I need a volume knob! Advice: preamp or homebrew?

  • Thread starter Thread starter regebro
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regebro

regebro

Insane Genious!
I need a volume knob between my mixer and my monitors (which has no volume control). Should I by a hifi preamp, or is there another good alternative? I don't need to boost the signal, so theoretically I could just hook up a potentiometer to attenuate the signal, but it dosn't feel to good doing that. If there is no problem doing that, tell me.
 
OK

This is not one of my strong points so I asked an enginner who I trust that was working along side of me.

He said not to use a poten..... and that you WILL need to use a pre. Thats the short version.

If you insist I'll get the longer version.
 
What type of output are you using? Line out or speaker out?

The long version would be nice.
 
Line out, åff kårs. It's between my mixer and my monitors (Reveal Actives). My mixer doesn't have a monitor output. :(
 
Stupid question, but why not use the stereo outs that are controlled by the main fader?

Then use the lineouts for tape or whatever?

What mixer is this?
 
Because both sets of outs are controlled from the same fader. And 0db in on the monitors are FAR too loud. So I need to get the level down between the mixer and the monitors.

I saw a second hand preamp for a reasonable price ($120). No tone controls = good. Thin and nice, didn't take up a lot of space. So I wrote down the brand and number and looked it up on the internet. Pfffft, it WASN'T a preamp at ALL! It was an integrated amp... :)
 
Here is a email he sent me about a longer explanation
Only..... he too claims to have limited knowledge on this.

hi moshe.

this is not realy my speciality but:

pot is a "pasive" component. so it will degrade the sound if it will not be in the right circut.

for instance there are lots of pots in mixers but all of them are active . i mean they are all located in the circut as a variable gain.

i didint try it and i will not drive sound thru pasive component not in the right circut - but you know it is only my opinion.

another thig ----- pot is aventualy is a resistor.

mixer output is probobly low resistenc so it will work good with hight load .the power will expect low input resistenc.

so the pot will change the load on the mixer and also change the input resistenc to the power.
not a good thing to do. it will probobly work but it may change the sound .
 
I'm confused, still. What kind of mixer is it?

You're telling me if the master faders are down all the way on the mixer, it is still too loud? And it gets louder when the faders go up???? :confused:
 
The problem is that line out isn't designed to drive speakers so the voltage and expected impedance doesn't "fit" speakers. I've seen some simple circuit that handles it in, well, a simple way but I cannot find it again. Still looking though.

I think the best bet is to get a power amp though. It's a power amp you need, not a preamp, right? I'm sure old HiFi amps can be had real cheap.
 
I'm still confused :)

He's got a mixer. Every mixer I've seen has a set of main faders going to a stereo out that is designed to go to an amp and then to a set of speakers, right?

Or doesn't his?

The tannoys are just the amp and speakers in one - I don't see what that wouldn't work. Am I missing something obvious here?

Like, if the main faders are all the way down, he shouldn't hear anything. Then he can bring up the faders until he hears at the right volume. I've GOT to be missing something, this is too easy.
 
Now I'm confused as well:confused: I missed that it was active monitors.

I'm at a loss - again
 
On your "mixer" do you have a nob marked control room or monitor?Thats the place that you would usally start at..and there should be some type of monitor out jacks to plug into .Or maybe you could use a small resitance mixer from Radio Shack


Don
 
I'm going to make a guess. The mystery mixer has two sets of outputs: monitor and main. He's running the monitor output to powered monitors. He might be using the main outs for something else, like for recording. The same master fader controls both. So if you reduce the volume for comfortable listening levels, then the output to the recorder is too low.And it sounds like he wants to get the fader up to 0dB, perhaps for good recording volume.
The best thing would be to find out what kind of mixer it is. Maybe it has aux sends that could be used for monitoring. Or maybe there's some other creative way to use it. Anyway, this is all based on a guess.

Jim
 
Let´s see: you got mixer with line level stereo output and active monitors. Is this -10 dB or +4 dB mixer ? When you set mixer´s master fader at 0 dB, you get aprox. 1 V ( volt ) on line output. Active speakers are designed to give maximum loudness ( 0 dB ), when driven with aprox. 1 V on amp´s input ( standard ).
So, get one ALPS conductive plastic stereo potentiometer and insert it between mixer and monitors. This is called " passive preamp ", and this is Hi-Fi solution.
 
JimH got it. Yes, it has two outputs. They are both controlled by the same fader. So when I have it on 0db, it's to loud.

Now I have answers saying that "yes a potentiometer is OK" and answer saying that "no it isn't".

So, which is it?
 
Well, " passive preamp " is solution used by people which pay 300$ for 1 meter piece of interconnecting stereo cable. ;)
 
So thats the solution used by stupid hifi nuts who beleive anything a salesperson says, huh? :)

OK. I'll buy a stereo put and some connector and then I'll do a A/B test to see if I can hear any difference in sound. Any recommendations on what resistance I should use? The tannoys have 32k ohm inputs.
 
Well, tried it, and it didn't work, weirdly enough. Sure, the volume changes, but the high frequencies changes faster than anything else. I suspected that might happen, although it doesn't behave as I thought it would. In fact, the high frequencies get weaker when the total resistance increases, which is the opposite of what I had expected. Even with the volume down to half = a doubling of the total output resistance, the high frequency is clearly lower. Very weird. Anybody have an explanation for this?

I tried both the voltage divider setup (with the resistance in parallell over the input) and the increased resistance setup (with the resistance in series with the input). Both had the same effect: Lower volume = less highs.
 
OK I know we can help....but

OK I know we can help....but first tell us what brand of mixer you have?

What kind of outputs do you have (1/4", RCA, XLR ?)

What kind of monitors are you driving....

I bet it's something simple.... like you are trying to use a PA Powered mixer as a board... or just using the wrong output jacks.

Sincerely;

Dom Franco
 
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