Topping pre90 - how to test?

[tonapo]

Hi there,

I sold a Topping pre90 last year which was working perfectly in my experience, I used it with a topping d90 DAC and NAD M23 power amp connected via xlr. Anyway, I changed to a different pre-amp, so I sold the Topping pre on ebay. Unfortunately the buyer got in contact a few days later to say he was experiencing a hissing sound when using the Topping pre90, both with XLR and phono connections. I had not experienced any issues previously but accepted the return of the unit. I then spent a short amount of time trying to recreate the issue. I tried with my desktop set-up with some Adam speakers and using a spare Topping D10 DAC but I could not reproduce any issue with the pre90.

I have not got around to testing any further and the pre90 has sat in my cupboard since last year. Are there any tests a non-technical person could do, to see if there is a fault somewhere with the unit? I might try plugging into a few units around the house, and see I can re-produce the issue. As it is I am not comfortable selling, but it is not being used which is a shame.

Thanks for reading.

 

[RayDunzl]

Maybe rhe buyer just didn't want it.

 

[DVDdoug]

All active analog electronics generate SOME noise. Whether it's audible or not depends on the sensitivity of your speakers (or headphones), the amount of gain and the volume control setting (including the following stages like a power amplifier), how close you are to the speakers, and other noise in the room, etc.

 

[Roland68]

All active analog electronics generate SOME noise. Whether it's audible or not depends on the sensitivity of your speakers (or headphones), the amount of gain and the volume control setting (including the following stages like a power amplifier), how close you are to the speakers, and other noise in the room, etc.

There's probably no problem, so you can't test anything.
- As @RayDunzl said, the buyer might not have wanted it. Unfortunately, blatant lies are enough on eBay to force a return.
- He did indeed have a problem, and it was due to incompatibility between the devices, grounding issues, ground loops, etc. Not a PRE90 problem.
- He already had a hissing noise in his system and thought he could solve it with the PRE90. Not a PRE90 problem either.
- He has some high-efficiency horns, e.g., at 109 dB, which make background noise audible, which otherwise doesn't matter.
If you have absolutely no problems, you can sell the PRE90 with a clear conscience.

Maybe you could just put it up for pickup at a local classifieds site and show it off.

 

[tonapo]

Thanks for the replies.

Yes, my first thought at the time was the buyer just did not want it. I was worried about passing on a potential defective unit though in my use-case it appears not to be. Its annoying. Oh well, I suppose I should try selling again then...