sorenb

Stumbled across this: I guess you would be able to regulate the BIAS from 350-580V using this?

@luvdunhill: nice little utility PCB ... ...could we get a PCB containing all the neat utilities? ....XLR in/out combined with alps ....the Stax jacks PCBs ... on/off switch ....bla bla, and so forth ...if someone would do the gerbers I'd do a GB on that ;o)

ok ok ... my bad .... if you build your zener string to get 580V from something that gives you 230 somewhere ....why not tap the NB from there using a few R/C's before the balast resistor? can't be more noisy than the 580V since is would be a dublicate of what is going on there ...or do I completely miss the point here?

what would be the downside of building the zener string from some values that have 280V and tap the NB from there using some r/c+r/c and a balast resistor? 130V + 150V + 150V + 150V = 580V 130V + 150V = 280V 100k/100nF + 100k/100nF + 5 4M7 as balast?

Congrats: Kingofsnake is like if the dust have only just settled before the amp emerged ;o) pretty good build you have there, even the lead for the caps got a redtube ;o)

@nopants: "Are you using a torque driver to do this? I don't know how else you'd assess how you're actually screwing things (in/up). However I'll go ahead andl note that Craig Sawyers mentioned in another thread that thermal interfacing reduces the sensitivity to torque." - I use a light but firm grib, and as soon as my fingers tend to slip I let go ... I'm pretty sure that I do not over teighten things ...

@Joamat, I guess Spritzer implies that I am screwing hard and therefore should use plastic

Birgir, that is a really nice looking rack you have ... And in rgrds to screwing, I already ordered some plastic from Mouser ...

@JimL: I believe that I've learned my lesson in that regard ) @Spritzer: "The heatsink is grounded so it doesn't make any sense that it shorts there. Also no traces too close to that spot... Weird... " Well ....maybe the heatsinks are grounded if you're done doing the mounting ... but since I was expecting something to go wrong I skipped the soldering of the heatsinks ... so even though the sinks will be grounded just by touching the side of the holes I actually manged to have a few that doesn't ... I guess that explains why I experience different readings on my DMM at the same spots after wrikling the board up side down a few times... The mark I've spotted is the only visual I could find, (apart from the two sources on the input fets) and assumed (wrongly) that the air hold edge was ground (I've checked my board and it is not) @nopants: I believe that the input fets in my Spritzer build is a pair of 170's ... and to my ears the Spritzer build sounds a bit better than mine BTW when putting on music for the first time I grabed a random CD from the box I have stoved them away in (only using NAS and good old LPs) ...turned out that it was in fact: Tower of Power's Monster on a leash ...in fact it is! @Joamat, Johnmclean: Thanks to everybody contributing to the thread I manged to pull it off.

Looking for Stax Normal BIAS teflon jacks ... the PROs are easy to find, but I haven't had any luck searching the NBs ....anyone?

Here's some pics of the situation yesterday, first the board itself, after removing the two IXYS parts, and a mark to where the short took place A close up of the actual scene of crime A pic of the insulation/screw etc ....the left parts was carrying the short, whereas the right didn't ....the washer is the 10PPSG so I guess only the "Arctic Silver 5" can be the suspect here, maybe it should be "Arc-ing Silver 5" would be the proper name for it Both amp boards has been cleaned and is back in business. Had a listen for some hours yesterday and it sounds very similar to the one very very well build edition I bought from Spritzer. It may sound less sweet, perhaps a little cold in direct comparison to the Spritzer build. There are a few apparent differences between the two: Current Sources: Mine: IXYS Spritzer: A1968 Input FETs Mine: LSK389 Spritzer: separate fets Heat: Mine: warm to the touch Spritzer: hot to the touch ... judging from the heat I guess Spritzers run at higher current than mine @DefQon: if the Arcing Silver isn't conductive I don't see how that short should ever be possible ... maybe something from the screw penetrating the washer ... but that would require some force and I don't tighten the screws that much ...just a rather soft grib and stop when the screwdriver slips my fingers @n_maher + nopants: I guess the Arcing Silver is meant to be used in PCs. I took advice and didn't check it out before hand ... I've checked everything else for this amp but the LSK389 and the Arcing Silver.learning the hard way seems to very true when fiddeling with HV.

@mwl168: Thanks for sharing your experience ... I have spent the evening listning to music from the amp, I'll adjust balance and offset and see if I experience likewise ;o)

I have balance and trim in the middle for now. One board is +-1V and the other is +18-15V ...approching 15 after an hour or so ....the latter board are +1V (-O) and -15V (+O)

Yes sir, I am already busy being 'the clean up guy' removing the stuff

@spritzer: thanks ...you were obviously right. Does it sound right that the boards are pulling 2x17mA each (the negative tends to bit a little lower) and is 15-18V DC acceptable or is it indicating that something is wrong somewhere? the other board is stable around +-1V.

OK, problem solved ... at least I think so - I might add, as my merrits fixing this beast isn't that glory. Hunting down the 16ohm and ended up at the heatsink of the IXYS parts ...the one closest to the edge...shorted to ground ...although I did use 7721-10PPSG and aluminium oxide pads ... but I also did use ARCTIC SILVER so I'm back to using white stuff only - so much for taking advice and not checking it thoroughly ... No parts seems to be fried must be Kevins current limiter that saved the rest of my day ... its up and running again.....and seems stable at 17V offset .... each board pulls approx 2x17mA...I guess it's on the low side?

Well, so much for enjoyment ... after having tested my KGSSHV for about 1½ hours yesterday ....I did the same today ....after 2½ hours ....a very loud cracking sound .... No smell, no apparent visuals to go after ....the PSU + was down to 1,2V ... removed the amp boards ... checked the PSU ...+/-457V ...did it again with 10k load on both rails ...no prob .... the I connected the amp boards one at a time .... to find that the one having the faulty LSK389 was the board having problems. A closer inspection of every transistor/diodes revealed that the everything but the LSK389 seems to work .... the soldering joints of the two Sources seems to have experience excessive heat : Any ideas to what might be causing this? After replacing the LSK389 yesterday I had an offset of 18-15V ....I compared measurments between the two boards and got approx the same values when probing around the diodes and further down that stage, so I took that everything would be ok then ... apparently not Testing the 389 itself directly on the legs, shows G(-) -> D/S(+) => OL, G(+) -> D/S(-) => 50ohms. The board doesn't seem to have shorts in the vicinity of the 389. I have tested all resistors to be measureing identical to the other board. No caps seem to short either .... Can it be the PCB itself causing this problem? BTW all boards have been cleaned for flux before using. Also after doing replacement Theres 16ohm between v+ and gnd ...

Starting the day powering up the AMPs ... light in all LEDs No, strange noises ... no arcing ... only one board had 89V DC, while the other was at 2V or there abouts. Turned out the the LSK389 was in fact the culprit, in fact the only transistor I didn't test before mounting One side had odd behavior and forced the input stage out of balance

Beautiful craftsman ship Kerry, but your knob is simply too whiny

My KGSSHV onboard is begining to materialize ... Will spend the evening populating the remainder of the AMP boards ...

@nopants, can I ask to join your PCB buy for Dynalo SMD? @Kevin: whats your opinion on adding a degenerated current-mirror to the input stage?

Can't argue that, and you may be right, that it is rather the change in current than the CCS itself that I am hearing Though I did try to match the existing current as close as possible. Anyway part of the fun doing DIY is also trying out stuff, and maybe realize that it didn't matter that much. For now In rgrds to the current in the output stage I haven't seen you recommend a sweetspot, other than commenting that one might 'get away' with 18mA ...is 18mA the sweet spot ?

Having read the SRX-revisited thread by JimL and the referenced articles by W.Jung I decided to replace the current sources in the one Dynalo I've built. From the 1st article by Jung, it seems as if that the CCS design used in the Dynalo has indeed a very good performance. However as JimL has pointed out the cascoded CCSs seems to offer even better performance. Looking at the very simple LM334 with one resistor demonstrates 20db better rejection than the LED CCS although the performance rapidly degrades past 10kHz; the cascoded LM344/2N5486 however maintain the performance above 10kHz. So, based on that I decided to try it out. First I have implemented the non cascoded LM334. At first hand it sounds like an improvement. However, not night and day difference; the sound is a bit more refined/detailed, and the soundstage as gained a bit more depth.

good one Pars ) No, did my measurement with open input .... inputs grounded its within 4mV (+O - -O) I haven't put the servos back in, but spend some time listning. My Sennheiser HD800 have never sounded better ) Done my listning using my Tact Mill. mkIII, and the Dynalo is clearly better than hooking up the HD800 directly to the speaker terminals ....much better. Thnx Kevin and Pars!

Ok. I'll leave them as is, and give a listen to hear wheather the effort was worth it ( I guess it was ;-) Many, many thanks Kevin for making and sharing your design. Also thanks to Spritzer, mypasswordis, GrindingThud, gepardcv, Pars, JimL, mwl168, and others sharing/contributing to the thread. Pics, or i didn't happen: