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Old 30th March 2010, 07:18 PM   #1
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Default GU-50 PP amp project - Any favs?

A while back I bought a bunch of these tubes and sockets and put them aside awaiting time and motivation to use them. I am now at a point where I'd like to put them to use. I'd like to build a PP amp preferably using octal support tubes. I've done a bit of searching here and on Google and found a few interesting things but none yet that scream "build me". I've also looked at a few classic KT88 designs to possibly modify. I figured it would be best to post here before I get to far along and get some input from people with experience with these.
Does anyone have any sage advice or any favorite PP amp designs for these?

Thanks,
Dave
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Old 30th March 2010, 08:12 PM   #2
AuroraB is offline AuroraB  Norway
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Maybe if you use Google or Babel to translate this....unless you read german?
I do, and this looks like a well worked project, but that's all I know about it, except the designer seems to have a name in Germany....

Gegentakt-Verstärker in AB-Betrieb fuer GU 50
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Old 30th March 2010, 11:03 PM   #3
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First of all, you need to think about output and power transformers, before thinking about octal tubes. GU-50 amp needs 8K P-P tranny capable of 100 Watt on rated bandwidth. It is not so easy to get good transformers with such parameters.

Also, you will need 12V 4A for filaments, 250-300V for screen grids and 700-900V for plates.

Are you scared already?
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Last edited by Wavebourn; 30th March 2010 at 11:25 PM. Reason: typo corrected
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Old 30th March 2010, 11:09 PM   #4
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Not scared at all. I've been building and repairing tube stuff since I was 14 (mid 1960's). I grew up with this stuff. My Dad was general manager of Grommes and started there as an engineer their originally. Now I'm a retired engineer

Thanks,
Dave
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Old 30th March 2010, 11:24 PM   #5
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I did not mean high voltages; I meant very unusual transformers.

GU-50 sound like a charm in my amps. I don't have a complete schematic drawn, they have almost directly coupled drivers with servo, parallel feedback by voltage across output tubes, and regulated voltages for screen grids and drivers.

www.wavebourn.com • View topic - Pyramid-VII: home stereo vacuum tube amp
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Old 31st March 2010, 03:39 PM   #6
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Try this one:
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Wavebourn: What do you think about this one. Maybe you could help us figure out how to make these transformers (for US) or better yet separate them (power xfmrs) into several smaller (modular type psu).?? I KNOW you've the skill and talent for it!!! Or use it as a launching platform for a different design here... maybe even group buy project? OHHHHHHHHHHHHHH, GU-50 OTLs.... now that's to drool for!!
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Old 31st March 2010, 04:03 PM   #7
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I ordered my transformers from EDCOR Electronics Corporation

I can draw full schematic of my Pyramid-VII, but I'm short of time currently. I even wanted to write an article for Elektor magazine about it, probably I will do that later.
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Old 31st March 2010, 04:03 PM   #8
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Quote:
Originally Posted by AuroraB View Post
Maybe if you use Google or Babel to translate this....unless you read german?
I do, and this looks like a well worked project, but that's all I know about it, except the designer seems to have a name in Germany....

Gegentakt-Verstärker in AB-Betrieb fuer GU 50

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