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Old 8th July 2013, 08:23 AM   #2461
rjm is offline rjm  Japan
Richard Murdey
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@devinyl

The Dynavector 10x5 output is 2.5 mV. It would normally pair with a 36-40 dB MM phono stage just fine, that you are finding that 50 dB (1 V nominal sensitivity!) is insufficient suggests a deeper problem that just the preamp.

To be clear: the VSPS300 at 50 dB with the 10x5 should be nearly as loud as a full line-level output, from a CD player for example.

@djnubz

link does not work. Suggest building a power supply according to the recommended BOM, and then experimenting afterwards. Dual mono: if you have $3000+ worth of components up and downstream, you should give it a try. If you don't, you don't need to worry over it.
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Old 8th July 2013, 09:30 AM   #2462
devinyl is offline devinyl  United Kingdom
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Cheers RJM. Looks like I've got to get the meter out and start looking for more of my mistakes as the vsps is nowhere near as loud as my CD line. Good / balanced sound from both channels, no distortion or interference, just not enough output. I noticed in one of dimkasta's earlier threads about low output due to low voltage from the x-regulator and looking for 10v to bump performance. I'll double check my R values against the BOM but whatever it is, its common to both boards. At least I'm consistent with my errors!
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Old 8th July 2013, 06:23 PM   #2463
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Here is another link

I just ordered 2 antek torroids and will be building a dual mono but I am curious what you think about using a high quality modern smps with your preamp design. I would think that a modern smps could work quite well due to their very low output impedance and ultrasonic switching frequencies.
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Old 10th July 2013, 12:10 AM   #2464
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Accidentally switching components, 47 ohms for 47k ohms for example, could cause the loss of output signal. That seems more likely than a problem with the power rails.

I have no comment re. smps since I have never used them, or rather what I have used in various scenarios (not phono stages) invariably sounded awful, with the single exception of my Onkyo sound card.
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Old 10th July 2013, 08:08 PM   #2465
devinyl is offline devinyl  United Kingdom
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Thanks RJM you nailed it from the other side of the planet and I couldn't see it when it was staring me in the face!!! I won't embarrass myself any further, just to say I've ordered some resistors of the right value and when I've corrected the mistake I'll update further.
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Old 11th July 2013, 09:36 PM   #2466
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Just finished correctly loading my Shure V15 running on a Thorens TD124 II and plugged her in. The VSPS sings! I forgot how good vinyl can sound; rich, warm and full of bloom. Great job RJM!
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Old 21st July 2013, 02:46 PM   #2467
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Hi Richard,

I finally had some time for checking things out.
PS is fine giving 35VDC between V++ and --.
Everything look fine but I get no sound at all.
Here is a pick. Can you see anything wrong?
Many thanks,
IK
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Old 25th July 2013, 11:20 AM   #2468
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Richard Murdey
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Sorry for the late reply.. its vacation time, here at RJM Audio.

It looks fine from here. A good clue is whether you hear any change in the background noise when you power up the VSPS. If yes, then its probably working but you haven't connected the inputs to the cartridge properly. If no, its most likely a problem with the output connections.

Also, double check the voltage from IC1 pin 4 (-12 V) and pin 8 (+12 V) to GND.
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Old 27th July 2013, 06:44 AM   #2469
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Hi Richard,

Enjoy your vacation

Here is what I'm getting:

VDC between V++ and V-- is 31.1
Between Pin 4 and ground -1.48VDC
Between Pin 8 and ground 0.4VDC

I get the same no sound when vsps is powered on or off

Any clue to whats wrong?

Thanks so much
IK
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Old 27th July 2013, 10:02 AM   #2470
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Clearly the voltage regulators are not operating properly. Could be a short from v+ to ground, or could be that the regs are shot. Do they get hot?

I would remove the opp amp from the socket and check the voltages at pin 4 and 8 again.

My best guess is you switched the lm7812 for the lm7912, so you have the negative reg on the positive rail.
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