DSL401 - loop, tone and heat mods

Discussion in 'The Workbench' started by JohnH, Apr 23, 2014.

  1. JohnH

    JohnH Well-Known Member

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    Thanks for the reply - all the images are visible here. can anyone confirm? A while ago I moved them out of Photobucket to a different host so should be OK.
     
  2. Will Letourneau

    Will Letourneau New Member

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    38BB26AF-76AB-43E6-A391-5442A409E61F.jpeg
    I can see them now - maybe I had to sign in... Tonight I swapped out the BR for a tall cool one with a sweet top hat heat sink

    I want to do the OD mod and FX loop next
     
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  3. Will Letourneau

    Will Letourneau New Member

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    Reverb mod works great

    OD Tone and FX loop must have something else going on because I did not notice amything. I plug directly into the effects return and there is barely any volume...

    ....back to work on it another day
     
  4. JohnH

    JohnH Well-Known Member

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    Glad the reverb mod worked for you, sorry to hear about the others. Other people have done them sucessfully too, so something is amiss on yours. They shouldnt change how the controls work, just the tones and levels you get. Particularly, the fx teturn should be able to get a low-gain sound plugged straight into it ( try via a pedal) so maybe something wrong there
     
  5. Will Letourneau

    Will Letourneau New Member

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    Got a Scumback 65w 16 ohm speaker today and installed it. Put a delay on the loop and the FX knob to 100% and poof ! everything works like a charm

    I’m still very interested if we can ever get information from David

    Thank you JohnH !

    I have a gig tomorrow night so I’ll really be able to open up the volume.

    Cheers - Will
     
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  6. JohnH

    JohnH Well-Known Member

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    Great!. Did the OD mod work too? it should give you a thicker OD tone.
     
  7. Will Letourneau

    Will Letourneau New Member

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    Yes, I believe so. Not such a big difference between Audi one and OD to now

    I might still play with other capacitor values I believe right now I have 4 nanofarad total
     
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  8. JohnH

    JohnH Well-Known Member

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    Cheers. Good luck with your gig.
     
  9. Grim177

    Grim177 New Member

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    I've always used OD2 as OD1 never had quite enough gain for me but as there's way too much on OD2, I've never been able to turn the gain above 2/9 o'clock. After recently replacing V2 with a 12DW7 I can now turn the gain up to 3 (don't laugh it is a significant improvement) but I still feel I'm not getting all the bass that is available as it seems to increase in conjuncture with the gain. So I'm wondering should I be looking at decreasing the overall gain of that channel (not sure how I'd do that, lower gain valve in V1?) to allow me to get the gain up above 5 to bring the bass in more, increase the value of C99 or possibly both? I'd really appreciate some advice with this, other than get a different amp ;)
     
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  10. JohnH

    JohnH Well-Known Member

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    Hi Grim, increasing C99 might do exactly what you want, and its a very easy mod working from the top. I added 3.9nF to mine, which was 1nF before, but you might prefer less. Its described in the OP, but I see my pictures are not working today. So here is the shot of how you can connect the cap to the leads of other components that connect to C99:

     
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  11. Jon C

    Jon C Active Member

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  12. Grim177

    Grim177 New Member

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    Cheers John, You're a bit of a legend with this amp, a lot of what I've learnt over the years is from you. How much of difference could I expect though? I'm aware you're more of a fan of OD1 and the bass is even lower on that "channel". For me with the bass maxed out on OD2 and the gain at 3, I feel almost like I need another half a dial of bass on top of what I have and that is with the treble and mids just a hair over 1! My 1983 Lead 12 has more of an apparent low end!

    Hey Jon C, I've tried an MXR 6 band in the loop and in front. I don't like the way it changes how I'm hitting the pre in front and in the loop, even with all the other bands ducked aside from the low, I feel like I can hear an effected signal as well as a dry one. Having said that, with the 100hz boosted about 9-10db that's broadly the amount more bass I'd like to shoot for.
     
    Last edited: Dec 6, 2018
  13. JohnH

    JohnH Well-Known Member

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    Thanks Grim
    The C99 mod definately thickens up Od2, maybe not as much as you ask though. But theres no reason not to try it since its cheap, easy and reversable.

    If you arent using the loop for other things, and don't like an active eq there, there's the 'Bass boosting patch cable' trick. Its an external patch from send to return, with a small R and C built into it to let only lows through. If you turn up the fx knob, its worth about 3db of added bass in addition to whatever else is happening. Its posted here on MF, can find it if needed.

    But, could it be that you are looking for more bone-crushing lows than a small open-backed El84 combo can be expected to provide? I added an external closed back ported 1x12 cab to mine which really fills out the lower tones. When Im not using that, placing the combo on the floor, slightly tilted back, about 2-3' from a wall also adds bass by reflection.
     
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  14. Grim177

    Grim177 New Member

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    Thanks again John, Is it possible to test different values with some test leads hooked up to swap them in and out? What's is the absolute maximum value you would consider adding to the 1nf?

    Wouldn't the patch cable be doing essentially the same thing as my MXR 6 with all the bands cut except the bass which is boosted though? As soon as I boost any frequency in a parallel loop aren't I theoretically getting two signals, one boosted and one dry? That's what the pedal sounds like to me.

    I think my expectations are realistic. I'm just looking to match the bass and thud that the clean channel has on offer. As I say if I set all the EQ to 2 on my little Lead 12 combo everything sounds balanced and great. If I did the same on the DSL's OD it'd sound like a clock radio being played through a telephone.
     
  15. JohnH

    JohnH Well-Known Member

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    The loop might have been distorting with the mxr6? you might hear that as two signals. But if not i wouldnt expect so. Keeping tbe od volume lower might help with using the mxr, leaving more headroom for it to work with.

    My c99 cap value is probably near the limit with what can be achieved there. See graphs in first post.
     
  16. Grim177

    Grim177 New Member

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    Ok thanks. Another thing I'd like to ask you specifically if I may, when you changed out the power valves did you notice a difference in tone?
     
  17. JohnH

    JohnH Well-Known Member

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    I dont think so, going from stock (whatever they were in 2006) to JJ.

    But there was a significant dulling of the tone from the preamp, which also got JJ. V1 is key so I put an old one back, where it still is.
     
  18. Grim177

    Grim177 New Member

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    Mine is a 2005, the power valves were Marshall branded JJ's and the pre's are Marshall branded Shuguang. I found the same thing when putting a JJ into V1, it sounded significantly different and surprisingly dull. Although I thought it might actually be a good thing taming the treble and that I just needed to get used to it, after swapping back to a newish Shuguang there was no contest. The JJ sounded like the same amp wrapped in a duvet.
     
  19. Grim177

    Grim177 New Member

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    Has anyone experimented with changing the value of R100? This is apparently what governs the difference between OD1 and OD2.
    Am I right in assuming that doubling it's value (93k from 47k) would effectively reduce the difference to -10db rather than -20db?
     
  20. JohnH

    JohnH Well-Known Member

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    I havent tried it, but I believe OD2 is the natural full gain of the OD channel, and switching in R100 cuts it down to create OD1. The ratio is dependent on the ratio of R99 to R100, which is 470k to 47k, so OD1 has 1/11th of the signal voltage of OD2. Rounding off to the nearest order of magnitude, 1/10th of voltage leads to -20db reduction, as quoted in specs. Doubling R100 should leave OD2 as it is and boost OD1 by about 5db.
     
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