Author Topic: Bass Behemoth + JMK mini Engineer's Thumb  (Read 4766 times)

thesameage

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Bass Behemoth + JMK mini Engineer's Thumb
« on: March 17, 2015, 07:24:56 AM »



Been wanting to try out a bass klon for a while now and when Rej made an offer in a thread for a populated version of his Bass Behemoth, I jumped on it. Around that time I had also collected a PPP orange sparkle enclosure and a pop'd JMK mini Engineer's thumb board from BYOC (missed getting one from JMK over the holidays). I just came off a bad time of trying to build a circuit of Midway Fair's that he designed for me that is in my fail box. Before hitting that one again, I thought I'd do an "easy" assembly pedal. Well, nothing is every easy!  :) I did get this one working, though.

I'm a bass player and have wanted a really basic, functional, utility pedal for a while now. Something that can do light grit, but can get fuzzy if need be AND incorporates a comp. Kind of a grab and go bass pedal. The circuit that Jon developed (that I couldn't get working from above) is the same idea as this pedal, but kind of a Bearhug/Green Russian Muff mashup put through the innovative approach that he uses for all of his projects. This is a different flavor of that and I'll be interested to see how they compare. This is a quad opamp take on the Klon with germanium diodes and a jfet boost that "only" works when the OD is engaged, which caused some complications in troubleshooting.

I have only been able to try this one out on my crappy bench amp, so I'll have to see how it sounds out loud on the stack. But so far, the engineer's thumb is really nice. Very smooth and full range with amazing sustain if you need it. It does color the sound a little bit, but I like it so far. The klon clone side is great so far as well. Allows for some nice boosted tone without losing low end-- kind of does what a klon should. I like the added grit, but will need some real speakers to test out what it sounds boosted. I like it so far. When the boost is engaged, the OD can get a little harsh (not as smooth and warm as I would like), but again, this needs some dialing in. Also, with these kinds of pedals and bass (as most of you know): when played at home, a nice warm fuzz generally seems to get lost in the mix with a band. Something that is slightly harsher sounding seems to actually sound better in a band mix, so I think it's going to be great.

One thing: When I max out the pot for the engineer's thumb, it abruptly cuts the signal in about the last 1/16th of the rotation. Any ideas on why that might be?

Luke51411

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Re: Bass Behemoth + JMK mini Engineer's Thumb
« Reply #1 on: March 17, 2015, 07:30:32 AM »
Nice build! Great work.
I built the mini engineers thumb and it didn't cut out like yours does. I have no other input as to why just that the one I build doesn't do that.

thesameage

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Re: Bass Behemoth + JMK mini Engineer's Thumb
« Reply #2 on: March 17, 2015, 07:37:44 AM »
Maybe it's just a dodgy pot. I don't really need to crank the comp anyway, so it's kind of moot.

A few things: I added the Led's at the last minute, so that wiring needs some work. Also, made the mistake of using superglue to put the led's in the lenses-- the superglue dripped and made the lenses a bit cloudy. Will have to be more careful on that end next time. Probably could have spaced the footswitches out better as well. This is more of a tone pedal and the only stomp I'll stomp on the fly is the boost, so that's fine too. As always, it's a learning process, but this one came together fairly well. Learned a bunch!

playpunk

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Re: Bass Behemoth + JMK mini Engineer's Thumb
« Reply #3 on: March 17, 2015, 07:41:27 AM »
Looks great! That enclosure is so tasty.... :)
"my legend grows" - playpunk

Luke51411

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Re: Bass Behemoth + JMK mini Engineer's Thumb
« Reply #4 on: March 17, 2015, 07:41:59 AM »
Maybe it's just a dodgy pot. I don't really need to crank the comp anyway, so it's kind of moot.

A few things: I added the Led's at the last minute, so that wiring needs some work. Also, made the mistake of using superglue to put the led's in the lenses-- the superglue dripped and made the lenses a bit cloudy. Will have to be more careful on that end next time. Probably could have spaced the footswitches out better as well. This is more of a tone pedal and the only stomp I'll stomp on the fly is the boost, so that's fine too. As always, it's a learning process, but this one came together fairly well. Learned a bunch!
Did you put the super glue on the LED before putting them in the hole? I usually put them in place first and then just dab it around the edges. That seems to work pretty well for me.

thesameage

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Re: Bass Behemoth + JMK mini Engineer's Thumb
« Reply #5 on: March 17, 2015, 07:45:13 AM »
Maybe it's just a dodgy pot. I don't really need to crank the comp anyway, so it's kind of moot.

A few things: I added the Led's at the last minute, so that wiring needs some work. Also, made the mistake of using superglue to put the led's in the lenses-- the superglue dripped and made the lenses a bit cloudy. Will have to be more careful on that end next time. Probably could have spaced the footswitches out better as well. This is more of a tone pedal and the only stomp I'll stomp on the fly is the boost, so that's fine too. As always, it's a learning process, but this one came together fairly well. Learned a bunch!
Did you put the super glue on the LED before putting them in the hole? I usually put them in place first and then just dab it around the edges. That seems to work pretty well for me.

I think I put it on before... should have wedged the LED in and then dabbed it. I also just got some super glue gel this weekend which would also have prevented that problem. It's minor, though. I wanted a diffused look-- I really got it! Also, when I drilled the holes for the lenses, I took a small ring of paint off right where the rings are. Any ideas on how to prevent that? I drilled everything through painter's tape to prevent chipping and to mark the spots, but had to do finally finishing on those holes without it.

thesameage

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Re: Bass Behemoth + JMK mini Engineer's Thumb
« Reply #6 on: March 17, 2015, 07:47:10 AM »
Looks great! That enclosure is so tasty.... :)

Ha ha... thanks again for sending it my way! Never would have picked that color, but now that I see it in person it's awesome.

Luke51411

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Re: Bass Behemoth + JMK mini Engineer's Thumb
« Reply #7 on: March 17, 2015, 07:56:13 AM »
Maybe it's just a dodgy pot. I don't really need to crank the comp anyway, so it's kind of moot.

A few things: I added the Led's at the last minute, so that wiring needs some work. Also, made the mistake of using superglue to put the led's in the lenses-- the superglue dripped and made the lenses a bit cloudy. Will have to be more careful on that end next time. Probably could have spaced the footswitches out better as well. This is more of a tone pedal and the only stomp I'll stomp on the fly is the boost, so that's fine too. As always, it's a learning process, but this one came together fairly well. Learned a bunch!
Did you put the super glue on the LED before putting them in the hole? I usually put them in place first and then just dab it around the edges. That seems to work pretty well for me.

I think I put it on before... should have wedged the LED in and then dabbed it. I also just got some super glue gel this weekend which would also have prevented that problem. It's minor, though. I wanted a diffused look-- I really got it! Also, when I drilled the holes for the lenses, I took a small ring of paint off right where the rings are. Any ideas on how to prevent that? I drilled everything through painter's tape to prevent chipping and to mark the spots, but had to do finally finishing on those holes without it.
I'm not sure on the paint ring, did you use a regular bit or a unibit? On occasion I've drilled from the inside of the box to try to avoid dinging a finish but I'm not sure how well it actually worked.

thesameage

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Re: Bass Behemoth + JMK mini Engineer's Thumb
« Reply #8 on: March 17, 2015, 07:57:05 AM »
I used a stepped bit.

TGP39

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Re: Bass Behemoth + JMK mini Engineer's Thumb
« Reply #9 on: March 17, 2015, 06:12:32 PM »
Really nice work JR. That mini engineer's comp looks like a nutter to populate. Where did you find those tiny 3pdt daughter boards? I like them.

Steve.
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thesameage

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Re: Bass Behemoth + JMK mini Engineer's Thumb
« Reply #10 on: March 18, 2015, 11:58:04 AM »
Thanks Steve,

Those 3dpt boards are ones that Rej makes specially for some of his pcbs. That said, you can find similar ones here: https://aionelectronics.com/project/micro-3pdt-bypass/

JR

thesameage

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Re: Bass Behemoth + JMK mini Engineer's Thumb
« Reply #11 on: March 19, 2015, 06:57:05 AM »
Posted about this in the open forum, but thought I'd post here as well. Finally tested it out at band practice last night and I get a pretty audible hum when everything is off. What should I do? I think that the culprit might be the power cable runs. The power jack is on the back and does a long run to the mini-compressor, and then there's another long run back to the back of the bass klon. Can I just connect everything to the jack? Or do I have to chain it like that? Here's a another pic of the insides. Thanks in advance for any suggestions: