Stand alone octave up

Stompboxes circuits published in magazines, books or on DIY electronics websites.

Stand alone octave up

Postby GuitarLord5000 » 11 Apr 2017, 02:58

Hello fellow pedal freaks.

Long story short: I hate fuzz pedals. They just don't work for my sound, no matter how hard I try. I've recently found a need for an octave up effect a la the octavia or foxx. I just don't want to use the fuzz that's inherent in these boxes. I much prefer to use my Rat for the grit. I've made dozens of pedals, but never an octave up. Can someone give me an explanation of the effect, or an "Octave up for dummies" version? I'm curious what creates the octave up effects, and wondering if there is a simple octave up building block that I can solder together and throw into its own enclosure that I can use with my Proco Rat for those rare occasions when the gig demands the effect.

Thanks in advance.

Prost!
Cheers,
Dave
User avatar
GuitarLord5000
 
Posts: 33
Joined: 16 Nov 2008, 17:46
Has thanked: 2 times
Have thanks: 0 time

Re: Stand alone octave up

Postby dv8r601 » 11 Apr 2017, 05:53

Search for it. There's literally DOZENS of octave up circuits out there from passive ring mod type to the fwr pedal. Not all of them are fuzz based, but most will have at least a hint of Fuzziness. From what you have described, It sounds like the Dan Armstrong Green Ringer would be perfect for you, its a clean octave. I have one in an enclosure with a Red Llama clone a la Purple Platypus and another one that's stand alone. I know the green ringer to work well with the rat, muff, ts808, and fuzz face.

For this message the author dv8r601 has received thanks:
GuitarLord5000 (12 Apr 2017, 05:51)
dv8r601
 
Posts: 34
Joined: 08 Oct 2011, 08:28
Location: Mississippi
Has thanked: 159 times
Have thanks: 7 times

Re: Stand alone octave up

Postby GuitarLord5000 » 11 Apr 2017, 06:36

Hey, thanks for the reply!

I've been doing some searching, and surprisingly, the Green Ringer didn't turn up. I've heard of the pedal quite often, but never actually heard the thing or knew what it was. After watching a few videos, I think it might be damn close to what I'm looking for.

I did find this Octo Booster:
http://www.guitarelectric.eu/schematy/E ... r.jpg.html

It looks like a pared down Tychobrahe. Seems like it could be pretty interesting, and very low parts count. But I haven't turned up any videos or sound clips of it to actually hear it.

I think I'll breadboard both of them and see which one works best with the Rat. Thanks for the tip DV8R.
Cheers,
Dave
User avatar
GuitarLord5000
 
Posts: 33
Joined: 16 Nov 2008, 17:46
Has thanked: 2 times
Have thanks: 0 time

Re: Stand alone octave up

Postby marcao_cfh » 11 Apr 2017, 20:09

Like it has been suggested, the Green Ringer is a clean-ish octave up you can try.

This Octo Booster uses an well know way to get an octave up: a transformer and two ge diodes configured as a rectifier. You'll find this little circuit in a lot of octave effects. An example is the Tychobrahe Octavia (http://fuzzcentral.ssguitar.com/octavia.php). Since diodes drop voltage, and the guitar signal have a low voltage, you need to boost your signal before feeding the transformer to make it work, so you can use basically any gain stage to do it. The schematic you've pointed uses a mosfet booster, but you can use a fuzz (Tychobrahe uses a Tone Bender-like circuit), a IC booster (http://www.hollis.co.uk/john/titan_boost.jpg and http://www.hollis.co.uk/john/titan_octave.jpg, this one uses a full ge bridge instead of a half ge bridge), a LM386 distortion (http://www.tdpri.com/attachments/bobsoc ... pg.286759/), a TS gain stage (http://www.geofex.com/Article_Folders/S ... octave.htm), a Rat gain stage (since you said you use a Rat as your main distortion) ...

What I suggest you is to breadboard the "transformer and ge diodes" stage, and feed it with your Rat to hear the results.

A simple one that I like is Tim Escobedo's Rambler (http://www.diale.org/tpe123/rambler.gif). But it's already distorted and will act like a fuzz if you push it with another distortion, and you'll need to back down your guitar volume a little bit to reduce gain. If you want to try it, I suggest you to not connect pins 1 and 8 to reduce the gain, or use it as a stand alone unit without any distortion pushing it.

And about the "octave up for dummies", here's a little explanation: take a look at the transformer stage. You have AC signal feeding the transformer, and AC signal coming out of the transformer. This AC signal goes thru 2 diodes oriented the same way. When positive AC current is coming from "top pin of the transformer, it'll go thru the "top diode". When positive AC current if coming from "bottom pin of the transformer", it goes thru the "bottom" diode. You'll get only positive (now DC) signal, and the new wave form will be an octave up from the original wave form. Altough the Green Ringer doesn't use a transformer, you can see the 2 diodes rectifying the signal.
marcao_cfh
Breadboard Brother
 
Posts: 65
Joined: 21 Aug 2007, 04:52
Has thanked: 0 time
Have thanks: 7 times

Re: Stand alone octave up

Postby GuitarLord5000 » 11 Apr 2017, 22:49

marcao_cfh wrote:And about the "octave up for dummies", here's a little explanation: take a look at the transformer stage. You have AC signal feeding the transformer, and AC signal coming out of the transformer. This AC signal goes thru 2 diodes oriented the same way. When positive AC current is coming from "top pin of the transformer, it'll go thru the "top diode". When positive AC current if coming from "bottom pin of the transformer", it goes thru the "bottom" diode. You'll get only positive (now DC) signal, and the new wave form will be an octave up from the original wave form. Altough the Green Ringer doesn't use a transformer, you can see the 2 diodes rectifying the signal.


THIS! Thanks marcao. I noticed that every analog octave schematic that I've seen utilizes diodes to achieve the effect. I know very little about rectification, and I don't quite understand how the use of a diode rectifier doubles the hertz of the signal in order to achieve an octave effect. But your explanation does give me a place to start researching.

marcao_cfh wrote:Since diodes drop voltage, and the guitar signal have a low voltage, you need to boost your signal before feeding the transformer to make it work, so you can use basically any gain stage to do it.....
.....What I suggest you is to breadboard the "transformer and ge diodes" stage, and feed it with your Rat to hear the results.


I like the idea of feeding the Rat into the octoboost. But using the effect in this manner would almost certainly amount to a severe volume drop when activating the pedal. For gigging, I'll need to turn the octave effect on and off during the songs without having a drop in volume. If anything, I'd want a boost in volume when the octave is activated, so I definitely need to keep the gain stage. But since the design of the gain stage isn't critical, I think that I'll just use a simple LM308 to do the boosting. I have a few of those lying around, and they're less touchy than MOSfets. Thanks for the idea!

Now I have another question. I haven't used a transformer in an effect pedal before. What sort of battery life can I expect from something like the octoboost? Seems to me like a transformer is a passive device. I don't guess that it would draw a bunch of current. But I've been known to guess wrong before.

Thanks again!

Prost!
Cheers,
Dave
User avatar
GuitarLord5000
 
Posts: 33
Joined: 16 Nov 2008, 17:46
Has thanked: 2 times
Have thanks: 0 time

Re: Stand alone octave up

Postby marcao_cfh » 12 Apr 2017, 04:44

About the battery life, well, let's think about it. The transformer stage itself is passive. If you build the stage as a passive stand alone stompbox and feed it with some amplified signal, it will work, but a volume drop is expected. So you'll need a gain stage, and the battery life will depend on the gain stage you use. So let's say you'll have a high battery life.

You can use a simple transistor gain stage (like the LPB) too.

For this message the author marcao_cfh has received thanks:
GuitarLord5000 (12 Apr 2017, 05:50)
marcao_cfh
Breadboard Brother
 
Posts: 65
Joined: 21 Aug 2007, 04:52
Has thanked: 0 time
Have thanks: 7 times

Re: Stand alone octave up

Postby GuitarLord5000 » 12 Apr 2017, 06:00

Cool. That's what I thought. I'll stick with using the LM308. Like I said, I have them lying around already. I think the transformer/diode idea is pretty solid. I also like that fact that I can use a stomp switch to switch between octave mode and boost only mode with the octo-boost. Space on my gigging pedalboard is at a premium, and any effect that can do double duty is a winner.

I'll try to remember to update this post after I build my bastardized version of the Octo-Boost. I'd also like to thank tcobretti for posting the Octo-Booster schem that I referenced in this thread (http://www.diystompboxes.com/smfforum/i ... ic=46021.0). If the Octo-Booster doesn't work for me, then I'll definitely go with the suggestion from DV8R and build the Green Ringer.

Thanks everyone.

Prost!
Cheers,
Dave
User avatar
GuitarLord5000
 
Posts: 33
Joined: 16 Nov 2008, 17:46
Has thanked: 2 times
Have thanks: 0 time


Return to DIY Stompbox designs

Who is online

Users browsing this forum: crisco and 6 guests