Hot Rod Deluxe reverb tank spec question

[glebert]

Nope, I did screw up, but not the way Enzo thought. Will post better description later.

[nevetslab]

I don't recall running into the R34 issues on the HR series Reverb Drive circuit. I have seen both the 4EB3C1B and 4BB3C1B tanks in use, as well as the Accutronics/Beltron 050394 tanks. I'd have to dig thru my notes on that #050394 to see if it's a 150 ohm or 600 ohm input Z. In either case, it's probably the low signal drive level that lets the TL072 get away with driving that low of an input impedance.

Looking at the Output Voltage swing vs load resistance graph on a TL072, it's capable of around +/- 4V @ 150 ohms and around +/- 9V at 600 ohms.

[glebert]

I don't recall running into the R34 issues on the HR series Reverb Drive circuit. I have seen both the 4EB3C1B and 4BB3C1B tanks in use, as well as the Accutronics/Beltron 050394 tanks. I'd have to dog thru my notes on that #050394 to see if it's a 150 ohm or 600 ohm input Z. In either case, it's probably the low signal drive level that lets the TL072 get away with driving that low of an input impedance.

Looking at the Output Voltage swing vs load resistance graph on a TL072, it's capable of around +/- 4V @ 150 ohms and around +/- 9V at 600 ohms.

I actually just totally bonked the measurement. Classic case of having a theory and then my brain trying to find data that supports it. Too many dumb things to chronicle.

Looking at other Fender amps that use the same reverb drive recovery circuit it seems like the drive levels for the HR series is much higher. In my screwed up experiment I ended up reducing the drive level to the amp and I think that is why I like it better. I may start a new thread on that just because this one is basically so full of hare brained thoughts to salvage.