What is too loud?

[Marbles]

Hi guys,

I was tinkering on a breadboard, not really knowing what I was doing, just adding gain stages etc and see what comes out of it.
This made it LOUD. Like, deafening loud. Are there any guidelines for that? I remember DBA boasting that they had pedals that could blow up your amp, and well, this was already freaking loud at 9 o' clock.


What would be suggested to tone it down a little? I'm using a 500k lin pot, to change that for a, let's say 50k would be enough? Or are there any drawbacks to that solution?

[Frank_NH]

This is an interesting question and goes to something I've considered when simulating pedal circuits using Spice.

Your electric guitar produces an voltage signal of about 0.1 to 0.5 volts, depending on the pickup.  Remember that this is an unsteady signal, and we're talking about an amplitude or some measure of the average voltage.  So this signal would normally go into you guitar amp, and it's preamp would increase the level to about 1V, then to the power amp, the speaker and your ears.  Your power amp can make your normal guitar signal very loud on it's own, but usually you have a volume knob to cut back the level from the power amp.

Now, let's add an overdrive, distortion, or fuzz pedal to the signal chain.  A tube screamer gives about 20 dB gain (maybe a little more), which translates to about a 10 times increase (gain) in voltage.  So a 0.1V signal becomes about 1V.  Of course, you can reduce this amplitude using the volume knob on the pedal, but if you crank it wide open it will give your volume a 20 dB boost.  Your guitar amp can handle this - in fact, the whole purpose of boosting the signal level in a tube amp is to cause the preamp and/or power amp stages to clip in that warm, crunchy way that we like.

Some old fuzz pedals actually don't boost the signal amplitude that much and in fact have to have their volume knobs turned all the way up to get unity gain.  This means that even though they distort the signal into a mostly square wave, the amplitude of the wave is relatively small.  BTW by unity gain, we simply mean that the output voltage level of your effect has the same amplitude as the guitar's (pickup) voltage signal amplitude.

Now, what if you generate way more than 1V output from your amplification stages in your pedal?  Like 40, 50, 60 dB?  Well, your volume (output) knob on your pedal can knock that down to acceptable levels for your amp (you may have to put it on 1...).  If you crank the effect volume all the way up, then your amp will have to deal with it by either clipping or you controlling the input volume on your preamp (or both).  Either way, it probably not a good way to get good tone (although amps on the verge of blowing up IS been a sound that a lot of people like...).

So, what is the bottom line?  If your effect output is too loud, knock the output voltage down with a variable resistor wired as a standard volume control.  100K should do the trick - I don't think it will matter a whole lot, though a lot depends on what your circuit looks like.  For me, if I'm looking at a circuit design in Spice, I try to have an output voltage gain of about 20 to 30 dB with the volume at maximum.  Anything more is unnecessary.

 

[Marbles]

Thanks a lot for your reply!

I will definitely look into Spice.. again haha. I was taking the easy route of tinkering and throwing stuff together. Notes were decaying too fast, not enough sustain. I looked at a big muff schematic and thought: Why not add the last gain stage to it, see what it does. Just a lot of volume apparently.

Your response made me realise this is not the way to go, and I will definitely think what I'm doing ;)

[Fuzz Prince Of Bel Air]

Personally, I'd rather have AMVAP (As Much Volume As Possible) and not have to use it than be in a situation where I wished I had more volume. For example, when stacking distortion.

So, to me, there is no such thing as a pedal having the potential to be too loud, just "OK, can you turn that down a bit?"-too loud.

If you feel differently and as if your pedal produces more volume than you'll ever use and that's a nuisance, then yeah, change the pot to a 50k, a 5k, etc.

But if you're asking if you can damage equipment if your pedal is too loud... I don't know anything about voltages, etc., but I presume a 9V pedal can't produce more than a 9V output.

Can an amp input handle that? Don't know... Probably?

An effects pedal? I presume it depends on the ratings of the components, but since you wouldn't build a 9V pedal with components that are rated below 9V, I'm pretty sure the pedal would be fine.

In fact, the same should apply to an amp since they run on way more than 9V.

Then there are USB audio interfaces, mixing desks, mixers, etc. To be safe, if I wanted to blast my pedal at max volume, I'd just plug it into an amp and mic it.

[Gabi Smith]

I'm not a big Genius of electronic, just humble hobbyiste that is Learning, but I don't think that the valour of the volume pot will affect the potential volume it will give.


I also Believe that to think the thing in terms " a 9v pedal can't give more than 9v signal" is a wrong way to think. The signal increased by a pedal won't rarely go upper than 2V, and if the next step can't handle the entering voltage (send by the pedal), it will distort, or fuzz. That'all.


A good way to reduce the general volume is to put a resistor before the pot. If possible, you could reduce the gain given by the last stage by adapting the résistors.

[Marbles]

It just went freaking loud haha


But what would be the difference? I don't know anything about electronics I guess, but am wondering about the following:

I thought, in a typical setting, you have a volume pot that dumps the complete signal to ground one way, and 'opens' up and passes signal the other way. The value of the pot would mean how far it 'opens' in other words how much resistance there is on the incoming signal first, and you control with the pot what's left of the signal.

So, in my mind, having a 250K resistor before a 500K pot, would be the same thing as having no resistor before the pot and using a 250K pot.

Ofcourse only when it comes to loudness. Depending on the type pot the travelling of the wiper would probably be different on both those situations.


Is there any truth in here?

[Fuzz Prince Of Bel Air]

Gabi Smith wrote

I also Believe that to think the thing in terms " a 9v pedal can't give more than 9v signal" is a wrong way to think. The signal increased by a pedal won't rarely go upper than 2V, and if the next step can't handle the entering voltage (send by the pedal), it will distort, or fuzz. That'all.

2v is not more than 9v, so you're saying the same thing I am ("a 9V pedal can't produce more than a 9V output"), but my thinking is wrong...?

[Fuzz Prince Of Bel Air]

Did you try different value pots on the breadboard? I know I've increased the volume by changing a 100k vol. pot to a 250k.

Or a variable resistor wired as a vol. pot, so some of the signal is permanently dumped to ground?

[induction]

Marbles wrote

I thought, in a typical setting, you have a volume pot that dumps the complete signal to ground one way, and 'opens' up and passes signal the other way. The value of the pot would mean how far it 'opens' in other words how much resistance there is on the incoming signal first, and you control with the pot what's left of the signal.

All approximately good, so far. Volume pots are generally set up as voltage dividers. For more conventional language, read this.

So, in my mind, having a 250K resistor before a 500K pot, would be the same thing as having no resistor before the pot and using a 250K pot.

You lost me. These two situations don't resemble each other in terms of voltage dividers or variable resistors. Try drawing them.

Also: You can change the maximum output volume by changing the pot value, but this works because you are actually changing the output load, which means you will also change the tone. (Larger volume pots are louder but also preserve treble better.) If I want to limit volume, I usually just add a resistor in front of the volume pot, but this also changes the output impedance. If you don't want to change the tone, best would be to find the voltage divider resistances when the pot is at the max volume you want, then select a fixed resistor that matches the resistance from lug 2 to lug 3 and put it in front of a volume pot that matches the resistance from lug 1 to lug 2. This might be overkill or not, depending on how picky you are and how much difference in the tone the volume pot value actually makes.

[scimitar]

Fuzz Prince Of Bel Air wrote

2v is not more than 9v, so you're saying the same thing I am ("a 9V pedal can't produce more than a 9V output"), but my thinking is wrong...?

I think you are correct, but bear in mind that since the signal swings positive and negative, it is actually a 4.5v absolute max and less than that (RMS) if the output is anything less than a square wave. Note also that not all op amps can swing the output from rail to rail. Obviously if the circuit includes a charge pump that all goes out of the window.