The Amp Garage

Well, I hate to jump on to this bandwagon, but I desperately needed some parts for a circuit mod, and I placed the order with Watts Tube Audio <https://tubeamplifierparts.com/>. It appears that my order simply died, with no shipping confirmation, no email response, and a telephone voice-mail which d...

Problem solved! Thanks to all who replied to help me. The issue: floating ground-reference resistors in the PI circuit. As a consequence, the input grids were floating or semi-floating. I must have missed that connection during the build. Surprisingly, the amp has a number of playing hours on it in ...

I can do voltages; regrettably, I cannot post pictures. I do not know why, but neither my home nor work computer will allow me to access TAG, as some kind of malware detection trigger is getting tripped. I can only access this forum via my iPad currently, and I cannot post photos over. I'll work on ...

Other things...... I lifted the 220 uF power tubes' cathode by-pass capacitor (runs in parallel with the cathode resistor) -- no difference. I also pulled the phase inverter tube (looking for an oscillation, possibly?) and again, no difference on the really hot bias at the power tubes. There is just...

Thanks Mark..... I did not have a 62 Ohm value in the parts bin......I had a 150 Ohm 10-watt resistor, so I expected a very cold bias when I removed the (stock) 50 Ohm value cathode resistor and replaced it with the 150 Ohm resistor. To my surprise, however, the 150 Ohm cathode resistor resulted in ...

I am really lost on this one...... Rocket-inspired build.....quad of EL84s cathode-biased via a single 50 Ohm cathode resistor. About 300V DC out of the rectifier with no power tubes installed, but that voltage is pulled way down to around 240V once the tubes go in. Each tube plate dissipation comes...

I can only access TAG using my iPad, which does not seem to have the malware site-blocking configuration. I cannot even get here on my computer, let alone log-in and post.....

Ah....got it now......thanks RJ.

RJ, I may be out-of-the-loop on this, but I don't seem to have quite enough info to track along.......I am not sure if the intent is for folks to *get* the circuit just from the photos......but I am not at that level. I was curious in particular about that attenuator? I can see the rheostat in your ...

Blackburn wrote:Love the fishbowl windows!.....

I second that......I has not thought about doing round side cut-outs like that before, but now that I see them, I thinknthey look great!

RJ Guitars wrote: .....One other factor to look at when you review my test results is that when you subtract out the cosmetic factor, MM and and Edcor drop more than the others.

RJ,

Can you explain this comment a bit more? *What* is being "dropped" by the MM and Edcor trannies?

Paul

Matt, Thanks for the additional thoughts. It may not be entirely fair to cite my lack-of-love for the DC30 circuit as being representative of all DC30s, as it was a Ceriatone kit and there may have been deviations from what was intended from Matchless. It is also simply possible that there was some ...

RJ,

I am not following that HUGE hole in the chassis......3 pre-amp tube holes, yes.......4 power tube holes, yes.......but then the rectifier hole looks like you could put your fist through it?

I am missing something?

Paul

Delete duplicate post.

4 el84 sounds better and isn't that much louder than two. As a point of reference, the Ceriatone "Rock It" kit has a half power switch -- so operated by dropping out two power tubes and adjusting the cathode resistor value accordingly. Having heard this mod played in both the full power and half po...