tail resistor phase inverter jcm800 2203

[giordydiver]

hi everybody, i have a jcm800 sir 34 with 6550. sir 34 have a 22k tail resistor PI , i know that it is more balance than 10k but what is the difference in term of sound and tone? is true that with 150k on gain pot, as sir34, 10k make a thin sound? I see more difference ideas about 10k and 22k.

thanks

[neikeel]

Only you can decide, try both combinations.

22k lowers volume a smudge, adds a little compression to my ears - subtle, I have used 15k and 18k too

The 150k on the pot makes the amp more manageable when you have all the cathode bypass caps on.

Try for yourself

[herbvis]

The tail r appears to be connected to the nfb r. I am guessing so correct me if I am wrong please, but I assume the value used would directly affect or have the most influence on the presence circuit?

[giordydiver]

Ok, what do you thind about the story about 150k on gain pot without 22k PI make a sound like a wah open?

Can i put a swich to select 10k /22k or risk to damage pi?

[Roe]

10k sounds punchier usually. but 22k has better balance and increasing PI voltage can help it to get punchier sounding. Another option is to use a 390k instead of the 1ma on v3a like the park 1210 did. this will also increase the balance of the output stage when running flat out with 100k/4ohms NFB