Substituting EL34s with 6V6s?

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by somedude, Jun 13, 2008.

  1. somedude

    somedude Member

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    How hard would it be to substitue 4x 6V6s into an amp designed for 4x EL34s?

    The amp in question is an Orange AD-140. Despite the name it puts out around 90w clean. I'd like to bring it down to around 50w, but pulling one pair of EL34s just makes it sound anemic and doesn't really affect the headroom as much as you'd think.
     
    Last edited by a moderator: Jun 13, 2008
  2. hamfist

    hamfist Member

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    What sort of plate voltages does the Orange run on ?
     
  3. rockon1

    rockon1 Member

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    FWIW- I ran my Rivera Chubster (came with EL34's) with 6V6's. Generally(but not always) its a safe swap as long as you can get them to bias(enough range in the bias pot) and the plate voltage isnt too high. My chubster plate voltage is around 420V. I used JJ's as they are stout 6V6's. It was still pretty loud. Bob
     
  4. Blue Strat

    Blue Strat Member

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    If it doesn't blow up the 6V6s, this won't sound much less loud either. I can't speak for the tone.

    Sounds like you need a 20-40 watt amp.
     
  5. Swarty

    Swarty Member

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    I've been puttinge them in 50w Marshalls for about 15 years and it works great... '70s & '80s Marshall 50w typically have less voltage than a Deluxe Reverb. There is a substantial reduction in volume and 6V6s have bias voltage requirements very similar to EL34s. 6550 amps will require less bias voltage and thus may require a lower value bias resistor. NOS or JJs only.
     
  6. Blue Strat

    Blue Strat Member

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    I tried this in my '71 Marshall 50 watter and thought it sounded like ass ;)
     
  7. somedude

    somedude Member

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    Not worried about the volume, just the headroom.

    50w is what I need. I've had a couple of 15, 25 and 30w amps and they all lacked headroom. 100w is too much headroom, but I'd rather have an amp with too much headroom than too little headroom. Like I said, I tried the pulling the two tubes thing and the amp sounded constipated yet lost very little headroom. I figure the 6V6 experiment won't cost me anything 'cause if it fails to achive a good sound I'll just keep the tubes as spares for my other amp.


    I'm working on getting the plate voltage and bias pot range now.
     
  8. B. Bop

    B. Bop Member

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    I was thinking of substituting 6V6's for the 6L6's in my 64' Dual Showman. I believe that the output transformer has a 2K primary and was intended to have a 4 ohm load. So. if I connect the amp to a 8 ohm load it should cause the tubes to see a 4K impedance which I believe is correct for 4 6V6's. If memory serves me right I think that my amp put 460V on the plates. Should be OK with NOS or JJ 6V6's. Does anyone know if the bias voltage has enough adjustment to get the tubes biased down to about 20ma. If not I guess I could increase the value of the 27K resistor between the 10K bias adjust pot and ground to give the tubes a little more negative bias. Any thoughts?
     
  9. jamison162

    jamison162 Supporting Member

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    Sell the AD-140 and buy a Rockerverb 50. 50 watts, 4 6V6's, problem solved!!!
     
  10. somedude

    somedude Member

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    I own a Rockerverb 50. ;)

    The thing is the RV50 does clean and distorted really well. The AD140 does overdriven and really overdriven really well. I figured that if I could knock the AD140 down using a quad of 6V6s they'd compliment each other quite nicely.
     
  11. jamison162

    jamison162 Supporting Member

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    Get the AD30TCH then???
     
  12. somedude

    somedude Member

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    I had one. It didn't have enough headroom. It was great for loose, screamin' lead guitar (It made me feel like Jimmy Page. I still regret selling it for that reason alone), but it was too squshy for what I like to hear in my rhythm tone. Ideally, I'd probably be best off to get an AD50.... but a set of tubes is way cheaper than an AD50 so I'm trying to see what I can do before selling the amp (the RV50 has become my primary amp).

    EDIT: I also have a GT-120, so I don't really need a second 100w+ amplfier of the Orange variety, but a second 50w that has a totally different vibe and gain structure would be useful.
     
  13. jamison162

    jamison162 Supporting Member

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    What speakers were you using with the AD30? I bet a 2x12 of Eminence Wizards would be loud and clean with that amp. In addition, JJ EL84's biased around 55-60%, 5751's or 12AT7's in the gain stages and a SS rectifier substitution would have done wonders for that amp in regards to what you're looking for. To bad you sold it already.
     
  14. somedude

    somedude Member

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    Closed back 4x12 w/ Vintage 30s + open back 2x12 w/ Vintage 30s. JJ's EL84s, Tung Sol ECC83s. JJ GZ34. Volume on 10, gain around 7, guitar's volume/tone/PU selector used to control everything else.

    Volume wasn't really the issue as it was more than loud enough. Just not enough headroom. I figured that it was designed to be low headroom and decided not to fight the design. EL84s will never have the girth of an EL34 or even 6V6, so there was no use fighting it.

    Now that I have a RV50 as my main rhythm amp I may trade the AD140 in for another AD30 and pair them up on stage so I can kick on the AD30 as a solo boost. After all, it was the best lead tone I've ever gotten. Unfortunatly it just wasn't groovin' as a rhythm tone and at the time I needed a great rhythm tone more than I needed a great lead tone.
     
  15. jamison162

    jamison162 Supporting Member

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    Is your RV50 stock? I just put in some Tung-Sol 6V6's and biased to 20mA.
     
  16. jcs

    jcs Member

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    gotta agree with bluestrat (mostly), i have a 71 smallbox 50 as well and have tried the 6v6 swap several times,it always sounds anemic compared to el34s.

    to me, you match a circuit and trannys to power tubes, i dont get this whole thing of using less powerful tubes but maybe i'm missing something,i remember changing impedance and trying 2x12 cabs instead of 4x12.

    maybe i need to try a 1x12,but i dont get this whole thing.

    if anything i want to go the other direction and try some real tung sol 6550s in my 71 smallbox 50 (i know swarty likes em).
     
  17. Blue Strat

    Blue Strat Member

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    Possibly but one pair of 6V6s might work and another pair not. The reason we use matched pairs is that power tubes, at random, can vary by as much as 20 mA.
     
  18. somedude

    somedude Member

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    I've installed Tung Sol ECC83s in the preamp, however I've never had an amp that used ECC81s before so I don't have anything to put in the reverb and FX loop driver spots. What I'd like to know is if those two spots are very critical tonally (ie, will they benifit from a really nice valve), or are the best off with some kind of workhorse that's known for being robust rather than toneful?

    Power amp is stock with EHX 6V6. I plan on ordering a set of JJ and Tung Sols to see how each performs in it.
     
  19. jamison162

    jamison162 Supporting Member

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    I put a pair of NOS Mullard 12AT7's (CV2064 or whatever) in the Reverb and FX positions. I don't use the loop and only use reverb here and there. I fugre this $40 investment should last me 10 yrs. or more with this amp.
     
  20. telemoxy

    telemoxy Member

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    Or install a larger value bias pot.
     

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