luvdunhill

not to mention the backwards resistors and rather static attenuation

We need to finalize the production boards and place the order. When we do this is really dependent on how much feedback we as a team want from Kevin and digger945. It probably makes sense to get as much feedback as possible from the both of them. I've made my suggestions in this thread and have sorta moved on to other things that are on my plate. Whether or not all the suggestions are implemented is really up to j4cbo I guess, and how willing he is to comb back through the thread and meticulously pick up all the comments and suggestions ... as he's the one that will implement the changes and feature requests. Once I receive the boards, I'll send out the boards with the matched devices. This includes the JFETs, the BJTs and the MOSFETs. There is still a little bit more matching to do, probably 40 hours or so. I don't even want to think how much time I've already spent... That's about it I think.

why not use a plate amp and case it up, or even a car amp?

dude that is sooo last night...

We had 0day for Chrome the second it was publically released. Literally that second. The same will happen for ChromeOS, I bet.

more like 1/4 of a discrete I/V

I think that's where the magic pebbles go.

some green things with "tooleaudio" printed on them

whatever les_garten is smoking telling off jp#s like that...

I dunno how to explain it. Maybe someone else can better. But, this calculation is fail: 18W / 60V = 300mA / 8 FETs = 37.5mA per FET this calculation is win: 18W / 60V = 300mA / 4 FET pairs = 75mA per FET Then power per device is 75mA * 30V. And with 75mA * 30V * 8 devices = 18W we're back to where we started.

no, four pairs at 75mA through each pair. Remember, current is calculated (edit: maybe "defined" is a better word, I dunno) from rail to rail. So, if one n-ch flows 75mA then the other complimentary p-ch device flows 75mA.

no. The original design was 150mA per FET with 4 devices. See the posts above. Once you doubled to eight, it requires double the heat sink. Instead, Kevin halved the bias so he didn't have to go out and by a larger heat sink, or go from 2 boards per heat sink to one, or run the die temperature way up.

See Kevin's post above. Nothing has changed. Four FETs @ 150mA or 8 FETs @ 75mA. Same heat. I ran them harder just as a proof of concept, but this has always been the recommended current.

Would it help if I sent you a 160VA 2x30 toroid? Probably could drop it in the cheapest flat rate USPS box.

Ok, I see. I thought you recommending 75mA for the 4 FET version. In which case, nothing changes it's just as hot as we thought. So balanced would be 72W. My recommendation of heat sink still stands.

COBOL absolutely should fulfill a foreign language requirement

well, okay, but I for one interpreted your comment in post #19 as designing towards 150mA: HeadWize: DIY Workshop > My newest in the dyna series "If you run the default of 150 ma per fet, the 2 ohm resistors are fine." In hindsight, I see how that comment could have been misconstrued in a number of different ways. All that said, I think more than 75mA is better. I know there are quotes from Borbely who uses these FETs in one of his design that many of his customers preferred them at > 100mA, and I tend to agree. Here's a quote from his old website: "More is Better (sometimes)! Although the fact is well known that MOSFETS require a lot of current to sound super, I believed that the suggested 40mA or so in the output stage was optimal. Until one of our customers suggested to try more. Mind you the tiny heatsink we are supplying with the Kit can

Well, 2.5dB +/- 2dB

3 minutes? heh. Try the other feedback setting as well, once you get accustomed to this version. Need to recruit more advocates for adding a switch here

She'd probably just take it to Ray to fix anyways Oh, pabbi1, so far things have been pretty boring, except for this little "incident":

Has anyone ever looked at, or used these On Semi parts? Look interesting to me. (Mouser part numbers below): 863-MPSW56RLRAG 863-MPSA56RLRAG 863-MPSW06RLRAG 863-MPSA06RLRAG The "W" devices are rated to 1W @ 25C in free air.

I think that the MF30-100 is a solid recommendation for the DynaFET at this point. This is based on the results of my heat sink and some crude math. This heat sink is 300mm wide, 100mm tall with 30 48mm fins. The base is 8mm thick. It is rated as 0.32 C/W @ 80C, or around 0.35 @ 60C. That results in 171W at @60C. Given two boards of 4 devices and 30V rails, that right at Kevin's recommendation of 150mA, at a conservative die temperature. I wouldn't even recommend using 8 devices with these. This is my standard recommendation, if anyone is looking for one. If you're using another heat sink that you don't trust the C/W rating for one reason or another, you can use a crude method of comparing the two based on dimensions alone.

This is the prefect chance to do a little perf board project.

They are the .1%, 25 PPM/C versions: http://www.prpinc.com/pdf/Audio_PR9372_Series.pdf

I wish I could buy those PRP resistors