Is regulated PSU for phono preamp a MUST? - Page 2 - diyAudio
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Old 10th April 2005, 07:37 PM   #11
jcarr is offline jcarr  United States
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Assuming you don't mind a hefty increase in weight, another worthwhile route that hasn't been mentioned yet is a choke input, with or without regulators.

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Old 10th April 2005, 11:16 PM   #12
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How different for this phono preamp application between CLC and one with a choke PSU then?
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Old 11th April 2005, 01:42 AM   #13
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if you have to, use a pair of positive and negative regulators -- i.e. on the positive rail an LM317LZ (the 100ma, TO-92 version of the LM317) at 18V and one following it with the adjust resistors set at 13.7V , same with the negative side -- this really works and costs next to nothing.

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Old 11th April 2005, 03:43 AM   #14
SY is offline SY  United States
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Regulation is cheap'n'easy, relatively, but...

Jcarr's comments about L input are correct- it's a great way to have low noise and good regulation but stay passive. I wonder, though, since this is more-or-less a constant current load (i.e., it's not an AB power amp) how important regulation really is. And given that the PSRR is better than 60dB at all audio frequencies, I really, really wonder how low noise it really has to be. As a frugal butcher, you might find that a simple CRC filter is all you need.
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Old 11th April 2005, 03:57 AM   #15
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I was questioning the same in a way, since fastcat95's schematic also set the bias into classA and I was thinking in relative terms like my JLH Class A with CLC PSU work very nicely. Hence the title of this thread..hmm now I have to reconsider about the PSU direction...

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Old 15th April 2005, 02:50 PM   #16
AndrewT is offline AndrewT  Scotland
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Hi Chris,
the proposed input capacitance seems a bit high @ 250pF.
Try making it adjustable unless you know that this cartridge needs a very high value.
Remember that the arm and interconnect cables also have capacitance that adds to the input value.
I would try switched steps of 0pF, 50pf and 100pF to start giving 4 choices until you hear what it sounds like.
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Old 15th April 2005, 03:41 PM   #17
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Yes Andrew,

I have actually think of making the R1 and C1 (the input loading) parts of the phono preamp with female pins on the board or even outside the box so that I can just push different cap values in. You are quite right that the cartridge will be changed quite often and I want to able to swap out C1 on the fly without soldering. Thanks for the suggested cap values, I will try and keep these values in my supply box from now on.

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Old 23rd April 2005, 08:12 PM   #18
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Quote:
Originally posted by Mikett
http://www.alw.audio.dsl.pipex.com/jung_schematic.htm

http://www.aoselectronics.com/jungsrpcb.html

http://home.comcast.net/~walt-jung/w...ed_PN_Regs.pdf

will transform op amp based circuits. The AOS boards are a bargain! As ALW has eluded to, the Jung Super Regulator is a clear step superior to the Sulzer type circuit.

IMO, these are the steps

Passive, no reg
Zener based
Capacitance multiplier
78XX, 79XX
317/337
LT108X
Sulzer
Jung Super Regulators.

Take your pick, each progression wil have greater transparency, depth and micro dynamics.

Take A pair of super regulators from AOS
Combine with
http://www.sound.westhost.com/project06.htm
and you have a ready to go project that should sound very good with the OPA637 you've chosen.

Wow it is getting expensive with the AOS boards, they are not bargain with my income standard. For this project I need 4 boards for mono blocks, just the unstuff board alone will cost around $70US and may be custom charges yet unknown..
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Old 23rd April 2005, 11:08 PM   #19
Mikett is offline Mikett  Canada
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I believe AOS is in Canada so there are no custom charges and shipping is minimal
In my opinion it's better to have a better regulator running two channels than multiple inferior ones in monoblock fashion. The sound of the power supply is significant on op amps as many chip amp zealots have discovered.
You can always etch and drill but a "proven" layout is important in this supply stability. Proven layouts can be found in the Audio Amateur/AudioXpress which are kept in the Toronto Public Library Science reference section. Xerox copiers are available.
You can always try to get a price break on multiple boards, just ask and see if it happens.
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Old 23rd April 2005, 11:13 PM   #20
Mikett is offline Mikett  Canada
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When ordering from the USA to arrive in Canada, be aware that if the item costs less than $10US. There are no applicable GST and PST and handling charges. If it is over $10, GST,PST will apply as well as a $5 handling charge by Canada Post.
Request that the suppier ship via USPS NOT UPS or FEDEX or you'll end up paying a small fortune for their handling and brokerage charge.

So choose USPS and pay more for HANDLING and LESS for the product cost from the supplier. "Wink Wink".
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