Haze 15 question

Discussion in 'The Workbench' started by black knight, Sep 21, 2019.

  1. black knight

    black knight Member

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    Greetings,

    I just got a Haze 15 head and I like it pretty much stock, with one exception, the bright switch discrepancy between the normal and overdrive channels. It sounds great clean without the bright switch engaged, but a bit too dark when switching over to the OD channel. I've read all about the mods for the 40 and 15 on this and other forums. Initially at least, I want to leave it stock with one minor modification - bypass the resistor that leaves the bright switch always engaged while on the OD channel. I've read that the resistor on the 40 is R77. My question is what resistor is the equivalent on the 15? I couldn't find a definitive answer anywhere. Viewing the schematics, it appears to me that R77 on the 40 is R58 on the 15. Is this correct? Has anyone done this on their 15 head? If so, does the amp retain all its goodness?

    Before I go whole hog with mods, I wanted to try this first. Again, I really like the amp as is. I'm not sure I want to turn it into a fire breathing 220_. Love those amps for what they are but this little 6V6 beast has it's own charm.

    Any help is most appreciated.

    Steve

    https://www.thetubestore.com/lib/thetubestore/schematics/Marshall/Marshall-Haze-MHZ40C-Schematic.pdf

    https://www.thetubestore.com/lib/thetubestore/schematics/Marshall/Marshall-Haze-MHZ15-Schematic.pdf
     
  2. Gunner64

    Gunner64 Well-Known Member Premium Member

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    I don't know about the resistor, but I did clip one leg of if I remember c59, which took out most of the muddiness in the od channel, closer to 800 territory..and oh yea..try clean boosting the front end if you havent already. Really tightens it up even more. i have the full Haze stack, and was considering getting one of the new sc20 mini 800s, because they are the same size as my haze cabs, and I love 800s..but after clipping that cap in my haze, and clean boosting it it pretty much sounds like an little 800, so I'm not sure I'd gain anything hetting the sc20. Plus the haze is 2 channel with very usable effects. Great little overlooked amps imo.
     
    Last edited: Sep 22, 2019
  3. South Park

    South Park Well-Known Member

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    It looks like r 59 to me.it might a drop down resister.
     
  4. mickeydg5

    mickeydg5 Well-Known Member VIP Member

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    First off the Haze15 preamp does not exactly resembly the Haze40 preamp so you should re-evaluate the approach.

    The bright switch circuit in the Haze15 OD Gain when OFF dumps the high frequencies. You can change C49 C71 to a lower value.

    Changing R58 to a low value just annunciates the other side of the switch which kind of renders the switch more usless.
    That is a dumb idea not being a good approach to changing the voicing.
     
    Last edited: Sep 22, 2019
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  5. South Park

    South Park Well-Known Member

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    Yes good call c49 and c71 need to changed out.too many switches
     
  6. Gunner64

    Gunner64 Well-Known Member Premium Member

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    Just clip one leg of c59 ( not r59) on the od channel vol pot, seems to bring the treble on the od channel closer to the clean channel.
     
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  7. Micky

    Micky Well-Known Member VIP Member

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    I never realized the bright switch doesn't work on the Ultra Channel...

    I'll have to try that...
     
  8. mickeydg5

    mickeydg5 Well-Known Member VIP Member

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    The C59 removal modifiction is a good call too. It is doing the same as those other capacitors, dumping high frequency to ground. C59 is dumping highs right at/before the Overdrive Volume potentiometer.
     
  9. black knight

    black knight Member

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    Thanks guys for taking the time. I admit that I'm far from a tech so this information is valuable to me.

    Gunner64, I agree totally. Great little amps and I will try this suggestion. In your estimation, did the character of the overdrive sound very similar or virtually identical to the stock sound with the bright switch engaged? I ask because I really dig the amp stock with the switch engaged and was hoping to retain that tone.

    mickeydg5, thanks. I am a noob so bear with me. The other threads I read on this topic include having the bright switch "engaged" at all times when on the OD channel which to my simple, logical mind, would make the amp perfect. Clean tone is great without it, OD is great with it. Guess it is not that simple so thanks. Out of curiosity, what exactly does R77 do on the 40?

    Micky, my apologies. I don't understand. What do you mean?
     
  10. Micky

    Micky Well-Known Member VIP Member

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    This statement is what I am referring to...
     
  11. mickeydg5

    mickeydg5 Well-Known Member VIP Member

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    There is no need to leave the BRIGHT switch ON all the time. You stated liking the NORMAL channel without it and the OVERDRIVE channel with it.
    The thing is with this amplifier there should have been two seperate switches, one for each channel.

    My thinking was to keep the switch options intact but change the non-bright situation on the OVERDRIVE channel to keep more highs.
    However I have a feeling you want more mids.
    You like the BRIGHT situation of the OVERDRIVE channel which uses a 1nF/100k series resonant circuit.
    That is going to give more upper mids.

    R58 of Haze15 does the same job as R77 of Haze40. The 2.2M resistor is there to avoid switch bounce click/noise. And yes if it is shorted or made a small value that part of the circuit will always play a major part of signal path which renders the swithing there more or less useless but it will leave that part of the circuit engaged as you said.

    Here is another idea if you would like to keep the swithing intact since it may be found the switching could be beneficial with different setups and volume levels. The real bright capacitor for the OVERDRIVE channel is C58. It is only 47pF. Marshall's normal values there are more like 1000pF and 5000pF. Try larger values there (piggyback or parallel to the 47pF if possible) to get more midrange roar in the OVERDRIVE channel. Test with alligator test leads first if possible to find a value you like.
     
  12. mickeydg5

    mickeydg5 Well-Known Member VIP Member

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    I think the word ultra is what threw him. There is no ULTRA on a Haze15, is there? :hmm:
     
    Last edited: Sep 22, 2019
  13. black knight

    black knight Member

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    Micky, I realize my poor choice of wording in my original post. I should have said "bypass or short the resistor which would have the effect of the bright switch being permanently engaged on the overdrive channel." Also, yes the word ultra added to my confusion. In any case, this is my understanding of what would happen if a jumper wire was used across R58 based on what I read in other threads on the topic. (Actually R77 on the Haze 40).

    I am rethinking things now after mickeydg5's recommendations.

    Thanks mickeydg5 for the explanation of what's actually happening when the switch is engaged. I suppose you are right in that it's more mids that I was wanting since I like how it sounds with the bright switch engaged. I will try your OD channel bright cap suggestion and perhaps, with the switching function left intact, I may get two useful sounds out of it. Anyway, thanks for the insight.
     
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  14. Gunner64

    Gunner64 Well-Known Member Premium Member

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    I found with mine after clipping C59 that the od channels treble response increased to where it was pretty close to the normal channels treble response. That is with the bright switch engaged. Before clipping c59 I found the od channel a bit bassy, and muddy..now it's much more crisp and crunchy to my ears..clean boost the front end with a ts9 and it becomes very 2203/04 ish.

    This is through the stock a and b haze 1x12 cabs with the stock Marquee speakers
     
  15. Micky

    Micky Well-Known Member VIP Member

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    I guess I've been using DSL's so long the channel names have stuck... Sorry.
    I haven't played the Haze 15 in a long time, it sits on top of a full stack of cabs and seemingly collects a bit of dust. Actually I have it covered with a padded moving blanket.

    I DO remember using the bright switch a bit differently than you all, I have the bright switch on for my LP's, and off for my Strats and Teles. Seems to balance the single-coil versus humbucker EQ, especially with the cabs I have. I never had a problem with muddy OD channel, except for the tone control on a couple guitars.
     
  16. mickeydg5

    mickeydg5 Well-Known Member VIP Member

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    That brings up another issue or option. Make sure you have a nice strong 12AX7/ECC83 type in V1 position. A dull tube could weaken the signal diminishing some of that upper roar. Try or rotate several in that position to see how the preamp reacts.
     
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