AudioAficionado.org  

Go Back   AudioAficionado.org > Audio & Video > Tubes & Valves

Tubes & Valves Upgrades, Spares & General Comments

Reply
 
Thread Tools Display Modes
  #21  
Old 05-21-2022, 08:40 PM
ycxc16588 ycxc16588 is offline
Guest
 
Join Date: May 2021
Posts: 4
Default

ust want to share some experience with tube rolling in MC275 MKVI. My tube rolling in MC275 was limited to small tubes, mostly the two 12AX7 in V3/5 as phase inverter. The preamp I used is McIntosh MX110Z recently fully restored at Audio Classics. The speakers are Rogers Studio 1A. I first replaced the 2 stock 12AX7 with Amperex orange globe 12AX7/ECC83. The sound became more transparent and neutral (not cold or thin). I also tried Siemens E88CC in V3/5 and it sounded really good (more vivid and grainless). When I played Mendelsohn's violin concerto op.64 thru Spotify (I used dCS Debussy DAC), it was quite obvious to me that Siemens E88CC sounds much better than Amperex 12AX7. I am not sure if I can ever find a pair 12AX7 that would sound as good as Siemens E88CC. Maybe I can try some 5751.
This is the interesting part. I hear some people claim that E88CC(6922) and 12AX7 are not interchangeable simply because of the difference in filament heating config. The suggested voltage for E88CC filament heating is 6.3V between pin4 and 5 (pin 9 is connected to the shield), while for 12AX7, in series, a 12.6V is applied between pin 4 and 5 with pin9 floating, and in parallel 6.3V is applied between pin 4+5 (4 and 5 are shorted) and pin 9. I measured the voltage drop between pin 4 and 5 in MC275 for 12AX7 with multimeter and found it was ~12.5V. The service manual shows that two 12A*** tubes are on 24V DC in series. Pin 9 is floating. So why would E88C even work in MC275? Why didn't 12V filament voltage burn E88CC? Or maybe 12V filament voltage can still make E88CC work, but can significantly reduce its life?
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Audioaficionado.org tested by Norton Internet Security

All times are GMT -4. The time now is 09:59 AM.



Powered by vBulletin® Version 3.8.10
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
©Copyright 2009-2023 AudioAficionado.org.Privately owned, All Rights Reserved.
Audio Aficionado Sponsors
AudioAficionado Subscriber
AudioAficionado Subscriber
Inspire By Dennis Had
Inspire By Dennis Had
Harmonic Resolution Systems
Harmonic Resolution Systems
Wyred4Sound
Wyred4Sound
Dragonfire Acoustics
Dragonfire Acoustics
GIK Acoustics
GIK Acoustics
Esoteric
Esoteric
AC Infinity
AC Infinity
JL Audio
JL Audio
Add Powr
Add Powr
Accuphase - Soulution
Accuphase - Soulution
Audio by E
Audio by E
Canton
Canton
Bryston
Bryston
WireWorld Cables
WireWorld Cables
Stillpoints
Stillpoints
Bricasti Design
Bricasti Design
Furutech
Furutech
Shunyata Research
Shunyata Research
Legend Audio & Video
Legend Audio & Video