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Agreed, not worth messing with. EDIT: And I found out last night what you were talking about regarding the two DC offset pots Marc. I didn't realize they would effect the bias as well, and had one board biased >300 mA for a short time. Pulled the board and found I had one side at around 45 ohms (pot || 620 ohm R). I may replace one side with a 500 ohm resistor. This is the most stable wrt DC offset of any KG design I've built. Sent from my iPhone using Tapatalk

^ I knew I forgot something in that post... disposal of that crap

I dunno John, you do such shitty work... sure, I'd love it if you shared that

http://www.antekinc.com/as-0528-50va-28v-transformer/ Earlier in the thread (had you read it) KG said you need ~35V raw dc, so 27 * 1.414 will get you ~38V minus the diode drops for the rectifier(s). I haven't looked at the schematic, but assume a bridge, so -1.4V, so you are at about 32.6V raw DC. Might work. 27-28V transformer will get you closer. 28V Antek above would put you at (28 * 1.414) - 1.4 = 38.2V. It appears some have built this with a 25V transformer.

I figured that. Same with bipolars, normally. If someone had a matched set of these I might be interested. Should be a bunch of them out there. I know I got the set I am using from you, and had been going back thru the GB stuff and my email, but didn't find where I had talked to you about them.

Went back to the 10K/1K feedback resistors, and all is well again. I've been reading online (Cordell, IRC, others) regarding using parallel mosfets with no source ballast resistors. Nelson Pass has been talking about it as well (Burning Amp talk). I know the Counterpoint amps used to do this (and were criticized for it). This apparently is without really tightly matching the FETs, but the gate voltage/current must be matched well and the Vgs should be as well. I measured Vgs on this, and while it is matched well between pairs of devices (N-ch or P-ch), it is not between the two types. I don't see any example schematics around either. I wonder what would happen if I decreased the ballast resistors to something like 0.1 ohms...

What I/V stage is that? Sent from my iPhone using Tapatalk

Thanks Kevin! The original DynaFET used a 100R input resistor (plus 100k to gnd), with a 1K/100R feedback resistors. I've changed these to 10K/1K (left the 100R input alone). The SS balanced DynaFET showed 200K/10K for the feedback resistors. Sent from my iPhone using Tapatalk

Failure finally; switched to the std. 1K/100R feedback loop, and getting oscillation with the crap phones plugged in only when the volume is all the way down (or nearly so). Turn it up and it goes away. This looked nasty though (nice sine wave), and appears to be the right channel only causing it (unplug right output and it goes away). About 4.5MHz, 17Vpp. Also, plugged in my load box. 33R looked ok, but different oscillation with the 330R. I guess I'll just stick with the 10K/1K feedback, and figure out what to decrease the compensation to. Kevin: any issues with increasing the actual feedback resistor values 10x over your design? In poking around, I didn't get a sense of how you determine the actual values, just the ratio. The balanced dynafet design went way above this (200K/10K), though I suspect that was because of the THAT340 input.

Someone more versed can probably help you more. Since the HD is dead, no recovery partition on it to start up from (and not sure how far back on OSX that went anyhow). What version of OSX were you running? Do you have the system DVDs (or whatever they are)? This page may be of some help: http://www.idownloadblog.com/2016/02/24/how-to-start-mac-recovery-mode/

Documenting how these are configured: Vbe multiplier: R17-R18: 3.3K R62: 1K VR3: 20K R19-R20: 2K Mods: Cordell zobels: 100pf / 90.9R from gate to ground (Cordell uses 39pf / 100R) Fair-rite ferrites (2773009112)) in series with gate resistor (cut gate traces) Gate stoppers: 47R Current feedback loop: 10K / 1K / 10pf (R55 / R56 / C1). I will try going back to the stock 1K / 100R on this. I would not even consider using the mid feedback point; last time I tried it (after board was working), it oscillated badly with no phones/output plugged in. I am going to solder the jumpers in place on this.

It isn't outdated nor redundant. It is the full-size SS Dynalo, vs. the mini that Kerry did the board layout for. The schematic you posted above is for the mini.

Yes, that is the mini. The kgdynalobal9 is the full size, but is also SMT for most of it. Use with the GRLV (or Amb sigma22, etc.) PSUs, normally at +/-20V. The kgdynalobal files seem to use SMT transistors, but thru-hole resistors. These are all full size; I'm not sure which is considered to be the latest. The kgdynalobal9.zip was what was used for the recent group buy, here. 6/5/2015 9:49 AM 242761 kgdynalobal5.zip 11/2/2016 11:09 AM 4298 kgdynalobal9.PKP 2/6/2016 8:25 AM 325771 kgdynalobal9.zip 11/13/2016 6:34 AM 88083 kgdynalobal9g.zip 11/12/2016 4:20 PM 79877 kgdynalobal9G2.zip 6/23/2015 6:59 AM 237220 dynalobal12.zip 6/23/2015 6:59 AM 235328 dynalobal13.zip 6/25/2015 4:22 AM 236564 dynalobal15.zip 6/25/2015 4:22 AM 252016 dynalobal17.zip

Both the ssdyna 15 and 17 files are SMT, didn't check the others. The top image of the 15 file is shown below (dynalobal15.zip) The MPSW thru-hole transistors were discontinued, forcing the move to SMT.

Schematic for the SMT SS Dynalo, not the mini.

That sounds similar to a problem I had with one of mine (2 pages back in this thread) when I brought it up on a variac. D1 was lit, but D9 not. Input voltage was too low and the opamp was locking up. Is your transformer actually putting out 16Vac? That should be plenty for a 15Vdc output.

Same number of output devices (8 per +/- channel, or 16 per L/R channel). Mini uses 16 PZTA06/56 and 6 MMBTA06/56. Full uses 22 MPSW06/56 (thru-hole, not available anymore), or 22 PZTA06/56 (16 output, 6 biasing/VAS) for the SMT version (current). I don't see a schematic for this version (the thru-hole schematic is still on Kevin's site).

Got both boards up and running with mods 1 and 2 above. Ran RMAA on it at 150mA, 100mA and 75mA bias. I think 150mA is probably the best. See what any of you think of the plots attached. Also brought my T50RPs down and listened to some tracks on it. I think this may be my favorite amp! I'll have to do more listening though. Dynafet_both_75_330L.pdf Dynafet_both_150_330L.pdf Dynafet_both_150_33L.pdf

Thanks all, got a couple of BOMs now. You guys don't like putting the output devices in your BOMs, eh? EDIT: also, can MJF15030/31s be used in place of the MJE15030/31? Specs seem the same with the exception of rated for 36W instead of 50W.

Does anyone have a BOM for this (SS Dynahi)? The one that Vortex posted in the 1st post is blank, and I suspect for the Toshiba boards anyhow. Lil Knights also was for Toshiba parts.

Happy Birthday Nate! Sent from my iPhone using Tapatalk

I know the thread is 15 pages, but this info is in here multiple times. Sent from my iPhone using Tapatalk

Yes, you only change one of the two resistors. ((R8+R7)/R7) x Vref ((750 + 1500)/1500) x 10 = 15 Sent from my iPhone using Tapatalk