2. misc-audio
  3. 190808-147430

Loud buzz with Marantz receiver preout to amp

Hi Team —

I’m trying to connect an amp to my Marantz 4270 via the preouts so I can control volume with the Marantz (the amp, an Ashly CFT-1800, has no volume controls). I’m getting loud buzz that gets louder with every gain dial increase on the amp, and there’s no music coming through from my phono or aux sources.

I can hear FM radio, but have to really crank the Marantz volume to get the FM loud enough over the buzz. Something’s not right. I don’t think it’s a ground loop issue because of the total lack of any phono or aux source audio. The RCA jacks from the Marantz preouts go to the Ashly’s screw terminal inputs (the RCA cable heads were cut off and the 4 wires run to both sides, channel 1 + and -, and channel 2 + and 1. The Ashly has two more screws between those channel inputs dedicated for additional grounds — input and chassis — both of which are empty in this case.

 

The Marantz uses shared jumpers in its preout and front main in jacks that must be removed to plug in an amp — which means the front main in jacks are then empty. The manual indicates that I should connect the main in jacks to the rear pre outs to get sound from front and rear speakers, but I don’t use rear speakers. I tried it though, to see if that made a needed connection that was missing, but it didn’t help. Same buzz. I should also say, the Marantz just came back from my tech, who specifically gave the preouts a clean bill of health, knowing I wanted to set this up.

Any ideas? Thanks very much!

jlcase
toddalin's avatar
toddalin
260 posts
 

Sounds like you have no ground connection between the preamp and amp and maybe should be using using that/those ground terminals.

Also, some interconnect cables are only grounded on one end, not both, and maybe this is the case here. If you have an ohmmeter, be sure that both the ground and hot leads are coming through the cables (i.e., check continuity).

jlcase OP
4 posts
 

Thank you for the response — I sent images to Ashly tech support and they didn’t call out a lack of grounding in the connection, but maybe that’s part of the puzzle. Another odd thing is that my Marantz works with the preamp jack engaged — and audio has to go through the preamp circuit into the main front in that case. That would indicate, as I understand it, that the preamp works. I’ve read of a couple other people trying to connect their Marantz units to external amps and getting no audio output, so I wonder if I’m just missing something — or if this is a common fault of vintage Marantz units… Just weird that the preout works perfectly when connected to its own internal amp.

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