Mismatch load on porpoise

[Reeltarded]

Oh yeah they are UL.. I have never liked the stiffness in the other small amps you mentioned. Not my kind of thing.

I wonder. So much different about the Zodiac. Good catch..

All the rest you say is absolutely true. Start out with a supernova and waste it somewhere before the speakers!

[matt h]

(deleted)

[pdf64]

Just to note that as the p-p load impedance is increased, plate dissipation tends to decrease but screen grid dissipation tends to increase.
So for an AB amp with double the regular p-p impedance, the plates may tolerate being run a little hotter, eg if the VB+ is reasonable then maybe bias to 80%.
But also consider the extra stress tipped on to screen grids, eg add some resistance to the screen supply (eg 470 in series with the choke) or increase the screen grid resistor value (eg 2k2).

Regarding UL/DL, as mentioned, most all the well regarded instrument amps have saggy B+ supplies, eg tube rectified, Pi filter prior to OT CT.
Whereas the B+ of those late 70s Fenders was very high and stiff.

Bear in mind that for a heavily overdriven amp, flipping the global feedback on/off doesn't seem to make much difference.
This is probably because the negative feedback can't do much once the output is pushed beyond the clipping point. Whereas UL/DL may always be in play, even when clipped, due to the OT taps forcing a voltage ratio between the plate and screen grids?
It would be difficult to test that idea though, as flipping a pentode / UL switch on a cranked amp (or even just an operational amp) may cause a problem.

[Reeltarded]

haha yes not something I would be comfortable with unless I flipped the switch with a 10' pole and wearing gun mufflers!



I settled in the middle of bias and the amp roars. it's my superfantastic. I would have kept playing so much for all those years if I knew this was coming!