Linlai 6SN7

I am using Linlai 6SN7 in my Supratek Cabernet preamp. I have noticed that the tubes run vey cool to touch even after four hours of use. Is that normal for these tubes? Thanks.

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Preamp tubes don't run that hot, most of the preamps that run tubes really hot go through tubes quickly.  I can touch the tubes in my preamp and they are just warm.

Sounds great? Enough Volume? Low Heat! Terrific.

Doing research, I checked with McIntosh about their vintage tube preamps. They confirmed: originally the preamp and tuner walnut cases had no top vents, even my mx110z tube tuner/preamp with 17 tubes.

They made matching wood cases for amps with top vents. Eventually they simply used the single top vented case for both preamps and amps, kept matters/stock easier.

jasonbourne52 My Psvane and TungSol tube run very hot only the Linlai are cool to the touch.

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invalid. All my tubes run very hot except for Linlai. Could the tubes be an issue? They sound really good though. If anyone running these tubes in Supratek can check and let me know that would be great.

All my tubes run very hot except for Linlai. Could the tubes be an issue?

The Linlai tube has a larger envelope and so has greater surface area to shed heat. Don't worry about it!

atmasphere. Good to hear that. I saw a video from Kevin at Upscale Audio that if tubes run cool then one needs to worry. Naturally I needed to confirm that. I do not know why if tubes run cold we should worry.

The Linlai E 6sn7 are the coolest tubes I own. Thank you @atmasphere for explaining this.  

I posted basically what Ralph noted, but it didn't take.

In addition I mentioned that if the Psvane 6SN7's also have large ST shapes bottles, but also feel hotter, they may have thicker glass.

Guessing that thicker glass would be less efficient @ dissipating heat as the added mass would also increase heat storage over hours of usage (like a cast iron pan VS a thin tin/copper pan).

I have/had numerous ST shaped 2A3/300B tubes with varied bottle/glass thickness, but have never monitored how hot they get/got (also never touched them when hot unless by accident).

The worst burn (under forearm) I ever got was from early JJ 2A3's which had very, very thick glass envelopes.

My old 300B amp (power switch on the back) was located on the bottom shelf of my rack, which is squeezed into a hall linen closet, and it's the same with my current Bottlehead 2A3 mono blocks (so burns do happen on occasion).

Curious if the hotter Psvane's have thicker glass.





@dekay, interesting question about glass thickness and heat. I’m  also curious about this. I never really thought about that,until this thread popped up. 

Just checked my Psvane CV181 tubes in front positions (warm) and TJ Full Music 6SN7s (slightly warmer) in rear positions in my Cary SLP-98 preamp. Can hold my fingers on both, neither are "hot" or burn fingers.  Put my tongue on them, no issue there either - just kidding, yak yak 🤪.   Power transformer is separate/external on mine, and not heating up the whole preamp top plate surface area either.  It's going to vary by design with each preamp, transformer locations, and casing, venting too.      

OP, others,

Do you have your own simple tube testers? I cannot imagine owning tube equipment without one.

simple, seller seems to know what he is talking about





I have this one


they make a slightly larger model 257, still very portable

there are a lot of good ones listed now


people say: " this little one agrees with my other testers". that's always been true for mine as well. I've got a big calibrated one around here somewhere, they always agree, I don't bother with it any more.

As a general rule, preamp tubes don’t run anywhere as hot as amplifier output tubes and that’s one big reason they can last 2000-10000 hours. I’m currently running a couple of Amperex 6922 and while I wouldn’t want to be holding one, they’re not so hot as to Immediately blister my fingers.

All the best.