Boss SD-1 questions

[Mark Hammer]

As a synth player, you must be excited about Behringer's announcement of all the Eurorack Roland and Moog modules they'll be producing at bargain basement prices.

And, as a synth player, I suppose the de-fizzing feedback cap that the TS-9 has but the SD-1 lacks, is not something you'd be inclined to add.  In which case, I think the suggested lowering, or even removal, of C6 may well be more than sufficient.  Again, remember that C4/R7 is but a humble single-pole lowpass, so there will be plenty of harmonic content remaining.  You may want to have a look at Jack Orman's ideas for tinkering with the TS-9 style Tone control, to see if it can bring you closer to the functionality you need.  http://www.muzique.com/lab/tstone.htm

[snk]

I made the veroboard, traces and cut, and put the resistors, electrolytics and all the sockets. I need to wire the pots and jack sockets, and let you know about my experiments.

I suppose the de-fizzing feedback cap that the TS-9 has but the SD-1 lacks, is not something you'd be inclined to add.  In which case, I think the suggested lowering, or even removal, of C6 may well be more than sufficient.

I will try this first, before messing with C4/R7. I'm planning to try a 1nF and a 10nF on a switch.

You may want to have a look at Jack Orman's ideas for tinkering with the TS-9 style Tone control, to see if it can bring you closer to the functionality you need.

Thank you ! I didn't know this page from Jack Orman, I will look at it.

As a synth player, you must be excited about Behringer's announcement of all the Eurorack Roland and Moog modules they'll be producing at bargain basement prices.

The Roland System 100 is a bit of a unicorn synth : something you never see in your real life but would like to try. So i would be lying if i'd say i am not interested in it Also, the modules are compact, well featured, and many are two-in-one, which is great when you're lacking space in your case.
But i am not really a supporter of Behringer's policy (no R&D, only cheap copies, sueing forumers and Dave Smith, etc), so I would say i am even more interested into Dreadbox's new and affordable line of modules, as well as other forward-thinking, innovative and smaller companies.
Imho, Korg's remake of Arp is like a tribute (it even keep the brand name), while Behringer seems to be flooding the market with mass-recreation of just about every synth in just a couple months timeframe (The Octave Cat is very rare so i can understand that, but the MS20 and some others are still produced by their original creators)...

[Mark Hammer]

There are certainly reasons to look askance at Behringer, but they have provided a service to many by making rare birds available to the masses, as well as subsidizing the reissuing of obsolete chips we couldn't live without.  I look forward to the return of '70s and '80s synth tones, with a 21st century sensibility.

I've seen the demos of the Dreadbox stuff and it looks like big heaps of cost-effective fun.  I've been stockpiling home-built MFOS and Tom Gamble modules for a while, and also acquired a Roland Torcido module a little while back, and a MIDI-2-CV box for my Casio MG-510 MIDI Strat, so I may be set.  Somewhat like a miniature version of the Empress Zoia Euroburo, the Roland Aira modules allow for virtual patching of up to 6 virtual modules, in combination with externally-supplied CV sources and audio signals.  It's a neat system.  https://www.roland.com/ca/products/aira_modular_customizer/

[snk]

There are certainly reasons to look askance at Behringer, but they have provided a service to many by making rare birds available to the masses, as well as subsidizing the reissuing of obsolete chips we couldn't live without.  I look forward to the return of '70s and '80s synth tones, with a 21st century sensibility

Yes, I hear you, and i agree. It's good to be able to afford a synth/pedal/mixer without breaking the bank, and be able to play an instrument which was previously made of unobtainium.

About the topic of the SD-1 : I built it, and it works 
I have compared my build (using stock values on sockets) and the original one, and it sounds nearly identical. The new version is a bit "sharper" and sounds a tad louder, but apart from that it's the same.
Then, I tried some mods, and I really thank you all for your help, because I think I have really found what i was after : the sonic palette of the pedal is really expanded.
With C3 and C6 on a switch, it can sound "vintage", or more modern with an increased bandwidth suiting any kind of electronic instrument.
I tweaked C4 a little bit : used in conjunction with the C6 switch, it's really great to shape the tone at will.
I didn't even feel the need to try tweaking C5/R8.
I lowered the minimum gain, so i can get a very transparent tone, with just some added grit on top, which i like.
The pedal became much, much versatile imho

Now, I am playing with diodes, and hesitating between 3X1N4148 (like stock), 3X red leds, or 2 red leds in a symetrical fashion...
1N4148 sound quite warmer, while leds sound more "open", but depending on the gain setting, it is not a night & day difference.

[snk]

Hi, I'd have one more practical question :
I can't figure out an easy way to have 3 caps on a toggle switch 
I wouldn't want to use a rotary 3p4t, so, would I need to use capacitors in series like picture below ?
(I wish i could just use the values i am aiming for -47nF, 100nF, 220nF-, instead of getting roughly 110nF by connecting in series 2 x 220nF on a switch).

[Mark Hammer]

What I like to do is have 2 caps in series.  The common of the toggle goes to the junction of the two caps, and the outside lugs of the toggle go to the "far end" of the caps.  So, for example, if I had a 220nf and 100nf cap in series, their effective capacitance in series would be just under 69nf.  Bridge the 220nf with the toggle (side position) and the capacitance goes up to 100nf.  Bridge the 100nf cap and the capacitance is now 220nf.  The tricky part is finding cap values that achieve the sort of proportional shift in range one wants.  The shift from 100 to 220nf is larger than that from 69 to 100nf.   Using a 150nf and 100nf cap gets you 60nf, 100nf and 150nf.  Not a perfectly proportional shift, but closer.

[Rob Strand]

It's possible to get more flexibility with a parallel connection but you need another cap.
You have a permanently connected cap and then switch two others in parallel.

Suppose we call the external connections A and B:
- Connect all caps to A
- Connect the smallest cap, C1,  to the switch center lug, this is connection point B
- Connect the next size cap C2 to one of the outside lugs.
- Connect the largest cap C3 to the other outer lug

C1 = 47n, C2 = 47n, C3 = 150n
up: is C1 in parallel with C2 = 47n + 47n = 94n
centre off:  C1 only = 47n
down:  C1 in parallel with C3 = 47n + 150n = 197n

The series method Mark mentioned is easy to wire-up and is most economical in terms of caps.

The only thing you gain with the parallel method is a bit more flexibility.  You can add 10M across the outer switch lugs to point B to reduce switching clicks but it adds more clutter to the circuit.

I'm not advocating one method over the other.   Both these methods have the issue that the centre position is the smallest cap so the switch position has the highest cut-off at the centre not the up position.

[snk]

Ok, thank you both.
What I usually don't like with caps in series is that you can't read the actual value from one single cap (you have to make some maths to know the value used by the circuit), which make servicing & tweaking less intuitive... but i might be lazy

Isn't my layout posted above correct ?
It seems that using two 220nF and one 68nF wired that way, we would get :
- center position = 220nF
- up position = 220+220=> 110nF
- down position = 220+68nF => 52nF

[willienillie]

Your center position is open.  I agree with Rob, wire your smallest desired value in permanently, then switch (two) other caps in parallel to make larger total values.  You might not have any popping issues.  It might depend on which end of the caps you're switching.

[rankot]

He can always parallel 1M resistors with those caps, so it will reduce popping.

[snk]

Your center position is open.

The center position would be 220nF, right ?
And then upper position 220nF + 220nF in series, which should give 110nF, and lower position 220nF+68nF in series, which should give 52nF. Isn't that correct ?


With a picture it's better, i'm a visual guy
Following Rob's suggestion, the nice thing is that putting capacitors in parallel is easier to find their added value
This would be like that, right ?

[willienillie]

The center position would be 220nF, right ?

No, assuming we're talking about a standard on-off-on DPDT, there would be no connection between the middle lugs in the center "off" position, no signal flow, open.  The upper and lower "on" positions would work as you expect.

Your new parallel diagram would work fine.

You might not have any popping issues.  It might depend on which end of the caps you're switching.

I should have been more detailed and clear.  With the parallel idea you can also use a SPDT on-off-on if you prefer, with one end of the added caps hard wired, and the other end switched.

crappy MSPaint diagram:

[Rob Strand]

This would be like that, right ?\

No, assuming we're talking about a standard on-off-on DPDT, there would be no connection between the middle lugs in the center "off" position, no signal flow, open.  The upper and lower "on" positions would work as you expect.

His drawing looks OK to me for an DPDT.  He's just using the centre contacts as  solder points for permanently wired caps.
The switch just parallels the selected cap across the permanent cap.    Centre position correct connects the permanent cap.

The way I outlined it before used an SPDT switch but the DPDT can also be used for convenient wiring.

[willienillie]

We're talking about two different drawings.  His initial series DPDT drawing would be left open in the center position.  His parallel DPDT drawing would work fine, though might pop when switching.

[Rob Strand]

We're talking about two different drawings. 

Sorry, that's my fault.  Your drawing *is* the SPDT version.

[snk]

Sorry, that's my fault.

Mine, too : i wrote my earlier post with a bag of on/on/on SPDT in front of me, and didn't realized that my DPDT were not like my SPDT 
Now everything makes perfect sense, sorry about the confusion (i made a DPDT layout with the SPDT behaviour in mind, and mixed/messed everything up).

One last thing : I can have both pedals (the old Boss and the "clone") sound identical, but the Boss is much louder. Is there any way to increase the output level on the "clone" without changing the overall sound ?

[rankot]

One last thing : I can have both pedals (the old Boss and the "clone") sound identical, but the Boss is much louder. Is there any way to increase the output level on the "clone" without changing the overall sound ?

There must be some difference between them! Compare and find.

[Rob Strand]

Are you sure the pot tapers on the clone are the same as the original.   That would mean the same pot positions aren't actually the same pot settings.

[snk]

Hi,
I played again with both units : i can confirm that my built is roughly 6dB more silent than the vintage one.
- When I put each on an AUX of my mixer, and putting their output on a dedicated mixer track, i have to adjust one track fader by -6dB to match the levels.
- If i make a side by side comparison (not using a mixer aux), i have to put the OUT pot of the vintage one at half course (while the fresh build is maxed) to match their levels.

This 6dB difference is roughly what i had when i swapped the 1N4148 y red leds for testing purposes (The red Leds were louder, but not as "round" and "warm" on the bass range as the 1N4148, so put the diodes back).

I made the test not by matching the knob's position, but by matching the sound by ear (and using original component values on my build). The sound is matched, but not the output level. It is not a very big deal (i get at unity gain), but I wish I could also match the output level.

I am sure that I am using the same pot value and taper as the original schematic (10K log).
Should I try a bigger value for the out pot (like 100K) ?

[Rob Strand]

i can confirm that my built is roughly 6dB more silent than the vintage one.

6dB is a lot.  Highly unlikely to get 6dB if the units are truly built the same.
It's quite a simple circuit so there isn't much opportunity for such a problem to creep in.

I'd be carefully comparing the each part value in the two units.
If that doesn't find anything check all DC voltages.
If that doesn't find anything  I'd be thinking something is faulty!