Building a Pearl 2

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rvanloghem

Member
Joined 2016
I want to thank everybody for the knowledge and tips/trics concerning building a Pearl 2.

I've built mine this month, and surprise, surprise.... it is dead quiet and worked straight out of the box! (great thanks to 6L6 for his great grounding scheme)

Now I do have some questions which I hope some of you might help me with.

Setting the DC offset is pretty hard to do, I've read that in the forums.

For me the voltage swings somewhere between -4mv and +4mv (with the lid open) I can't seem to get it to 0 exactly... (but just looking at my DMM it without it being connected to the pearl 2, it doesn't stay exactly on 0mv as well....).
Is the swing in voltage normal?

Second question;
On the RCA outputs there is a slight DC voltage, but really just from -0,1mv to 0,1mv range. Is this ok? (I do have a DC protection circuit on my Pass F5 amp)

And last question;

I have a Lehmann Black Cube statement, which is pretty good with my Ortofon Quintet Black MC.
But comparing it to the pearl 2 especially in the lower and mid frequencies is a whole lot better! But I do "feel" I'm missing some of the high frequencies, some "air". Is that something I am able to change by changing the load resistor? (currently only set for 47K)

thanks a lot!

Robert
 

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M

McQuaide

Member
Joined 2011
rvanloghem said:
I want to thank everybody for the knowledge and tips/trics concerning building a Pearl 2.

I've built mine this month, and surprise, surprise.... it is dead quiet and worked straight out of the box! (great thanks to 6L6 for his great grounding scheme)

Now I do have some questions which I hope some of you might help me with.

Setting the DC offset is pretty hard to do, I've read that in the forums.

For me the voltage swings somewhere between -4mv and +4mv (with the lid open) I can't seem to get it to 0 exactly... (but just looking at my DMM it without it being connected to the pearl 2, it doesn't stay exactly on 0mv as well....).
Is the swing in voltage normal?

Second question;
On the RCA outputs there is a slight DC voltage, but really just from -0,1mv to 0,1mv range. Is this ok? (I do have a DC protection circuit on my Pass F5 amp)

And last question;

I have a Lehmann Black Cube statement, which is pretty good with my Ortofon Quintet Black MC.
But comparing it to the pearl 2 especially in the lower and mid frequencies is a whole lot better! But I do "feel" I'm missing some of the high frequencies, some "air". Is that something I am able to change by changing the load resistor? (currently only set for 47K)

thanks a lot!

Robert
Click to expand...


+ and - 4mv is excellent, mine tends to drift a bit. Loading a Quintet Black at 47K is your problem, it's supposed to be at around 20-50 ohms! No wonder it's rolled off.
 
6L6

6L6

Moderator
Joined 2010
Paid Member
Robert, Andrew,

Your builds are looking really nice, well done! It's always great to see people having successful projects. It sounds like your grounding is quiet, so the big fight is over! Hooray!

If I may suggest a few things for lowest noise and best performance;

1) Rotate the PCBs 90deg (Andrew) and 180deg (Robert) and get the input stage close(r) to the RCA plugs. Short input leads, long output leads are quieter.

2)Run all wires as close to the chassis as possible. Remember that there is a lid to the chassis, you can run the power up and across the top and then down to the power inputs. (you don't have to, just remember there is more than one way to route things)

3) Run the center ground wires (the lone black one near the small electrolytics) under the PCB

4)The LEDs are not lights, they are a bias voltage reference for the output stage, having them on fly leads will only pick up noise.

5) When possible, attempt to have power and signal wires cross at 90deg angles.

6) Phonostages, being the most gain in a single box in the entire chain, AND having an intrinsic noise penalty due to the cartridge/input stage interface that you can't do anything about, neatness really counts in wiring. As short as comfortable, run tight to the chassis, bundled together when appropriate. Zip-ties are your friend. The Pearl can have incredibly good SNR, it's absolutely worth the effort. :D


728801d1547413680-building-pearl-2-a-img_4643-jpg


729745d1547746085-building-pearl-2-a-img_0588-jpg
 
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rvanloghem

Member
Joined 2016
Thanks a lot for the replies!

Will try different resistor values asap.

6L6 I will make the modifications... (can't believe it will be even more quiet then it already is)

btw. It already is a lot more quiet then the Lehmann. The Lehmann has a lot more hiss. The Pearl 2 has some hiss if I turn the volume waaaaaaaaaaaaaay up. (I wouldn't want to listen at those volumes anyway as it might bring the whole house down)
 
L

Lbcyclist

Member
Joined 2014
Dennis Hui said:
Hi Lbcyclist,

I was actually thinking of modifying the R part on your power supply board,
where you currently have the 1 ohm resistor.

If you currently have +/34V with both boards attached and assuming
a total 100mA draw (going by the Pearl 2 documentation; you can
verify by measuring the voltage across that 1 ohm resistor), you can
lose a couple more volts, for example, by changing out the 1 ohm
and putting 20ohms/1W in its place.

Cheers,
Dennis
Click to expand...

Hi Dennis,

Thanks for the advice, I replaced the 1Ω resistors in the power supply with 20Ω ones.

Now getting 33.5V on the negative side and 31.9V on the positive side. Voltage drop on the new resistor is 1.0V on the negative side and 1.8V on the positive. Would that be expected given the higher draw on the positive side?

In any case, thanks for the help!
 
R

Russellc

Member
Joined 2003
Paid Member
Eric said:
I used the taller sinks that WBS linked above. They don't get warm at all, though my linear power supply delivers about 27v to the on-board regulators, so there isn't much excess voltage to burn off. A bit of thermal paste is always a good idea for sinks, as Jim indicates.
Click to expand...

Same here, l like that style of sink, no heat...likely overkill.

Russellc
 
6L6

6L6

Moderator
Joined 2010
Paid Member
Manolo47 said:
Is there an updated complete parts list somewhere? Thanks!
Click to expand...

There is the schematic... The original parts list gives parts numbers, although many are obsolete, but certain physical parameters will be there.

This is a big challenge of projects like this that live a long time, the parts get harder to find.

Nothing on this board is particularly hard to find suitable new production parts for. Do you have any specific questions? We're happy to help. :D
 
WBS

WBS

Member
Joined 2007
Mouser BOM as of Jan. 2019

Here is what I have so far from Mouser.

I've increased the quantity of items that are static sensitive or when the extended price was about the same as the smaller qty.

I'll post my DigiKey list soon.
 

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WBS

WBS

Member
Joined 2007
DigiKey BOM Jan. 2019

TRIMMER 5K OHM 1W PC PIN TOP ADJ: Part Number ‎3290W-1-502-ND‎

RES 1K OHM 1/4W 1% AXIAL: Part Number ‎1135-1401-1-ND‎

CAP FILM 100PF 5% 100VDC RAD: Part Number ‎1928-1039-ND‎

I forgot to add 2 female XLR panel mount sockets for the power cord.

Oh, and I didn't add the power supply caps 'cause I'm still deciding what to do.
 
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B

bkdog

Member
Joined 2005
I know it happens here sometimes, but please do not use an XLR connector for power... They are signal connectors and not rated for power. A Powercon connector is better, or a Tuchel etc. There are many better options.

I work in pro audio and having power on an XLR connector is an accident waiting to happen.
 
WBS

WBS

Member
Joined 2007
bkdog said:
I work in pro audio and having power on an XLR connector is an accident waiting to happen.
Click to expand...

I don't question your experience.

However, we're talking about ~30V at 100mA. Is that too much of a strain on an XLR rated at 94V? :confused:

If it is, spending an extra $30.00 for power connectors would be worth it.

Reading through the thread there appear to be more than a few Pearl 2 powered using XLR connectors.

Has anyone had a problem with their XLR connectors in the 10 years the design has been around? It would be helpful to hear from you if you have.
 
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