'metal' mid-scoop for a DS-1, would this work?...

[kissack101]

Hey, my girlfriend wants me to add a 'scoop' pot onto her modded DS-1 for of a metal tone. I realise through extensive searching that i'm not the only one whos had this idea, and there doesn't seem to be a real answer, but here goes anyway:

If you took this circuit:



and built only what was in the red box, would that work? The relevant link is here: http://www.diystompboxes.com/smfforum/index.php?topic=24359.msg295954#msg295954. Could you ignore the 'bass frequency' and 'treble frequency' parts of the circuit and just build the mids bit? Or would I have to build all three bits and simply hard-wire the other 'pots' via a resistor to a neutral position?

Also, i'm using the assumption that 1kh-1.5kh is about the range I need to be 'scooping', is that accurate? I'm not what you'd call a 'metal' player...

Any help would be much appreciated,

Adam.

[cd]

Referring to this schematic:

http://www.godiksennet.com/images/sch/DS1PG2.jpg

You can probably just replace R16 with a variable pot to kill more highs, which will have the illusion of a mid-scoop.

Play around with Duncan's Tone Stack Simulator (use the Big Muff model) until you hit upon a good sounding curve:

http://www.duncanamps.com/tsc/

[WGTP]

Your girlfriend wants a notch filter, how lucky are you?

I mess with notch filters on my breadboard all the time and now have moved on to the BMP type control using a trim pot.  The problem is, that there are so many variables that you could have hundreds of different notches.  The frequency can be anything from 300 to 3000Hz, the depth of the notch can be from -3db to -30db and the Q can also vary considerably (estimates).  You can even have assymetrical notches.  A simple solution is to get a 7 or 8 band EQ for $20 to bucks that swithces in or out and use it after the DS-1.  A more effective notch EQ can be obtained by using a parametric EQ.  Good luck.   

[kissack101]

Your girlfriend wants a notch filter, how lucky are you?

Well that depends on my ability to build the damn thing!  I was thinking an EQ pedal before it would be an ideal solution, but the pedal was a gift and i'd like to make it 'all in one' if possible. What i guess i'm saying is, I think i'm going to have to compromise somewhere.

Does R16 in the DS-1 correspond to R2 in the Duncan Muff simulation? If so, then you can get a pretty effective scoop from that, although then you still have to worry about where in the frequency range to place it. Maybe I should take my GE-7 over, have her mess around with it and make a note of her favourite setting? Might give me an idea?

Does all this mean that my plan above is doomed to failure?

Adam.

[Mark Hammer]

There is a mid-scoop on the output of the Shin-Ei FY-2 that I adapted to yield a variable scoop: http://img.photobucket.com/albums/v474/mhammer/moddedfy-2.gif
I have been very impressed with the performance of this circuit.  The scoop filter is formed from the 10k/15k/1000pf/.1uf network between the fuzz and volume pots.  The "scoop" pot determines how much of the mids are bled off to ground.  Where the rolloff occurs for the high end that bypasses the scoop is determined by the value of that cap shown as 1000pf.  Higher values get you more upper mids and lower treble.

Note that since this is a passive bleed circuit, more scoop = less signal level.  IN view of the 100k Volume pot on the DS-1, though, the signal loss should be easily compensated for by volume settings.

Just so we're clear here, you can't have the existing tone control circuit and this add-on without suffering a significant passive loss.  Gotta be one or the other.

Okay, with that in hand, here's what you excise from the board:  R15/R16/R17,  C11 and C12 come out too, and while you can re-use the Tone pot, it will need to be rewired.
There are quite likely enough unused slots available once those components have been pulled out, that you can stick in all the ones you need to make the variable midscoop.  Naturally, while you can re-use the Tone pot (not all the the full 50k in what I've shown is really necessary) it will need to be rewired to form a variable resistance to ground.

[kissack101]

There is a mid-scoop on the output of the Shin-Ei FY-2 that I adapted to yield a variable scoop: http://img.photobucket.com/albums/v474/mhammer/moddedfy-2.gif
I have been very impressed with the performance of this circuit.  The scoop filter is formed from the 10k/15k/1000pf/.1uf network between the fuzz and volume pots.  The "scoop" pot determines how much of the mids are bled off to ground.  Where the rolloff occurs for the high end that bypasses the scoop is determined by the value of that cap shown as 1000pf.  Higher values get you more upper mids and lower treble.

Note that since this is a passive bleed circuit, more scoop = less signal level.  IN view of the 100k Volume pot on the DS-1, though, the signal loss should be easily compensated for by volume settings.

Just so we're clear here, you can't have the existing tone control circuit and this add-on without suffering a significant passive loss.  Gotta be one or the other.

Okay, with that in hand, here's what you excise from the board:  R15/R16/R17,  C11 and C12 come out too, and while you can re-use the Tone pot, it will need to be rewired.
There are quite likely enough unused slots available once those components have been pulled out, that you can stick in all the ones you need to make the variable midscoop.  Naturally, while you can re-use the Tone pot (not all the the full 50k in what I've shown is really necessary) it will need to be rewired to form a variable resistance to ground.

Hey,

thanks a lot, the shin-ei looks pretty much what i'm after. I assume because its passive it won't act as a 'boost' as well? Also, how significant is the signal loss likely to be? The volume pot on my ds-1 never goes past 9 o'clock anyway, could I compensate by winding it up? I'd rather keep the existing tone circuit than not (perhaps I could switch between the two?)

Thanks again, this is all very helpful!

Adam

[grapefruit]

I've only got the schematic for the 80's DS1, but the tone control is similar to a big muff tone control. You could use just change the values of the components to get a mis scoop, as in Jack Ormans presence control.

http://www.muzique.com/lab/tone3.htm

You could use Duncans tone stack calculator to work out the scoop.
The DS1 already had a little dip. If you change C11 to 4.7n youll get a much bigger scoop at 1kHz. You can vary this by putting a pot and resistor in series with R17

[WGTP]

http://aronnelson.com/gallery/WGTP/BassBoostNotch

Here is what Mark is referring to and what I use on my breadboard.  It could easily be switched in and out.  The deeper the notch, the more signal lose there is.  Try a 1-10K resistor, .01uf and .047uf caps and 10 and 22K resistors for a pretty good size notch.  Sockets will allow for experimentation.   

[michael_ibrahim]

As opposed to connecting the .022uF cap directly to ground, to get a variable mid cut, connect it though a suitable pot. Ty A25k, or A50k, configured as a variable resistor. Obviously, you'd need to vary the values of the caps in order to get more scoop. Basically, to get more scoop, decrease the value of the top cap, and increase the value of the bottom cap.

Just note that this is a lossy circuit, so you'll loose more output volume with it. If I recall correctly, the DS1 is already rather quiet.

[Mark Hammer]

It IS a lossy circuit, though not painfully so.  I implemented two different versions of it on my original FY-2 and a clone of it.  On the original, I simply bypassed the scoop network with a DPDT toggle, and replaced the entire network with a 39k fixed resistor in "bypass" mode to yield an approximate volume balance between the scoop and no-scoop settings.  Not perfect, but close enough for rock and roll.  On the other, I eschewed a bypass switch and used a 50k pot because I had lots lying around.  Quite frankly, you probably don't need more than maybe 20k of resistance (the value of the existing tone pot) to make a big difference in scoop depth. 

Alternatively, the Tone pot can be used as a variable resistor in series with the bypass cap (.001uf in the original scoop design) to adjust the treble level.  So, a person could have a somewhat larger bypass cap value (e.g., .0033uf) in series with the Tone pot, AND a full bypass toggle (as described above).  The user could get a no-cut "flat" setting, and a scoop-with-variable-sizzle setting, necessitating only a single hole popped into the chassis for a toggle.

Note that the tone control on the Foxx Tone Machine does a bit of this.  The tone circuit is essentially the same type of 2-cap/2-resistor scoop filter, with a pot set up BMP-style between the bypass cap and the second resistor.  Rotated to one side, it presents no series resistance to the bypass cap, but a larger series resistance on the other path.  Rotate it the other way and the bypass cap gets a resistance tacked on at the end, while the other path has its post-cap resistance dropped.  Not the MOST effective tone control in the world, but it works, and sets a reasonable precedent for what I suggested.

If output level is an issue, try a Keeley-style "seeing eye" mod by replacing one or both of the diodes with a red LED.  That will diminish the amount of distortion a bit, but give a little more dynamics and noticeably greater output level.  A serious midscoop will help to offset the loss of distortion amount by an increase in the "sick and evil" factor - midscoops will do that .  That could be a kickass pedal.  Ready for a girlfriend who gets more people asking her about her gear than you do?

[kissack101]

Ready for a girlfriend who gets more people asking her about her gear than you do?

LOL! It's the only pedal she's got at the mo', i was so sick of looking at her Korg multi-effect thingy that I HAD to do something! Thanks a lot for everything though, I think i'll tack the FY-2 scoop onto the end (do I put it BEFORE the output cap?) with a DPDT switch to pull it in and out. The pedal already has LEDs in the clipping stage so I don't think volume loss will be a problem, and it means another cool toggle switch for the pedal! Needless to say, i'll keep you all posted with how I get on!

Thanks again  ,

Adam.

[Mark Hammer]

The scoop thing will go in between the point where C9/C10 meet and the input to the Volume pot. You can wire up the toggle almost exactly as you would a true bypass stompswitch, although as suggested earlier you probably want to replace a "straight wire feedthrough" on the bypass side with a fixed resistor.  Something in the vicinity of 39k will probably come pretty close. 

Note that 39k in series with the input to the 100k Volume pot makes the vol pot act like it is a 139k pot turned down 1/3 of the way when set to max volume.  If the volume imbalance is unsettling or uneven, use a higher value resistor (e.g.,43k or 47k) if the noscoop setting is too loud, and a lower value (e.g., 33k or 36k) if it isn't loud enough.

Given the large volume of DS-1 owners and modders (aren't they one in the same?  ), see if you can get a soundclip to post.  I'm sure others will be interested.

[TheBigMan]

I'd certainly be interested.  I've been toying with adding a switchable clipping section into my DS-1.  Currently I've got a pair of 1N34As in there and whilst the sound is great there's not a lot of level.  I was thinking of adding an option for assymetrical 1N914/LED and the 1N34As with a simple volume recovery stage tacked in between the tone and volume controls.  Adding a mid scoop as well would make the pedal really versatile.

[kissack101]

The scoop thing will go in between the point where C9/C10 meet and the input to the Volume pot. You can wire up the toggle almost exactly as you would a true bypass stompswitch, although as suggested earlier you probably want to replace a "straight wire feedthrough" on the bypass side with a fixed resistor.  Something in the vicinity of 39k will probably come pretty close. 

Right, i've finally got round to this after a couple of weeks doing other things. I've wired it up but predictably, no signal is coming through the pedal, even when the pedal is 'off'. In terms of where i'm wiring it, I have a wire coming from the leg of C9 that connects to C10 into the 'input' of the FY-2 scoop circuit, and a wire going from the output of this to the volume pot (after the output from the tone control).

Is this right? Or do I need to cut a trace somewhere and just splice the scoop into the circuit somewhere? Any help would be much appreciated, i'll be sure to write all this up once i've got the damn thing working!

Adam.

[Mark Hammer]

From your description, you've done the correct bit of wiring, but from your experience it sounds like your description may be inaccurate!

Let's start slow, then.  Unsolder/lift the ends of C11/R16 that connect to C9/C10, plus either end of R17 and C12.  This will assure that the existing tone network is completely removed from the circuit.   From that C9/C10 junction, run a straight wire to the input lug of the volume pot.   You will now have whatis essentially an "untamed" DS-1, where the clipping output goes immediately and directly to the volume pot without any tonal shaping whatsoever.  If THAT works, then we have verification that you have isolated the appropriate parts without doing damage.

What I had suggested to you before was an attempt to re-use as much as possible of the existing traces and on-board components as possible.  It does not NEED to be done that way, however; at least not at first.  Once you have confirmed that your tone-bypass works, with the board and everything still out of the chassis, substitute a perfed midscoop filter (fixed) for the straight wire bypass.  This will have an in, out, and ground wire that will be tied to Vref.  That will verify that the scoop indeed sounds the way you want it to.

Once you have THAT part done, wire up the pot of your choice as a variable resistor between the ground cap and Vref on the midscoop, and confirm that the variable scoop is also to your liking.  Make some notes about what the resistance value of the pot is at that points where you start to notice useful changes, as well as where it tends to produce no further audible change.  Those measurements can be used to adjust the taper of the pot or the amount of series resistance you set as maximum.

Once you have all of THAT confirmed, now it's time to figure out how to use the available component spaces on the board to install your new (and hopefully aesthetically pleasing) midscoop.

[kissack101]

Hey,

Thanks a lot for the reply, i'll work on all this tonight. Just to me clear: I was hoping for a solution that allowed me (her?) to use the existing tone control AND have the mid-scoop control as well. The scoop circuit itself is on a small sqaure of perf-board lodged in the cavity between the chasis and the existing PCB (properly insulated so that it doesn't short or anything). Is it possible to have 'both' tone controls (signal loss aside)?. As I (thought I) understood it, the 'new' tone section seemed to 'straddle' the existing one but the more I thought about that the less I thought it should work. On the diagram for the FY-2 the scoop seems to be just tagged on the end, and I thought this might be possible here, though my intuition the fact that the DS-1 isn't true bypass will mean its not that staight-forward.

I'll do as you suggest in the meantime Mr Hammer and let everyone know how I got on. Hopefully I can get this cracked, it seems like something a lot of folk might be interested in.

Thanks again,

Adam.

[Mark Hammer]

Trying to incorporate BOTH the existing and additional tone-shaping will likely eat up too much signal, yielding an unsatisfyingly low output level.  You can likely get away with a midscoop and some supplementary treble cut since that doesn't rob too much overall amplitude, but applying significant attenuation in the zone where the body of the notes live is asking for trouble.

[Elektrojänis]

On the other hand... If it gives you more signal than you really need with the existing tone control, you might get away whith both of them. I'd say try it.

If the volume gets too low you could add some kind of a booster in there. I prefer fet-boosters myself but others should work too.