How to connect a mono cartridge

[willo1]

Hi all,

How to connect my two pole cartridge to my NAD PP4 preamplifier? I have a stereo system and thought to divide the + and - on the cartridge into two signals: left and right.
My question is now: Could it harm the preamp if the ground signals are connected?




Kind regards, Willem

[Chris65]

No, it will not harm your phono stage.
You can connect both +ve leads & -ve leads at the cartridge to combine signals, presuming you are using a stereo tonearm.

  

[willo1]

Thank you Chris. Kind regards, Willem

[analogadikt]

No, it will not harm your phono stage.
You can connect both +ve leads & -ve leads at the cartridge to combine signals, presuming you are using a stereo tonearm.
 

It seems to me that this arrangement shall halve the load resistance? Wouldn't that change the sound signature?

Regards,

[Chris65]

Yes Anwesh, if you mean the phono load impedance that is indeed the case. But since the OP did not provide much information, no mention of tonearm (stereo or mono), mono Lp’s/78’s? regular mono use or just occasional, details about the phono stage, GE pictured but is that the actual cartridge? etc.....I just suggested an ‘easy’ solution

[willo1]

Dear Chris and Analogadikt,

Do you think the results from the impedance being divided by two, leads to significant changes in the characteristics? If you think this will change the characteristics too much is there a solution besides from buying a second preamp.

My tonearm is stereo All-Balance from apr 1960 and the mono cartridge is indeed a GE VR II mono with two needls, 78: saphire 2,5 mil and 33 vinyl: diamond 1 mil.
My preamplifier is a NAD PP4 stereo amp. 100 ohm/180pF (MC), 47 kohm/200pF (MM)
For stereo a Denon DL-160
Mono and schellac the GE VR II  ( I have quite a collection of pre 1950 schellac's, most old Dutch comical repertoire. Now I like to digitalize some of those.

Kind regards, Willem

[Andr039]

to add a mess a bit.
what's the reason to connect the stereo to mono like on the second scheme?

[niclaspa]

Willem, I found this thread where Alexey writes that he finds GE VR-II sensitive to load impedance and capacitance: https://www.lencoheaven.net/forum/index.php?topic=6304.0  He has found 80-100 k as the best load impedance.

If you can handle a soldering iron it might be possible to change the resistor that defines the input impedance of your phono stage.  There is a 47 k resistor parallell to the input of each channel.  If you change them to 160 k - 200 k, you will get half of that as input impedance with the connection that Chris showed.  You will also get 400 pF input capacitance with this arrangement.  For many cartridges, this is too high, but I have no idea what GE VR-II should be loaded with.

An alternative is to use only one channel in your RIAA stage and connect the single channel to both channels in you preamplifier, e.g., by using a Y-connector.  In that way, you will have 47 k input impedance and 200 pF input capacitance.

[analogadikt]

An alternative is to use only one channel in your RIAA stage and connect the single channel to both channels in you preamplifier, e.g., by using a Y-connector.  In that way, you will have 47 k input impedance and 200 pF input capacitance.

Do this and add a RCA socket wired externally across the input. Then use RCA plug with resistor soldered across it in this socket. This resistor shall be parallel to the 47k that is inside, using online calculator you can determine the value needed for the external resistor so the combo gives you the   desired final value. The whole arrangement can be fitted inside a little box before the pre, without any modding to the pre. The RCA socket and plug can be substituted with a selector switch with various value registers soldered to it.

Regards,

[niclaspa]

Do this and add a RCA socket wired externally across the input. Then use RCA plug with resistor soldered across it in this socket. This resistor shall be parallel to the 47k that is inside, using online calculator you can determine the value needed for the external resistor so the combo gives you the   desired final value.

The limitation with this arrangement is that you can only lower the input impedance.  In Willem's case, it appears that he needs to raise the input impedance.

[analogadikt]

 Yes. Just checked where I did this recently to modify a tape head input on a vintage Fisher amp. It worked because there was no resistor inside. So my suggestion shall not work.

Regards,

[Chris65]

An alternative is to use only one channel in your RIAA stage and connect the single channel to both channels in you preamplifier, e.g., by using a Y-connector.  In that way, you will have 47 k input impedance and 200 pF input capacitance.

Yes, that would be my suggestion also, knowing more about the set-up.
Use the Right channel to the phono & cartidge loading will be as Niclas states. You may get hum from the Left channel, this can be shorted at the headshell (join both wires together).

There is a sticky in this section about loading GE cartridges, I think 100K is preferred.

Ultimately though a PP4 is not ideal for shellac/78rpm playback. A phono with variable EQ will provide a better listening experience. There are threads here about such phono preamps, solutions include DIY or vintage gear such as Quad or Leak.

[Chris65]

what's the reason to connect the stereo to mono like on the second scheme

Hey Andrey, it’s for vertical cut discs (e.g. Pathé, Edison)

[Pillo69]

According to the documentation of the VRII, the necessary load is of 6K2 for RIAA and 47K for Flat.
I think the load of 23K5, connected to a stereo amplifier is good.

[Andr039]

Hey Andrey, it’s for vertical cut discs (e.g. Pathé, Edison)

"Vertical connections" for vertical Pathe discs.. Unexpectedly   
Thank you, Chris!