The Hum problem: THAT simple.

[maxlorenz]

I had a "little" problem with my second main system. Humm appeared whenever my modified Samsung multiformat player was connected to the preamp... (US$100)

The system:

Samsung multiformat player->unbalanced connection->Darwin source selector /Kookaburra preamp-> unbalanced connection-> Ampslab modified active preamp/modified with balanced output-> UCD 180 amps-> Tannoy Autograph replica (woofers with around 100dB sensitivity with Beyma KX15 coaxials).

I read every paper that Bill Whitlock wrote and tried many options, without success. Using my TVC as preamp made the humm disappear...but I have better use for that unit...

I planned to make a balanced output for the DVD and a balanced receiver for the Kookaburra. Better known products, like SSM2142 and DRV134 balanced line drivers with their respective balanced line receivers were difficult to get. Then I found THAT corporations products which stated better performance than the above:

http://www.thatcorp.com/1600-series_...river_ICs.html

http://www.thatcorp.com/1200-series_...eiver_ICs.html

The later being designed by...guess who! Bill Whitlock himself!
Promising and interface comparable to high quality transformer (without galvanic insulation) for a reasonable cost.

I found a seller of small quantities:

http://www.ka-electronics.com/that1646/that1646.htm

Sorry if I'm not allowed to post that link

The circuits were built using recommended components (see application notes). Non polar Black Gate were chosen where indicated. The power supplies included Teddyregs and OCC copper connections were made.

I could post picks (you miss nothing, really) if ever my daughters lend me their digital camera

How did it work? Extremely well, in fact. Humm is gone even if I am still hesitating how to connect pin1 to ground reference (only chassis are connected). The driver units compliments well DVD's LM4562 output opamp, which is very detailed but lacks body (in my unit), making it more full sounding and with deeper bass, while taking away some of the inner detail (it is still braking-in).

A good experience so far and it's kind of cool thinking: hey, I have a DVD with balanced output !

I wanted to share it in case there are more members with similar problems.

I hope it is useful.
M