Sourcing parts for GSG, couple questions

2nd harmonics for the masses

Sourcing parts for GSG, couple questions

Postby denverartist » Tue May 06, 2014 9:02 am

I'm gathering parts for my GSG project. It all started when I found I had 3 good US 6B4Gs and wondered what I could do with them. I am no newbie when it comes to building amplifiers, but this is my first SET build and I will be working with Hi-efficiency speakers as well, also a new area for me.

Question: I have good, powerful older pwr transformer with 4+ Amp 6.3VAC filament supply. Can I supply both sides of the PCB filament supply with this? Just run wires to both sides, L A/B and R A/B?

Can a 900ohm 5W R be used instead of 3x 2.7K ohm resistors?

It appears the board is grounded to chassis in one place only, at transformer center tap? And just to be clear, input jack grounds are only connected to board?

Thanks for advice.

Peter
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Re: Sourcing parts for GSG, couple questions

Postby Shannon Parks » Wed May 07, 2014 5:18 am

denverartist wrote:Question: I have good, powerful older pwr transformer with 4+ Amp 6.3VAC filament supply. Can I supply both sides of the PCB filament supply with this? Just run wires to both sides, L A/B and R A/B?


Unfortunately the GSG design needs two separate 6.3VAC windings for 6B4Gs.

denverartist wrote: Can a 900ohm 5W R be used instead of 3x 2.7K ohm resistors?


That would be fine.

denverartist wrote:It appears the board is grounded to chassis in one place only, at transformer center tap? And just to be clear, input jack grounds are only connected to board?


That method (my earlier method) works OK, but sometimes can be improved with a single wire from the PCB ground (J6-2 or J6-3) to chassis ground (usually to close to the safety ground).

Shannon
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Re: Sourcing parts for GSG, couple questions

Postby denverartist » Wed May 07, 2014 1:24 pm

Thanks very much, Mr Parks. I guess I should just bite the bullet and order the Triode transformer. I like using vintage parts but I'll sell 2 of my old xformers to (partially) finance this project.

I'm so used to point-to-point wiring, this should be very neat and tidy build.

Planning to adapt this walnut wood base (from old turntable).

Cheers,
Peter
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Grid resistor Q

Postby denverartist » Fri May 09, 2014 8:35 am

I've always found the resistor to the signal grid very important, in this case the 1000 ohm R-3,4. What composition has been found to be best by GSG builders? Carbon comp? metal film? carbon film?

Thanks

Peter
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