6V6 high voltage

slideman82 · 24th October 2011, 02:48 PM

I'm going to run a pair of Sylvania 6V6gta at about 420V on plates, basically a Fender Deluxe Reverb power section (about 22W 6V6 pp power amp). The point is I wanted to use diode rectification, but it seems it's not possible doing this (even with right bias). It can be done with tube rectification, but I've read it's bad for the 6V6's with diodes. Must be something to do with max current through output tubes at max power, don't know well, really.

Any suggestions?

TheGimp · 24th October 2011, 03:03 PM

The only issue I can see is if you have a tube rectifier design and you switch to SS without compensating in the power transformer, you will not be running the 6V6s on 420V B+, but something higher as the tube rectifier has tens of Volts of diode drop.

If you choose the proper transformer to set your B+ at 420V, it should not matter. You amy get more rectifier noise with the SS recifiers, but snubbers and proper filtering should take care of that.

boywonder · 24th October 2011, 09:36 PM

Slideman: Model up your power supply both ways in PSUDII; that will show you the difference between SS and tube rectification, and you'll be able to quickly determine what transformer secondary voltage you need for SS rectification vs. tube rectification.

One other difference between the two is that SS rectification will be instant B+ to the tubes (no slow warm up as with tube rectification), and the SS rectification will provide lower PS output impedance, which in a guitar amp, may or may not be a good thing if you want voltage sag at high output.

slideman82 · 24th October 2011, 10:47 PM

I have to order the power supply, but had doubts if it was going to fry the output tubes! Great tips, btw! Just have to place 100uF 450V caps and that's it, I think!

Tom Bavis · 25th October 2011, 12:30 AM

Using fixed bias and relatively low idle current, it should be fine. When exceeding one rated parameter, don't push the others...

slideman82 · 25th October 2011, 03:02 AM

Quote:

Originally Posted by Tom Bavis

Using fixed bias and relatively low idle current, it should be fine. When exceeding one rated parameter, don't push the others...

Exactly!

Enzo · 25th October 2011, 03:22 AM

COnsidering that Leo Fender ran the 6V6s at 100v over the book ratings, and those amps are still running 50 years later, I am betting you can get away with it too.

slideman82 · 25th October 2011, 05:04 AM

yeeeeeeeeeeeeah! But my doubt was if that was possible because of tube rectifier, but now I know I can use diodes! Just that.

SemperFi · 25th October 2011, 12:37 PM

Quote:

Originally Posted by Enzo

COnsidering that Leo Fender ran the 6V6s at 100v over the book ratings, and those amps are still running 50 years later, I am betting you can get away with it too.

Could it also be why guitarists believe that it is normal to change tubes every year?
In those old days (well perhaps today also) the amps with the biggest number sold easier than the one with lower numbers. So squizing 22-25watts out of a pair of 6V6s ment more sale. It may also be the it gives preferable tone, but certainly it is possible to design with tube's life in mind in these days of mic'ed cabs and megawatt PAs.

So my suggestion is why not make it into a cathode biased version and live safe?

slideman82 · 25th October 2011, 01:12 PM

I thought cathoded bias made tubes life last less than fixed bias. 22W can be cranked really good, and using high SPL speakers will make this puppy rock like it should for local gigging! 50W is a lotta power, I'm trying to make friends understand this.

24th October 2011, 02:48 PM	#1
slideman82 diyAudio Member Join Date: Oct 2007	6V6 high voltage I'm going to run a pair of Sylvania 6V6gta at about 420V on plates, basically a Fender Deluxe Reverb power section (about 22W 6V6 pp power amp). The point is I wanted to use diode rectification, but it seems it's not possible doing this (even with right bias). It can be done with tube rectification, but I've read it's bad for the 6V6's with diodes. Must be something to do with max current through output tubes at max power, don't know well, really. Any suggestions?

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24th October 2011, 03:03 PM	#2
TheGimp diyAudio Member Join Date: Aug 2009 Location: Johnson City, TN	The only issue I can see is if you have a tube rectifier design and you switch to SS without compensating in the power transformer, you will not be running the 6V6s on 420V B+, but something higher as the tube rectifier has tens of Volts of diode drop. If you choose the proper transformer to set your B+ at 420V, it should not matter. You amy get more rectifier noise with the SS recifiers, but snubbers and proper filtering should take care of that.

24th October 2011, 09:36 PM	#3
boywonder diyAudio Member Join Date: Jan 2008 Location: So.Cal.	Slideman: Model up your power supply both ways in PSUDII; that will show you the difference between SS and tube rectification, and you'll be able to quickly determine what transformer secondary voltage you need for SS rectification vs. tube rectification. One other difference between the two is that SS rectification will be instant B+ to the tubes (no slow warm up as with tube rectification), and the SS rectification will provide lower PS output impedance, which in a guitar amp, may or may not be a good thing if you want voltage sag at high output.

24th October 2011, 10:47 PM	#4
slideman82 diyAudio Member Join Date: Oct 2007	I have to order the power supply, but had doubts if it was going to fry the output tubes! Great tips, btw! Just have to place 100uF 450V caps and that's it, I think!

25th October 2011, 12:30 AM	#5
Tom Bavis diyAudio Member Join Date: Jun 2002 Location: Macedon NY	Using fixed bias and relatively low idle current, it should be fine. When exceeding one rated parameter, don't push the others...

25th October 2011, 03:22 AM	#7
Enzo diyAudio Member Join Date: Sep 2004 Location: Lansing, Michigan	COnsidering that Leo Fender ran the 6V6s at 100v over the book ratings, and those amps are still running 50 years later, I am betting you can get away with it too.

25th October 2011, 05:04 AM	#8
slideman82 diyAudio Member Join Date: Oct 2007	yeeeeeeeeeeeeah! But my doubt was if that was possible because of tube rectifier, but now I know I can use diodes! Just that.

25th October 2011, 01:12 PM	#10
slideman82 diyAudio Member Join Date: Oct 2007	I thought cathoded bias made tubes life last less than fixed bias. 22W can be cranked really good, and using high SPL speakers will make this puppy rock like it should for local gigging! 50W is a lotta power, I'm trying to make friends understand this.

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