Question Setting Bias on AKSA 100

[dgarner]

Hi, I needed to replace a fuse in my amp so opened it up for the first time in around 10 years.

After replacing the fuses I wanted to check the bias and performed the following actions:
-ran leads to the emitter terminal on T7 & T8.
-played unit on a loud setting for 20 minutes
-Set meter to 200mv range
-recorded the following readings after 30 seconds idle time
Left Channel 55mv
Right Channel 48mv
-Let the unit settle for 15 minutes and recorded the following
Left Channel 54.5mv
Right Channel 58.2mv

Based on the instructions something does not seem correct with the Left Channel.

Did I do this correctly and what should I do now?

PS: I am not electronics savy!

Thanks,
Darin

 

[AKSA]

Darin,

That's fine. Bias current is highly dependent on thermal and indeed mains voltage conditions. It does move up and down and is very difficult to get precisely equal.

However, small deviations, +/-10%, have very little sonic effect.

Cheers,

Hugh

 

[dgarner]

Hugh,

Hope your doing well; it's been a long time since I bothered you!

From the looks of all your products you have been busy; I am going to get one of those GK-2 from you when they are ready.

On the bias settings its wasn't the variation from left to right that worried me; it was that the lack of change on the left channel after idling for 20 minutes after running hard. The right channel operated as I expected.

Thanks,

Darin

 

[AKSA]

Darin,

sorry for late reply.

Be absolutely sure that all output devices are screwed down tight onto the heatsink; this ensures that thermal equilibrium is uniform across the two modules.

If the left channel is constant, and quiescent never varies, I would ascribe it to a lucky coincidence of tempcos on the bias generator/output devices, and not even think further about it!!

I will put you down for the GK2, which matches very well with the AKSA.

Thanks for the post, Happy New Year to you and your family!

Cheers,

Hugh