Pars

Looks nice Michael, and agreed on the socket. Having it machined to recess into the front panel might look better as well, but looks great for a prefab case! Here are a couple of pics of mine so far (the usual not even close to being done ) I took Kevin's suggestion and wired the pass devices off to the heatsink for the GRLV.

Happy Birthday!

Thanks. Like Michael has experienced, even with matching (hFe and resistors), the DC offset without the servo is 66mV (for me), consistent in both boards. The servo brings it down to ~1-2mV. Biasing is at 200mA across the 1 ohm resistors. Q21 (the MJF15030 driven by the 7K resistor and the pot) seems to be running rather warm, but I'll need to recheck that. Overall, the amp doesn't run as warm as the Dynafet does. Running it at +/-30V currently, GRLV. Sound wise, from a short listen, this didn't sound as "fast" as I was expecting. It still sounded very good. The highs perhaps sounded a little recessed. This is all with the 25K pot. I'll try it with a 10K Alps today and see what difference that makes. Damn easy to build and get running though; pretty much came right up. As long as you don't make any errors stuffing the board, it works. Yes, I'm looking at you Dynafet

What would the sonic effect be of running a 25K pot with this? It is what I have (TKD) in my DynaHi/DynaFET and I was planning on running these boards in that. I know you usually spec a 10K. Thanks!

Happy Birthday!

Happy Birthday!

That one might work. Also I came across this as a replacement: PBHV8540Z

Tossed together an LTSpice model for this (warning: I'm a Spice newbie/hack) CFP spice.zip

I wish I could use modelling software like that

RIP to David, Della, et al And RIP to Arnie Nudell (Infinity)

There is a thread about a Wayne-designed Pass Labs head amp on diyaudio right now, with pcbs being available. Sent from my iPhone using Tapatalk

I think you meant Schottky. They supposedly have lower switching noise than std. silicon rectifier diodes. Sent from my iPhone using Tapatalk

Yes

That looks right to me, but I’m no SMT expert. Sent from my iPhone using Tapatalk

Fired board #1 up tonight on a bench supply at +/-20V. Seems to be working, characteristic 58mV DC offset. At first I wasn't seeing anything across the 1R resistors, but after turning the pot clockwise, it started going up. I left it at around 158mV, which should be 150mA bias? I didn't feel any heat from the transistors, and I don't have the L bracket bolted onto a heatsink yet, so not really interested in cranking it up much. Also didn't leave it on long at all, less than 2-3 minutes.

The isolated tab. I didn't know if I had enough to220 thermal pads and shoulder washers around... I do. EDIT: Ack, Mouser. The 5K trimpots I ordered (and ordered correctly) turned out to be 25K. Label on bag was correct for 5K. Must have been a good day in order picking . They also shorted me some 560 ohm resistors, but thoughtfully provided the 4 I needed. Edit 2: I put 10K pots in with a 10K resistor in parallel. Will change to the 5K pots when Mouser fixes it.

Crap. Just noticed I ordered MJEs, not MJFs...

Happy Birthday JP!

Go back a page (April 11 post)... still haven't finished casing it yet (this winter...). Both amp boards are on the right heatsink now, and a GRLV on the left heatsink.

Which Toshibas? And it's tempting, BTW I'm just going to use my cheapie meter with hFe to see what the MJE1503xs look like instead of rigging up a jig and doing it properly.

^ I hear ya. Was struggling with trying to decide whether this would work or not. Voltage switch (115/230) with 2 transformers, and switching of the main transformer on with front power switch (e24 type functionality, but allowing line voltage selection). Relays switching both primaries of the main transformer since both would be live in the case of 115 parallel connection. Maybe I'll just use a Meanwell AC-DC brick for the relay board power (ala Soren).

A brain? Sent from my iPhone using Tapatalk

Does it do hfe? If not, it would be kinda worthless for matching transistors. Not clear from the write up what exactly it does do. Sent from my iPhone using Tapatalk

Yes, I’ve used Arrow in the past year for some things, as well as OnlineComponents, though they have a $50 min order. They also have some Pana TS series caps, which makes it worthwhile Got an update from USPS... order out for delivery. This is the first time I’ve had trouble with Mouser... their Econ shipping normally arrives in 2 days. Sent from my iPhone using Tapatalk

Mouser is pissing me off... placed an order on Sunday night. It didn’t ship until late Tuesday, using that UPS Innovations crap. Supposedly in town being transferred to USPS, but don’t know what’s up with it or when it will be delivered. I was hoping to get the CFP boards at least in a testable state this weekend. Fuckers... Sent from my iPhone using Tapatalk