No worries. I think the difference between channels at the first stage is due to different Jfets Idss (6mA and 7mA). The other difference (20V, 22.5V) may be because of LEDs? Please check also voltages coming out from the power supplies, should be +-24V.
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PEARL 2 power supply
I have several spare power supplies from another project as well as two 400VA 22va-0-22va transformers to match them. Bit over the top for the transformers but I am not using them.
The power supply I am referring to is an SKA Audio class A PSU-model GB50S.
You can check it out on the SKA-Audio.com
I am wondering if I could use these parts for a PEARL 2 powers supply.
Thank you.
I have several spare power supplies from another project as well as two 400VA 22va-0-22va transformers to match them. Bit over the top for the transformers but I am not using them.
The power supply I am referring to is an SKA Audio class A PSU-model GB50S.
You can check it out on the SKA-Audio.com
I am wondering if I could use these parts for a PEARL 2 powers supply.
Thank you.
Pass DIY Addict
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That power supply will certainly work, though 400VA is overkill several time over 
22v is a good voltage for secondaries. The total draw of the Pearl II is about 42mA on the negative rail and about 84mA on the positive rail for both boards combined.
You'll definitely want to keep a 400VA away from the boards...
22v is a good voltage for secondaries. The total draw of the Pearl II is about 42mA on the negative rail and about 84mA on the positive rail for both boards combined.You'll definitely want to keep a 400VA away from the boards...
Help
I got all parts and populated my boards. Fired it up and I had insane gain. I could pick up radio stations by touching the cartridge drop bar. It was banging +/- 20V with a little clipping but enough good music came through to get me inspired with volume at zero. Figured it out that I forgot to jump R14 (hey it wasn't a part I needed to order so forgot it). I had the boards mounted pretty well with cables already soldered in so added jumpers from top and soldered front of board. Fired it up and got zero gain one channel the other channel lasted 20 seconds with too little gain so I turned it way up.... then oscillate to where I learned a high current capable power amp can trip a 15 amp house fuse. Now no gain, no hiss, no output at all. Power regulation looks Ok. Any guesses to what I fried and need to replace?
I got all parts and populated my boards. Fired it up and I had insane gain. I could pick up radio stations by touching the cartridge drop bar. It was banging +/- 20V with a little clipping but enough good music came through to get me inspired with volume at zero. Figured it out that I forgot to jump R14 (hey it wasn't a part I needed to order so forgot it). I had the boards mounted pretty well with cables already soldered in so added jumpers from top and soldered front of board. Fired it up and got zero gain one channel the other channel lasted 20 seconds with too little gain so I turned it way up.... then oscillate to where I learned a high current capable power amp can trip a 15 amp house fuse. Now no gain, no hiss, no output at all. Power regulation looks Ok. Any guesses to what I fried and need to replace?
Insane gain -- what type cartridge are you using? Pearl is designed for moving coil. You may also have used incorrect Rg and Rf.
The output MOSFET is already cited as the issue -- buy several,
or you can just scrub the stock output section and use this OPA604 which will happily run on the high rail voltages:
Pearl Two
Gain
Koetsu Black vintage 1980 which is fairly high output moving coil 0.4mv. Without any jumper or resistor in R14 gain is infinity and beyond. Not playing music I could hear change in output noise if got within 6 inches of turn table and if touched forearm I picked up radio exceptionally well. My turntable lacks ground wiring (first generation Oracle Delphi). With jumper in the gain was not enough clearly with need to have volume near max to listen (which is when oscillation started)
Koetsu Black vintage 1980 which is fairly high output moving coil 0.4mv. Without any jumper or resistor in R14 gain is infinity and beyond. Not playing music I could hear change in output noise if got within 6 inches of turn table and if touched forearm I picked up radio exceptionally well. My turntable lacks ground wiring (first generation Oracle Delphi). With jumper in the gain was not enough clearly with need to have volume near max to listen (which is when oscillation started)
pictures coming
Digital camera is on vacation with another family member.
Is there such a thing as a table of expected voltages at various points to help trouble shoot for failed parts?
This was working without R15 - just with way too much gain. Put in jumper and it was not enough gain - but only in one channel, the other was dead and it worked until I pulled out RCA without powering down and had huge oscillation scream then both channels down now.
Digital camera is on vacation with another family member.
Is there such a thing as a table of expected voltages at various points to help trouble shoot for failed parts?
This was working without R15 - just with way too much gain. Put in jumper and it was not enough gain - but only in one channel, the other was dead and it worked until I pulled out RCA without powering down and had huge oscillation scream then both channels down now.
camac
Before you think I'm brain dead... my other phono preamp is an ancient Mark Levinson ML10a (1979 era) which uses CAMAC connectors. Camac stands for: Computer Automated Measurement And Control. It's an IEEE-standard (583). It has a wonderful feature over RCA jacks in that the ground is the first contact and so you never get that loud buzz you get when you switch connectors without powering down in RCA equipment. You just plug them in. There was also no on-off switch on the ML so never needed to power down to switch equipment. It was good enough I've kept it for 39 years! The power supply on the ML is sadly failing and it cycles on and off hence my need for a new phono pre-amp (no swapping out capacitors in power supply did not fix the power supply).
Before you think I'm brain dead... my other phono preamp is an ancient Mark Levinson ML10a (1979 era) which uses CAMAC connectors. Camac stands for: Computer Automated Measurement And Control. It's an IEEE-standard (583). It has a wonderful feature over RCA jacks in that the ground is the first contact and so you never get that loud buzz you get when you switch connectors without powering down in RCA equipment. You just plug them in. There was also no on-off switch on the ML so never needed to power down to switch equipment. It was good enough I've kept it for 39 years! The power supply on the ML is sadly failing and it cycles on and off hence my need for a new phono pre-amp (no swapping out capacitors in power supply did not fix the power supply).
