is slight signal 'boost' normal??

[plexi12000]

i was wondering if it is normal that some pedals give a slight boost...even though they aren't intended as such?

my recent phase 45 build does this. very slight....it doesn't bother me or anything. just wondering if this is norrmal, or maybe something I did?

thanks!  -TGIF

[GibsonGM]

Yup!  Some do, and some don't...it's very hard to figure out what kind of guitar will be the input to these effects...just how much voltage the input will contain.  They are designed around a sort of "standard" input, and there we go.  At some point, you have to just use some kind of average input for your design, and let it go. 

If it's boosting, just turn it down, LOL!   No volume control?  Put one in, or do it with another pedal downstream, or go in and hardwire some gain reduction (in a feedback loop, maybe?).

Oh, and they also may have worked a real boost in to make an effect more prominent.  Ex: I boosted my wah's output level just so that when I use it, it is OUT THERE, and NOT subtle. My preference...

[PRR]

> some pedals give a slight boost...

If a toy is not-quite unity-gain, users whine and moan and complain endlessly.

Slight boost doesn't get complaints. Very slight boost usually sounds "better" even if the box does no good or slight harm to audio.

If I was going to err, I'd sure aim for over-unity to be sure my 10% parts *never* came out to under-unity.

[Mark Hammer]

When any circuit uses 5% tolerance resistors, the odds are reasonably good that most stages of the circuit will not come out absolutely identical, unless there is some sort of internal trimmer to achieve absolutely identical function.

Since you mentioned a Phase 45, when a phaser has more than 2 stages (4, 6, 8, etc.), there are no absolute assurances that each of the stages has ONLY unity gain, and contributes nothing above that.  Because there is always the risk that this stage has a gain of 1.05 and that one has a gain of 1.07, when you place all those stages in series, you might conceivably end up with more than unity-gain overall, when those stages are multiplied together.  It won't be anything like 3x, but it doesn't have to be that much more than unity to result in oscillation when feedback is used.  Keep in mind that even if the overall gain of all the stages is "only" 1.04x. that 1.04*1.04*1.04*1.04, etc. (which is what happens when the same signal gets fed back to the start of the loop) can add up PDQ.

That's why many 4-stage and higher phasers either keep feedback fixed and modest (like the Phase 90 does), or else include a trimmer to set the maximum amount of feedback before oscillation sets in.

[plexi12000]

'nuther new term for me..."unity gain". -lol    in other words.....you're saying one stage may be "louder" than another?  does "unity-gain" then mean each stage is totally equal?

[deadastronaut]

i like to put a vol control on ALL my pedals....

i too had this drop/boost issue....no more..

[antonis]

does "unity-gain" then mean each stage is totally equal?

Equal to what..??
(Were physics quantities and units invented just for fun..??) 

In terms of Voltage gain, yes..
(theoretically input and output voltages are equal - not necessarily identical..)

Unity gain (in terms of Voltage) is mainly used either for phase inversion or/and impedance (miss)matching..

[R.G.]

Unity gain is a gain of 1.00000000, no more, no less. What you get out is the same level as what you put in.

That gets complicated when you realize that the "measuring instrument" is the human ear, which has many known and unknown tinkering mechanisms for perceived sound loudness. And effect which is a sonic mixmaster/blender on the incoming signal generates all kinds of hash that were not in the original signal, so loudness may be highly subjective.

"Unity gain" in these situations means "sounds about the same loudness".

And the comments above are right. One of the revelations of hifi tweako work on speakers is that speakers that were microscopically louder than other speakers were perceived to be either clearer or more pleasing, not louder. So a pedal whose output is slightly bigger than its input (taking into account the human ears' quirks) will be perceived as slightly better in a non-qualifiable way.

It makes for great advertising, and also makes those "replace one component" tests a little shakier. 

[plexi12000]

Thank you-  i looked up 'unity gain' and read a short tech article.  i kinda "get it".

[LightSoundGeometry]

i always thought Unity gain was a perceived, observed or a heard value that is qualitative; and quantitative can be measured scientifically in a lab to show a rise in  what I call sound, or the signal.

The way sound is transmitted and picked up is something I am very green on. I know later on we will get into frequencies and stuff. So how do you measure a increase in volume? is that the gain? or is gain the amount of distortion present in a signal?

[R.G.]

In the strict technical sense, unity gain is a gain of 1.0000000..., which is usually assumed by real-world technicians as 1.0+/- some observation tolerance. The tolerance ought to be well below 10% for even casual techs to say it's unity gain. For instance, a cathode (vacuum tube) follower has a gain that's about 0.95 to 0.97, but most people would say that's close enough to unity.

The break with this definition is in the perceptual "loudness" which we get to by listening to two signals and deciding they're about the same loudness. As I mentioned, this is slippery. Human ears don't do all that well at measuring small differences in loudness. 3db increase in audio power is perceived as a just-noticeable increase in loudness, not the doubling of audio power that it is.

We still perceive sub-db increases or decreases in loudness, but our mind/ear interprets this as "clairity" or "indefinable betterness", not loudness.

[MrStab]

if you aren't already, you should check the activated vs. bypassed states with a buffer before either pedal, just in case the perceived loudness changes when going from low to high impedance. though as it's the Phase 45 in question, which as others alluded to is a unity-gain-effect, my point is just a footnote.