Noob question: how do I build this simple set-up?

[oysterman]

I'm looking to replace my head unit and it seems my old Alpine CDA-9832RB, rated at 60w per channel, was one of the more powerful units on the market. I have Polk Audio MM651 UM 100w speakers so ideally I am looking for a head unit with 100w per channel. If this is not feasible/cost effective, then I could look at an amp, but I live on a boat and power consumption is an issue.

More to the point, the unit needs to have two aux inputs (RCA) so either of them can benefit from the four speakers. The Alpine uses a KCA aiNet box that allowed me two separate aux inputs that I could control from the head remote, but I don't think Alpine make head units with the aiNet input any more (is that correct?).

I'm after something like this:

The two sources are two PCs, so they'll be RCA connections.

Questions:

1. What recommended head unit is rated at 100w per channel, with four channels and two aux inputs?

2. If head units don't come with 100w per channel, is there an alternative to the Alpine ai-net splitter out there?

3. If I buy an amp, can I by-pass it by not switching it on? That is, does the audio signal pass through the amp without being amplified?

4. Have I got my maths right with the wattage rating, or is 60w per channel the max I can go with 100w speakers?

Any help appreciated, thanks.

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[Boomin_tahoe 5,000+ posts]

Hu's don't have 100w x4. Amps do.

 

[garychoffmann 10+ year member]

Your old alpine wasn't actually 60x4. Head units are normally limited to 10-15 watts per channel. The 50x4, 60x4 are more marketing gimmicks of the power it can produce for milliseconds under optimal conditions. That being said if you were happy with it's output any headunit will probably do. If your input is from computers could you use usb inputs? Many head units have usb inputs and aux inputs.

 

[Water Bear]

What he said. I've never seen or heard of a head unit exceeding maybe 10 or 15 watts per channel. That 60 was a "max" rating, almost for sure.

If you're worried about current draw, use a class D amp. They're more efficient. For example this one:

Alpine MRV-F300

50x4 at 4 ohm class D. Shouldn't drain even the smallest charging system.

Also what's the story with the 2 front AUX inputs? These days most head units have 1 AUX in the front and then a USB.

 

[Water Bear]

I'm after something like this:

The two sources are two PCs, so they'll be RCA connections.

It is possibly to directly connect thumb drives or hard drives via USB to most head units these days. Is that an acceptable solution?

Questions:

1. What recommended head unit is rated at 100w per channel, with four channels and two aux inputs?

No head unit does this. You'll need an amp. There are plenty with more than one USB input, but not both on the front. Similarly there are plenty with 1 AUX on front and 1 in back, but not both on front.

2. If head units don't come with 100w per channel, is there an alternative to the Alpine ai-net splitter out there?

Not that I know of. There may be some sort of Y-connection which can take 2 AUX inputs into one, but obviously you won't be controlling that with a remote.

3. If I buy an amp, can I by-pass it by not switching it on? That is, does the audio signal pass through the amp without being amplified?

No. If the amp is turned off it won't output any signal. You can set the amp gain to 0, which will cause its output voltage to equal or be very near its input voltage, ie no amplification. This could be achieved with a remote gain control knob.

4. Have I got my maths right with the wattage rating, or is 60w per channel the max I can go with 100w speakers?

You can go at least to 100 watts with 100w RMS speakers. You can probably safely exceed that by a little.

See red text answers.

 

[oysterman]

Your old alpine wasn't actually 60x4. Head units are normally limited to 10-15 watts per channel. The 50x4, 60x4 are more marketing gimmicks of the power it can produce for milliseconds under optimal conditions. That being said if you were happy with it's output any headunit will probably do. If your input is from computers could you use usb inputs? Many head units have usb inputs and aux inputs.

Thanks for the info. The hard drives are powered externally, not USB powered, if that makes a difference. A lot of my music is in different formats and my understanding is that many of these units only read certain formats. Also I'm using a specific android app that controls a Windows media player (foobar), not via the unit itself.

 

[oysterman]

What he said. I've never seen or heard of a head unit exceeding maybe 10 or 15 watts per channel. That 60 was a "max" rating, almost for sure.
If you're worried about current draw, use a class D amp. They're more efficient. For example this one:

Alpine MRV-F300

50x4 at 4 ohm class D. Shouldn't drain even the smallest charging system.

Also what's the story with the 2 front AUX inputs? These days most head units have 1 AUX in the front and then a USB.

Apologies if my diagram confused you. The two aux inputs are not at the front, I was looking for something I could plug into from the back.

The two aux units are computers, one to run movies and a low powered mini stick pc to run music (this would be on most of the time). Currently I have one nuc doing all the work but I'm trying to reduce standby power consumption.

 

[oysterman]

See red text answers.

Thanks for that, Water Bear. You've confirmed a couple of things for me and provided some food for thought. It's a shame Alpine no longer produce the ai-net link. It has two aux inputs, which was really useful.

 

[oysterman]

What he said. I've never seen or heard of a head unit exceeding maybe 10 or 15 watts per channel. That 60 was a "max" rating, almost for sure.
If you're worried about current draw, use a class D amp. They're more efficient. For example this one:

Alpine MRV-F300

50x4 at 4 ohm class D. Shouldn't drain even the smallest charging system.

Also what's the story with the 2 front AUX inputs? These days most head units have 1 AUX in the front and then a USB.

BTW, thanks for the link to the amp. If I do buy one, this will probably be it. Cheers.

 

[Jcsaudio]

Sony is the only one that I know of that makes a head unit with a built in 40 watts per channel of real RMS power, not inflated peak numbers. In fact I think they have a double din radio with an internal amplifier putting out 45 watts per channel RMS x 4 now. Forget peak power numbers as they are a marketing gimmick and mean nothing. RMS power is what you want to use and the closer you get the RMS power to the top range RMS power your speakers are rated for the better.

 

[oysterman]

Been giving this a little more thought. I can get away with a single aux in because I can just use an rca splitter. If I buy an amp then how much did the HU matter? For example I came across this Boss unit https://www.crutchfield.com/p_104560BRGB/Boss-560BRGB.html?tp=72310

That rigged up to the previously mention Alpine amp, is that good or bad? I really don't know much about HUs so I've no idea whether a set up like this would work.

Any thoughts?

 

[honkyg 10+ year member]

good, reliable sound starts with your main source unit,.. it matters more than you might assume and boss is definitely not up to par in that department.

alpine, sony, clarion, kenwood, and pioneer is what i would advise sticking to if you buy new and dont want to get too snazzy,..

but if im reading correctly, it's just your head unit's internal amp that no longer works, correct?

if so, you may get lucky and the pre-amplifier outputs and processing still work, so you wouldnt immediately need a new unit,.. thus only calling for an external amplifier, which it looks like you're doing regardless.

 

[Water Bear]

Been giving this a little more thought. I can get away with a single aux in because I can just use an rca splitter. If I buy an amp then how much did the HU matter? For example I came across this Boss unit https://www.crutchfield.com/p_104560BRGB/Boss-560BRGB.html?tp=72310
That rigged up to the previously mention Alpine amp, is that good or bad? I really don't know much about HUs so I've no idea whether a set up like this would work.

Any thoughts?

Depends on what you're looking for. If you're using digital media files as input, you should check the specs to see if your head unit has a decent digital to analog converter. It's not required but it can't hurt, and not many head units (even digital media receivers) list it as a feature. Also you are looking for 4 volt pre amp outputs. Preferably 6 channels in case you decide to add a subwoofer at some point.

This JVC unit has what you're looking for. 6 channel pre-amp outs with 4 volts, built in 24 bit digital to analog converter, front USB and AUX inputs, and a 13 band EQ if you decide to play with your stereo set up. It even has a built in 22 watt amp, which may or may not be enough for you, depending on your needs.

Crutchfield is, IMO, the best place to buy head units because they will typically include your install gear (such as replacement face plates and wiring harnesses) either for free or super cheap.

As for amps, you can generally find better prices elsewhere, but Crutchfield has a truly bullet proof warranty / customer service set up. I bought an "open box" amp from them that was DOA and they exchanged it for a brand new one, no questions asked.

 

[oysterman]

good, reliable sound starts with your main source unit,.. it matters more than you might assume and boss is definitely not up to par in that department.
alpine, sony, clarion, kenwood, and pioneer is what i would advise sticking to if you buy new and dont want to get too snazzy,..

but if im reading correctly, it's just your head unit's internal amp that no longer works, correct?

if so, you may get lucky and the pre-amplifier outputs and processing still work, so you wouldnt immediately need a new unit,.. thus only calling for an external amplifier, which it looks like you're doing regardless.

The head unit's power button is faulty. When I turn the unit on it automatically puts the tuner on so I have to press the power button a couple of times to cycle through to AUX. Often the unit turns off when cycling through. Aside from that it's still working fine. I could use the remote to do this but that is also faulty. I may be able to pick one up on eBay.

 

[oysterman]

Depends on what you're looking for. If you're using digital media files as input, you should check the specs to see if your head unit has a decent digital to analog converter. It's not required but it can't hurt, and not many head units (even digital media receivers) list it as a feature. Also you are looking for 4 volt pre amp outputs. Preferably 6 channels in case you decide to add a subwoofer at some point.
This JVC unit has what you're looking for. 6 channel pre-amp outs with 4 volts, built in 24 bit digital to analog converter, front USB and AUX inputs, and a 13 band EQ if you decide to play with your stereo set up. It even has a built in 22 watt amp, which may or may not be enough for you, depending on your needs.

Crutchfield is, IMO, the best place to buy head units because they will typically include your install gear (such as replacement face plates and wiring harnesses) either for free or super cheap.

As for amps, you can generally find better prices elsewhere, but Crutchfield has a truly bullet proof warranty / customer service set up. I bought an "open box" amp from them that was DOA and they exchanged it for a brand new one, no questions asked.

That's the kind of thing I'm looking for, though the reviews do point to dodgy BT behaviour for that model, but yeah, good recommend. How does JVC build up against the 'big' manufacturers?