Let's talk about 6SL7 tubes!

Discussion in 'Amps [BG]' started by BurningSkies, Jun 24, 2012.


  1. BurningSkies

    BurningSkies Supporting Member

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    We've had plenty of threads about 12AX7, AU7, 6L6, etc. But a bunch of amps and pre-amps use 6SL7's and now that I've got one, I'd love to hear everyone's experience with the both modern and vintage tubes. Lets discuss their general tonal profile and/or any of differences in types...and of course the any of the 6SL7 variant tubes (like the Russian 1579).

    What say you?
  2. BurningSkies

    BurningSkies Supporting Member

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    First up, I have on hand a couple Sylvania green label 6SL7's that TB'er wcriley sent me...currently untested...I also have a Tung-Sol pull that is untested. I'll give them a try in my new preamp once it re-arrives at some point. I also have a pair of NOS Russian 1579 coming, purportedly from 1950's production.
  3. beans-on-toast

    beans-on-toast

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    I love the rich tone of the octal tubes like the 6SL7 over that of the 9-pin tubes as the 12AX7. I think that they sound better.

    The great thing about the 6SL7 is that NOS tubes are readily available at affordable prices. Although they've been going up in the last couple of years. I primarily use Sylvania, RCA, Tung-Sol. Ampeg used mostly Sylvania in their B-15's.
  4. beans-on-toast

    beans-on-toast

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    This is a good seller.
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  6. BurningSkies

    BurningSkies Supporting Member

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    Unfortunately, I don't have a tester...but I did put the Tung Sol in the V1 of my Monique for some trouble shooting (it was having output level problems), but I found it seemed to be higher gain, bigger and fuller than the stock Shuguang V1. I won't know if that's true until I get the preamp back from Jule. But in that slot, the Sylvania seemed pretty even compared to the TS which was a bit wild and maybe a touch microphonic.

    From what I can tell they sound different from the 'standard' 12AX7 tone. A bit more punchy and attack on the front side of the note. Fender style implementation of the 12AX7 seems so smooth and soft...
  7. BurningSkies

    BurningSkies Supporting Member

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    Thanks! I know that Passinwind likes the brown based Sylvanias...and they're reasonably priced. I'm sort of wanting to see if I can score some red base RCA/JAN if I can for less than an arm and a leg...
  8. LowEZ

    LowEZ Supporting Member

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    I've tried new production Tung-Sol 6SL7's in a 1960 Ampeg Jet in the preamp/tremolo and phase-inverter positions. I was not happy with the result. The preamp sounded a bit sterile and the tremolo sounded like a helicopter. This was with brand new coupling caps and new resistors where needed. Any of my old, worn, microphonic 6SL7's sounded much better. Ampeg used Sylvanias a lot and I prefer those although they're getting pricey.
  9. BurningSkies

    BurningSkies Supporting Member

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    I'm not loving much of the new tube production in the world right now. I thought that the JJ's (6L6/12AX7) I bought about 5+ years ago, were decent but they seem to have QC problems. The Shuguang tubes that were sourced for my Monique are supposed to be nice 'audiophile' tubes but Jule's had a high failure rate with the current batch.

    I'm trying to not go too crazy yet, but I love options and I love that sense of hitting that one tube that just does it for you. I don't want to sink hundreds into them right now, but the 6SL7's are fairly cheap.
  10. beans-on-toast

    beans-on-toast

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    I've run into one "equivalent" NOS 6SL7's that could not take the normal plate voltage of a 6SL7. You have to be careful to verify the data sheet specs of these other tubes to ensure that they will run in your amp. Knowing what voltage your amp applies to the plate would help.

    Those red base RCA 5691's are very nice. They have a 10,000 hour service life rating.

    Tube testers can check out a number of important parameters. The problem with them is that a tube that provides an acceptable transconductance (one of the important things to examine when checking a tube) reading at one plate voltage may not function as well at another plate voltage. That is why, for optimal results, it is important to take these readings at the plate voltage of the amp that the tube will be used in.
  11. JimmyM

    JimmyM Supporting Member

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    What about the bottle size? Are there any characteristics inherent to bottle size?
  12. beans-on-toast

    beans-on-toast

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    For these sort of tubes, bottle size is usually related to plate size. Longer plates require a longer bottle. Longer plates dissipate heat better. Longer plate tubes can be prone to higher micro phonics. There are always tradeoffs.

    I don't know if the shape of the glass envelope serves a purpose. Perhaps a coke bottle shape can add strength. Some tubes have thicker glass than others. This helps with heat dissipation.
  13. Passinwind

    Passinwind Charlie Escher Supporting Member

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    I like this "one particular one" I got from Brent Jesse a whole lot, in my decidedly non-standard issue homemade preamp. I returned something else (his return policy rules) and threw myself at his mercy, and he sent me something in JAN Sylvania brown base, green lettering, short glass, halo getter, and tested specifically for lowest microphonics. I think these run $30-40 these days.

    Not sure how that translates to anyone else, but I'm definitely subscribed to this thread...;)
  14. JimmyM

    JimmyM Supporting Member

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    http://www.head-fi.org/t/353051/best-sounding-6sl7-short-glass-version-tubes-advice-need-it-pls

    Here's a thread with some comparison talk that looks pretty good. The guy who seems to know the most about them just sold me some excellent NOS 6N1P's for my REDDI.

    I've only got experience with Sovteks, basic Sylvanias, and briefly basic RCA's. The Sovteks ran forever but my B-15 was beat before I had it restored and they ran their course by then, so I couldn't tell you what they sound like in comparison to the Sylvanias. And the RCA's I tried sounded like the Sylvanias to me but they all crackled so I returned them and got Sylvanias. I've tried short and long bottle and I really couldn't detect much of a difference. Good sounding tubes to my ears. That's what they originally came with, too.

    But they were the $15-20 kind of Sylvanias and RCA's, not the $30-150 kind. I've not tried the JAN Philips that came with the Heritage B-15, but my tube guy told me they were the same as Sylvanias anyway, and he's really up on stuff like that. But after getting my mind blown by throwing an expensive tube in the REDDI, I might be up for seeing if I can create the same excitement with my B-15. Would I need to swap out the phase inverter tube too, or would channel 1 be enough?
  15. chadds

    chadds

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    Okay this is just great. :meh:
    A thread like this could raise the prices of these things. :):eek:

    In my testing in the Monique Rack:
    To my ears the black plate RCAs were the sweetest.
    The Sylvanias had a rough lower mids with otherwise clear sweetness.
    The GEs were as good as the Shugaungs. Just not as musically exciting as the others.
    I have some Shugaungs that were made more than a year ago that are reliable noise free (little gurgle on start up) and I won't replace until they go bad. They are musically interesting.
    The JAN Phillips is very very sweet.

    Definition of sweet: open, airy, full hifi frequency response. No mud. No grit except what you make with your attack. A very pleasant richly harmonic sound. Allows all the strings overtones to be expressed.

    Some tubes that weren't labeled JAN are the same build. The armed forces determined that the consumer tubes met their specs.
    Tube testing won't necessarily reveal microphonics. Pete Cage has this device that can detect some.
    An EM pulse from a Nuke and that hard banked turn in your B-52 to avoid the cloud and shock wave won't reveal the tube's microphonic tendencies.
    The tap I can deal with. The howl like "Dog Symphony #4 by Hounds Boneman" sounds like you have a looper.

    In my case a very microphonic tube works great in V2 where the gain is much much lower.
  16. BurningSkies

    BurningSkies Supporting Member

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    Chadds, I'm surprised that the GE's weren't that good. I tend to like them better than Sylvanias for other tubes. I won't really know what the ones I have sound like until I have my Monique back, and try one in V1 to see. I did try it briefly but was having such low levels it was hard for me to make any kind of judgement. I can say that the Tung Sol in V1 sounded way bigger, fuller and 'more'. Unfortunately, it also appeared to have some microphonics happening, which won't do.

    I wonder this too. The Tung Sol I mentioned above had a recognizably larger envelope and longer plates, of course it seemed to have higher gain and some microphonics. Speaking of which, the reputation of the 6SL7 seems to be one of much greater chance of microphonics...I assume that's because it's a larger tube with longer plates than the standard issue preamp tubes, and microphonics are of a physical/vibrational nature. True?

    The JAN RCA's with red bases and black plates interest me (beyond the fact that black plate RCA's tend to sound pretty nice) because they also have triple mica spacers and additional support rods. All of that suggests to me lower chance of physical problems in the tube.

    One of these days I'll invest in a tube tester...if Lady Skies will let me have one in the house...
  17. BurningSkies

    BurningSkies Supporting Member

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    I was thinking of the V2 slot...The problem is that once on my rig, with a fair amount of volume, even when isolated there's some vibration and that could lead to microphonic noise when playing at LOUD volume...and that of course wouldn't reveal itself until I'm on stage and playing one of those gigs.
  18. wcriley

    wcriley

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    Skies: putting your rack somewhere other than on top of the cabs would prevent this.

    My amp is almost always on a stand to my immediate right...But then, I run sound from the stage, so it's easy to put my bass rack under the mixer/on top of the PA rack.
  19. BurningSkies

    BurningSkies Supporting Member

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    True, but probably not in the cards. I'm a firm believer in the amp-on-cabs school of thought. ;)
  20. wcriley

    wcriley

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    Should have known you were a "traditional appearance" over "more functional" type of person. :D
  21. BurningSkies

    BurningSkies Supporting Member

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    Its just easier for me. Rather than carrying an extra stand and sometimes not having space, also ergonomic...since my amp setup is at eye height. The less stuff that's spread on stage the better and less stuff for others to knock over. My cab's ain't goin' anywhere.

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