kevin gilmore Posted September 19, 2017 Author Report Posted September 19, 2017 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
Laowei Posted September 19, 2017 Report Posted September 19, 2017 Thanks Kevin. Your generosity in taking the time to dissect and explain this is greatly appreciated.
Laowei Posted October 13, 2017 Report Posted October 13, 2017 (edited) 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: GG: Edited October 13, 2017 by Laowei
Helium Posted October 14, 2017 Report Posted October 14, 2017 @Laowei: Just curious, what GG board file are you using? What I'm looking at has slightly different traces layout (was posted 20160224). Can you check yours if its newer?
Laowei Posted October 14, 2017 Report Posted October 14, 2017 (edited) 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. Edited October 14, 2017 by Laowei 2
bbest Posted November 19, 2017 Report Posted November 19, 2017 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 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.
Mcwhirr Posted November 22, 2017 Report Posted November 22, 2017 Hello Does anyone have the schematic of gg thanks
bbest Posted November 22, 2017 Report Posted November 22, 2017 Thanks to sorenb and other members who answred my questions, next story begins: More photo on https://cloud.mail.ru/public/JVGf/J2tNmedVm I am ready to assemble both Carbon and GG, and will compare them. 1
bbest Posted January 8, 2018 Report Posted January 8, 2018 (edited) 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. Edited January 8, 2018 by bbest
sorenb Posted January 8, 2018 Report Posted January 8, 2018 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 2
Laowei Posted January 8, 2018 Report Posted January 8, 2018 Don’t forget separate 2X 18VAC secondary taps for supplying power to the input section. 200mA would be overkill for the GG.
sorenb Posted January 8, 2018 Report Posted January 8, 2018 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)
UFN Posted May 6, 2018 Report Posted May 6, 2018 Fantastic work Søren! Can we see the insides as well please?
UFN Posted May 6, 2018 Report Posted May 6, 2018 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?
Pars Posted May 6, 2018 Report Posted May 6, 2018 Very nice, as usual, Søren! What are your impressions of it?
chinsettawong Posted May 7, 2018 Report Posted May 7, 2018 I need a little help with my GG. I just can't adjust the offset of both channels below 50V for some reasons. The balance adjusts to zero just fine though. My PS is measured at 465V. The bias is set at 0.8V or 16mA.
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