Proco RAT - no sound after diodes added

[Elijah-Baley]

I made some tests after several research.

I socketed: C6 4.7uF, C11 3.3nF, C12 22nF, C13 1uF; R7 560R, R9 1.5k.
I swapper C6 with a 10uF for getting more fullness, but I can't hear much difference. Same for C13, swapped with a 10uF as newest version, no much effect.
C11, C12 and R9 shape the tone. Tried some close values but with very subtle effect. I was trying to make the filter pot more usable. With a 47nF for C12 move the tone toward low frequency.
I have to make further tests.

[GGBB]

Latest version of ProCo Multi RAT schematic:


C12, C13 aren't going to be useful. For more solid bottom end, change c6 to 10u AND change R7 to 270. For even more bass boost, increase C6 and decrease R7 more, keeping the knee frequency of that filter around the same point (e.g. 22u/120R). The goal is to increase the gain while preserving the shape/RAT tone. It is a little on the subtle side, but once you get to the point where its an obvious/dramatic difference, the pedal stops sounding like a RAT. Increasing C6 alone doesn't do much at all, but along with decreasing R7 it does help noticeably.

The key to making the filter pot more usable is to figure out what range you use on the original and then dial that in by increasing R9 and using a smaller pot and adjusting C11 if necessary. This old post of mine might give you some ideas: http://www.diystompboxes.com/smfforum/index.php?topic=91080.msg776687#msg776687.

[Elijah-Baley]

Thank you, GGBB. These infos will be very useful to me.
(Too bad, I have not 50k pots as filter.)

[Brynngar]

Hey guys,

so, I built a second RAT. Good thing about it is that I finally got some veroboard and sockets, so the process was a lot easier.
But then, kinda as expected: Still the same issue - no sound!
I am super frustrated by now, since there must be some crucial mistake I'm doing every time...
Here the pics, I already checked for solder bridges (there are none) and the components are also correct (which, as I found out, was
not the case with my last version). Schematic and layout still the same.

Measurements will follow later today, but my first measurement yesterday yielded similar results to the other RAT.
Oh, and the IC I used (because the one I ordered is not here yet) is a TL074.

[antonis]

In your pics I see a TL072 (not a TL074) which is an Dual Op Amp and it's pin-out are totally different of those of LM308..

[Elijah-Baley]

I think is hard make the same unwilling mistake on two boards, or two different mistake with the same result. Thought in this case you got no sound, and the causes could be different.

Of course it is a TL072, but pay attention, I'm not sure that IC should be ok with this circuit. GGG suggest TL061, TL071. I assume TL081 could be right.

[GGBB]

TL072 will not work in a layout designed for LM308. TL070, 71, 80, 81 wlll work but might not sound right or as good or like a rat should sound. OP07 is another option.

Always always always verify pinout compatibility when substituting parts, especially opamps, using the data sheets, BEFORE building.

[duck_arse]

as the fellows say, tl072, tl074, tl0x2, tl0x4 won't work. also, in the top row of your build, you need to cut the track under the greencap (?value? can't remember). this applies to ANY cap run east-west on vero. also resistors.

also, you probably want to try using a smaller drill bit to cut the tracks, or an exacto knife for some better precision. it will result in less damage to the tracks. damages tracks means poor and problematic connections.

[where's that bloke from hamlin when we need him? what was his name "pies", or something?]

[Elijah-Baley]

When I plan a project, before to place the order, I make a research about it, for replacements and mods. I replace parts just if I can't find the original, but I ask before or I look alternative verified layouts.

I cut the traces with a 4mm dril. I scratch until the trace is interrupted, but I never make holes.

[Brynngar]

Ahhh yes, sorry guys. It's just that I had this one lying around and in my hurry (desparation) just plugged it in (while misreading it's name).
I'll just wait for the 'real' one, the LM308 that I ordered. Thanks for not kicking me from this forum due to my... lack of proper planning? 
Again I'll give you an update once the new OP-amp is here!

As for the track cutting, I kinda.. took the whole "cutting" business too serious I guess, once I read about people using drills...
Oh, and there is indeed a cut under the greencap, though more subtle than the rest 

[Elijah-Baley]

There's a nice tutorial about veroboard on Sabrotone web site. Try to take a look.
I count always the cut traces, look with my eyes and check with the multimeter.
I tried to make everything fine, planning well, with a lots of informations, checking every components, measuring, look the board, he soldering, etc... but sometime a little mistake is unavoidable. Also I learned about them.

[Brynngar]

Yeyyyyy, good news everybody:
The matter has been resolved! My 2nd attempt works like a charm after the correct IC arrived in the mail today. The issue with the first one was
that some of the caps I used were pretty hard to read due to small letters etc, which resulted in me mixing them up somehow... changing them for the correct values
should solve that problem as well. If anyone else is building a RAT and runs into a similar issue, I can send you my measurents etc 

[antonis]

I can't imagine how some wrong value or mixed capacitors could result on this:
<I tried it out and it worked, but gave a clean signal. That's when I noticed that I forgot the diodes. After installing those, it gave me no more sound whatsoever.>