The Phonoclone and VSPS PCB Help Desk

[kaban]

OK, an update:

I was having issues with my newly completed Phonoclone. It is very bass shy, and I am having to really pump the bass level out on my amp to make it sound decent. It's not a flat response at all.

It seems that the RIAA section of the circuit could be the issue.
I managed to have a look at what components and values I have there.

I double checked R5 and R6, both are OK. Correct values on both boards.

In C1 I have a capacitor marked "102K100" that is the 1.00nf capacitor.

In C2 I have two caps - One marked "222K100" that is the 2.2nf cap and the other cap marked "684K100" which is the 680pf cap.. or it should be. These two are in parallel to make a total of 2.90nF.

I have a feeling that the 680pf cap is where I have gone wrong. I am not very good with capacitor codes but if I am correct the value of this cap is 680,000pf. or 0.680uf. Is that correct, or am I way off the mark?

Also, would I be correct in saying that the C2 section of the RIAA circuitry is the one that attenuates bass?

Thanks,

Kaban

[AndrewT]

102k=1000pF=1nF
222k=2200pF=2.2nF
684k=680000pF=680nF

The third digit is the number of zeros to be added to the first two digits.

681k=680pF

I think the trailing 100 is the DC voltage rating.

[kaban]

Ah ha!

So that is where I have gone wrong! I'm using the wrong value caps! I will obtain the proper values and give it a go.

Thanks for the help Andrew!

Kaban

Originally posted by AndrewT
102k=1000pF=1nF
222k=2200pF=2.2nF
684k=680000pF=680nF

The third digit is the number of zeros to be added to the first two digits.

681k=680pF

I think the trailing 100 is the DC voltage rating.

[woodturner-fran]

BTW, thats exactly what I did first time I did my VSPS and got pretty much the same result as you.


Fran

[Onvinyl]

Hi Fran,
how do you like the sound with your zyx and phonoclone? I run my clone with a DL103-R (14R impedance) with an R2 of 680R. No (subjective) distortion here.
Rüdiger

[woodturner-fran]

Same here really - very happy, no distortion at all. In fact I had a slight hum at higher volumes due to EMF. Since I lowered the gain a little thats much reduced.

I actually have a second phonoclone and I using it with a Benz L2 which has an output of 0.35mV and I think I will drop the gain on that one too. Something like 680 or 780R would probably do. Theres 1.2K in there right now.

On extended listening I can't see that it has lost anything - no loss of any detail, dynamics etc. Doesn't seem to have any adverse effects.

Fran

[brianco]

I have two questions before starting on a Phonoclone: any help much appreciated.

1) to save wading through 35+ pages, can I simply leave out the eq. stage? (I have a much loved and good preamp - so all I want is a step-up.)

2) My cartridge is an exceptionally low output original Audionote 1o. It is also very low impedence. Any suggested starting points on loading?

Many thanks,

Brian.

[brianco]

Sorry - double post

[tube 300]

Hello play for a while now with the Phonoclone limited
but not much because i dont get complete rid of the hum
and i think i tried everything possible
I tried 1 transformer
and now i use 2 transformers.
I tried com to case and today i build it back for the forth time to input ground to case.
When i use a dummy load (47 ohm in a rca connector) i measure a hum of 0,014 volt on the output
thats audible in my system and to much .
When i use the tonearm cable i measure 0,026 volt on the output.
for the measurements i use a Fluke true rms voltage meter.

Can someone measure the output hum of his Phonoclone please
and post it here
Best regards Robert

[woodturner-fran]

I have still a little hum in both of mine - but its low. Back a bit in the thread there was a new grounding scheme for anyone using a dual mono supply - it does help.

But also, I found that when I move around the interconnects from phonoclone to amp makes a huge difference. My leads from the TT to the phonoclone are screened, but not the interconnects to the amp. It does seem sensitive to picking up hum from other stuff. Another thing you could try is dropping the gain a little - the kit has R2 at 1.2K. You could try adding another in parallel - say a 550R. That would drop the gain a bit, is easily reversible and might help with the hum. I often wondered about adding some caps across the outputs to see if that would help but never did it.

Brianco: Use something that matches the DC resistance of the cart.

... OK I just looked it up and see thats its only 1R! I dunno - try say 5R or 10R to see. The kit RJM did had it at 10R I think.

Fran