Getting a good Mix control

[Kearns892]

In sprucing up a personal TS derivative I currently have breadboarded, I thought I would try to add a mix knob to add some of my clean signal back in post distortion. I split the dry input and ran one side through the OD and another through a LPB. From there I planned on adjusting the LPB volume to a good setting and replacing it with fixed resistors, but I couldn't find any good settings with the mix knob other than full off or full on, everything in the middle was just watery (?). Did not get the nice crisp sound i had heard from other pedals with this feature. The OD itself sounded fine though. Suggestions for improvement?

[mth5044]

Why don't you try adding in a buff n' blend instead?

[sean k]

Isn't the TS two inverting stages which would end up the same whereas the LPB is a single inverting stage?

This means they are going to do alot of cancelling in the mixing part. You could buffer the input to the LPB with an inverting stage with a small resistor between collector and base to keep the amplification down or sit the collector and emitter on the same size resistors.

[moosapotamus]

Try searching "Sprinkle Drive" (Sparkle Drive clone) for some ideas. That's sort of a tube screamer with a wet/dry blend control.

~ Charlie

[Kearns892]

Try searching "Sprinkle Drive" (Sparkle Drive clone) for some ideas. That's sort of a tube screamer with a wet/dry blend control.

~ Charlie

Hmmm, I don't want to build a sparkle drive clone verbatim, just interested in a mix (Clean) control. I ran a search and could only find layouts no schematics. Tracing it wouldn't be difficult as its pretty much a TS, but do you have a link to the schem just to save me some time?

Why don't you try adding in a buff n' blend instead?

I guess I have a conceptual misunderstanding. The only difference I see in what is happening between the Buff n Blend and what I am doing, is that the Buff n Blend boosts the clean signal and splits that boosted signal into dry/wet as opposed to me boosting only the dry signal. Why would this be advantageous?

Isn't the TS two inverting stages which would end up the same whereas the LPB is a single inverting stage?

This means they are going to do alot of cancelling in the mixing part. You could buffer the input to the LPB with an inverting stage with a small resistor between collector and base to keep the amplification down or sit the collector and emitter on the same size resistors.

I'm not sure I understand what you are saying. The setup I have right now boosts the dry signal only, how would this result in cancellation with the TS? I could just be hearing you wrong, after all I'm the one with a blend that isn't operating ideally.

[Quackzed]

i think sean is saying that the 2 signals are out of phase with one another, so when you add them together instead of adding up they subtract from each other...
basically if the signal is quieter at 50/50 mix and louder at 100/0 and 0/100 mix, they are probably out of phase.
if so, youll need to somehow get one of the signals back in phase by either using a different booster that doesnt invert the signal
or adding another lpb in series with the first to invert the signal a second time, so its back in phase
or you could remove the booster circuit and not invert the signal in the first place.
2 out of phase signals combined tend to sound 'thin' and trebley if that helps.

[sean k]

Thankyou, thats exactly what I was saying...explained better.

Now the thing is to mix the signals at equal strengths and this depends on how far over unity your TS amps things as you then want to build two inverting stages that amp as much so your mix can be as equals. An emitter follower as a buffer would only work if the output from the TS was at unity...well it might work as the buffer is an emitter follower and these do amplify current but chances are it would then require a log pot as mixer and bring signal down to unity.

The two ways that I know of to de amplify outputs from collectors are one to use a resistance from cllector to base to employ positive feedback and mix the nverted signal at the cllector back with the base signal and this inversion brings down the output. The other way is to have two same resistances at emitter and collector, as they do in octave FX where the two outs, one from emitter and one from collector are mixed specifically to cancel and leave the octave harmonic, and using, say tow 10k's results in a lowered output from the collector. 

[moosapotamus]

Try searching "Sprinkle Drive" (Sparkle Drive clone) for some ideas. That's sort of a tube screamer with a wet/dry blend control.

~ Charlie

Hmmm, I don't want to build a sparkle drive clone verbatim, just interested in a mix (Clean) control. I ran a search and could only find layouts no schematics. Tracing it wouldn't be difficult as its pretty much a TS, but do you have a link to the schem just to save me some time?

I wasn't trying to suggest that you build a sparkle drive clone. Just that taking a look at it could give you some fresh ideas to try to get your mix control working how you want. Hence, check these out...

sparkle drive schematic

sprinkle drive schematic

sean k and Quackzed are on the money about getting your signals in phase with each other before you blend them together, too.

Good luck!
~ Charlie