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In Reply to: RE: Alan Kimmel OTL posted by pickle on March 01, 2012 at 12:45:14
Hello,
for the Kimmel OTL I am very interested.
A simulation I made with LTspice.
At the 12AX7 tubes I have problems.
Up to the input of the 12AX7 everything is okay,
then the signal is broken.
Can anyone help me?
Best regards Steffen
Follow Ups:
I've built the Kimmel OTL; it works nicely, and seems comparable to other OTLs I've built.(Mine is a rather utilitarian construction, with no particular attempt at elegance!)
Chris
Edits: 01/18/14 01/18/14 01/19/14
Vary nice...........what output tube is that...an are these 12AX7 inputs??.............if so looks like a lot of gain...have fun with tubes OTL...
Input is 12AU7. The output tubes are JJ EL509S.
I just made the "lite" version, with four output tubes per channel. I wanted to fit the whole stereo amp onto one chassis, rather than two monoblocks each with a separate power supply chassis as in Alan Kimmel's original article. It is a bit of a squeeze, and there's an outboard fan at the back, and the heater toroidal transformer too, like a spare tyre on an SUV.
Chris
what power output do you feel your geting?......i two like the stereo with the one ground for the two chn... it can sound sweeter to me.....i have diyed a Tron OTL like that...an ran all the tube hearters off one tranX...i like the sound alot....thanks for the info...
tyu, I've never tried pushing it to the limits to measure the maximum output power it's capable of. In the original VTV article Alan Kimmel says the 8 tube version will give 210W rms into 8 ohms. There, he makes no mention of the output power with fewer output tubes. However, in another copy of the article I found on the internet, the specifications for a 6 tube and a 4 tube version are appended at the end. The claim there is 115W into 8 ohms for the 4 tube version. That sound somewhat high to me; roughly speaking, the maximum power should be limited by the current the output tubes can handle, and so with a halving of the number of tubes I'd have expected roughly one quarter of the power handling, not one half. My guess would be about 50W therefore, but as I say I've not felt inclined to push to the limits to measure it. I've measured up to about 25W rms into 8 ohms and stopped the experiment there.
Chris
I had a Melos two ch tube amp in the 90s......that had 4 EL509 in it ...the older tubes..... one with the plate on top....i still have some of the tubes here now i was going to put in a push-pull amp....only 4-5 of tubes....but i could never get the Melos amp setup.....how the hell can you get 200 watts out of two tubes
i sold the amp.... never sounded good.....but it had trodels output trax....at that time i was told the output trax were the prob....
But your amp may sound sweeter.....than the one with more EL504s
an less heat..........thats my prob....even the M60s i have to HOT..
i live with push pull amps an get great sound 50-60 wattes KT88s 6550s
an some mods....like the DC clamp on the output tubes that Bob Carvers uses in his amps....with a 5AL5 tube....i now have the tube amp sound i have been looking for for 40 year.... thanks for your time.
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