2. amps-preamps
  3. 151693-2183

Crackling and hiss - Preamp tubes not seated right?

I've posted here before about the cracking and hiss I get from my Primaluna Dialogue Premium. It became very noticeable during listening last week, so I took another stab at trying to isolate it.

When the amp is on, but with out anything playing, I can hear a low hiss and an intermittent crackle - the volume knob does not effect it.

It was only happening in the right speaker, when I swap the speakers it stays, so I figure it has the be the amp.

I swapped the three preamp tubes in 1,2 and 3 positions with the tubes in 4,5 and 6 position and it moved to the other speaker, so I assume it's a preamp tube problem.

I swapped out the 6 Mullard CV4003 for the original stock tubes, and it's silent. That felt good to finally get ahead of the problem.

I started to swap back in the Mullards one at a time to see when the 'bad' tube appeared. Swapping into position 1 and 2 were good, but it came back on when I added a tube to position 3, so I went back down to positions 1 and 2, and it was there again! But it was silent before? Very frustrating. I went back to all 6 of the stock tubes and it's silent again.

So my question is this - could it be that the Mullards don't seat as well as the stock tubes, and there is some arcing and other interference getting through? Should I give the pins and sockets a cleaning? Any advice on how to do that? Maybe I need an adapter to go into the socket to seat the Mullards?

I also think this may be the source of some distortion I was hearing, particularly on piano at certain higher frequencies. Does anyone have any thoughts on that?
stephenjess
jperry
2,444 posts
 
You have a bad tube(s) that need to be replaced. If you want high quality NOS tubes contact Andy at Vintage Tube Services.

New production tubes the tube store already referenced is fine.
paulcreed
554 posts
 
I agree with Elizabeth, I've had same issue many times with newly purchased nos tube from very reputable dealers. If you take the tube and lightly tap tube pins on countertop, take tube out of amp tap the tube with a pencil it should clear up problem. If not there are other issues.

jayctoy's avatar
jayctoy
3,959 posts
 
I got the same problem with my quad 300b Gold lion , I bought them last year brand new, I decided to use them Feb 2019, last week I notice my left speaker does have crackling sound, When I replaced them with EH 300 B all back to quiteness, I will try to use all the tricks mention here, and rotate them, I think it will work...
atmasphere's avatar
atmasphere
11,753 posts
 
 Despite what I've read about JJ reliability, I decided to re tube with JJ in my amps and pre and they have been rock solid so far and the tone is perfect in my set up.  
IMO/IME JJs are more reliable than any of the newer Russian made signal tubes.
I swapped the three preamp tubes in 1,2 and 3 positions with the tubes in 4,5 and 6 position and it moved to the other speaker, so I assume it's a preamp tube problem.
@stephenjess  This is a solid indication that one of the three you swapped from left to right is the culprit. The thing is, when a tube is making crackling sounds, often it will be affected by physical handling- tapping on the tube can often make it stop- for a while. So I would swap the tubes one at a time! When the problem moves then you'll know which tube it actually is. Don't be fooled by it shutting up for a while- be patient.

daveyf's avatar
daveyf
2,857 posts
 
Had the exact same problem with a Mullard CV4003 as the OP. The culprit is the tube. These tubes, which sound great...as another member posted, are getting on in years ( if they are NOS, which mine were). As such, i think they are not as ’durable’ as a lot of others. I sourced mine from a very well known tube supplier, yet one tube still had this problem. It is NOT the fault of the gear ( although the tube supplier always tells everyone that my preamp is hard on tubes....yeah right!).

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