High voltage driver for AB2 operation GU81m tubes

[Alexontherocks]

Thanks! I really appreciate the encouragement!

Actually work is progressing much more slowly than I would like. What really helps is to think things over and over...really imagine the assembly in every aspect before even touching the screwdriver. This way when the time comes to build, every forseen problem is addressed swiftly (obviously there is a margin for error). I think the amp will work well. In any case the driver section can be redesigned and swapped for something better in a very short amount of time. I am eager to test the power section. Once that is done it will just a matter of starting the testing phase.

I think the bass response will be really exceptional. Many have described music played by large tubes as "effortless". can't wait to corroborate this idea!

[Tony]

go slow...haste makes waste...are you affected by the earthquake?

[Alexontherocks]

here is the video

http://youtu.be/F8Jh4s9j9rk

the filaments are sofstarted via a 4A 10ohm NTC thermistor....the main switch triggers the timer which in turn activates the softsart module. This will force the surge to flow through 4x NTC thermistors. After 1.2s the thermistors are bypassed by a relay.

[Alexontherocks]

Originally Posted by Tony

go slow...haste makes waste...are you affected by the earthquake?

Very true. The best part is yet to come...for now it is just boring mechanical work. I still have to wait for the sockets to be sandblasted and powdercoated.

Thanks for the question. Very kind of you. Luckily no I live in the least sismic area of Italy and just felt the smallest amount of tremors. At 9 o'clock yesterday the tremor was noticeable but not cause for concern.

The amp is so heavy I was pretty confident nothing could happen.

[Alexontherocks]

burning tubes...

all filament transformers in the amplifier are connected to mains via a NTC thermistor (CL-60) 10ohm @ 25°C

Only the rectifier filaments do not draw enough power to lower the thermistor's resistance to an acceptable value...therefore with only the rectifiers on I get 2.1v instead of 2.5v.

I hope this will solve itself when the gu81m filament transformer will draw its own current.

for now...some burn in tests

xenon


mercury



If anyone has any suggestions for ux4 compatibile rectifiers I am all ears (no pun intended). This will be a great testing platform for future experiments

[Alexontherocks]

Also a question...

I want to move inputs and outputs to the front of the amplifier


the front plate is 10mm thick. I can get away with it as far as the outputs (since the threaded connectors are very very long) but input s going to be a problem. Can anyone point out a connector, with a round footprint, which will mount on a 10mm thick panel? I thought of 6,3mm jack or RCA but both seem too short.

[Alexontherocks]

voltage boards fitted



need to dremel out a pice to allow for the bank of b+ caps.

[Alexontherocks]

unfortunately I have very little time to post this picture...so let us say somethings work, other don't

[djn]

Wow, looks like the Genie is about to jump out of the bottle. Kind of a cool picture though.

[7N7]

Originally Posted by Alexontherocks

Also a question...

I want to move inputs and outputs to the front of the amplifier


the front plate is 10mm thick. I can get away with it as far as the outputs (since the threaded connectors are very very long) but input s going to be a problem. Can anyone point out a connector, with a round footprint, which will mount on a 10mm thick panel? I thought of 6,3mm jack or RCA but both seem too short.

Is the front panel removable?

If so what you need is a counterbore. A counterbore is a drill - for example that begins as say a 6mm drill further along it becomes like an end-milling cutter, so you might have say a 6mm pilot hole followed by a 22mm flat cut. With care this would enable you to reduce the thickness of your panel where needed,

Paul