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Old 18th October 2012, 11:16 PM   #2081
rjm is offline rjm  Japan
Richard Murdey
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@wirehead.be

Sorry, I meant to comment on your FFT plots earlier: The bottom plot seems about right for the noise floor of the VSPS. Note the noise spectrum has an "inverse RIAA" shape to it, and no power line harmonics. This indicates a clean bill of health. To get a truly accurate picture, the inputs should be shorted with a load resistor of 1k to mimic an MM cartridge. The top plot, I wouldn't put a lot of value in. If noise is injected into the signal path by clicking the mouse, noise is also being picked up from who knows where.

@Hikari1

I'd suggest using the VSPS and adjusting the output gain to 50 dB. The output signal with be close enough to a standard line level signal that it should be usable in your passive setup.

Switch mode power supplies: don't use them.

/R
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Old 24th October 2012, 11:26 AM   #2082
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Can I use any transformer from 2x11-19 volt. Normally LM78xx series can operate in a range from 15 to max 27 volt giving secondary rang eof 11-19 volt. Or are there other aspects I haven't thought about?
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Old 26th October 2012, 07:02 AM   #2083
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Originally Posted by rjm View Post

So, minimum recommended is 35 VA. Bigger is generally better, but quality counts, too.

-rjm
What's the technical reason that bigger is better? I'm not building a power amp but a phono stage.

What is the maximum current draw (peaks)?

I have a small poweramp with Tripath 2024 chip. It have a 12 volt 2A supply, and it's adequate. Why should I build a PSU for a phono stage, that is more powerfull that one I use in a power amp?

To start with I use a 16VA 2x12 volt transformer, and later only I might try a total overkill PSU just to compare.
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Old 2nd November 2012, 09:12 AM   #2084
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Quote:
Originally Posted by Kjeldsen View Post
What's the technical reason that bigger is better? I'm not building a power amp but a phono stage.
here

More importantly, if you read the various VSPS and Phonoclone related threads you will find many testimonials vouching for the significant improvement.
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Old 2nd November 2012, 09:17 PM   #2085
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Power supplies should not go "wild" and become a monster current sources. Some people tend to use very powerful transformers to power up their RIAA preamps (me including).

However I have a very good reason to use 35VA trafo instead of 15VA. My local supplier offers those two with just 3-4 euro price difference, so why go cheap? I'm not manufacturing RIAA preamps in thousands of units per year

Regards,
Venci

p.s. toroidal transformers nowadays are so affordable.
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Old 2nd November 2012, 10:23 PM   #2086
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Quote:
Originally Posted by Kjeldsen View Post
I have a small poweramp with Tripath 2024 chip. It have a 12 volt 2A supply, and it's adequate.
The secret is the word adequate.... It really is not a negative word, but not a positive either...

Give a 100VA a try and you will not regret it. Same with full dual mono.
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Old 3rd November 2012, 09:23 AM   #2087
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I have the stereo module, so dual mono is not possible.

Tranformers i Denmark are not cheap. I have now a good quality 16 VA for 20$ and 35 VA was 30$. I like to start cheap, and then get my own experience with more sofisticated items.
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Old 3rd November 2012, 10:43 AM   #2088
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The problem with starting cheap and then moving up is that it costs more than doing it 'properly' in the first place.

The designer and others have said 'bigger is better' so why query it? Doing it right first time is always cheaper.

FWIW my PhonoClone3 has a 120va transformer, and its doing very nicely thank you. I never considered getting anything smaller (and TBH I did think of a 250va one, but then physical size starts to become an issue)
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Old 3rd November 2012, 11:28 AM   #2089
simonov is offline simonov  Bulgaria
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In general,
no audio device is better than its own power supply
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Old 4th November 2012, 09:33 AM   #2090
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As you can see from the replies, everyone has their own threshold.

Really though, there is not normally a very great difference in cost, size, or weight up to about 50 VA so you might as well buy in at the top of that range.

Whether an upgrade to 100VA-160VA is a worthwhile does depend somewhat on what you can get and at what price. In any event for the stereo VSPS I'd suggest sticking with 35-50 VA.
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