output voltage of pedals

[Wounded Paw]

I saw someone asking this on a different (non stompbox) forum about the maximum output voltage of pedals and now I'm curious myself.  Guitars supposedly put out around 0.15 to 0.4 volts peak AC and pedals can boost this quite a bit and it all depends on how the amp you're going into can handle it but what's a safe limit on the output voltage of a pedal?

[earthtonesaudio]

Max theoretical output is the available supply voltage (9V p-p for most stompboxes).  In reality, you hardly ever see this much because most devices don't operate rail-to-rail (some opamps do though).

A side note, guitar outputs vary a lot, some hotter humbucker guitars can put out over 1V p-p.

You're right though, the amp you plug into after the effect makes a lot of difference.

If you want a good practical example, the LPB booster probably swings less than 7V p-p at maximum.

(p-p=peak to peak AC voltage)

[R.G.]

There is no safe limit on the output of a pedal.

Some pedals use tubes running from hundreds of volts, and I'm certain that someone will hook the plate output up to the output jack; you could have 150V peak to peak.

[Wounded Paw]

I was thinking more of a general guideline than an absolute limit.

[R.G.]

OK.

Then it's the voltage available from a 9V battery; 9V and a bit over peak to peak. CMOS opamps are available that easily do rail to rail. For ordinary opamps, 7V peak to peak, as they lose 1-2 V at each rail. For transistors, battery minus about half a volt.

On average, people turn them down much more than that, perhaps to 1-2V peak to peak. But not a day goes by without some new metalhead wanting MORE drive.

[DougH]

not a day goes by without some new metalhead wanting MORE drive.

Heh-heh...

Quotable  quote, R.G. Thanks for the sig...

[ForcedFire]

Sorry to drag this up from the dead. I ran a search wondering the same thing. I'm working on a clean boost for my friend's band. I used a set of red LED's as an overload protection and have them running to the two 'O's in the word BOOST on the case. It's pretty cool, might be distracting to my friend but we'll see. Anyways it's clipping a lot more than I was hoping so I'm going to add a switch to let it run wide open and was wondering how much voltage I should let out of the little guy.

I've looked through some amp manuals in the past and seen input limits as low as 1V RMS but I'm assuming this more an issue of the amp saturating and not being able to provide real clean tones at that point. The maximum rating on a transistor or tube input stage can't really be less than what we're getting out of a 9V supply?

Thanks!

Nathan

[R.G.]

Sorry to drag this up from the dead. I ran a search wondering the same thing. I'm working on a clean boost for my friend's band. I used a set of red LED's as an overload protection and have them running to the two 'O's in the word BOOST on the case. It's pretty cool, might be distracting to my friend but we'll see. Anyways it's clipping a lot more than I was hoping so I'm going to add a switch to let it run wide open and was wondering how much voltage I should let out of the little guy.

I've looked through some amp manuals in the past and seen input limits as low as 1V RMS but I'm assuming this more an issue of the amp saturating and not being able to provide real clean tones at that point. The maximum rating on a transistor or tube input stage can't really be less than what we're getting out of a 9V supply?

No good pedal issue ever stays buried. We get a new crop of folks discovering pedal building every few months, and they all need freshly educated; the questions recur.

IMHO, no designer makes an amp which would be destroyed by 120Vac through perhaps 20K of resistance on it's input. That's because humans can carry almost the full AC line voltage from stray field pickup, and humans certainly touch the tip of a guitar cord connected to an amp. (human skin resistance, when dry, is about 20K more or less).

I'd bet that there's not a lot of thought that goes into amps on this topic. The vast majority of amps, particularly tube amps, just do it the way it's always been done, and that's that. Some tube amps and some solid state amps will look at the issue. Generally if there is a stated maximum, it will be for the signal level to drive the amp to distortion. I have never seen an amp with an "Absolute Maximums" rating in the way that integrated circuits have absolute maximums.

Tube amp inputs are hard to kill, being primarily just a 68K series resistor and a 1M to ground, then tne input to a 12AX7 grid. This is a pretty robust setup. Even an input that caused arcing inside the tube would not necessarily kill the tube, and if it did, the guitarist would probably say "Huh. My amp just quit. Oh, it's just another one of those (insert least favorite brand name here) tubes dying again. I just gotta get some good ones someday."

Solid state amps are where big pedal outputs would have a chance at destruction. Some of these have protective circuits to clamp the inputs to non-destructive levels. Some don't.

On your pedal, open it up and let it rip. I've designed pedals with outputs much bigger than a 9V battery, and it's become common for guitarists to run 9V pedals from 12V or 18V power supplies because they read somewhere on the internet (and can't remember that url...  ) that it was more better that way somehow. Made their guitar sound like lasers or spiders or something... !?

On the quip: "But not a day goes by without some new metalhead wanting MORE drive."    We get this request so often that we've considered putting a "More" knob on some pedals. The knob would be connected to a bunch of parts on the PCB - all of which are NOT connected to anything else! I bet we'd get a huge number of posts in the online fora about the setting of the "More" knob being better one position than the other, or lists of how to set it for what tone. 

[ForcedFire]

  too funny.

[Juggernogjones]

Hi all,
Sorry if this is the wrong place for this question but the title seemed relevant

I'm not actually trying to build a Stomp box, but I'm trying to work out whether my setup is safe.. Because a few people have told me that I risk damaging amps/speakers that I plug in to

My setup chain is:
1.Guitar and laptop go into 4channel behringer mixer
2.mixer into boss mt2 metal zone pedal
3.mt2 into boss dd7 pedal
4.dd7 into vol/wah ped
5.vol/wah pedal into tc electronics ditto x4 looper pedal
6.ditto x4 directly into the following items:

-ditto stereo outs direct into PA desk
-ditto mono out direct into rubbish computer speaker
-ditto stereo outs into aux input on a hifi Amp
-ditto stereo outs into Yamaha hs8 active monitors


Forgetting tone and sound quality.. Are these configs safe? Or am I going to leave a trail of damaged speakers/amps/other things wherever I go?

I ask this question because people have said to me that the output level(or maybe voltage) is higher from fx pedals? I. E. Too high

I know the ideal route is using a guitar Amp and fx loop, but my need is for portability and so far this works for me

Would be really grateful for any feedback or confirmation either way
Thanks for reading!

[antonis]

a few people have told me that I risk damaging amps/speakers that I plug in to..
people have said to me that the output level(or maybe voltage) is higher from fx pedals? I. E. Too high

Hi & Welcome..

What might damage amp should be an extraordinary input signal level (too high voltage)..
This isn't the case for Ditto X4 Looper..
https://www.fullcompass.com/common/files/31707-TCElectronicsDittoX4LooperUserManual.pdf
(9VDC powered - even if there is a voltage doubler inside, don't worry..)
So, you have to go back to last pedal output (vol/wah)..
As far as it's designed as guitar effect, don't bother anymore..

P.S.
I can't get why you ask some people for something said by other people..

[Juggernogjones]

Thanks for the reply dude!

First, my new ditto x4 came with a 12v power supply so it's really weird that the manual says 9v! But maybe I could also use 9v

My English isn't prefect, so I just wanted to check what you meant by this:

"So, you have to go back to last pedal output (vol/wah)..
As far as it's designed as guitar effect, don't bother anymore.."
Does this mean the output won't cause a problem to any amp/speaker combination?

And I liked your p.s. Haha.. I just had to get a second opinion because they guys who told me couldn't explain it.. And I couldn't risk my expensive monitors!

[antonis]

Does this mean the output won't cause a problem to any amp/speaker combination?

OK.. Let's take it from another point of view..

What about amp/speaker specifications..??

[GibsonGM]

Thanks for the reply dude!

First, my new ditto x4 came with a 12v power supply so it's really weird that the manual says 9v! But maybe I could also use 9v

My English isn't prefect, so I just wanted to check what you meant by this:

"So, you have to go back to last pedal output (vol/wah)..
As far as it's designed as guitar effect, don't bother anymore.."
Does this mean the output won't cause a problem to any amp/speaker combination?

And I liked your p.s. Haha.. I just had to get a second opinion because they guys who told me couldn't explain it.. And I couldn't risk my expensive monitors!

We're talking about the wisdom of the ages here, friend    He has Solon and Antonis the Thessalonian quoted in his profile...never steered me wrong yet...