6AS7 as rectifier tube?

kmtang · 4th January 2006, 02:32 PM

Hi,

As the GZ37 is getting so expensive, I am thinking if I can use the 6AS7 as an indirectly heated rectifier tube instead.

If it can be done, I believe it need to have the grid and cathode shorted for it to work as rectifier.

My questions are :-

1. What is the current rating with this config?

2. Does it have the same slow turn on time like the GZ37??

Johnny

WALTER BURKHARD · 4th January 2006, 02:36 PM

6AS7 is a double Triode.You can use 5Z3C or 5Z4C or......
regards Walter

Giaime · 4th January 2006, 03:30 PM

I've seen people using an 845 as a rectifier: it was in an all-845 amp, with 5 845 tubes: 2 rectifiers, a voltage amp, a driver transformer coupled to another 845, the real power one... people sometimes are crazy

Cassiel · 4th January 2006, 04:42 PM

I tried it. Sounds great!

About current, it was a monoblock sucking 50 mA so i wasn't worried.
That 6AS7 died in an accident btw (a transformer hit her badly) but i've got now a NOS RCA which is better than the Svetlana.

kevinkr · 4th January 2006, 04:42 PM

The 6AS7 would be a pretty bad choice as a rectifier due to cathode stripping during warm up. Current production 5AR4/GZ34 would be a better choice.

Tom Bavis · 4th January 2006, 05:05 PM

Old production 6BY5G/GA are a dirt cheap, indirectly heated dual diode. 6AX5 is another. For REALLY slow warmup, use damper diodes like a pair of 6AX4, 6W4, 6AU4.

ilimzn · 4th January 2006, 06:33 PM

6AS7G also has a rather low maximum plate voltage...

kmtang · 5th January 2006, 03:26 AM

Thanks so much for your valuable info.

Johnny

hagtech · 6th January 2006, 04:06 AM

I'd be worried about the peak inverse voltage. When plate is not conducting. A tube not designed for such voltages may be prone to arc. The rectifier is a special case that has to endure things no triode should ever see.

Then again. can't hurt to try.

jh

EC8010 · 6th January 2006, 10:51 AM

Quote:

Originally posted by Tom Bavis
For REALLY slow warmup, use damper diodes like a pair of 6AX4, 6W4, 6AU4.

I thought that too - I figured that the thick heater/cathode insulation must slow warm-up. Then I measured 6CL3. They take exactly the same time as any other diode (about 11 seconds).

But don't let me dampen your enthusiasm for them - they're good and they're cheap.

4th January 2006, 02:32 PM	#1
kmtang diyAudio Member Join Date: Nov 2004 Location: Vancouver	6AS7 as rectifier tube? Hi, As the GZ37 is getting so expensive, I am thinking if I can use the 6AS7 as an indirectly heated rectifier tube instead. If it can be done, I believe it need to have the grid and cathode shorted for it to work as rectifier. My questions are :- 1. What is the current rating with this config? 2. Does it have the same slow turn on time like the GZ37?? Johnny

4th January 2006, 04:42 PM	#5
kevinkr diyAudio Moderator Join Date: Sep 2004 Location: Boston, Massachusetts Blog Entries: 6	The 6AS7 would be a pretty bad choice as a rectifier due to cathode stripping during warm up. Current production 5AR4/GZ34 would be a better choice. __________________ www.kta-hifi.net

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4th January 2006, 02:36 PM	#2
WALTER BURKHARD diyAudio Member Join Date: Dec 2002 Location: Helsinki	6AS7 is a double Triode.You can use 5Z3C or 5Z4C or...... regards Walter

4th January 2006, 03:30 PM	#3
Giaime diyAudio Member Join Date: Oct 2004	I've seen people using an 845 as a rectifier: it was in an all-845 amp, with 5 845 tubes: 2 rectifiers, a voltage amp, a driver transformer coupled to another 845, the real power one... people sometimes are crazy

4th January 2006, 04:42 PM	#4
Cassiel diyAudio Member Join Date: Sep 2004 Location: Madrid	I tried it. Sounds great! About current, it was a monoblock sucking 50 mA so i wasn't worried. That 6AS7 died in an accident btw (a transformer hit her badly) but i've got now a NOS RCA which is better than the Svetlana.

4th January 2006, 05:05 PM	#6
Tom Bavis diyAudio Member Join Date: Jun 2002 Location: Macedon NY	Old production 6BY5G/GA are a dirt cheap, indirectly heated dual diode. 6AX5 is another. For REALLY slow warmup, use damper diodes like a pair of 6AX4, 6W4, 6AU4.

4th January 2006, 06:33 PM	#7
ilimzn diyAudio Member Join Date: Feb 2005 Location: Zagreb	6AS7G also has a rather low maximum plate voltage...

5th January 2006, 03:26 AM	#8
kmtang diyAudio Member Join Date: Nov 2004 Location: Vancouver	Thanks so much for your valuable info. Johnny

6th January 2006, 04:06 AM	#9
hagtech diyAudio Member Join Date: Mar 2002 Location: Hawaii	I'd be worried about the peak inverse voltage. When plate is not conducting. A tube not designed for such voltages may be prone to arc. The rectifier is a special case that has to endure things no triode should ever see. Then again. can't hurt to try. jh

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