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Old 18th January 2014, 08:55 PM   #2631
rjm is offline rjm  Japan
Richard Murdey
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Thanks for the kind words of support.

Shopping around, it seems components at Digikey and RS are priced about the same. The depreciating value of the Yen is part of the story, but I think also that Mouser in particular offered very attractive pricing 4-5 years ago when they made a big push to enter the Japanese market, and now they are moving to reclaim their profit margins.

I still have parts in stock from when I made placed some big orders at Mouser two years ago. Prices will stay as they are until probably the summer, but regrettably the kits are going to get quite a lot more expensive after that.

/R
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Old 18th January 2014, 09:04 PM   #2632
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Quote:
Originally Posted by AndrewT View Post
Could you open a Thread, or Blog, or ? and describe the method and equipment in more detail?
It was just a suggestion, rather than something I'd actually done ... but the procedure itself is trivial. Looking for a strange turn off buzzing doesn't require high sensitivity or a low measurement noise floor, so its just a matter of getting a 3.5mm stereo <-> RCA adapter cable, and connecting the VSPS output to the line input of a laptop. I'd use the free software Audacity to record the sounds of turnoff, and (assuming the turn off spike was not so dire as to saturate the input) just throw up the data on screen to take a peek.

One further step up in complexity would be to make your own probe with a 3.5 mm jack on one end and alligator clips or something similar on the other end. You could even make a "10x" style probe with a voltage divider and AC coupling, so that 1) protect the laptop for DC voltage and 2) lower the input signal to allow larger voltages to be measured with the line level input.
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Old 19th January 2014, 02:54 AM   #2633
athanor is offline athanor  Portugal
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Hello all,

this is a really great place! I've already build 3 VSPS preamps for me and a couple of friends and everything seem to always work great!

Anyway, and since I'm no electronic guru, my question is; what components should I bypass in the RIAA section to remove the RIAA equalization? I was trying to use the VSPS with old filter types (using software..), but I'm not shure if removing C1, C2, R4 and R5 will do it right?

Cheers all,

Isaac Daniel
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Old 19th January 2014, 04:32 AM   #2634
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A flat amp, as a mic preamp or low noise preamp for data aquisition etc.

remove R3 R4 C1 C2

adjust R5 to set the gain as G=R5/R2+1. Circuit not recommended for G<5.
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Old 9th February 2014, 12:56 AM   #2635
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I can only speak to the VSPS300 and it's value. You would have to compare it to something to make a judgement. It is logical to compare it to another similar item except there is nothing that truly compares. There are certainly other phono stages but none with 1)split rail power supply, 2)one single stage of gain, 3)world class non current limiting power supply built in.
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Old 3rd March 2014, 03:29 PM   #2636
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Is there an advantage to using the buffer after the VSPS 300? Can the output cap be reduced or eliminated?
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Old 3rd March 2014, 11:37 PM   #2637
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It cannot be eliminated, but it can be reduced.

The advantage is more that the buffer isolates the VSPS op amp from the inductance/capacitance of the interconnects, so all it has to do is drive the RIAA network and the (resistive, high impedance) buffer input.
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Old 14th March 2014, 05:55 PM   #2638
hajj is online now hajj  Lebanon
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Hi Richard,
What's the VSPS's input capacitance?
I'm trying to fine tune the input impedance to better match my new cartridge and need an estimate as to where to start.
(tried searching in the thread, but the forum's search engine being what it is, I couldn't the answer)
thanks!
Nick
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Old 14th March 2014, 06:04 PM   #2639
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I think it would be the input capacitance of the used op amp + hookup cable + rca chassis
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Old 15th March 2014, 04:21 AM   #2640
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Quote:
Originally Posted by Wirehead.be View Post
I think it would be the input capacitance of the used op amp + hookup cable + rca chassis
Yes, and my understanding is that the cable capacitance (100 pF/m typically) will dominate.

My advice is to just follow the manufacturers advice. If they suggest 100 pF, put 100 pF across the inputs...
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