Valve Itch phono

Is there anything undesirable with a bias ~1.7mV?

Lets say you have 160 V from anode to cathode. Look at the difference in current. Current, or lower Zout is good for working with the resistors and capacitors in the riaa compensation.
 

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diyAudio Chief Moderator
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At 1V or about I haven't found any input valve sample that did not stop grid leak. But they were a few samples. At 1.5-1.7V the bias current is going to go lower by 25% is the effect. That could change THD but not much since the signal is little in a phono input stage.
 
diyAudio Chief Moderator
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If its MM cart the response is going to change. Usually less kOhm means duller treble. Try 68k if you think some MM misses some sparkle, before adding some Cx loading. If its SUT the reflected load to its primary is going to change. Square wave test SUT ringing and THD can also change if not correctly loaded. Most assume 47k on the secondary. Some manufacturers advise snubber also. Like Jensen does.
 
diyAudio Senior Member
Joined 2002
Hi,

MM cartridges aren't that much affected by resistive loading (within reason), capacitive loading has much more effect on their FR.

The actual standard resistive load for MM cartridges is 50K. Since 47K is the most common closest value this is what is commonly used.
I've seen products using 49k9 resistors but they're rare.

With MC cartridges the capacitive load is less influential on overall FR but it's the resistive load that tames the often rising FR. I.e. more resistive loading results in more control of the moving coils.

IOW, if you have high frequency response issues I'd look elsewhere.

Cheers, ;)