Gu50 output problems

[beamnet]

use an 6sn7 or two 6j5's

but i have plenty 7193-like valves for sale..

Bas

 

[adishor_2005]

2K for primary impedance isn't to low for Gu50, i know that the tube needs arround 5K.
have you made changes to the schematic after you solved the problems or the schematic is the final...
do you have a schematic for the power supply of the circuit???and for de output transformer

thanks

 

[Zibi]

http://www.tubefreak.de/
http://www.goldenmiddle.com/english/trans.htm

 

[beamnet]

There is no former there that would survive the gu-50

Im have used beard p-100 output formers.

The other link doesn' have a schem

I would advidse the schem i gave. It is simple as hell and allows for easy mods. i have ccs on the tail now and various other tweaks.

The ps:
schematic

Good luck!

 

[Zibi]

adishor_2005 wrote: 2K for primary impedance isn't to low for Gu50, i know that the tube needs arround 5K.

http://www.goldenmiddle.com/english/trans.htm :
5k/8ohm 40W Recommended tubes: 6P3S, 6L6, 6S4S/2A3, 300B, 6550, EL34, 6P41S, 6P36S, 6P45S, KT66, KT88, G807, GU50, 6R3S, GU19
6k/8ohm 50W Recommended tubes: RB300-3CX, KT66, KT88, 6550, GU50

http://www.realaudiotechnika.bacska.hu/parts.htm :
PPP Raa 2K5/8ohm 120W PPP GU50 (AB 120W RMS!)

 

[Wavebourn]

http://www.realaudiotechnika.bacska.hu/parts.htm :
PPP Raa 2K5/8ohm 120W PPP GU50 (AB 120W RMS!)

What is PPP? 2 tubes in parallel?
One pair of GU-50 gives 120W in PP mode with 6K CT transformer.

Actually, it was a LS-50 stolen from WW-II enemy by Soviet engineers. It was designed by Telefunken ray pentode, after the war they used to produce EL152 that was cheaper than military version LS-50 and Soviet clone GU-50, but anyway it was expensive because of materials and technology. Rated for 40W plate dissipation it could survive more because of specially treated nickel plate that could glow red without a harm for a tube.

http://www.tubecollector.org/main/ls50.jpg
http://www.wiwitubes.com/pic/tube/TFKel152.jpg
http://www.tubecollector.org/main/r-gu50.jpg

I was intended too keep silence about it, because ePay reacts fast on publications on forums...

 

[Zibi]

parallel push-pull

120W@6k load O.K. - but what about anode voltage?
800V? 1kV?

 

[Wavebourn]

parallel push-pull

120W@6k load O.K. - but what about anode voltage?
800V? 1kV?

750 in my amps.

 

[Zibi]

Pretty high.

 

[Wavebourn]

Just enough for an excellent sound.

 

[adam2a3]

Hello, I have built a QUAD II amp using an original QUAD output transformer and in place of KT66's I used the GU50's. Apart from the different cathode resistor I had to install 47R anode stop resistors and to stabilize by VR tubes the g2 voltage. I added an extra 12V dc filament supply. The tubes are used with aluminum heatsinks (!), taken from a USSR transmitter. The dual socket assy as well.
Also there was a PP KT88 amp published in Glass Audio several years ago, in which output tubes were driven from their cathodes by an opamp chip. In this amp the KT88's could be replaced by GU50's that worked whithout problems and as I remember the output was more than 30 Watts of excellent sound. adam2a3

 

[zdenoeddie]

Hi mates!
I renew this thread, I'm going to build PP UL gu50 amplifier. But I'm afraid cause maximum voltge on G2. I have Ub cca 450V. Are anybody tested this tubes (gu50) with Ug2 voltage higher than 300V? Is there any problem, or some faults? Thanks very much!
(Output tran. is 3k/60W/UL taps 43%, with cathode feedback).