The Amp Garage

I probably would look for something like this Hammond output transformer. https://www.hammfg.com/part/1628SEA If you disagree that’s fine, but I would like to know why. It is touted as a Hi Fi transformer, but I don’t like Class A amp with rubbish bass response generally. From my experience this tra...

Measure the leakage at rated DCV. Measure the ESR. Measure the capacitance. Look for deformities. Fairly simple, but it takes time. It can be done by lifting one leg with care, and can be done using the amp's power supply when you have a variac and use a series resistor for current sensing. Right, ...

]The Two Stroke seems a strange amp to me. The tone control on these amps is nice but it does mean the amp loses signal so it doesn’t have the same break up as a Champ. I don’t know why the second 1.5K cathode resistor wasn’t bypassed by a 5uF to 22uF cap for extra gain and a 47 ohm tail resistor pu...

It’s not a question I thought I would be asking but here I am. I use the ESR-70 to determine the condition of the filter caps. I have mentioned this online and been roundly told this tester won’t determine if the cap is leaky and I should simply replace the caps. I tend to think if the cap was leaky...

That master volume mod doesn't actually help, I did some tests on this a few years ago with a spectrum analyser and found it made no difference. But YMMV. Dave Friedman puts a 500pF cap across the cathode follower 100K, lowers the first coupling cap to .0022uF, adds a 22uF to the final stage cathod...

Mystery double post.

bepone wrote: ↑Sat Apr 13, 2024 1:50 pm Speaker is v30? Change the speaker?
Some other guitar problem?

I used a EVH MIM guitar, and I also used my Strat. The box is a Fender Bassman box with Kendrick Blackframe speakers in it. I have previously used the box with a 1959 and it sounded fine. The speakers aren’t overly bright.

I plugged into my friends 2203 and it sounded dreadful. It was overly compressed and the treble is raspy. The compression was due to the 100K cathode follower resistor measuring 880K. I replaced it and the amp sounded much better. The amp still has raspiness which goes away when I turn the volume up...

Thanks for your advice I appreciate that.

I’m working on a JCM-800 and I find that the bias voltage ranges from -58VDc to -42VDC. I have tried the EL-34’s that the amp came in with and a new set. I find with a new Marshall branded set if EL-34’s the maximum they will pull is 27mA. The bias circuit is incredibly simple. A diode, two resistor...

[Franchesca (Express "85") had Clarostat PC style pots throughout where both Ingrid (Express "92") and the Liverpool from Funks images have a mix of Clarostat, PEC and Mil-spec AB's but in similar layouts. The 1megs used for volume appear different than those used for treble etc. I would be interes...

Malou is a very interesting example. The pots themselves are a great source of consideration for me as they each appear to have been selected for a reason. Either that or they were just sourced from a box of various pots! I know that Marshall used the "hot shield" regularly in their cascaded amps i...

Did you try the vintage/fast switch. That reduces the output from the second stage. I tried a few of those sorts of things over the years. To be honest I can't remember exactly the values I played with in that spot but I did have a switch on it. I think I mostly put the preamp back to stock now... ...

Yes those photos were on Dave funks website maybe thunderfunk.com but cant seem to find it. Dave was a authorized Trainwreck repair shop and after ken passed Dave decided to spill the beans that he had built Trainwrecks for ken. Would send ken the chassis and ken would tweak them, serial them, head...

Interesting that Funk would have been involved in the Liverpool with the extra cap and 10 turn variable resistor. I wonder which amp that is and whether it is one of the more known or not. Also wonder if there was just a great deal of Mil-spec pots in stock for the Mids or if there was something ab...