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    Building, troubleshooting and testing of these amplifiers should only be
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paralelled tube

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Mas Penk

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Joined 2003
#1
Hi all,
I just wanna know the purpose we paralleled twin triodes together.

All i know if we paralleled twin triodes (let's take sample from 6SN7). in normal condition (not paralleled) ra 7k, mu 20.
but if i paralleled will this 6SN7 have ra 3,5k and mu 40 on same loadline?

thank you for explanation....

best regards
 
#3
Triodes are sometimes paralleled to take advantage of the reduction in RP. (i.e lower source impedance) This allows the use of lower impedances in following stages for a possibleimprovement in snr.

Triodes (basically gaussian noise sources) in parallel noise power reduces by 3dB for each doubling in the number of tubes paralleled. (If I recall the relationship correctly.)

Note that unfortunately while the above are both advantages miller capacitance doubles for one pair in parallel, and quadruples for two pairs in parallel ad infinitum. :bawling:

I used paralleled 5751 in some of my early passively equalized phono pre-amplifier designs which were intended for use mainly with mc type cartridges and they were substantially quieter than single tube implementations. You would want to be very careful about doing this with cartridges that don't like substantial amounts of loading capacitance.

Kevin
 
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