Dropping 6v6's into a 6l6 amp?

Discussion in 'Amps and Cabs' started by sovtekking, Oct 21, 2008.

  1. sovtekking

    sovtekking Supporting Member

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    Hey guys, I'm currently a senior in electrical engineering so I'm a pretty knowledgeable guy but they don't teach us much at all about tube technology these days. I love 6v6's in every amp I've ever heard them in so I was wondering if you can "backfit" a 6L6 amp with a set of 6v6's with a rebias on the tubes to get the current and voltage matched up correctly for the 6v6? Are there any concerns about doing this that one should know about even if it safe? Thanks
     
  2. gemmill

    gemmill Member

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    you can... sometimes just w/ rebias, usually w/ other tweaks required to get the b+ under control. it's a really nice sound in the right amp..
     
  3. Austinrocks

    Austinrocks Member

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    have on my fender Hot Rod Deluxe, love the tone of the 6v6 a couple of my originally 6L6 amps have 6v6 tubes, my Mesa Mark IV is designed to accept the 6V6 and EL-34, just set it up with the power in tweed mode and running simulink, really get great tone, the Mesa Amps don't have a bias adjust, My Fender Hot Rod Deluxe a 40 watt amp is running 6v6 as well, got the tubes from euro-tubes.


    from eurotubes site

    http://www.eurotubes.com/euro-l.htm#2


    It's common knowledge now for most net surfers that we have been using the JJ 6V6's in HRD's since December of 2003 and the most common question I get about this is "does this work and will it harm my amp". The answer is yes it will work and no, it won't harm your amp or I would not recommend it... I have LOTS of HRD customers that have been using the 6V6's for over three years now with no ill affects what so ever. There are no mods necessary to do this. The transformers do not need to be changed nor do the screen grid resisters need to be changed. The only thing necessary is to bias the amp for them.
    The bias on HRD amps will rarely get the 6V6's as hot as they can be run which would be between 40 to 45mv at the test points for Hotrod Deluxe's and 30 to 35mv for Hotrod Deville's, but the JJ 6V6's have the ability to sound VERY good at lower bias settings clear down to 25 to 30mv. You will probably be very happy with the tone anywhere from 25 up and if your Hotrod Deluxe will not get the tubes up to 40 ( some will & some won't ) and you want to get them up higher then you can change the 100K resister ( R77 ) that is in series with the trim pot to a 70K and then you will be able to use all grades of 6L6's and get the 6V6's up to maximum levels. Now these will NOT turn your HRD into a bedroom quiet amp but it will cut the power down from about 40 watts to around 28 to 30 watts so it will still be plenty loud but it will have that cranked Deluxe Reverb vibe. For you HRD players still after maximum headroom stick with the JJ 6L6GC's.


    and some biasing videos as well

    http://www.eurotubes.com/euro-video.htm


    The hot rod deluxe is easy to bias,
     
  4. Sparky6string

    Sparky6string Member

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    I would recommend only using the more robust JJ 6V6's if you do this. I have switched out el34s for JJ6V6s with great results. From what I understand el34s bias more closely to 6V6s than do 6L6s. Also I think I remember reading that there would be a difference in output impedance when switching 6L6s to 6V6s. You may want to post this question at the Amp Technical Info forum here at TGP if you don't get all the details you need. The whizzes there should be able to help.
     
  5. wyatt

    wyatt Member

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    The trick here is to watch the plate voltages.

    Most NOS 6V6GT's are good in amps with plate voltages up to 425VDC or so. This is the average plate voltage of a Deluxe Reverb and they ran those tubes pretty hot. But that is okay, tubes are consumables were were never intended to last a lifetime.

    Modern 6V6GT's have improved incredibly. It is less than 2 decades since there weren't any 6V6GT's made and then for the longest time the only option was the Sovtek, which was delicate and often blow in amps with plate voltages much over 400VDC (this is why Fender biased the DRRI so cold for so many years). But then the EH hit the market, and despite some infancide issues, they proved to be a rugged enough tube to easily handle 425+VDC; it's the tube that allowed a lot of designers to return to 6V6 designs. And the Tung Sol is gettingeven closer to NOS tone and perfromance. And we have the JJ, which is sort of a 6V6/small-bottle 6L6 hybird than can handle up to 500VDC, but it does have a little 6L6 tone in it as well.

    So, if the amp's plate voltage exceeds 425VDC, I would go with the JJ's until you get to 500VDC. Above 500VDC, you would have to rebuild the power supply.

    You also have to remember that the primary impedance will change at the output trasnformer, so you have to adjust the secondary tap/speaker load accordingly.
     
    Last edited: Oct 21, 2008
  6. sovtekking

    sovtekking Supporting Member

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    These are all great responses and advice. Keep ém coming guys!!! I'm gonna have to break out the 6v6s and try this out. Biasing is remarkably simple with most modern amps so it should be a fun little swap.
     
  7. Mickey Shane

    Mickey Shane Silver Supporting Member

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    You can also lower the amps plate DC by lowering the AC in with a variac.
     
  8. orogeny

    orogeny Supporting Member

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    my buddy has been buggin' me to put them jj 6v6 in my rott to replace the 5881s in there. . .

    might have to finally give it a try. . . .
     
  9. mindwave_21

    mindwave_21 Member

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    Bob from Eurotubes said they don't work in my Traynor YCV40. Cathode biased, 6L6, something about the bias isn't suited for 6V6's.
     
  10. Zelja

    Zelja Member

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    For those that are worried about the V+ voltage doing harm to their non-JJ tubes, you can try a Weber copper cap instead of your GZ34 rectifier, but use an equivalent with a greater voltgae drop, like the WU4GB. The standard GZ34 replacement (WZ34), drops the voltage 17V while the WU4GB (a 5U4GB replacement) drops it 50V. Hence if your normal V+ is say 425V with the GZ34 rectifier, the V+ would drop to 425 - (50 -17) = 392V.

    On the webpage they say they are developing a unit to give variable V+:
    http://www.webervst.com/ccap.html

    Of course the unit can still be useful withh JJs as by dropping the V+ you will get less total volume, quicker onset of overdrive etc. You will get more sag as well I'm guessing.

    Warning/Note - just dropping in an actual 5U4GB may be hazardous & as I'm pretty sure they require more heater current than the GZ34 & hence your power transformer may not cope. The copper caps haven't got a heater coil, so it's a non-issue.
     
    Last edited: Oct 21, 2008
  11. sovtekking

    sovtekking Supporting Member

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    Homeboy know's his amps!!
     
  12. Zelja

    Zelja Member

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    Aw, shucks, thanks. I'm no expert as I still don't understand 100% how phase inverters work :messedup among others things...

    Did EE, cause I wanted to build a guitar amplifier, in the early 80s & no tubes info then either. It took me 20 years to build an amp (actually retrofitted a Fender bassman 20 & turned it into a tweed deluxe type thing). For my thesis, I did design/build a guitar to midi (synth) interface before they were commercial available - -worked too :eek:

    I've used the copper cap & 6V6s in my '64 Fender Vibrolux & was happy with the results. I'm sure you'll have fun with your amp too.
     
  13. sovtekking

    sovtekking Supporting Member

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    yeah I'm pretty good at taking the solid state info we get and relating it to tube tech. even though it's not really the exact same thing. I've learned a lot from doing EE but really it's getting more and more programming an digitally oriented. I got into it for the same reasons you did and I'm slowly realizing that even EE is slowly becoming a subset of Comp Eng with the way technology is headed these days. It's a good thing that people still offer tube amp classes and instructional material to help those of us who are on the brink of really good amp techs. Most amp/electronic techs I know aren't very passionate about their work and just do it as a means to make a buck so I'm glad to see some people still "doing it for fun" so to speak.
     
  14. Blue Strat

    Blue Strat Member

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    Sometimes. What amp is it? What's the plate voltage? Is it fixed or self biasing?

    There's no pat answer to your question so avoid responses that don't ask for more information.
     
  15. gixxerrock

    gixxerrock Member

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    I'm an EE as well. I felt a little cheated when they dropped tubes from the curriculum in our electronics courses. If you are really interested pick up an old text book and learn it the proper way. It is not that different from doing it with transistors.
     
  16. rockon1

    rockon1 Member

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    +1 If your under 500v(hopefully a good bit lower) and its fixed bias I'd fell more comfortable doing so -at least with a set of JJ6V6's as long as you get the bias down to what it calls for for the PV (17-20 ma-depending of coarse on the pv) Bob
     
  17. jmcorey

    jmcorey Supporting Member

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    I talked to Joe at Traynor and he said not to do this swap....
     
  18. rockon1

    rockon1 Member

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    Running the JJ 6V6's in my Rivera Chubster for a few weeks now-no problems. The amp is designed for EL34's and runs at 430 volts on the plates. bob
     

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