Loud hum on C-2 preamp input

[bennybee]

Hi all,
Title error : should read 'Hum on preamp OUTPUT' ...

I recently purchased a C2 preamp on evilbay in Germany to match my Yamaha T2 tuner.
It is in great condition inside and outside (I needed to open the unit to check the general condition and the possible source of the loud hum).
When I hook it up to my Quad 303 power amplifier, I sometimes get a loud hum, like when you touch the center pin of the RCA plug that is connected to the power amp. Sometimes the hum goes away when working the RCA plugs in and out of the 'power amp' outlets of the C2 a few times.
At first I thought the metal RCA plugs touched the C2 back panel, but that can't be the source of the hum of course. Then I thought about a bad contact inside the C2, since the small board with the RCA connectors is plugged onto the mother board by multi-pin connectors and there is some play on those.
But everything looks great and neat inside...
Now I suspect that the Quad has a problem OR isn't a great match for the C2. The Quad 303 works fine without hum on the Quad 34 preamp though.

What is going on here and what would be a good power amp for the C2? I once owned a Yamaha M4 in a previous life, but these (and all other Yams) are way too big for a third audio system in my home. I need something sleek, like the M35 or MX35? Although these look like they are not worthy of a C2 ?
I must say that the sound from the C2 (on the Quad 303) is impressive and my first impression is that it sounds better (tighter and deeper) than my Accuphase E305.

Thanks in advance for your help and ideas.

 

[avionic]

what would be a good power amp for the C2?

M-2 .. Any of the Yamaha line.

 

[avionic]

When I hook it up to my Quad 303 power amplifier, I sometimes get a loud hum, like when you touch the center pin of the RCA plug that is connected to the power amp. Sometimes the hum goes away when working the RCA plugs in and out of the 'power amp' outlets of the C2 a few times.

Cracked ground solder connections on the RCA jacks..

 

[bennybee]

Thanks Avionic. This more or less crossed my mind but I wrongly ruled it out somehow. I will look into that asap.

 

[avionic]

Verify your interconnect cable is serviceable..

 

[bennybee]

The interconnect cable seems fine. It's a special RCA/4pin affair for the Quad 303 input.
As for the choice of a power amp, the M2, M4 and later M-type Yamaha power amps are all too big and heavy. This C2 goes into a small third system in the veranda. The Yamaha M35 looks slim and with more or less matching design, but it has those STK power modules and therefor perhaps not in the same league as the C2...