Which one of the above IR LEDs is preferred for Valve Itch?
My guess and 2 cents is that it might depend on the tube samples. I have thought of test where grid current starts at some samples I have but I havent gotten around it yet. A couple of 100 mV bias above the medium value would be preferable for some aging safety etc.
The HLMP K150 is a beauty to for applikations working at 1,6-1,7 at 1 mAish also
Thanks.
It looks more linear than others around 1mA.
My guess and 2 cents is that it might depend on the tube samples. I have thought of test where grid current starts at some samples I have but I havent gotten around it yet. A couple of 100 mV bias above the medium value would be preferable for some aging safety etc.
Is there anything undesirable with a bias ~1.7mV?
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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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.
So, would bias of between about 1V to 1.3V be ideal?
OSRAM SFH 4550 looks suitable for about 1mA 1.2V going almost straight up
Also VISHAY TSAL6200
Still suitable?
Still suitable?
Yep. Will work
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.
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,
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,
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