|3rd July 2017, 12:49 AM||#1|
Join Date: May 2005
Location: Vancouver BC Canada
TU-8600 Why Mr. Fujita used 12Au7 X 2 and 12AX7 X1 intead of 12AT7
This explains why Mr Fujita used 12AX7 x 1 +12AU7 X 2 instead of 12AT7 X 2.
1. To achieve higher stability of NFB, the overall NFB amount is decreased, and instead, cathode feedback is applied to 300B.
(This is why the third winding for cathode NFB is added to the OPT.)
2. Applying cathode NFB requires bigger driving amplitude for 300B.
3. To achieve such large driving amplitude, 12AU7 is more suitable than 12AT7, as its max. rating is higher than 12AU7.
4. Since the gain of 12AU7 is smaller than that of 12AT7, 12AX7 is used for the first stage.
Mr. Fujita conducted the circuit simulation to make sure his theory is correct, and confirmed that bigger amplitude can be achieved when 12AX7x1+12AU7x2 than 2x12AT7.(The driving ability of 12AX7x1+12AU7x2 with TU-8600 circuit is 200V peak-peak without wave clipping)
LL2770 is custom made for TU-8600 as upgrade option
Last edited by vkung; 15th April 2018 at 05:02 AM.
|Thread Tools||Search this Thread|
|Thread||Thread Starter||Forum||Replies||Last Post|
|Lundahl LL2770 for TU-8600||vkung||Elekit||0||22nd June 2017 09:50 PM|
|12AX7 vs 12AT7 vs 12AU7||cl1238||Tubes / Valves||22||27th February 2016 05:05 AM|
|Pavane/ Psvane 845, 805, 211, 12AX7, 12AU7, 12AT7 and EL84||otto88||Tubes / Valves||5||28th November 2010 05:51 AM|
|12AU7/12AT7/12AX7 preamp schmatic needed||Sal Brisindi||Tubes / Valves||6||17th October 2009 04:48 AM|
|12AU7 or 12AT7 instead of 12AX7 ?||Gubby||Tubes / Valves||5||26th June 2004 12:31 AM|
|New To Site?||Need Help?|