Challenge: Onboard Octavia Action for Bass Sound

[CheshireCat]

Okay, here's a bit of challenge that I'm up against, and maybe you guys can help.

I want to be able to play bass lines on my Utah, like two-handed stuff, or even thickening up various chords and so on, and had the idea of creating a 2 pole (or perhaps 3) pickup for the low E and A strings (possibly D) and then running that thru an onboard Super Octave circuit, kinda like Boss's Super Octave pedal.

Now, I know there is a way to do it passively as a doubler, where I go one octave higher, and it's pretty simple, small, and unobtrusive at that. But a halfer? That's the challenge!

Does anyone have any ideas? Know of any analog pedals out there from way back when that I could sort of pillage and copy?

Also, this needs to be able to run from a 9-volt battery. The Boss pedal works only off of DC and needs an external power supply, but, then again, it has all sorts of onboard preamping and other stuff that I wouldn't need, and isn't just a simple circuit.

Now, btw, to answer your question, yes, I imagine I could do this with MIDI, and in fact will have MIDI onboard as it is. But considering that there is probably some simple way of doing this that I haven't quite put my finger on, and it will presumably require a minimal amount of wood, I would much rather handle it passively (if that's the right word) and onboard, and save the MIDI for other things. Also, this would mean that I could play out anywhere and have bass available to me without needing a MIDI hook-up and/or rig.

Any ideas? Wolf?

Chesh

[CheshireCat]

Any ideas guys? Wolf?

[bam]

I don't go into hardcore electronics, but maybe you can locate a schematic for that pedal and rip off its octaver circuit.. ?

[CheshireCat]

bam said:

I don't go into hardcore electronics, but maybe you can locate a schematic for that pedal and rip off its octaver circuit.. ?

I was toying with that idea. Anyone know where I might find such a schematic? I know it is possible, and no doubt probably doable with only a 9-volt battery to work with, vs. DC.

Any ideas?

Chesh

[JohnH]

Just for interest, heres what may be a fairly dreadful idea, from my days as a teenage electronics nerd in the '70s. This could be made out of probably 4 transistors:

signal from 'bass' pickup goes to:
passive treble cut filter to smooth it out to as near a pure sine wave as possible, goes to:
a level control, goes to:
high gain preamp to convert it, by clipping, to a square wave, dependent on the level control, goes to:
a frequency divider, made from two transistors, to halve the frequency, goes to:
some more passive or active treble cut filtering to control and smooth out the signal, goes to
volume control to mix it with the real signal

This would not be expensive, but you'd definately want to mock it up outside of a guitar first to see if it sounds any good. Unlike modern digital ways of sampling and changing frequency, which preserve the tonal nature, this would be a pure bass fuzz sound.

[CheshireCat]

johnh said:

Just for interest, heres what may be a fairly dreadful idea, from my days as a teenage electronics nerd in the '70s. This could be made out of probably 4 transistors:

signal from 'bass' pickup goes to:
passive treble cut filter to smooth it out to as near a pure sine wave as possible, goes to:
a level control, goes to:
high gain preamp to convert it, by clipping, to a square wave, dependent on the level control, goes to:
a frequency divider, made from two transistors, to halve the frequency, goes to:
some more passive or active treble cut filtering to control and smooth out the signal, goes to
volume control to mix it with the real signal

This would not be expensive, but you'd definately want to mock it up outside of a guitar first to see if it sounds any good. Unlike modern digital ways of sampling and changing frequency, which preserve the tonal nature, this would be a pure bass fuzz sound.

Well, hey, for some $5 to $10 worth of electronics, plus some preamping (I already have some EQ circuitry), pure bass fuzz might just be what the doctor ordered. The bit of octavia circuitry floating somewhere in the Boss Super Bass schematic is still on the table, so until I can work that out, what you've described sounds very promising, at least in moving the project along.

Also, a fuzzy, synthy sound might be pretty cool. As long as it sounds palletable and bassy, that's the key thing right now.

I'm not that versant in regular electronics. What exactly would that look like and what would I need to get?

And thanks!!! This represents a major breakthru!!!!

Chesh

[JohnH]

Im going to try to mock something up by stealing my sons electronics kit. No promises though - its an idea from a long time ago and I'm out of practice! It might take a few days but Ill let you know.

[CheshireCat]

johnh said:

Im going to try to mock something up by stealing my sons electronics kit. No promises though - its an idea from a long time ago and I'm out of practice! It might take a few days but Ill let you know.

Excellent!!

I'm definitely looking forward to that!

Tell ya what: is it also possible to sketch something out real quick and then post a pic? That way I could get working on it too. At least a thumbnail sketch to work with.


Chesh

[JohnH]

OK Chesh, at the risk of posting something stupid, here is a half baked circuit. Im nervous because I know there are some real electronics people in here.:

people.smartchat.net.au/~l_jhewitt/circuits/fuzzdivider.gif

I rigged this up today and it basically works - it took 5 transistors though. Q1 and Q2, are from a 'fuzzface' circuit., to drive the input signal to clipping. The real version of this has the 1k resitor with a capacitor on the central connection, taken to ground, to control the fuzz. as shown its at max fuzz. The signal from this part of the circuit is actually quite good, if you want an extreme fuzz.

Q3 forms a switch, based on the output of Q2. This drives Q4 and Q5 which are a 'toggle bistable'. This changes state with each pulse, dividing the frequency at the output by two.

As shown, the component values are not optimised, nor are there any mixing controls or eq included. It just makes a very loud deep farting noise. I found it works much better with a single note that with two or more strings going, at which it gets a bit confused. The transistors are all NPN, small signal types, anything should do. Mine have a gain of arond 220, but this is probably not critical

Im not sure if this will lead anywhere, but it was fun to try!

cheers

John

[CheshireCat]

johnh said:

OK Chesh, at the risk of posting something stupid, here is a half baked circuit. Im nervous because I know there are some real electronics people in here.:

people.smartchat.net.au/~l_jhewitt/circuits/fuzzdivider.gif

I rigged this up today and it basically works - it took 5 transistors though. Q1 and Q2, are from a 'fuzzface' circuit., to drive the input signal to clipping. The real version of this has the 1k resitor with a capacitor on the central connection, taken to ground, to control the fuzz. as shown its at max fuzz. The signal from this part of the circuit is actually quite good, if you want an extreme fuzz.

Q3 forms a switch, based on the output of Q2. This drives Q4 and Q5 which are a 'toggle bistable'. This changes state with each pulse, dividing the frequency at the output by two.

As shown, the component values are not optimised, nor are there any mixing controls or eq included. It just makes a very loud deep farting noise. I found it works much better with a single note that with two or more strings going, at which it gets a bit confused. The transistors are all NPN, small signal types, anything should do. Mine have a gain of arond 220, but this is probably not critical

Im not sure if this will lead anywhere, but it was fun to try!

cheers

John

Excellent! This is definitely a start! BTW, would you be able to take a pic of the set-up and post it, so I have a visual reference? I'm not very versant on schematics.

Also, I want to tell you how appreciative I am. You have my heartfelt gratitude!!

Chesh

[JohnH]

My cam is not working today, and in any case, I dont think a picture would help. I built it on my sons electronics kit where you push the componenets into a grillage of small sockets. Easy to do, but the end result is a tangled mess of spagetti. Theres no angle that makes it clear!

Im going away for a few days, so here is everything else I can think of:

Its not a hard circuit to wire up, and the schematic is the best way to follow it. Please note, the way I draw circuits: a dot indicates two wires connected, but if they cross but with no dot, they are not connected (its too hard to draw little loops where wires cross!).

I find a $20 digital multimeter an essential tool. You can check resistance values when its too hard to peer at the coloured stripes, and also with a transistor test function, test for the e, b and c connections of unknown transistors.

If you build it, start with Q1 and Q2 and get that going as a fuzz box first.

As to how to prototype it, you may have your own favorite way, but these plug in breadboards make it very easy with no soldering. When I started doing this however, we used to stick the schematic on a piece of wood, put small nails at each joint, tin themwith solder and then just solder the components on top of the schematic - cant go wrong then.

Finally, as to the component values, if you think there is mileage in it, it would be good to try some variations in values, particularly in the Q4 and Q5 part. The value of the 2.7k resistors could be raised to draw less current, which may need a change to the other resistors nearby. I think the capacitor values are probably higher than they need to be. Then it would need some pots to mix the sound properly and set the level, and some treble cut to calm it down a bit. It might be quite interesting to be able to combine the pure tone, the basic fuzz (from Q2) and the divided fuzz in a controlled way.

cheers

John

[CheshireCat]

johnh said:

My cam is not working today, and in any case, I dont think a picture would help. I built it on my sons electronics kit where you push the componenets into a grillage of small sockets. Easy to do, but the end result is a tangled mess of spagetti. Theres no angle that makes it clear!

Im going away for a few days, so here is everything else I can think of:

Its not a hard circuit to wire up, and the schematic is the best way to follow it. Please note, the way I draw circuits: a dot indicates two wires connected, but if they cross but with no dot, they are not connected (its too hard to draw little loops where wires cross!).

I find a $20 digital multimeter an essential tool. You can check resistance values when its too hard to peer at the coloured stripes, and also with a transistor test function, test for the e, b and c connections of unknown transistors.

If you build it, start with Q1 and Q2 and get that going as a fuzz box first.

As to how to prototype it, you may have your own favorite way, but these plug in breadboards make it very easy with no soldering. When I started doing this however, we used to stick the schematic on a piece of wood, put small nails at each joint, tin themwith solder and then just solder the components on top of the schematic - cant go wrong then.

Finally, as to the component values, if you think there is mileage in it, it would be good to try some variations in values, particularly in the Q4 and Q5 part. The value of the 2.7k resistors could be raised to draw less current, which may need a change to the other resistors nearby. I think the capacitor values are probably higher than they need to be. Then it would need some pots to mix the sound properly and set the level, and some treble cut to calm it down a bit. It might be quite interesting to be able to combine the pure tone, the basic fuzz (from Q2) and the divided fuzz in a controlled way.

cheers

John

What are the values for the different transistors.

Chesh

[JohnH]

They are all the same, and are small NPN transistors. They would not be critical, hence you could use whatever you have, or what ever is in the bucket at radioshack. The kit I used has type 2SC for these. Other suitable ones would be BC108c or BC109c
John

[CheshireCat]

johnh said:

They are all the same, and are small NPN transistors. They would not be critical, hence you could use whatever you have, or what ever is in the bucket at radioshack. The kit I used has type 2SC for these. Other suitable ones would be BC108c or BC109c
John

Cool! Thanks for everything!

Chesh

[JohnH]

Hi Chesh - back again.

I was looking through some gadget sites and heard about what seems to be a pro version of the 'fuzz divider', which is alot more complex but addresses some of the problems with this type of circuit. It is called the 'Rocktave Divider'. Heres a page with a link (bottom of page) to an article about it, with the design.
ampage.org/cgi-bin/hammer/index.cgi?cmd=lt&xid=&fid=&ex=&pg=11
here is the pdf of it:
ampage.org/hammer/files/rocktave.pdf
If you google +rocktave +divider, youll find a few discussions, which suggest that the rocktave divider was the best of its type, and that it necessarily has to be fairly complex to work properly. The pdf above describes some of the issues of tracking the signal, and sputtering as the signal dies at the end of the note, and how it addresses these.

My circuit does have some of these problems, but it is a first attempt and it does work!

[CheshireCat]

johnh said:

Hi Chesh - back again.

I was looking through some gadget sites and heard about what seems to be a pro version of the 'fuzz divider', which is alot more complex but addresses some of the problems with this type of circuit. It is called the 'Rocktave Divider'. Heres a page with a link (bottom of page) to an article about it, with the design.
ampage.org/cgi-bin/hammer/index.cgi?cmd=lt&xid=&fid=&ex=&pg=11
here is the pdf of it:
ampage.org/hammer/files/rocktave.pdf
If you google +rocktave +divider, youll find a few discussions, which suggest that the rocktave divider was the best of its type, and that it necessarily has to be fairly complex to work properly. The pdf above describes some of the issues of tracking the signal, and sputtering as the signal dies at the end of the note, and how it addresses these.

My circuit does have some of these problems, but it is a first attempt and it does work!

Alright, two words:

First: WOOOOOOHOOOOOOOOOOOOOOOOOOO!!!!!!!!!

Second: UDAMAN!!!!!!

As far as your set-up, it's excellent, and it apparantly does work, based on your results, so, hey, it's still on the table!

The EverGrateful Chesh

[JohnH]

You are most welcome Chesh.

Ive been tinkering with the fuzzdivider this afternoon, and here is Mark 2. people.smartchat.net.au/~l_jhewitt/circuits/fuzzdividerMk2.gif

Same circuit, with a few resistors increased. Current drain is now a reasonable 2.2 mA. Theres a 100MFd cap across the 1k resistor (maybe with a small resistor, zero to 200 Ohms in series), this cranks up the gain to make it respond better. Ive added a bit of Eq at the output, to bring the signal level down and emphasise the bass tones. The 1k resistor in the power line seems to control stuttering at the end of the note, so notes finish more cleanly.

It now plays much better, and can do some very heavy bass parts. Pluck the lowest E string, and the sound (an octave down) sustains constantly for about 40 seconds, then stops! Theres a knack to playing it.

Based on all that , Im now reclassifying this design from 'elephants fart', to 'almost musical elephants fart'
cheers
John

[CheshireCat]

johnh said:

You are most welcome Chesh.

Ive been tinkering with the fuzzdivider this afternoon, and here is Mark 2. people.smartchat.net.au/~l_jhewitt/circuits/fuzzdividerMk2.gif

Same circuit, with a few resistors increased. Current drain is now a reasonable 2.2 mA. Theres a 100MFd cap across the 1k resistor (maybe with a small resistor, zero to 200 Ohms in series), this cranks up the gain to make it respond better. Ive added a bit of Eq at the output, to bring the signal level down and emphasise the bass tones. The 1k resistor in the power line seems to control stuttering at the end of the note, so notes finish more cleanly.

It now plays much better, and can do some very heavy bass parts. Pluck the lowest E string, and the sound (an octave down) sustains constantly for about 40 seconds, then stops! Theres a knack to playing it.

Based on all that , Im now reclassifying this design from 'elephants fart', to 'almost musical elephants fart'
cheers
John

Excellent! That looks very exciting. I was at RS earlier, pricing things out. Now that I've had a chance to compare a breadboard to your schematic, it makes more sense.

BTW, at www.paia.com, they have sound samples from Craig's book with the roctave fuzz divider. Here's the sample for the divider. Does your version (mk2) sound kinda like this?

Chesh

[JohnH]

Well, a bit like that!

Heres my project for today: I will try to make a sound sample and post it

The Rocktave is a much more sophisticated circuit, with its control of dynamics and other functions, and I see that you can buy a kit from that site. Mine is less scary to fiddle with though, since the parts should be cheap and there are no IC's needed.

Isnt it great when you find that some dude had the same idea over twenty years earlier, and made a fully developed version? I also need to get on with one of my other projects: I have an idea to put these round things on each corner of my car to make it roll better.

[CheshireCat]

johnh said:

Well, a bit like that!

Heres my project for today: I will try to make a sound sample and post it

The Rocktave is a much more sophisticated circuit, with its control of dynamics and other functions, and I see that you can buy a kit from that site. Mine is less scary to fiddle with though, since the parts should be cheap and there are no IC's needed.

Isnt it great when you find that some dude had the same idea over twenty years earlier, and made a fully developed version? I also need to get on with one of my other projects: I have an idea to put these round things on each corner of my car to make it roll better.

Well, if you can make a sound clip, that would be great, but I'll still move ahead with your mock-up anyway, as it will definitely give me something to work with.

Sure, the Roctave Divider is more sophisticated and sounds great, but there are some options on it that I don't think I'll use, and I need to make it smaller and more streamlined, so I can fit it into my Utah with minimal wood loss.

So, your circuit is definitely the ticket right now.

Thanks!
Chesh

[JohnH]

OK, well I learn something everyday. Ive managed to make some clips, never done that before! - here they are:
people.smartchat.net.au/~l_jhewitt/circuits/fuzzdivsample1.mp3
people.smartchat.net.au/~l_jhewitt/circuits/fuzzdivsample2.mp3
people.smartchat.net.au/~l_jhewitt/circuits/fuzzdivsample3.mp3

The clips were recorded via an old tape deck (as a mixer), straight into the line-in of the computer, using Creative Recorder and WaveStudio, then ripped to mp3 with MusicMatch.

To make it interesting, I took one channel from the main divided output, and the other channel has a little of the undivided fuzz sound after the second transistor. I pulled out the 100 MFD cap which I drew across the 1K resistor for these clips.

I hope you have a sub-woofer - this thing is making my desk shake!

John

[CheshireCat]

johnh said:

OK, well I learn something everyday. Ive managed to make some clips, never done that before! - here they are:
people.smartchat.net.au/~l_jhewitt/circuits/fuzzdivsample1.mp3
people.smartchat.net.au/~l_jhewitt/circuits/fuzzdivsample2.mp3
people.smartchat.net.au/~l_jhewitt/circuits/fuzzdivsample3.mp3

The clips were recorded via an old tape deck (as a mixer), straight into the line-in of the computer, using Creative Recorder and WaveStudio, then ripped to mp3 with MusicMatch.

To make it interesting, I took one channel from the main divided output, and the other channel has a little of the undivided fuzz sound after the second transistor. I pulled out the 100 MFD cap which I drew across the 1K resistor for these clips.

I hope you have a sub-woofer - this thing is making my desk shake!

John

I am impressed!!! And believe me, it takes a lot to impress me!

Alright, the modified, streamlined Rocktave Divider will be the Holy Graile the long term, and I am going to put your fuzzdivider together. It sounds excellent . . . better than I could have hoped for. Truly.

I'm going to make my way to my fav electronics store and get what I need, and then start figuring this out. Fortunately, your design is small and simple enough that I can make it really small and compact to fit into my guitar.

Now I just get to figure out how to make the pickups . . . which I kinda know anyway . . . it's just gets down to the logistics of putting it together.

Also, I came up with some other ideas.

For one, what if I wanted to convert my guitar into a bass outright? Well, I could then draw signal from the neck pickup. What if I wanted to combine bass and guitar action together? Then I could use those special pickups.

I'm thinking that some simple switching could have several possibilities indeed!

Also, while the Rocktave Divider has a lot of niceties, the first purpose is for it to do what you've accomplished outright. This, in fact, may very well be the streamlined version I needed in the first place.

I'll let you know how things develop. Thanks!!

BTW, what ever became of those round things you were going to put in the corners of your car?

The EverGrateful Chesh

[JohnH]

cheshirecat said:

BTW, what ever became of those round things you were going to put in the corners of your car?

It turned out the Sumerians had them all figured out by 3000BC. ( @#%! and &%*@ !!!!)

Ill be interested to see how it goes with your pickups. I think its a good idea just to pickup from a couple of strings, because this sort of circuit gets mixed up if theres more than one note happening at a time. Also, when you get it basically working, , but before hard wiring it, youll want to play with various resistors and capacitors to tune the levels and tone of the input and output, and to mix the divided and undivided sounds.

best wishes and good luck!

John

[CheshireCat]

johnh said:

cheshirecat said:

BTW, what ever became of those round things you were going to put in the corners of your car?

It turned out the Sumerians had them all figured out by 3000BC. ( @#%! and &%*@ !!!!)

A-ha!! Those blasted Sumerians. Typical. Just typical.

johnh said:

I'll be interested to see how it goes with your pickups.

I'll keep you posted, and thanks!

johnh said:

I think its a good idea just to pickup from a couple of strings, because this sort of circuit gets mixed up if theres more than one note happening at a time.

True. I'm still working on whether to do E and A, or E, A, and D.

johnh said:

Also, when you get it basically working, but before hard wiring it, youll want to play with various resistors and capacitors to tune the levels and tone of the input and output, and to mix the divided and undivided sounds.

Any insight on how I would go about doing that? Like, are there any guiding principles in terms of whether I increase the value of one cap or resistor, I get one result, vs. decreasing it gives another result?

Also, a question: in the diagram a wire in lower left corner of the diagram . . .

^
^
. . . runs off and then terminates in a little ball (usually indicating a connection). Is that representing the end of the side axis on the breadboard? Was there some bit of the schematic that didn't get across?

johnh said:

best wishes and good luck!

John

Thank you so much! You have been a great help!

Chesh

[JohnH]

Chesh - Ill figure out some suggestions for how to balance the sounds.

The connection at lower left goes to the ground wire from the pickups. In my case, (and for you if you test this on a breadboard) this is the sleeve connection of the lead that goes to the guitar. In a built-in version, if the pups and this circuit have a common ground, then theres no additional connection here.
J

[CheshireCat]

johnh said:

Chesh - Ill figure out some suggestions for how to balance the sounds.

Excellent! I'm sure that will be as enlightening as the rest of your work. ;D

johnh said:

The connection at lower left goes to the ground wire from the pickups. In my case, (and for you if you test this on a breadboard) this is the sleeve connection of the lead that goes to the guitar. In a built-in version, if the pups and this circuit have a common ground, then theres no additional connection here.
J

So, if I use a starground, then that wouldn't connect to anything because the ground would probably run to the starground, as would the leads from the pickup? Of course, in a sense, that ground would come straight from starground to begin with, by virtue of the fact that it is connected in a straight line to the ground thru the board.

Chesh

[Happyguy]

Wow, That is realy REALY impressive. My suggestion would be to do all the wiring on a pc board. (not realy sure if thats how u say it not being all that english). The draw out the circuit dip in acid then drill component holes method. would reduce size, and probably make it easier to wire.

[CheshireCat]

happyguy said:

Wow, That is realy REALY impressive. My suggestion would be to do all the wiring on a pc board. (not realy sure if thats how u say it not being all that english). The draw out the circuit dip in acid then drill component holes method. would reduce size, and probably make it easier to wire.

Well, welcome to the boards!

Yeah, I was thinking about burning my own board (or should that be "etching"?) after I experiemented with a breadboard and got everything working. Also, I want to make this as small, streamlined, and unobtrusive as possible.

What do you play? Think you might use one yourself?

Chesh

[JohnH]

Herse todays version - with some mixing between the divided and undevided fuzz, using a 100k pot as a blender:

people.smartchat.net.au/~l_jhewitt/circuits/fuzzdividerMk3.gif

The output is approx guitar level, and it could go to a master volume for further mixing with the rest of the guitar Thers a 0.47 cap on the right of the circuit - you could try a lower value for a brighter bass sound

John

[Mini-Strat_Maine]

johnh said:

Based on all that , Im now reclassifying this design from 'elephants fart', to 'almost musical elephants fart'

Dagnabbit, John, do a "C&C Warning" when you write something like that! I had just taken a drink of coffee before I read it, and I missed a good opportunity to decorate my keyboard and monitor. ;D

For those not familiar with the term, a "C&C Warning" is a "Coffee and Cat Warning." Basically, it means set down your coffee cup, soda can, or whatever; swallow anything you were drinking or eating; move the cat off your lap so it isn't startled, thereby becoming attached to your leg; then go ahead and read this with little or no chance of damages when you bust out laughing.

Okay, back on topic. (Ahem.) I recall ads some years back for an octave divider that was supposed to help a guitarist sound like "Eric Clapton and Jack Bruce at the same time," if I remember correctly. I'm trying to remember if it was a preassembled pedal, or one of the PAiA kits. If the latter, there might be circuits shown in "ELECTRONIC PROJECTS FOR MUSICIANS." www.paia.com/epfm.htm
Instant Update: Hey, the Roctave Divider was a PAiA kit. I was looking for info on the Danelectro Chili Dog Octave, and found this: filters.muziq.be/model/paia/roctave

Anyway, I have a Danelectro DJ-12 Chili Dog Octave mini-pedal, which will drop a signal one or two octaves, depending on the setting. It will let you mix the "dry" signal with the octaved signal, and I don't think it adds any fuzzing. Maybe at eBay prices, one could be dissected to get what you need? filters.muziq.be/model/danelectro/chilidog

Hope this long post is of some help, somehow.

--
Doug C.