Looking to sell a strangely behaving Cayin HA-1A MK2 tube amp. I purchased this unit from a user on Head-Fi and once I received it, it started exhibiting buzzing and humming. According to the previous owner, there was never any noise while the unit was in his possession. I have tried changing the input (CD -> AUX and vice versa), using different output impedances, using different headphone outputs, using a different power cable, plugging it directly into a wall outlet instead of an outlet extension, adding a ground loop noise isolator between my source and the Cayin, using different combinations of tubes, and moving the unit to different locations in my home. Despite all of this, the unit experiences a hum when it is in my possession. The hum is minimal when the lowest output impedance is selected and strongest at the highest output impedance.

I took the Cayin to a local repairman specializing in guitar tube amplifiers to get some basic troubleshooting. this is what I was told:

There is a 120Hz hum output by both channel outputs. Probing the tube sockets, there is too high of a voltage across the control grid of the tubes which can damage them Finally, the main PCB of the amp has a constant non-zero DC voltage. Resistors that should experience a voltage drop have no voltage drop.

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I sent the Cayin to Fuchs Audio for further diagnosis and potential repair only to be told that there is nothing wrong with it (check the timestamp for proof; will forward the unredacted invoice to any potential buyers). They were unable to replicate any noise, static, hum, or hiss. However, upon getting the amp back and trying it in my home, the noise immediately appeared and is apparent. It is unlistenable to when in my possession and I am hoping to sell it and get some of the money that I spent on it back.

The Cayin HA-1A MK2 is being sold AS IS with no promise of intended functionality. The Cayin amp may sound perfect to you with zero noise. You may have a terrible experience like I had, one that leaves you scratching your head wondering why only you can hear the noise and in awe of the fact that a tube amp and everyone you talk to is gaslighting you into thinking that it is functioning normally. I do not know why it makes static. It may or may not make static noises if you buy it.- I can promise you nothing. Aside from the static, the only things wrong with the Cayin HA-1A MK2 are a burnt-out LED under the right EL84 tube, minor scratches on the top and sides of the case, and a chip in the wood on the top all visible in the timestamp photos.

I have since purchased a Feliks Elise MK2 and use it in the same location as the Cayin. There is 0 hum/hiss/static/noise. It is pitch black like a solid state amp under the same operating conditions, using the same audio stack, same RCA cables, and same power cable plugged into the same power outlet. Hence, I am hoping to let this go and recoup a little bit of the money that I have spent on it.

To summarize:
- Wonky Cayin HA-1A MK2 that may or may not have static. It may decide it likes you and behaves. It may decide it hates you and wants to torment you endlessly. I do not know.
- Purchased originally in 2019; No longer covered by warranty. Any repairs will be at YOUR expense
- Includes the original box and all accessories (manual, spare fuses, power cord, and original vacuum tubes)
- Signs on use through minor scratches on the sides and top surfaces

This wonderful nightmare can be yours for $450 OBO Shipped CONUS. This weighs 26 lbs- I will not ship it outside the CONUS unless YOU pay to ship it. If you decide that you want this for some reason, you can bundle it with all the tubes that I have as well for an extra $200 (4 pairs of matched 12AU7s, 1 pair of matched EL84s, 4 12DT5s). I will take trades for headphones, like Sash Tres headphones, Sennheiser headphones, Grados, Clears, or Raidances (I will add PayPal), IEMs, and matched pairs of high-end 6SN7GT vacuum tubes.

If you have any questions please reach out! Thank you for looking!