Jim Thompson wrote:> My customer bought the MCU core IP from Cadence and I added the signal > conditioning around it, with glue logic (and MCU programming) provided > by Mark Tse (quite a talent)... who thought I was around 50 years > old... and was quite surprised when I told him I was coming up on 72 > (at that time). > > Now my next milestone is 3/4C :-D > > ...Jim Thompson >He was a programmer and probably meant it in hex (72 = 0x48) :-) -- Reinhardt Behm
Headphone amp simulation
Started by ●May 26, 2014
Reply by ●June 1, 20142014-06-01
Reply by ●June 1, 20142014-06-01
"Jim Thompson" <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote in message news:02fko9tn5tntoek65u8a3jdrspa5men65v@4ax.com...> I have a 6DS4 (RCA Nuvistor) sitting here on my desk... and I've seen > photos of experimental devices about the size of a surface mount > capacitor. > > For lots of HV applications I'm surprised that no one (*) has thought > to put a transistor under the cathode of a tube... a lot more durable > that a Power FET. > > (*) Maybe someone has, somewhere?Tek certainly did it a lot during their hybrid days, but if you mean co-packed, I can't imagine a 200C bulb temp would be so friendly, even if the chip is glass passivated (hey, just weld it onto the envelope, who cares right?). I've also seen co-pack (or maybe they're actually monolithic?) BJT-MOSFET cascodes for moderate voltage switching applications, but I haven't thought of a place they'd be useful. I used to tell people that an EL519 -- ignoring the heater power, or maybe not even, depending -- is still several times better than the best commercially available HV MOSFET. But, now that IXYS has some 2.5kV ~10A devices, that has also passed. Tim -- Seven Transistor Labs Electrical Engineering Consultation Website: http://seventransistorlabs.com
Reply by ●June 1, 20142014-06-01
On Sat, 31 May 2014 21:12:30 -0600, Reinhardt Behm <rbehm@hushmail.com> wrote:>Jim Thompson wrote: > >> My customer bought the MCU core IP from Cadence and I added the signal >> conditioning around it, with glue logic (and MCU programming) provided >> by Mark Tse (quite a talent)... who thought I was around 50 years >> old... and was quite surprised when I told him I was coming up on 72 >> (at that time). >> >> Now my next milestone is 3/4C :-D >> >> ...Jim Thompson >> > >He was a programmer and probably meant it in hex (72 = 0x48) :-)>:-} ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
Reply by ●June 1, 20142014-06-01
>"For lots of HV applications I'm surprised that no one (*) has thought=20to put a transistor under the cathode of a tube... a lot more durable=20 that a Power FET.=20 (*) Maybe someone has, somewhere?" Shut the fuck up if you want to live. those NSA guys don't play around. LOL Problem is that the temperature at which thermionic emission get going is d= estructive fro most transistors. for germanium it might be totally impossib= le, for suilicon nby yhte time you derate it you will not have the power to= feed a cathode driven amp, which would be the only purpose of suc a circui= t.=20 Of course emitter turnoff has existed for some time now. when the load is h= ighly inductive, they will take a transistor and turn it off on the emitter= of the main transitor. This makes the biug transistor shieild the little e= mitter transitor from the big bad voltage, but enhances whart REALLY happen= s between the emitter and base of the big transistor. They actually used it= in brownware for a short time, for wide screen CRT based projection TVs. t= ha is until better transistors got ther (the 2SC5588 IIRC). then only the t= races and silkscreening remain, and of course the one jumper. the drive cir= cuit still sowed soigns of the scheme. I cna do a screen catpur if you have= any interest in this, or if you can handle DWG files. Problem is it wasn't= used in any units I worked on so I don't know how wlell it worked. In fact= I wouldn't anyeay as I had no tinme for those unprofitable excursions much= .=20 But yeah, a little shit ass transistor in the emitter circuit that could ha= ndle the curtrent but not the voltage, wa sturned off as the big transistor= was tirned off and the cpaacitance of the big transistor aided in its own = turnoff.=20 Pretty novel little deal, and cheap. Applied to the cheapest pf the cheap t= o save money on the drive circuit. As I said, better transistors came forth= and the design was changed to eliminate this drive opitmization as soon as= it was no longer needed.
Reply by ●June 1, 20142014-06-01
Reply by ●June 1, 20142014-06-01
>" starting with 6V6... 6L6... finally KT88's, then went=20"solid state" when I went to..." (snipped the part thar fuckd it all up... I'm currently selling a pair of Chicago BO-15s. Were driven by 6550s, the G= OOD versoin of the octal tubes. charging a hundred bucks. One guy in Chicag= o wants them but I haev to shoip them. a local guy is offering half that. M= aybe I kjust keep them. They are in a pair of monoblocks built by my Uncle.= I still have the 6550s and the emossion tested fair to good a couple weeks= ago. They hadn't been lit for ten years so they are probably better than t= hat indicates, once you warm them up. and the getters are not all that gone= . They are brown but not flaking off the glass. The transformers are triple center tapped primary willianson type with four= and eight secondary taps. the chassis' they are oin now are configured for= 100 watts RMS (yeah I know) into four or eight ohms. The power transformer= s are bigger thant they are. Which makes sense.=20 One guy offered fifty bucks. No way. hundred bucks her, or forget it. These= things sounded great and might run, well one of them, if I had all the tub= es. Well, maybe. Stole a few parts off.=20 You are just an IC away fom a new breed of amp.=20 But I ain't taking fifty bucks.=20 Can we switchmode these things and make them class E or F or someting ?
