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Hello, all. I've got a PrimaLuna ProLogue 2, and a couple of months ago I picked up a pair of the Phillips Holland Pope 12AX7s and a pair of the 1956 French Military Radiotechnique 12AU7s from Upscale.They're all fantastic tubes, but the problem is that they don't seem like they fit in the sockets very well on the PrimaLuna. All four of the tubes seem to sit very loosely in the sockets, so much so that I occasionally get hissing sounds from one channel or the other. I can "fix" this hissing (kind of like a low-grade pink noise) by gently moving one or another of the tubes within the socket, but moving the tubes creates a kind of loud crackling noise which disturbs me. But by moving the tubes within the socket slightly, I get rid of the hiss.
I didn't have this problem with the stock tubes that came with the amp. It seems like the pins just aren't sitting in the sockets very well, which kind of makes it seems like the pins are dirty or they're not all touching the socket contacts like they should. Any thoughts?
Thanks.
Follow Ups:
What about the effectiveness of contact enhancers--i.e., Mapleshade and Walker Audio? Seems like an application to the tube pens and/or tube sockets my be beneficial.
Don't use silver paste contact enhancer, especially where high voltages are present!
The silver paste is a good concept, but I'm sure some people are going to have problems with it.
Another thing to worry about when buying used.
Caig De-Oxit/Pro-Gold is safe for use on tube pins and sockets but most other stuff I have seen used does not stand up to the heat or will promote carbon tracking and arcing of the socket if the contact enhancer migrates anywhere. Tweek is really bad too.Extremely bad!
Replacing tube socket is a lot of work but may be necessary if the socket is worn out.
I like the ceramic/gold ones Antique Electronic Supply stocks. Good quality and they hold up to tube rolling well.
--
Al G
Born To Tinker!
.
Even though I didn't realize until now that there was such a thing as "floppy tubes," they do suck. The good news is that I can seat the tubes so they work and, for now, if they don't get moved around, the're allright. I think messign with the sockets or draining the capacitors may be a bit much for me. But at least I know what's going on.Thanks, guys.
I would suspect the tubes have oxidized or dirty pins first. That's something that doesn't get mentioned enough when rolling NOS or used tubes. To make matters worse, you can stick a tube with dirty pins in the socket and contaminate the socket if the gunk transfers.Having said that, I've had small signal tube sockets that just don't seem to grip the pins very well and require a little wiggling...even with clean tubes. It just so happens that the Cayin that I used to have required it and the tube was quite loose in the socket. Cayin and Primaluna are made in the same factory, btw.
Hi,I would venture to say that the stock current production tubes have marginally greater diameter pins than the NOS tubes. This has loosened the sockets for your tube rolling. Additionally, I find that the chinese tube sockets are nowhere near as good as good old american micanol sockets for spring tension.
With the unit unplugged and capacitors discharged (if you don't know how to do this...don't) use a dental pick to gently pry the receiving pins of the sockets tighter. Problem solved. If you go back to current production USSR tubes plan on doing this again if you tube roll.
Good luck
Not everyone has a set of Dental tools (I do, came in an antique porcelin topped drawer cabinet) so a much more common heavy sewing needle can suffice; if you do not have one of these, chances are the neighbor lady or your Mom or Auntie do. You just need a sturdy tool that will slip into the small space between socket & gripper. Be careful prying against micanol or phenolic sockets so you do not flake off fragments of the socket.
> > .
nt
"David! You can KILL a man with a chopstick!" -Keith Charles, Six Feet Under
Prying the metal collars/contacts inside the socket holes is NOT a good idea unless you know more about the sockets. Some of them are really cheaply made and the copper is thin or brittle. It breaks. Then you are really up s-it creek without a paddle and skip the next para.I have been through the mill with floppy tubes. The first cheap things to do are: clean the pins, bend the pins a bit for a tighter fit (also dangerous), stuff socket holes with tiny pieces of alum. foil. (Be sure to put tape over the center hole if there is one).
The best and most expensive thing to do: get a good technician to replace the sockets with better ones that have smaller, springier, collars/contacts.
Floppy tubes suck, man.
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