BUFFER BLENDED PROCO RAT

raziellycas · Post by **raziellycas** » 30 Mar 2015, 10:56

Hi! please forgive my english, I'm not mothertongue U_U

I need some help from another couple of eyes in order to check my buffered-blended RAT.
The attached version is the 1.3, I've built the 1.2 and with an active bass seems works but not with a passive guitar.
The main difference between 1.2 and 1.3 is that in early version I've used a pair of 5M resistor instead 1M at the input buffer node (R1-R15 in the schematic), the buffer itself it's a pair of buffers (one for the RAT one for the dry signal) with common signal "+" coming from the input, R14 was missing in this previous version.
Another difference it's the final stage, controls LEVEL, BLEND and VOL are in cascade with nothing in the middle, in this new version I've removed the double buffer at input, kept just one of them and then buffered the output after the BLEND control.
My question is pretty simple, due I'm not happy with the 1.2 version that I've made (with custom diy etched PCB components soldered etc etc) prior the development of 1.3 version I wish to have circuit checked by someone else than me, I'm not an electronic engineer so probably in the 1.2 version there are mistakes, if someone with better knowledge may take a look at the schematic and advice me in case of obvious errors I will be really grateful ^_^

I will use a 3PDT with grounded input in the wiring so I suppose that this "thing" won't pops when turned on, right? at the input there is the pulldown resistor and at the output the VOL control works like pulldown resistor too or I'm wrong and I have to expect that this will pops?

The 1.3 version is based upon the DAM EZEKIEL (http://revolutiondeux.blogspot.it/2012/ ... rtion.html) and the Sean McLennan blender (http://gaussmarkov.net/wordpress/circuits/b-blender/) the RAT schematic it's a modified version of the amazing GaussMarkov ones that's why the resistors and the capacitor counts appears a bit strange, usually I draw my design on paper but in order to psot it on forum I've thought to use a better schematic and edited this ones in EAGLE.

Another question that is buzzing in my head is: in case I'll use bipolar electrolityc capacitors instead polarized ones (I refer for example to C10,C15,C17) may this create issues? due I usually use Nichicon MUSE bipolar capacitors

EddieTavares · Post by **EddieTavares** » 30 Mar 2015, 13:25

There is a secondary signal feed back in that circuit. The signal that belongs the level pot goes to the blend pot, the C15 and finally returns to the rat through the C1. I would suggest you two ways avoid that unnecessary feed back.

There is a diy circuit easy to find on internet that is called Sprinkle Drive that is one off rat variants, see below:

As you can see there is two separated signal paths mixed in before the volume control, I like that one a lot with my stratocaster.

Another one is the equivalent rat bass pedal called Juggernaut:

Both are in the same world.

raziellycas · Post by **raziellycas** » 30 Mar 2015, 15:54

Hi, thanks for the advice!
Will works if I increase C10 to 10uF (as the sparkle) and wire LEVEL as a signal attenuator instead a VOL with signal passing by 3-2 pin shorted and then from 1 until BLEND?
R16 it's needed? and eventually it's needed a mirrored resistor from signal path to ground after C10?

EddieTavares · Post by **EddieTavares** » 30 Mar 2015, 16:42

To avoid the undesirable feed back try to move one of those IC buffers to work between the rat input and the mix pot and be happy.