Pars

Well, yes high. How many would you need to buy to ensure good matches if you were doing it yourself? ~$30 for 8 LSK170s and $62 for 8 LSJ74s. You might get a matched quad out of that, but I had heard that Linear's devices are all over the map regarding Idss within a certain grade.

After re-reading much of this thread (for I don't recall how many times), the feedback isn'w quite what I expected. It appears by the attached drawing, marked up to correspond to Kevin's post, that the feedback is either: pins 3-2: output to inverting input pins 1-2: midpoint of R19/R20 (2K, not 5K) to inverting input For some reason, I thought it was either 1 above, or output to midpoint. In looking the board files over, I see that that is wrong. Also, for the midpoint feedback (#2), there doesn't appear to be a gain resistor in play, unless R19 || R20 acts as the gain resistor? I'm using the output to input FB, and could not get the midpoint feedback even close to working. And to clarify on your comment on SJ2 (which was not on the boards), you had never intended to ground the midpoint of R19/R20 in any circumstance? Thanks!

Speaking of which, I thought that Linear had released an LSJ109? They don't show them on their site, and from what I could find, they claimed they were available, but no one seems to have gotten any? Fast forward to today with the LSJ689... Trendsetter doesn't list them, and apparently the other place referenced doesn't either? Are these going to be the same thing again? They do seem to really have LSJ74s, so at least there is that.

OK, thanks Kevin.

Yes, that is the same one that I have. R19 and R21 are 15k on it. The board has a pair of 5k on the silk, which is these resistors (I think). The thread had a cfp2f schematic posted by Kevin on his northwestern site. I don't find this in the current archive. Sent from my iPhone using Tapatalk

No one has this schematic? Sent from my iPhone using Tapatalk

I haven't tried them, but those did look very interesting on the Linear site. Probably impossible to do an adapter board accommodating all comers, including the old 7-pin Toshiba duals, but maybe with the Linear round cans or SMD packages of these, plus the singles.

I'm kinda surprise with your posts regarding "purity of the build", that you went that route to begin with. Glad it is sorted, as the T2 seems to be a well documented build regarding "Do.s/Dont's).

Once everyone adapts 4.4mm, then everyone is backwards compatible, both single ended and balanced. See how that works? See all of the high quality and inexpensive connectors out there? Sent from my iPhone using Tapatalk

Thanks Michael! This has some differences from the BOM I was putting together and from trying to follow the thread. No 15K resistors (guess they're 5K now) 20K resistor 22pf cap I take it the 2x50K resistors in the schematic are now 1 100K? Same with the 2x34K resistors are the single 68K? I can't find the schematic mentioned in the thread (cfp2f.jpg), 2nd page of thread around April 1, 2015.

Oh boy... Got an email from these guys today describing their new DAC. I recall them being quite the tube hacks back in the (HF) days. http://www.doge.audio/products/tube-dac/doge-7-tube-dac/ I would presume that they haven't changed much... Sent from my iPhone using Tapatalk

You need a fugly set of cable pants for your Y split. I keed I keed.... nice job! Sent from my iPhone using Tapatalk

I believe it is simple physics... smaller = more heat Sent from my iPhone using Tapatalk

I would guess it is because everything is in a smaller area and enclosure, thus less ability to dissipate heat.

I also saved it and did find it (if it is the one Kevin was thinking of)...

If you have the THAT socketed, you can just plug the JFETs in there, assuming they are thru-hole TO92 packages (that is what I did on my SS Dynalo). Make sure they are good machined pin sockets though (Mill-Max, etc.) and not those crap leaf sprung ones.

Happy Birthday Marc! Sent from my iPhone using Tapatalk

Appears to be back up again

Thanks Michael... yes, I rather like that one. As for the Dynafet, yes it uses obsolete parts, some of which you could work around: 2SJ109/2SK389 dual (sub linear systems LSJ74/LSK170 x2) 2SA1349/2SC3381 dual (sub 2SA970/2SC2240 if you can find them; not sure what else would be a good sub) 2SA1145/2SC2705 (possible sub 2SA1370/2SC3467). Don't know if the SS thru-hole transistors would be a good replacement, and would have to check pinout And the FETs. These were designed to use the Renesas 2SJ76-79 and 2SK213-216 (mine uses 2SJ77/2SK214). You can still get the J79/K216 I think, but they need to be matched (closer the better). The FETs that Amb uses for the Sigma22 will work (pinout needs checking) and apparently are much less cranky than the Renesas parts. In the Dynafet thread, I had also posted some links to threads on diyaudio listing possible replacements as well. This might not be something you would want to play with, as you probably saw all the mods I had to do to get mine to work. This has been the only amp of mine that I have been listening to though. I might be interested in your pair of CFA (CFP?) boards anyway, so shoot me a pm if you want to part with them.

Don't quite understand your question? At any rate, the ground lug from the TRS jack should go straight to PSU ground (sigma22?)

I'd go for that Michael, but took a look and don't have any more blanks. I do have a built-up one with Roederstein resistors, all devices socketed with Mill-Max pin sockets. That one has some sentimental value to me The original transistors that I had (have) weren't that bad between N and P. I do have a pair of original Dynahi boards, as well as around 5 of the original Dynahi PSUs. Also, a couple of cetoole discrete I/V boards, some amb and KG protection boards (with my mods), etc. Oh, and a pair of DynaFET boards To vortaku: I would recommend using the modern SS layout, using current parts. Many of the parts for the original are somewhat unobtanium (Toshiba 2SJ74 2SK170 JFETs). You can get equivalent parts from Linear Systems, but the original transistors (2SA1015 / 2SC1815) aren't easily obtained.

I worked withDan Gardner quite a bit on this around this time, doing edits for the build guide, etc. I've never seen board files or gerbers for these, and I am pretty sure that Kevin doesn't have them either. Dan hasn't been active on these forums for a long time. Either we could contact him or I could possibly do a layout. I may still have a couple of boards but would need to look. Sent from my iPhone using Tapatalk

Hmmm. I would probably start by swapping the input wiring (pot to boards). If the noise moves then it has something to do with that. Otherwise go over the board (components and location correct? Solder joints?) Sent from my iPhone using Tapatalk

Happy Birthday! Sent from my iPhone using Tapatalk

Interested in building a single-ended CFA2 (or is that CFP2)? Can't find the schematic matching the cfp2gmt board files on the archive... I have the cfa2.pdf schematic, but it doesn't match the board file. Maybe I'm not looking for the right name here... Also, what is the board size on these? I'll have to admit I am having a hard time following this thread and all the loops and progressions from se to balanced to power amps...