What test are you doing to conclude that a short exists?
A short is a physicals connection. So it's always going to be there - with exceptions of course for intermittent issues like hardware switching or a connectivity issue like loose copper or bad wiring crossing paths.

So you say there's a short but your explanation suggests otherwise. Unless you're physically making the short happen when handing the board - which is another clue to where the problem may exist.

As always, best of luck!

[snow123]

and it turns out that 9v and 4v5 only get shorted to ground when the pedal isnt powered or turned on.

I see you're getting better at building and debugging. That's awesome!
However, does this make sense to you? If so I suggest you backtrack a bit so you don't continue to provide yourself and the folks here with incorrect conclusions.

What test are you doing to conclude that a short exists?
A short is a physicals connection. So it's always going to be there - with exceptions of course for intermittent issues like hardware switching or a connectivity issue like loose copper or bad wiring crossing paths.

im just using my multimeter on continuity mode to check for shorts

[snow123]

i just double checked the pedal, and it seems like maxing out the tone control starts to distort the circuit, and then maxing out the volume and mids control increases the distortion.

[bartimaeus]

continuity measurements are most reliable when the pedal is powered off. if you find a short when the pedal is powered off, you need to remove that short.

as for the distortion, does it decrease if you turn down the guitar's volume? you may be boosting so much that you hits the rails of the opamps?

[snow123]

as for the distortion, does it decrease if you turn down the guitar's volume? you may be boosting so much that you hits the rails of the opamps?

yep, cleans right back up.
my bridge pickup (which is what i mostly use) is rated at about 16k ohms, if that matters.

[GibsonGM]

This would seem to be directly related to R1 & R2s values, then.   Crank the tone to distortion point, then do the trick described earlier with a pot to dial in to where it stops distorting...keeping in mind that of course, this IS an overdrive, so it's going to do some distortion on its own!!     And - as you turn the tone pot, you might just be re-introducing higher frequencies that have already been distorted, making it appear that the 'tone' is somehow boosting - it probably is not.    You must check at U3 output with an audio probe to see if it sounds good, then go thru the next stage the same way.   This is all compromise in how much gain you allow per stage. 

If you look back at previous responses, you'll see the same advice a few times...you have to adjust how much gain the circuit is providing before your tone shaping, it is the same as turning down the guitar volume pot...

[snow123]

also i should note that i did replace the volume pot (some connections were pretty unstable), and i think that decreased the distortion by alot, and the tone pot seems to have a very sudden drop (not sure how to describe it) when i turn the pot all the way down. so maybe i should replace the tone pot?

[snow123]

the sweet spot for r1 seems to be at around 5.1k.

[snow123]

and the mids control doesnt even boost the mids when r1 is at 5k1.

[snow123]

omfg it still freaking distorts, but now it only distorts when the tone pot is at the last turn.

heres the tone pots sweep with the mids control maxed:

[snow123]

so if the tone pot is at around 80%-90% , and everything else is maxed, it will only have a slight breakup (which is what i want), but if i max out the tone pot. it will distort really badly.
so i guess the issue now is that the tone pot is boosting the mids too much.

[snow123]

the tone control is basically another mids control now..

[snow123]

i think i kinda fixed the tone control by adjusting some values in the mids control and tone control

tone control (with mids at .9):



mids control (with tone at .5):


ive noticed that R1 at 5k6 (instead of 5k1) and C1 at 39n (instead of 47n) works a bit better.