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In Reply to: RE: Don't think so posted by Tre' on May 07, 2024 at 16:26:29
I think a bit more specification is required. Such as defining the amount of loss between 20 Hz power output and that which can be delivered at say, 2000 Hz. That if you want a real answer to your question anyway... LOLA2 will of course be just like A1 in the need to balance the idle current in between minimum and maximum. The extension of the maximum is no magic in the power output.
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
Edits: 05/08/24Follow Ups:
"defining the amount of loss between 20 Hz power output and that which can be delivered at say, 2000 Hz."Can we start with no loss (due to lack of primary inductance)?
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 05/08/24
Only with a large pile of primary L.
Seems we are talking about what is possible, so how much response at 20 or 30 cps is left compared to low-midband? Seems to me the question would be for say, -3 dB at 20 cps compared to something like a 1000 cps output, could be a part of determining just how much primary L is needed.
Once you have figured out what you need, then you can try figuring out how to go about getting it. Soooo, picking that 10k number for convenience, and putting down 30W at its -3dB point at 20 cps, how much are you going to need? Then at the same time, confirm the AC flux does not push you over the edge either...LOL
I will stick with PP for my A2 amp. Effectively a zero bias one. An S265 should do just fine for the power output a pair of DHT's with 65W plates can deliver. Off to get a small handful of P-channel, lateral MOSFET's to drive the cathodes with( source followers ). If I get totally nuts I will do voltage amplification and phase splitting with a pair of HY40's. That amp will have a lot of 7.5V running around heating cathodes.
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
I was trying to understand what is considered acceptable response at 20Hz and how much inductance is needed to get that in a single ended amp.Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 05/08/24
well... FWIW here is what spice says.
the basics are 10K OT 211 operating at 1kV -45V bias and around 90ma and inductance is stepped 40, 80 and 160Hy for both 20Hz and 50Hz.
The third "penne" plot has 40Hy of inductance and combination of 20Hz and 1000Hz each at -6dB as the excitation source. This appears to encompass an envelope a lot closer to the 50Hz one than the 20Hz one which is in line with what Partridge claimed was the realistic lowest frequency of interest for music.
personally i would be fine with 40Hy in this case with music being the source.
dave
That operating point (1000v/90mA/10K load) is more suited to A2 operation; in A1 as shown it only make about 8 watts.
.
Have Fun and Enjoy the Music
"Still Working the Problem"
I measured the low frequency -1dB point for the FS-100 (driven by a 211) at 19Hz. I've never measured the inductance of these transformers though. Whatever it is, core flux degrades it considerably when output is increased above a few watts.
.
Have Fun and Enjoy the Music
"Still Working the Problem"
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