GSG in the house...

[fran604g]

Hi folks, this is my first post, so it should be a postive one...and it is! I recently purchased one of Tom's builds from a gentleman in Hawaii, I set it up yesterday and let the adventure begin. I'm using a pair of Sylvania Green Label 6B4G's with a Tung-Sol 6SU7GTY and rectified with an RCA 6AX5GT, all NOS, I believe.

This amp really is dead quiet, you hear people say this kind of thing all of the time, and IMO it's rarely true.

Anyway, I'm loving it so far, Mike, (the man I bought it from) was gracious and included many 6SL7's to try, so I'm going to have some fun for a while

Fran

[Shannon Parks]

Glad you are loving your GSG, Fran. I sure love mine, too! Nice selection of classic octals to keep you busy tube rolling, too. I hope to flesh out the manual and document more mods this summer - like a 300B mod.

Shannon

[EWBrown]

Triode strapped 6AV5GAs also work very well in the GSG design, both with the 6AX5GA rectifier tube, or with SS rectification for a bit more output power. With SS rectifiers, it would be a good idea to connect a 50 to 100 ohm, 5W WW resistor in series with each diode's anode ahd the power tranny HV secondary leads, to keep the B+ to a safe level for the 6AV5GAs, as they can operate with 15 to 18W plate dissipation, but not all of them can handle 20W or more.

I would SWAG that 2A3s would also work well, with a separate 2.5V, 3A filament transsformer for each tube. 2A3s really don't need DC filament power to run quiet, whereas 6B4Gs can be a bit hummy with AC powered filaments.

With a bit of creativity, or by using separate 4 pin tube sockets appropriately connected for each tube type, a 6B4G / 2A3 (or Russian 2C4C) convertible could be designed built.

300Bs have already been proven to be good with the GSG by Tom McNally.

/ed B in NC

[elbinster]

I'm also loving the GSG I finished up about 9 months ago. I don't yet trust any source of tubes so I built in a switch to select between 6B4G, 2A3, and 300B. I took Ed's advice and put in two separate 2.5V transformers for the 2A3s. A simple humpot cancels almost all the hum. I'm running them through a pair of Klipsch KLF-20 (100dB sensitivity) and I have to have my ear right up on the woofers to hear the hum. 300B mod is also a piece of cake, with details spread around the forums here. The 6B4Gs and 300Bs run off DC, so there is no hum whatsoever.

As for the switching, one of my 6B4G tubes died one night and the amp was down for about 5 minutes while it cooled and I switched to the 2A3s (I'm not rich or brave enough to try a hot switch )

Too bad the english language is nowhere near good enough to explain the difference in sound between the three options. There is a subtle difference, but I haven't decided on a clear favorite, as all sound fantastic.

[EWBrown]

A future experiment I will try, is to run 300B filaments with 5V, 2A SMPS "bricks" to light up the filaments. I've seen (and heard) this done with far more sophisticated SET amps, using GM70s and some VICOR 20V, 6A SMPS modules to light them up.

The litle 5V, 2A "bricks are tiny, about half the size of a pack of "coffin nails", and they have the folding AC line prongs. I could use them as-is, or crack open the plastic cases and just use the boards inside. ANd they are cheaper than 5V 2A filament trannies, to boot

With any "ripple" being above 40KHz, it is a very simple matter to filter them, have extremely clean DC filament voltages.

/ed B

[fran604g]

Thanks everyone for the remarks, I've already started dreaming ahead a bit with plans to buy another GSG PCB and set it up for 300b's, but then I came across this:
http://diytube.com/phpBB2/viewtopic.php ... t=6b4+300b

[fran604g]

Glad you are loving your GSG, Fran. I sure love mine, too! Nice selection of classic octals to keep you busy tube rolling, too. I hope to flesh out the manual and document more mods this summer - like a 300B mod.

Shannon

in the vernacular (at least mine, I guess ): u da man

[Shannon Parks]

I'm glad I actually documented that mod! Glad you like the GSG - it has been my main amp the last few years.

Shannon

[ramkumar]

Great topic, good replies. Had great time reading them all.

[msmpe]

Hi All -

Has anyone tried the 1626 in the G*S*G? I know the power wouldn't be much, but with efficient speakers, it might sound reeel sweeet !!



Cheers

[Shannon Parks]

Has anyone tried the 1626 in the G*S*G? I know the power wouldn't be much, but with efficient speakers, it might sound reeel sweeet !!

Working on that *right this second*. It's basically a conversion of the GSG to a Darling-type board that I call the Clementine. Thermion and I are testing the 1626 for Class A triode data (gm, mu and Rp).

Shannon

[Shannon Parks]

From Thermion:

mu:~5
GM:~1650
RP:~3050

Shannon

[Quad]

Working on that *right this second*. It's basically a conversion of the GSG to a Darling-type board that I call the Clementine. Thermion and I are testing the 1626 for Class A triode data (gm, mu and Rp).

Shannon

Here's the test track for that :-)

http://www.youtube.com/watch?v=hUetpcjSmHw