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Pedal Voltage

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Pedal Voltage

Postby twotoedsloth » Tue Oct 29, 2019 2:16 pm

Hello, thanks for taking the time to read this.

I am working with a bassoonist this week who will be running through several pedals.

How much voltage should I be expecting to come out of the last pedal in the chain?

Many thanks,

Peter
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Re: Pedal Voltage

Postby James Perrett » Tue Oct 29, 2019 2:29 pm

If these are guitar pedals then they'll usually be designed so that the output is at a similar level to the input. Guitar levels are usually 20dB or so lower than line levels and guitars like to see a high impedance but the pedals themselves are usually happy driving lower impedances so, unless you have an instrument input on your audio interface, I'd just use a line input with plenty of gain.

I'm assuming that the bassoonist will take care of matching their mic or pickup to the input of the pedal. You can often get away with plugging a mic straight into a pedal but the levels and impedances aren't an ideal match.
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Re: Pedal Voltage

Postby Hugh Robjohns » Tue Oct 29, 2019 4:56 pm

twotoedsloth wrote:How much voltage should I be expecting to come out of the last pedal in the chain?

In strict technical terms it depends on the signal voltage going in to the first pedal, and the sum of all the gains of all the pedals....

But in general, as most effects pedals are designed to operate with unity gain (or nearly so), the signal voltage from the last pedal is likely to be similar to that of the input signal.

Of course, there are some high-gain pedals so it would help to know what specific pedals are involved, and what the input source is.
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Re: Pedal Voltage

Postby twotoedsloth » Tue Oct 29, 2019 5:03 pm

Thank you sincerely for all of your replies.

Unfortunately the bassoonist is being rather cagy about which pedals she is using. She is using a Shure Beta 57 microphone.

Should I be using a DI box, or can I plug this directly into the line inputs on my mixer (Yamaha O1V96i)?

Your advice is greatly appreciated.
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Re: Pedal Voltage

Postby Sam Spoons » Tue Oct 29, 2019 5:14 pm

If she is sending you the output from the last pedal it will be unbalanced, in which case I'd use a DI unless it's a very short run to the desk.
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Re: Pedal Voltage

Postby Hugh Robjohns » Tue Oct 29, 2019 5:43 pm

Personally, and assuming this is in a home studio, I'd plug the pedal output straight into the mixer line input. But if it's on stage, or a long cable is involved, a DI box might be needed.
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Re: Pedal Voltage

Postby Arpangel » Wed Oct 30, 2019 10:11 am

Just make sure you use the right leads, I got caught out recently. Now I use unbalanced TS leads into mixer line inputs, as most pedals are unbalanced anyway.
I inadvertently used a balanced TRS lead on a dual power Boss pedal, if your pedal has battery as well as mains operation the TRS plug will throw it into confusion, resulting in hum and no signal.
If you're going into a DI box, make sure you go in unbalanced, using TS leads.
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Re: Pedal Voltage

Postby Wonks » Wed Oct 30, 2019 10:43 am

Presumably the bassoonist has got a lo to hi impedance converter between the SM57 and the first pedal. The mic signal is going to be pretty low compared to a guitar output, so the first pedal is probably some boost pedal or preamp to get the signal a bit hotter. This and the other pedals are probably going to add some noise, especially if there's a compressor involved.

If this is a recording rather than live work, you may want to think about adding a second mic and recording that direct, then duplicating the FX pedals in software (for a quieter recording). You can then decide which sounds best, or maybe blend/swap between the two if some of the stomp pedal sounds are better than the software ones.
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Re: Pedal Voltage

Postby Arpangel » Wed Oct 30, 2019 11:06 am

Maybe plug the 57 into a mixer channel, then use a direct line out, or aux, to feed the pedal, if a mixer is bring used and you have a spare channel, saves using or buying a converter.
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Re: Pedal Voltage

Postby Exalted Wombat » Wed Oct 30, 2019 1:37 pm

If she performs with effects, her accustomed 'instrument' probably consists of bassoon, effect pedals and a personal speaker/amp combo. Let her use it, mic it or tag a DI from the combo. I suspect her playing technique will be very bound up with HEARING the effects as she plays. Not a good idea to look at her pedals and say 'Oh throw them away, I can give you better quality effects in the mix'!

If you decide not to use her speaker, well, she must be feeding it a signal that looks like a mic output or looks like a line output. Nothing you won't be able to cope with either directly or through a DI box.
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Re: Pedal Voltage

Postby Wonks » Wed Oct 30, 2019 3:02 pm

Exalted Wombat wrote: Not a good idea to look at her pedals and say 'Oh throw them away, I can give you better quality effects in the mix'!.

Did I say throw them away? I just said it may be quite noisy, so a straight additional mic recording might be useful, in the same way that an additional DI'd guitar recording when micing an amp is always a useful fall-back.

If they do use a combo when recording, rather than headphones, then a straight mic recording may not be possible due to spill.
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Re: Pedal Voltage

Postby twotoedsloth » Wed Oct 30, 2019 3:13 pm

Hello again,

This project is for a live concert, so it will be on a stage. I will use a DI box, as the cable run will be about 150 feet. Would you recommend an active or passive DI?

She does not want to bring an amp, which I guess is understandable, so we're patching into our house PA.

Many thanks all of you,

Peter
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Re: Pedal Voltage

Postby Hugh Robjohns » Wed Oct 30, 2019 3:34 pm

Since the output (from the last pedal in the chain) is active (ie. an electronic output driver), either a passive or an active DI box will work just fine.

H
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Re: Pedal Voltage

Postby twotoedsloth » Wed Oct 30, 2019 3:40 pm

Thanks,

I know I can always count on the denizens of this forum to set me straight.

Much Appreciated,

Peter
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