Rat Breadboard Issues [SOLVED]

[nero1985]

Hey guys, I put a Rat on the breadboard and while most of it works, there's one thing wrong, I'm getting this stuttering when i play the low E and any note on it.

I have LEDs right now for clipping but i had 1N914s, the weird thing is, i've seen a mod where people put the LEDs on the outside and they both seem to light up and fade out at the same time, with mine they are off sync if that makes sense

The filter is a TRIMPOT, also the only changes are the 560ohm resistor is a 510, and the 30pf cap between pins 1 and 8 is 33pf

EDIT: 4.5v is coming from another breadboard, I kept the power filtering on a separate breadboard so i can reuse it.

EDIT: I replaced the IC with a 741 and it worked without that issue, removed the compensation cap along with it, something seems wrong with the 308. THANK YOU FOR YOUR HELP!

Also i'm attaching an audio clip so you can hear what i mean, any help is appreciated :-)

MP3
http://www.roxxxtar.com/site-files/audio/6f3f07afed1315b38dd77826e51d7602.mp3

The voltages are:

LM308 (from small bear, not the can version)
P1- 8.03
P2- 4.33
P3- 3.62
P4- 0.00
P5- 0.00
P6- 4.34
P7- 8.69
P8- 4.42

2N5458
D- 8.69
S- 2.84
G- 0.00

Here is a shot of the breadboard which i draw before putting them together and the actual breadboard (at the moment i have LEDs instead of diodes for clipping)

[GibsonGM]

What are you powering it with? (batteries or a wall wart supply?)
Something sounds unbiased, to me, which can happen with massive sag.

[nero1985]

Forgot to mention, I have the power sections on another breadboard, I'm using a Dunlop DC Brick which supplies 8.91v

[duck_arse]

where is the 4.5 volts coming from, is it on the other section?

[nero1985]

Yes, 4.5v is coming from another breadboard, i kept the power filtering on a separate breadboard so i can reuse it.

[Fp-www.Tonepad.com]

the breadboard layout will influence the quality of the sound, specially feedback, crosstalk and noise.

[GibsonGM]

the breadboard layout will influence the quality of the sound, specially feedback, crosstalk and noise.

+1   the sound reminded me of massive sag...dropping voltage when low notes "call for" more power.  It shifts operating points around.   What is the setup on the other board (regulator?  What caps?....); what happens if you dramatically shorten the leads going to the distortion board?   Long leads invite oscillation....   

How about just building the Vref right on the board and powering if off a 9V battery to be sure it's not the supply doing this?  Should take like 5 minutes to do.

[nero1985]

Here's what the power section looks like, I've built a lot of distortion pedals this way, the only issue i've had when i did them was the oscillation which with this one i'm not getting any, barely any noise too, which is why I can't figure out what the issue is,

One thing to point is my guitar has SD Alnico 2 Pros which are lower output and are a bit thicker than a PAF style pickup, I have coil splits on it and when i go into coil split the issue is gone.

[nero1985]

I Changed the power supply to be a 9v Battery instead, same results, i'm going to move the Vcc to the same board but I doubt that's the problem, i'm wondering if the compensation cap is the issue being 33pf instead of 30pf, i don't think it would be that but who knows, I also checked all the values for caps and resistors to make sure i didn't put a wrong value there but so far nothing, I'm going to try another IC

[GGBB]

i'm wondering if the compensation cap is the issue being 33pf instead of 30pf.

Won't be that. Try adding a 1M resistor between the 2N5458 drain and gate.

[hymenoptera]

Build the Rat up last night on breadboard using this layout, wanted to say thanks to whoever drew it out. Works great! Sounds even better!

A few changes to mine: I did mine up as per the Mad Bean Slow Loris schematic, since I've got his PCB and will be building that soon, so I added the 1k "sweep" pot in the opamp gain section and the switchable LEDs/10n cap. This circuit really comes to life with the LEDs!! Also used the correct 560R at R5 and a Fairchild 2n5457 at Q1 instead of a 5458. Looking fwd to trying some more ideas before I commit to solder/PCB.

One little surprise that caught me offguard: I added the extra 10k to ground at the output seen in some versions of the Rat, put it on a switch to A/B it, and was surprised to find it has a less-than-subtle effect on the bass response of this pedal. I'm going to add a toggle to the final product labelled "Bass" and "Guitar" so I can switch that 10k resistor in and out of circuit as needed. If anyone hasn't tried the optional 10k at the output, give it a go, you might like it!

[anotherjim]

The bass change with the 10k is interesting  - it shouldn't really be that noticeable. It raises the theoretical response of the output capacitor from almost 1.5Hz to about 15Hz. Possible your output cap is actually less than 1uF?

[GGBB]

Earlier RAT2 and Turbo RAT pedals were the only ones that had the 10k to ground paralleling the volume control. The purpose was so that the LED circuitry (a la millennium bypass) would work. But those RATs also had 10uF output caps instead of 1u, so the high-pass filter knee would remain essentially the same.

There is no reason for the 10k other than the LED circuitry, so it is completely unnecessary in a 3PDT bypass setup. In fact, since the early 2000's all RATs have 3PDT bypass and no longer include the 10k or the 10uF output cap:

[anotherjim]

Thanks, that makes complete sense.