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mosfetmaniac 10th April 2012 08:21 AM

834 Triode amp
I have some 834 Transimtter tubes which I *was* keeping to build an amp with at one stage, however I can't seem to find anything, anywhere, in relation to these being used as an audio amp. :confused:
If anyone has some info it would be very much appreciated :)

mark6699331 18th January 2013 07:29 AM

I saw one guy on ebay selling these tubes I talked to who built an amp. They are very similar to a vt-62 or relative of the type 10 amp but higher voltage and different bias.
He said he only heard one tube sound better than this one in a S.E. triode configuration.
That was a rare Eimac tube. He also said this tube if done right BLOWS away western electric triodes like the 300B.
Unfortunately he's a DIY type person and didn't have a schematic. He did send me pictures of his amp on top and underneath but no values. It looked like one tube to drive it, an interstage transformer and then an OPT and that's it. Very simple. He wouldn't give me details as to the B+ and how he got it to class A, and all the stuff I really needed. i'll try to find the pics and post them on here and maybe someone can help us figure this one out. They are really cool looking tubes with those two anodes sticking out the top of the big glass bulb. I couldn't believe those small plates could handle 1250Volts on them in Class C!!! and put out 50watts class C per tube.
I'd do anything short of dying to get a schematic or project going to build a pair of monoblocks of these or even an integrated as the heater and mains supply are going to be unusual votages. I just bought 6 tubes/3 matched pairs. If you find anything else out please post here. Perhaps somebody good at DIY will be able to help us out.
Mark :)

rotaspec 18th January 2013 06:09 PM

I too have a large stash of these sitting waiting for the day I have enough knowledge to design a big amp from scratch. The downside of these tubes is that they are prone to the air seals failing, so gassy tubes are common. The other thing is that they have to be run with heatsinking caps on the plate and grid posts. They do look good fired up on the tester.
A quick look at the curves shows that there would be a good starting point for class A at around 750v and 40mA into a quite high SE load. Again a possible starting point would be 10k.
Another possibility if you want higher power output, is A2 operation, but that is beyond my skill level at the moment.


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