Atma and bias tubes

  • Thread starter Thread starter roccster
  • Start date Start date
roccster

roccster

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Anyone know if you have to bias the tubes on the Atma after replacing them?
And if so, how?

Cheers!

/ Richard
 
Since it's Class A, no bias is needed. Just make sure you get a good matched set.
 
Great!
Thanks for quick answer.

Another thing you might be able to answer. I feel like Im wearing out tubes rather quick. And It is more noticeable when running in 1w mode (i get that 60hz kinda hum and some crackling when cold). When running in 18w there is not that much hum. When replacing with a fresh set of tubes the hum is much "better".

I play the amp at least 1-2 hours a day, mostly in 1w.

Cheers!
 
As the tubes get older you may be noticing some wear/drift which could be the tube hum you hear.

Do you notice more or less in 5w mode? Are you still running JJ tubes when you changed them?
 
Bogner Amps":1x1e2ujw said:
As the tubes get older you may be noticing some wear/drift which could be the tube hum you hear.

Do you notice more or less in 5w mode? Are you still running JJ tubes when you changed them?
Click to expand...

Yep, still JJ tubes, and the hum is basicly identical in 1 and 5w. There is a noticeable drop in the hum when toggeling the vintage/modern switch to modern.

rgds
/ Richard
 
Just for reference,

I just came home after buying a new EZ81 and two new el84.
Before and after files, filmed through iPhone, same set up, both in 1w mode (vintage).

1w old tubes


1w new tubes


Guess it eats alot of tubes :)
 
Bogner Amps":2kztpdio said:
As the tubes get older you may be noticing some wear/drift which could be the tube hum you hear.

Do you notice more or less in 5w mode? Are you still running JJ tubes when you changed them?
Click to expand...

What is the lifespan on tubes in the Atma? The other day my TAD EL84s that I bought in April decided to throw in the towel.

I play on my amp pretty much every day, at least one hour in 1w mode (at home that is and 18w at rehersals) and my Atma seems to eat tubes alot. The TAD EL84 was much better then the JJs though, and just started to give away that nasty hum just before they pretty much gave in.

So is it normal for these amps to wear out tubes this fast?

rgds
/ Richard
 
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