2. amps-preamps
  3. 1039394637

Lazarus tube preamp noise ....

Hi all,

After listening for a while on my new tube system I decided to complete the whole tube line by using the Lazarus pre-amp's phono as input to my aux of the Legend preamp. Knowing in advance from the seller that this preamp had some sort of "hiss" I still bought it to experiment. Whoa ... the hiss is higher than I expected kind of ... you know ... like the hiss from a cassette tape but even higher . Here are what I've tried:

1) Leave the preamp on for 3 days in a row . The hiss noise is less dominant but is still there.

2) Change the 12AX7 tubes from Tesla to military 5751 ... Still noisy .. even more .

The next thing I plan to do is to replace the 12AU7's pair but doubt if this' gonna work. My friend recommends to replace all the caps but doing this is a major thing and the last resort if I have to. Any ideas to do next?
dongnhac
marakanetz's avatar
marakanetz
5,473 posts
 
ok 12ax7 tube even if you blow on it can work as a microphone.

make sure and check thoroughly components arround your preamp and try to re-arrange component placements so that transformer is not on one axle with 12ax7 tube(s).

make sure that power amplifier(s) stay away with its powerful power transformers. you can also use tube dampers that will have on 12ax7 probably the largest effect among other different tubes.
dongnhac OP
5 posts
 
Marakanetz,

The 12AX7's are on a seperate board vertical to the plane that the transformer is mounted on. Do I need to move the transformer somewhere else ? Where do I get the 12AX7 dampers?

Thanks,
Don
marakanetz's avatar
marakanetz
5,473 posts
 
Don,
I don't think that you should moove built-in transformer arround in the preamp. I meant different transformers that are in your other components ESPECIALLY in power amp(s).
Tube dampers you can get here on audiogon that are very often advertised for any tube.
Also make sure that your rig is not located close to the AC socket or power line. It is very essential for 12ax7.
You can also modify your unit to use different driving tubes that many tube-files do. I too will probably rework my poweramps to get rid of driving 12ax7 tubes.
dongnhac OP
5 posts
 
Modifying the unit ? That sounds too technical for me as I'm only a beginner in electronics. Are there any literatures that teach ume how to do that? 12AX7 is cheap, using different types of tubes may cost too much ....
More to discover