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In Reply to: RE: The comment on Tubecad posted by Ralph on April 22, 2017 at 15:25:39
Ralph, I was hoping you would answer this question. Thank you for the explanation and info, it answered a lot of question I had.
i saw that the Zero Autoformers were used with your amps. Are they as good as what I have seen written about them?
I have also been looking into your M-60 kit as well as the Transcendent. I currently have a Latino VTA-120 that I built from a kit and I'm happy with but I have been hearing good things about the OTL's for a while and now have the bug to build one. I was looking to do a Beast or the M-60 in kit form but this thing of proper speaker loads came up.
Thank you for the help.
Edits: 04/22/17Follow Ups:
I have written about this before, maybe many times. I modified my Sound Labs 845PX speakers, which in stock configuration had a nasty impedance dip at critical midrange frequencies, down to below 4 ohms, such that the impedance after the modifications is a fairly flat 20-30 ohms, from around 100Hz to 5kHz. Impedance falls gradually above 5kHz to 2 ohms at 20kHz (nearly unavoidable with a large ESL like mine, due to the capacitative nature of the speaker itself). In any case, the improvement in both speaker efficiency and in the capacity of my Atma-sphere MA240 amplifiers to drive them, and hence the pleasure factor, was nothing short of phenomenal and continues to gratify me every time I fire them up.
(Efficiency went up as a result of the mods independent of the fact that impedance went up, because the low impedance of the OEM configuration is in large part due to the fact that the crossover places a rather low value resistor, anywhere from 5 ohms to 10 ohms depending upon the year and model of the SL speaker, in parallel with the output of the amplifier. The resistor inevitably sucks amplifier power and converts it to useless heat. That resistor is now in the trash.)
I feel certain that any 50W tube amp would drive the modified SL speakers to ear-splitting levels with no strain.
They are a problem solver; when a person wants to use a low impedance load the ZEROs are often helpful for getting many amps to sound better on that load, even transistor amps.
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