DSL40CR Classic green too quiet?

Discussion in 'The Workbench' started by wrees, Nov 19, 2019.

  1. wrees

    wrees New Member

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    Loving my new DSL40CR, but I find that the Classic channel on green is too quiet compared to on red. I can balance the volume of the Classic and Ultra with the knobs, so no problem there. And on Ultra, there isn't much difference in volume between green and red, so that's no problem either.

    So, I need to either make Classic green louder or Classic red quieter. Can I do either of those with a safe tube swap?

    Thanks for any thoughts!
     
  2. South Park

    South Park Well-Known Member

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    You can start by swapping preamp tubes around and see if it sounds different
     
  3. Colnago

    Colnago New Member

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    Check to make sure it’s biased properly.
     
  4. MarshallDog

    MarshallDog Well-Known Member Premium Member

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    Maybe try a 5751 in V2 but it probably won’t work well at all. The way I understand it is that Classic Red adds another gain stage so it is what it is and changing other tubes will also have other affects.
     
  5. SlapHand

    SlapHand Active Member Premium Member

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    One MV for Classic Green and the other MV for the three other modes.
     
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  6. SkyMonkey

    SkyMonkey Well-Known Member

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    I have the same amp and posed this question soon after getting it.
    The consensus then was that this is just a quirk of the Mk II (40C) and Mk III (40CR) DSLs.
    The simplest way to balance the Classic channels is to assign a Master Volume to the Classic clean (e.g. green) and the other MV (red) to all the other channels. You assign by simply selecting and the choice is remembered by the amp.
    Set the desired volume for OD1/2 with the red MV and balance Classic Crunch to OD1/2 using Classic volume.
    Then balance the Classic channels using the different MVs you have assigned.

    This will lose you the option of using a second MV as a solo boost, but unless you have the 6 button footswitch you have to stop playing to do this anyway. Boost can always be achieved with an OD pedal out front, set to a clean setting.
    I balance the channels by setting the patch levels of my GT-100 in 4CM with MIDI switching. That way all the channels scale evenly together and don't need rebalancing when I change the MV setting.

    There are no circuit diagrams available yet for the DSL40CR, so we can't be sure of how the gain stages work. But the DSL40C uses the 2 sides of the V1 & V2 preamp tubes in different ways for the different gain stages of the channels and modes.
    The DSL40CR is probably the same principle.
    This is from @Micky a few years back on the DSL40C:

    "V1a is the input buffer for both channels of the amp. V1b is the first gain stage of the Ultra Channel. V1B is bypassed for the Classic channel.
    V2 is strictly a cascaded gain stage tube, the output of V1 feeds V2a, and that output feeds V2b. This is essentially the difference between Classic and Ultra, Classic goes V1a->V2a->V2b and Ultra goes from V1a->V1b->V2a->V2b. Follow me so far?
    From V2 onward, both channels go thru basically the same path, with only slight variations."

    I suspect @MarshallDog is right about V2.
    So if you try to tame the Classic Crunch channel by swapping a tube with different gain characteristics in its 2 halves (i.e. V2A & V2B) then the OD channels will be affected in some way too.
    A bit of fairly cheap experimentation could find you the answer.
    The tubes to try out may be the JJ ECC832 or ECC823.
    A tube like an ECC83 (that you have in the DSL) has the same gain (μ) of 100 for each half.
    The 832 and 823 have unequal gain (JJ call them system I and system II) of μ=100 and μ=17.
    The 823 is just the reverse of the 832. See below:

    ECC832.PNG

    So if the DSL Mk I principle holds for the DSL Mk II then one of these tubes should either step down the Classic Crunch in relation to the Classic Clean or exaggerate the differences that are there already. Depends on how 'in-channel' mode switching affects the gain stages used between Clean/Crunch and OD1/2 works. Is V2B bypassed for Clean and OD1? If so then you would need the ECC832. But that would lower the comparative gain of OD1 and OD2 too.

    There is also the question of the unusable gain of the OD2 channel. One of these tubes may make the OD2 gain more evenly distributed so you can turn the knob past 1 O'clock and hear a difference. i.e. same amount of achievable gain, but over a longer sweep of the gain knob.

    BTW My DSL has stock tubes and I have not tried any of these changes. (but I might)
     
    Last edited: Nov 20, 2019
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  7. wrees

    wrees New Member

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    Wow. Exactly what I needed. I'll try the 823/832 experiment and report back.

    I've been using the MV so far, but yeah, that takes away one of the reasons I got the amp.

    I'm using a Rocktron Xpression in the FX loop, which has an analog direct signal thru *with volume control per patch*. That's my plan B (C?) if tube swapping doesn't work out.

    Thanks again for all the tips, everyone!
     
  8. SkyMonkey

    SkyMonkey Well-Known Member

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    Can you hook up a MIDI footswitch to the Rocktron?
    If so then you might be able to utilise the DSL40CR MIDI switching with the THRU/OUT.

    I think if I were to try a different V2 tube, I would try the reverse 823 to increase the gain difference between the OD1 and OD2 modes! All depends on what gain stage (V2A or V2B?) is bypassed to create the difference.
    Hopefully someone will chime in with more definitive information than my guesswork!
     
  9. wrees

    wrees New Member

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    Question about this. That nicely explains how the difference between Classic and Ultra works, but how does the difference between green and red work for each channel? Does the extra gain in red mode come from non-tube circuitry? Or is the extra gain stage for red mentioned by @MarshallDog perhaps V2b switched in or out of the path?

    Sorry if the answer's obvious or implied earlier in thread - if so, I didn't get it!
     
  10. SkyMonkey

    SkyMonkey Well-Known Member

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    That is the question!

    This was posted by @MonstersOfTheMidway a while back on the question of JVM410 gain stages:

    JVM 410H_gain stages _2[1].PNG

    Not sure what GAIN ON signifies! And it's in French.
    Now obviously that is a very different amp, with far mode channels and modes. But I suspect that the principles are similar.
    V3 is a common gain tube for all 4 DSL modes as far as I have read, so what stages are used in V3 I don't know.
    I am not proficient enough in electronics to be able to understand the DSL40C schematic.
     
  11. wrees

    wrees New Member

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    I stared at a DSL40C (not CR) schematic from 2011 for a while, and from what my untrained eye could tell, the circuitry associated with the green and red modes looked more like non-tube components that maybe just step down the gain for the green mode and not for the red mode? Is that a possible/likely scenario?
     
  12. SkyMonkey

    SkyMonkey Well-Known Member

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    We need someone like @Micky to clarify. Mickeeeeeyyyy!
     
  13. Micky

    Micky Well-Known Member VIP Member

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    What?
    Clarify what?

    I thought I was pretty clear before when I posted the info about gain stages years ago... (post is from 2012?)

    Classic Clean has one LESS gain stage, which is critical as far as output volume is concerned.
    V1a is the input buffer, which basically matches the guitar input with the amplifier.
    It is then either fed to V2a (Classic Clean) or V1b (Classic Crunch).
    From there it follows the same path as every other mode.
    Again - Classic clean is the ONLY mode (out of 4) that has one less gain stage.
    ( the above chart is misleading, it is from a JVM which has 12 different modes...)

    Classic Clean - V1a->V2a->V2b->V3a->V3b-> Power stage
    Classic Crunch, Ultra 1 & 2 = V1a->V1b->V2a->V2b->V3a->V3b-> Power stage

    That all being said (hope you guys are still following/understanding this...)
    There are MANY other factors that shape / modify / amplify the circuit before it gets to the finals.
    To directly answer the question of 'how does the difference between green and red work for each channel?'
    It is a combination of factors, but it is ALL centered around V1b.
    To put it quite simply, if you take a signal, pass it to the next guy you have the Classic Clean.
    If you take that signal, pass it to a guy who boosts it just a little, you have Classic Crunch.
    If you take that signal, pass it to a guy who boosts it quite a bit, you have Ultra 1.
    If you take that signal pass it to a guy who boosts it quite a bit more, then you have Ultra 2.
    All of this is accomplished by varying the signal level and input resistance to V1b.

    Please remember that V2a&b and V3a&b is exactly the same for ALL modes, it does not change one bit.
    (except for tone shift button)

    This all being said, it has been this way since the invention of tube amps, to a varying degree.
    Some amps are more noticeable than others. Sorry for the long rambling post...
     
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  14. SkyMonkey

    SkyMonkey Well-Known Member

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    Thanks @Micky. I did try to sift through the massive DSL40C thread to find this out, but even with keyword searching I gave up the will to live!

    So it looks like an ECC832 in V1 won't help balance the Classic green and red volumes without bringing them to more or less the same gain too.
    In any other position they will just get lost in the gain cascade, affecting all channels equally.

    I get it now. Cheers Micky.

    I still want to try a lower gain tube (12AY7?) in V2 or V3 to see what changes that would make to the gain difference between OD1 and OD2.
     
    Last edited: Nov 21, 2019
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  15. wrees

    wrees New Member

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    Yes, thanks so much @Micky! I too only found your previous Classic versus Ultra tube flow posts and not anything about green vs. red. I too gave up - so many posts!

    My JJ 823 and 832 should arrive in the next couple days. I'll give them a try and report back!
     
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  16. SkyMonkey

    SkyMonkey Well-Known Member

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    Be aware that gain and volume are different things. You may end up with 2 channels that sound almost the same.
    Look forward to hearing the results. Good luck.
     
  17. wrees

    wrees New Member

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    Got the tubes, did some experiments, got some interesting data. I used a dB meter, a reasonably repeatable signal, and tried Clean, Crunch, OD1, and OD2 with 1. original tubes, 2. 823 in V1, then in V2, and then in V3, and 3. 832 in V1, then in V2, and then in V3. Found a mix of expected and unexpected results. This was not super scientific but enough to convince me (so far) about what's going on.

    Reducing V1a with an 832 in V1 lowered everything a bunch.
    Reducing V1b with an 823 in V1 moderately lowered *only* OD1 and OD2.

    Reducing V2a with an 832 in V2 lowered everything a little.
    Reducing V2b with an 823 in V2 lowered everything a little.

    Reducing V3a with an 832 in V3 lowered everything a bunch.
    Reducing V3b with an 823 in V3 didn't seem to do anything.

    Note: the brand new 832 DIED after I used it in V3. That freaked me out a bit and meant I couldn't do a full second round of tests.

    Taking these results and looking at the DSL40C schematic from 2011 (attached), I'm leaning toward a different analysis than what @Micky proposed. In short, I don't think Classic red goes through V1b, and the difference between Classic green and Classic red is achieved with non-tube components (similarly to how the difference between Ultra green and red are done with non-tube components). I think:

    Classic green: V1a -> (electronics) -> V2a -> V2b -> V3a -> V3b (to drive EQ section?)
    Classic red: V1a -> (electronics) ->V2a -> V2b -> V3a -> V3b (to drive EQ section?)
    Ultra green: V1a -> (electronics) ->V1b -> V2a -> V2b -> V3a -> V3b (to drive EQ section?)
    Ultra red: V1a -> (electronics) ->V1b -> V2a -> V2b -> V3a -> V3b (to drive EQ section?)

    If this is really what's going on, I think it will take an electronics mod to change the difference between Classic green and red.

    But again, I'm not an engineer, so I could be wildly off!
     

    Attached Files:

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  18. SkyMonkey

    SkyMonkey Well-Known Member

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    Pretty thorough stuff. Pity about the 832!
    All that is going into the DSL tube file I have been building. Cheers @wrees.
    I think I will get a 5751 (μ=70) and a 12AY7 (μ=40) to have a play with at some point. Will report when I do.
     

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