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    6L6GC to replace EL34 on st70

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    wantech

    Posts : 8
    Join date : 2017-09-26

    6L6GC to replace EL34 on st70

    Post by wantech on Tue Sep 26, 2017 11:56 pm

    Can I put 6L6GC set on st70 to replace EL34 set ?
    Do I have to adjust biaset ? same 1.56V or different ?
    Will they sound differently ?
    thanks...

    wildiowa

    Posts : 172
    Join date : 2012-03-19

    Re: 6L6GC to replace EL34 on st70

    Post by wildiowa on Wed Sep 27, 2017 5:22 am

    I have two EL34's from an old Marshall amp on one side of my ST70 and two 6L6GCs on the other side....not ideal, will catch much flak here for that....but it will work. not sure on the bias etc. But I think they are pretty much interchangeable. Isn't it essentially the EL34 is a British tube, the other a US??

    Dogstar

    Posts : 292
    Join date : 2014-06-23

    Re: 6L6GC to replace EL34 on st70

    Post by Dogstar on Wed Sep 27, 2017 6:22 am

    Did you try one of each on each channel rather than one pair on one channel and the other pair on the other channel? Seems like that may actually balance the sound better.

    GP49

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    Join date : 2009-04-30
    Location : East of the sun and west of the moon

    Re: 6L6GC to replace EL34 on st70

    Post by GP49 on Wed Sep 27, 2017 7:53 pm

    6L6GC is not the USA equivalent to EL34.

    6CA7 is.

    6L6GC is a lower-power tube, typically used in ultralinear amplifiers of 15-20 watts output power. It can be used in a Dynaco Stereo 70 if the idle current (referred to by most as "bias") is adjusted to the appropriate range for the tube.
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    peterh

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    Join date : 2012-12-25
    Location : gothenburg, sweden

    Re: 6L6GC to replace EL34 on st70

    Post by peterh on Thu Sep 28, 2017 12:51 am

    GP49 wrote:6L6GC is not the USA equivalent to EL34.

    6CA7 is.

    6L6GC is a lower-power tube, typically used in ultralinear amplifiers of 15-20 watts output power.  It can be used in a Dynaco Stereo 70 if the idle current (referred to by most as "bias") is adjusted to the appropriate range for the tube.

    6L6 is a lower power tube. 6L6GC is higher rated then EL34 ( but downward equivalent,
    you can replace a 6L6 tube with a 6L6GC but not the other way around)

    6L6(GC) and 6CA7 are both beam-tetrodes, EL34 pentod. But they will all work fine in
    a ST-70
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    PeterCapo

    Posts : 466
    Join date : 2008-12-05

    Re: 6L6GC to replace EL34 on st70

    Post by PeterCapo on Thu Sep 28, 2017 7:09 am

    I tried a set of the current production Tung-Sol 6L6G in my Stereo 70. I was unable to bias them with a 5AR4 rectifier in use. Substituting a 5U4 rectifier for the 5AR4 allowed the bias to be set to the originally prescribed 1.56 VDC, but IIRC it was kind of close. My AC mains was 122 VAC and I was using the dynakitparts PT with the 122VAC primary and a thermistor that dropped the AC mains a couple of volts.

    wildiowa

    Posts : 172
    Join date : 2012-03-19

    Re: 6L6GC to replace EL34 on st70

    Post by wildiowa on Thu Sep 28, 2017 8:33 am

    I read somewhere that the "GC" designation was merely a "glass case" sidebar and there is little difference in performance...but of course, that was off the internet!! So there are discernible, and distinct differences between the two? I come from the guitar amp world of 6L6 and EL34's...essentially, Fender vs Marshall. If you want to see a debate between these two tubes check out a tube guitar amp blog....the debate rages.
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    peterh

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    Join date : 2012-12-25
    Location : gothenburg, sweden

    Re: 6L6GC to replace EL34 on st70

    Post by peterh on Thu Sep 28, 2017 2:15 pm

    wildiowa wrote:I read somewhere that the "GC" designation was merely a "glass case" sidebar and there is little difference in performance...but of course, that was off the internet!! So there are discernible, and distinct differences between the two? I come from the guitar amp world of 6L6 and EL34's...essentially, Fender vs Marshall. If you want to see a debate between these two tubes check out a tube guitar amp blog....the debate rages.

    Note : 'G'  stands for glass, 'C' version C ( 30w plate limit)

    I'll quote :
    http://www.tdpri.com/threads/6l6-6l6g-6l6gc-whats-the-difference.710286/

    The 6L6 is a metal tube, and generally isn't used in gutiar amplifiers, it's rated at 360V max and 19W max plate dissipation. The 6L6G and 6L6GB are rated 360V max and 19W max plate dissipation. The 6L6GC is rated 500V max and 30W max plate dissipation. If you're running a typical Fender amp with their insanely high B+ you want 6L6GCs.



    See https://www.thegearpage.net/board/index.php?threads/6l6-vs-6l6gc-interchangable.561680/  
    And of course, applicable tube data sheets
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    Peter W.

    Posts : 552
    Join date : 2016-08-07
    Location : Melrose Park, PA

    Re: 6L6GC to replace EL34 on st70

    Post by Peter W. on Thu Sep 28, 2017 3:46 pm

    WARNING: Some (not all) ST70s, especially vintage devices, use one of the output socket pin terminals as a junction - for the EL34, there are no pins in that position. Using a metal tube in that socket may cause all sorts of havoc. BE EXCEEDINGLY CAREFUL!

    Otherwise a glass 6L6, or even a glass 5881 can be a very mellifluous, if lower power, option in these amps. Please used them in pairs, and please bias according to the need of the tube. I also want to repeat that there is NO reason electrically to use all-four the same type of output tubes.

    However, when rolling tubes at that level, making sure that the sockets are tight becomes an necessary habit at each change.
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    Tubes4ever

    Posts : 107
    Join date : 2015-07-14
    Location : Star, Idaho

    Re: 6L6GC to replace EL34 on st70

    Post by Tubes4ever on Thu Sep 28, 2017 11:34 pm

    wantech wrote:Can I put 6L6GC set on st70 to replace EL34 set ?
    Do I have to adjust biaset ? same 1.56V or different ?
    Will they sound differently ?
    thanks...

    Yes you can use 6L6GC in an ST70. Bias them the same as you would the EL34.
    I use them in my ST70 because I like the more pronounced highs as compared to EL34s. 6L6GCs have more "Chime" than EL34s.

    As others have noted, use 6L6GC not any previous version as they are not rated for the voltages present on the ST70.

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