Pearl with symmetrical (xlr) inputs? - diyAudio
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Old 27th December 2006, 08:23 PM   #1
h_a is offline h_a  Europe
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Default Pearl with symmetrical (xlr) inputs?

Dear all,

I would be interested in symmetrical inputs (and outputs if possible) for the great pearl. Interestingly I couldn't find any posts regarding this option, so I'm stuck - is this an especially obvious stupid question or was there never really interest in this?

Honestly I haven't have a lot of knowledge about symmetrical inputs/outputs/circuits (xlr), I somehow have the impression it's about differential signaling, therefore the grounds of the channels have to stay separated...right?

What else?

Do the pcbs on passdiy have to be changed for symmetrical inputs? Or is it not possible without major changes?

What happens if I connect unsymmetrical signals? Is there just no advantage (no cancelling) or happens something else?

Would be great if somebody could help me!!

Maybe somebody has some links where I could read a bit more about symmetrical connections/signalling!!

Thanks a lot!!

Have a nice evening and happy holidays!!

Cheers, Hannes
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Old 27th December 2006, 09:44 PM   #2
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in fact-pearl is so simple,that -for balanced operation,technically you need two (bridged) stereo pearls .........
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Old 28th December 2006, 03:02 PM   #3
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Thanks for your reply!

I read a bit about balanced operation in general and as I understand now, a conversion between balanced and unbalanced inputs would be possible via a transformer.

What is really needed to do this conversion?

Could somebody please point me to some information??

I do not want to have 2x stereo pearls to get balanced inputs, a conversion would probably be sufficient.

Any disadvantages?

Thanks a lot for helping me further!!

With kind regards, Hannes
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Old 28th December 2006, 05:56 PM   #4
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The Pearl is a single-ended circuit. As such, you can't use it to amplify balanced signals. There's no easy way to make the circuit handle balanced inputs or outputs; to do so, you'd need to redesign the circuit.
A transformer would allow you to use a balanced input. Connect the positive phase to one end of the primary, negative to the other, and ground in the middle. Then use one end of the secondary to drive the input of the Pearl and ground the other.
To get a balanced output, you could use a transformer at the output (hooked up opposite the discription above) or a differential circuit, which would create the opposite phase out of thin air, so to speak.

Grey
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Old 29th December 2006, 03:55 PM   #5
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Thanks a lot for your reply!!

How does the transformer affect the signal?

I want to connect moving magnet cartridges which have an impedance of about 1kOhm. It is extremely important for a good frequency response to have the proper capacity in parallel to the pickup, it's usually (including the phono cable) around 150-250pF (RC-circuit).

Since the cartridge also has an inductance of roughly 300mH I expect that a transformer with several Henrys (!) is going to have an impact on the signal/phase.

Am I wrong here?

What transformer is better suitable for cartriges with roughly 1KOhm impedance? Mic or line?

Thanks a lot for your help!!

With kind regards, Hannes
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