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The Phonoclone and VSPS PCB Help Desk
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Old 4th July 2019, 08:32 AM   #4161
warrjon is offline warrjon  Australia
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Hi Richard,

I have an issue with my Phonoclone and need some advice. The story. My Rega Apheta fell apart (that's another story) and was replaced with an Apheta 2. The issue is it sounds dull and I have lost detail and imaging.

I suspect the issue is a loading mismatch between the cart and input effecting the freq response. Unfortunately Rega do not release much info on their carts, only resistance and voltage which is the same as the Apheta 1.

Any ideas??
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Old 4th July 2019, 11:39 PM   #4162
rjm is offline rjm  Japan
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The Phonoclone and VSPS PCB Help Desk
The phonoclone has no loading to mismatch, so it's definitely not that. While of course all phono stages interact with cartridges, so it could be that the Apheta 2 does not "like" zero ohm load, I rather suspect something more mundane: either the new cartridge hasn't broken in yet or the stylus isn't as perfectly aligned / set up as your previous one.
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Old 5th July 2019, 10:41 PM   #4163
warrjon is offline warrjon  Australia
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Thanks for the reply,

The Rega Apheta and Rega tonearms have a 3 point mount that sets cartridge alignment and has no adjustment (maybe 50um sideways). Even so I still checked it with the protractor.

I cobbled up a JFET MC pre this morning and connected it to my old MM phono stage powered from a couple 9V batteries to verify whether it was the TT or preamp.

Conclusion the Apheta 2 does not like the Phonoclone. I have read reports that the Apheta 2 is very sensitive to loading, even though the raw specs are the same as the Apheta 1 the motor is completely different.

Oh well the search starts for a new phono preamp.
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Old 6th July 2019, 06:23 AM   #4164
rjm is offline rjm  Japan
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It's true not all cartridges like a zero ohm load, though I'm surprised there is such a difference between an original and upgraded version of the same mode.

The Emerald phono stage has a conventional voltage input, and the Switchboard offers multiple loading options.
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Old 19th July 2019, 11:31 AM   #4165
warrjon is offline warrjon  Australia
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Ok I can say for sure the Apheta 2 does not like Zero Ω loading. I splashed out on a Rega Aria and I have the bass and dynamics back.
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Old 19th July 2019, 05:25 PM   #4166
rjm is offline rjm  Japan
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Not all cartridges do, though this is the first definitive example I've come across. Speficially, carts with low resistance and high inductance may have a different frequency response into 0 ohms than the recommended load.

The only oddity in the specs of the Alpheta 2 that might be relevant is the recommended loading capacitance is a high 1000 pF.
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Old 20th July 2019, 10:15 AM   #4167
Leffler is offline Leffler  Sweden
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Default Old VSPS

Hello

You probably haven't seen a VSPS this old for a while.

I found myself disappointed with my vinyl setup, and remembered this old half-finished build. I need to order a pair of OPA314 anyway, and I have a 50VA 20+20v transformer, so I'll might as well use a pair of 18v brides for perhaps slightly better performance? I'll also use some high grade output caps.

Anyway, my question is this, this uses the old RIAA values of 1nf and 330p and corresponding resistor values. Are the current values somehow better, or should I just - "let it be"?

Thanks!

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Old 21st July 2019, 03:48 AM   #4168
rjm is offline rjm  Japan
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Yeah, that's from so far back I can't remember. Did I originally use 1 nF and 330 pF? It must have been for only a brief period.

Essentially, that puts the RIAA network at 3x the impedance of the current one. I don't expect it would make much difference. I changed it to try to achieve lower noise.

Note that much more recently the RIAA network was changed again to remove the 50k time constant. This change does improve the sound slightly.

So you could modernize your build use the current values, but honestly I can't really say it would be worth the trouble now you have everything soldered. If you want to remove the 50k time constant but keep the same 330 pF and 1nF caps you have, let me know the resistance values you have and I can tell you the revised values you need to substitute.

/R
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Old 21st July 2019, 08:11 AM   #4169
Leffler is offline Leffler  Sweden
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Quote:
Originally Posted by rjm View Post
Yeah, that's from so far back I can't remember. Did I originally use 1 nF and 330 pF? It must have been for only a brief period.

Essentially, that puts the RIAA network at 3x the impedance of the current one. I don't expect it would make much difference. I changed it to try to achieve lower noise.

Note that much more recently the RIAA network was changed again to remove the 50k time constant. This change does improve the sound slightly.

So you could modernize your build use the current values, but honestly I can't really say it would be worth the trouble now you have everything soldered. If you want to remove the 50k time constant but keep the same 330 pF and 1nF caps you have, let me know the resistance values you have and I can tell you the revised values you need to substitute.

/R

According to my mailbox, I bought it from you in 2006. It's strange I never bothered to test it back then when it was pretty much done (and I was constantly tweaking my vinyl setup... Currently I have toddlers, so it is usually stowed away) but I'll go ahead now!

The original instruction with the values I currently have is here (hi-Z values 330k, 2.2M, 330p, 1n + Allen Wright): The VSPS

Don't bother recalculating, I'll just to simply replace it with the current parts, but I guess it could be troublesome to fit three parallel 1nf on this board... I suppose I could put the two extra ones underneath the board. Thanks for the offer even though this must be way out of warranty.

The rest of my system is extremely revealing these days, so I might as well put those extra minutes and cents in and try to get the most out of it. I will be replacing the LM7x12s (with 7x18s, mainly not to just waste the spare voltage as heat) and the output caps anyway - I assume going to 18v doesn't change the feedback loop/ riaa correction? The rest of the vinyl system is a Denon DL160 high output MC pickup (on a heavily tweaked Rega planar 2) so I think 47k should be the right input impedance.

Thanks for your support!

Last edited by Leffler; 21st July 2019 at 08:34 AM.
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Old 21st July 2019, 03:06 PM   #4170
rjm is offline rjm  Japan
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I recommend using a straight wire jumper instead of the Allen Wright resistor, and increasing the 2.2 Mohm resistor to around 2.5 Mohms. That should add a little roundness to the low end.
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