Rectifier & Pre's Needed....

[zozoe]

Greetings,,, For my new Morgan JMI amp, I require a new production GZ34, & a few 12AX7's, and want to know who's exceptional glass these days for each type I need.. Many thanks in advance ॐ

 

[beaubrummels]

For pres, I prefer TAD 12AX7STR, or JJ ECC803S long plate, better sound (or I use ECC83S if microphonics are a problem)
For GZ34 I've been using JJ (or NOS GE, but any reason you require new production?)

People on here complain they've experienced failure rates with JJ. I haven't had one fail yet, but YMMV.

 

[Rex_Rocker]

Exceptional... I'm not a tube snob, but if you want exceptional, you might need to go NOS.

Solid and priced OK, I usually work with a recipee of Sovtek LPS on the PI for its headroom and solid output, Chinese for any in-between position because they sound great, and they can handle cathode follower positions (not sure if your amp has one, but better stay safe) and your choice of New Sensor AX7 for V1. I like the Mullard CV4004 or the Svetlana 12AX7SV. Go Tung Sol if you want bright.

What I usually stay away from is long plate AX7's for V1 for their tendency to microphonics, and New Sensor 12AX7's for any cathode follower positions because they can't handle the higher voltage.

 

[El Dunco]

I like the JJGZ34s. Less mushy than the 5U4s. From what I’ve read, they only run about 10 volts less than silicone diodes.

 

[Mikelamury]

While on the subject of rectifiers, can a 5U4 tube be replaced with anything without Changing the bias?(say on a mesa/boogie amp)

 

[JMP/HBE]

While on the subject of rectifiers, can a 5U4 tube be replaced with anything without Changing the bias?(say on a mesa/boogie amp)

Boogie Rectifiers do not have bias trim pots to change the bias but some Recto's have pads on the PCB's for a trimmer.
Switching from 6L6 to EL-34 does change some voltage in the bias circuit.

 

[beaubrummels]

While on the subject of rectifiers, can a 5U4 tube be replaced with anything without Changing the bias?(say on a mesa/boogie amp)

FYI a 5U4 requires a 3 amp filament current. AFAIK the GZ37 is the only other 3 amp filament current rectifier. Most all the other rectifier types have a 2 amp filament current. I think you can step down to a 2 amp filament rectifier and it will work, the concerns are more going the other way, trying to step up. But it may require changing other components in your amp to work with the different rectifier. I'd probably side with replacing like-for-like tubes, unless you are trying to change specific behavior of the amp and you know what tubes and components will effect that change.

 

[beaubrummels]

Can't edit my post, but needed to add: Changing to a different rectifier type will change the power output and the sag and other behaviors of the amp.

 

[Mikelamury]

Can't edit my post, but needed to add: Changing to a different rectifier type will change the power output and the sag and other behaviors of the amp.

Good to know, your first post answered my question perfectly. I'm not planning on switching the rectifier, I was just wondering if there were any suitable replacement for my own knowledge.