stereo hissing after eq install

[Earmark Marine]

Thats how I tuned it at first. To get it real loud I end up turning the main volume to about 3/4 and the in boat to about 60%. It is VERY LOUD.

Should I turn the EQ volumes up and the source down? The iPod volume is at about 80%.

Also I'm dissapointed the 420sq doens't have a sub crossover, it only has a volume knob. The old 420 had both volume and crossover.

It never had a crossover. Why would you want a lowpass crossover when the amplifier already has one? Previously it had a paragraphic bass tone control (altered turnover frequency and amplitude) that was replaced with a dedicated bass level control.

David

[Earmark Marine]

The ipod should be at 90% output unless you can detect some form of distortion which is unlikely into such a high input impedance versus a headset or earbuds. I prefer the true preamp output.

The EQ internal input sensitivity should be left at the factory setting unless you have a gain inequity between the main and auxilary source.

The EQ master volume and separate zone volumes should be at 90%. You want just a little extra bit of headroom in case you have a song, artist or download that is a weaker recording.

The amplifier gains shouldn't be more than 50% in most cases especially with this much output voltage from the EQ.

This by no means is the way to tune a system for maximum performance. But it is a good start for getting down to the normal level of ambient hiss.

If your amplifier inputs are shorted and you are at 50% input gain then all hiss is owned by the amplifier.

If all EQ inputs are shorted then any additional hiss is owned by the EQ.

Same with the source unit.

Work the signal path in reverse.

All processors will add some small degree of hiss unless the gains are mismanaged to eliminate all hiss. You have to strike a balance between a low noise floor and decent dynamic range.

And try that internal ground switch for sure.

David

[FastFreddy]

The ipod should be at 90% output unless you can detect some form of distortion which is unlikely into such a high input impedance versus a headset or earbuds. I prefer the true preamp output.

The EQ internal input sensitivity should be left at the factory setting unless you have a gain inequity between the main and auxilary source.

The EQ master volume and separate zone volumes should be at 90%. You want just a little extra bit of headroom in case you have a song, artist or download that is a weaker recording.

The amplifier gains shouldn't be more than 50% in most cases especially with this much output voltage from the EQ.

This by no means is the way to tune a system for maximum performance. But it is a good start for getting down to the normal level of ambient hiss.

If your amplifier inputs are shorted and you are at 50% input gain then all hiss is owned by the amplifier.

If all EQ inputs are shorted then any additional hiss is owned by the EQ.

Same with the source unit.

Work the signal path in reverse.

All processors will add some small degree of hiss unless the gains are mismanaged to eliminate all hiss. You have to strike a balance between a low noise floor and decent dynamic range.

And try that internal ground switch for sure.

David

Ok thanks for the tips David. Just to clarify the hiss is not background noise, the hiss is a fluctuating noise which is fairly high pitched it seems to cycle up and down fairly slowly, maybe every 30 seconds or so. There is a small amount of background/white noise when the subwoofer amp is not connected with RCAs but that is not what I am complaining about, that noise I know is normal.

What I call a hiss sounds a bit like a distant 2 stroke dirtbike slowly cycling between power and coasting. Hard to explain...

[FastFreddy]

It never had a crossover. Why would you want a lowpass crossover when the amplifier already has one? Previously it had a paragraphic bass tone control (altered turnover frequency and amplitude) that was replaced with a dedicated bass level control.

David

I sometimes liked adjusting the crossover on a head unit even though my amp was set to a high crossover level. I listen to different types of music and I like to filter out some "high" bass on hip-hop but like the high bass on punk music. Just my preference.

If I can get rid of the hissing then I'm sure I'll love this EQ.

[Earmark Marine]

I would describe 'hiss' as a constant white noise (across a fairly wide treble range) like the sound of a distant waterfall....like, "Shhhhh". This is also called thermal noise. All my previous comments relate to 'hiss'.

If there is something that fluctuates at all then it is something else from a boat management module or a boat operation (alternator, ignition, etc.) or from the amplifier high speed switching power supplies. 90% of this 'something else' is a product of a supply or ground loop that should not exist and should be corrected in the installation. 10% is caused by poor gain matching.

If the boat systems are totally powered down because the key is 'Off' or you disabled the helm buss breaker then the noise is coming from within the audio system. If it appears when the boat systems are engaged or the key is switched to acc/ign then the source is a boat function. However, neither should have a route into the audio signal path.

Btw, not a fan of changing the crossover point AFTER the system has been tuned. That creates either a null or overlap between the high and lowpass filters because you are not changing both simultaneously. Each high and low filter goes through it's own phase rotation so that is an element that I want to remain consistent as I originally set it up. The way I tune a system it definitely matters.

David

[FastFreddy]

I would describe 'hiss' as a constant white noise (across a fairly wide treble range) like the sound of a distant waterfall....like, "Shhhhh". This is also called thermal noise. All my previous comments relate to 'hiss'.

If there is something that fluctuates at all then it is something else from a boat management module or a boat operation (alternator, ignition, etc.) or from the amplifier high speed switching power supplies. 90% of this 'something else' is a product of a supply or ground loop that should not exist and should be corrected in the installation. 10% is caused by poor gain matching.

If the boat systems are totally powered down because the key is 'Off' or you disabled the helm buss breaker then the noise is coming from within the audio system. If it appears when the boat systems are engaged or the key is switched to acc/ign then the source is a boat function. However, neither should have a route into the audio signal path.

Btw, not a fan of changing the crossover point AFTER the system has been tuned. That creates either a null or overlap between the high and lowpass filters because you are not changing both simultaneously. Each high and low filter goes through it's own phase rotation so that is an element that I want to remain consistent as I originally set it up. The way I tune a system it definitely matters.

David

Ok so my description of a hiss is definitely wrong. The sound is there with the key OFF so it's not an alternator noise, fuel pump or anything else but it is also not the white noise. If I plug the iPod directly to the amp there is some white noise or slight continuous "SHHHHHHH", that's not what I am noticing after the EQ install.

You say that "90% of this 'something else' is a product of a supply or ground loop that should not exist and should be corrected in the installation" and I'm pretty sure this is my problem. Since it only happened after the EQ install I'd have to think it is the power or ground supply. I'll rewire the EQ directly to the battery and see if that helps.

One thing I was wondering is if it is possible that the sound is coming from the blue switch wire? Does it matter how it is wired? Currently it comes from the factory head unit location, splits into two, one to the EQ, the other to the sub amp, from the sub amp connection it splits again, one wire to each of the other amps. Should I use a distribution block for the switch wire?

Edited June 6, 2013 by FastFreddy

[FastFreddy]

Could excessive fusing cause this?

The power runs as such. First to the distribution block for the amp, 60 amp fuse. Then to a smaller distribution block under the helm 5 amp fuse, then to the EQ which also has it's own fuse. The reason for this is I wanted to add a distribution block under the helm for other power requirements. Currently there is nothing other than the EQ connected to this smaller block. I might try taking that out of the equation.

[Earmark Marine]

The remote turn-on lead should not affect the audio signal. It's outside the path. However, for completely different reasons I recommend that you use a relay when turning on three or more components. The draw per component is only 0.05 of an amp max and most source units are rated for .350 amp draw on this lead. But if you make a small error this is an extremely expensive HU repair compared to the low cost of a relay/socket.

All audio component grounds must go to a common point close to the amplifiers. The same goes for a common point for the B+ supply including the memory. Typically the amplifiers are close to the battery anyway. But my important reference is for all audio components in the signal path.

David

[shawndoggy]

relay that remote turn on.

[FastFreddy]

I don't think I need to relay the remote turn on since I am not using a head unit at all. I am using the factory stereo switch on/off from the dash which I'm sure is higher powered than the regular head unit remote wire.

I can't remember the last time I listened to a CD.

Main will be iPod and the Aux will be my satellite radio.

Thanks David, so the remote turn-on can not introduce interference. I have a list of things to try tonight. I feel like I will find the problem for sure now.

[shawndoggy]

Ahhh, yeah no relay needed.

[Earmark Marine]

Yeah, if you are using a 15 amp marine switch you do not need a relay. But I would still fuse it at the source as with all other circuits.

Okay, so no head unit. You may have to tweak the internal EQ input since it normaly sees a gain level from a HU twice that of an ipod.

David

[nyryan2001]

Freddy- where do you currently have the EQ wired to for power, ground and remote?

I about to hook up a ZLD to mine... I plan to power/ground/remote it right off the Amp lugs for the tower speakers. Anyone see a problem with that?

[Bawshogg]

Go to the distro block with power and ground. That way you are insured power and ground are all from the same exact location/ source. The remote wire can be pulled off an amp lead.

[FastFreddy]

Ok the distortion is fixed. I'm not sure which of these things fixed it but it is gone now.

1. Opened up the EQ and changed the jumper to ground isolate.

2. Added dielectric grease to fuse holder for the EQ

3. Soldered all the connections instead of crimped.

I'm 95% sure it was the jumper in the EQ that did it. I had the wires crimped just to test things out before soldering so I was going to do that anyways. I always prefer to solder my connection over crimping. Much cleaner look.

The EQ still has a bit of what I call white noise but it is acceptable to me.

I played with the EQ some more and I really like all the functions on it!