Soft pins on preamp tubes?

[Little Pigbacon]

Has anyone noticed preamp tubes with soft pins that are easily bent? I have some Groove Tubes 12AX7-C that I put in V3 and V4 of my Marshall JVM, and the pins are prone to getting bent on insertion.

On this amp, the small-signal tubes go in through rubber grommets that line the holes in the top of the chassis. Since you can't put the grommets in with the tubes in place, you have put the tubes in with the grommets in place, so you can't see the pins or the tube socket while you're doing it. This whole process, with soft pins, is a bad combination.

These Groove Tubes are Chinese. I destroyed the first one I bought, because one of the pins folded completely up against the bottom of the tube. None of my Electro-Harmonix 12AX7's had this problem, and neither did the Tung-Sols.

Has anyone else noticed a problem with soft pins on preamp tubes?

 

[ehdwuld]

Re: Soft pins on preamp tubes?

can you flip the amp on its head
install tubes then back up?

 

[Little Pigbacon]

Re: Soft pins on preamp tubes?

can you flip the amp on its head
install tubes then back up?

I've already got the chassis pulled with the tubes pointing up. The problem is that I'm trying to install the tube into a socket that's recessed down in a form-fitting hole in the chassis. It's a blind operation; you can line up the pins with the socket up to a point, but after that you have to go by feel.

View attachment 82915

 

[crusty philtrum]

Re: Soft pins on preamp tubes?

Are the actual sockets mounted to a PCB ?

If yes, get rid of the amp. I've had the glass envelope of an EL84 come apart in my fingers as I tried to remove it from a stubborn socket, and I was extremely lucky that my fingers weren't seriously sliced open.

Valves should have their sockets mounted to the chasis. PCB-mounted sockets are a world of potential trouble (not to mention an indicator of sub-standard, cheap manufacture).

 

[SlyFoxx]

Re: Soft pins on preamp tubes?

First off I'd get my needle nose pliers and straighten all the pins. If those rubbers are causing you trouble I'd just take 'em out an put 'em in a zip-loc bag and label them so you don't forget what they are for. I've never seen any necessity for them or pre-amp tube covers for that matter. If you amp is getting tossed around so as to need the rubbers the amp needs to be treated better and if tubes are falling out of their sockets under normal use and transport that's a problem with the sockets.

 

[Little Pigbacon]

Re: Soft pins on preamp tubes?

Are the actual sockets mounted to a PCB ?

If yes, get rid of the amp. I've had the glass envelope of an EL84 come apart in my fingers as I tried to remove it from a stubborn socket, and I was extremely lucky that my fingers weren't seriously sliced open.

Valves should have their sockets mounted to the chasis. PCB-mounted sockets are a world of potential trouble (not to mention an indicator of sub-standard, cheap manufacture).

Couldn't an envelope come apart in a chassis-mounted tube socket?

The other thing is this: I love how this amp sounds. Even at micro-volume, sitting on the floor in front of it, running into a couple of Mesa V30's, it sounds unbelievable. Sooo worth the money.

 

[Little Pigbacon]

Re: Soft pins on preamp tubes?

First off I'd get my needle nose pliers and straighten all the pins. If those rubbers are causing you trouble I'd just take 'em out an put 'em in a zip-loc bag and label them so you don't forget what they are for. I've never seen any necessity for them or pre-amp tube covers for that matter. If you amp is getting tossed around so as to need the rubbers the amp needs to be treated better and if tubes are falling out of their sockets under normal use and transport that's a problem with the sockets.

I picked up one of these a while back. It helps immensely. I might still take those rubber grommets out. The amp doesn't travel, unless you count rolling around on casters in my bedroom.

View attachment 82935

 

[Little Pigbacon]

Re: Soft pins on preamp tubes?

Anybody else on soft pins?

 

[Chris Pile]

Re: Soft pins on preamp tubes?

Just my guess..... you've been handling them wrong.

 

[Gtrjunior]

Re: Soft pins on preamp tubes?

When I had a JVM I took those rubber grommets out. More trouble than they are worth.
I've bent pins before too but I don't think I'd say that the pins were soft...I think that I may not have had them lined up perfectly.
But like you said, with the grommets in place you're going at it blind. In a typical socket without the grommet you can gently rotate the tube until you feel the pins line up....you're not able to do that with the grommet in place.

 

[Little Pigbacon]

Re: Soft pins on preamp tubes?

Exactly. The friction from the grommet dampens your feel so that you can't tell by touch what's going on. It's easy to crush a pin on one of these GT-12AX7-C without even feeling it. Contrast that with the EHX and Tung-Sols; if you get one or more pins out of alignment, they will deflect slightly and go in the holes instead of folding up.

 

[Little Pigbacon]

Re: Soft pins on preamp tubes?

Just my guess..... you've been handling them wrong.

How do you explain the difference between the these Groove Tubes and other tubes? Why am I not bending pins on EHX and Tung-Sol?

 

[Rex_Rocker]

Re: Soft pins on preamp tubes?

No, yeah, I agree. I feel them Shuguang C9's have more flimsy pins compared to JJ's or Russian preamp tubes. They still sound nice, though.

 

[Darg1911]

Re: Soft pins on preamp tubes?

Some of the Chinese preamp tubes do definitely have whimpy pins. I have some China made Bugera labeled tubes that aren't terribly bad in terms of the pins. But I also have some non labeled Chinese tubes that you really have to be careful with. They are probably the same tubes that get tested and labeled by some of the amp manufacturers or GT.

 

[Little Pigbacon]

Re: Soft pins on preamp tubes?

According to The Tube Store, these are Shuguang 12AX7-A.

http://www.thetubestore.com/Tubes/Groove-Tubes

http://www.thetubestore.com/Tubes/Shuguang-12AX7-A

 

[Gtrjunior]

Soft pins on preamp tubes?

If I were you I'd remove the grommets. They are only the equivalent of tube dampers. If you find that you hear some tube rattle (I seriously doubt that you will) you can always get a set of tube dampers that roll over the tube itself and isn't built into the amps chassis.
Fwiw, I've never experienced tube rattle from a preamp tube, only power tubes. Ymmv

 

[Little Pigbacon]

Re: Soft pins on preamp tubes?

I bought a bunch of dampers a while back. No reason needed.

 

[Mincer]

Re: Soft pins on preamp tubes?

My Mesa preamp tubes have easily bendable pins. They are held in place by a retainer tray, but I have to be careful when putting them in.

 

[Rex_Rocker]

Re: Soft pins on preamp tubes?

According to The Tube Store, these are Shuguang 12AX7-A.

http://www.thetubestore.com/Tubes/Groove-Tubes

http://www.thetubestore.com/Tubes/Shuguang-12AX7-A

Yep. So are Ruby C5's, a few TAD's, Penta Labs, and ARS's. The infamous Shuguang 9th generation.

They are good-sounding tubes, IMO.

 

[Hank-]

Re: Soft pins on preamp tubes?

Well the New Sensor(EHX) preamp tubes have bigger glass diameter than JJ or chinese stuff like TADs. In my case I don't have those rubber things but aluminum things mounted on chassis with covers that have a spring inside them. The problem for me is that the Ehx(& rest NS stuff) have to be pushed hard which usually ends up causing a particular pin to bend on all of these, also the worst part is when pulling them out. The JJ's and Chinese made ones in contrast are a looser fit & I guess benefit from the metal cap things. I also had read as these two being accurate with the NOS stuff glass dimensions somewhat but not the ehx stuff.

In your case the Chinese tubes should feel easier to rotate & feel the slots for the pins compared to the others you have.