Building a Pearl 2

Hello everyone,

I have a question regarding a PSU for Pearl II. Do you think it would be possible to build this using something off the shelf like a Mean Well PSU GST120A48-P1M https://cdn.shopify.com/s/files/1/1006/5046/files/GST120A-spec.pdf? The reason I ask is that this would be my first build after ACA 1.6 and I would like to avoid handling high voltage circuits as my immediate next project.

By the way, thanks for all your discussions and pictures, I think I found a new hobby that will burn a hole in my pockets :scratch2:


What if I use dual 24v PSUs like Mean Well GST120A24 to create the +24V and -24V rails and feed them to the output of 7824 and 7924 regulators on the Pearl II PCB?


EDIT: Or 48v PSU with rail splitter like this one TLE2426 The 'Rail Splitter' Precision Virtual Ground | TI.com
 
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Having finally ordered and received my Pearl 2 boards I'm interested in knowing the answer to your questions also. The GlobTech medical supply used with my B5 is dead quiet. How about something similar for this project? Or is the circuit so sensitive to noise it wouldn't work?

Anyone?
 

6L6

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The Pearl 2 requires a bipolar supply, +/- 24 V, and it needs to be few (3+) volts above 24 so the regulators can work properly.

This is not to say a SMPS won't work, on the contrary it could work very well. I'm just not sure there is one that will be of proper specifications to work in this application.
 
The Pearl 2 requires a bipolar supply, +/- 24 V, and it needs to be few (3+) volts above 24 so the regulators can work properly.

The performance of the Pearl 2 with a somewhat lower supply voltage is negligibly different. You can wire up an LM317/LM337 as +/-22V regulators, driven from a 48V SMPS with a an OPA544 rail splitter and derive almost the same result. (In fact, the LM317/337 will be quieter and have better PSRR than the LM7824/LM7924).
 

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Having finally ordered and received my Pearl 2 boards I'm interested in knowing the answer to your questions also. The GlobTech medical supply used with my B5 is dead quiet. How about something similar for this project? Or is the circuit so sensitive to noise it wouldn't work?

Anyone?

Cool! My Pearl 2 boards are still on the way. Please share your findings if you go this route!

The Pearl 2 requires a bipolar supply, +/- 24 V, and it needs to be few (3+) volts above 24 so the regulators can work properly.

This is not to say a SMPS won't work, on the contrary it could work very well. I'm just not sure there is one that will be of proper specifications to work in this application.

Thanks for your input 6L6! What about skipping the regulators? They output 24 v, correct? Forgive me if this is a silly question.

The performance of the Pearl 2 with a somewhat lower supply voltage is negligibly different. You can wire up an LM317/LM337 as +/-22V regulators, driven from a 48V SMPS with a an OPA544 rail splitter and derive almost the same result. (In fact, the LM317/337 will be quieter and have better PSRR than the LM7824/LM7924).

Thanks for your input jackinnj! So regulating down to 22v would be to allow the +3V leeway for the LM7824/LM7924, correct? Or do you suggest to skip the LM regulators altogether and drive Pearl 2 from +22/-22?

Another question about the rail splitter, such as OPA544, is it a cleaner way rather than using 2 24V SMPS with virtual ground? Reason I ask is that I have two of these available for the ACA 1.6 monoblocks.

On a side note, It will make me very happy to be able to hide the SMPS behind the furniture instead of having another enclosure!
 
Can the Pearl 2 be power with dc batteries? Novice here so it's probably obvious. I just want the quietest phono stage that I can.

Yes, you can do this. Connect an even number of batteries in series with one another (line them up in a chain of NEG of one battery connected to POS of the next battery in the chain). You must use an EVEN number of batteries. The center point is your 0v connection. The POS end connects to your +24v and the NEG end connects to your -24v.

Batteries, however, do not guarantee the absence of noise. I don't have a ready-made reference for you, but the chemical process give rise to all sorts of noise in the line.
 
Batteries, however, do not guarantee the absence of noise. I don't have a ready-made reference for you, but the chemical process give rise to all sorts of noise in the line.

Lithium ion cells have noise in the pico-Volts per root Hertz, nickel cadmium even lower.

Here's an oft-quoted "ready made reference":
https://tf.nist.gov/general/pdf/1133.pdf

Batteries do have impedance which is higher than linear power supplies like Jung, Sjostrom, Salas etc.

I could detect little difference in noise levels of the Pearl 2 with either a Jung Regulator, batteries, or the LMXXX.
 
I could detect little difference in noise levels of the Pearl 2 with either a Jung Regulator, batteries, or the LMXXX.

Thanks for the link, Jack. I also figured someone would have some more subjective comments to add here. I was wondering if any of this would actually be audible or measurable...
 
I see PassDIY sells the Pearl2 boards and JFETS for $200. I'm just starting this addictive hobby, it gets expensive when combined with 3-4 other amp builds. Anyway, is buying from PassDIY the way to go? Thanks!

If your in need of a phono stage, the Pearl II is very nice and a simple build.

You mention 'expensive', if your outside the US it can get a bit costly because of the duties to be paid on top of the $200. For here in the UK the Pearl II is just over $300 by the time it gets to your door.

All the parts are off the shelve + a case or two and a few hours (days) with a soldering iron in hand you've a superb bit of kit.
 
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Eric - are you going to use the Salas shunt reg in lieu of the on-board regs? I've always wanted to try that...

Out of interest Ive tried various 'off board regs' on the Pearl II, W Jung - A L Weeks Super regs, Russ White shunts and Teddy Pardo's super teddy regs...but preferred the standard on board regs 78 & 7924 fixed.

All the the others listed in one form or another resulted in a dark hew to the sound and way to laid back...'to soft' IMO.

Would like to know how the Salas shunts turn out...