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DIYstompboxes.com  |  DIY Stompboxes  |  Building your own stompbox  |  Is there a contour knob mod for BSIAB2? 0 Members and 1 Guest are viewing this topic. « previous next »
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Author Topic: Is there a contour knob mod for BSIAB2?  (Read 3445 times)
mth5044
Posts: 1850

Matt


Is there a contour knob mod for BSIAB2?
« on: February 21, 2009, 02:16:08 PM »

The one thread that is one this site about the mod links to a GGG page that shows how to build a talkbox  Roll Eyes  Tongue

Is there anywhere else that shows how to put in the contour knob? I can't seem to come up with anything and it sounds like a worthwhile mod.

Thanks  Smiley
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John Lyons
Posts: 5733


Basic Audio


WWW
Re: Is there a contour knob mod for BSIAB2?
« Reply #1 on: February 21, 2009, 02:45:46 PM »

Never heard of one....by that description at least.

john


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Basic Audio Pedals
www.basicaudio.net/
mth5044
Posts: 1850

Matt


Re: Is there a contour knob mod for BSIAB2?
« Reply #2 on: February 21, 2009, 02:58:16 PM »

Hmmm... maybe it's just the AMZ body control.

here is a picture of one with the contour



I read somewhere that JD on GGG had done up a kit or a prebuilt pedal with 4 knobs, but I guess that was a while ago. The description I've found around the web says its a mids knob, which sounds like the AMZ presence control on the website.

Hrm.
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liquids
Posts: 1020


Matthew


Re: Is there a contour knob mod for BSIAB2?
« Reply #3 on: February 21, 2009, 06:20:52 PM »

Far as I can tell from asking JD, and experimenting with the circuit, the 'contour' knob was a variable resistor to ground off of the "Big Muff" style tone stack - 'replacing' R8. It definitely borrows from Jack's tweaking ideas here, the 'body' or 'presence' control  http://www.muzique.com/misc/presence.pdf, the latter name I do find a misnomer, but it is what it is.  Smiley

This is a very useful mod for some.  I like the 'full mids' with the stock 82Kish range on the BSIAB, including 56K, 100k, etc.  As the designer Ed notes himself, most amps are already designed and/or EQ's for mid scoop...so scooping more mids is not necessarily a good idea.  Many people find the stock Big Muff Tone stack with a lower resistor (I'll throw 22k out there) which scoops the mids a fair amount means things get lost in a live setting,  YMMV.  Mid scoop is good in moderation rather than excess for most tones...but it depends on what you want, the rest of the circuit, etc.

When the BSIAB or anything gets that gainy, things naturally sounds brighter and chunky on the low end, downplaying mids (meaning it seems more mid-scooped).  The full, VH hot-rodded marshall type mids into the inevitably mid-scooped, set-bright fender amp are what it the pedal was designed around, also, bear in mind.   I like the midrange girth the circuit has even with lower gain settings.  So I personally would not want to scoop much more mids...but in theory, it's a great option, and can make it sound 'heavier' and/or more 'modern;' forgive the cliches.  Likewise with really low gain, being able to dial down the mids could give you more perceived clarity for bluesy single notes and neck pickups, etc. 

Try breadboarding it with a various resistor values (82K, 56K, 47K, 33k, 22K, 10K, 4k etc) and see how you feel about it, or what range of values you find usable.  Or, you can just make it a 100K pot, drill the hole, be done with it...my question is...if you go with the 100K pot, should it be linear or audio taper?  My gut and bad memory say audio taper, but you gotta use your own ears.   Smiley
« Last Edit: February 21, 2009, 06:23:13 PM by liquids » Logged

Breadboard it!
mth5044
Posts: 1850

Matt


Re: Is there a contour knob mod for BSIAB2?
« Reply #4 on: February 21, 2009, 07:20:10 PM »

Thanks for the explaination. I really appreciate it. You make a good point about the already scooped mid sound, I hadn't thought about that.

But you say it was designed to go into a bright fender amp.. that worries me a bit. If it goes into a single channel 'clean' marshall amp, its not going to sound as good?
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John Lyons
Posts: 5733


Basic Audio


WWW
Re: Is there a contour knob mod for BSIAB2?
« Reply #5 on: February 22, 2009, 01:06:37 AM »

The Magic of the AMZ presence control is the ability to bring back the mids with the big muff tone control
which has a mid scoop with the tone knob in the center position.

The BSIAB is pretty flat in the mids as it is. It does have a smooth hump in the low end though.
With the mid knob I think you would only be able to cut the mids which isn't what you want to do with the
BSIAB as it's generally considered a "dark" sounding circuit...or at least not bright and midrangy...

Check out the other big muff modifications at AMZ though because there is another one that has the ability to boost the
mids and that would be a cool thing with the BSIAB.

john

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Basic Audio Pedals
www.basicaudio.net/
liquids
Posts: 1020


Matthew


Re: Is there a contour knob mod for BSIAB2?
« Reply #6 on: February 22, 2009, 01:38:45 PM »

Thanks for the explaination. I really appreciate it. You make a good point about the already scooped mid sound, I hadn't thought about that.

But you say it was designed to go into a bright fender amp.. that worries me a bit. If it goes into a single channel 'clean' marshall amp, its not going to sound as good?
It was designed running single coils into a blackface-fender style amp set with the bass low and the bright switch on, etc, trying to get an early VH type sound.  Most people who are not running that type of setup/EQ hence find the circuit---really the tone stack and filter section--dark. 

But It's easy to mod it out of darkness to taste, once you know what you think of it stock.  It's been discussed here a lot.  Remove C13 and or C14.  Or replace one or both with smaller values (for example .001's instead of .0022uFs for a  less high end roll of).  And/or change C10 to a smaller value - I like .0047uF, for example, to make the tone knob more of a 'sheen' controlling only the highest treble (if you mod C8 to 1uF so the tone stack has little to no bass roll off, that is). These are just simple ways to 're-voice' the filters if your not running bright pickups into such a bright amp.

Really, have no fear.  the BSIAB is an incredibly versatile, responsive, tweakable circuit, the likes of which most stock production overdrive/distortion pedals can't compare to.  It's no one trick pony.  Try it, see how you feel about it, and we'll help you mod it to your tastes from there.   Smiley
« Last Edit: February 22, 2009, 01:55:10 PM by liquids » Logged

Breadboard it!
liquids
Posts: 1020


Matthew


Re: Is there a contour knob mod for BSIAB2?
« Reply #7 on: March 16, 2009, 07:09:31 AM »

Correction - I was looking at my BSIAB and rehousing it this weekend and noticed something.

AS per the GGG schematic, while I imagine a pot to control R8 would be a more interesting control for some, I think the contour control was actually in place of R7 on the board.  This would control the 'corner' (I believe) frequency of the high end roll off. The stock tone control is pretty dark.  There's other ways to go about this, but this is an option.
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Breadboard it!
naz
Posts: 1


Re: Is there a contour knob mod for BSIAB2?
« Reply #8 on: May 01, 2009, 07:26:04 AM »

Hi all - my first day here and glad to be. Does anyone have any results to report on the contour mod?

I'm looking to boost the mids/low mids to move the pedal more toward ZZ top and a away from the JCM 800 sound. Looks like the AMZ contour mod puts the pot in place of R8, but I have also seen mentioned here and suggested on other forums on R7. Also, Jack Orman changes all of the other resistor/cap values in his AMZ tone circuit (contour) mod. Anyone implement these mods and have thoughts? Does it give you more of a Billy Gibbons sound? thanks
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caspercody
Posts: 560

Rob Schneider


Re: Is there a contour knob mod for BSIAB2?
« Reply #9 on: July 15, 2009, 11:26:05 PM »

I read in another forum that wamplers Pinnacle pedal is the BSIAB mu-amp setup into a Big Muff style tone control, into a variable twin t type filter for mid control (contour), and than into a jfet to volume.

I would love to try this on my BSIAB. So alittle help.. It is easy to find a schematic for the Big Muff tone, but waht is the variable twin t filter? Is this similar to what you are talking about with the AMZ presence control? And the jfet booster is easy to find in here.

Any help would be great!

thanks
Rob
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sandmannn69
Posts: 2


Re: Is there a contour knob mod for BSIAB2?
« Reply #10 on: July 28, 2009, 02:19:39 PM »

I read in another forum that wamplers Pinnacle pedal is the BSIAB mu-amp setup into a Big Muff style tone control, into a variable twin t type filter for mid control (contour), and than into a jfet to volume.

I would love to try this on my BSIAB. So alittle help.. It is easy to find a schematic for the Big Muff tone, but waht is the variable twin t filter? Is this similar to what you are talking about with the AMZ presence control? And the jfet booster is easy to find in here.

Any help would be great!

thanks
Rob

Rob I am actually in the process of modding my BSIAB 2 into a Pinnacle (waiting for Mouser to send parts). Let me know if you need info about the changes.
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caspercody
Posts: 560

Rob Schneider


Re: Is there a contour knob mod for BSIAB2?
« Reply #11 on: July 28, 2009, 02:51:17 PM »

Yes please!!! I am wanting to make a Pinnacle, but not sure exactly what to do.

I have collected some information on this, and have been waiting to talk (or write) to someone who is trying the same.

Please send any info you have, and if you would like  can send you what I have. I have been waiting to place an order with Mouser till I have a good idea what to do.
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sandmannn69
Posts: 2


Re: Is there a contour knob mod for BSIAB2?
« Reply #12 on: July 28, 2009, 05:20:46 PM »

Caspercody,

Sent you a PM.
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