January 7, 201115 yr Now I have two competing fantasy images of Craig: either he's in blissful audio Nirvana playing music nonstop and achieving new levels of awareness --or-- he's been electrocuted by the T2. I know the reality is more mundane, but whenever this happens that kind of thing runs through my head.
January 7, 201115 yr I wish no word “2SC3675” or “2SK216” in his next post. Now I have two competing fantasy images of Craig: either he's in blissful audio Nirvana playing music nonstop and achieving new levels of awareness --or-- he's been electrocuted by the T2. I know the reality is more mundane, but whenever this happens that kind of thing runs through my head. I think it may be as simple as he can't post anymore without breaking Inu's wishes
January 7, 201115 yr craig is alive and well. Inu found a slight tweek thats a good idea... 5pf across the 100k feeedback resistors to kill off slight 650 khz oscillations...
January 7, 201115 yr Omygod. I'm speechless and breathless - I've really heard nothing to compare with this. I could witter on about speed and clarity, and the tendency to listen to things far too loud because there is zero listening fatigue. Looks guys - I have a BH, and bloody good it is too. But KG's recreation of the T2 is simply in another league. OK - the right channel has noticeably hiss, but that is because I need to frig with the battery voltage a bit on that channel. What I need to do is stop listening for long enough to pull the lid off again. Mind you - it served up a bit of a fright. I'd had the thing on/off/on/off etc as I was messing around trying various cures for the 650kHz problem with no mishaps. Put all the covers on, heaters came up, but when the HT came on the fuse blew. WTF??? Tore covers back off to find the gremlin. There wasn't one - the 2AT fuse I had in the IEC was clearly not man for the inrush job (6.3A in there now) - but it waited until I'd put the gadzillions of screws in before it gave up the ghost.
January 7, 201115 yr Wife came home to the new walkman on the kitched table [ATTACH=CONFIG]4210[/ATTACH]
January 7, 201115 yr Wife came home to the new walkman on the kitched table [ATTACH=CONFIG]4210[/ATTACH] Such a great picture black Omegas and black T2
January 7, 201115 yr Author Nice going Craig!! The 6.3A is also needed for amps like the ESX, massive inrush current FTW...
January 7, 201115 yr Omygod. I'm speechless and breathless - I've really heard nothing to compare with this. I could witter on about speed and clarity, and the tendency to listen to things far too loud because there is zero listening fatigue. This is a way better way to explain the tendency to crank the volume. No fatigue of any kind, even at ear bleeding levels. And i can listen for many hours at levels way louder than i should. I've been thinking quite a while on this, what i would do to make anything that would be better than this and i just don't have any ideas. I'm still running on a 2 or 2.5 amp fuse, it has never blown.
January 7, 201115 yr Just for the record, there were three mods to the power supply and amp: (1) The power supply mod developed by Kevin and Inu to make it stable (2) Adding precautionary 750 ohm resistors in series with the gates of all K216's (3) Adding 5pF 1kV caps (I used ceramic, Inu used mica) across the 100k feedback resistors. That was also an Inu mod. (1) and (3) are essential IMHO. (2) is discretionary - these resistors were not present in the original from examination of the photos. It has already been said - this sucker runs real hot. Once it has been on for a few hours the heatsinks, front panel and top plate are toasty.
January 7, 201115 yr I've been thinking quite a while on this, what i would do to make anything that would be better than this and i just don't have any ideas solid state front end or all sand version? an all tube version of the BH (tube front end and replace cathode of output stage with tubes)?
January 8, 201115 yr solid state front end is definitely doable. Cut the +250 to +100, use 2sa1486 as cascode transistor, cut R6 in half and use everyone's favorite n-channel front end fets. Add zener at junction of R9 and R10. change out the fet and led's in the batteries for the precision regulator and a resistor, remove one adjustment. might have to fiddle a bit with the range on RV1. Neither should make any change in the sound whatsoever. But its not better. There is no suitable 1kv + transistor to replace the output tube. But if anyone knows of anything suitable please let me know. Something that can handle at least 20 watts with 500 volts across it. Cathode of output stage with tubes is possible but then the -500 would have to be -600 or more, then remove Q26,27,28,29 this would likely change the sound a bit. All the output current would have to go thru this tube, and thats a bit much for the kind of tube you would need to use. Still nothing really stands out as any better. Just maybe a slight bit simpler. If you think this thing gets hot, you should have touched the original. No practical way to replace the active batteries with a tube. Gas tubes have too high an impedance. Edited January 8, 201115 yr by kevin gilmore
January 8, 201115 yr Just for the record, there were three mods to the power supply and amp: (1) The power supply mod developed by Kevin and Inu to make it stable (2) Adding precautionary 750 ohm resistors in series with the gates of all K216's (3) Adding 5pF 1kV caps (I used ceramic, Inu used mica) across the 100k feedback resistors. That was also an Inu mod. (1) and (3) are essential IMHO. (2) is discretionary - these resistors were not present in the original from examination of the photos. It has already been said - this sucker runs real hot. Once it has been on for a few hours the heatsinks, front panel and top plate are toasty. Thanks Craig for summarizing. Very glad you got everything working
January 8, 201115 yr Don't forget the one diode on the power supply board that is backwards, 4 of the diodes, one on each of the supplies is actually a zener and the resistor cross for the servo. also if you get a universal primary transformer, don't wire both the 110vac and 220 vac lines...
January 8, 201115 yr There is no suitable 1kv + transistor to replace the output tube. But if anyone knows of anything suitable please let me know. Something that can handle at least 20 watts with 500 volts across it. Semisouth JFETs! SemiSouth Laboratories, Inc. | Products
January 8, 201115 yr I think that those things are going to perform very poorly at 20 ma, but i'm willing to give it a try. Gate capacitance not too bad. Now to find someone with the things in stock. Would be neat to run the things at 100ma, but you will need a fork lift to move the required power supply... Figure about 800 watts with the current sources.
January 8, 201115 yr Kevin I can help you get them. I'll send a PM tomorrow. They are not cheap. These are the devices in the new Pass amps and the cute ones with his logo are custom devices, if you've seen them. He says they are the best output devices he has seen, ever.
Please sign in to comment
You will be able to leave a comment after signing in
Sign In Now