xianghao Posted April 23, 2015 Report Share Posted April 23, 2015 So to elaborate on spritzer's comment, the 6S4A is a single triode tube, the 12AU7 is a dual triode tube. The 6S4A triode has a much higher max plate voltage (550 volts vs 330 volts) and power dissipation rating (8.5 watts vs 2.75 watts), different filament requirements, they are wired completely differently. their internals look completely different, and neither will work in a circuit designed for the other. They do plug into the same socket so they must otherwise be completely identical . In summary, they are as alike as Arnold Swarzenegger and the Bobbsey twins. If your friend can't tell the difference between the two tubes he likely can't tell the difference between Arnie and Bobbsey. thanks a lot, for this i can argue with my friend. Quote Link to comment Share on other sites More sharing options...
nopants Posted April 23, 2015 Report Share Posted April 23, 2015 might want to tell your friend to use properly sized heatsinks as well Quote Link to comment Share on other sites More sharing options...
xianghao Posted April 23, 2015 Report Share Posted April 23, 2015 might want to tell your friend to use properly sized heatsinks as well oops.. this one was the first demo prototype i built....... it seems no problem but i have replaced it to large size. also replaced the chassis. Quote Link to comment Share on other sites More sharing options...
xianghao Posted April 23, 2015 Report Share Posted April 23, 2015 (edited) here is what he built : waiting to discuss.... Edited April 23, 2015 by xianghao Quote Link to comment Share on other sites More sharing options...
kevin gilmore Posted April 23, 2015 Author Report Share Posted April 23, 2015 i will start. very simple power supply, roughly same as original BH supply at lower power, zener based. definitely drifts with temperature. resistor based output tube. See JimL posts on current sources. And the resistors look like 100K which is extremely inadequate, but match the power level of the tube. Quote Link to comment Share on other sites More sharing options...
spritzer Posted April 23, 2015 Report Share Posted April 23, 2015 That's just so many levels of stupid. Was the intended goal of this design to copy the RSA A-10? I'd love to know the distortion that phase splitter is spitting out. Too tired to run it in simulation. Quote Link to comment Share on other sites More sharing options...
xianghao Posted April 23, 2015 Report Share Posted April 23, 2015 according to what he said: he liked RSA-A10 very much , thought that srm-007 is good enough and why we build KGST with 6s4a. Quote Link to comment Share on other sites More sharing options...
JimL Posted April 24, 2015 Report Share Posted April 24, 2015 Overall view looks like PS board at left, unbalanced to balanced board at top and two amp boards. I'm guessing the unbalanced to balanced board uses a 12AT7 as a long tailed phase splitter with a 2SK170 current source on the tai to improve output balance, with capacitor coupled outputs. A top view of the amp board before assembly would be helpful. Looks like a 12AT7 driver capacitor coupled to a 12AU7 output tube, also capacitor coupled. Load resistors on the outputs which means a lot of the signal current burned up in the load resistors. Not an A10 clone - not enough tubes for SRPP. I'm thinking more parts so more complicated than an SRX, but less sophisticated. In terms of potential output power based on combined plate dissipation, 12AU7 < 6CG7 (used in SRM006) < 6SN7GTA (modified SRX) < 6S4A (KGST) < EL34 (BHSE). The SRM007 uses 6CG7 in parallel so more potential output power than a 6SN7GTA but not as much voltage swing, however the 007 uses load resistors so using good current sources with a 6SN7GTA puts it back on top in terms of available output power. Quote Link to comment Share on other sites More sharing options...
JimL Posted April 24, 2015 Report Share Posted April 24, 2015 And the resistors look like 100K which is extremely inadequate, but match the power level of the tube. On the amp board there are two sets of four 12k resistors, which I'm thinking are the plate resistors in series connection to make 48k. Those resistor values don't make sense as grid resistors and probably not as cathode resistors in parallel either, as the cathode shouldn't need that much power handling, so what else could they be? Not sure of the values or function of the two large resistors between the red capacitors. Anyway, if I'm correct, with +/- 300 volt supplies and the tubes biased so that half the voltage is across the plate resistors and half across the tube, that would make the standing current about 6 mA/plate and the tube dissipation about 80% of max. Quote Link to comment Share on other sites More sharing options...
kevin gilmore Posted April 24, 2015 Author Report Share Posted April 24, 2015 I was thinking those other resistors might be the plate resistors, but then what are the ones in between the caps. Anyway with the resistors not lifted off the board, the same thing will happen that has happened to the kingsound amps. Quote Link to comment Share on other sites More sharing options...
JimL Posted April 25, 2015 Report Share Posted April 25, 2015 I love the smell of burning fiberglass in the morning. It smells like....Kingsound! Quote Link to comment Share on other sites More sharing options...
JoaMat Posted April 25, 2015 Report Share Posted April 25, 2015 .............like ......victory. Quote Link to comment Share on other sites More sharing options...
JimL Posted April 25, 2015 Report Share Posted April 25, 2015 Quote Link to comment Share on other sites More sharing options...
xianghao Posted April 26, 2015 Report Share Posted April 26, 2015 (edited) And a new old friend arrived wonderful status(No.2XX)with original units ,and i have power to make the T-2 for this new friend. Edited April 26, 2015 by xianghao 3 Quote Link to comment Share on other sites More sharing options...
Jon L Posted April 27, 2015 Report Share Posted April 27, 2015 And a new old friend arrived wonderful status(No.2XX)with original units ,and i have power to make the T-2 for this new friend. Nice.. What Stax should have based their SR009 on... Quote Link to comment Share on other sites More sharing options...
DefQon Posted April 28, 2015 Report Share Posted April 28, 2015 12AU7 = 6S4? Spritzer may say its stupid but I find it funny. In reference to tube rollers on H-fi, "Ohh look ma it has same amount of pins lets plug it in and hope for the best." Quote Link to comment Share on other sites More sharing options...
Hopstretch Posted April 28, 2015 Report Share Posted April 28, 2015 Put the plug in the socket, give me all your power. When you turn it on I can go for hours. Hit the switch, push the button, baby, then you'll see, We can have it all, baby, you and me. And KG. -- Nelson Pass. Quote Link to comment Share on other sites More sharing options...
Kerry Posted May 3, 2015 Report Share Posted May 3, 2015 Thanks to the NYC Spring Meet yesterday, I was motivated to finish casing up my KGST. I'm very happy with the result. The chassis is 7" x 12.8". Perfect for my night table Here's the beast in it's intended home: Still need to do the finish and put a respectable knob on it. Here's the back of the amp. Because of the size I wanted to use a single 5 pin mini xlr. Had to build a cable as well. I Put the DAC behind the night table to keep a clean look. I'm just spent the last couple of hours listening and just love it. 11 Quote Link to comment Share on other sites More sharing options...
dsavitsk Posted May 3, 2015 Report Share Posted May 3, 2015 Very nice build, Kerry! Quote Link to comment Share on other sites More sharing options...
kevin gilmore Posted May 3, 2015 Author Report Share Posted May 3, 2015 massively sweet. definitely needs a wood knob. 1 Quote Link to comment Share on other sites More sharing options...
insanity Posted May 3, 2015 Report Share Posted May 3, 2015 very nice and small!! is it your first listen to the kgst? Quote Link to comment Share on other sites More sharing options...
spritzer Posted May 3, 2015 Report Share Posted May 3, 2015 That does look awesome!! One guy who recently got one of my KGST's said his old KGSSHV must have been broken... Quote Link to comment Share on other sites More sharing options...
bozebuttons Posted May 3, 2015 Report Share Posted May 3, 2015 Saw & heard it at the NYC meet yesterday,Pics don't do the amp justice. Kerrys getting really good at this. Quote Link to comment Share on other sites More sharing options...
n_maher Posted May 3, 2015 Report Share Posted May 3, 2015 Very nice, Kerry. Quote Link to comment Share on other sites More sharing options...
HemiSam Posted May 3, 2015 Report Share Posted May 3, 2015 That looks fantastic...and that small footprint. Gobsmacked. I have to say, my KGST is that cat's arse. Only wish my damn SR-007A's didn't present a channel imbalance within a week of receiving them new. Oh well. The Koss ESP's and a closed set of dynamics I bought recently are holding me over. Can't say enough good things about the KGST design. I'm no expert, but paired with the 007A's.....oh my. HS Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.