6550 or El34

Discussion in 'The Workbench' started by jan norberg, Oct 31, 2020.

  1. jan norberg

    jan norberg New Member

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    Hi,
    Just bought a brand new AFD with 6550 as original valves. How will it sound with El34? I have ordered Mullards. And should i go for new ecc83s as well.
    I have had a lot of different Marshalls through the years but never changed any tubes.
     
  2. junk notes

    junk notes Well-Known Member

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    :welcome:

    I gigged a 100w amp that had this feature. Switching back and forth, the 6550s had more headroom and chords bloomed, but made my leads sing with the EL34s.
    Any experience with substituting E.H. 6CA7? I would like to A/B a quartet of 6550-6CA7 to hear and feel these differences.
    (I also would like to try the new Shuguang fat bottle/short plate 12AX7 in V1 with either/or the 6550s or EL34s. :yesway:)
     
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  3. Ray Baker

    Ray Baker Member

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    Jan, First off, Welcome. Second, word of caution. You can't just swap to EL34's without making other changes. I am not up on the AFD, but I have four different Marshall 100w heads and it's not just a simple as changing the tubes. There are resistors that need to be changed. Again, I don't know a lot about the AFD but when I considered changing my 1979 JMP Mark II N-MV 6550's to EL34's I changed my mind quickly. I am guessing you purchased the AFD specifically for the Slash sound. They are installed in the AFD for a reason. That's what was in the head Slash rented from SIR. Second reason the original head had 6550's is that the US importer was getting beat up on warranty claims as the EL34's weren't holding up during the shipping the the US back then. I do know the AFD has an "Auto-Bias" feature, that feature my be able to overcome the issue , but again I don't know enough about the AFD to be sure. In the vintage heads I have if you change the tubes and do not change the resistors you're going to have issues (an amp that likely does not sound like your looking for). I really encourage you to re-think this and / or read up more on it before installing the tubes you ordered.

    Update .... I did a follow up to understand the ADF 100 better. As IOSEPHVS pointed out in his response to my original post, You can simply install EL34's in the amp. You can actually install a variety of different tubes. Having said that, I have to agree with Marshall Boogie, you're going to see more difference swapping out the pre-amp tubes. I am guessing that your 6550's are still good so now that you own the EL34's that are on order you'll just have to install them and do a comparison with your cabinets, guitars and any effects that you may use. It will boil down to preference. For all of my heads I get my tubes from Eurotubes.com and I get the Hi Gain option when purchasing new tubes.

    I also took the following from https://www.slashparadise.com/equipment/marshall-afd100-slash-handbook.pdf:

    3.BIASFAULT Like any high performance machine, parts such as valves wear out over time. It is essential that these all-important components are working properly and that’s where the valve fault indicator comes in very useful. This system allows you to monitor the AFD100’s power amp and clearly indicates any valve that has developed a fault while performing the biasing procedure. If lit under normal use, it may indicate that a valve is faulty or that some kind of temporary fault was detected and the valve needs to be examined. If all four LEDs are lit, this could signal that the HT fuse has blown and needs to be replaced. Only use the same HT fuse type as indicated on the rear panel.

    NOTE: It is possible to have different octal pentode or tetrode power valves installed in your AFD100. Some popular options include EL34s, 6L6s, 5881s, KT66s, KT77s and KT88s.
     
    Last edited: Nov 1, 2020
  4. IOSEPHVS

    IOSEPHVS Well-Known Member

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    I used to own a Randall RT503 head and the matching Celestion loaded 2x12 cabinet. Like the AFD, you could swap out various octal tubes, and adjust the external trimpots according to the chart in the manual. It shipped with 6L6s which I thought sounded great until I put in a set of EL34s. I went back and forth for awhile and eventually stuck with the EL34s.
     
  5. IOSEPHVS

    IOSEPHVS Well-Known Member

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    Actually, with the AFD it is as simple as swapping the valves and adjusting the external trimpot.
     
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  6. Marshall Boogie

    Marshall Boogie Well-Known Member

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    I have a Mesa Boogie Mark V and it has the ability to switch between 6l6 and el-34 and frankly I find I heard more difference between tall bottle and short bottle 6l6 than I hear between 6l6 and el-34. Just my opinion but personally I think the differences between the tubes are more hype than reality. You get much greater impact switching preamp tubes, there are some real differences.
     
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  7. jan norberg

    jan norberg New Member

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  8. jan norberg

    jan norberg New Member

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    Hi guys!
    Many many thanks for youre input! I love the amp as it is but i will ofcourse test it with EL34, my favorite valve.
    I just bought the amp from the former distributer here in Sweden, where it has been laying around in their warehose for aprox 10 years. So i broke the plastic and lifted it from the box...
    in my opinion the 2003, Silver Jubilee and the Slash amps are Just great amps. My rig is now one AFD and one 2555X through 2 2x12” cabs. The Silver Jubilee is for Strats and ”clean/crunch” and the AFD is for my Gibsons.
    long live rock n roll.
    All the best
    Janne
     
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  9. Ray Baker

    Ray Baker Member

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    I would certainly love to hear a before and after.
     

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