Tube Amp Archive

Another perspective on the 20K resistor to ground after the series field coil as filter choke. It has a more important function than just a bleeder resistor or dropping excessive plate voltage as is sometimes suggested. But wait, the older version with 6N6 power tubes has a 6K resistor to ground bet...

I see people on antique radio forums who do some really weird stuff to avoid spending money and get something sort of working. Or a antique part isn't available. One was to alter an IT PI with an open primary by disconnecting it, feeding DC through a resistor, and coupling the driver output through ...

If you can't sleep, read this. If you don't like science experiments, your choice. I think I will go find a post that actually refers to the T-8780 or -8790 IT PI and post what I just recorded. (This looks like the best one). The BR-3 schematic looks enough like the others to make me assume they use...

I think I will go find a post that actually refers to the T-8780 or -8790 IT PI and post what I just recorded. The BR-3 schematic looks enough like the others to make me assume they used the same interstage transformer phase inverter the other models did. But Mercury mentions both Gibson transformer...

I bought some black furry (single-sided) polyester fleece from my local Jo-Ann store a couple weeks ago to mod a guitar case after asking Gator what they recommended.

I found a Gibson schematic for an EH-160, the AC/DC lower-powered variant of EH-150, with capacitor-coupling to the IT PI, and a 100k resistor feeding the B+ to the IT PI driver tube but versions of BR-3, BR-9 & early EH-100 & EH-150 had driver B+ fed through the IT. They all appear in the 116-schem...

I find myself back here talking to myself again. I paid $108 minus a 10% (?) holiday coupon from Mercury + expensive shipping. I think the net was $118 delivered. That may be offensive in comparison to lesser IT's (that apparently do not work), but it's cheap for an EH-150-III compared to what Mercu...

1936 and 1942 Radio's Master Encyclopedia told me about the Jensen C12-R speaker. Field coil resistances as high as 11500 ohms were catalog items, but any value 'could be accommodated on request' The A-12 and B-12 were higher power speakers, both in voice coil power rating and field coil power being...

J.R. Someone on an antique radio site told me 'definitely' a Jensen. Also found that it was from a Coronado 2CM floor radio that could have three 12" speakers, per the service manual, which shows it as also being sold as Wells-Gardner, maybe also Western Auto, and sold at Monkey Ward's. The service ...

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I am looking at Gibson amp schematics that use the T-8790 interstage transformer phase splitter. I see it in an EH-150 'Style III', an EH-100, and once in an EH-125, which I cannot find tonight. I found a BR- amp (probably 3) amp with a IT, but this post shows T-1001D for the BR- amp. Or was it for ...

I wonder if 40 mA continuous is too much for a 6AL5. Probably OK for a 6X4. Datasheet spec number vs. datasheet graphs say different things...or I read different things.