Starting this month I am scaling back the monthly WPKN FM radio show to one…
Im back from 2 weeks in Japan, time that I primarily spent hunting for records.…
Available now on LoveAllDay Records : the new LP "Secular Music Group Volume 1"- avail on vinyl…
This month's Preservation Sound Radio program will air tonight Tuesday May 21 at 8:30 PM.…
This month on Preservation Sound Radio: nine side-filling tracks from 1970 thru 1986, all from…
This month's show airs Tuesday 2.20.24 at 8:30PM -11:25PM EST on WPKN 89.5 FM in…
View Comments
The 6AS7 has a mu of 2 or thereabouts, which means it needs a LOT of drive.
Using a driver transformer is one way to do it.
Using a power supply with a straight output in the 200 volt range (it's a low B+ design too) and a voltage doubler for the driver section, or a tapped PT secondary, would be another. The driver tube needs to swing as much as the B+ of the output tube itself, so must have nearly twice the B+ itself.
With the 807, it is the plate, not the grid, that is on the top cap.
The very cheap 1625 is identical to the 807, except that it has a 12.6 Volt filament.
All the best,
Kevin Strom.
The 1625 also has a seven pin base. The 807 has a five pin base.
Figure 2 is the Curtis Schafer amp in the first Audio Anthology. It would be a good thing to reprint Mr. Schafer's comments on these.
I met him in the late seventies: he was still active then, and that was in Chicago as I recall. I remembered his name from an article in one of the audio magazines at that time and we talked, but not about this stuff. If I had only known....
There is no way a 6AS7 is going to give thirty watts out.
In push pull with itself maybe ten, probably less. NEVER try to parallel the triode sections, they always differ a lot because of how the tube is made.