Very interesting remark (40-60 ohms) My actual project consist in 6c33c otl monoblocks and quad esl63 modifyed for 32 ohms. Last tests looked fine but the final test shall be the real listening.
Anny suggestions?
Actually unless you plan to change the operating points of the power tubes (including the B+) there's no advantage to impedances this high.
20-30 ohms works though and quite well. At impedances above about 20 ohms the full power output of the amp decreases.
that was a Garrard with local solid wood plinth while the tonearm is a linear tracker, locally designed and fabricated.....i think that was a hanna mc cartridge...
Maybe when your OTL settles down and you become more confident of it, you can "live dangerously" and remove the O/P caps. I ran my own OTL for about a week into a dummy load before connecting speakers. Now the O/P DC offset does not vary by more than +/- 6 milliVolts. So far, there have been no LS disasters. It takes courage though.
yes, i have my sights on that.....i just don't want another persons' speakers burn out.,....btw, those in the show did not know about the output caps...
the hever asled so i never told them....
I am running too, the mono-blocks since more than 10 month on the precious esl 63 and offset seams to be prety stable. I also face one ef86 damaged, but fuse done his job. On my humble oppinion output cups may alter the sound more than an OT.
if this were so, those who came to the show and listened were all smiles as they left the room....but i do believe that the amp will be better without the cap, just that safety of the speaker came in as first priority...
that esl 63 has a built in transformer if i am not mistaken...
Yes, you are right but is a doble step-up 250x so firework can rise if something is wrong.
Some pasionate guys consider OTL+OT step-up/step-doun an interesting option. That's why our project consist in otl/esl but the target is modifying the esl63 from 8 to 32 ohms. 6c33c shall feel better, rms power rise to 40-50 wats and PSU shall be less stressed.
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At the moment, I use my OTL to feed two Fostex FE126Es in a bi-amping setup. They were not very expensive and anyway I have two spares waiting for the day they are needed. The large bass unit is fed from a vintage Quad 405 Mark I. I cross over with a Behringer CX 2310 @ 350 Hz.
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I wonder sometimes about whether output capacitors would really be that beneficial in the event of a catastrophic tube failure. If the output voltage on the upper tube's cathode suddenly went to one or other of the B+ or B- rail voltages because of some failure condition, I could imagine the surge current through the speaker would be pretty massive even if there were a capacitor in series with the speaker coil. I could imagine the coil would get fried either way, with or without the series capacitor. Fuses hopefully take care of the situation anyway after a short time, but the initial surge before they can act is maybe the bigger risk.
Anyway, I just hope for the best with mine, and it's been OK so far, which is about 5 years with using the amplifier almost daily.
As to whether an output capacitor would affect the sound, since the power supply capacitors are in the audio path anyway, I wouldn't think there should be much difference to the sound either way, as long as the output capacitor is large enough.
Chris
the + rail fuse blows up ....i wouldn't make a big deal out of the output caps,
i will not even justify its use....
the output caps were used in early ss amps back in the day....
that is until they realised that the was not really necessary...
there are no turn on thumps either with this otl tube amp...
i will not even justify its use....
the output caps were used in early ss amps back in the day....
that is until they realised that the was not really necessary...
there are no turn on thumps either with this otl tube amp...
I'm using 1.5 Amp quick-blow fuses in the speaker O/Ps. A bit low maybe but then again, I'm pushing only a few Watts at the moment and they haven't blown yet. I'm not concerned with the ultra purist notion of non-linearity of fuses in the O/P chain; to me the idea of no O/P transformers in a tube power amp overrides most other considerations. Anyway My Tim Mellow OTL is now singing happily day in, day out.