I've ordered everything except caps. I found someone selling some old 500v's on 'th bay, but I don't trust them. Just can't find any 10uF's so I'm tempted to go with a film cap.
Allied Electronics has over 7000 items listed on their "excess inventory" pages. The parts are discounted 30 to 50%. The link to these parts seems to show up on their home page randomly (posted below). There are lots of parts that are useful to amplifier builders on those pages including some Cornell Dublier 500 volt electrolytics.
Part numbers:
862-6224 120uF 500V $2.85 I have one of these in a Simple SE I paid over $4 2 years ago
862-6212 82uF 500V $2.05
862-6216 100uF 500V $2.31 Still shows 17 in stock, but I ordered 10 this morning.
862-6210 68uF 500V $1.80
862-6214 82uF 500V $2.03
There are also some Fuji mosfets (I thought Fuji made cameras and film) rated for up to 900 volts with very low capacitance. How about a 600 volt mosfet rated for 43 amps and 600 watts for $5! Even I couldn't blow those up, but I didn't buy any (2SK3681). I did buy some 2SK3524, 600 volts, 135 watt, 8 amps, 4.0 pF!!! reverse transfer capacitance, for .......90 cents each!!!!!! I also couldn't resist some 2SK3675 , 900 volt 195 watt, 7 amp, 8pF for $1.40.
If you waste most of a day with their search engine, you can find some useful resistors and some coupling caps. Other semis too. I have now placed 2 orders totaling over $300. The search engine doesn't always find everything. There are some 600volt electrolytics that it didn't find, but they were over $8 each, so I didn't buy any. Yes, I went through all 7000+ parts listed.
http://www.alliedelec.com/absolutebm/abmc.aspx?b=59&z=35
Part numbers:
862-6224 120uF 500V $2.85 I have one of these in a Simple SE I paid over $4 2 years ago
862-6212 82uF 500V $2.05
862-6216 100uF 500V $2.31 Still shows 17 in stock, but I ordered 10 this morning.
862-6210 68uF 500V $1.80
862-6214 82uF 500V $2.03
There are also some Fuji mosfets (I thought Fuji made cameras and film) rated for up to 900 volts with very low capacitance. How about a 600 volt mosfet rated for 43 amps and 600 watts for $5! Even I couldn't blow those up, but I didn't buy any (2SK3681). I did buy some 2SK3524, 600 volts, 135 watt, 8 amps, 4.0 pF!!! reverse transfer capacitance, for .......90 cents each!!!!!! I also couldn't resist some 2SK3675 , 900 volt 195 watt, 7 amp, 8pF for $1.40.
If you waste most of a day with their search engine, you can find some useful resistors and some coupling caps. Other semis too. I have now placed 2 orders totaling over $300. The search engine doesn't always find everything. There are some 600volt electrolytics that it didn't find, but they were over $8 each, so I didn't buy any. Yes, I went through all 7000+ parts listed.
http://www.alliedelec.com/absolutebm/abmc.aspx?b=59&z=35
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They made some awesome printers in their day (who remembers the DL-3400?)
Hmmmm... RF fodder?
Cheers!
My board is still in the mail somewhere. Edcor says three weeks for the transformers.😱
Can someone tell me the standoff length for mounting the board. I'd like to add this to the BOM so I don't forget them.
Thanks,
Jeff
Can someone tell me the standoff length for mounting the board. I'd like to add this to the BOM so I don't forget them.
Thanks,
Jeff
Actually I was thinking sandy state audio output devices. Somewhere in my future there will be a fully differential class A amplifier. It will be based on the octal driver board that I made for the 6L6GC in AB2 thread. I want to try tube, mosfet, and BJT output devices. I also plan to revisit the augmented cathode follower with a mix of tubes and sand.
RF, well I am dreaming up the ultimate ham radio since the really good ones are beyond my price range. The HF portion will likely use MRF150's since I bought some MRI amp boards in Dayton that have a bunch of MRF150's.
The length will depend on the tube sockets that you use. Unfortunately the sockets that I mounted on my board are not the same height.
For the sockets I used, 1/2" standoffs (or 12mm) work great.
Sorry about the mail... I've never understood why it can take 2 weeks to get from the US to Canada.
Edcor told me 3 weeks too, but delivered in about 10 days, so keep your fingers crossed...
Pete
I initially tested with some James JS-6228HS transformers, which are rated 8k plate-to-plate at 25 watts. The distortion was flat to about 10kHz, then sloped up from there to about 1% at 30kHz.
Unfortunately it looks like I didn't save the plots! And I really don't feel like ripping the amp apart to try it agan...
That said, I'm really not sure how much distortion at such high frequencies is audible. If you go by the engineering assumption (no flames, now, I am not necessarily saying this is true!) that the audiblity stops at 20kHz, then only H2 at 10kHz is audible, and H2 + H3 at 6.7kHz.
I also suspect tweeters have much more distortion than the amp, though I'm not sure.
Pete
FYI.... the second batch of boards are all sold, but there are more coming.
Anybody have something built yet? Comments/questions/photos?
Pete
Anybody have something built yet? Comments/questions/photos?
Pete
Been there; done that. I did a design with BJTs that turned out quite well. Don't let your finals bang up against the rails, give 'em headroom. Secondly, quasicomplimentary finals may measure worse, but definitely sound significantly better.
I'd like to do something with these SiC JFETs. They're something new, pricey, and not at all easy to get. These will need OPTs since they have to run at unusually high voltages (for solid state).
MOSFETs: best run these Class A. Class AB with MOSFETs just plain SUX.
Yup!
They can lock-up full "on" sometimes if slammed on the rails 😱
Agreed.
Cheers!
Congratulations Pete on selling out your second set of boards!
I have three projects on my bench to finish before I get to your Amp. As soon as I am done I will post some photos.
Cheers, Alan
What I have in mind will bear little resemblance to the typical SS output stage. There will be an OPT no matter what the output devices are. Early low power experimentation favored the sound of the BJT, but higher powered experiments vaporized parts due to SOA limitations. BJT's, OPT's and lotsa volts blew up a lot, hence the 900 volt mosfets.
Thanks.🙂
No apologies necessary, it's not uncommon for stuff to take 2 weeks to get up here. I never complain unless something arrives damaged.
Yes, the nice ladies at Edcor mentioned that I could see them sooner.
Jeff
I always count on 3-4 weeks.
But it is silly, considering it's 3-5 days for stuff coming down your ways 🙄
(in my experience)
Cheers!
Hmmm, I have a couple of those, too. I'll take some spectra at spot frequencies (I don't have your cool distortion vs freq plot capability yet). It will be interesting to see how they compare to the "classic" UTC iron.
Again, I am interested (and pretty sure I have all tubes and sockets),
if there's a local pickup. Still need knobs too, I need to note the model
of my Tek scope whats missing the the twirly bits... That scope buried
much deeper than the compactron Pentodes were found.
Frequent any local HAM radio meets, Tanner's?
if there's a local pickup. Still need knobs too, I need to note the model
of my Tek scope whats missing the the twirly bits... That scope buried
much deeper than the compactron Pentodes were found.
Frequent any local HAM radio meets, Tanner's?
Pete stated he used a "shallow load line". A lower load impedance will result in higher output power and possibly higher distortion. I will not get to build mine until November, but I plan to use a 6600 ohm OPT. I have extracted lots of power from similar sized sweep tubes and a 3300 ohm OPT. The distortion was still very reasonable for power levels under 30 watts.
Never heard of an Eico ST-70, but a Dynaco ST-70 or any other ST clone that I know of that used EL34's, have 4.2K OPT's, not 6.6K.
Cheers!
Old school integrated, not the greatest schem: http://www.triodeel.com/eist70ps.gif
Looks like decent iron?
Jeff