6em7 And upgrades

[tttubes]

Just picked up a used s.e.x. Amp and i have a bunch of 6em7's was wodering if the older amps can be converted. Also what would you think are must have upgrade I have already changed the signal caps.

[tttubes]

Anybody ?

[Paul Birkeland]

How old is the SEX amp?  The 6EM7 works in the circuit, but you need to change a couple of caps and resistors to do so.  It ultimately works much, much better if you have constant current sources available, as the stock driver plate load resistor is a little on the low side for the 'EM7.

[tttubes]

I'm not sure of the age but it has speco transformers.

[Paul Birkeland]

You can send me a PM with your e-mail address and I'll send you a copy of the manual, then I can direct you to the pages and parts that would need to be swapped out to use 6EM7's.

If you already have the manual, let me know and I'll post away.

-PB

[tttubes]

Paul I have the manual and have a c4s on order.

Thanks

Jim

[Paul Birkeland]

OK, on page 30, you will see the note about substituting a 1.6K 10W resistor.

What is left off is that the 1000uF/35V cap across that resistor will now see just about exactly 35V, which is especially risky since the cap has been seeing low voltage for its whole life, so up the voltage rating to 50V /(63V is OK too).  You can also drop the value to 470uF if space is an issue.   

On the SEX C4S, change the R1 value to 1000 ohms, leaving everything else the same.  (You will need to drill a small hole in your chassis to mount the board, no big deal though).

-PB