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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
fiftyfifty OP
12 posts
 
Thank you all for responding. 

I would like to repeat there is no hum physically coming from the amp. It is coming through the speakers because of the amp. Please don't ask me to switch power source, preamps, etc. I've tried all this, even moved the amp to the dealer's store and other geographical locations. I  can very confidently state that the source of the hum is the amp and nothing else. Now whether it is a ground loop or a DC offset issue - that I do not know. But i do know that it is a design issue with the amp, for which Cary has a fix and they have fixed it in their newer version. Cary is not asking me to ship the amp back to them. They want to ship the harness/cable to me and they want me to pay for the cable. Alternatively, they want me to trade in my unit for the newer version. Considering that it is a design issue, I believe it is unfair and unethical that I should be asked to pay for them to fix a design issue. What is your opinion on this???

As for the hum, I guess I can identify an electronics expert who can fix it.

Cheers!
jea48
4,323 posts
 
But i do know that it is a design issue with the amp, for which Cary has a fix and they have fixed it in their newer version. Cary is not asking me to ship the amp back to them. They want to ship the harness/cable to me and they want me to pay for the cable.

Cary should send the harness/cable to you free of charge. PERIOD!
The problem is a design flaw, which according to you, they admit.
Stupid move on Cary's part. You should try going higher up in the Cary company chain of command.


thecarpathian
4,185 posts
 
Thank you for the clarification. It is indeed unfair that you should be asked to pay for a repair if it is indeed a design flaw. That being said, I don't believe t is either a ground loop or dc offset issue. Dc offset issue would cause the transformer to hum, which you do not have. From my understanding,if you have an amp with a powerful toroidal transformer attached to high sensitivity speakers, you can hear a very soft hum coming from the woofer and can only be heard with your ear very close to the speaker. Some consider this harmless, and say it has no affect on sound quality.
fiftyfifty OP
12 posts
 
if you have an amp with a powerful toroidal transformer attached to high sensitivity speakers, you can hear a very soft hum coming from the woofer and can only be heard with your ear very close to the speaker.
Thanks jea48 and thecarpathian! The hum is audible from the listening position. But it cannot be heard when the music starts to play. 
bdp24's avatar
bdp24
9,510 posts
 
I know what I would do: send the amp to Cary to fix, when it is received back sell it, and never again buy a Cary product. There are plenty of other amps and amp companies out there, no need to settle for a poorly designed one from a company treating the owner of one of it's shoddy products with such disrespect, if not outright contempt.
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