Proco rat blend pot

[gtudoran]

Hello guys,

A friend of mine asked me if there is any possibility to add a blend knob to a procorat ... could smth like this be done?

Best regards,
Gabriel Tudoran
Analog Sound

[deadastronaut]

to blend a straight signal and distorted?...

straight in pot 1
distortion pot 3
out pot 2...

thats a simple way...others may have better ideas...

[gtudoran]

So i take the clean signal ... stright after the input cap?... i thought of this also ... but was too simple )

Schematic: http://www.tonepad.com/getFile.asp?id=89

So: I take the clean signal after 0.022uF input cap on lug 1 then the distorted signal after 1uF output cap put it to lug 3 and the volume cap will be on the lug 2 of the blend pot... did i get it right?

Best regards,
Gabriel Tudoran
Analog Sound

[ashcat_lt]

Not after the input cap!  There's 4.5V DC at that point and coupling it to the output will not be a good thing.

If you're going with simple passive blend you should expect some tone suck as the pot loads down the pickups.  Better would be to add a buffer before splitting. 

You'll have to experiment with pot value and taper to get a useful blend since the distorted output will be a whole lot louder than the direct clean sound.  I can tell you from experience that it's a bit difficult to get a smooth blend action and end up with something where you get only clean sound at one end of the pot using just a single element pot like mentioned above.

[apotheodaimon]

Old thread, I know; I am looking to do the same thing and am getting rather confused about the above instruction. Could someone explain this for a dummy like me?

[antonis]

PASSIVE blending of two (or more..) signals demands "same" signal level..
(if not, you have to amplify the "weaker" or attenuate the "stronger" to obtain equal levels before blending - then you can mix different signal "amounts"..)


If you want to use just a pot to mix the clean with the distorted signal you have to somehow raise the clean path impedance to match the distorted signal's already raised one...
(the ideal setting would be to double circuit impedance and make the clean path equal..)

If you don't do this, guitar output "sees" a resistance, through clean path, which depends only on pot value (and blend setting) so it is loaded enough and results in level and tone loss..

Pot value also depends on the point of mixing the signals..
(before clipping diodes, before filter, before output buffer or before Level pot...)

P.S.
Neither my English language skills nor my in depth knowledge help to make it distinct and clear...

[apotheodaimon]

OK then, I understood that.

If you were to do it with just a pot, what would be your ideal way to do it? I have pots ranging from 1k to 1meg so anything goes.

I was thinking I'd use a 1 meg pot to get the brightest clean signal possible.

I'm just really not even sure where to take the leadsfrom to get the clean, ddistortion and where to output.

[ashcat_lt]

When I did it I used a quad opamp.  Buffer, split, rat on one side and buffered (with lpf in mine) on the other, blend pot, output buffer with a little "makeup" gain.  I don't know for sure that you need a buffer for the clean side alone if you're not doing the LPF, but it really does make the whole thing more flexible, especially if you ever need a Rat for bass.