The Phonoclone and VSPS PCB Help Desk

[dimkasta]

Not sure how various cartridges will appreciate that input resistance.

 

[Bibio]

@ rjm

is there an eta on when you will have more phonoclone kits for sale?

 

[rjm]

@bibio Though it doesn't say so, I'm out of both Phonoclone 3 and VSPS 300 boards right now. Everything back to normal from March 3rd.

@vulejov The input series resistance linearizes gain and frequency response at the expense of S/N. It's a reasonable tradeoff either way.

 

[pdg]

@bibio Though it doesn't say so, I'm out of both Phonoclone 3 and VSPS 300 boards right now. Everything back to normal from March 3rd.

A friend of mine who orders boards frequently from a source in China told me that there's a two week delay because of holiday activities there, probably related to their New Year celebrations.

 

[vulejov]

@vulejov The input series resistance linearizes gain and frequency response at the expense of S/N. It's a reasonable tradeoff either way.

With LT1028 noise is 400 uV on 20kHz...

I dont believe that cartridges have linear frequency response when working in "zero impedance".. I dont believe manufacturers..

 

[Bibio]

thanks Richard.

 

[rjm]

Manufacturers make no claims about the linearity outside of when the cartridge is used with its recommended loading.

"zero impedance" is not zero, the cartridge always sees it's own impedance. The load resistance is added to this value. This flattens the frequency response by swamping the effect of the cartridge inductance.

 

[vulejov]

LM7812/7912 are very good for this phono..
For C8-C11 is better 1uF polyester, there is no use of electrolytic capacitor..
For C3 use MKP..

 

[rjm]

A heavy-modded Phonoclone RC board from some years back. Nice work. You might want to connect the traces properly at C11, R4 and LM7812 though. Also the hole diameter of the extra pad you added at C3 is too small to be useful...

 

[vulejov]

Thanx, Eagle signalised something wrong but traces are good.. this is your original board, I use it because phono works very nice with LM7812/7912..

There is final version, 100 Ohms load is optimal for most cartridges.. gain is 64 dB, enough for my amp but who wants more it is better to change R3 than R4..

First chip is LT1028 and I will try LT1115, but dont expect any difference... second chip is LT 1028 but this is not so important like first one.. thinking about LME 49710 for second..

 

[pdg]

one 3nf instead of 3 1nf for C2

@rjm
Hi Richard.
Is there any specific reason that you've specified 3 1nF(1000pF) in the RIAA equilization of the PC3 instead of a single 3nF cap?

thanks, Philip

 

[rjm]

Simply because 3 nF is not a standard part value, and its more efficient to buy lots of a single value rather than small quantities of several different parts.

/R

 

[pdg]

Simply because 3 nF is not a standard part value, and its more efficient to buy lots of a single value rather than small quantities of several different parts.

/R

Thanks Richard. Digikey has the 3nF from the same manufacturer as you specify in your BOM with the same tolerance and lead spacing as the 1nF and I'll save myself about $10 which I can spend on possibly upgrading the coupling cap's. Philip

 

[downhiller2010]

What is the estimated USD cost to build the VSPS dual board version?

 

[Bibio]

i'll admit from the start i know nothing about electronics.

i would like to know what would happen if you wired up 2 transformers like the picture below. this is for one mono board

An externally hosted image should be here but it was not working when we last tested it.

 

[vulejov]

This is final version.. I hope so.. RIAA curve is very accurate..

Is there any reason for such big transformers.. it works very smooth with 1.9 VA board mount transformer..

 

[rjm]

What is the estimated USD cost to build the VSPS dual board version?

Total finished VSPS 300 at single quantity pricing and bom parts would be about 200 usd.

 

[rjm]

i'll admit from the start i know nothing about electronics.

i would like to know what would happen if you wired up 2 transformers like the picture below.

Don't do this! Transformers cannot be connected in parallel!

 

[troystg]

Agreed, transformers can't but secondaries can.

If he parallels the secondaries of the transformers he doubles the current in a safe manner.

 

[pfcs49]

Don't know a lot, but I bet you'd better get the primaries in phase to do this.
And wouldn't the primaries be in parallel to the AC voltage source??