Pentode vrs Mosfet “MU-Stage”

[sgerus]

I'm looking for advice on building a “Mu-Stage” amp
( as described in the Alan Kimmel article)

http://www7.taosnet.com/f10/mustage.html

My current idea is for a 6sl7-6sj7-300B config. The 6sj7 is the pentode for the Mu-Stage.

The question is:
Is using a pentode (vrs a Mosfet) really worth the effort. I would really like to here from someone that has listened to both.

This is how I see it so far:
Pentode Cons:
More space, higher B+, extra iron for pentode heater, bias up pentode heater, higher cost, more holes to drill
Pentode Pros: the amp is 100% tube

Mosfet Cons:
Have added some ss parts (I really don’t mind)
Moset Pros:
less cost and space, overall amp will look better with just 3 tubes (6sl7, 300B and Rectifier)

Thanks, Scott

 

[Giaime]

I think you have answered yourself. Also, please note that a pentode (like any other tube) will have its characteristics variable with age, instead a Mosfet don't show this aging.