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what you are essentially doing is changing the gain on the output tube by a small amount. Something like .1db or so. larger changes in the resistance would change the gain even more.  The rest of the circuit will compensate to keep the overall gain the same, so there may be other slight differences. For this circuit the diode is just taking .7v from the voltage from plate thru the resistor to the grid.

transformer circuits where the plate will swing negative with respect to ground will definitely respond differently to the diode

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Just like Carbon we built. Same box, same PS. Relay=120s. Separated filament transformer.      

Another Grounded Grid lives.  Have been listening to it for about a week. Powered by the same GRHV/GRLV PSU I use to power my KGSSHV, Carbon and Blue Hawaii. 400VDC rails and 20mA plate current.

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  • 4 weeks later...

Another couple of questions on grid connections in the output sections’ triode wired EL34s in the GG.

1) Per the GG PCB, and also the KGBH schematic, G3 (the suppressor grid) is tied directly to the cathode.This is the conventional connection for a grounded cathode circuit. In a grounded grid circuit where the cathode is driven, wouldn’t the added G3 parasitic load be harder/non-linear to drive?

2) In the DIY T2 and T8000 Sandwich PCBs, G3 is directly connected to the Plate. circuit. Is the suppressor function really needed in a grounded grid triode? Seems like driving the cathode only would be optimum in a grounded grid circuit. 

3) Does the STAX T2, or DIY T2 have a history of being harder on the output EL34s’ G3, than a KGBH? I searched and could not find any mention of this. 

4) Any advantage to cutting and modifying the traces on my GG PCB to try out the G3 to Plate connection? 

Thanks for any advise offered. 

 

T8000 Sandwich:

1C3B569B-6339-4362-9A39-749025E5C8F4.thumb.png.5404d10fc4fe1637099fe0c089223280.png

 

GG: 

C3AC501E-FFBC-4646-BA17-9A9AF2FABB85.png

Edited by Laowei
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The graphic is from earlier in this thread where the PCB was first posted. It matches the traces on my PCB. Both appear similar and no printed Revision level is found. I bought my boards from another member, so probably the first.

Kevin quickly drew up the GG (a tube version of the Carbon) to humor us vacuum tube Luddites. 

Your example looks like a later version. Basically the same, just tidied up a bit. The amazing thing is, even the quickie electrostatic amp designs that Kevin publishes, are simply incredible sounding. He is an irreplaceable source of inspiration for us DIYers. 

 

 

 

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  • 1 month later...
On 7/30/2017 at 12:56 AM, jose said:

I like the powerful amps with "flat" sound, like Dynalo/hi or Beta22, so the Carbon is the one that best suits my tastes between the GG/KGST/SRX-P. For this reason, Carbon has become my reference amplifier for Stat.

Anyway, I'm not being fair because I haven´t found a quad of valves for the GG that sound good to me. Maybe when I try the 6CA7 I will be more comfortable with the GG.

Excuse the long answer for such a short question :sadcat:

 

I have balanced beta22 + moded HiFiman HE-6. Also owned tube push pull stax amp. As for me, tube amp sounds more lovely than beta22.

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7 hours ago, bbest said:

Hello all!

How many mA in transformer prefer to use for GG? Voltage 360 (=> 450V output) and 350 mA is it will be enough? On another forum recommended 500VA transformer for tubes amps.

( 2 channels x (2x Output stage current  + 10mA for input stage )*sqrt2*360VAC + 4x 6.3VAC*1.5A ) * some_factor depending on how much overkill  ~ 100VA * some_factor 
I usually end up using a factor somewhere above 2 and close to 3 

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2 hours ago, Laowei said:

Don’t forget separate 2X 18VAC secondary taps for supplying power to the input section. 200mA would be overkill for the GG. 

10mA * 360VAC should account plenty for that ;o)

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  • 3 months later...

Modushop Dissipante 2U/400mm by the looks of it ;)

More interested to know if hifi2000 did the customisation to the front and back of if that was someone else? :D

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