2. amps-preamps
  3. 166424-2183

Can’t use any other tube??!!?

I just got a used Rogue Cronus Magnum 2, and I want to roll a few tubes I have into the center 21au7 spot to see if I can beat the stock JJ.

Every tube I try is noisy - crackling and hissing. Even tubes that I take from another amp where they are crystal clear.

But when I put the JJ back in - it’s quiet again.

I have tried new production Mallard and two different NOS Mullards.

Any ideas why only the stock tube is working? 


stephenjess
jjss49's avatar
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jjss49
6,612 posts
 
It's a pre-amp section that is sensitive to noisy tubes. Very common. Call Upscale audio and they will set you up with some good choices.

^^^ this ^^^

new production mullards are not real old stock mullards, nothing to do with them other than the name, which has been purchased by the russian tube maker

you need real noise screening on the tubes, need to buy from someone who can do this... search other threads for old stock tube dealers - kevin deal is one of them, 4-5 others out there who do this properly
russ69's avatar
russ69
3,523 posts
 
"...It can be reduced, but not completely eliminated..."

All 5 of my tube driven systems are dead quiet. YMMV
atmasphere's avatar
atmasphere
11,862 posts
 
Any ideas why only the stock tube is working?
In any high performance tube equipment the tubes are hand-picked. Your 'replacements' are not. They are just random tubes. You need a 12AU7 that is picked for low noise and low microphonics.
oddiofyl's avatar
oddiofyl
3,947 posts
 
Agreed.... my preamp is very sensitive to noisy tubes.   I have a JJ 6922 in there now.   Just put a brand new Gold Lion in,  noise.   The Gold Lion tube is dead quiet in amp but rush in pre. .   So i put the JJ back in.   Sounds very good,  not quite as good as the GL...still sounds really good, just different .   Im going to order a super low noise tube .....
avanti1960
1,487 posts
 
It can be done!  I tried dozens of preamp tubes on my old CM Ii.  Excellent sounding amp that upgrades nicely with small signal tubes. 
See Brent Jesee Audiotubes.com.  Spec  low noise screening for an extra 10 bucks.
My favorite was Amperex NOS.  Buy an off label Amperex and save $
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