The Phonoclone and VSPS PCB Help Desk

[Leeuwarden]

The calculator is in the BOM of the PhonoClone... Lets see if I can get the math right...

 

[Leeuwarden]

My calculations:

Sumiko BluePoint EVOIII Specs:

Load Impedance 47k Ohms

Output Voltage/Channel 2.5mV

Calculating with Richards spread sheet makes:
See attached picture.

Am I doing this right?

 

[kor952]

Hi Leeuwarden,

You need the internal resistance of the coil not the load impedance.

Gr.

Ronald, Amsterdam.

 

[Leeuwarden]

Hi Leeuwarden,

You need the internal resistance of the coil not the load impedance.

Gr.

Ronald, Amsterdam.

Thanks, I'll see if I can find that somewhere...

 

[Leeuwarden]

Hmmm that seems a difficult question to find the resistance of the coil. It's not mentioned anywhere...

 

[kor952]

It will be somewhere between 50 and 120 ohm for a high output MC.
Did you try vinylengine.com?

 

[WntrMute2]

Ill be able to help this evening

 

[Leeuwarden]

Yes, it is not mentioned either...

 

[Leeuwarden]

Ill be able to help this evening

That would be great!

 

[kor952]

The internal resistance of the Blackbird is 135 ohm, I do not think there will be much difference between the internal resistance of Blackbird and Bluepoint special etc. I think a resistor of 120 or 150 ohm (instead of the 47k you calculated) will do perfectly. This resistor balances the two inputs of the op amp.

 

[WntrMute2]

OK, I just got my resistors for the above Phonoclone and have another question. For R1=135, should I undershoot with a resistor value of 121ohms or overshoot with 150ohms? Same thing for R2=540, under at 511ohms or over at 562ohms. Thanks in advance.
Dave

Here is my earlier conversation with Richard. I would order one set over and one set under as the exact values are hard to source.

 

[Leeuwarden]

Thanks! I contacted the importer of Sumiko also. I'll wait a couple of days and see if he comes up with the exact specs. If not I will use your values.

 

[naimster]

Hi,
I was wondering anyone attempted to change the active RIAA network at the 2nd stage from RC to LCR type? Wonder if this is worthwhile investigating given that LCR is supposedly a more accurate RIAA network.

 

[WntrMute2]

One thing I did is to solder sockets 1-1571994-0 Product Details - TE live these into the resistor holes on the board. That way I could try different ones out or go back to stock vales if I wanted to try a LOMC cart. Just cut it apart into single sockets and solder them in. I'll see if I can find a picture of what I did to clarify.

 

[Leeuwarden]

I know these sockets! I think I even have them in my parts-box. It's a good idea to use these!

 

[WntrMute2]

You can make out the sockets under the blue potentiometers. This is another DIY phono stage that uses potentiometers instead of resistors. I did that so I had a wide range of cartridges I could use here too.

 

[Leeuwarden]

Thanks! I will use them too.

 

[naimster]

One thing I did is to solder sockets 1-1571994-0 Product Details - TE live these into the resistor holes on the board. That way I could try different ones out or go back to stock vales if I wanted to try a LOMC cart. Just cut it apart into single sockets and solder them in. I'll see if I can find a picture of what I did to clarify.

Great minds think alike ... I use them too. Unfortunately they are rather small for more some of the more exotic resistors which has a thicker lead. Do you know if there's a version with bigger socket hole?

 

[rjm]

There's a ton of different pins and sockets at Mouser, sold in strips and individually. I suggest you start looking there.

 

[vulejov]

Again a little discussion about RIAA..

Phonoclone spice model..

Two versions of the RIAA network .. which one do you think is more accurate?