Rat Capacitor values (tagboardfx layout)

[jonny toetags]

Hi,

I'm building a Rat using this layout


My question is about the two '1u' capacitors. Does that mean 1uf? that seems a little big to me.
Ive looked at schematics and i don't see any 1uf caps listed.

[Govmnt_Lacky]

I see them on plenty of schematics although they are electrolytics.

[IvIark]

I've got 1uf caps in that Panasonic range which is why I used that type in the layout, but if you want to use electrolytics or tantalums, the left hand cap has the negative lead down, the right hand cap has the negative lead up.

[R O Tiree]

There are 3 of them in this layout.  The 2 at the bottom-left should have their negative leads connected to the GND rail (down)  The one up in the top-right corner should have its negative lead "up", ie connected to lug 3 of the Vol pot.

[Kesh]

There are 3 of them in this layout.  The 2 at the bottom-left should have their negative leads connected to the GND rail (down)  The one up in the top-right corner should have its negative lead "up", ie connected to lug 3 of the Vol pot.

one of those 1u is a 1n. i read it as 1u too for a second. we're both dyslexic i guess.

OP, the 1u on the right is for dc blocking the signal and probably best kept as a 1u poly. if your signal is muddy and low you could lower it.

the 1u on the left that AC grounds the 4.5V rail is often a higher value electro in many circuits. 47u seems the norm

[jonny toetags]

I marked a picture so I understand better


So for 'A' i can sub for a lower value poly cap? What value should I use?
And for 'B', I can use an electrolytic?

[Kesh]

Other way around.

A is usually a 47u electro (in any pedal that needs 4.5V). It AC grounds the 4.5V supply.

B is the coupling cap. Leave it as 1u if you want to follow the schematic. Drop it if you know anything that comes after the pedal is high impedance, or don't mind losing some lows. Most schematics say use an electro. Using a poly is more "boutique", whatever that means.

[GGBB]

So for 'A' i can sub for a lower value poly cap? What value should I use?
And for 'B', I can use an electrolytic?

In the RAT, A and B are always 1u polarized electrolytic (except in RATs with the LED bypass circuitry - not this layout - where B is 10u).

http://www.aronnelson.com/gallery/main.php/v/diyuser/GGBB/Multi-RAT.png.html
A=C2, B=C13

[R O Tiree]

> one of those 1u is a 1n. i read it as 1u too for a second. we're both dyslexic i guess.

Oops   Dyslexia Rules KO!

BTW... Did you hear about the dyxlexic, insomniac agnostic?  Laid awake all night wondering if there was a Dog...

[jonny toetags]

Got it 'working' but it isn't producing any distortion.
The volume knob adds loads of volume (too much imo), filter knob works as its supposed to and the distortion knob does nothing.
It's almost acting like a db booster.
Any ideas?

[Kesh]

If the sound is clean and your distortion knob does nothing, then pin 2 to pin 6 of the IC is probably being shorted out. That is the negative feedback circuit.

Or maybe shorted back to pin 2 through the 1K off pin 6, for instance. Or shorted out on the actual pot wiring.

Or you could be bypassing the IC altogether.

Very hard to debug on the internet, but the feedback circuit of the op-amp is the first place i'd look if you are getting the symptoms you describe.