The Reference 6SN7 Thread

[mordy]

Rounding up, I have approximately an infinite number of RCA 12sn7gta tubes and have never had this kind of sound with them. Mind you, I may have never tried them with these particular output tubes and these particular preamp tubes. Another thing for me to try. First I need to try to document what I have and see what, if any differences there are between these tubes.

And yeah, audiophile tales have worn thin with me too.

I have this theory about unscrupulous sellers:
Most people don't have the interest and knowledge to differentiate between different tubes - within a given category they all look pretty much the same to an untrained eye. So if you can find something that easily identifies a certain tube so that even a less experienced person can identify it, you can use this to jack up the price.
Here are some examples:
Pinched waist - this is something you can see, although I have seen tubes advertised with pinched waist that look the same as everything else.
Bad Boy - let's face it, who wouldn't want to have a Bad Boy tube? Brilliant marketing that covers almost anything...
It is a know fact that the curved base GEC 1834A sounds much better than the regular base 1834A - so you can charge much more for it.
Everybody knows that a gray glass tube sounds much better than than clear glass version of the same tube.
And black glass is even better than gray glass, especially if the black stuff only covers part of the tube.
All metal base tubes are better than black base tubes.
The story goes about a seller that had a large quantity red base tubes that didn't move off the shelves. But once people were made aware of the red base color and the specialness of this tube, it started to sell and the price - you can figure it out.
Brown base is very desirable.
The stronger the tube glow, the better the tube sounds.
And here is a tip for the lurker sellers trolling Head-Fi - I just discovered a tube with bulging glass. Imagine what this means!

 

[NicRhodes]

The 12SX7GT is certainly different to the 12SN7GT. For me it is one of the lowest distortion tubes of this era and as such does not add much character of it's own. A bit like the 76 in that regard. It is probably why some don't like it.

 

[TLO]

I have this theory about unscrupulous sellers:
Most people don't have the interest and knowledge to differentiate between different tubes - within a given category they all look pretty much the same to an untrained eye. So if you can find something that easily identifies a certain tube so that even a less experienced person can identify it, you can use this to jack up the price.
Here are some examples:
Pinched waist - this is something you can see, although I have seen tubes advertised with pinched waist that look the same as everything else.
Bad Boy - let's face it, who wouldn't want to have a Bad Boy tube? Brilliant marketing that covers almost anything...
It is a know fact that the curved base GEC 1834A sounds much better than the regular base 1834A - so you can charge much more for it.
Everybody knows that a gray glass tube sounds much better than than clear glass version of the same tube.
And black glass is even better than gray glass, especially if the black stuff only covers part of the tube.
All metal base tubes are better than black base tubes.
The story goes about a seller that had a large quantity red base tubes that didn't move off the shelves. But once people were made aware of the red base color and the specialness of this tube, it started to sell and the price - you can figure it out.
Brown base is very desirable.
The stronger the tube glow, the better the tube sounds.
And here is a tip for the lurker sellers trolling Head-Fi - I just discovered a tube with bulging glass. Imagine what this means!

Add to the list...
ST sounds better than GT, and GT sounds better than miniature....lastly, Globe is the king...lol

 

[Galapac]

I have this theory about unscrupulous sellers:
Most people don't have the interest and knowledge to differentiate between different tubes - within a given category they all look pretty much the same to an untrained eye. So if you can find something that easily identifies a certain tube so that even a less experienced person can identify it, you can use this to jack up the price.
Here are some examples:
Pinched waist - this is something you can see, although I have seen tubes advertised with pinched waist that look the same as everything else.
Bad Boy - let's face it, who wouldn't want to have a Bad Boy tube? Brilliant marketing that covers almost anything...
It is a know fact that the curved base GEC 1834A sounds much better than the regular base 1834A - so you can charge much more for it.
Everybody knows that a gray glass tube sounds much better than than clear glass version of the same tube.
And black glass is even better than gray glass, especially if the black stuff only covers part of the tube.
All metal base tubes are better than black base tubes.
The story goes about a seller that had a large quantity red base tubes that didn't move off the shelves. But once people were made aware of the red base color and the specialness of this tube, it started to sell and the price - you can figure it out.
Brown base is very desirable.
The stronger the tube glow, the better the tube sounds.
And here is a tip for the lurker sellers trolling Head-Fi - I just discovered a tube with bulging glass. Imagine what this means!

This is awesome! You are so spot on. Like many when I started my journey in tube buying/rolling many of what you mentioned were the Buzzwords people hyped up. Over time you learn and with some, at a cost. Great write up, made me actually laugh out loud!

 

[Paladin79]

This is awesome! You are so spot on. Like many when I started my journey in tube buying/rolling many of what you mentioned were the Buzzwords people hyped up. Over time you learn and with some, at a cost. Great write up, made me actually laugh out loud!

I named one pair of single triode Sylvania tubes “naughty girls” cause they had the same characteristics as Bad Boys.

 

[Slade01]

I named one pair of single triode Sylvania tubes “naughty girls” cause they had the same characteristics as Bad Boys.

Don't forget @bcowen 's famous "Frankentube" 7N7!

 

[Paladin79]

Don't forget @bcowen 's famous "Frankentube" 7N7!

I own several and even included one in some blind tests.

 

[g0ldl10n]

The 12SX7GT is certainly different to the 12SN7GT. For me it is one of the lowest distortion tubes of this era and as such does not add much character of it's own. A bit like the 76 in that regard. It is probably why some don't like it.

If you look at the 12SX7 and 12SN7 datasheets, and the average plate characteristics and its curves, it does seem this tube was designed for use in low plate voltage applications.. as the curves given specifically focus on very low plate voltage relative to the 12SN7 datasheets.. also, the datasheet does give rating for when plate voltage is only at 26.5V

12SX7GT

These curves are obviously focused on plate voltage below 50V, and the relative grid voltage

Now, if we look at the 12SN7 datasheet, we see no reference to this very low plate voltage and the specs to go along with it.. however, the rating for when the plate voltages are higher are basically the same.. so, the question is, was a new tube actually engineered/designed to operate at the low plate voltages, while keeping its ability to run the same exact way as a 12SN7 at the higher plate voltages? Or, did tube manufactures realize that it could operate at the lower plate voltages, and likely some govt application was needing a tube to do that, and they just started stamping 12SX7 on the tubes, and calling it a newly designed tube? Idk

But, the datasheets are a bit different and what the focus is on, especially in the average plate characteristic curves given

So, idk.. just some info

I don't have any 12SX7 tubes to even try, tbh, I think this is the first I have heard of them, lol

 

[mordy]

This is awesome! You are so spot on. Like many when I started my journey in tube buying/rolling many of what you mentioned were the Buzzwords people hyped up. Over time you learn and with some, at a cost. Great write up, made me actually laugh out loud!

Thanks

 

[Isaacc7]

I can’t find my GE 12sx7 right now but I took a few pictures of the RCA tubes I have.

Don’t tell the audiophile police but my other RCA 12sx7 has grey glass and I’m running them at the same time!

Here’s one of my many RCA 12sn7GTA tubes that I have.

There are a lot of similarities there… I’ll pop them in tonight and listen over the next several days. If I’m lucky the GTA will sound just like the sx7 and save me from buying more tubes lol.

 

[triod750]

and save me from buying more tubes lol.

Good luck with that!!

 

[Galapac]

I can’t find my GE 12sx7 right now but I took a few pictures of the RCA tubes I have.



Don’t tell the audiophile police but my other RCA 12sx7 has grey glass and I’m running them at the same time!

Here’s one of my many RCA 12sn7GTA tubes that I have.



There are a lot of similarities there… I’ll pop them in tonight and listen over the next several days. If I’m lucky the GTA will sound just like the sx7 and save me from buying more tubes lol.

Oh I see, your 12XS7 has copper support rods wheras your 12SN7GTA does not.
Yes they do look strikingly similar.

 

[g0ldl10n]

@OctavianH hey, you have that nice amp that allows you test what tubes will require for specific plate voltages and operating points, right?

If you have these two types of tubes, are there any sort of comparisons you could do with your amp to see if there are actually differences at least electronically speaking between these two?

 

[Isaacc7]

Oh I see, your 12XS7 has copper support rods wheras your 12SN7GTA does not.
Yes they do look strikingly similar.

In theory the heater wire should be different. Of course in theory that shouldn’t change the sound at all either

 

[OctavianH]

@OctavianH hey, you have that nice amp that allows you test what tubes will require for specific plate voltages and operating points, right?

If you have these two types of tubes, are there any sort of comparisons you could do with your amp to see if there are actually differences at least electronically speaking between these two?

My amp has only 6.3V heaters and input stage operating point is fixed to 180V/4mA. It's true that I have variable manual grid bias and I can bias almost anything in range of 0-13V if it can be biased in that range for 180V/4mA. These seem to be 12.6V tubes and I do not have them.