The Amp Garage

I just discovered that the little circuit I've been hot to work up on the bench, is in actuality, a rehash of a horizontal sweep oscillator. Mid 50's TV.
Bettie White's hot fuzz,...

I had a couple fender champs to scab around with before I started to fabricate rigs at home. I was out and about to jams and open mikes and had the perfect test conditions to keep going after it. Any little SE kit is convenient as hell. When I got going on it I had to accumulate a bone pile old tube...

There's this company, Devilwatt, they make piezo generators for stove tops and wood stoves, it is possible. Cram the stove full and jam a bit,...

I resorted to rigging this "odjet d'art" to keep at it off grid thru these, and the hard times comin'. Most fabrication can continue with intermittent power or hand tools but dressing a circuit requires an iron or course, and a bit more electrical demand than a solar/battery rig can provide. And,......

There used to be metal type calibration tubes, keep your eyes out for those, a calibration set is a pretty penny. The grounding pin on metal pentodes , 6sj7 can be very useful. They can be microphonic and NOS can be leaky . But every now and again I've found strong and nice sounding metal types, I a...

Thank you... You are correct, double checked PT and the design max for the tube type. Most common guitar PT do indeed land around 400v to 450v ish. And to make it go for the suggested tube type, looks to be 300v to 350v ish. I do have a PT in an old Mil. R-361/gr receiver that should give around 330...

I want to try a single ended headphone amp. So... it means 2 se amps (stereo) on a shared power supply, driving a 32ohm load. I have deluxe sized PT, looks like it will be enough for a pair of 6v6,.. or 6f6, even 6k6 ,... and I have a tub of 6v6 and even a pair or two of the later. The OPT I'm eyein...

Ummm... the other way around. I was noodling with 6sn7 and paraphase inverter, but ended up finding a happy place with 6sl7. The only way to add a pentode pre to it and keep the gain structure post, is to dump the gain pre. I was thinking to use an attenuator to pad the signal but it was more intere...

I'm contemplating using 6sj7, 6au6 and the ilk with higher gain paraphrase inverters, and looking the RC tables, relative to voltage gains of 12ax7, I really just don't need all that gain. Funny thing, saying that you don't want a lot of gain in a guitar rig. Looking at the various RC tables, it loo...

Under static conditions, both valves ( or several ), G1 or K tied and at same bias , G2 ( screens ) tied and at the same voltage, you can measure the V diff. between the G2 and P with a multi-meter as a quick matching check under what ever voltage condition you desire. The assumption for push-pull i...

I had a good haul from a junk pile find. It is about a bushel of ham/CB 7 pin mini, mostly RF pentodes and pentagrid and other various bench remains. And, a practical pile of AF tubes. I'm looking to rig a small combo using the following ,...6at6---6j6---6aq5. 6at6 is a single triode 6sl7, with an a...

Scrounged drier element.

I keep a bone yard of junk electronics for exactly that purpose, purchasing them seems silly.

Adding a bypass cap to the second 12ax7 stage, or the first 12bh7 stage should brighten it up, experiment, doesn't have to be a large value... .5 to 5 uF. You might change the first gain stage from zero bias to cathode bias as well. Nice to see 12bh7 as a SE amp.

I would set the bias a little too high (cold) and check static voltage conditions. First without the power tubes installed, looking for odd voltages, and then with the power tubes... could be a physical or component issue but it could also be a poor matching of the power tubes, bad tube or even a lo...