two (great?) ideas

[Halion]

Ok, I don't know that much about electronics, but I have succesfully build a Rebote 2 delay and added a volume control to my Mini Q-tron. Here's what I was thinking:

1: If you just want to pitch the sound of my instrument, how would I do that? Wouldn't a simple pot do the entire trick?

2: I'm a bassplayer, and if there one thing that bassplayers are looking for, it's that honk that you get from vintage basses. Now, I was thinking, low notes on the bridge pickup sound greatest, because the frequenties are so low that you can actually hear the sine (like a motor running). However, when moving up just 1 string, that driving kindoff sound is already almost gone, and going up further it just dissappears. If I were to use a tremelo, set to only change the volume a little bit, but on a really, really fast rate, would that not create the great drive-like sound on any note?

I really don't like overdrive or distortion on bass, so don't tell me to use that :wink: Would it even be possible to make a tremelo go up to around 40/50 hz?

[jrc4558]

The problem with a 40Hz tremolo is that we would hear the LFO working.
Usually LFO runs below the bottom treshold of human audio range, which is 20 Hz and thus we have good modulation without any interference with audio.

[Halion]

hmm, ok, no way to work around that?

[Lurco]

ringmodulator

[jrc4558]

But you're not after a ring modulator, are you?

[Halion]

no, why would I use a ring modulator, it sounds nothing like a tremelo  :?

[claydavis]

i think people are having a hard time figuring out what you're after. a tremolo won't do much to make your bass sound vintage, and if you run a tremolo at 40-50 hz, it will sound like a ring modulator. if you want honk, play a 2 pickup bass (preferably a jazz) with the neck pickup rolled back a bit, and the low-mids boosted at the amp. maybe if you clarify, someone can offer more insight.

clay

[Sic]

what kind of bass? active or passive? those kinds of things are something to consider...

[ExpAnonColin]

Here's the answer...

A tremolo is 2 quadrant multiplication.

Literally this means adding 2 signals together (a and b) and getting a, b, a+b and a-b out.

An LED/LDR combo is two quadrant multiplication.

Tremolos normally go up to about 10hz.

Human hearing range starts normally at about 20hz.

Signal a is the guitar, b is the LFO.

Since b is below the hearing range, you only hear the guitar, a, and the sum and difference of the frequencies, which all together is the tremoloed signal.

Ring modulation is 4 quadrant multiplication.

With 4 quadrant you only get a+b and a-b.

Remember, you're adding frequencies-but probably not in the sense you're thinking of.  Think of adding waveforms, I think it helps more to visualize it that way:


Ring modulators normally go from 100hz to maybe 10khz.  The good ones go below 20hz (but we'll get to that later).

You get the added and subtracted signal out-the familiar bell sound.  Ding dong, beow bwow, space ship... odd funky sounds.  No guitar, no 10khz signal.

So then let's say the ring modulator, or 4 quadrant multiplier, is going sub audio rates, a la a tremolo.

It will sound like a tremolo, yet slightly different.  Why?

Well, with 4 quadrant multiplation vs 2 quadrant, the way people normally set it up is by "nulling" the carrier signal, or the LFO.  With 2 quadrant, then, now you're getting the guitar signal and the added and subtracted.  If you're getting the guitar signal out, why does it sound effected?  Because the added and subtracted signals will mask the overall signal...  it's not too easy to explain, and probably easier to just think of as an automatic volume knob, but oh well.  Now, with the 4 quadrant, you're NOT getting that guitar signal out-you're getting the added and subtracted signals only.  So, what that sounds like is basically a super deep tremolo-sort of like a square wave.  It's sort of hard to explain the aural difference without just listening to a slow ring mod or 4 quadrant, but a properly nulled 4 quadrant will sound different than a properly nulled 2 quadrant.

You could also think of it that the 2 quadrant needs less nulling (because you still can hear changes in potential difference, even if it's a low frequency, like a low frequency square wave sounding like a metronome, it still needs nulling, just not as much).  The 4 quadrant, however, jumps into the auditory range and our mind adds up those fast potential difference changes into tones... at which point we need to get rid of that completely.  2 quadrant, we're just getting rid of the peaks, really, with 4 quadrant you have to get rid of the entire tone at the output to get it to be just a+b, a-b.

So why does this matter to what you're asking?

Well, if you want a 40hz tremolo... that's going to jump to audio range and the brain will turn it into a signal and you'll be able to hear the low frequency in there, sort of just as a constant obnoxious rumble.  However, with a ring mod, you've got the signal totally nulled out of there-you won't hear it, at all.

So, my friend, go with a ring modulator.  Most people don't realize that the two devices are very very very similiar just because the LFO ranges are often so different.

There are many ring mod schematics on my site to get you started.

Good luck.

-Colin

[Halion]

Ah, sorry guys, I understand now. I forgot the frequency and volume are the same to an electronic defice, it's just matter of zooming in. Hmm, ok, well so much for the 40-50hz tremelo. I still think something around 20hz might be good, I'll try that sometime if I can find a cheap trem to mod.

And I know I won't get a vintage bass sound that way, I was just looking at it from a purely technical point of view. I'm very happy with the sound I can get from my bass infact. I just wanna try that someday;)