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Mr. Entropy  
#1 Posted : Wednesday, October 1, 2014 3:25:39 PM(UTC)
Mr. Entropy

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I am looking for a power supply for the Pass B1 buffer preamp. The requirements, quoting Nelson Pass:

"The buffer uses an external power supply from 18 to 24 Volts DC. You can power it with batteries, but most convenient is an external regulated supply running off the wall. The preamp typically draws fewer that 0.02 Amps, so current is not much of an issue. A regulated supply is better, but the circuit is pretty good at ignoring noise on the supply and minor fluctuations."


My reading suggests that most people prefer Vout ~ 24vdc, and the excellence of the Placid and its ability to adjust Vout are attractive. Thus, do you think the Placid HD 2.1 is a good choice for my application?

Many thanks,
Pete

BTW, I recently inquired about the availability of the LCBPS which would power the Analog Signal Processor (ASP) of my Linkwitz Orions (i.e., I'm looking for two power supplies for different applications; I'm not confused). Angel

Edited by user Wednesday, October 1, 2014 3:51:24 PM(UTC)  | Reason: remove discussion trouble with the Vout calcuation in the manual, not really relevant.

miero  
#2 Posted : Thursday, October 2, 2014 7:37:50 PM(UTC)
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It might work, but you will need transformer with higher voltage output, approx. 20-22V AC. It will be rectified to 28-31V DC and then regulated down to 24V.
Mr. Entropy  
#3 Posted : Thursday, October 2, 2014 7:44:21 PM(UTC)
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Thanks, very helpful. Unless someone here sees a problem, I will go ahead and order in the next day or two. / Pete
Brian Donegan  
#4 Posted : Thursday, October 2, 2014 8:24:36 PM(UTC)
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You will probably want to increase the voltage of the big cap as well. I would switch to a 50V.

I have not tested the Placid at these voltages, but might give it a try tonight if I can find a little time.

Mr. Entropy  
#5 Posted : Thursday, October 2, 2014 9:52:44 PM(UTC)
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Thanks!! I'm very interested, but not in a big rush either. Let me know what you think once you have had time to try it. / Pete
Mr. Entropy  
#6 Posted : Friday, October 10, 2014 1:35:13 AM(UTC)
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Any further info, advice, or opinions? / Pete
Brian Donegan  
#7 Posted : Friday, October 10, 2014 4:25:34 PM(UTC)
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I was able to test this, but only for a short time. Everything seems to work just fine. I was using a 15v+15v trafo in series, so ~30V input. This brought the rectified voltage up way to high for the standard smoothing cap (35V), but I was able to adjust the output voltages to 25VDC and adjust a range of shunt currents.

I would probably up the smoothing cap to 50V in your situation, just to make sure there is plenty of room, but I think it will work fine.

I could swap a 50V/15kuF cap in to the kit in place of the standard 35V/10kuF if you want.

Mr. Entropy  
#8 Posted : Friday, October 10, 2014 5:42:31 PM(UTC)
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OK, thanks...

Brian Donegan wrote: "I could swap a 50V/15kuF cap in to the kit in place of the standard 35V/10kuF if you want."

Yes, let's do that.

Will the standard heatsinks be sufficient if--as Nelson Pass claims "...the preamp typically draws fewer that 0.02 Amps", or will they need to be bigger? For context, the Placid HD 2.1 will power a Pass B1 preamp (see schematic, fig 1 at https://www.passdiy.com/...lifiers/b1-buffer-preamp) which will then feed the Analog Signal Processor (essentially the XO) of a Linkwitz Orion system.

Thanks again,
Pete




Mr. Entropy  
#9 Posted : Monday, October 13, 2014 6:59:06 PM(UTC)
Mr. Entropy

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Just placed my order! Thanks..
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