Behringer dsp1124 hiss

[nm2285]

I just hooked up my parametric EQ and am encountering a hiss which is easily audible with no music playing and also easily audible in quiet to medium passages or music/movie. I have it hooked up to my NAD C370 - pre-outs of the NAD to the EQ and EQ to the Main-in of the NAD. I'm using an RCA to 1/4" cable. When I hook up my Alesis M-EQ230 (graphic EQ) there is no significant hiss. Any idea how to lessen the hiss?

It occurs to me that I need to either boost the input level, decrease the outpul level, or both. How do I accomplish either/or?


Also, when I turn the volume on my amp all the way down, I can still here the music at a low volume (and of course the hiss). Will decreasing the output of the EQ fix this?

-Nick

 

[WmAx]

I just hooked up my parametric EQ and am encountering a hiss which is easily audible with no music playing and also easily audible in quiet to medium passages or music/movie. I have it hooked up to my NAD C370 - pre-outs of the NAD to the EQ and EQ to the Main-in of the NAD. I'm using an RCA to 1/4" cable. When I hook up my Alesis M-EQ230 (graphic EQ) there is no significant hiss. Any idea how to lessen the hiss?

It occurs to me that I need to either boost the input level, decrease the outpul level, or both. How do I accomplish either/or?


Also, when I turn the volume on my amp all the way down, I can still here the music at a low volume (and of course the hiss). Will decreasing the output of the EQ fix this?

-Nick

On the back of the Behringer, you will find two small buttons, one near each output. These switch the output voltage to match either professional or consumer gear. You need to switch to consumer level voltage output.

-Chris

 

[nm2285]

I've done this. Although it does make the hiss quieter (or louder) even on the consumer setting, its unreasonably loud. Any other suggestions?

 

[WmAx]

I've done this. Although it does make the hiss quieter (or louder) even on the consumer setting, its unreasonably loud. Any other suggestions?

It sounds like the unit is still providing too much gain for your main amp inputs. The solution in that case is to install a potentiometer between the Behringer outputs and the amplifier inputs so that you can reduce the output voltage further, and at the same time allow greater voltage to be applied to the Behringer inputs(because you will be using a higher volume control position on the preamp). Note: This assumes you are not presently inputing enough voltage to make the level LEDs on the Behringer go near the top of their range.


-Chris

 

[nm2285]

No, I haven't approached clipping yet. Any suggestions on a potentiometer?

thanks for the help

 

[nm2285]

I haven't tried it yet, but I assume I could use the graphic EQ I have (the M-EQ230) as a "potentiometer" and just lower the gains on both channels, is this correct?

I'd still rather sell that guy and get a dedicated one if the price is better. Let me know of any that will work for me.

 

[Malice]

Look at this thread...

http://www.nextlevelav.com/forum/showthread.php?t=733

It is in a forum section dedicated to the BFD.

HTH

EDIT: Also a few pointers can be found here http://www.avforums.com/forums/showthread.php?t=268513&highlight=residual

 

[WmAx]

Look at this thread...

http://www.nextlevelav.com/forum/showthread.php?t=733

It is in a forum section dedicated to the BFD.

The guy above is not having an issue with a ground loop(60Hz hum), which is the subject of the linked thread.

-Chris

 

[WmAx]

No, I haven't approached clipping yet. Any suggestions on a potentiometer?

thanks for the help

A standard 50k dual-ganged potentiometer, with short cables running between it and the hardware(capacitance of the cable is an issue, so keep cables short to avoid this being an issue). If you need specific instructions(I'm assuming you know how to connect a potentiometer), just ask.

-Chris

 

[WmAx]

I haven't tried it yet, but I assume I could use the graphic EQ I have (the M-EQ230) as a "potentiometer" and just lower the gains on both channels, is this correct?

Certainly you can try it. But in the end, you'll want to go ahead and install the in-line attenuator(potentiometer) for simplicity and minimum noise.

I'd still rather sell that guy and get a dedicated one if the price is better. Let me know of any that will work for me.

It's not clear to me what you mean in this statement. A dedicated what?

-Chris

 

[nm2285]

Certainly you can try it. But in the end, you'll want to go ahead and install the in-line attenuator(potentiometer) for simplicity and minimum noise.



It's not clear to me what you mean in this statement. A dedicated what?

-Chris

I just meant that I'd rather get a true potentiometer, not a substitute for one. I could probably figure out how to install one, but having never used/seen one before, some more tips would really be appreciated (cause at the moment I'm basically cluless). Thanks again for the assistance.

 

[nm2285]

I've been checking them out a bit and have a few questions.

50K is the load? Why 50?
What is dual vs single ganged?
Audio controlled or linear-tapered (whats the difference)?
What kind of watt tolerance is needed in the run between EQ and amp?

I see this:
http://www.radioshack.com/product/index.jsp?productId=2062359&cp=&pg=2&kw=potentiometer&parentPage=search
but 1) don't know how to install it and 2) don't know if it meets specifications (i read somewhere it's rated for 0.05 watts). Does it need an enclosure?

How about volume controls such as part$expre$$ part #300-523?

 

[WmAx]

50K is the load? Why 50?

I recommend 50k as a general solution value in passive attenuators in-line, because this value is most widely compatible concerning source impedance, load impedance, and cable capacitance issue(s).

What is dual vs single ganged?

Ganged lets you adjust both channels in unison. The alternative is two seperate single potentiometers which you must then match with each other manually.

Audio controlled or linear-tapered (whats the difference)?

It does not matter for your application. But FYI, an audio taper is just the proportionate value of attenuation within a specific turn ratio to better match the motion/degree of turn to the amount of volume change that you percieve when adjusting. It's useful for actual volume controls on a preamplifier where you use it as such, but for a seldom used attenuator, it makes no difference.

What kind of watt tolerance is needed in the run between EQ and amp?

Not an issue. Any rating will work in this application.

http://www.radioshack.com/product/index.jsp?productId=2062359&cp=&pg=2&kw=potentiometer&parentPage=search
but 1) don't know how to install it and 2) don't know if it meets specifications (i read somewhere it's rated for 0.05 watts). Does it need an enclosure?

Enclosure is optional. You can solder wires right to it if you want. This 100K value make work fine in your application. Provide me with the output impedance of the Behringer and input impedance of the amplifier and I can calculate the response for you. Or, I can just mail(assuming you are in the U.S.A.) you an Alps 50k dual-ganged pot if you prefer. As for connection, you do the same for L and R channels. As for connection, here is more than you ever wanted to know, including how to connect them: http://sound.westhost.com/pots.htm

How about volume controls such as part$expre$$ part #300-523?

This is not the correct part for the application. This is a speaker volume control.

-Chris

 

[nm2285]

From stereophile review for the NAD:
"Input impedance at 1kHz was 300k ohms..."

Output impedance from the Behringer: 30 ohms

Let me know what the response would be

 

[nm2285]

I picked up the volume control from radioshack. It has the 3 prongs for each channel as seen on the website that you posted on potentiometers (1 for in, 1 for out, 1 for ground). There is also one more prong for each channel on the opposite side from the 3 others.
What are these 2 prongs for?

Also, the NAD and the Behringer do not have grounds. Any problem connecting the ground to an unassociated equipment?

 

[nm2285]

Anyone able to answer the above Q?

 

[WmAx]

From stereophile review for the NAD:
"Input impedance at 1kHz was 300k ohms..."

Output impedance from the Behringer: 30 ohms

Let me know what the response would be

I was going to calculate various positions for the pot vs. the input impedance, but that(300 kOhm) is a very high input impedance(this is a good thing). No sense in calculating, you should be fine with that pot and input impedance. Just use short cables to connect.

-Chris

 

[WmAx]

I picked up the volume control from radioshack. It has the 3 prongs for each channel as seen on the website that you posted on potentiometers (1 for in, 1 for out, 1 for ground). There is also one more prong for each channel on the opposite side from the 3 others.
What are these 2 prongs for?

I'de have to see a pic of the potentiometer. It might be a combination volume control-on/off switch. Does the pot click on and off at it's far left position? Just ignore the extra tabs.

Also, the NAD and the Behringer do not have grounds. Any problem connecting the ground to an unassociated equipment?

Ground is the outer sheild of the coax cable(or the outside metal sleeve of the RCA plug/jack if you want to look at it that way) on the Nad. On the Behringer XLR jacks, ground is pin 1 of the XLR. You should connect pins 1 and 3 together in the XLR plug when using with unbalanced connection if you are making up a custom cable. If you are using a RCA-XLR adapter, it should do this internally.

-Chris

 

[nm2285]

heres a pic of the pot. i labelled the prongs. If you could list the correct connections, that would be a huge help. eg: 1 - right positive, 2 - ...

and especially: what are 7 and 8 for?

it does not click when turned all the way in either direction

-nick

 

[WmAx]

heres a pic of the pot. i labelled the prongs. If you could list the correct connections, that would be a huge help. eg: 1 - right positive, 2 - ...

and especially: what are 7 and 8 for?

it does not click when turned all the way in either direction

-nick

Example: Connect from source to pin 3, output to amp pin 2, ground from both source and to amp are connected at pin 1. Repeat for the other channel on the bottom pins. I'm not sure what the orientation of this pot is(pins up or down), but the worst that would happen with reverse order is that the volume gets quieter as you turn to right instead of the other way around. As always, use very short cables.

I am not sure what the additional pins are for. It might be tapped for a loudness control circuit, but it's not important. Just ignore the extra pins; don't connect anything to them.

-Chris