Unison Unico SE noise

Sounds like the preamp tube may have gone bad (staticky crackily noise would indicate a tube problem). If you have access to a tester, try testing it. If not, you may want to just replace it and see if that solves the problem.

Marco

Wow, I just got it back from Underwood Hi for mods not to long ago. I know the replace the stock tubes. Think it could be bad already? By the way, their service was great, they really took care of another problem I had with the amp.

I have had brand new tubes be bad right out of their box.

Arthur

Sounds like a bad tube to me, too, especially if the hum is in one channel only. It might just be a tube that needs to be reseated in the socket.

Whatever you do, use a step by step method. Consider swapping tubes from left to right, one pair at a time, and listen for changes.

the low level hum/static is in both speakers.

That doesn't sound like a tube issue to me. Have you tried unplugging all you sources, and re-connecting them one at a time to see if a source might be the cause? I'd try that, but connect only one source, then disconnect it and connect the next source. Once you've gone through them all, then you can start adding a second source. It might be a bad interconnect, ungrounded power cord, etc.

If you find the hum returns when a particular source is connected, then swap the source interconnects and power cord to rull out the wire as the problem.

Dumb question time - where is your ear when you hear this low level noise. In the listening position or at the speaker? If the latter you may just be hearing the noise floor of your amp or, more probably the noise floor of the particular tubes Wally installed.

There are tubes and then there are tubes teted for 'low noise'. A lot of tube electronics need LN tubes to avoid a low level sort of hiss. If you are only hearing this when your ear is next to the speaker, either forget about it or buy some especially low noise tubes.

BTW, do I assume that you listened for, and did not hear, this noise previously?

I tried unhooking all the interconnects. Even with all of them unhooked, the noise is still there.

Okay Newbee, I think you are right. I can't really hear the hum/static from my listening position. I have to get close to the speaker to hear it. I certainly do not hear it when the tv is on or when I am playing music. Thanks for the input so far guys.

Try using a cheater plug on your amp's power cord.

although there is noise from both speakers, it is really bad, loud in the right channel. It is a lot louder then when I first posted about the problem earlier. So I opened up the amp and switched the tubes from one side to the other. Sure enough the heavy static noise moved to the left side so that means it is a bad tube. These are the mullard CU 4003s (12AU7s). I know I need to replace the one tube, but my question is are the mullards a little noisey anyways?

my question is are the mullards a little noisey anyways?
Kclone (Reviews | Threads | Answers)

All tubes can vary in the amount of inherent noise. That's why all good tube sellers test and grade their tubes according to noise. Upscale does this as does Vintage Tube Services.

To specifically answer your question, Mullards are not noisy. They are extremely quiet as a rule. However, as I mentioned, some will be more noisy than others, but we're talking about low levels of hiss...not the type of noise you describe.

Congratulations for troubleshooting the source of the noise.

I have been enjoying my Unico SE ( level two modded by Underwood/ parts connexion with Mullards ) for about a month now and I think it is starting to show its true colours finally !! I have been running it all day for a lot of the time as I heard it could take awhile. I stopped the music and turned up the volume full and was suprised to hear sweet silence with my ear right next to my speaker. I tried this test soon after recieving it and could hear hiss so am very pleased with the improvement !! It handles all my music well but the jazz is pure magic and its probably the jazz that I want to get right! It really is turning into an awesome amp. My CDP is the new Raysonic which is turning out pretty nice too. I think they have a great synergy . Cheers.