Pars

Cool! Sent from my iPhone using Tapatalk

Happy birthday Dan! Sent from my iPhone using Tapatalk

Yes, definitely use heavier copper for these. I was just saying that 1oz for normal boards (non-high current/voltage) is normally fine.

I would question his reference material as well. To me, reference material is something like a symphony orchestra in a hall that you have been in and know. For his material, was he at the recording sessions and knows what it sounds like? His reference system also seems to be over processed. Must be a lot of a/d/a going on there. Sent from my iPhone using Tapatalk

Happy Birthday Al! Sent from my iPhone using Tapatalk

I've never had problems reworking 1oz boards (several cycles) if they are quality fab boards. 2oz is probably better though I don't know if 2oz is bonded to the substrate any better than 1oz is. I guess the additional copper must have some effect. Today's boards are a far cry from some of the '80s shit, where traces would lift if you looked cross-eyed at them Sent from my iPhone using Tapatalk

Checked the actual board (marked the same as yours Kevin, from the group buy, lovely black soldermask), and the 2 electros up by the MOSFETs run from V+ to V-. I'd have to refresh my memory on bypassing, as I recall this being done with opamps before, but I would think to gnd would be better? Still running 1 pair of devices, removed the 1K gate stopper and put sockets in. With 221R everything looks fine, other than it is resembling lampizator construction technique. Marc: thanks for the Cordell link. I read quite a bit of that, plus took a look at his book on amplifier design. It appears that he always uses gate zobels consisting of 39pf->100R->gnd on his amps. He seemed to indicate that he always uses them.

Very clean soldering work John! Nice! Did you do any matching?

No no Steve... some of us might like to see what kind of fucked up shit he is up to these days

Yes, but it takes a $200K table to run a high $$$ cart into the label...

^ I'll have to check the actual board. The Eagle files I have, which are not quite the final board. show the two 220uf/100V as going from V+ to V-. I've been trying to update the Eagle file so it more or less matches. The combo SMD/TH resistors he created are a massive PITA in this though, requiring 2 connections on each end.

Happy Birthday Colin!

Happy Birthday Steve!

Sure, I'll give it a try. I noticed that Borbely was using 100R or 221R on these devices. Any thought on the zobel fixing this? Band-aid? Cheating?

More interesting. I pulled 1 pair of devices. Still oscillating. Actually, now it was oscillating with the volume all the way down, would quit when turned up slightly, then back to oscillating as volume went up. Pulled the replacement 2SK214 and put one of the originals back in. Still oscillating, same as before. Pulled the ferrite chips I had put in and replaced with a couple of these: http://www.digikey.com/products/en?keywords=240-2437-1-nd Not oscillating! Hmmm. Of course Digikey doesn't have those anymore and I don't have 8 of them (5). Shit. Looks like I ordered 10. Will have to see what I used them in... flea clock boards probably.

Happy Birthday Ed! To a healthy future! Sent from my iPhone using Tapatalk

Is this a Danny B meet? That guy even still around? :evil: Sent from my iPhone using Tapatalk

Hmmm, re: caps. Does that actually do anything? Thinking of changing these to ground? I'm running 4 devices (2 pairs). Sent from my iPhone using Tapatalk

Someone might have posted this before, but remastered audio, live 1973 performance

One other question... looking at the board layout for these, I noticed that the 220uf/100V caps up by the FETs are run from V+ to V-, not V+ to GND and V- to GND. Is this correct?

Ran some Bode plots in my spice simulation. Not completely sure how to interpret these yet. Haven't installed the zobels yet either (in the actual amp). I have them in the simulation; I'll have to run some of these with/without them and see what differences I can see. At any rate, some below: Standard 1K/100R feedback loop, 10pf compensation cap Same 1K/100R feedback, 33pf compensation 10K/1K feedback loop, 10pf comp. 10K/1K feedback loop, 5.1pf comp

A cap farm! That one would be a fun recap, though I doubt you guys keep stuff long enough to need to do that Sent from my iPhone using Tapatalk

Yes on both questions. Pm me if you would like a board. Sent from my iPhone using Tapatalk

Yes, very nice tribute Brent!

The ferrite beads seem to have no effect. I decreased the feedback resistors to 10K/1K (still the same 10pf compensation cap). Oscillation is still there, though I now have to turn it up a bit further before it begins. Waveform looks slightly different as well, but I didn't recheck frequency. The spice simulation doesn't behave exactly like the real world circuit (big surprise), but does seem quite picky regarding the compensation cap. The 10pf works well for the std. 1K/100R feedback network. 5.1pf seems to work well for the 10K/1K network, and 1pf up to about 4pf works for the 100K/10K network. I'll play around with the compensation cap in the actual circuit. Now for the interesting part: since this only occurs with some crappy phones plugged in, I tossed a zobel together with a series 20R MF resistor and a Wima 0.047uf cap. This completely killed the oscillation. I'll get some more appropriate parts per Amb's b22 parts list and install. I don't know how to do Bode plots nor take the measurements necessary for one in order to try to figure out exactly what is going on in the amp. At least that is my guess as to what it would take to really nail down the actual cause. Any advice here appreciated!