SYMMETRICAL CARTRIDGE-CONNECTION

[roberto.missoli]

First of all I would like to tell you I like very much this site, I think is one of best!

I have an idea to build your RIAA amplifier but I don't know if is it compatible  with the connection in attach:

Roberto





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[peranders]

You can connect this pickup to my amps.

[roberto.missoli]

You can connect this pickup to my amps.

Thank you for our answer,
That means have I to use two stereo amps? (Sorry but I am not an expert)

I know normally balanced connections have 3 conductors: positive, negative and ground, in the case of cartriges, which are balanced sources with just 2 conductors - positive and negative, in technical term is floating balanced or balanced without ground. The positive signal is connected to one dedicated amplifier stage and the negative signal is inverted and also connected to one dedicated amplifier stage (differential amplifier).

From your circuit the only way I see to use floating balanced technic is to use one input (right) for the positive crest and the second one (left) for the negative crest.
But are the two amps match for this task?

Regards.

[peranders]

You can connect the cartridge but the signal will be unbalanced since the input is unbalance. You must connect COLD with shield for both channels. If you want a true balanced input you must have a preamp with balanced input or as you mention, using a stereo phono amp for each channel.

[roberto.missoli]

... but do you think I have a really advantage to use a true balanced input? Is it true with this typology I loose 3 db noise figure and is it true that in an unbalanced preamp the noise signal (along with the desired signal) that is superimposed on the leads connecting the cartridge to the preamp will be greatly amplified but not so in a balanced system?

I read that in a true balanced amp the noise, which is common to both the plus and the minus leads, drops out of the amplification process because of the inability of a balanced preamp to amplify what is common to both of its inputs, its common mode rejection ratio (CMRR).

[peranders]

The main reason for having balanced signals is when you have a nasty environment and long wires. It is always an advantage to have a true balanced input but why does your turntable has this wiring in the first place besides it's impressive?