The Phonoclone and VSPS PCB Help Desk

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#621
The phonoclone and phonocard measure the current generated by the phono cartridge rather than the voltage. The traditional concept of loading the cartridge with a particular resistance to tune the frequency response is not applicable to this circuit topology. Its more of a take it or leave it scenario.

/R
 
#622
Thanks again,
last question before I leave you in peace,

Therefore Based upon cartridge [as per earlier discusion]
Output Impedance 16 ohms
Load Impedance 150-1000 ohms
output .29mv


If I was being a perfectionist / pedantic would I thus make:
R1 =16 ohms
R2 =2.7k ohms

Any other changes to improve sound...

Again many thanks for your patience, knowledge, time and assistance with persavering with questioners like me.

Regards Frank, have a nice day
 
#623
If I was being a perfectionist / pedantic would I thus make: R1 =16 ohms, R2 =2.7k ohms
Click to expand...

Sure, though neither of these components is critical. As long as they fall within a reasonable range you'll be fine.

I hate tinkering with things, so I would have set R2 to give an average gain with an average cartridge in the hope that future cartridge selection would have not required further adjustment.

Thus I have set R2 at 1k in mine at present.

There are no other changes to make, any other tweaks are cartridge independent and mostly center on improving the voltage regulator, cf the discussion of superregs a while back.

/R
 
#625
Hi everyone, I've just completed my vsps project to the point where things actually work. I did this as a personal project for my grade 10 electronics class. Although I think it sounds quite clean, I think there is there is not enough bass and soundstage, and a bit too bright. Is this to be expected? Maybe I should change all my resistors to better quality ones or my op amp NE5534 to something better. Or is there something wrong with my RIAA capacitors? I would like to make it sound much warmer and better than my original Luxman built in phono stage. I tried to make my box see through, but the glue kinda made it ugly. Overall, I did my best....having spent nearly four weeks building it. Any suggestions would be appreciated. Thanks.
 

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#626
Double check that the caps in the RIAA section are correct - when I first built mine I had some of them wrong (used some of the ones for the lo-Z version for the hi-Z version which was what I was actually building - D'Oh!)

Anyway, what I heard was a thin sound though detailed, not as bad as you'd expect considering what I did, although my soundstage wasn't affected. Check your nf to uF conversion too.

Well done on completing it, congratulations on your project!

Fran
 
#628
Hi,

I have one more question, there is this moderate hum that I get when i turn up the volume and kinda gets annoying. I think there is something wrong with my ground. Is it because I used a plastic box instead of a metal for to put my actual phono stage? Or could I get rid of the problem by properly grounding the power supply box? Right now I have all the COM connection and turntable ground going to the COM in the transformer. Any help would be appreciated.
 
#630
I want to try the VSPS ultra for my Benz gold MC, my current tubed phono has not enough gain and delivers a humm along with the music.

Have all the parts for it to solder on a perfboard, but i realised i didn't have the 4.7 uF output caps. I wondered if i can omit them with a sort of potmeter adjusment out of V+ and - into pin 1 of the AD797/LT1115. Maybe it even sounds some better with it too.
Has anyone thought of this or tried it?

VSPS: http://www.geocities.com/rjm003.geo/rjmaudio/diy_pho7.html
AD797: http://www.analog.com/en/prod/0,2877,AD797,00.html

Thanks
 
#631
I was looking at the phonoclone circuit and wondered about adding the 50KHz pole to the RIAA. Would that just involve putting a 3.18K ohm resistor in series with the 1nF cap or would that affect the values of the rest of the RIAA network?
 
#632
tubee:

You can get the 4.7uF caps at Partsconnexion, or any substitute film cap 1uF or above can be used.

Two observations you may or may not care to consider:

Messing about with trim pots is more trouble than its worth.

Messing about with the AD797 is more trouble than its worth.

and for tkwou:

Messing about with a 50kHz pole in the Phonoclone circuit isis more trouble than its worth. Letting the gain roll off helps to prevent oscillation.
 
#633
rjm said:
tubee:
You can get the 4.7uF caps at Partsconnexion, or any substitute film cap 1uF or above can be used.

Two observations you may or may not care to consider:

Messing about with trim pots is more trouble than its worth.

Messing about with the AD797 is more trouble than its worth.
Click to expand...

Hi RJM

Thanks for reply.

Even when i take a precision 10 turn pot it will problably always be a fiddling with it to get it right indeed. (Have a dc-coupled tube line amp) I will first buy a motor starter cap, reasonable good sound, low price, easy available.
 
#635
Those are noninverting gain stages, there is an inbuilt high frequency pole by default as the gain cannot fall below unity. I'm only tuning it to 50 kHz. The Phonoclone is inverting, the gain continues to fall as the frequency increases. I think its better not to interfere with that desirable trait. /R
 
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