Boss - LMB-3 Bass Limiter  [schematic]

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mothbox
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Post by mothbox »

I'm interested in modding my LMB-3 with the Steve McKinley Thunder mod. Wondered if anyone has tried it and knows what it actually is.

I can't afford to send my pedal half way around the world to get this mod done so want to do it myself, but I can't find any information on what the actual changes are.

Anybody got any idea?

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Dirk_Hendrik
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Post by Dirk_Hendrik »

No response in 7 hrs... That's not too much.

So, what happened?!
Steve McKinley seemingly is onto something with his Thunder mod. He's onto thatso well that nobody even dared to figure out what he did figure out! Or, It's that damn good people are willing to pay Steve McKinley real money for his Thunder mod!!! The fact that you cannot afford it too simply says you do not want it that bad enough.

OK, here's the plan?
- You, Mothbox, have a little patience and work hard till you get the money together to get Steve McKinley to mod your pedal.
- You get your pedal modded by Steve McKinley and pay the guy accordingly.
- You recieve your pedal back from Steve Mc Etc. and be a sole judge on wether his work is worth the money.
- You determine what Steve exactly did change and post it here or on any guitar related forum so anyone else is able to do the same.
- You feel proud that you were among those who opted to get information you paid real money for into the open source domain which does not give you anything in return, other than an occasional "thanks".

Anything in the above that does not fit your perspective Mothbox? Than seemingly this mod is not really that valueable to you. :blackeye
Sorry. Plain out of planes.

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roseblood11
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Post by roseblood11 »

different approach:

- find a schematic or draw one. (LMB-2 is in this thread: https://www.freestompboxes.org/viewtopic.php?f=1&t=8735 )
- understand how the circuit works
- find the mods that work best for you

mothbox
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Post by mothbox »

Dirk_Hendrik wrote:OK, here's the plan?
- You, Mothbox, have a little patience and work hard till you get the money together to get Steve McKinley to mod your pedal.
- You get your pedal modded by Steve McKinley and pay the guy accordingly.
- You recieve your pedal back from Steve Mc Etc. and be a sole judge on wether his work is worth the money.
If I was based in the US I would pay for the mod. But posting it from China and back again plus the cost of the mod and the cost of the original pedal I'm coming close to what I'd pay for a Diamond Comp, and I picked up the LMB-3 on a budget to begin to experiment with compressors.

I'm tempted to email Steve and request to pay for the mod schematic. The Thunder mod removes a lot of the issues I have with the pedal such as the noise on the enhance knob and some "popping" on certain settings. I'm not trying to do the bloke out of cash by asking if anyone knows what the mod actually is.

As for figuring it out off the back of the original schematic, the engineers at Boss seemed to fail to remove the noise so I'm not sure that I'll be unable to correct the problems in their design! My knowledge of circuitry is limited at best! The things I want to change are the issues with noise in the circuit and not adding features.

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Post by tube-exorcist »

Oh yeah...... China..... I understand....

The only problem is that I haven´t seen a schematic of an original unit yet, and.....

.....I havent seen any guts (except one with only a burned transistor):
https://www.diystompboxes.com/smfforum/ ... ic=99955.0

But obviously you have an original and working pedal:
mothbox wrote: .... I picked up the LMB-3 on a budget .....
Now you have to find only someone with a digital camera. Take some nice pictures of the insides of the pedal and post these pictures here. I think that your chances will then increase dramatically.
"I've noticed there's an inverse relationship between cost of gear and talent. If you need the most expensive gear to get decent tones, then you suck as a player."

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Post by roseblood11 »


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Dirk_Hendrik
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Post by Dirk_Hendrik »

And another one bit the dust? :lol:
Sorry. Plain out of planes.

http://www.dirk-hendrik.com

mothbox
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Post by mothbox »

Work in progress.

I want to use the unaltered pedal through a jam-room system and also get some DI recording done with it in the loop to see if the artifacts are present in the recordings and if its a specific range within the settings where they appear.

The enhance knob needs altered though. I'm surprised with the amount of noise it adds that Boss released the pedal.

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Post by Dirk_Hendrik »

I'm surprised about the absence of the suggested photo's. Might help a lot to speed this topic up. :D
Sorry. Plain out of planes.

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Rocket Roll
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Post by Rocket Roll »

OK, here's a couple of pictures.
Attachments
Boss LMB-3 (9).jpg
Boss LMB-3 (8).jpg
Boss LMB-3 (7).jpg
Boss LMB-3 (6).jpg
Boss LMB-3 (5).jpg
Boss LMB-3 (3).jpg
Boss LMB-3 (2).jpg

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Rocket Roll
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Post by Rocket Roll »

...and one more.
Some of the values:
R 55, 560 R
C1, 10uF
IC5, NJM45(58LO)
IC4, NJM3404AL
IC3, NJM4558LO
IC2, THAT 21810
IC1, NJM455(8LO)
C23, 100uF
C22, 47uF
C24, 47uF
C18, 1uF
C12, 1uF
C9, 1uF
C10, 1uF
C40, 2n2
C11, 1uF
C27, 10uF
C26, 10uF
C28, 1uF
C29, 22n
C7, 47n
C8, 1uF
C35, 47n
C33, 10uF
C34, 47n
C32, 1uF
C31, 10uF

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Rocket Roll
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Post by Rocket Roll »

Sorry, forgot to post a picture, and I cannot edit previous post.
Attachments
Boss LMB-3 (10).jpg

george giblet
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Post by george giblet »

Hi All, I've just about got this thing traced. However there's a few thing missing from the photos (posted above) and I was wondering if someone can help me out so we can finally put this one to rest.

I've attached a pic showing all the missing stuff.

Thanks!
Attachments
LMB-3 missing parts 2019_03_02j.jpg

george giblet
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Post by george giblet »

OK here's the trace. This is *not* the original schematic. In order to see the difference between the LMB-3 and the LM-2B I've marked-up the LM-2B schematic. The blue parts show the parts of the ckt which are different between the LMB-3 and the LM-2B.

Red dots mark areas which need to be verified.

FYI:
The wholenote blm-270 limiter,
http://www.freestompboxes.org/viewtopic.php?f=1&t=18385
uses a different VCA chip and maybe a few different value resistors around the VCA. Different opamps. Note also the enhance caps are 1n2 instead of 1n on the LMB-3.

The Behringer BLE-100 uses a different VGA and maybe a few different value resistors around the VCA. Different opamps (TL064).

From the parts of the circuits I traced of these in detail both are very similar to the LMB-3.

The FET switching circuits are likely to be different.
Attachments
Boss LMB-3 sch dwgV10.png

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