Pars

It lives! Fired it up (not literally) last night, and things seem good. Takes around 4 hours to adjust bias and make sure it is stable, so will do that this week sometime. I guess the charred portion will just stay like it is as there is no plus to removing the board to clean it up as best I can, but lots of negatives as in 8 MOSFETs I could blow up...

I didn't get mine from these guys, but you could try them. Also, I see the DA models all over amazon; just need to weed out the plastic LX ones. Jewelry Tools - SEP Jewelry Tools of Chicago, Inc. Also, be aware the the higher power ones (like the DA10s I have, 3.5X) have a pretty low focal length (~4") which makes soldering, etc. a bit challenging. I've meant to get another lower powered lens plate for mine, but just haven't gotten around to it yet

He had posted some HF-worthy short post (KRmathis-like), to which I replied that he might want to read the welcome PM. I never saw what he posted in reply, but assume he must have posted something? Pity

I'm not Miguel, but have used these for a few years now. You can get them from Amazon, etc. They apparently have a plastic lens version out now for less money (LX models), but I would go with the glass lens DA models. Note that you can get additional lens plates for different magnifications, and they are easy and quick to change out. The product is by Donegal and is called an Optivisor.

I'd read your welcome PM if I were you...

Had a chance to do some more critical listening with my K601s to this the other night. Bias scheme is the new transistor bias. I decreased the CCS to 65 ohms; measured drop is 0.94V, so 14.5mA. I like this biasing the best of all that I have tried; thought the sound was quite natural, drove the phones well. Possibly a touch soft in the bass compared to my dynalo, still sounds slightly darker also, but really pretty close overall. A keeper.

Audiolab, design by John Westlake. I'd like to hear these. Sabre32 DACs, really reasonable price. Audiolab 8200CD and 8200CDQ CD Players - eCoustics.com A forum that John has been posting on as of late: At last...................... - Page 29 - pink fish media

Thanks guys. Fortunately, the damage is in the APC section (some sort of protection circuit that worked real nice, as you can see ). The two 8-pin DIP sockets you can see were populated by a couple of chips that split in half... been quite awhile since I have seen that. That portion is disabled now, with only the actual output circuitry still connected. The output FETs for these are unobtainable, and must be very closely matched. It appears they are OK, but I'll find out presently. I don't have the schematic, so am depending upon a couple of ex-Counterpoint service people on diya to guide me right now. Feels funny flying blind.

Seems like a lot of the things where I work only work with IE. IT dept. has their heads up Redmond's ass so far... inextractable. This made me laugh: Executive: Microsoft a dying consumer brand | Chicago Breaking Business

Variac (thanks for the rec Nate!). Variable AC Output Transformer MAX.20A (Metered Variac) - eBay (item 120631655275 end time Nov-07-10 14:34:08 PST) Now I just need to work up the nerve to use it on the arc welder power amp I am trying to fix for my brother. The one that was trying to start his house on fire

Another point that they touch on is if you are replacing a lossy cap with a good cap plus a series resistance of 0.8 ohms (their example) to compensate, why bother? I guess you would have to try it, or better if someone was able to analyze the FR, phase etc. changes that you brought about with your tweaks. And of course, listening.

^^ I recommend this post...

Late, but congrats, Mike!

Implemented the new bias scheme and ran some tests yesterday. I used some BC556C's that I had on hand, as well as some green LEDs which measured ~1.82Vdc. Voltage at the emitter is ~2.5Vdc. I was finding that the left channel was very sensitive to the particular LED in place, and not sure why? The first one that was in was showing a much higher threshold level in RMAA than the right channel. I tried swapping the tubes L-R, but no change. Changing out that LED resulted in the channels being much more closely matched. THD is still slightly higher than with the previous bias scheme (Blue LEDs) as well as most of the previous schemes not involving higher CCS current. I haven't tried listening to it yet. EDIT: one question: why would you not want to jumper the transformers to the anode instead of ground? Seems like this would be similar to the original instructions using LED bias? EDIT2: I did not do the extra credit of the cap

Happy Birthday Marc !!!

Not sure if any of this would be of interest to you Kevin, just did a search on Craigslist... HP3582A Audio spec an., HP8165A signal source, Hitachi V-423 o-scope Also, are Philips scopes any good? http://chicago.craigslist.org/wcl/ele/2008654797.html

FTFY Good, something to do tonight since Fringe isn't on

Ooops, sorry didn't see this. I'll have to think about it. I have replaced a tweeter when I blew one playing around with a DEQ2496 , but they are a major pain in the ass to get to. I'll take a look at the dimensions, etc. and see if I want to mess with it or not. Bolt or screw pattern is different as well.

I'd re-read your PM if I were you...

Did some non-critical listening to resistor bias tonight. 56 ohm ccs. So far, I like what I was hearing. Jumpers are kind of hard to get to, particularly the one tucked in by the parafeed cap. Might want to move those a bit on the final layout.

^ Not me.

Happy Birthday gentlemen!!!

Good place to pick up a variac around Chicago? My brother's Counterpoint power amp decided it might be a good time start on fire , and I am trying to fix it (with some excellent help on diya). I'll need a variac of bring it up slowly to determine whether or not the output devices are still good. Something around 10A would be great, though I was advised that something smaller (s low as 2.5A or so) will work as long as I don't take it up to full voltage on the variac.

No, using 4.7uf Clarity caps... I may try going to the 56 ohm CCS and switching the jumpers to see what that sounds and measures like. Or go 65 ohms like Doug is using. I think I have some 499 ohm resistors around to put in parallel, could try that as well.

HEY! I resemble that remark Have done some listening with Blue LEDs in, but no comparison with going back to the Red LEDs, going to higher CCS current/resistor bias, etc. I did A/B it with my Gilmore and they are pretty close. The l'esp is a bit darker, I can hear the increased distortion at times, but not bothersome. I do prefer the Gilmore, but that might just be me. This was driving AKG K601s and using classical (Shosty and Stravinski). Using my Shure 840s, I listened to some Simple Minds... was fun; a bit of a bass hump with these (whether it was the phones or the amp ??) Didn't notice a bass hump at all with the AKGs.