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Correct load for MM

Started by zz1969, March 22, 2013, 03:40:08 AM

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Hi P-A!
In the circuit discription for QSXM2 you say:

"It's very important to tune the input impedance in order to achieve flat frequency response. If you choose to use the input bias servo (see page 7) the input impedance will be 270 kohms (R97) and if you choose not it's several megaohms (you can ignore it).
R1 together with R97 creates 47 kohms needed for most MM pickups"

R1 - 56KOhm and R97 - 270KOhm. Is that correct? I just can't understand how it results to 47KOhm.
Can you explain?
And how to change load to, say, 10 KOhm?
Thank you. (excuse me if these are stupid questions :)


56 in parallel with 270 = 46.38 kohms

You can of course change the load but the frequency will no be flat and you will loose some signal if you load the cartridge higher.
/Per-Anders Sjöström, owner of this forum

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