Shaka 5

[aron]

Oh yes, no offense taken. When the Shaka 3 came along, Jack was helping and feeding me all sorts of designs which I would try. He had a lot of ideas and I was ready and willing to try them. I never even knew about the "internal diode" at that time. I just connected things up and if I liked the sound, I went with it.

[Kipper4]

I see what you mean now Aron. Although i though for a while you were litterally using a series diode in the signal path not NFB style.
I have seen series diodes suggested by Jack in his clipping article.

[mac]

I'm sure i read somewhere that part of the mosets character comes from the fact that it has a high capacitance compared to most others. Indeed when measured the capacitance was over 1nf on my little chinese tester.

Unused leaky germs, like bad ACxxx, have high internal capacitance too.
Or maybe a cap across the diodes, like in the Dist+.

mac

[Kipper4]

Really I never knew that Mac. Sweet bit of info.
I have lots of ac153 with low gain so that maybe an option.
I'll take a look at the dist+ too although I feel sure I must have already made one as a debutant.
Cheers guys

Edit: I see what you mean about the cap in parallel with the diodes in the dist +.
A similar thing is already used in the Shaka 5 too and the cap size does make a difference.
Note that Aron uses a 220pf and I'm using a 10nf.

Hopefully sometime this weekend I'll get to do a bit more.

[mac]

Talking about caps, just an idea:


-----|<-----|<----- gnd
         |
-----||-----||----- gnd


----->|----->|----- gnd
         |
-----||-----||----- gnd



mac

[Kipper4]

I m having a high pitched squealing when the treble if flat out with this .
I tried a low pass filter 750 Hz Fc on the output I didn't fix it
Need some help and inspiring .
Thanks
https://http://imagizer.imageshack.com/img910/5274/19zyMT.jpg

[Kipper4]

I should add that if I reduce the gain (level pot) the noise goes and that there's a point in turning the level pot where it goes quite.

[snap]

that schematic looks funny to me. So unhorizontallined.

[Kipper4]

Sorry the image didn't work

Here's a new one



https://http://imagizer.imageshack.com/img537/4530/DcBMVt.jpg

[samhay]

A cap (maybe 100p) from output to (-) input of IC2B might fix the squeal. If not, I don't think it is causing the squeal, but R15 (and R 1) aren't helping, and I would jumper those.
If the squeal gets worse as you turn up the level then a cap across the level pot would be a good idea - 330p to 1n would be a good place to start.

[Kipper4]

Cheers Sam I'll try some of that.

[Gus]

Layout and wiring could be a cause of the squealing. 
Also a DPDT, 3PDT switch can bring the input and output too close together with some high gain circuits

[Kipper4]

Thanks Gus
I'll post up the layout although, I always try to keep good input and output seperated as you point out the switch could be an issue.
I'll report back
cheers guys

[Kipper4]

No Luck yet guys although I still have some of those bits to do.
I got to thinking and wondered what anyone thinks of the idea of moving the active tonestack between IC1B output cap  and The clippers.
I'll probably make the IC1B output decoupling cap  470nf while im at it.
I remembered reading some post talking about predistortion eq or have I got this wrong?
Cheers
Rich

[Kipper4]

I tried all the fixs Sam but to no avail.
Its sorted now. Note. I used an active James tonestack from boss FA1
I changed the NFB resistor in IC2b to 1k8.
How did  I arrive at this I kept turning the old level pot up until it started to squeel which was around the 2k mark. So I figured err on the side of caution and use he next value down i could think of.
Strange though since I'm using a R in of 10k. i thought the least value i would have to use would be a 10k (to make a straight buffer with a gain of 1) since I thought that op amps cannot attenuate. Don't ask me why I thought I rad it somewhere. So I found this a little confusing.
It all works now I just have to test it with the big rig then hopefully tidy up the board. Its had a bit of  bashing with all the mods i've been doing.
Thanks for the help guys. I'll post up a schematic once I'm done.
Rich

[morganharri]

 I am using a half of an op amp for v bias.