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In Reply to: RE: Class A push-pull posted by Triode_Kingdom on December 07, 2024 at 16:04:17
I went all the way up to the 304TL with the 28 pound 1642SE hammond OPT and 1,200 volts @ 200mA. Bass is better even at low volumes, but not quite like the vice-like-grip of a PP amp. (8 ohm load on the 4 ohm secondary to raise the 5,000 ohm reflected load a bit.) Horn bass is just so physically massive. I am currently using a pair of 18" vented 97db bass speakers.
I do like percussive bass you can feel in your chest, however. I think musical choice changes the preferences.
Follow Ups:
"8 ohm load on the 4 ohm secondary to raise the 5,000 ohm reflected load..."
That effectively cuts the inductance in half raising the F3 an octave.
I did the same thing with the same OPT for a 211 build but I wasn't using it for bass.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
The inductance remains constant and the load doubles which is not critical when the tube being loaded is a triode. If you double the load and keep inductance constant with a triode, not much bad is going to happen. The belief that if you double the load, you must double the inductance stems from the use of a pentode as the tube which has an inherently high Rp making the reflected load work against the inductance to determine LF behavior. When the tube being loaded is a triode, the rP is typically 1/3 or less that of the reflected load so it dominates the impedance the inductance must work against.
I am not saying more inductance is not a good thing. Just that how you determine the required inductance is based on tube Rp for a triode and reflected load for a pentode.
dave
if you double the reflective impedance by up-tapping the OPT you need to double the inductance to keep the same relationship between the reflected impedance and the total load impedance as seen by the output tube.
and I should have left the F3 part out.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
While what you say is technically correct, it glosses over the basic idea that the inductance has more to do with the characteristics of the drive impedance and not the value of the reflected load.
Taken to the extreme by your argument, a plate choke would need infinite inductance to match the reflected load. So would a line out transformer driving the grid of a tube. This opens up the whole large signal vs small signal can of worms which simply confuses the underlying concept. I think we can all accept that for a given tube, the more current that needs to be delivered to the load, the more inductance is needed. The idea that doubling the load requires 2X the inductance puts far too much emphasis in a FOM that isn't universally applicable.
dave
.
Have Fun and Enjoy the Music
"Still Working the Problem"
figure of merit
.
Have Fun and Enjoy the Music
"Still Working the Problem"
"If you double the load and keep inductance constant with a triode, not much bad is going to happen."
It's not just about the tube and the load line. When the reflected load impedance increases, AC voltage across the transformer also goes up. That causes earlier saturation, particularly at low frequencies where core flux is greatest. And on the subject of triode VS pentode, it seems to me that NFB (required in the case of the pentode, but not the triode) levels the field when analyzing the source impedance seen by the transformer.
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