Do I have a defective Gold Lion 12AX7?

[Dj_AmTraX]

I have a Bellari HA-540 headphones OTL amp that uses ONE 12AX7 tube.
Bellari HA540 Class A Tube Headphone Amp (Our Fav. Standard Amp) [HA540] - $299.99 : Listening Station!, Specializing in Quality Headphones

The problem I am experiencing is I am getting off balanced sound. I've tried two different brand of 12AX7 tubes.

- Gold Lion, right channel is a bit louder than the left.

- Tung Sol (x2), right channel is way louder than the left, almost can't hear the left.

I know it's not the amp because I used a Mullard 12AX7 and a stock McIntosh tube with normal sound so it has to be the tubes. I ran the tubes in for 24 hours and the problem remains.

Your thought on why? Thank you for your help.

[Dj_AmTraX]

no one?

[jdandy]

Mike.......I would contact Bellari, and pose the question to them. With only a single tube in a two channel headphone amplifier, I am not sure what exactly is the tubes purpose. Is it in the power supply circuit or the audio circuits.

You are positive you are connected up properly on either the High or Low inputs, and selected the correct switch position for the input you are using, correct?

[Alberto]

Originally Posted by jdandy

Mike.......I would contact Bellari, and pose the question to them. With only a single tube in a two channel headphone amplifier, I am not sure what exactly is the tubes purpose. Is it in the power supply circuit or the audio circuits.

The 12AX7 is a dual-triode so you can use a single one to amplify two channels. It's the equivalent of two 6AV6 triodes in a single tube.

It's entirely possible that one of the two triodes is defective.

Alberto

[Dj_AmTraX]

If one of the Triodes is defective, is the tube safe to use in a different application, like an amp or preamplifier?

[jdandy]

Originally Posted by Alberto

The 12AX7 is a dual-triode so you can use a single one to amplify two channels. It's the equivalent of two 6AV6 triodes in a single tube.

It's entirely possible that one of the two triodes is defective.

Alberto.......Thanks. It is also possible that the two triodes are not closely balanced. The design of the Bellari is obviously sensitive to the triodes being balanced.

[Dj_AmTraX]

Thanks guys!

[tdelahanty]

It is common to see variances in the gain of tubes or transistors and this is why many manufacturers take the time to sort or match gain on a tube checker or curve tracer for transistors.

[Dj_AmTraX]

I sold the amp because I was tired of dealing with gain issues. I am seeking another that uses TWO 12ax7. Any suggestions?