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Old 19th April 2013, 02:44 PM   #2131
c_door is offline c_door  Italy
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I've received today my Pearl Two PCB's and fets from the Passdiy store.
After reading through this thread, now time for some questions
I'm thinking to feed them with Salas shunt regs (one Mezmerize board per channel). Another Mezmerize, fully populated, will be my DCB1 line preamplifier.
1) Should I fit the regulators inside the RIAA chassis, leaving only the trafo outside, or better move the whole psu in a separate enclosure, 3ft away?

2) When using the regulated psu I know that the 7x24 regulators have to be removed.
Is this the only modification ? Other thingies to be left out ? Where in the board I have to apply the voltage coming from the psu ?

3) Without the Pearl's regulators, I understand that the shunted PSU has to provide 24V 100mA to the board, so I need to set the Salas reg for 24V, 200mA.
Any good in "hot-rodding" the shunt, let's say 400mA instead of 200 ?

4)The trafo's output, for Salas' instructions, should be (24V+7V)/1.41=22V.
Is a -24/0/+24V 150VA toroidal good for this ? (maybe I move this question to the shunt's thread)

Very basic questions, I know, but I don't want to be wrong when filling my BOM

Thanks a lot! cheers. Carlo.
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Old 19th April 2013, 02:57 PM   #2132
6L6 is offline 6L6  United States
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1) Yes, the regulators need to be as close to the load as possible. Place the transformer in the separate enclosure.

2)If you can't look at the schematic and determine what pieces of the regulator need to be omitted, and where the shunts need to be attached, I strongly suggest you build the Pearl in it's 'stock' (normal) configuration first, get the circuit working first (almost everybody has some issue in the beginning) and only when it's working perfectly, then use the shunt regulators.

3) The powersupply needs to make +/-24v not just +24v. Shunt regulators need to be set for the load - no more, no less.

4) Yes, a 24v+24v transformer will be fine. 150VA is a bit big, but that won't hurt anything.

Glad to hear you are building a Pearl 2! It's a wonderful phonostage, I'm sure you will be happy with it.
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Old 19th April 2013, 03:06 PM   #2133
Tea-Bag is offline Tea-Bag  United States
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6L6, I disagree -
Building both supplies seems a waste of parts potentially.
Here is my modded schematic, this is what my P2 boards look like without the built in regulators.

Click the image to open in full size.

I would mount the Reg in the same chassis as P2 boards, but keep trafo in another box, with DC rectification happening near the Trafo, a 1000uf cap, and a bleeder resistor across the 1000uf cap in trafo box.
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Old 19th April 2013, 03:22 PM   #2134
6L6 is offline 6L6  United States
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I was thinking with a bit of care the 'stock' regulators and other parts could be salvaged and used in a later project - they (the 7*24 and associated components) are very universal and can certainly be used again.

But not doing things twice is also good.
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Old 19th April 2013, 03:43 PM   #2135
c_door is offline c_door  Italy
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You guys are great! Just a few minutes and you gave me a lot of info, and a full schematic too
My idea is then to place inside the same chassis the two regulator boards (Mezmerize portions) side to side, and the two RIAA boards one on top of the other, to save space and keep the in/out cabling shorter.
Without the 7x24 regulators I guess that the lower board won't generate any warmth (or just a little), so the upper one is not affected. A hifi2000 chassis with a perforated top will host the four boards nicely.
Thanks!
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Old 19th April 2013, 03:47 PM   #2136
6L6 is offline 6L6  United States
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That layout should work well. The Pearl RIAA boards will make very little heat.

Make sure the shunt regs have sufficient heatsink.
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Old 19th April 2013, 09:06 PM   #2137
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Quote:
Originally Posted by c_door View Post
You guys are great! Just a few minutes and you gave me a lot of info, and a full schematic too
My idea is then to place inside the same chassis the two regulator boards (Mezmerize portions) side to side, and the two RIAA boards one on top of the other, to save space and keep the in/out cabling shorter.
Without the 7x24 regulators I guess that the lower board won't generate any warmth (or just a little), so the upper one is not affected. A hifi2000 chassis with a perforated top will host the four boards nicely.
Thanks!
If you stack the boards on top of eachother it will not be possible to set P1 without taking out the top board. But then again, that is not something you will be doing everyday.
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Old 19th April 2013, 09:11 PM   #2138
6L6 is offline 6L6  United States
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Ha! Good point!
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Old 19th April 2013, 09:34 PM   #2139
AVWERK is offline AVWERK  United States
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Side mount pots.
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Old 19th April 2013, 11:43 PM   #2140
c_door is offline c_door  Italy
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With the pot mounted on the bottom side of the lower board, and a small hole on the bottom panel, it should work.
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