Pearl Phono Stage

I have just finished the boards for the Pearl Phono Stage.

How is everyone else progressing?

Following a careful final check and some voltage measurements I finally realised the split earths on the latest version of the board must of course be linked at the output.

All the parts are stock Digikey/Mouser with the expection of the 10,000 uf 50 volt filter caps which I substituted with 15,000 63 volt as I happen to have a heap of them. I also used some Black Gate 10 uf 50 volt C series caps for the output instead of PP non polarised.

Using the Fidelity Research MC with about 0.2 mv output it worked superbly. Not a hint of hum or noise.

The Pearl is very smooth and dymanic, with a very natural quality no unlike the Aleph, I could not ask for anything more.

There is just enough overall system gain with my Harman Kardan av preamp wound up 3/4 full and using U/balanced mode with the Aleph 5's.

I expect when the BOSOZ is completed there will be adequate gain margin in balanced mode to the Aleph.

I will post some pics as soon as I get it in a box.

Special thanks to Karen, Wayne and the rest of the Passlabs crew for their support.


best regards

macka:)
 
Wayne thank you so much, i was searching for a nice phono circuit for years, but they all didnt convince me. I was so happy finding the pearl that i directly decided to build it.

I finished my first pearl 3 month ago and i love the sound its very clear, quiet between the notes and has a kind of liquidity, that is far away from every cd player i have ever listened to.
I made my own layout and have made just a few changes to get more gain for my low output ZYX yarta. I changed R19 to 1k and put two 2sk389 in the output stage.
Everybody loves the sound and so im continuing with the next 3 pearls for my friends trying to make the layout smaller and nicer, the first of the three circuits is finished and the other two a progressing, maybe i need another week or so and than show some pictures.
 

macka

Member
2001-12-15 3:07 am
Australia
Pearl Service from Karen

Kaz,

When I have the box ready l'll zip your some nice hi resolution images for the Gallery (currently fabricating the Aleph 2 cabinets)

best regards

Ian.

PS I just fired up the Balanced Line Stage, Hmm she cooken just the way Muma said she would.
 
Howdy from Kansas!
I just finished the assembly on my Pearl - all parts are as specified on the "Revisionist" boards (there was some disagreement between the board and the manual).
Unfortunately, when I checked the DC coming out of my PS, it was at 50V. Turns out my AC is at 124V. Thinking this might be OK (I am not known for my patience), I went ahead and hooked up the boards to see if they would blow up. No smoke or funny smells, and some of the voltages were even pretty darn near what Wayne says they should be. Q4 and Q5, however are running at about 28.5 V on both boards (should be at 13.8 and 11.7 V, respectively).
Questions:
1) Do I need to rectify the power supply discrepancy? (yes, the pun was intentional)

2) Does the high V on Q4 and Q5 indicate that yours truly has incorrectly read something (such as the new-fangled grounding scheme)?

TIA,

Cody

PS- Thanks to the Pass Posse (the "Passe"?) for making this a relatively painless reentry into the world of hobbyist electronics.
 
reverber said:
Howdy from Kansas!
I just finished the assembly on my Pearl - all parts are as specified on the "Revisionist" boards (there was some disagreement between the board and the manual).

How long have they boards being shipped differ from the originals? I purchased mine 6 months ago or so. Hope to stuff next month.
I plan on going a little overboard on the raw power supply. But the boards will be close to the listed parts.

George








Unfortunately, when I checked the DC coming out of my PS, it was at 50V. Turns out my AC is at 124V. Thinking this might be OK (I am not known for my patience), I went ahead and hooked up the boards to see if they would blow up. No smoke or funny smells, and some of the voltages were even pretty darn near what Wayne says they should be. Q4 and Q5, however are running at about 28.5 V on both boards (should be at 13.8 and 11.7 V, respectively).
Questions:
1) Do I need to rectify the power supply discrepancy? (yes, the pun was intentional)

2) Does the high V on Q4 and Q5 indicate that yours truly has incorrectly read something (such as the new-fangled grounding scheme)?

TIA,

Cody

PS- Thanks to the Pass Posse (the "Passe"?) for making this a relatively painless reentry into the world of hobbyist electronics.
 
How long have they boards being shipped differ from the originals? I purchased mine 6 months ago or so. Hope to stuff next month.
I plan on going a little overboard on the raw power supply. But the boards will be close to the listed parts.

I think you probably have the revised boards (the ones with the split ground). IIRC, the parts difference was in the wattage of R2 and R3, which are now 3W according to the legend on the boards, but listed as 2W in the manual.

I now have my Pearls going and they actually have more gain than the phono stage of the Sansui integrated that I have. My SO says that she can hear a differnce, but she may be humoring me ;) .

Thanks to Boban for pointing out his thread where his similar grounding problem was solved.

Now to build some enclosures that are worthy of the sound. I am thinking of duplicating the look of the base of my AR-ES turntable.


Cody
 
reverber said:


I think you probably have the revised boards (the ones with the split ground). IIRC, the parts difference was in the wattage of R2 and R3, which are now 3W according to the legend on the boards, but listed as 2W in the manual.

The manual shows 2 watt, but the parts list has 3w 4.7 ohm resistors listed. BTW, I remember reading that the current draw on the Pearl was something around 40 ma per channel. I must be incorrect.
What is the normal current draw of the Pearl? I just checked some numbers and I would run a 1 watt resistor at anything under 325 ma. Since the transformer is a 30 watter, the current should be 375 ma max and less 200 ma to keep from overloading the iron.
Were the big resistors chosen for the inductance they provide? I have a handfull of round plastic encased chokes that are 10 mH, 2.1 ohm, and rated 8 mH at 1 amp DC. These look to be perfect to replace those dropping resistors. They are about the diameter of a half dollar and an inch thick.

Thanks
George









I now have my Pearls going and they actually have more gain than the phono stage of the Sansui integrated that I have. My SO says that she can hear a differnce, but she may be humoring me ;) .

Thanks to Boban for pointing out his thread where his similar grounding problem was solved.

Now to build some enclosures that are worthy of the sound. I am thinking of duplicating the look of the base of my AR-ES turntable.


Cody