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

Showing 1 response by oldhvymec

OP you know anyone with a valve tester?

It's pretty simple you have a piece of equipment that only one valve in the world will work, just ONE.. I hope they or IT doesn't go bad..:-)

No I'm just joking. BUT the valve (tube) tester will tell most of the story.

You have some noisy valves and BAD contact could be some if not all of your problem.. Just because they sound OK in one unit may just mean you have better contact on the pins, from one to the other..

Does that happen very often? Ask a bench tech that works on valve amps A LOT. 

101 valve maintenance. Check the valve pins and SOCKETS for cleanliness. Tighten and clean the pin pockets AS NEEDED...

Take the questionable valve, a wad of cotton and a little WD40 and spray the cotton ball with wd40. Plunge the pins several times into the cotton.
Be aware of the silk screening on some old valves. The WD40 might loosen or stain the printing.

IF that doesn't help, which it will no matter the change. It is always a good idea to start from the side of "I checked it correctly" and that cleaning really made a difference..

The long and short of it is. 

First clean the valve and pockets and tighten them if needed

Second, test the valves you have OR buy a pair of noise free valves from a good supplier.  Tell the supplier what your problem is.. NOISE.

Just so you know transportation of valves is NEVER guaranteed. If they bounced across the US and were thrown on the front porch..

TWO week is a wise mans approach.. Keep an eye out.. BUT usually the first 2 minutes to the last of 24 hours is a good sign they survived the transportation experience AGAIN. They will probably have a long life..

Happy hunting..