THANKS!
Thanks to everyone who analyzed this for me and helped me see what's going on. I think it's gotta be the 9610.
I think I was a bit blinded by the "it can't be...." kind of thing.
"These are all new parts, it can't be bad MOSFETs..."
"Both channels show the same symptom, it can't be that BOTH 9610's are bad..."
And, actually, since this project sat unbuilt for a couple of years in the closet of the guy I bought it from, and the 9610's were not in conductive bags, it is entirely possible they are both open.
(I use a Hakko soldering station, it's grounded, and I did the work during humid summer months, so I don't think I blew these out- but replacements are coming and when I put them in I will be extra-careful)
Thanks to everyone who analyzed this for me and helped me see what's going on. I think it's gotta be the 9610.
I think I was a bit blinded by the "it can't be...." kind of thing.
"These are all new parts, it can't be bad MOSFETs..."
"Both channels show the same symptom, it can't be that BOTH 9610's are bad..."
And, actually, since this project sat unbuilt for a couple of years in the closet of the guy I bought it from, and the 9610's were not in conductive bags, it is entirely possible they are both open.
(I use a Hakko soldering station, it's grounded, and I did the work during humid summer months, so I don't think I blew these out- but replacements are coming and when I put them in I will be extra-careful)
Glad to see the issue fixed.
The guy you got the IRFs from should have known that those parts are damaged by static spikes, hence the non-conductive bag they're originally shipped in
Oh, well, now you have a very nice regulation working.
I also would recommend to put some RC networks across the diode bridges of the PSU, like "100nF+1R2" series in parallel to each diode. If you built the two channel supply shown in the Pearl pdf, you'll need 8 x 100 nF and 8 x 1R2 1/4W resistors.
Best,
nAr
Attachments
Snubbers
I didn't use the circuit in the Pearl article. I used HEXFREDs and I do have snubbers across them to dissipate the noise from the resonance formed by the secondary's leakage inductance and capacitance. Thanks, though. It's a useful thing to use in any audio power supply, especially power for low-level, high gain circuits like power supplies.
I didn't use the circuit in the Pearl article. I used HEXFREDs and I do have snubbers across them to dissipate the noise from the resonance formed by the secondary's leakage inductance and capacitance. Thanks, though. It's a useful thing to use in any audio power supply, especially power for low-level, high gain circuits like power supplies.
I meant to say,
"I didn't use the circuit in the Pearl article. I used HEXFREDs and I do have snubbers across them to dissipate the noise from the resonance formed by the secondary's leakage inductance and capacitance. Thanks, though. It's a useful thing to use in any audio power supply, especially power for low-level, high gain circuits like power supplies FOR PHONO PREAMPS"
"I didn't use the circuit in the Pearl article. I used HEXFREDs and I do have snubbers across them to dissipate the noise from the resonance formed by the secondary's leakage inductance and capacitance. Thanks, though. It's a useful thing to use in any audio power supply, especially power for low-level, high gain circuits like power supplies FOR PHONO PREAMPS"
I believe your resistor values are too small to be effective as snubbers. Here is a good article that shows how to calculate snubbers for individual circuits, depending on the transformer's leakage inductance. Btw. one snubber circuit instead of 4 would be enough: http://www.hagtech.com/pdf/snubber.pdf
Yes, I personally use MUR-160
If I recall, exact resistor value is 1R8, that's all I got ... X-formers are 10VA/24V square types. Because the pre itself consumes less power than Pearls, also 1 supply / reg per channel
nAr
WEIRD NEW PROBLEM WITH PEARL
This is a strange one.
With Shure V-15 / type III into the Pearl all is well. Sounds good, at least as good as a V15 sounds anyway.
With Dynavector 10x5 into Pearl, there is a serious (9 dB) channel imbalance at 1,000 Hz.
With Dynavector 10x5 into Bottlehead Eros, or Parasound Z-Phono, NO CHANNEL IMBALANCE.
So, for some reason the Dynavector shows a big channel imbalance into the Pearl, but not into other preamps; while using the V15 with the Pearl shows less than 1 dB of imbalance on the 1 kHz band on my test LP.
?????
Double-checked my input load resistors, they are 47k, this should work great with the Dynavector.
Not sure I can understand how this could even be possible, outside of some odd loading effect?
It's too bad, too, because the Pearl is really SUPER QUIET compared to the Bottlehead and the Parasound doesn't really sound all that great.
This is a strange one.
With Shure V-15 / type III into the Pearl all is well. Sounds good, at least as good as a V15 sounds anyway.
With Dynavector 10x5 into Pearl, there is a serious (9 dB) channel imbalance at 1,000 Hz.
With Dynavector 10x5 into Bottlehead Eros, or Parasound Z-Phono, NO CHANNEL IMBALANCE.
So, for some reason the Dynavector shows a big channel imbalance into the Pearl, but not into other preamps; while using the V15 with the Pearl shows less than 1 dB of imbalance on the 1 kHz band on my test LP.
?????
Double-checked my input load resistors, they are 47k, this should work great with the Dynavector.
Not sure I can understand how this could even be possible, outside of some odd loading effect?
It's too bad, too, because the Pearl is really SUPER QUIET compared to the Bottlehead and the Parasound doesn't really sound all that great.
If it's not a cable/solder issue, try experimenting other loading values, tech datasheet says > 1k, so you can experiment from that value
If problem is still, maybe it's a cartridge tracking problem on the cut groove, test LPs are known to be excellent to reveal those kind of things.Maybe confirm with another Dynavector that problem is still. Maybe unmount - mount of cartridges can lead to connections problems, those are tiny wires after all
It's rather an external problem not Pearl internal.
Regards,
nAr
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If problem is still, maybe it's a cartridge tracking problem on the cut groove, test LPs are known to be excellent to reveal those kind of things.
Maybe confirm with another Dynavector that problem is still. Maybe unmount - mount of cartridges can lead to connections problems, those are tiny wires after all
It's rather an external problem not Pearl internal.
Regards,
nAr
Well, I would think if it were tracking / setup, cartridge lead connection issue, etc, then the channel imbalance problem would be the same with any phono preamp. However, using the 10x5 with Parasound Z-Phono or Bottlehead Eros phono stages, the Dynavector has NO channel imbalance problem... the only cartridge / phono stage combination that shows this problem is the Dynavector / Pearl.
...and the Shure with the Pearl, channels are very well balanced.
A real head scratcher.
Just to be sure; you use same turntable for all tests ? just swapping cartridges ? and same phono cord between turntable and phono pre ?
Best,
nAr
http://www.passdiy.com/pdf/pearlphono.pdf <= ORIGINAL PEARL
http://www.passdiy.com/pdf/PEARL%202.pdf <= PEARL 2
-Bill