Solid state rectifier replacements

les_paul

Member
Messages
965
Anyone try those solid state rectifiers that plug into a tube rectifier socket? I'm thinking of doing one for my JTM45 build to help out the lows but I'm a little hesitant. Also sounds like it would need a rebias. I want something a little closer to a 1987 with a little tighter bass if that helps.
 

VICOwner

Gold Supporting Member
Messages
1,880
A proper jtm45 build will have about 450 volts on the plates at idle. A good GZ34 doesn’t sag much compared to the power transformer. The stock filter on the plates of the power tubes is 32uF and between it and the sagging power transformer is where you are going to get the loose bottom end. If you up the filtering of the power tube plates, it will help but it won’t cure the situation. The jtm45 is supposed to perform as it does and that along with the KT66 and the output transformer is what makes it a jtm45. I understand what you’re after but a JTM50 or early JMP circuit will have a firmer bottom. The early JMP and JTM50 don’t have all the aggression of the later circuits because they don’t have the larger bright cap, split cathode or the .68uf cathode bypass caps.
Simply putting in a solid state rectifier is going to make the amp idle at higher plate voltage.
 

easyed

Gold Supporting Member
Messages
2,564
I've had good experience with Weber Copper Cap WZ34 (replacement for GZ34. It performed well in a 69 Super Reverb as well as a DRRI. It includes resistors and diodes and has the same voltage drop as a glass rectifier.
 

les_paul

Member
Messages
965
A proper jtm45 build will have about 450 volts on the plates at idle. A good GZ34 doesn’t sag much compared to the power transformer. The stock filter on the plates of the power tubes is 32uF and between it and the sagging power transformer is where you are going to get the loose bottom end. If you up the filtering of the power tube plates, it will help but it won’t cure the situation. The jtm45 is supposed to perform as it does and that along with the KT66 and the output transformer is what makes it a jtm45. I understand what you’re after but a JTM50 or early JMP circuit will have a firmer bottom. The early JMP and JTM50 don’t have all the aggression of the later circuits because they don’t have the larger bright cap, split cathode or the .68uf cathode bypass caps.
Simply putting in a solid state rectifier is going to make the amp idle at higher plate voltage.
Loud and clear. Perhaps if the funds free up I'll just build a 1987 or something similar and keep this one as is.
 




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