Metropoulos Forum

Hi guys,

Here is a picture of my custom board I just finished. I posted it for some comments on my ideas. I sent it to George, but I have not heard from him. Any comments/suggestions would be great. Here's some of the things I did:


I used the large original size board drilled for the reissue mount spacing. The board will be positioned like the vintage amps because the extra length is on the diode end just like the originals. Because I used the larger board, I could put the two .022 caps on it. I also removed the four 68K CC resistors to mount them on the tubes and make room for the larger SoZo .68 caps. I have used the FRED’s instead of the 1N4007’s and added the master volume mod. If you look closely, I have also realigned all the turrets so they are spaced evenly across the board. This made everything line up nice and straight. Some of the extraneous holes were eliminated as well.

I realize this is not a real copy of a vintage board, but I thought it was a nice mixture of new and old. I’m just hoping is sounds great!

Roger

Looks good. I just picked up some phenolic material to make my own. I've been planning on leaving the 68K resistors right on the tube sockets as well. I'm also going to include a ground buss across part of the board. Let us know how yours sounds.

Very nice work Roger. Be sure to post pics of the finished amp, should be sweet!!

Indeed!!!

Thanks for the nice commets, guys. I have not finished my project as of yet, but will keep you posted. I just read about people changing the 220K resistors to 470K going to the master volume mod. I am contemplating doing this. Any thoughts or comments on this?

Thanks,

Roger

Very nice and neat board.

What part Number are the FRED diodes and who stocks them?
I've been reading a lot of good things about them and want to try a set.

The idea is pretty simple. The Rich mod puts a 500k pot parallel with each 220k bias splitter. Parallel resistances add inverses. So with the Rich master at max volume the resistance will be closer to 150k then the stock 220k. Thats OK if you like a lot if gain or a more warm browned out VH kinda sound, and it seems at least a few people with non-mv SLs do change that stock resistor to 200k or 150k for that reason, but, if you like the open, high headroom kinda crunch, or you just want to keep it truer, your better with upping those splitters to 400k-470k. Most people use 470k. When maxxed the resistance is about 10-20k higher then 220k. Personally Id us 400k or 430k. With 400k your range will be about 211k-222k depending on the pots tolerance and with the 430k your range will be about 219k-231k.

The FREDS I bought came from Don at www.tone-man.com. You can get the exact same part from Mouser. Here is the link:

http://www.mouser.com/index.cfm?&handle ... 0&crc=true

I modified my FREDS. I very carefully cut the top mounting part off flush with the body. It made a much neater appearance on the board.

Roger

Billy,

Thank you. That helped considerably. I am looking for the VH tone, so I think I'm just going to leave things alone for now. It will be easy to change them to 400K-430K later if I want to experiment. This might not be a bad place to put in a switch to be able to change from 220K to 400K resistors. Or, would that affect something else down the line?

Roger

rtcook wrote:Billy,

Thank you. That helped considerably. I am looking for the VH tone, so I think I'm just going to leave things alone for now. It will be easy to change them to 400K-430K later if I want to experiment. This might not be a bad place to put in a switch to be able to change from 220K to 400K resistors. Or, would that affect something else down the line?

Roger

Well were only talking about the max resistance here at full volume. As you turn down the pot your turning down the resistance as well.

Thanks for the link Roger.

Billy,

I understand now. Thanks again.

Roger

Actually thats not totally true. As you turn down you are lowering that splitter resistance but your also adding resistance between the PI signal output and the power tubes. So you may still benefit from using the stock 220k instead of 470k-400k if you wanted to get that more compressed browner sound. Its hard to explain. Its only 2 resistors and with that small turret strip its easy enough to try both. Again you would know that the larger values would get you closer to stock.