New DSL40 tube layout?

Discussion in 'The Workbench' started by DirtySteve, Oct 28, 2012.

  1. DirtySteve

    DirtySteve Well-Known Member VIP Member

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    I apologize in advance for the noob questions, but I just stepped up from a Class 5 and I can't find any of this info on the new DSLs. I kind of need a quick lesson. I'm not a total idiot about this, but I don't want to take any chances.

    I was just about to roll a couple of NOS preamp tubes in V1 & 2 in my new dsl40c when it dawned on me that I don't know what all these tubes are for and if I might screw something up if I put a wrong tube type in the wrong position. It's my first amp with more than 3 pres.

    Can anyone give me a rundown of what the preamps are? I assume V1 is closest to the input like any other amp? What are V3 and V4? I also assume V4 is the PI?...or am I way off?

    It also just occurred to me that I probably have to re bias if I swap power tubes????

    Any info at all in this department is much appreciated! :cheers:




    edit: I have some pix, but I can't download them to my computer at home, I'll post them if I need to in the am.
     
  2. Dogs of Doom

    Dogs of Doom Moderator Staff Member

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    Funny how google images refers back to this forum...

    [​IMG]

    Looks like the front row from right to left V1-V3 & the PI far left in front of the 4 power tubes...

    Typical is following the path from the input socket to the power section.
     
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  3. DirtySteve

    DirtySteve Well-Known Member VIP Member

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    Yes, but I'm talking about the new one that was just released. The tube layout is different than that in mine. I'll post photos in the morning. There are 4 preamp tubes in mine and 2 power tubes.
     
  4. big dooley

    big dooley Well-Known Member VIP Member

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    V1 and V2 are the gain stages,
    V3 is the last gain stage and cathode follower
    V4 is the PI
     
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  5. DirtySteve

    DirtySteve Well-Known Member VIP Member

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    Thanks Dooley, that helps. ...and V1 is closest the input? Are there certain tubes that shouldn't be used in the Cathode follower? I've read that somewhere before and I want to be sure...and what's a good PI tube? The last time I had a PI was in my PV classic 50 and the Sovtek LPS was highly recommended on the PV forum.

    I guess I have to open her up after all if I want to swap el34s, and I think I want to check the bias anyway. Where can I find out what it should be set at?
     
  6. DirtySteve

    DirtySteve Well-Known Member VIP Member

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    Sorry, I must have misread your post earlier. So V1 is closest to the input just like normal and the 4th pre is indeed the PI. Thanks man. :hippie:
     
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  7. big dooley

    big dooley Well-Known Member VIP Member

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    i'm not sure about these new series,
    but i avoid anything from new sensor like the plague for the cathode followers (in truth i avoid them anyway, but that's personal preference)
    as for other positions that's up to you... happy experimenting :)

    as for bias, just stay under 70% of max plate dissipation
     
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  8. Dogs of Doom

    Dogs of Doom Moderator Staff Member

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    No worries... I figured there might be a little differences between the models, but by looking at the image, you should be able to figure it out.

    I posted some other pic's in the other thread too. Maybe not identical, but should give clues to what to look for when you take it apart.
     
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  9. DirtySteve

    DirtySteve Well-Known Member VIP Member

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    Forgive my ignorance, but how do I know what 70% of max plate dissipation is? I'm learning here...:)

    Thanks guys. I really only want to swap V1 & 2 right now and check the bias, I might swap in some GT EL34Ms I have, but I'm more concerned with the pres right now. I wanted to know what the other ones are for too just in case I get froggy and want to go further. I have a bunch of NOS pres sitting here all laid out. :naughty:
     
  10. Dogs of Doom

    Dogs of Doom Moderator Staff Member

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    The problem is it's very subjective. Not only that, but you can have a recipe that works in one DSL & sound muddy, or flat in another.

    As a matter of fact, I swapped out the stock tube in my JMP-1 for the 1st time not too long ago. I put a Genalex Gold Lion in & it sounded more Marshally goodness than ever before (not to say it didn't sound Marshally to begin w/). Now though, using it w/ different amps & using the JMP-1 through the EL34, it's not doing what I liked about it in the 1st place so much.

    Using the JMP-1 direct into a board, through the speaker emulators, it kills. Through the direct outputs into either my Ampeg VL, or the EL34, it gets muddy & loses clarity in the mids.

    You'll have to swap out #1 w/ just about everything you've got to see what you like best. Then go on to the rest of the stages.
     
  11. big dooley

    big dooley Well-Known Member VIP Member

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    by measuring plate voltage and the voltage on the testpoints and do a little calculation...
    you don't want to exceed 70% of 40 watt (20 watt per tube) on idle
     
  12. DirtySteve

    DirtySteve Well-Known Member VIP Member

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    Thanks guys. After watching tube biasing videos all morning I think I'm in a little over my head, I'm just going to leave the power tubes alone for right now. I'm only going to mess with V1 & maybe V2. I don't think I need to get into anything else just yet.
     
  13. shades of blue

    shades of blue New Member

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    Same here...I think I put my tubes in backwards! I though the tube with the cover was the PI, and I went backwards considering V1 the furthest from the jack...

    I wish Marshall put a tube layout in their manual like Mesa, Egnater, and all other amp manufacturers! Their manuals are for crap.
     
  14. Rocktane

    Rocktane Well-Known Member

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    The PCB has markings for all the preamp tubes :)
     
  15. shades of blue

    shades of blue New Member

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    do i have to remove the chassis from the cabinet to see them? Sorry just not familiar with Marshall amps.
     
  16. DirtySteve

    DirtySteve Well-Known Member VIP Member

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    You do, but I don't think you need to. V1 is closest to the input. I only swapped V1 and 2 and difference was huge, so I'm pretty sure of it. None of mine have a cover, but V1 does have a rubber ring on it.
     
  17. Rocktane

    Rocktane Well-Known Member

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    Correct. And they are in order as well. V1 in the 100H has a cover.
     
  18. shades of blue

    shades of blue New Member

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    Thanks! The thing that was throwing me off is that the power tubes on the new DSL100 are not in line with the preamp tubes. The power tubes sit directly behind the preamp tubes.

    Like this

    [​IMG]
    not my pic!
     
  19. Stringjunkie

    Stringjunkie Well-Known Member

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    That's purdy!
     
  20. DirtySteve

    DirtySteve Well-Known Member VIP Member

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    Remove the 2 outside power tubes, but leave the holes for the sockets and it's the 40w. It's the exact same chassis. I have pics of mine to post, but I can't do it from home and I didn't go to work today to do it there.
     

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