The Amp Garage

I'd recommend using your 125 and not overthinking this. The working load from a reverb tank isn't going to tax that driver circuit. A 6AQ5 running below 150V is cruising. With the Hammond you can try a few different impedance options. The only notable changes will be in tone. Higher impedance should...

Champ transformer only has a fixed ratio. If you attach an 8 ohm tank then then you'll have nominal 10k ohm on the primary. FWIW the stock Fender reverb transformer is 22k8 ohm, but what Premier have spec'ed is mystery. That schematic has no notes on that.

Either will work. Hammond 125 has an advantage from multi-tap secondary. Both are a bit of overkill power-wise.

Hmm, that's more true for a higher gain amp. A bit more background. He has a few amps but none with an effects loop. This includes both a 6G12a Concert and a 6G15 'verb. He recently latched onto a tremolo-less 5E9-ish amp I built by modifying a Mission 5E3 kit. This is a relatively clean amp with a ...

Yup. Agree the skills of a hand surgeon or similar would be good when building a ReVibe. I do like that Hoffman variant. Basic reverb is pretty simple. Even the 6G15 is doable. What seems to me blowing it up is that 6G12 trem circuit. I was hoping someone has a pointer to a simpler tremolo based on ...

I know about Weber's "ReVibe" kit but wondering if the collective wisdom has better alternatives for building a standalone tremolo+reverb unit. Suggested options will need to be reasonably straightforward. As close to "paint by number" since it will be a first build by a friend. We want him to succe...

Or use a combo small signal pentode+triode tube designed for RF (TV etc) such as ECF80/6BL8. The pentode for gain and the triode as CF. Worked in Dynaco hifi designs as voltage gain plus cathodyne PI driver swinging a pair of EL34. Has more than enough to push a tone stack. Will require some fiddlin...

Hello - I took a run at this a while back. My eventual solution was to clone (with tweaks) the vibrato channel from ab763 Super Reverb and run that single-ended into a 6L6. I was after the sparkling clean Fender tone with something lighter and cheaper than a Twin or Super. It turned out well but was...

Grasping at what for me is the last straw --- disconnect the power bypass capacitor. Does no harm to remove but really unlikely it's causing a problem.

The only other thing I know of that might be pulling it up is super-hot screens. Earlier measurement suggest that's unlikely too.

Best ... Ian

The 24M ohm reading off the cap is OK. Probably just a meter issue.

Assuming the power tube are still simply disconnected? Floating grids are bad. They should be tied to ground, probably preferably just through that pair of 220K resistors that are missing in your photos.

Best ... Ian

Single conductor from the master. That shield is not helping anything and it probably is your low signal problem. OOOHHHHH ppimv. NIX IT kill that delete it. make the amp work then install it. I was thinking if a pair was going hot it was just an output coupler.. I disconnected the two preamp wires...

I had similar thoughts to Martin but given what I find on Edcor's site - the colours are those typically for UL screen tap so the 5K2 on a multi-primary - plus your resistance measurements have parked it. My suggestions are perhaps a short in the 40-20-20-20 multicap -- but usually that involves smo...

Hmm - Not exactly. I (very carefully) clip the load to ground and then B+1. But if you wanted to test upstream of the standby then clip to the positive (+) end of your first pair of power filter caps. I do this starting with the power off and filter caps checked they're fully drained. And then (very...

Hello - I keep a handful of 20W 10K ohm power resistors used to provide reasonably close dummy load when testing a repair or firing up a new amp. On an express or liverpool style a pair in parallel gives you 5K @ 20W, which is enough to pull down power rail from the center tap of the output primary....

Feedback will scrub some grit particularly in higher frequencies, which increases "clean" headroom. Cliff's comments were absolutely spot on about the benefits --- except that songwriter and rocket are both push-pull class AB (quad of el84). So experience/observations with single-ended class A amps ...