Need Help with Squealing Ruby Amp

[Jdansti]

I built a Ruby and I can play my guitar through it, but I can't leave the gain pot connected without it squealing like a stuck pig. Even without the gain pot connected, it's pretty distorted. Here's the layout I used:



Here are my voltages:

PS 9.56

MPF102
D 4.54
S 2.66
G 0

LM386
1. 1.31
2. 0
3. 0
4. 0
5. 1.31
6.  4.71
7. 9.55
8.  4.58

Here's a top view:



I've cleaned up the soldered side of the board, run a razor between all of the tracks, and inspected it with a high power loup and can't find any solder bridges or any other problems.

Any help would be appreciated. 

[Toney]

Think JRC386 or LM386N3 are recommended for this.
Not sure if that yr issue but I see an N1 in there.

[Gurner]

I've only quickly looked, but one thing that jumps out with your DC readings, is that the power supply voltage to the LM386 (pin6) ought to be nearer 9V - until it is, the circuit won't work right. Also, the output voltage (pin 5) is wrong too  (but that's probably becuase the supply voltage is being loaded down).

What voltage do you see on pin6 with the LM386 removed?

[Jdansti]

I've only quickly looked, but one thing that jumps out with your DC readings, is that the power supply voltage to the LM386 (pin6) ought to be nearer 9V - until it is, the circuit won't work right. Also, the output voltage (pin 5) is wrong too  (but that's probably becuase the supply voltage is being loaded down).

What voltage do you see on pin6 with the LM386 removed?

Thanks for looking at it. After reading your reply I realized that I read pins 5-8 backwards.  It was late and I had been messing with it for awhile. Here are the corrected readings:

LM386
1. 1.31
2. 0
3. 0
4. 0
5. 4.58
6. 9.55
7. 4.71
8. 1.31

Sorry for the confusion.

[Skruffyhound]

I seem to remember using ferrite beads when I was messing with this. It may be your primary problem, but it wouldn't hurt in damping any chance for oscillation.
You have altered the layout a bit, can we see the solder side. I'm interested if that long jumper is still going where it is supposed to from drain to trimmer leg 3, is it being replaced by the long jumper on the right of your board or is it on the solder side?
I find that if it is not necessary to change the layout because of a space issue, then I will build it exactly as shown including even the I/O's etc, one less chance for mistakes to be made.

Good Luck

[Skruffyhound]

Having just recommended you not to change the layout I had a look at the ruby I made to drive my reverb plate where we can see I totally changed the perf layout for no reason 

[Gurner]

if you ground pin 2 (therefore volume pot rolled right back) does it still squeal?

[Jdansti]

I seem to remember using ferrite beads when I was messing with this. It may be your primary problem, but it wouldn't hurt in damping any chance for oscillation.
You have altered the layout a bit, can we see the solder side. I'm interested if that long jumper is still going where it is supposed to from drain to trimmer leg 3, is it being replaced by the long jumper on the right of your board or is it on the solder side?
I find that if it is not necessary to change the layout because of a space issue, then I will build it exactly as shown including even the I/O's etc, one less chance for mistakes to be made.

Good Luck

Thanks.  I put a couple of jumpers in to place the off board wiring for the pots and speaker on the same side of the board. The long jumper on the right goes from the Gain #3 strip to the unused 10nth row.  Now both gain wires can be placed on the left side of the board.

Likewise, the short jumper from the 9th row to the 11th allows me to place both speaker wires on the right side.

Here's a look at the solder side. Note that I accidentally cut the traces in two places. I put a wire bridge across the accidental cuts. The are in the 3rd column, 3rd row (unnecessary repair) and the 10nth column, 1st row.

[Skruffyhound]

Jep, jumper goes where it's supposed to. I can't see any obvious mistakes.

[Jdansti]

Thanks for taking a look. I drew out the schematic based on the vero. I'd appreciate you guys looking for anything squirrelly.

[Jdansti]

Well, I changed the MPF102 to a J201 and it sounds MUCH better!  The MPF102 was hard to bias. The J201 cooperated much better and the squealing stopped.  It sounded great through a 4ohm 2x12 cab.  I also have better headroom before it starts distorting.

The other thing I did was after I got it to sound better, I ran it through a CE0030B based amp from a PaperJamz toy amp and got a lot more volume without much distortion. Probably closer to a full watt.  (see: http://www.diystompboxes.com/smfforum/index.php?topic=97012.msg844525#msg844525)

Thanks Gurner, Toney, and Skruffyhound for your help!

BTW-Skruffyhound- If you have the perf layout that you used for your Ruby could you please post it?

[Skruffyhound]

And it was as simple as that. I just checked the schem against the layout because I hadn't scrolled all the way down  - good for me since I don't really vero anymore.

As regards the perf layout I'm afraid I just perfed it on the fly, why I like perf, you just lay it out like the schem and it works. So no layout, sorry.

Glad you got your Ruby working.

[Jdansti]

Thanks Skruffyhound. I've done some perf work as well. I might build another one from using a different schem and using perf and see how it turns out. Thanks for the idea!

[Jdansti]

Even though I got the Ruby to sound better, I had to build something else to compare it to. This time I built the Noisy Cricket cousin of the Ruby. I used a tried and true schematic from Bevis Audio and just did the perf board thing. WOW!  Much much better this time-from very clean to crunchy.  I'll be build a small cabinet for it with a 10" or 12" speaker.

I never could get the Ruby to totally clean up, although I know that a lot of people have had good success. Either the  vero I used has one or more issues or I screwed up and couldn't find the error. Anyway, I've got a good one now.

[Skruffyhound]

[B Tremblay]

Just to clarify, the layout posted at the beginning of this thread is for a Ruby amp variant that replaces the stock buffer with a gain stage.  The Fetzer-Ruby will provide more gain (and as a result, less clean sounds) than the stock Ruby.

[Jdansti]

Just to clarify, the layout posted at the beginning of this thread is for a Ruby amp variant that replaces the stock buffer with a gain stage.  The Fetzer-Ruby will provide more gain (and as a result, less clean sounds) than the stock Ruby.

Thank you for clarifying this. Now it makes sense as to why I couldn't get it to clean up.