The Amp Garage

I have a 50W JMP'ish that I built a number of years ago and hav been tweaking ever since. Actually, started at an JTM-45 with RS transformers, then Drake, then JTM 50 and now its like a mix of JTM/JMP/JCM. I really like what I am hearing when dialed up but one final adjustment I'd like to make is sp...

Interesting! I even could read about people splitting the cathodes of a push-pull to use mismatched tubes, possibly not of the same type. What sounds good to him might not sound good to you, & vice-versa... 8) You know how cathode bypass caps work? Well that's it! (U may want to Google that otherwi...

Found a great video on this

https://www.youtube.com/watch?v=HrkYUPmEUhk

danman wrote: ↑Sun May 03, 2020 2:52 am This may help you.

http://forum.metropoulos.net/viewtopic.php?f=26&t=15719

The boards changed slightly over the years but this should have the info you need.

Thanks for this! I actually stumbled upon it after posting the question. This is perfect. Exactly what I was looking for.

What sounds good to him might not sound good to you, & vice-versa... 8) You know how cathode bypass caps work? Well that's it! (U may want to Google that otherwise) I understand what you are saying, but there is no harm in asking for an opinion. Not everything someone says has to be scientifically ...

Thank you! Do you happen to know if that mid boost you speak of sounds good?

I have a JTM 50 clone that I want to hot rod and the first thing I'm planning on is to bring it closer to JMP 50 spec, starting with the shared cathode on V1. I'd rather not split due to lack of room on the board and was wondering if the lead channel would sound the same if I just changed the values...

Thank you for the information.....I'll do some viewing on YouTube as you suggest. Just realized that it sounded like I was giving that "search for yourself" answer that annoys me. I was really just trying to get you to check out those clips and not settle for just the technical jargon. Komets are a...

If your looking for a technical answer I'm sure someone will chime in, otherwise go to the Komet web site for a description. Even better check the Komet Concode clips on YouTube by Pete Thorn. He demonstrates the fast and gradual modes in 2 separate videos. Fast Mode: more gain. Louder. Faster attac...

Do you have someone who can look at it on an oscilloscope? Possibly a high frequency oscillation? Do you have the original tubes that worked? Can you put those back in? No, unfortunately, I don't but picking one up and learning how to use one was on my short list of things to do. Are the handheld s...

Is the bias in good range, I've had amps where the bias was too hot and take out a tube. By the way you did a very good job building this amp hope you or someone can identify the problem so you can enjoy. Appreciate it Mark. I had the bias set a bit low as a precaution. About 25-30mA. I'll figure i...

I think that's the one I went off of. Since mine is a hybrid I'm going off the K60 chart because that how my preamp section is wired. You can see that my voltages are pretty much on.

tubeswell wrote:Have you measured the OT Pr:Sec VAC ratio yet? (for both sides of the primary)

Please tell me how to do this and I'll test it tonight. Not sure what you mean by ratio, but I did measure the secondaries at pins3 of V4 & V5 and got 487V

Under the filter cap board did you wire that correctly? Did you use the two other filter caps under the board? Yes. You had sent me the board layouts a couple months ago and I followed them to a T. Only difference is that I replaced one of the 80uf caps with a 220uf per Concorde spec. The two 80uf ...

tubeswell, I posted the voltages. If there are others that I need to check please tell me how because I'm not following the lingo. Newbie here. g2 = shorthand for "screen grid" (g1 = control/signal grid, g3 = suppressor grid, k = cathode, a = plate/anode) You posted the cathode and plate voltages e...