6SN7 adapter for VTA120

After a nice vacation I returned refreshed and ready to try out the 12AU7 to 6SN7 adapter I received from eickmewg. I plugged in a GE 6SN7GTA I had on hand and after some warm up time I listened to several tracks. I didn't notice too big of a change over the RCA 12AU7 I had been using. One track did highlight good separation of instruments. I heard better distinction of a guitar line in Rachael Yamagata's song, "Nobody" from her latest CD, Tightrope Walker. Sadly I only had about 30 minutes of listening time last night. I'll keep listening and have a few other 6SN7's to try out. Electro Harmonix, Sovtek. I've had them for years and was never too impressed with them before but I'll try them. I also want to pick up some more to try out. Stay tuned!

Eickmewg was nice enough to send me a 6SN7 TO 12AU7 Convertor Adapter adapter along with a Raytheon 6SN7 tube. It had a hand written label with LNSR79 on the label. Not sure what that means.
Anyway I installed the adapter and tube and just to make sure everything was set correctly I also re-biased the Genelex KT88 tubes. I was also running a Genelex GZ34 rectifier.

When I first powered up it sounded as if the low end was a little more clear and not as mushy. The highs seemed smoother also. However after about 15 or 20 minutes I heard a strange buzzing noise that I at first thought was a neighbors lawnmower (I walked out of the listening room for a moment). When it happened again while I was in the room only this time it was louder. I quickly shut everything down. A few days before this I noticed a clicking noise coming from the the right speaker and it was suggested I tap the tubes to break free any material that may have accumulated on the inside of the tubes so I then removed all the tubes and lightly tapped the top of each tube. I also switched positions of the tubes to see if the clicking sounds and the 'lawnmower' sound moved to different channels. I re-biased the tubes again and after a few minutes the 'lawnmower' sound came back. No clicking sounds though. Same thing when I switched to a Webber rectifier. I replaced the 6SN7 with my 12AU7 and thus time the only sounds coming from my speakers was music. Complete silence between tracks with either the Webber or Genelex rectifiers.

Could the sounds I was hearing be the result of the tube being microphonic? If so would switching to a different 6SN7 possibly cure the problem?

After that GE tube I tried a couple of nos tubes that had all identifying markings worn off. One sounds fantastic and the other immediately hummed like crazy in both channels. It's probably the tube.

I'll buy and try a new one. I'm considering purchasing the octal board so investing in a few to experiment with may be the way to go.

Dogstar,
I'm sure that it was the tube to blame. Sorry about that. Let me send you another. I have a nice Sylvania 6SN7GTB that is dead quiet in my VTA ST120 I'll be happy to donate. I will mention that I initially had a new reissue TungSol 6SN7GTB that hummed like crazy, returned it to TubeDepot for a replacement, and the replacement was bad as well. I then got a matched quad of the 1959 Sylvania's that have been great. I'm only using three in my octal board. So, don't worry! Let me know if you want it.

Bill

Thank you eickmewg. That's really good of you. I'd be happy to send you the Raytheon or better yet compensate you for your generosity. Please let me know if I can do that for you. I figured if I bought new TungSol's I would be safe and I'm not sure I feel comfortable buying used tubes off of eBay. I wonder if the new Electro-Harmonix 6SN7's would be good. I've heard more people recommend staying away from JJ's though that may be a particular tube type. Of course I may also reach out to Jim McShane.

I really would like to try out a good 6SN7 tube. Again. Thank you.

Mine's still keeping me happy.



Been meaning to get into some of the so called "premium" tubes here, but really ... not much incentive, as the RCA coin base I'm using is mighty fine as is.

JJ has introduced 6SN7 as new production. It's built without "stem", the connections goes
straight to the socket, this shortens leads and reduces hum.
here is a link to one us-supplier ( not affiliated) :
http://www.eurotubes.com/store/pc/viewCategories.asp?idCategory=811

I have a bunch of good NOS 6sn7s you can try.  My experience with a Wright pre-amp is as follows:
Sylvania Chrome Top - Bass heavy, nice mid-range but a little flat on the top.
Baldwin Green label - Similar to the Sylvanias which should come as no surprise since they are relabeled Sylvanias.
RCA Backplates - Nicely extended up top, clear mid-range and less thick in the bass.  A favorite of mine.
Russian Metal Based with holes in plates - An all time favorite but really hard to source!  Sound great from top to bottom.  Sorry, I can't let these out of my sight.
Suguang CV-181-t or z - This is the nicest new tube I've found!  Beats the pants off of most fancy-pants NOS ones.  I'running these in my pre-amp currently and couldn't be happier.  Tube store has them for $109 a piece but they are buttery smooth with beautiful tone bass/mids/highs.  I've only got one pair so I can't lend one out.  Too bad. CV-181

I could probably put together a care package of three to four tubes for you to try.  They all have printing intact so you can determine what is working for you.

"RCA Blackplates - Nicely extended up top, clear mid-range and less thick in the bass. A favorite of mine.
Russian Metal Based with holes in plates - An all time favorite but really hard to source! Sound great from top to bottom. Sorry, I can't let these out of my sight.
Shuguang CV-181-t or z - This is the nicest new tube I've found! Beats the pants off of most fancy-pants NOS ones. I'm running these in my pre-amp currently and couldn't be happier. Tube store has them for $109 a piece but they are buttery smooth with beautiful tone bass/mids/highs. I've only got one pair so I can't lend one out. Too bad. CV-181"

My experiences exactly!

As with Kentley I keep going back to the Shuguang types CV-181 (including Psvane) with adapter at the center ST120 position. They beat out any NOS 6SN7s (and 12AU7s) that I have tried but I haven't tried them all of them. Deep bass, smooth extended highs, low noise, and holographic soundstage with the CV-181s. The last Shuguang CV-181T has seen almost two years use and still going strong with daily use. Runs so cools that you can touch its glass envelope without burning your fingers.

The CV-181s take forever the run-in and may sound strange for the first 50 hours. Should be on your list for audition at some point.

I concur at all levels ref: the Changsha-made CV-181s, whether PSV or SG.
Unfortunately Chinese tubes are a crap-shoot, QC-wise, however, which is why there are no U.S. retailers. They're not cheap, several I have are horribly microphonic, returns are an expensive pain. But a good pair of CV-181s in the SP-14 or in the driver holes of a VTA amp is ambrosia and will top your best NOS of any flavour and they live a long, long time.
As to the metal-based Russkie MELZ 6H8Cs, right up there with the CV-181s. However, nearly all the MELZ Russians need repair work off the bat, which involves de-soldering the base and pins from the tube itself, cleaning the wires, and re-soldering (use a decent Cardas or equiv.). For some reason the solder and/or Zek labour the CCCP used in final assembly were dreadful, although the glass guts themselves are top-notch. A less time-consuming quick-and-dirty fix is just to re-heat and re-flow the existing solder in the pins. Still a great tube at a fraction of NOS or CV-181 prices.

I've had bad luck with Shuguang KT-88s. Not recommended. The CV-181s and even their 12AU7Ts had been solid performers.

@arledgsc,
For some reason I've had much better luck with PSVanes than with Shu Guangs, even though they're made in the same factory -- whether KT-88s or the -181s.
Most of the Chinese dealers will make good on a lame tube. The problem is, returning a single tube via China Post costs more than the damn tube costs. My rough calculus is two in every eight SG tubes will be junk, whereas in the 16 or so PSVs I haven't had a single defect.
That said, I've got four SG KT-88-Zs that have been in my Don Sachs ST-120 for about 400 hours now and keep sounding better and better. I have them biased at 0.6VDC/tube and it has not budged since I put them in.

I have Psvane KT-88s, 12AU7, and CV-181.  Never had a problem with any.  

I have only use Shuguang's expensive Natural Sound KT-88Ts.  Sounded good while they lasted.  One tube opened and another shorted and blew a cathode reisistor after only a few months of use.  As a matter of fact a few days ago I rounded up the KT-88Ts and dumped them at the electronic scrap place.  Good riddance.  

I am so use to KT120s now I will never change.  They are just absolute perfect in my setup, last a very long time, and extremely affordable.

peterh wrote:JJ has introduced 6SN7 as new production. It's built without "stem", the connections goes straight to the socket, this shortens leads and reduces hum.

here is a link to one us-supplier ( not affiliated) :
http://www.eurotubes.com/store/pc/viewCategories.asp?idCategory=811

Thanx for the heads up on those ... looking for another option and that one sounds real interesting.

PS ... Eurotubes? Threw me for a minute there, but looks like they're in Washington state ...

sKiZo 503 area code is Oregon the state in which I live never heard of Eurotubes may have to check them out

https://s-media-cache-ak0.pinimg.com/originals/15/0a/d3/150ad3b4602806009a146967c3fc9e8c.jpg

Where the idea for the Eurotube logo came from?

I dunno but I like it. Just the right amount of cleavage.

Looks like the tube community back in the golden age of audio knew that sex sells. No wonder my family had a Zenith TV when I was a kid. My dad did have a Grundig console stereo he got as a Christmas gift from my mom back in the early 60's. I do remember the tube amplifier and AM/FM tuner with shortwave bands as well.

Last night I tried an Electro-Harmonix 6SN7GTB with fairly low expectations. I admit I was biased by my early experience with EH tubes in my ST70. I found EH EL34's kinda boring sounding but with hindsight there could've been other factors. That was my first tube amp and I had a lot to learn.

Anyway, the 6SN7GTB sounded pretty good. A little warm in the treble* region but good separation and space. I was happily impressed. I'll be doing more listening this weekend.





* could also be my hearing.

eickmewg was nice enough to send me a Baldwin 6SN7GTB tube that replaced the noisy tube he sent me last week. I listened to the Modern Cool CD by Patricia Barber. I think her recordings really test a system and if it's a good system help show off how good it is. Mine sound great. Thank you. I found when listening with my VTA ST-120 in Triode mode Patricia's voice stood out and the instruments seemed set back more. I then put it in Ultralinear mode and everything came forward though everything seemed smoother. Thanks again.

So, it seems the 6SN7 in the center position on the VTA ST-120 gets some love. I really like the octal driver board I built for my ST-120. It really is a pretty inexpensive experiment that you might like.

I may have to give EHs another try , , , like Corndog's my early experience with them was pretty dull but maybe there's a learning curve involved. Plus "back in the day" any tube that didn't sound perfect right out of the box was consigned to the junk drawer, which is no way to judge one, If you still hate 'em after 100 hours maybe they don't belong there, but 5 hours does not a test make.

I'd like to try out the octal board as well. However once I build the board and install it I really don't want to swap back so I may consider putting into a new amp altogether.

I only listened to one CD...perhaps 40 or 45 minutes total with the 6SN7 tube installed. One thing I noticed when shutting down was that all three transformers were still cool to the touch. I expected at least the center, power transformer, to be warmer than the other two since but all three were the same.