ADCOM GFA 555 II

[Guido]

From my previous work as an ADCOM warranty guy here in Winnipeg, I remember some flameproof ground float resistors opening on a few occasions. If you feel handy and have a multimeter. I would check R104 and R154 (one in each channel) They are 100 ohms-1/4 watt and don't show any signs of heat when they open. They also cause a DC offset which your woofers will not like !! They are located on the small input board at the rear.

The resistors are ok. Funny thing is that the are 50 ohm types in my Adcom.

Thanks for help and the schematic.

Do you have an idea regarding the hum(ing) A-Bus module?

[boputnam]

It was the russound A-Bus Module connected to my Rotel RC-972 that caused the hum. With disconnected A-Bus Module everything is fine.

Nice one, Guido!!

With GL's it's always best to start nekked, with everything unplugged from the preamp and then work into it, one component at a time...

Soory - I'm ignorant on the Rotel line...

[Guido]

What to do with the A-Bus?

Connect it with chinch cables that have connected shield only on one side?

[boputnam]

What to do with the A-Bus?

Connect it with chinch cables that have connected shield only on one side?

No. I think you should try an induction coil - we need to isolate that A-Bus AC/DC power supply converter (that is the problem) from the signal ground.

Here in the States, Radio Shack makes a great in-line GL Isolator.

http://www.radioshack.com/product.as...t%5Fid=270-054

I've used these between the pre-amp and the offending peripheral device, when needed. Work great with little / no degredation of signal strength.

[Guido]

Thanks for the Help Guys.

This Adcom really is a killer. Power without limits on my 250ti.
Can't wait to test it on my 4435 (not finished yet )