VSPS Help/Suggestions

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Hi,

I built a VSPS phono stage, and it sounds kind of terrible. I am wondering if anyone can help me figure out what the problem is. The problem with the sound is that the treble is rolled off, and everyting sounds a bit recessed. The lower-mids are a syrupy (which is okay) , the bass is full, but the treble is really just not there.

My build is as follows:

There is a pair of LM317 circuits (schottkey rectifiers, 2200uF smoothing caps, 2 10uF caps after the output, etc.) that provide +/- 15V. From that there are dual mono pairs of 12V regulators (LM340/LM7912) that use the suggested 220uF caps (FMs) on the in and out pins. The curcuit itself uses dual mono opa627 opamps. The feedback resistors are all Riken Ohm, the feedback caps are silver mica, the rest of the resistors are metal film, the output caps are Solens, and there are .1uF film and foil caps on the voltage pins of the opamps.

So, what I am trying to figure out is whether it is the circuit, the PS, or a problem with my turntable (which has been in storage for about 6 months) Any suggestions on what to try? The two things that seem like early candidates are the silver mica caps and the PS bypass caps, but I am not sure.

I attached a blurry photo that should give some idea of the setup.
 

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rjm

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Hi,

I'd nonetheless double-check that the resistors and capacitors in the feedback loop are the correct value and correctly connected.

Your build appears neat and tidy and well thought out. I wouldn't have separated the regulator and VSPS circuits on separate boards, and I 'm not so sure using Solens for power supply decoupling is the best solution, but these are likely minor points.

/R
 
Bas Horneman said:
Good to hear all is well!

Thanks. For whatever reason, I had decided to not believe in burn-in in this case and just assumed it would work immediatly. I think it is by far the most dramatic example I have heard, however. Part of it is likely that the cartridge (a clearaudio) on the table needed to get going after a long time with no use.

rjm said:
I'd nonetheless double-check that the resistors and capacitors in the feedback loop are the correct value and correctly connected.

Everything seems to be working quite well now. I am pleasantly surprised by how good this thing sounds.

rjm said:
Your build appears neat and tidy and well thought out. I wouldn't have separated the regulator and VSPS circuits on separate boards, and I 'm not so sure using Solens for power supply decoupling is the best solution, but these are likely minor points.

The seperation is why I added the extra PS bypass caps.

As for Solens, they are the output caps. (The power decoupling caps are dayton film and foil.) I agree that more boutique-y caps sound a bit better, but at their price point, I think these things can't be beat. While they get a lot of bad press around here because they are so cheap, my sense is that all of their sins are ones of omission. They may not ofer the absolute last level of resolution, but they are pretty darn close for the money.

Also, I would actually think that with just an opamp in the circuit here, that one should be able to get away without the caps at all. I'll take some measurements later and see if this is the case.

-d
 
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