FEEDBACK /PRESENCE

[RCGPNY1]

Is there a big difference which output tap the feedback loop is connected to? On my triode JTM 50 build it wants me to connect to the 8 ohm tap. I thought original JTM's had this going to the 16 ohm tap (?). I know some folks just connect to the speaker output jack...thoughts?

[Reeltarded]

Yeah big difference. Higher tap is cleaner output and tamed sound.

27k on the 16R is normal for JTM45. What is their idea of a JTM50? JTM45 with EL34s, silicon rectifier, shared cathode, 470k mixers?

[NickC]

Some JTM50 schematics show it attached to the speaker impedance switch. Others have it attached to the speaker jack. Either way, the NFB will be attached to whatever tap is selected/presented to the spkr-jack.


http://www.classictubeamps.com/schemati ... /JTM50.pdf

http://img.photobucket.com/albums/v204/ ... ushall.gif

[RCGPNY1]

Yeah big difference. Higher tap is cleaner output and tamed sound.

27k on the 16R is normal for JTM45. What is their idea of a JTM50? JTM45 with EL34s, silicon rectifier, shared cathode, 470k mixers?

It's tube recitfied with the larger supply of a JMP50. A transitional version...only made for about a year. Yep on the 470k mixers. So the 4 ohm tap will yield dirtier output and more agressive sound? Maybe that's why they are saying the 8R tap...right in the middle.

[Reeltarded]

My original transition model was 27k on 16R. They didn't make that amp for a year.

[RCGPNY1]

My original transition model was 27k on 16R. They didn't make that amp for a year.

So...how long was it made...as the transition was not absolute.