Noise in one channel - BHK preamp - tube rolling tribulations


#21

Hi!
I have had almost exactly the same problem with my BHK Pre…
After turning it on for the first time, I heard a strong “tube like” buzzing noise via headphones in the right channel. Left channel OK, and dead silent. When listening via speakers, the noise was not more or less prominent compared to the left channel. Suddenly one day when changing music, I heard a tone in the right speaker (like a 500 to 1 kHz sine wave). When turning the volume down to 1, The tone was still there, and I suspect some kind of self resonance in the tube. I talked to the vendor, and he ordered a new set of tubes right away. After changing to new (stock) tubes, there is still a faint buzzing noise in the right channel via headphones, that starts over 4 in volume, and goes away at certain levels of gain. Well anyway, just two days ago when firing the PRE up, I heard a strong noise in the right channel (tube rush?), both in Headphones and in the speaker. I have now changed the right channel tube back to the old left tube, and the noise is gone… I’m starting to worry that the PRE may be faulty, and are eating right channel tubes?

Please advice…


#22

This morning my right channel began doing what you all have described. Pulsing rush of increased background noise. I’ve swapped tubes left for right (524 hours on them), and swapped for a new set. Problem remains with right channel.

Bought new in March 2018, signed by Bascom, about 1100 faultless hours.

I’ve contacted support.


#23

I love the sound of the Brimar CV4003 (12AU7) in my BHK pre, but two sets turning milky white tops pretty quickly, am I alone in short life of these tubes? No such issue with any others i.e., Amperex 7308 or The Tungsrams.


#24

I use these off and on in the 4003/3987 long plate variant (non BHK pre) and have no problems like you say. They are fantastic tubes…


#25

You’re right, Mark, they are fantastic. Sonically, I think they do everything right.
Perhaps I got two pair from the same sick batch… Maybe I can get Uncle Kevvy to cut me a break.


#26

I tried a pair of Amperex 6922 tubes in the pre, and they went “tube rush” noisy in about 3 weeks’ use of my system. That sure seems awfully fast. I have been using Amperex 7308’s for well over a year before that, and they are still fine. (Just wanted to see if I liked the slightly warmer sound of the 6922, but the 7308’s are just spot on in my system, it seems.


#27

Yes, I’m using the same 7308’s and I can’t find a single thing I don’t like about them.


#28

Hi, new hear and don’t want to ruffle any feathers, but I suggest as strongly as possible to take that deoxit and throw it away. I used it once; yes it seemed to clean the tube pins and sockets, it also left a film on the tube pins and sockets. Then I started having the exact same issues you describe. I searched for 99% alcohol to clean the pins and sockets, which is hard to find where I live, CVS doesn’t sell it, but I did find it. A little almost pure alcohol, Q-tips and some round tooth picks cleaned my pins and sockets and the issues you describe disappeared and have not returned. I did the same as you, went through a lot of tubes before realizing the tube pins and sockets were simply dirty.


#29

DeoxIT is supposed to leave a protective film which prevents corrosion and enhances conductivity. But it does not do well with heat over time. As I recall, CAIG (the manufacturer) has a high temperature product good for tube pins.

Using a cleaner and finishing off with a wiping of anhydrous alcohol is an excellent option.


#30

99.9% anhydrous isopropyl is available on Amazon, saves calling or running around town to find it.


#31

Which problem did you experience? Noise in one channel or the tubes going milky white?


#32

You are correct. Deoxit does clean and it leaves a film / residue . But the residue becomes sticky when hot which is not good. I clean tube pins with Anhydrous Ethanol. I have a contact who works in the lab at my old university. I keep it safely locked away. Pretty lethal stuff if ingested, more than likely lead to blindness or even worse depending on ones thirst :: Without using any cleaner just the action of removing and installing the tubes a few times will clean the pins, but then again this is also dependant on or factors, like humidity, dust, etc.


#33

Hi Brett,

I experienced rushing and spitting sounds; not sure what you mean by milky. I’ve had the sound turn off, then back on while listening, then the channel just turn off completely. I’ve had the sound become unusually euphonic, all of these in one channel.

I had used deoxit because as someone said, “it is made to clean tubes and sockets”, which is true. And it does leave a residue meant to prevent oxidation. That residue film also caused problems for me. Back in the 80’s there was product sold to enhance RCA contacts; it cleaned and left a film “enhancing and sealing the connection”. It was a BS product.

The trick to signal transfer which happens when an conductor is pressed into a socket is the wiping action and the method of applying contact pressure. Modern day connectors follow the same design method of contact as tube sockets.

I prefer gold plated pins and gold plated tube sockets. Corrosion never occurs. The tube sockets do get dust on them and need to be cleaned. A simple small round toothpick and 99% alcohol will do the job and evaporate completely, leaving a clean contact surface.

Sorry to be so wordy. I recently retired and guess I need something to do. I enjoy this forum, the daily post and videos.

Michael


#34

Thanks, RonP posted just above your post that some of his tubes had gone milky white, hence my question for you.


#35

The “getter” is the grayish coating at the top or sides of the tube. If you get air infiltration, i.e. from a crack near a pin, the getter will turn milky white.