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  1. #1

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    just got a 50w 1x12 holland lil jimi. It's a great amp but while it shares the topology of the AB763 fender, it seems to be voiced more like a marshall in terms of treble response. Not crazy about the shift control and I end up having the presence and treble at 1 or 2 and it's still brighter and thinner on the higher strings than my '68 bandmaster reverb with the treble on 6 (running through the same speaker cabs). I'm considering disconnecting the presence and shift controls. I'm a big fan of the basic amp sound just being "right" and not having a ton of wide ranging modifying controls.


    Can some recommend which value caps / resistors I would want to change to voice it a bit more like a fender?

    I'd be willing to pay someone to walk me through this with a diagram...



    Can someone help me get a holland lil jimi to sound more like a fender?-holland-jpg

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  3. #2

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    Well without the schematic it's difficult to tell ( that's just the layout diagram) but for a start, the tone stack has Marshall value 0.02 caps, so not the AB763 topology. Maybe the fact it's called a lil Jimmy is a clue? It's impossible to tell much from just the layout diagram; the sweep control looks like a variable slope control maybe. Marshalls and AB circuits have very different slope
    resistances in their tonestacks, presumably that's the idea behind 'sweep'...can't see a shift control. So many factors affect the sound, it's hard to say much more.
    But all amps can be revoiced to sound differently, you need the schematic if you want to convert it to the AB topology. And as you know, the speakers have a lot to do with how it sounds..

    I'd be careful about disconnecting the presence control, it's part of the negative feedback loop. Suggest just setting it to minimum.

  4. #3

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    something else to consider..altho the diagram ^ shows 2 5881 power tubes, the lil jimi is designed to be able to take 6v6 and 6l6 power tubes as well (with re-biasing)...check what your power tubes are

    using lower watt 6v6 will get you more fender deluxe crunch...6l6's will give you increased headroom and a bit of fendery scoop

    cheers

  5. #4
    Quote Originally Posted by neatomic
    something else to consider..altho the diagram ^ shows 2 5881 power tubes, the lil jimi is designed to be able to take 6v6 and 6l6 power tubes as well (with re-biasing)...check what your power tubes are

    using lower watt 6v6 will get you more fender deluxe crunch...6l6's will give you increased headroom and a bit of fendery scoop

    cheers
    This one has got over 450v on the plates. 6V6 won't work. They made a couple different versions. I currently have tungsol (reissue) 6L6-STR in it.

  6. #5

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    I did a quick comparison between and an AB763 schematic and your layout. It looks like several resisters in the negative feedback circuit are different (highlighted in yellow). I think besides adding a the presence pot in place of the 100 ohm resistor, the amount of negative feedback was reduced.

    The tone stack (highlighted in orange) looks a lot different, incorporating a sweep control, I guess to alter the effects of the mid control.



    To get back to AB763 voicing, I think you’ve need to draw a schematic of these part of the layout, compare them to an AB763 schematic, and rewire per AB763.

    Here’s an AB763 schematic with the presence and EQ circuits highlighted.



    That would disable the presence and sweep controls. You can add a presence control to the AB763 circuit and could repurpose the sweep pot. I’ve been impressed with Rob Robinette’s site, and he’s got goo page on AB763 mods.
    AB763 Mods

    Here’s the Twin Reverb schematic I looked at.
    https://schematicheaven.net/fenderam...b763_schem.pdf

  7. #6

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    A couple more thoughts:

    -if you wanted to try a quick and dirty AB value substitution, and can work on tube amps safely, you could try changing a few components in the tone stack to AB values on a temporary basis.

    1)....from the components inside your layout orange line boundary, locate the .02 cap at bottom right ( one end attached to a 100k resistor), remove and replace with a 0.1uf 600 ( ideally) or 450 v poly cap. The 0.1 cap will not attenuate bass frequencies. It's a temporary 'bridge' to avoid rewiring the whole thing to AB specs, and to avoid relocating the 250p cap to another node on the board, the leads probably won't be long enough.
    2) .....locate the two .02 caps joined together at one end, in layout lower middle. Replace the upper cap with 0.047uf and the lower cap with 0.1uf poly caps.
    3).....disconnect the two wires to the sweep control at the respective junctions with the 56k resistor and the 250pf cap, and tape them off. You can reinstall if you don't like the change
    4).....leave the 56k R in place, now with one end un-attached to the sweep control, and solder a 100k 1 watt resistor to the junction of the 250pf cap, the unattached 56k resistor and the new 0.1 uf 600/450v cap you already installed in step 1. The other end goes to the junction of the .047 and the 0.1 caps you have already installed in step 2

    Disclaimer - if this doesn't make sense to you, please ignore the suggestion!!! One bad solder joint could make things worse, I don't know how used you are to working on amps. Obviously all electrical safety precautions apply. Take it a tech., who if competent will know how to rewire these things.

    Worth mentioning that the presence control appears unconventionally wired. The older Fender circuits have the presence controls in parallel with a fixed tail resistor ( the value has to be calcultaed according to the negative feedback applied, and the value varies. Typical AB circuits don't have presence controls at all.) This design appears to make the presence pot a variable tail resistor. This could be a bad idea, because if the pot gets dirty or wears out, or has bad contact with the chassis, and is the sole route to ground for the phase inverter current, the amp will become intermittent or even cut out. The old Fender way ( eg in the 5E circuits) is safer, and if the presence cap is placed before the presence pot in the circuit, you don't get dc voltage on the pot.

    These changes won't necessarily get the changes you are looking for - other factors are important- but might indicate whether it's worth persisting with modding the amp. If you like the changes, then the step 1 cap can be taken out and the wiring fully configured for AB763. This will probably involve replacing your 250pf cap with a new new 250pf cap, as your existing one won't reach the new required lug on the board.

    Again, if these changes don't fully make sense when you look at your layout, please ignore this and take it to a tech.

  8. #7

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    Errrr, Jack, why not just get a 6L6-based Fender amp that sounds like a 6L6-based Fender amp? The Gries 36 is a good one...

  9. #8
    Thanks so much Franz! I'll take a hard look at that later today. I greatly appreciate it!

  10. #9
    Quote Originally Posted by Jabberwocky
    Errrr, Jack, why not just get a 6L6-based Fender amp that sounds like a 6L6-based Fender amp? The Gries 36 is a good one...
    For a number of reasons.

    • I got the holland for $800. No way I'm going to get something comparable, hand wired for that price.
    • The gries is great but way less power, no longer manufactured and i've literally been looking for one for over a year.
      • I used to have a gries 35 and loved it but I sold it locally to a jazz and blues player and it didn't have enough headroom for him. He now uses a Dr. Z-Lux which is a 44w amp. Much more headroom. I'd love to use one of those but don't really like the tone. Too much bottom and low mids and Dr. Z was unwilling to customize it.

    • fender never made a single 12", 50w amp except maybe the Concert and it's also not really an AB763 amp.

  11. #10

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  12. #11
    Quote Originally Posted by medblues
    The problem with the dr z amps for jazzers is that they are voiced more for blues guys and all have a ton of bass and low mids. The zluxe and ezg50 both have this issue so they'd both have to be modified in much the same way as the holland though probably a bit less so.

    And also $2400 is a lot more than the $800 I have invested in the holland. The holland is actually a great platform. It has a heyboer 2/4/8 super reverb OT, a powerful PT which can put 450+ volts on the plates, choke, reverb transformer, etc.

  13. #12

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    Quote Originally Posted by jzucker
    The problem with the dr z amps for jazzers is that they are voiced more for blues guys and all have a ton of bass and low mids. The zluxe and ezg50 both have this issue so they'd both have to be modified in much the same way as the holland though probably a bit less so.

    And also $2400 is a lot more than the $800 I have invested in the holland. The holland is actually a great platform. It has a heyboer 2/4/8 super reverb OT, a powerful PT which can put 450+ volts on the plates, choke, reverb transformer, etc.
    Yeah sorry I realized the pricing mistake after I initially posted. Never played a Z-Lux but when I was shopping for a high headroom louder amp, Eddie's guitars told me EZG-50 was the only suitable one among Dr.Z models and I liked the head they had I don't remember the cab they used. Eventually, I ended up with a Fender George Benson HRD and a Carr Rambler and completed my tube amp journey.

  14. #13

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    Quote Originally Posted by jzucker
    For a number of reasons.

    • I got the holland for $800. No way I'm going to get something comparable, hand wired for that price.
    • The gries is great but way less power, no longer manufactured and i've literally been looking for one for over a year.
      • I used to have a gries 35 and loved it but I sold it locally to a jazz and blues player and it didn't have enough headroom for him. He now uses a Dr. Z-Lux which is a 44w amp. Much more headroom. I'd love to use one of those but don't really like the tone. Too much bottom and low mids and Dr. Z was unwilling to customize it.

    • fender never made a single 12", 50w amp except maybe the Concert and it's also not really an AB763 amp.
    According the site, Gries is making the Gries 36 now—current manufacture. I just bought a 5 watt head from him—he’s definitely in business. New at $1300 seems like a great deal.

  15. #14
    Quote Originally Posted by wzpgsr
    According the site, Gries is making the Gries 36 now—current manufacture. I just bought a 5 watt head from him—he’s definitely in business. New at $1300 seems like a great deal.
    completely different amp. Doesn't have reverb. And as I mentioned before, it works well for quieter gigs but needs a bit more headroom for louder ones.

  16. #15

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    Just about any silver-face Deluxe you can find is going to be closer to AB763 than that. It isn't even a 6V6 amp.

  17. #16
    Quote Originally Posted by icr
    Just about any silver-face Deluxe you can find is going to be closer to AB763 than that. It isn't even a 6V6 amp.
    ab763 is not just a nomenclature for deluxe reverbs. There is an AB763 twin reverb for example. Deluxe doesn't have enough headroom.

  18. #17

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    Quote Originally Posted by jzucker
    ab763 is not just a nomenclature for deluxe reverbs. There is an AB763 twin reverb for example. Deluxe doesn't have enough headroom.
    Yes, good point. So you want the headroom offered by the higher output.
    You make a lot of videos, how about one with the amp as it sounds now.

  19. #18
    Quote Originally Posted by icr
    Yes, good point. So you want the headroom offered by the higher output.
    You make a lot of videos, how about one with the amp as it sounds now.
    I just shipped it to a repairman today to repair and and perform some mods. A few days ago, it started fading out to about 25% volume, then would come back for a while and then fade again. Yesterday it blew a fuse. I reached out to guy guy I bought it from on reverb but because it was more than 7 days, they will not do anything. So anyway, the repairman (Jim Jorewiky) makes amps, has a great reputation and blackfaced a friend of mine's allen encore which sounds superb so I figured I'd have him fix it and blackface it for me while he has it. Unfortunately, I couldn't find anyone in cleveland to do the repair so the cost of shipping both ways will add $150 to the repair cost!