VK Music - Elekit & Triode Japan Forum

Welcome! Need support, you got it. Or share your ideas and experiences.

Return to VK Music - Elekit & Triode Japan Forum

VK Music - Elekit & Triode Japan Forum

TU-879S and TU-875 mods

190.19.89.98

Hello there. I have some questions about the 879S and 875 models.

About TU-879S, does the convertion from pentode to triode modify the frequencies characteristics ?? I find that this happens in my guitar tube amps..

What do I achieve by putting the negative feedback circuit out of the circuit and whats the difference on just decreasing it ??

About the TU-875 preamp, is it possible to add 3 or 4 band eq ??

Follow Ups:

RE: TU-879S and TU-875 mods - vkung 21:19:12 10/23/11 (0)
Change to ultra-triode connection
When you add a small signal transistor to the first stage, it becomes an ultra-triode connection by using the 12AX7 triode as the feedback device. (See below.) You can obtain high quality bass as this will reduce distortion drastically - home page for the ultra-triode connection.
http://www.ne.jp/asahi/evo/amp/TU-879R/reform1.htm
Reduce the amount of NFB or turn to no feedback
You can reduce the amount of NFB by increasing the resistance Rnf towards triode cathode that is running NFB from the secondary output transformer. (In reverse, the amount of NFB will be increased by decreasing the resistance. This is not recommended as the performance will not be stable.) Once you remove Rnf, it becomes a non feedback amplifier. (Cg can be removed if it is preferred.)
http://www.mizunaga.jp/879sinf2.html#3
Advantages of NFB:
Better frequency response, less distortion, less gain or voltage drift,
Disadvantages of NFB:
Less gain.
Possible oscillation if not properly designed.

Regarding TU-875:The chasiss of Tu-875 is too small to add 3 or 4 bank eq.

Edits: 10/23/11

Post a Followup:

FAQ

Post a Message!

Forgot Password?

Moniker (Username):
Password (Optional):
	Remember my Moniker & Password (What's this?) Eat Me
E-Mail (Optional):
Subject:

Message:	(Posts are subject to Content Rules)

Optional Link URL:
Optional Link Title:
Optional Image URL:
Upload Image:
E-mail Replies:	Automagically notify you when someone responds.

To view your new posting or follow-up, click on the RELOAD or REFRESH button on your browser.

This post is made possible by the generous support of people like you and our sponsors:

VH Audio