# Mini Review: Various 6SN7 Tubes



## aerius

Or more accurately, paragraph length impressions of various 6SN7 family tubes, because most of my tubes are 12 & 25V versions of the 6SN7.

 To start from the beginning, back in September last year I built myself a new headphone amp, which proved to be way better than expected, and so started the quest for better 6SN7 tubes.

 First off was the *GE Canada 6SN7GTB* with round side-getter, found it in the local surplus shop. It wasn't a bad match with my K340, the extra zing in the treble was a good thing which balanced out the roll off of my headphones. Unfortuanately it was too harsh & sibilant and proved to be fatiguing. Midrange wasn't bad, it lacking in detail compared and instruments & voices tended to blend together, but it had a warmish tone and didn't offend. The bass however had issues. Bloated and one-note are the words that come to mind, it got out of control down there. Low piano notes had a tendency to sound alike and blur into each other, as did faster bass lines. Not good.

 Next was the *Electro-Harmonix 6SN7*, normal pins. It's a dynamic & fun tube, it can slam the bass and rock you out while giving a taste of tube sound. My main problem with this tube is that it fails to connect me to the music, yes it can do frequency extension & dynamics, but it doesn't do low-level detail & harmonics, and more importantly, no midrange magic. In a nutshell, sounds like the above GE, but with better bass control & quality, smoother treble, and a drier midrange. It ultimately proved to be unsatisfying.

 After that was a pair of *Rogers Canada 12SN7GTA* tubes. They look similar to the Sylvania yellow labels in the gallery linked to adhoc's 6SN7 guide. These things will give you the stereotypical tube sound: warm midrange, soft & somewhat weak bass, and smooth highs. The highs are less extended than the GE, but they're the smoothest and most detailed of the tubes listed so far. I can finally have extended listening sessions with all my albums, even the bright crappily recorded ones. But the highs are too smoothed & rolled off, even though the detail is there, transients suffer as do dynamics to a lesser extent. Cymbal hits are too soft and don't accent the music correctly. Midrange is warm & nice, if a bit distant, no reach out and touch it feeling. Bass, well, see treble. Not enough dynamics and drum hits suffer the same way cymbals do.

 And then I came across the *GE Canada 12SN7GT*A, which looks remarkably like the 1952 Sylvania in adhoc's photo album, but it doesn't sound like one, even though I thought it did at first. This is one of my favourite tubes, it has the best frequency extension on both ends and it's punchy and dynamic as hell throughout the entire frequency range. Great PRaT on this tube, it reminds me of Naim & Grado gear in that it's always pushing the music forward with a lot of drive, awesome for rocking out. 

 Bass is nice & tight, midrange is still a bit on the warm side, but the treble can get a bit sibilant on some material, Tori Amos comes to mind. This tube makes a couple of her albums a bit hard to listen to, her "S" sounds are already a bit on the sharp side and the GE accentuates that and makes them sharper & longer. Also, compared to the RCA's, it's not harmonically complete, and the tone of various instruments don't sound quite right. It's a minor issue though, and doesn't stop me from enjoying this tube.


 Then a chance meeting with an old-timer at the local surplus store led to me getting some tubes to try out. He had thousands of tubes stashed away and was happy enough to give a few pairs to me.


*RCA 12SN7GT* with red labels & single side getter. Warm sound and a nice wide soundstage, but on some music there was a bit of a hole in the middle. Moves everything back a couple rows and doesn't have the dynamics & drive of the GE 12SN7GTA. It's a good match with my Grado 225, but doesn't get along as well with my K340. Doesn't have the drive and can sometimes put me to sleep with the wrong music. Tonally, it's getting better, fuller sounding than all tubes so far, instruments are getting a nice body to them and piano hasn't sounded better. It's a bit more detailed than the above GE in the bass & midrange, but gives up a bit in the treble in exchange for a smoother presentation. Bass isn't as tight nor as dynamic as the GE, but it doesn't get bloated nor indistinct by any means. Quite nice, if only i didn't hear the better stuff.

*Sylvania VT-231*. Umm...where'd the bass go? Way too clean, noticeably better detail than the GE (detail limited by my headphones) and I finally get the treble detail & extension I'm looking for but not nearly enough bass, and this is with a K340 that has as much bass as a PS-1 Pro. The lows sound like an HP-1000 on a solidstate amp, way too tight, lean & dry, I ain't a fan of that sound. Would be great if I had some kind of bass boost on my amp to fatten up the sound. Those of you who are old enough may remember the "Rumble" button on some receivers, it's purpose was to cut the low bass so it doesn't feed back into the turntable & cause _bad things._ It sounded like someone had taken a great tube and hit the Rumble button.

*GE 6SN7GTB* with exposed filament on top. It looks cool and glows in the dark, and I guess that's about the only good thing I can say about it. Might as well use transistor gear because that's pretty much what it sounds like. 

*RCA VT-231* and *1633* with grey glass. This is my favourite tube, it's not neutral, it's not perfect, but damn is it ever sweet. Robert H was right, the tonality on this tube is just killer, it's the tube equivalent of a grand old concert hall. It's not the last work in detail, transparency, extension, and all that stuff, but the tone of the instruments has a warm dense sweetness to it that just pulls you in. No it's not neutral, not anywhere close, but the tone is so good that I just don't care. Takes the big wide soundstage of the side-getter RCA, fills in the hole in the middle, and adds height. I think it does the best portrayal of height of all the tubes, and imaging has the best solidity as well thanks to the tonal density.

 Bass is strong & rich, fuller sounding than the GE 12SN7GTA but not quite as dynamic. Detail and harmonics though is no contest, RCA all the way. You don't just hear the low notes of say, a grand piano, you hear the entire body of the piano and the air around it, and the subtle differences in tone of the various bass notes and how they fill the space. Midrange is the strength of this tube, let's put it this way, I swear to god I've had my ears tongued by all my favourite female singer, it's unreal. Treble is the only weakness, doesn't have as much extension as the GE or Sylvania, but at the same time it sounds just as real if not more so. Cymbals end up with a more brassy than airy tone, but they still sound really nice & solid, and each individual hit has it's own unique sound & character. There's more detail than the GE, not as much as the Sylvania, but between the RCA & Sylvania I'm still having a hard time deciding which I like more in the treble.

*Chinese 6SN7* tubes from a former co-worker's amp since he's not using them, and now I know why he's not using them. It sounds worse than the GE exposed filament GTB. Harsh, grainy, lack of detail, practically no instrument separation, my Sony Discman probably sounds better than this tube. Pure crap.

*Shugang 6N8P* tubes, from the same guy as the above. Take the GE Canada 6SN7GTB. Tighten up the bass, dial back the treble a tad, and lean out the midrange till it hurts. In an attempt to make a non-tubey sounding tube, they sucked all the goodness out of it. As with the exposed filament GTB, might as well go with transistors with how it sounds.


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## Jon L

Yup, RCA VT231 sounds kind of like AKG k340's. The treble is not as open as other 6SN7's, but the tone and density is something to behold. 

 My favorite 6SN7 tubes are all from this "tone and density" school, including National Union grey glass, Kenrad VT231 black glass, and the RCA grey glass. The NU Grey glass, if you can find it, is even more mythically magical. I haven't been able to find any more for a Looong time, though. Black glass, yes, but not grey glass. 

 A little trick to get around the treble extension issue with these Tone Kings is to use something like Walker SST Extreme to the tube pins and use Herbie tube dampers.


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## Glod

Nice mini-review. I think it is important not to marginalize the 6SN7GTA, GTB’s and later non-U.S productions. I haven’t tried many my self, but the ones I have sound satisfactory IMO. They do not sound bad in absolute terms; it is just that there are 6SN7GT’s that sound very much better. BTW e.g. very early RCA 6SN7GTA sound quite alike the VT-231 version IMO. IIRC, the GTA was invented 1948. 

 However, as your review points at, there are no holy grails out there. The famous Tung-Sol round-plate/black-glass is perhaps one, but for the rest most tubes have their weak spots and combining them, if possible, become important in order to get a more complete sound. 

 An interesting phenomenon, at least in this forum, has been the introduction of 6SN7-like tubes such as the 6BL7 and 6BX7. A welcome alternative to the pricy early 6SN7GT. I am not sure they can be used in any amp tuned for 6SN7, but in the MPX3 they have been quite a revelation. A pair of, e.g. early 1950’s GE 6BX7GT as outputs, give a radically different sound than the nearest comparable 6SN7GT. If I was to dare a comparison, I would say they sound like a combination of a RCA VT-231 and a Raytheon 6SN7WGT (flat-plates): Warm, exiting, vigorous and eager and with better micro dynamics than the two 6SN7GT’s. Ultimately, however, I find the GE 6BX7GT to be larger than life, but interesting and fun they are.


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## aerius

Quote:


  Originally Posted by *Jon L* 
_Yup, RCA VT231 sounds kind of like AKG k340's. The treble is not as open as other 6SN7's, but the tone and density is something to behold._

 

That's for sure, especially when I put them together. I have 3 pairs of them now, a pair in VT-231 and two pairs as 1633's and I'm trying to secure a lifetime supply of them.

  Quote:


 My favorite 6SN7 tubes are all from this "tone and density" school, including National Union grey glass, Kenrad VT231 black glass, and the RCA grey glass. The NU Grey glass, if you can find it, is even more mythically magical. I haven't been able to find any more for a Looong time, though. Black glass, yes, but not grey glass. 
 

Yup, those are definitely on my list. I'll have to give that old-timer I met a call and see if he has any lying around that he can spare me. I used to think better extension in the treble would be the answer, but then I heard the midrange on the grey glass RCA's and was addicted. 

  Quote:


 A little trick to get around the treble extension issue with these Tone Kings is to use something like Walker SST Extreme to the tube pins and use Herbie tube dampers. 
 

Thanks! I have some conductive silver grease for switches & contacts which I have lying around. It worked for my RCA jacks so I guess I'll try it out on the tube pins.

  Quote:


  Originally Posted by *Glod* 
_Nice mini-review. I think it is important not to marginalize the 6SN7GTA, GTB’s and later non-U.S productions. I haven’t tried many my self, but the ones I have sound satisfactory IMO. They do not sound bad in absolute terms; it is just that there are 6SN7GT’s that sound very much better. BTW e.g. very early RCA 6SN7GTA sound quite alike the VT-231 version IMO. IIRC, the GTA was invented 1948._

 

That's definitely true. Against my Gilmore Lite, anything of the Electro-Harmonix level & up will begin leaving the solidstate amp behind. Only the Chinese tubes and exposed filament GTB are noticeably worse than the Gilmore Lite. The GE GTB is about even IMO, and it could go either way depending on preferences.

 I did get an early RCA GTA bottom-getter in a few days ago but don't have enough time on it to write anything conclusive. It does share characteristics with the VT-231 and the later side-getter. Has the seamless soundstage of the '231, but so far it sounds kinda muddy though it has cleared up a bit.

 As for the 6BL7 & 6BX7, I'll have to get a new filament power supply to run those tubes. I'm using a surplus rack-mount DC power supply and it's not rated for the amount of current those tubes will pull. I'd like to try them out sometime though, but that'll have to wait till I find a better power supply at the surplus store. Yes, I'm a cheapskate.


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