Modded my La2a. 12ay7. Very happy!

[BluegrassDan]

I did the "CJ Mod" to my ptp La2a the other night. Swapped out the 12ax7 for a GE 12ay7 and changed the plate resistors from 220k to 100k. Also, added a small bypass cap to C4 which helped straighten out the standard 10k dip in frequency response. It's just about flat in frequency response now.

Sounds less woolly in the midrange. Love it!

 

[andyfromdenver]

thanks for the report 

I imagine down the road I will be tempted to f with mine, but for now I don't want to take it out of the rack ever again!! ;D

"Sounds like (insert hamburger metaphor)"
Andy

 

[Di_Sousa]

Also, added a small bypass cap to C4 which helped straighten out the standard 10k dip in frequency response. It's just about flat in frequency response now.

Really?
I didn't know that, do LA-2A have a dip at 10Khz ?

thanks

 

[emrr]

Really?
I didn't know that, do LA-2A have a dip at 10Khz ?

That would be transformer dependent.  As described, the bypass cap doesn't make any clear sense.