6SN7/6SL7 swap...

[BuzzK]

We're talking a cheap magnavox amp here, not a Carver or Fisher tube amplifier and such.

Fair enough.

But what you recommending for this guy's Magnavox is, IMHO, bad advice for the other amps you mentioned. If you don't provide more complete information, or at least a clear caveat up front about the recommendation(s), then why wouldn't the OP walk away from the conversation thinking the principles apply to any or all tube circuits?

Buzz

 

[cademan]

Fair enough.

But what you recommending for this guy's Magnavox is, IMHO, bad advice for the other amps you mentioned.

Not other amps, just for the Magnavox. I own 3 of these that are heavily modified using a 6SN7 tube instead of the 6SL7 tube in place of the 12AX7 tube. 6SN7 just sounds better.

If you don't provide more complete information, or at least a clear caveat up front about the recommendation(s), then why wouldn't the OP walk away from the conversation thinking the principles apply to any or all tube circuits?

Buzz

Guess I'll have to! :thmbsp:

 

[knockbill]

Can you get away with it? Probably.

Will it be optimally biased? Surely not.

Typical operating points for a 6SL7:

Grid -2V
µ = 70
Plate resistance: 44K

For the 6SN7:

Grid: -12V
µ = 20
Plate resistance = 7K

Surely more distortion, different FB characteristics, etc.

Not recommended without circuit redesign!

What needs to be changed to use 6SN7 in the original Maggy 175 amp?

Regards,
John