G*S*G paralleled output tubes

2nd harmonics for the masses

G*S*G paralleled output tubes

Postby snowstate » Fri Aug 26, 2016 7:47 am

Can the GSG drive a pair of 6b4g's in parallel?
I search the threads but did not find a discussion on this
Thanks
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Re: G*S*G paralleled output tubes

Postby TomMcNally » Fri Aug 26, 2016 1:24 pm

You would have to make many modifications to run parallel 6B4G's.
The power transformer is not big enough for the extra current, the DC filament supply wouldn't be big enough. You'd need to change the cathode resistor system. The output transformer primary impedance would need to be half of what it is now. Not sure about the 6SL7 drive.
Seems like a lot of trouble for not much benefit.

... tom
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Re: G*S*G paralleled output tubes

Postby snowstate » Fri Aug 26, 2016 2:29 pm

Tom, Thanks for the information.
I was considering trying paralleling the 6b4g's since I had an extra PA060 power transformer. I would have to get the voltage down to 300V but
it should handle the current and has two 6V filament taps. You are right, probably not worth the effort.
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Re: G*S*G paralleled output tubes

Postby EWBrown » Sat Aug 27, 2016 4:40 pm

It might be less complicated to use 300Bs, though they would require higher B+ voltage and current, in order to gain the full benefit. filaments require 5VDC at 1 A, just add a series resistor (1.2 or 1.3 ohms, 5W) to drop from 6.3VDC. Sovtek or E-H 300Bs are fairly decent quality and not too pricey.

https://frank.pocnet.net/sheets/084/3/300B.pdf
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Re: G*S*G paralleled output tubes

Postby jwhitmor » Sun Oct 30, 2016 9:24 pm

If understand correctly, the 6B4G tubes are constructed as two triodes in parallel already. They are normally thought of, and are used, as a single triode.
If it is not making X-rays, your B+ is too low.
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Re: G*S*G paralleled output tubes

Postby Geek » Sun Oct 30, 2016 9:49 pm

jwhitmor wrote:If understand correctly, the 6B4G tubes are constructed as two triodes in parallel already. They are normally thought of, and are used, as a single triode.


Yes.... and because of their construction, you'll never get them to hum balance =:o

Use DC on them.

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Re: G*S*G paralleled output tubes

Postby Vapour » Wed Nov 02, 2016 7:16 pm

jwhitmor wrote:If understand correctly, the 6B4G tubes are constructed as two triodes in parallel already. They are normally thought of, and are used, as a single triode.


The 6B4G is a single triode.
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