6SN7GT VT231 TUBES

I have a pair of Sylvania VT 231. 6SN7GT on my OPPO 105 Modwright and when I open the drawer on the player I can hear the noise of the opening on my speakers

Are these normal??

@zorro

That’s very normal for vintage 6SN7GT in "upstream" slots. That’s why I mentioned I hate these tubes in anything but power amps - where they’re far enough downstream from most of your system’s net gain (gain structure). The problem is:

1. 6SN7 has very LARGE plate structure compared to its moderately high mu / gain
2. Vintage 6SN7GT (and VT-231) are very old, and its large mica spacers are not holding the internal parts as tightly as they should, especially after all these years. Later GTA and GTB variants improve the plate & mica structures for this reason; you might try those though they don’t sound as "sweet" as GT.

And yes, any mechanical switches or motors in the SAME box as a 6SN7 is going to cause audible mechanical feedback. That’s not specific to 6SN7 - I have 6H30 preamps with the same issue (they are very sensitive to this). Tube dampers are worthless for this; don't even bother - the problem is how they are mounted to the sockets and PCB / chassis. 

Anyways, if your Oppo 103 has a digital volume control (I forget if it does or not), and you’re using this to directly drive your amps, your problem is gonna be SO MUCH WORSE. If you had an analog preamp with volume control, then that attenuator is at least able to filter some of the microphonic noise (a downstream attenuator reduces the "net gain" the 6SN7 sees downstream). By contrast, the Oppo’s digital volume occus before the 6SN7, so your tube noise effectively bypasses it.

Frankly, 6SN7 here is a rather sadistic choice on part of the modder.

@acresverde seems as though the Melz tubes have a reputation of having problems. Reading on other forums shows that many of the noise and different failures can be fixed by resoldering the connections inside the pins. I’ve been put off buying them because of the issues people have reported. It would be a shame to throw out expensive tubes if they could be repaired. 

If you want amazing sound but don’t want to spend the big bucks on the really hard to find NOS you have some options. You could use an adapter that allows you to use a pair of 6j5, 6c5, or even 6p5 tubes instead of the 6sn7. The 6sn7 essentially has two 6j5 in one bottle so a pair of 6j5 are exact equivalents of a 6sn7. I really like the Cossor 6c5g, GEC l63, Australian 6j5gt, and the good old metal RCA 6j5.
 

You could also get an adapter that allows you to use 12v versions of the 6sn7. The 12sn7 tubes are exactly the same as the 6sn7 but much less expensive. It’s the only way I could afford the GEC b36, the b65 sells for stupid money these days. Same holds true for the Tung Sol black glass round plate 12sn7. I also use that adapter along with the 6j5 adapter to use 12j5 tubes. Love the Raytheon 12j5wgt, Sylvania round plate 12j5gt, Mullard cv535, and Tung Sol JAN 12j5gt. 
 

The 7n7 tubes mirror the Sylvania 6sn7 tubes for the most part. If there’s a Sylvania 6sn7 you like you can get it for less in a 7n7 with one exception. The original metal base Sylvania 6sn7w is generally considered to be their best but they never made an equivalent 7n7 or even 12sn7. Interestingly, the 14n7, the 12v version of the 7n7 seems to be an exact copy of the metal base 6sn7wgt complete with copper support rod. The 14n7 is one of my most loved tubes and also one of the cheapest in my collection. 
 

There are a few variations of the 7n7 that are worth looking for. Any of the tall bottle ones are good, just like the tall bottle 6sn7. Some say the so-called Frankenstein version sounds better. Its bottle is shaped slightly differently and that’s how you can tell them apart. All of the 7n7 and 14n7 were made by Sylvania with one exception. National Union made round plate 7n7 for a very short period of time. They have a dark tall bottle and you can see the bottom of round plates in the gap between the base and the dark coating. Great sounding tubes, the same as the NU round plates 6f8g as far as I can tell. 

Don’t forget the Shuguang WE6SN7 Plus. This is a fantastic current production tube. I use a pair in my Don Sachs DS2 and they are lovely.

Just thought I would chime in here with my experience. In my system I have a pair of 6SN7s in my preamp and each of my monoblocks uses a 6SN7 in the driver stage.

When I first got my tube preamp it came with late production Russian equivalents - (6H8C? or 6N8P? I don’t remember). They sounded great, but the forums got me obsessed with the old tubes. I read & researched on the various forums and bought a lot of tubes. Yes, there were differences and I eventually settled on a pair of Ken Rad VT 231s as my daily drivers in my preamp. My power amps came with brown base 5692s. When one of those finally failed I replaced them with a pair of coin base Sylvanias that are typically "pooh-poohed" in comparison with the usual, well-respected suspects. They sound fantastic and are probably the quietest 6SN7s in my collection.

Recently I switched the Sylvanias for the Ken-Rads between the power amps and the preamp. They sound superb. I did not expect them to sound so good!

My system has evolved a lot over the last 24 months. And I’ve been able to distinguish the impact of every change, sometimes with grudging acceptance - "this should not make a difference, but I can hear it, and, having heard it, I cannot go back!" It can get expensive!

All this experience has reinforced the "foundational truths" that:

- Everything is system dependent and everyone’s system is different, at least if for not other reason than the fact that our rooms are different. As well as our experience and preferences.

- You can read the various forums and opinions for entertainment value but there is no substitute for personal experimentation and patient, relaxed listening, in your system. Opinions and verdicts about what is best are about as useful as reading a Car and Driver magazine where they test a Ferrari or whatever, but what you need as your daily driver is a Honda Pilot. Or Ford F150 pickup. Entertaining, but, for all practical purposes, irrelevant. At best, such posts can point the way from someone else’s lessons learned in their system, in their room, with their listening preferences.

- We all have our own preferences, largely based on what we're used to.