Hello everyone,
I'm the owner of a CSP2+ since about two months. First, let me say that it sounds terriffic - I primarily use it as a headphone amp, and I have yet to hear one that sounds more life-like than the CSP2+. Unfortunately, I have several issues that bother me... let me start from the beginning:
- When I received the amp, I immediately noticed some background humming. I do realise that a tube amp will never have a perfectly silent background, but with the CSP2+ it was clearly audible even when listening to music (in more quiet passages, anyway). I would call it baely acceptable, and was about to return the amp - but then decied against it, and hoped that the humming would get better with different tubes.
Since then, I have purchased several new sets of tubes for the CSP2+. While the humming issue actually did get better with some of them, there were additional problems...:
- I first tried some NOS Sylvania 6922. I tried every tube separately - keeping the stock 6N1P in the two other positions - and observed with a shock that the tube started arcing after about 10-20 seconds. After removing the faulty tube, I tried the amp with the stock tubes, and luckily everything sounded alright. I then tried the other Sylvanias, first in front, then in the rear position - both started arcing like the first one.
- Next, I tried some Amperex Bugle Boy 6922's. These did not arc (phew!), but presented other problems. I had two pairs: the first was extremely microphonic, the second pair exhibited a weird sort of hissing noise, which from time to time would grow louder and then turn into a faint crackling noise. Note that this appeared when I tried the tube in the front position.
- I then tried some new production ECC88's. This time, no crackling or hissing (humming was still there) - but when listening to something, there was an enormous amount of distortion, even on low volumes. This was consistent with all three tubes. Poor quality, I guess...
- Finally, I tried a new production EH 6922 in the front position, and two Amperex 6922's in the rear position. With this combination I've had the best overall result, and that's what I'm using since about three or four weeks. Only one issue was persistent, an occasional, irregular, faint crackling in one channel. This didn't bother me too much, but it was audible if it occured just in the pause between two tracks.
- Today, with the tube combination mentioned above, a new issue appeared out of nowhere: a distinctive hissing in the left channel, which turned eventually into a crackling noise - the same that I had discovered when I tried one Amperex tube in the front position. I was somewhat ennerved and decided just to go back to the stock 6N1P tubes, with which I did not have any problems before. And guess wha - the exact same problem occured with these tubes as well!
I tried most of the combinations listed above with three different rectifiers: The stock one, an RCA 5Y3GT, and a GE 6087 (which is, I think, mostly identical with the 5Y3GT). I did not notice any difference between them, so I think the rectifier is fine.
... well, I'm at my wits end. Does anybody have an idea what is wrong with my amp? Could it be that the arcing Sylvania tubes have damaged the amp, so that my problems are now persistent with all tubes? And further, just how much background humming is normal for this amp?
I'm trying to make sure that the problem lies with the amp, and not the tubes - I'm in Europe, so shipping the amp back to the US for a check-up would be very expensive, especially if it should turn out that nothing is wrong with the amp itself.
Really looking forward to your replies. Thanks!
lastly, I apologise for any grammatical errors - as you surely have noticed, English is not my primary language