Differential input amplifiers

[8ight]

I thought you meant balanced/differential...

[MrSkippyJ]

Some extremely high end (Denon, etc) head units have balanced outputs but most of the time you just use a transmitter like this http://www.ebay.com/itm/New-Zapco-SLDIN-T-Symbilink-/130567865573 or a line driver.

8ight- Thanks for that link. I'm currently running the soundstream reference amplifiers, and they have the option to run a symbilink-style balanced input. It is a 6-pin mini-din type connector that looks just like what you have posted above. Guess I'll be ordering a couple of those

>

Some higher end amplifiers have differential RCA inputs to isolate 12v to ground to help with noise.

Great technology, but do you have to have a head unit that will "output" a differential signal. If so, how can I tell?

Sorry if this is a dumb question, but I'm currently running coaxial RCAs on my amplifier with the RCA's at the head unit grounded to the head unit's chassis. (Gotta love pioneer)

Just looking to upgrade my cabling to twisted pairs if I can, thanks

My first question is why do you think that twisted pair cables are an "upgrade"?

Don't believe all the marketing hype that you see.

Your best cable option is the cable that properly transfers your available signal between the HU and amp/processor/etc.

For a balanced/differential signal to work properly, you need a HU that outputs that type of signal. You also need an amp/processor that accepts and processes the signal as well.

Will a system work if you mis-match parts, sure it could but you wont be getting full use of the noise cancelling ability of the twisted pair cable.

When used properly a coax cable will also have great noise reducing ability as well.

You mentioned Pioneer for a HU and that you may have the pico fuse issue. cabling can only do so much of other components are faulty.

As said above, very few HU's have balanced outputs, especially aftermarket ones. So you most likely have a single-ended HU.

As you saw in Tony D's video, the best option for that output is coax.

If you absolutely have to have twisted pair, then as mentioned above, you could get a converter to change your signal from one to another.

If you'd like to test for it then do the following:

Read your manual(s) and see if your equipment supports balanced/differential signals. If they do then the manuals should say so.....OR

Play a test tone on your HU at full volume (rest of the system disconnected obviously) or at least decent volume where you'll get a solid RCA output voltage to read.

Place the ground lead of your DMM on the HU's chassis. Set the DMM to Vac.

Probe the center conductor of your RCA pre-outs with the positive DMM lead (F, R, SUB RCA should all work assuming you have your settings flat and nothing is attenuated).

You should get a reading that is inline with your "rated" RCA output voltage if you use a 0dB test tone.

Now use the positive probe and look at the outside conductor of the RCA output.

If you have balanced/differential outputs then you should see the same signal voltage there as with the center conductor.

If you did see a signal on the outside conductor then you can also use the DMM probes between the outside and inside conductor of the RCA jacks and you should see double the voltage you did on the previous measurements.

Another check you could do is to set the DMM to ohms and measure the resistance between the outside of the RCA jack to the chassis of the HU. Make sure everything is Powered off, system disconnected).

If you have single-ended outputs then you should see a very low (~0.4 Ohm) reading.

If you have balanced/differential outputs then you should see a high resistance.

There is a catch though. If you have a "pico fuse" issue then the connection between your HU chassis and RCA outside conductor has been compromised so you'll get a false reading.

Great info here, thank you for the response. Why do I think twisted pair would be an upgrade? Because anything would be an upgrade over the el-cheapo dollar store type RCAs that I'm currently using. I guess I'll be ordering the symbilink type connector and running that.

Thanks

You are confusing the quality of the cable with the TYPE of cable. The el-cheapo dollar store cables are el-cheapo because they are shitty quality, not because they are the standard type of RCA cable. You can have shitty twisted pair cables too (or balanced or whatever the hell they are called).

[Wicks]

Some extremely high end (Denon, etc) head units have balanced outputs but most of the time you just use a transmitter like this http://www.ebay.com/itm/New-Zapco-SLDIN-T-Symbilink-/130567865573 or a line driver.

8ight- Thanks for that link. I'm currently running the soundstream reference amplifiers, and they have the option to run a symbilink-style balanced input. It is a 6-pin mini-din type connector that looks just like what you have posted above. Guess I'll be ordering a couple of those

Some higher end amplifiers have differential RCA inputs to isolate 12v to ground to help with noise.

Great technology, but do you have to have a head unit that will "output" a differential signal. If so, how can I tell?

Sorry if this is a dumb question, but I'm currently running coaxial RCAs on my amplifier with the RCA's at the head unit grounded to the head unit's chassis. (Gotta love pioneer)

Just looking to upgrade my cabling to twisted pairs if I can, thanks

My first question is why do you think that twisted pair cables are an "upgrade"?

Don't believe all the marketing hype that you see.

Your best cable option is the cable that properly transfers your available signal between the HU and amp/processor/etc.

For a balanced/differential signal to work properly, you need a HU that outputs that type of signal. You also need an amp/processor that accepts and processes the signal as well.

Will a system work if you mis-match parts, sure it could but you wont be getting full use of the noise cancelling ability of the twisted pair cable.

When used properly a coax cable will also have great noise reducing ability as well.

You mentioned Pioneer for a HU and that you may have the pico fuse issue. cabling can only do so much of other components are faulty.

As said above, very few HU's have balanced outputs, especially aftermarket ones. So you most likely have a single-ended HU.

As you saw in Tony D's video, the best option for that output is coax.

If you absolutely have to have twisted pair, then as mentioned above, you could get a converter to change your signal from one to another.

If you'd like to test for it then do the following:

Read your manual(s) and see if your equipment supports balanced/differential signals. If they do then the manuals should say so.....OR

Play a test tone on your HU at full volume (rest of the system disconnected obviously) or at least decent volume where you'll get a solid RCA output voltage to read.

Place the ground lead of your DMM on the HU's chassis. Set the DMM to Vac.

Probe the center conductor of your RCA pre-outs with the positive DMM lead (F, R, SUB RCA should all work assuming you have your settings flat and nothing is attenuated).

You should get a reading that is inline with your "rated" RCA output voltage if you use a 0dB test tone.

Now use the positive probe and look at the outside conductor of the RCA output.

If you have balanced/differential outputs then you should see the same signal voltage there as with the center conductor.

If you did see a signal on the outside conductor then you can also use the DMM probes between the outside and inside conductor of the RCA jacks and you should see double the voltage you did on the previous measurements.

Another check you could do is to set the DMM to ohms and measure the resistance between the outside of the RCA jack to the chassis of the HU. Make sure everything is Powered off, system disconnected).

If you have single-ended outputs then you should see a very low (~0.4 Ohm) reading.

If you have balanced/differential outputs then you should see a high resistance.

There is a catch though. If you have a "pico fuse" issue then the connection between your HU chassis and RCA outside conductor has been compromised so you'll get a false reading.

Great info here, thank you for the response. Why do I think twisted pair would be an upgrade? Because anything would be an upgrade over the el-cheapo dollar store type RCAs that I'm currently using. I guess I'll be ordering thhe symbilink type connector and running that.

Thanks

We could get into lots of detail about cables but there's a fundamental question that we should answer first.

Do you actually have noise that you need to eliminate?

Just because your equipment supports a feature, it doesn't mean you have to use it.

Don't get me wrong, if you want to utilize your equipment's best feature that's great and there's nothing wrong with that. I'm just going over all the options.

[79Bronco]

Do I have noise? Yes.

It's very slight, and you really have to strain to listen to it, almost like pink noise (usually at full tilt.) Definitely not alternator whine or anything like that.

Gains set with an oscope, so I know that's not the problem.

Grounded my head unit properly and RCA's grounded to head unit.

I'm running a fully active setup with a 3 way front stage and I think opting for decent cables is my next step.

[Wicks]

Hmmm, a low level static-type noise may be something else.

That might originate in the HU itself or the amp.

In that case, cables won't do anything because you'd be transmitting noise and not having it coupled into your signal.

The Soundstream's have balanced inputs but that's a whole different connector interface.

Out or curiosity, disconnect your RCA's from the amp and measure the resistance between the ground input and the outside connectors of your RCA jacks on the amp.

For coax to work properly, it needs to be grounded on both sides (HU and amp).

Another test would be to use a portable music player (iPod) and plug it directly into your amp with a separate RCA cable which isn't installed in your vehicle (away from power wires and other things that could be adding noise).

If the noise is gone then there's a chance its coming from the HU.

[bassinyerface]

I know a tad about PA systems and such. As I have a realatively elaborate DJ setup. Balanced outputs have 3 main purposes 1. They can be powered so long runs are possible. 2. Noise cancelation and 3. And the fact it can also be digitaly monitered threw a pass threw device. So for instance a clip meter or what I have built in vu meter that runs to my cabinet's. Let's me know that my signal is getting passed threw the same. Idk thats my inderstanding but I could be wrong