smallsound/bigsound - mini  [traced]

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smallsound/bigsound - mini

Postby bubstance » 06 Jul 2016, 15:37

Some preliminary gutshots to get things rolling. They're not the best, but it's what I can do at this precise moment. I only have the pedal for another day or two, so ask all the questions you can.

http://s44.photobucket.com/user/bubstan ... oads/story

Q1= 2N5089
Q2= J201
Q3= 2N5457
Q4= J201
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Re: smallsound/bigsound mini  [traced]

Postby smallsnd/bigsnd » 06 Jul 2016, 19:45

i got u. even cleaned up the schematic from the original so it's easier to read... :hug:

Image

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Re: smallsound/bigsound mini

Postby bubstance » 06 Jul 2016, 21:36

Damn, Brian, you really are the actual fucking man, aren't you? :hug:

So what's going on in the "high gain/scramble/octave" mod on these? I've seen you offer up info for the DIY inclined, but never had a mini to look at for comparison.
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Re: smallsound/bigsound mini

Postby smallsnd/bigsnd » 06 Jul 2016, 21:47

bubstance wrote:Damn, Brian, you really are the actual fucking man, aren't you? :hug:

So what's going on in the "high gain/scramble/octave" mod on these? I've seen you offer up info for the DIY inclined, but never had a mini to look at for comparison.


nah just figured i'd save everyone some time.
uuuh let me get back about the scramble mod - i have it written down at my shop and i'm not there at the moment.
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Re: smallsound/bigsound mini

Postby destro » 07 Jul 2016, 18:51

YES!! This is awesome. Thanks, Brian. Christmas in July!!
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Re: smallsound/bigsound mini

Postby smallsnd/bigsnd » 07 Jul 2016, 20:12

destro wrote:YES!! This is awesome. Thanks, Brian. Christmas in July!!


:cheers

maybe i should make up a PCB for DIY folks?
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Re: smallsound/bigsound mini

Postby karter2000 » 07 Jul 2016, 22:22

smallsnd/bigsnd wrote:
destro wrote:YES!! This is awesome. Thanks, Brian. Christmas in July!!


:cheers

maybe i should make up a PCB for DIY folks?


Count me in for one. Thanks a bunch for the schematic!
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Re: smallsound/bigsound mini

Postby destro » 08 Jul 2016, 15:30

smallsnd/bigsnd wrote:
destro wrote:YES!! This is awesome. Thanks, Brian. Christmas in July!!


:cheers

maybe i should make up a PCB for DIY folks?


:scratch: :hmmm: .... it's a trick. Get an axe.
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Re: smallsound/bigsound mini

Postby bubstance » 09 Jul 2016, 12:01

smallsnd/bigsnd wrote:
destro wrote:YES!! This is awesome. Thanks, Brian. Christmas in July!!


:cheers

maybe i should make up a PCB for DIY folks?


Hell yeah. I'd buy several.
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Re: smallsound/bigsound mini

Postby maortojn » 09 Jul 2016, 16:20

smallsnd/bigsnd wrote:
destro wrote:YES!! This is awesome. Thanks, Brian. Christmas in July!!


:cheers

maybe i should make up a PCB for DIY folks?


Really cool to post the schematic, and I would definitely be up for a pcb.
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Re: smallsound/bigsound mini

Postby smallsnd/bigsnd » 10 Jul 2016, 04:04

alright, sounds like there is interest. i'll get on it this week. the layout i use is a little weird so i'd rather make something new that's more DIY-friendly. i can make one with 2 PCB mounted pots like the way i already do it - then you wire 3 off-board pots. in my experience, a 125B is the best choice for size vs overall ease of build.

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Re: smallsound/bigsound mini

Postby 287m » 10 Jul 2016, 13:40

hello
the gain pots is dual gang pots?
and what criteria for jfet?
thanks :thumbsup
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Re: smallsound/bigsound mini

Postby hozy31 » 10 Jul 2016, 16:10

Verified a vero layout of this on Guitar FX layouts posted by Anders in the contributions section. Awesome overdrive. Thanks Brian for the schematic.
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Re: smallsound/bigsound mini

Postby smallsnd/bigsnd » 11 Jul 2016, 17:06

hozy31 wrote:Verified a vero layout of this on Guitar FX layouts posted by Anders in the contributions section. Awesome overdrive. Thanks Brian for the schematic.


cool! oh sorry there is one small error in the schematic which is important - BIAS in the schematic is a 10k TRIMPOT.
the actual BIAS control that is panel-mounted should connect the wiper to the intersection of the drain of Q3/C4 and lug 1 to pin 1 of the 10k trim. sorry about that! you might want to update the vero. i'll update the schematic in a few minutes.

also - i use J201 for Q2 and Q4, 2N5457 for Q3.

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Re: smallsound/bigsound mini

Postby storyboardist » 12 Jul 2016, 18:35

Thanks Brian for sharing with us! Here's a perf and PCB layout for those interested. All pots can be board mounted and you might be able to squeeze it into a 1590B (though I agree with Brian, 125Bs are best).

Image
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Re: smallsound/bigsound mini

Postby EBRAddict » 12 Jul 2016, 18:58

I'd socket the drain and source resistors, measure the component values and pick the values based on what 2N5457 I have. The 2N5457 has a 0.5-6V Vgs swing and Idss is 1-5mA. You'd grow old and/or broke trying to find the right through-hole JFET. My experience with SMD JFETs is they are fairly uniform so picking through them is not very productive.
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Re: smallsound/bigsound mini

Postby smallsnd/bigsnd » 13 Jul 2016, 05:47

storyboardist wrote:Thanks Brian for sharing with us! Here's a perf and PCB layout for those interested. All pots can be board mounted and you might be able to squeeze it into a 1590B (though I agree with Brian, 125Bs are best).


nice!

EBRAddict wrote:I'd socket the drain and source resistors, measure the component values and pick the values based on what 2N5457 I have. The 2N5457 has a 0.5-6V Vgs swing and Idss is 1-5mA. You'd grow old and/or broke trying to find the right through-hole JFET. My experience with SMD JFETs is they are fairly uniform so picking through them is not very productive.


that's what the trimpots are there for although you won't go broke or old if you handpick... i select all three JFETs for each pedal using a little test rig and it only takes a few minutes. ymmv though of course.
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Re: smallsound/bigsound mini

Postby johnk » 13 Jul 2016, 07:59

I etched and built up storyboardist's PCB and it works great so it's verified.
what bias voltage are we looking for on the Jfet's.
I have an original 125B MINI but i'd prefer not to take it apart to measure them since the legs on them are so short.

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Re: smallsound/bigsound mini

Postby smallsnd/bigsnd » 13 Jul 2016, 15:48

johnk wrote:I etched and built up storyboardist's PCB and it works great so it's verified.
what bias voltage are we looking for on the Jfet's.
I have an original 125B MINI but i'd prefer not to take it apart to measure them since the legs on them are so short.


cool! yeah it's a simple little build so it shouldn't be too difficult for anyone.
now that i think about it for Q2 i actually choose the transistor for a resistance value in my test build so that the range of the bias is correct.
for voltages, i like:
Q1 - 5.1V +/- .2V
Q2 - i go for approximately half supply at noon on the bias knob.
Q3 - 4.5-4.7V

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Re: smallsound/bigsound mini

Postby johnk » 13 Jul 2016, 22:01

thanks!
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