Teeco 610D conversion

[TUBEDUDE]

Maybe replace the 450pF with a 1000pF and a larger treble pot.

[angelodp]

Ok just tried 1M pots for both Treble and Bass, improved. I will try the 1000pf next thanks. Finally have a tone-stack workin here.

Cheers A

[martin manning]

I think a smaller treble cap would move the treble adjustment up and out of the mid range. Typical Fender TS has 250p.

[angelodp]

MM, just went for the 250pf, I see/hear what you mean. I think I am going to create a small eyelet board dedicated to the tone-stack and play some more. Still a mystery why I could not implement the stack between the first and second triode. I'll keep playing with things, but its a playable fun little amp.

BTW I just inherited three older amps to attempt a conversion.

1. Challenger Amp Model CH30

2. DuKane Amp Model 1A385A

3. McGowan M-20

All in pretty good shape, no tubes, but very little rust if any. Wax caps here and there that need to come out.

Wondering which of these is a good candidate to attack first.

Thanks for hangin in there with me.

A

[angelodp]

Ok, well here she is. I worked out a little daughter board so I can easily tweak the stack, but its sounding very nice with a proper working stack now. I do have a fairly larger divider to bring the gain down (4.5M/1M), but all in all its happening.

Thanks for the support. Might try to get a Master in there.

[angelodp]

I have 6.2k off of the Bass pot to ground. I just experimented with a 100k pot (between the 6.2k and ground) to try the RAW setup. All well until about 40k on the pot and then the signal got scratchy and poor quality. I thought that with a large resistance I would basically eliminate the tone stack into pure RAW sound. Have I got that wrong?

[martin manning]

I have 6.2k off of the Bass pot to ground. I just experimented with a 100k pot (between the 6.2k and ground) to try the RAW setup. All well until about 40k on the pot and then the signal got scratchy and poor quality. I thought that with a large resistance I would basically eliminate the tone stack into pure RAW sound. Have I got that wrong?

No, that's correct. Maybe at some point it kicks into oscillation? Long leads on your pot would increase the chance.

[angelodp]

Here is a graphic layout with the latest components. Something strange in this amp its that the tone-stack works well with a 1.5k slope resistor, and not with a larger common value, like 56k or 100k. The foot-switch for the NFB is fine and works and the tone is quite good. I am unclear as to why the 1.5k works where the larger values do not.

I am contemplating a change to the PI and doing a LTP. I'll post as this proceeds.

[angelodp]

Here is my plan for replacing the PI. Does this look workable.

[sluckey]

Using that 6SC7 as a cascaded preamp is a terrible idea. The common cathode sets the circuit up to be prone to oscillate. Using a 6SL7 and separate cathode components would be much better.

[angelodp]

Ok so nix the 6SC7 and rework the first two stages with a 6SL7. Would you suggest inserting the tonestack between the first two stages of an 6SL7?

Would two JJ's be the right move?

[sluckey]

I would put the TS between the triodes. Here's a proven circuit. And the typical slope resistor works just fine. If I had to buy a 6SL7 I'd probably get a JJ simply because of the price.

http://sluckeyamps.com/rocky/rocky.pdf

[angelodp]

Looks Good, will 6v6 and 5y3 work with this plan?

[sluckey]

Yes.

One note... You will have almost no NFB with that resistor.

[angelodp]

You mean the 22k in the Rock-o-la? Might there be any sound clips of this amp?