My Cary amp - the story of a hum and a bug


Hi,
I have had a problem with my Cary SA200.2 power amp from the time i bought it 3 years ago. There's a hum from both speakers (doesn't increase when the volume is turned up). The hum is there irrespective of the connected preamp or power source and even if i take the amp to another city or location. I was told by the dealer that such a mild hum is normal in such a powerful amp. It was only later that I realized that a solid state amp with a toroidal transformer, however powerful, should not have any audible hum. By then, it was out of warranty.

With the help of the India dealer, I wrote to Cary in the US. From their delayed and intermittent responses, it appears that the hum is a known issue, inherent in the design of the amp, that needs a 'fix', which is taken care of in the newer model of the amp. The 'fix' consists of a cable with caps and a bridge rectifier. Shockingly, they expect that I should pay around $210 + duties for this. To me, it is not a question of money, but one of principle! Why should I pay for them to fix a bug, even if the amp is out of warranty? I even suggested that it will not cost me more than $30 to build the cable here in India if they can send the diagram and component values for this fix. But Cary is adamant that I either pay for the cable or trade in my amp for a new +1 model!! In desperation, I requested that they send me the service manual of the amp, hoping to address the bug with the help of the manual. Back comes the reply that it is proprietary and that they cannot share it with customers. The dealer has been unable to exert any real pressure on Cary to resolve this issue.

I would like to know, from fellow FMs:
1. Is Cary justified in it's stand?
2. Role of local distributors/dealers?
3. Does any other FM own a Cary SA 200.2 and how he has fixed this issue.
4. Can the electronic experts suggest the specs to filter out the hum?
5. Will adding this filter adversely affect the sound quality?

CUT TO CHINA:
I have a Chinese made integrated amp (Kinki Studio). It is no slouch, having been awarded the Blue Moon award by none other than Srajen of 6moons. I blew the amp some time ago by an incorrect connection. It was my fault. But within minutes of sending an email, the dealer in Singapore was on whatsapp chatting with me, asking for photographs, communicating with the manufacturer, suggesting diagnostic checks. Within 24 hours, they realized it could not be fixed via distance communication with a non-electronics-trained user like me. Within a week, a pair of new power amp boards arrived by DHL, shipped at the dealer's cost, with detailed instructions on how to replace the boards. The only cost I incurred was the cost of shipping the old boards back to them for diagnosis. So I guess Xi Jinping wins this round :) 

Thanks for reading
fiftyfifty

Showing 1 response by skiroe

It is a design issue flaw. Potentially in the power supply. A well designed S/S amp should have no hum either from the amp itself or at the speakers. I have experienced both. My bugaboo is usually when the amp itself has some hum. This can be because of not using a power transformer that is over spec’ed for the needs of the amp. In way older amps or even tuners or other equipment using the older type trannies the plates can vibrate because of the potting material no longer in good condition. I have a Sony 80’s tuner that is for sale that has been restored. It had hum which is a bit unusual for a tuner. Granted , this was not hum at the speaker. I certainly empathize with you on the type of hum you are dealing with. The transformer was re-potted which eliminated the hum. In your case as I mentioned this is a design flaw in the power supply creating a hum that exhibits at the speaker. My Pass amp which operates in class A which  could as well be a set up for having hum either at the speaker or at the amp itself and it has neither and runs dead quiet. This is a well designed amp.. period. If Cary was a stand up company they would at the least cover the repair and pay for at least half of the shipping although it would seem that footing the entire bill would be the responsible thing to do as this is not a fault in your system but in their design of the amp.