• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Fisher 800c Alternate Tube

H

Hi-FiGuy

AK Subscriber
Subscriber
I was looking at the schematic for the Fisher 800c and thinking about tube alternates. Has anyone ever tried to use a 7427 / 12DW7 right in front of the output tubes? Pins 678 are the 12ax7 and pins 123 line up with the 12au7. Im thinking that would be perfect as a gain followed by a driver tube. Would the au7 section work better than the ax7 section with this substitution?
 
Register to hide this ad
first, why?

You'd have to modify the stage to properly re-bias the tube so it would work. A 12au7 section would draw a fair bit more current. Not sure that it would offer any advantage either.
 
I was just wondering if anyone had tried it, I am currently using some ribbed plate telefunken (Fisher) tubes and the amp sounds great.
 
Hi-FiGuy said:
I was just wondering if anyone had tried it, I am currently using some ribbed plate telefunken (Fisher) tubes and the amp sounds great.
Click to expand...
Read the threads regarding the noose phase inverters mod..... Those 12ax7 tubes are very important esp if it is old stock!
 
Are those tubes not phase inverters? If so and I believe they are then I would stick with the long plate 12ax7's.
 
You must log in or register to reply here.
Back
Top Bottom