I saw this video from D'Amore and was wondering what everyone thought about it?

Are there other installments to this series?  It appears his description is incomplete.

 

This first problem with his description is that in order for the signal to be balanced, which is what he's describing for the differential input with the phase inverted signal, is that the source must output a balanced signal with a phase inverted signal.  And that is extremely rare these days.  I can only imagine the number of kids watching that video who are going to automatically assume because they see "differential input" as a feature of their amplifier that their system is operating as he's describing.  Doesn't work that way.  You need a source that transmits a balance signal and an amplifier that accepts that balanced signal, such as one with differential balanced inputs. 

 

Unless you are actually using a balanced signal transfer (source outputs a balanced signal), then standard shielded cables are what you need.  Just because your amplifier has differential inputs does not mean you are using a balanced system.  Even if your amplifier has differential inputs, if your source does not output a balanced signal then you still want shielded cables.  If you by chance are running a balanced system with the method described in the video then yes, twisted cables are what you want.

He has a lot of videos up, click here for all of them.

Well, I didn't see any other videos that this could be an installment from.  As such......he's not "wrong", but all of the necessary information isn't presented to allow the novice this was presumably targeted at to completely understand the information.  As I said in my prior post......having differential inputs on the amplifier doesn't mean you are running the type of system he is talking about in that video.  That said I agree with his premise.....unless you are running balanced, you are better off with shielded cables.

Oh I see what you mean now, yea I don't think he has anymore about RCA cables specifically. 

Are there other installments to this series?  It appears his description is incomplete.

 

This first problem with his description is that in order for the signal to be balanced, which is what he's describing for the differential input with the phase inverted signal, is that the source must output a balanced signal with a phase inverted signal.  And that is extremely rare these days.  I can only imagine the number of kids watching that video who are going to automatically assume because they see "differential input" as a feature of their amplifier that their system is operating as he's describing.  Doesn't work that way.  You need a source that transmits a balance signal and an amplifier that accepts that balanced signal, such as one with differential balanced inputs. 

 

Unless you are actually using a balanced signal transfer (source outputs a balanced signal), then standard shielded cables are what you need.  Just because your amplifier has differential inputs does not mean you are using a balanced system.  Even if your amplifier has differential inputs, if your source does not output a balanced signal then you still want shielded cables.  If you by chance are running a balanced system with the method described in the video then yes, twisted cables are what you want.

 

alright, thanks for the information.

 

he also posted this in the comments,

"If the head unit has SE outputs and the amplifier has SE inputs = coax cable

If the head unit has SE outputs and the amplifier has Diff inputs = twisted pair

If the head unit has Diff outputs and the amplifier has Diff inputs = twister pair

If the head unit has Diff outputs and the amplifier has SE inputs =

bad no matter what as you will shorting out half of the head unit's

outputs. In this case you would need an amplifier with Diff inputs or a

converter to convert the head unit's outputs to SE"

 

Show me the schematic of an amplifier that has true differential inputs on an RCA connector... 

 

The only car audio amplifiers I have installed that had differential inputs were Butlers, and they had XLR connectors, of course...  Some Adcom and Macintosh gear ran differential signal I/O, but again, on XLR connectors...

Show me the schematic of an amplifier that has true differential inputs on an RCA connector... 

 

The only car audio amplifiers I have installed that had differential inputs were Butlers, and they had XLR connectors, of course...  Some Adcom and Macintosh gear ran differential signal I/O, but again, on XLR connectors...

 

jl advertises the hd and xd series as differential-balanced inputs. is that a case of false advertising or are they half assing the design?

Show me the schematic of an amplifier that has true differential inputs on an RCA connector... 

 

The only car audio amplifiers I have installed that had differential inputs were Butlers, and they had XLR connectors, of course...  Some Adcom and Macintosh gear ran differential signal I/O, but again, on XLR connectors...

The original PDX amps were confirmed by werewolf to have differential inputs per the service manual back in the ECA days.

 

The designers at JL and JBL are pretty smart cookies....from the posts from Manville and Andy, respectively, I would readily believe the amps they indicate to have differential inputs truly do. 

 

Seems like of all of the things to falsely advertise, differential inputs would be a bad choice given the first time someone tries to drive it with a balanced signal and the amp goes pop, there would be a lot of liability there.  From what I found skimming threads a while back some BMW systems use balanced line level signal transmission and people have been splicing in directly to the OEM system by using amps with differential inputs.

I have read about some companies claiming differential balanced inputs on RCA's, but it just doesn't make any sense.  You just can't exploit the benefit of differential transmission with an RCA connector, never mind the fact that most sources are not balanced, so that actually makes things worse if you truly have a balanced amplifier input. 

 

My guess is they may be running some kind of quasi-balanced input, I just don't see the reasoning behind true differential balanced signal on single ended connectors, with single ended sources.  I think it is more off an attempt to float the input cutting down on ground loops than differential operation...

 

All truly balanced equipment I have dealt with has truly balanced I/O connectors, be it XLR, Phoenix or barrier strips, never RCAs...

 

I would have to see a schematic of the amplifier to see if it is truly balanced, but that is pretty tough to get sometimes, so I will probably keep my BS flag up on this one until shown otherwise...

Show me the schematic of an amplifier that has true differential inputs on an RCA connector... 

 

The only car audio amplifiers I have installed that had differential inputs were Butlers, and they had XLR connectors, of course...  Some Adcom and Macintosh gear ran differential signal I/O, but again, on XLR connectors...

The original PDX amps were confirmed by werewolf to have differential inputs per the service manual back in the ECA days.

 

The designers at JL and JBL are pretty smart cookies....from the posts from Manville and Andy, respectively, I would readily believe the amps they indicate to have differential inputs truly do. 

 

Seems like of all of the things to falsely advertise, differential inputs would be a bad choice given the first time someone tries to drive it with a balanced signal and the amp goes pop, there would be a lot of liability there.  From what I found skimming threads a while back some BMW systems use balanced line level signal transmission and people have been splicing in directly to the OEM system by using amps with differential inputs.

Yeah, I just don't see the logic here.  It is pointless to have differential inputs driven by a single ended source.  I can cause a myriad of problems.  That is why I wonder if it is some kind of modified/quasi balanced circuit.  RCAs were never intended to be a part of a balanced signal chain.  This is why I think there is some BS going on here.

 

All circuits are differential at some point in a push-pull amp, anywhere past the splitter/inverter is balanced, there can be some creativity in how this is described to the customer. 

My PPI amp has balanced input stage, but they are not RCA connectors.  Being as I don't have a balanced ouput I just run normal RCAs.

 

And while on the subject of RCA cables and noise, DC (i.e. power cable) will not induce noise running next to the signal cables.

I would also like to see a car audio source with RCAs and identical phase inverted signals on the outer shell and inner pin...  Just don't see it happening, but I could be wrong... 

 I think it is more off an attempt to float the input cutting down on ground loops than differential operation...

I believe you hit the nail on the head.  The goal is to limit ground loop noise than actually isolate noise during the sound transmission.

 

As an aside - My old Coustic DR amps accepted balanced input via dual RCA inputs per channel.

My PPI amp has balanced input stage, but they are not RCA connectors.  Being as I don't have a balanced ouput I just run normal RCAs.

 

And while on the subject of RCA cables and noise, DC (i.e. power cable) will not induce noise running next to the signal cables.

 This is what I am getting at, the truly balanced signal components do not pass those signals on RCAs.  They use connections and cabling specifically designed for differential transmission.

 

DC won't induce noise, correct.  Any AC component that is also on your DC cable (alternator ripple, ignition harmonics) can be induced on to your signal cables, but it is normally so low in magnitude, it never gets anywhere...

As an aside - My old Coustic DR amps accepted balanced input via dual RCA inputs per channel.

 

-And that makes perfect sense...