The Amp Garage

Ok, just to make sure I got that right: 1. I connect a dummy load to the speaker output. 2. I connect both multimeter probes to the power tubes' cathodes (one probe for each tube pair). Do I actually have to connect the cathodes in each pair or is the 1 ohm resistance small enough that it doesn't m...

How am I supposed to adjust the power stage output to 50% when I inject the signal into the power amp through the FX return? After the master pot there is no other control that would allow me to dump the input signal down. Am I supposed to lower the output of the signal generator itself until I onl...

Three questions: 1. Power amp input = the point right before the .02uF cap right after the master volume output? Top of the MV pot, or if you have an FX loop, the return/power amp in is an option. 2. I don't really get point 3 (see picture). Where am I supposed to set the output level? You must hav...

Seller is putting the Dumble name on products. Could be a problem.

I would take the time to get this one working. You are probably not far away, and you will probably learn something. Then you can decide if you want to rebuild it or just go through it and tidy things up, maybe replacing some parts.

Placed a Mouser order today. Most line items are showing an estimated tariff of 10-30%. Overall the hit is 15% of the order total. :^\

Looks like the site is being attacked again.

Did the brightness improve? Is the reduced gain a deal breaker for this mod?

Looks like your HV input lead is coming from the DC side of a safety silicon diode. It needs to be connected directly to the HV AC.

A new feature I've been tinkering with for the past few days... Dumping out coordinates at data sheet reference Vg2 for plotting measured data or design values on the factory curves. Retro engineering ;^)

This is from my Excel load line plotter. Looks like you are ok given the reduced voltages at high power conditions.

Make sure all grounds are good, including all hacks and pots have clean and solid connection to the chassis. Many times simply tightening all pots and jacks can eliminate a lot of noise. The other prime suspects are carbon comp resistors, especially plate loads.

Have you checked voltages on the uTracer? You should have +/-15, +5, and -40 Here are my notes for getting uTracerJS up and running: The Home directory “martinmanning” has a folder called uTracerJS, containing the following: 1) uTracerJS-macos-arm64 (executable) 2) uTracerJS.txt (two lines that iden...

If the ripple gets too high, it will show up in the audio. Common mode cancellation is imperfect.

I prefer this circuit: https://ampgarage.com/forum/viewtopic.p ... 77#p476377
It is fail safe, and preserves its ripple filtering ability even if the bias is set to the most negative value. In that case the circuit above will parallel C1 and C2.