audio-talk

Hi Nick Sometimes the best way to learn a lesson is the hard way. You have to hand it to Bruce Rozenblit though, He really does seem to have made an OTL that is user friendly and does not blow up your speakers. If a numpty like me can build one of his designs without blowing himself up then it must ...

Well I've had it up and running on four valves and it sounds very nice indeed. liquid and smooth like you wouldn't believe. The top end is simply beautiful. There is not much power with the four valves but it is extremely neutral sounding, totally different to single ended with output transformers. ...

Well I cured it but I have lost two valves in the process. One shorted grid to cathode and destroyed itself. Its partner on the bank now has an open heater. It was a bad B+ decoupling cap in the end which I found by removing them until the noise stopped, plus of course the feedback miswire. The driv...

Right. Inserting the HT fuses one at a time. The negative rail on its own has just the normal hum that would cancel out if the other side was on. The positive rail on its own however sounds like a buzz saw rattling around in a bag of spanners. So It is now isolated to something in the positive side ...

Nick:

You have a PM
Steve

I'm not holding my breath. Steve PS that's the problem with this higher power game. When these amps fail they make a much more scary noise and generate much bigger bangs. Told you I wasn't holding my breath. It still motorboats but without the accompanying blatting noise on top of it. That's one fa...

Hi Colin
That looks fantastic.

Strange how these new amps of yours and mine are having such a painful birth. What with my amp's impression of a canal barge and your Tent Labs heater supply failure.

Have your results so far been worth it.?

Steve.

Something else as well now I've had a sleep. The way I have the cap connected will bypass the cathode resistors to ground, which will substantially increase the gain of the first stage. The first stage is a 12AX7 high gain valve which makes the relative increase the worst case scenario as there aren...

Hi Nick Couldn't leave it alone as it was nagging at me. So I had a nice cup of tea, said my relaxation mantra and armed with the circuit diagram and a very strong pair of reading glasses I found this http://homepage.mac.com/scress1958/.Pictures/oops.gif What is this going to do to the feedback? I a...

Thanks Nick I might just do that. I know you managed to sort Simon's Blatting 2A3. after he got completely stumped as I seem to be. I don't yet know why and I'm leaving it for tonight but there seems to be -6v of feedback coming along the left channel but only 1.5V coming back down the right. Could ...

Paul
you have two PMs

Oh dear, Here we bloody go again! I'm giving up with this neatness lark. It's clip leads and rat's nests from hereon in. So what seems to be the trouble then? Right. The HT to the output stage is isolated by fuses which are removed whilst the checkout is in progress. So far so good. Everything check...

Hi. There have been anumber of developments with the Metronome speaker Martin King has come up with a proper baffle step correction circuit for the Metronome FE108EZ version. He visited Jim Shearer in New York, who had just completed a pair of the FE108EZ speakers http://www.diyaudio.com/forums/show...

That's it! Apart from wiring in the input cables to the selector switch the OTL is completed. It has been powered up and tested without the valves, just to check that the right voltages are appearing in the right places, and with the right polarities. One fault was found with the left channel bias v...

The job is nearing completion now. Here are a few pics of the progress made over the past couple of days. http://homepage.mac.com/scress1958/.Pictures/OTLtxs.jpg On go the four transformers. The Sowter at the rear has two HT windings for the driver and output stages. Next size down is the heater tra...