... now that i've converted to 5F6A, the amp does not get real loud. ... just tonite I swapped speaker loads, the tweed is very loud on three, the SR 5F6A goes to 8 to equal.
Was the amp's volume right when it was the Super Reverb circuit? I can't speak to replacement OT's, but I used to own a blackface Super Reverb and can tell you it is every bit as loud as the 5F6A.
More important to the evaluation of volume: are both amps roughly the same audible volume when they start to distort? This is not an issue of volume knob setting; does essentially a similar volume come from the speakers?
The 2 amps have different circuits, but similar output stages. They should create essentially the same clean volume output, given the same output number and type of tubes, same number of speakers and similar phase inverter and feedback. But the placement of the tone circuit and the fact that it is driven by a cathode follower in the 5F6A leads to somewhat less loss in the tweed circuit's preamp.
That could account for some discrepancy of volume knob setting. Another would be the type of pots used. What kind of pots are in each amp? Are they different? If you have a linear-taper pot for a volume control, almost all the volume change will seem to occur up to about 3 on the knob. From 3 to 10 (12?), there will be almost no volume change, but possibly only a distortion change. If you use a log pot, the volume will seem to change smoothly and "linearly" from 0 to 10. Yeah, it's hard to remember that a log pot will do this, because the name is different from the effect, unless you remember that human hearing responds logarithmically.
But there is more than just 1 kind of log pot. Most that you come across are 10% taper. Measure the resistance between the outside lugs, then rotate the wiper up halfway and measure from the center lug to the ground lug. You will read about 10% of the total resistance at 50% rotation. A linear pot will show 50% resistance for 50% rotation.
Some manufacturers use a 30% taper log pot. The resistance increases faster, and gives 30% resistance at 50% rotation. The effect is that the amp is louder on 2-3 than another amp with a 10% taper on 5-6. Because the taper is faster, the voltage is divided differently and the volume rises in a hurry. But at the top end of the rotation, there is very little volume change, and it can even seem like the amp runs out of "headroom" as some folks say. It really has nothing to do with the circuit performance, only the pot taper.
Come to think of it, I have a tweed Deluxe copy that has, I think, 30% taper pots. I'll have to go in and swap them out for 10% taper pots. Tweed Deluxes distort early on the volume knob, but I might get some wiggle room with a part change. The WeberVST pots are 30% taper. Others, you'll have to check a distributor with full info in a catalog or webpage (like Mouser, Newark, Digikey, etc) to see what the specified taper is.
Topic: Repro Output Xfrmr wound for less output? (Read 4360 times)