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Topic: Building an active vol pedal |
J Fletcher
From:
London,Ont,Canada
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Posted 23 Jan 2007 10:04 am |
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Hello folks
I'm thinking about building a buffered active volume pedal, and wondered if any one else here had done this, and had any tips.
Looks like I'll need some sort of a voltage controlled amp chip, and a good audio opamp. I've looked at a few sites on the web, and there seems to be a few circuits out there. Any body had success building one of these?
Thanks...Jerry |
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John Daugherty
From:
Rolla, Missouri, USA
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Keith Cordell
From:
San Diego
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Posted 23 Jan 2007 1:22 pm
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| I wondered how many posts would go on before someone had to bring up the Hilton. Not many, as it turns out. |
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John Daugherty
From:
Rolla, Missouri, USA
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Posted 24 Jan 2007 4:50 am
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Jerry, I am not aware of any schematics that are available for the circuit you want (perhaps there are some).
The Hilton pedal has an Infra red LED, pointed at an infrared detector. The pedal moves a piece of film between the LED and the detector. The film is shaded, with the shading increasing,logarithmically with distance. The detector controls the voltage to a voltage controlled preamp.
I am aware of a voltage controlled audio preamp that Peavey uses in their mixers. It is an 8-pin dip, SSM2017. It requires a +12vdc source and a -12vdc source.
You will have to do a lot of experimenting to come up with a high impedance input circuit and an EQ circuit to give a flat response.. You will also have to locate a source for the shaded film strip.
That's about all I can offer in the way of help .... Good luck.......JD.
_________________
www.home.earthlink.net/~johnd37
www.myspace.com/johndaughertysteelguitar |
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Jack Stoner
From:
Kansas City, MO
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Posted 24 Jan 2007 5:48 am
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Along with the Hilton that I use and recommend, Goodrich also has some "electronic" volume pedals.
As far as building one yourself, you are basically "on your own" to design and build it. Practically any information that is available is based around a 6 string guitar and it's particular properties which are much different than a pedal steel guitar (impedence of the pickup and the output level of most steel guitar pickups compared to a 6 string guitar). |
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J Fletcher
From:
London,Ont,Canada
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Posted 24 Jan 2007 3:10 pm
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| Thanks for the replies guys. I was thinking something along the lines of having all the active circuitry inside my amp, which I built, and the foot pedal would only be the controller for the VCA. In fact, there is a circuit I found on the web, that does this. That way, there's no need to run power to the pedal, though there would still be a cable between the pedal and the amp, and one from the guitar to the amp. Wouldn't buffer the guitar to amp connection though, which I think the Hilton does....Jerry |
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Robert Leaman
From:
Murphy, North Carolina, USA
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Posted 24 Jan 2007 7:11 pm Volume Pedal
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| There are several circuits that convert linear signals to a logarithmic signals. Also, it is possible to control taper from linear to almost any mathematical curve that one desires. This permits use of a linear potentiometer to produce a tapered signal. A high impedance pre-amp that is linear from DC to almost 1 MHz is no technilogical challenge with today's IC op-amp selections. I designed several modules that convert a linear signal to virtually any taper (non-linear function). It seems that AC 3-phase motors need such tapers so that constant torque can be applied during motor acceleration with mechanical loads that do not have constant, linear torque demands with respect to motor speed. Such motor control is used for energy conservation and torque shock avoidance in mechanical linkages. Since I hold design rights for these modules, they are not published. I offered to help with this some time ago but I was told that Hilton has all these capabilities but a Hilton pedal cannot meet all this criteria. Buy Hilton. |
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Joe Buczek
From:
Montana, USA
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Posted 29 Jan 2007 7:52 pm Re: Building an active vol pedal
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Jerry,
Here is a URL to the data sheet for the exact op-amp part used in the Goodrich 10-K pedal: http://www.onsemi.com/PowerSolutions/product.do?id=MC33078DR2 I had a problem with my L10-K when I purchased it (new) and opened it up. The data sheet that ON Semi supplies contains what appeared to me to be a substantially similar circuit to that found in the Goodrich pedal. After seeing how simple the circuit was, and that the vendor actually supplies you this design, I also considered building an outboard circuit that could be controlled, as you mention, by a standard volume pedal. I think its a great idea.
One problem I can think of with what you're contemplating is signal attenuation between the instrument and the op-amp circuit. I think you want the op-amp located as closely as possible to the guitar, not at the other end of a cable near the amplifier. Other than this, I like the idea and had contemplated doing something like it myself.
As for misters Goodrich and Hilton, I think they are very fine folks who make great products as many here on the forum will attest. I personally own a Goodrich L10-K. It is built to last and I know I couldn't afford to build a pedal for what Goodrich sells them for. Is there anything wrong with Do It Yourself? Absolutely not! I say "Go for it!" And Good Luck! |
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