The Phonoclone and VSPS PCB Help Desk

[woodturner-fran]

Woo Hooo,


My kit arrived today!!!!!!

And today was the day I picked up the new Tx for the build - and I just got my cases last night!


I can't believe how quickly it got here - Kyoto to Dublin in 3 days - wow!


Fran

[tube 300]

Hi Richard
Mine arrived also today
thats very Quick.
I build yesterday my cases
and will finish them next week.
The kit looks very good and the certificate is nice
now i start put the kit together.
Thanks for the good work!

[tube 300]

Abouth the Black Gate non polar, is there a "best" way to put them in the signal?
there is a short and longer wire i think one is inner and the other outer foil .

[Toaster]

Thanks Richard - No. 10 has arrived safely in the UK. I'm intending to build the boards up tomorrow.

[lancer]

Received mine today. Thanks Richard.

[earsandeyes]

Received mine yesterday.
Took about 75 minutes to assemble.

I will try to fire up tonight.

E&E

[mavallarino]

And mine?

Richard: have you got the new RIAA correction curve with standard resistors?

Saluti,
MV

[rjm]

You mean this? Its also on the VSPS page, btw.

/R

P.S. And before you ask: I know the upper curve looks bad, but it really isnt. (+/- 0.1 dB is bad!? Most of my phonoclones that I have built were worse than this!) You arent going to get anything like the bottom trace anyway unless your capacitors are also matched to under 1%.

[AndrewT]

Hi,
getting the 1uF and three parallel 1uF to match to better than 0.5% is easy. Getting both channels to match is nearly as easy. Getting absolute accuracy is nearly impossible due to inaccuracies in our measuring standards.

If all the caps are matched perfectly but sit 1% low or all sit 1% high, what do these two response curves look like?

Can you eliminate the 0.6db rise @ 20kHz?
How high does that peak go and at what frequency does it level off?

[rjm]

>If all the caps are matched perfectly but sit 1% low or all sit 1% high, what do these two response curves look like?

1% will be trivial deviation. 3% willl be about 0.1 dB, see attached for 732k, 105k, 1.03nF and 3.09nF...

>Can you eliminate the 0.6db rise @ 20kHz?

No, not with the non-inverting topology. You can shift it to higher frequencies somewhat though. As explained on the web page, I have set it deliberately to follow the Allen Wright modified RIAA response.

>How high does that peak go and at what frequency does it level off?

Since the curve is referened to the RIAA response its not a peak, its a levellling off of the RIAA high frequency cut. It continues until the op amp runs out of bandwidth.