• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

6AU4GTA as High voltage rectifier

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Fuling

Fuling

Member
Joined 2001
Long story short: 813 SE monoblocks, 900V 110mA B+, hybrid Graetz bridge rectifier, capacitor input filter, what tube to choose: 1 x 5R4 or 2 x 6AU4GTA (damper diodes) per channel??

The low prize, indirect heating and long warmup time of the 6AU4´s seems attractive, but will they survive??
I know a lot of people use them as rectifiers in power amps, but 900V and 110mA is not an easy task for a tube rectifier.
 
Gary P

Gary P

Member
Joined 2002
pimmlabs.com
The 6AU4GTA's in a hybrid Graetz bridge should work good.

I have been running a similar power supply for my active loaded 300B amplifier for 2 years now without any problems. The supply for the active loaded 300B uses a pair of 6AX4GTB's in a hybrid Graetz bridge configuration with a 15uf-10Hy-15uf capacitor input filter. The output is 1000 volts at 140ma. The peak and avarage current specs for the 6AX4GTB is just slightly lower than the 6AU4GTA's.

You can use PSUDII from the Duncan amps page to verify that you are keeping the peak current into the first cap below the 1.1 amp peak limit of the 6AU4GTB.

As for why they recommend that you don't use them for power rectifiers I have no clue... They do a great job in the application.

Gary
 
T

The-Planet

Member
Joined 2003
the-planet.org
Damper Diodes

I use a 6CG3 12 pin compactron damper diode as a "slow turn on" for a pair of 866jr's. It's running 825v at around 150ma - works very nicely. I've had it running this way for almost a year now, with regular use.

I'd bet you won't have any trouble with the 6AU4GTA, but some of the later compactron damper diodes have higher ratings.

- Gary

http://www.the-planet.org
 
M

mcs

Member
Joined 2003
stiftsbogtrykkeriet.dk/~mcs/
Fuling said:
Damn it, I just read the last words in the GE datasheet:
(same thing in the Sylvania sheet)
"Operation of this tube as a power rectifier is not recommended"

There is no further explanation why it isn´t recommended?!?
Click to expand...

I think is has a lot to do with warranties, tech. support etc. The tubes were developed for use as damper tubes and they were only tested in that application. Why would you use damper tubes when plenty of power rectifier tubes were available (back then)?

A few of the damper tubes are actually shown with ratings for both uses. Take a look at the Sylvania datasheet for the 6BY5GA. I use that tube in my 2A3 SE amp - works great.

Best regards,

Mikkel C. Simonsen
 
luvdunhill

luvdunhill

Member
Joined 2006
Gary P said:
For the current waveforms you should be able to model the PS as a full wave CT with double the voltage on the transformer.

For voltage output I have been modeling both SS and Vacuum rectifiers and splitting the difference in voltage.

Gary
Click to expand...

just curious, as I'm playing around with this now.... for the voltage output interpolation, are you modeling first as "solid state bridge" and then "VT bridge", or "full wave SS" and then "full wave VT"?

Also, for the current waveforms, are you using the "full wave SS" or the "full wave VT"?

Just curious, is there a better way to do this these days? ;)

Thanks all!
 
S

snoopyma

Member
Joined 2004
Re: Damper Diodes

The-Planet said:
I use a 6CG3 12 pin compactron damper diode as a "slow turn on" for a pair of 866jr's. It's running 825v at around 150ma - works very nicely. I've had it running this way for almost a year now, with regular use.

I'd bet you won't have any trouble with the 6AU4GTA, but some of the later compactron damper diodes have higher ratings.

- Gary

http://www.the-planet.org
Click to expand...

Hi Gary,

I want to use a pair of 866A full-wave rectified to provide 700V, 200ma power supply for my power amp. project.

Can I use a 6CG3 to connect between the ground and the centre tap of the transformer as a slow turn on? If yes, should the plate of 6CG3 be connected to ground and its grid to the ct of transformer?

Would it be better to short it out of the circuit after all are turned on?

Thank you for any advice and information.

Best Regards,
T.C. MA
 
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