Can I add an amp to Honda head unit (stereo) ?

[brianl703]

Originally Posted By: digitalSniperX1


Differential amplifiers have two output devices also, but they continuously drive in opposing polarities to each other, with what I'll call a "non-physical ground". "assumed ground" or "virtual ground" between them.


That perfectly describes the output of most car head unit amplifiers..and is why the speaker outputs are not to be grounded.

 

[brianl703]

This is what the amplifier circuit in most headunits looks like. Note that the signal is fed into the inverting input of one amplifier and the non-inverting input of the other ampliifer, and the signal coming out of one amplifier is a mirror image of the other.

This will work with ANY class of amplifier.

 

[digitalSniperX1]

Well, if that's the most common configuration, I stand corrected. I would not have thought so.

I was thinking you may've been confusing differential with complementary. Clearly you are not.

But, for example, my Yamaha RX-V1 schematic shows a classic complementary output stage where the NPN device is tied to a 46.8 volt rail and the PNP device is tied to a -46.8 volt rail. Both emitters drive the positive speaker terminal (and a negative feedback circuit), and the negative speaker terminal is capacitively coupled to ground (i.e. AC ground).

And it was definately not cheap (orig retail price $3200 US).

I'd include a jpeg of it if I knew how, LOL (too lazy to figure it out).

 

[digitalSniperX1]

Too late to edit..but it makes sense they are differential..I think the following makes sense (mostly).

Ok, I think we're referring to CAR stereo amplifiers. Makes perfect sense to make them differential outputs since a lower voltage rail is required to produce higher power. Without a complicated power supply (but with enough capacitance to produce a -12 volt rail) you could achieve close to 24 volts p-p at the speaker terminals.

Ok, sorry for hijacking the thread. Hopefully this discussion is of interest to others.

 

[brianl703]

Yes, this configuration allows ~20W per channel instead of the ~5W per channel that a single-ended output design would allow, with the same supply voltage.

It used to be that many stock car headunits and cheaper aftermarkets used the single-ended design.

It's not like that anymore..pretty much everything, stock or aftermarket, with very few exceptions uses the differential design for more output power at a relatively low additional cost (I guess maybe $2-$3, certainly much lower than going to the next step of using a step-up switching power supply to increase the ~12V to something higher).

There isn't much use for type of design in units designed for 120V wall power, although I am told that some very high power PA amps use this design too, probably again in lieu of a step-up power supply. (You might think they could use a step-up power transformer since it's AC, but the silicon may well be cheaper than a big transformer..)