The Phonoclone and VSPS PCB Help Desk

rjm

Member
Joined 2004
Paid Member
Re: thanks AHAJA

juluska said:
Now i'm going to change the riaa network with your modifications. Can you explain with plain words hows this modifications can improve the sound?

At high frequencies you extend the feedback loop to include the electrolytic capacitor (and the 47 ohm resistor). This, simply put, makes the op amp work to compensate for the capacitor distortion. The distortion is reduced, but the op amp has to work harder.

The potential problem is at high frequencies, where the op amp doesn't have a lot of control available, but the capacitor distortion and inductance are potentially quite large. Forcing the op amp to chase after the capacitor could cause more distortion than it cures. I say that as speculation, I don't know for sure.

The other change involves 47 ohm resistor. It was included to isolate the opamp from the capacitance/inductance of the output, improving stability. If you put it in the feedback loop, it's effectiveness in this regard is much reduced, but the output impedance is lowered from 47 ohms to ~<1 ohm. How that change effects the sound is going to be very dependent on the situation, what cables are used, etc. It is "safer" to leave the resistor out of the feedback loop, as shown in the figure below, but unlikely to make a great difference either way.
 

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VSPS

I intend to build a VSPS phono stage with 40dB gain using PCB that I ordered from Akito and parts sourced from Farnell. This VSPS is to be mated to a Denon DL160 high output MC cartridge (measured output claimed to be 2.2mV as opposed to published specs of 1.6mV).

My questions:-
1) I have a Burr Brown OPA2111 opamp, would I be able to use this opamp in the VSPS? Do I need to change value of any caps or resistors to 'optimise' performance of this opamp?
2) I am building a VSPS to match the Denon DL160 MC cart solely and not make it an allrounder with other MM/high-output MC carts. Would I benefit from use of OPA2211 opamp reputed to sound good with MC carts in a VSPS?
3) I have narrowed down my choice of RIAA caps to either Wima FKP2 1.0nF polypropyrenes or Cornell Dubilier silver mica caps. Which of these 2 caps would be better suited to the Tyco 1/4W carbon resistors that I planned to use and to my Denon cart?

Opinions and advice highly appreciated. TIA.
 

rjm

Member
Joined 2004
Paid Member
Phonoclone Gain Calculator

Worksheet to determine the required values of R1 and R2 in the Phonoclone schematic, such that the output voltage is gain matched to a CD player.

For those with VSPS, it's easier.

First convert the cartridge output to decibels:

20 * log (output in mV / 1000)

You get a number, say -50 dB.

Take the absolute value, 50 dB, and subtract 10 dB. You get 40 dB. That's the VSPS gain you should use.
 

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Hi,

I am a little bit ashamed of my question, but I am a genuine newbie, I tryed a search in this thread without success.

I am going to build the VSPS phono-pre (pcb and components from skycoral.com), but I do not know how to mount the ne5532 op-amp on the board, indeed I have two choices turning the op-amp 180 degrees.
The op-amp I have is symmetrical (except for the op-amp name printed on the top) and there is not the small cut specified in the drawing on the pcb. The op-amp data sheet didd not clarify me.

Can I try what position is working without the risk of damaging the pcb?

Thank you for your help

Renato
 
northernsky said:
Hi,

I am a little bit ashamed of my question, but I am a genuine newbie, I tryed a search in this thread without success.

I am going to build the VSPS phono-pre (pcb and components from skycoral.com), but I do not know how to mount the ne5532 op-amp on the board, indeed I have two choices turning the op-amp 180 degrees.
The op-amp I have is symmetrical (except for the op-amp name printed on the top) and there is not the small cut specified in the drawing on the pcb. The op-amp data sheet didd not clarify me.

Can I try what position is working without the risk of damaging the pcb?

Thank you for your help

Renato

I think the only package without the small cut is the SO8 and the drawing has the same orientation in all op-amps.

http://ignatiusprojects.blogspot.com/
 
Ok Need help!!

I finished mu VSPS base on this board (http://skycoral.com/?p=49).

I used the double schottky diodes rectifier.
RIAA resistor is carbone, all other is metal.
RIAA cap are 1nf Panasonic poly
My output cap is Clary Cap SA.
Opamp: Try op2134 and lm4562 (both sound good)

All the solder joint look perfect, I tested all the resistors, the value is OK

I got issue with my first version of my rectifier.. I miss connected the transfo and burn couple diodes :xeye: and at this time my opamp was not in the circuit.. So I redo my rectifier ...

But now my Right channel play couple db lower that my left.. And I can't figure where is my problem... :bawling: