Recent content by Jesco

My early 60’s Alamo Challenger (essentially a grid-leak biased 5F2a) has a conjunctive filter in the circuit.

My 5F2A has a 4ohm 12A125A in a 5e3 sized cab. It sounds fantastic. I haven’t tried any other speakers with that build, but it really feels like a great fit for that amp.

This is how I do it on a PR. I also run a wire from the power supply ground to the pre-amp bus ground to create a single point grounding scheme attached to the chassis at the input.

As a proud owner of a quiet torevibe, all I can say is “hell yes”! Well done.

That’s exactly what I was thinking. I had the dropping plate voltage scenario happen on a fixed bias amp where the grid leak resistors had not been grounded. Something worth investigating.

Learning opportunity for me! I don’t understand the above statement. They way I’m looking at it, if you connect the heater line center tap to the cathode of a cathode follower triode stage, you would be shunting 3.15 VAC into the signal path. What am I missing?

I believe that wouldn’t work because the cathode of the cathode follower is the audio signal path. You would be putting AC heater noise into the signal path.

This is what I did in my Revibe build. The grounding scheme as suggested by tubeswell will work great. It looks like he’s following Jeff Gehring’s example of running individual ground wires back to a buss bar. In my revibe build, I connected grounds together by filter cap (ala Blencowe’s...

In a cathode biased amp, yes. In a fixed biased amp, no.

it looks like the cathodes of two power tubes (I assume 6V6) are tied together to an unbypasssed resistor. There appear to be two preamp tubes, two power tubes and a tube rectifier.

No build thread. This was a custom order amp I built for someone recently. After I built it, there was intermittent hum, specifically when turning up the reverb. Initially, I was worried about the reverb tank, and was able to change the level of hum by moving it around. However, in the end, it...

I just finished a 22 watt Princeton Reverb in a head. The head is not particularly high. It is as quiet as you could want. I’ll add a pic so you can see the size. I think it is maybe 9”s high? So I wouldn’t automatically assume a problem with reverb tank being too close to the chassis. I had...

It sounds like you’re narrowing it down to the input circuit. If you’re getting noise when you chopstick pin seven and eight of the one, don’t ignore that. That could indicate a bad tube, or cold solder joints at those connections. The first thing I would check is to make sure that the...

Not particularly. Some manufacturers user 18 gauge for heaters, but others use thinner wire. Coaxial wire is shielded, so it shields the signal from noise. Usually folks put the 68k resistors right on the Jacks and then run the coaxial wire to V1A grid. You’ll find pics of this online. It’s...

The preamp tubes in the 6G2 are 12AX7s. You can just substitute 6SL7’s without making any changes.