[aln]

I read this in the thread on the 600 R- " Note that this unit was built before we started building in the HumDinger circuits but it runs very quietly here anyway."
Can you talk about when you put this into production on your units?

Thanks!

[avahifi]

The HumDinger is built into all AVA Fet Valve amps that have shipped starting in January, 2013.

Frank

[NIGHTFALL1970]

How much is a retrofit?

[avahifi]

First of all, if you have no transformer hum issues, then don't bother with a retrofit.

Unfortunately a built in HumDinger retrofit in a new series Fet Valve amplifier is labor intensive  The internal AC wiring has to be redone, transformer leads moved, and parts moved and changed on both the inner front panel terminal strip and the bottom of the chassis terminal strip.  It actually is a lot more work than building a separate free standing HumDinger.  I would estimate 2 hours labor and all the internal parts from a Humdinger except the chassis and input and output jacks.

I think it would run $100 plus two way shipping.  This means that a free standing HumDinger is a better value than a retrofit as shipping cost on the amplifier will more than eat up the cost difference.

Regards,

Frank Van Alstine