I've used the Unison Research Unico Pre and DM as my main amps for a long time. I've had mosfets blow a couple of times in the past due to my error, but otherwise they've been very reliable. However a while back I changed some fuses incorrectly and this caused some issues which it took me a while to track down. S-Man on PFM was very helpful in finding a fuse issue, but it recurred. Then I had Armstrong Audio look at it and they seemed to have sorted the problem.
I've now got a slightly different problem. The power amp sometimes emits a high pitched whine on the right channel (the tone seems to be around 1.2Khz). It's odd that it only seems to happen at certain times, and it seems to be related to the protection circuits of the amps.
Both pre and power have a soft start mechanism for the valve input stage, and they also go back into standby automatically after about 10 minutes.
The problem seems to occur when the power amp has done its automatic switch off and I then turn it on again. Usually when the preamp is still on.
I described this to Twaleb at Armstrong Audio and he has suggested bringing it in for tests. But I'm hesitant about the cost, and thinking, should the money be put towards a more general service?
This leads to the question of when and whether servicing is necessary for an amp. The capacitors all look like they're in good shape, but should I have the amp fully tested and measured to check? I've had it about 10 years and Duvet had it before me for a few years, so it's far from new but far from old. I've had much older amps that didn't need servicing.
I could send it to Henley (the distributor), but having spoken to them they clearly don't know the model well and would inevitably send it to Italy. I suppose that would be the best option, but no doubt expensive.
I'd appreciate any thoughts or suggestions, either about repairing or servicing.
I've now got a slightly different problem. The power amp sometimes emits a high pitched whine on the right channel (the tone seems to be around 1.2Khz). It's odd that it only seems to happen at certain times, and it seems to be related to the protection circuits of the amps.
Both pre and power have a soft start mechanism for the valve input stage, and they also go back into standby automatically after about 10 minutes.
The problem seems to occur when the power amp has done its automatic switch off and I then turn it on again. Usually when the preamp is still on.
I described this to Twaleb at Armstrong Audio and he has suggested bringing it in for tests. But I'm hesitant about the cost, and thinking, should the money be put towards a more general service?
This leads to the question of when and whether servicing is necessary for an amp. The capacitors all look like they're in good shape, but should I have the amp fully tested and measured to check? I've had it about 10 years and Duvet had it before me for a few years, so it's far from new but far from old. I've had much older amps that didn't need servicing.
I could send it to Henley (the distributor), but having spoken to them they clearly don't know the model well and would inevitably send it to Italy. I suppose that would be the best option, but no doubt expensive.
I'd appreciate any thoughts or suggestions, either about repairing or servicing.