Pars

Another stupid question time When replacing the THAT340 with JFETS, would the NPNs be replaced with N-ch, and PNPs replaced with P-ch, or vice versa? For a NPN, the base needs to go positive by the diode voltage, or +0.7Vdc before it will turn on. Somehow it seems that a P-ch should be used here, but not sure. Like I said, stupid question Might not be an issue, as in going thru parts inventory, I have a bunch of 2SK170s but can't find the 2SJ74s I thought I had. If anyone has around 8 (or 4 matched Idss) they would sell, shoot me a PM. Also, this is applicable to anything using complementary pairs of 2SK170 / 2SJ74, but I ran across this last night on DIYaudio: http://www.diyaudio.com/forums/swap-meet/232547-fs-2sk170-2sj74-matched-sets-10.html#post3966396 Has anyone run across this before, and what do you think of it? Not having a curve tracer, no way for me to verify this. Also see attached pdf.

Lookup JFET Idss testing. Quite easy, all you need is a battery (like a 9Vdc) and a DMM to measure current (mA). Like this (which came from the original Gilmore dynamic thread or the dynahi thread on head-fi) http://www.diamondstar.de/transistor_matching_jfet.html And yes nopants, those are the ones I was referring to. Didn't know you could still get those.

The singles aren't hard to match (for Idss), and most of the time are closer matches than what is in the duals (at least from my experience). Linear Systems makes the LSJ74, which seem to only be available thru diyaudio.com in lots of 8 for ~$50. I think the 2SJ74s can still be had? There had also been a run of heat-sink thingies for grouping pairs of these into a single connected unit, but those are probably unobtanium anymore. I would pull the 2sj109 and test it if I were you. Someone familiar with the SRM-3 may pop in and give you more enlightened advice.

Thanks Kevin. This would be for the multiamp, not the ubal to bal converter (I guess these are not the same thing?). Rf is R16 and R19? I assume by Ri you mean input, so the 5K resistors R18 / R33?

I am still considering building one of these to replace my dynalo, but had questions regarding the input section. From what I understand, the THAT340 bipolar input can be replaced with individual JFETs simply by replacing the individual NPN or PNP in the THAT with N-ch or P-ch FETs? C -> D B -> G E -> S Advantages would seem to be higher input impedance and lower offset? Any other changes required to the circuit? Would you want to remove the input series resistors, shown as 5K on the schematic (R18/R33) and jumper these? I still have enough 2SK109/2SK389 or single equivalents to do this. Or is the THAT340 recommended? Anyone listen to either version and have comments?

I think I saw where we got 14.5" out in the sw burbs. I'll shoot a pic of the deck after I get out and run the snowblower again. Shoveling the end of the driveway yesterday was a good time, reserved for my sons I started on it after determining there was no way my small snowblower was going to deal with that. I quickly decided this wasn't old guy work. Very glad I put a new auger belt on Saturday as it would have been worthless without it. Shouldn't be too bad today, other than the dude running the snowplow for the cul-de-sac that I am on the corner of plowed snow across the corner of the sidewalk so not sure how I will get the snowblower over to the cul-de-sac sidewalk. Also not sure I am going to worry about it

what is the warehouse sale?

I presume this is a pic of the finger I think it is... Holy fuck on a stick! Stay safe and warm dudes, and your families. I can sympathize, and my snow blower is cringing in fear of that level of snow! Glad for you guys that it is fluffy and heavy damp wet shit!

Happy Belated Birthdays!

Same here, how did I miss this? At any rate, Happy belated Grahame!

Happy Birthday Mike!

I've never done a balanced amp before but have built some dynalos. Since each channel +/- board is referenced to ground internally, and just because it seems intuitively correct to me, I would think you would want to try to 0 out the offset for each + or - channel to ground, and then try to 0 the +/- for that channel. I could be wrong though...

Happy Birthday!

Happy Birthday John and Frank!

I like this approach, assuming you use stout enough leads

Nice build! I'm not sure he meant he made the switch himself. Don't be a dick.

Hehe. What is this "broken parts" he speaks of? I'm not sure I've ever experienced this...

Happy Birthday!

Happy Birthday Jacob!

Best wishes

^ PM sent.

Happy Birthday Ken!

Mike said it best! Merry Happy Birthday Ric!

John, nicely stated! Best wishes to all!

I've never ridden one and don't know much about them. You might hang out here for a bit and pick up some interesting bits... http://www.bikeforums.net/recumbent/