Now that I've installed my player, I have a couple questions. Yes, I've been active on the board for > 2.5 years and I just last month installed my player!

In my '02 Maxima, I've got a Bose 6-disc in-dash changer wired to the aux-in of my empeg. The empeg runs out to the stock Bose amp. Having read the FAQ, I was expecting to have some volume issues because my setup is:
Bose HU ----> empeg ----> Bose AMP
and I've heard that they are different voltages.

But the effect is different than I was anticipating. The output from the empeg is too quiet. When I turn the volume up to 0db, it's a good strong medium, but not as loud as it should be (my perception of "should be" is based on listingen to CDs in the Bose HU -> Bose amp before I installed the empeg). And when I'm listening to a CD, if I turn the Bose HU's volume up more than about 2/3, it starts clipping and is rather distorted.

So my question is: Can I get more volume out of the empeg without replacing the amp? Maybe put another piece of hardware inline? I'm thinking that replacing the amp would then mean replacing the speakers (Bose being so proprietary and all). I've changed my config.ini so I can set the empeg to +10db, but over about +5 it gets notably distorted.

For never having installed a car stereo myself, I'm pleased not to have any problems with alternator whine, sub thumping or even Tony's pop when pulling the empeg out while driving. I've had many an occation when some experimental software I'm playing with exhibits bugs that require a power cycle and pulling the player out while driving and putting it back in has no pop at all (another reason I'd rather not replace the amp).

I'm guessing that the Bose HU has speaker level outputs. This is getting fairly common in factory installed systems, eg VW. The HU has an integrated amp, so it can feed the speakers directly. Then for the 'premium' option, they just throw in an additional speaker-level input amp and change the speaker setup. Sometimes the HU is reprogrammed (it is in VW), but I believe this is simply to take into account the speaker changes (ie extend the bass range).
This allows the car manufacturers to only have to produce one model of HU, and gain cost savings in doing so. It will help maintain Signal-to-Noise ratios at the amp too - the radio frequency noise picked up by the HU->amp wiring is going to fairly constant, but the signal on those wires is much greater.

Certainly this would explain both of your symptoms. You should be able to find line level converters fairly easily, although it's probably a good idea to try and garner some opinions on various models before outlaying any cash.

http://www.crutchfield.com/S-XFoTipitu8G/cgi-bin/ProdView.asp?i=101PL2 will do the HU-->empeg part.
http://www.crutchfield.com/cgi-bin/S-XFoTipitu8G/ProdView.asp?a=0&s=0&cc=01&g=751&id=detailed_info&i=127OEM2 looks like it would do either connection.

Have you looked or able to get at the amp and see if there are adjustable gain controls, I know that it's OEM but most amps have gain controls of some kind. If not I would go with genixia's suggestions.

issues because my setup is: Bose HU ----> empeg ----> Bose AMP

Exactly, that's the problem. The bose amp doesn't take line-level. That FAQ entry you linked referred to 1v line-level versus 4v line-level, not line-level versus speaker level (which is what the Bose amp is expecting to get).

After a bit of time away (and a couple vacations), I've finally had a chance to read the replies here. I wouldn't have guess speaker-level output from the Bose HU, but as you describe it, it makes a lot of sense and certainly helps explain what's happening. Thanks for the suggestions and info.

JrFaust, good idea, but no, I crawled into the trunk with a flash light and don't see any adjustments I can make to the amp... if only life were that simple :/

For the Bose HU -> empeg part, should I care about dropping the voltage? For now, I just don't turn the volume up all the way and it sounds fine... am I hurting the empeg, or is this an ok thing to do?

For the empeg -> Bose Amp, I read the description of the second link you provided. It sounds like it's going the other way "convert speaker level output to preamp output". Can I just turn that around to convert the empeg's pre-amp out to be a speaker level input to the amp? Or would I need a different device?

The speaker level to line level converter is essentially a fancy voltage divider (in the very simplest form you use a couple of resistors).
Going from line to speaker level would require an amplifier - not a big one, but an amplifier all the same.

I believe there are specific adapters available for line level out after market HUs to stock "premium" systems with high level inputs. Browse old stuff in teh Installation forum and I believe you find some posts about these (sorry, no good ideas for search terms...)

/Michael

Ok. Thanks for the clarification!

Browsing install pics, I saw this one which is for sale here.

The form doesn't work in Mozilla (on Linux or Windows), but it does in IE. Anyway, they ask what kind of HU it's for. Well, I'd like to answer that it's for a Nissan factory installed Bose HU. Because I've got two HUs (the Bose and the empeg), I had to make a custom 3-way wiring harness... the connection to the Bose amp is the factory connector and that's where this "OEM-1" thing would go (between a pair of mating Nissan-Bose connectors (sounds like a type of quark).

Now I'm wishing I'd started this thread in the Install Forum. My next question is: do any of the HUs listed have wiring harnesses like the Nissan-Bose? If not, should I just pick one and then buy a pair of wiring harnesses to solder together?

should I just pick one and then buy a pair of wiring harnesses to solder together?

I'm not sure exactly what you're talking about. Do you have a way of drawing a diagram of how you intend the system to go together?

If you're trying to wire two separate stereos to send their outputs into the same amplifier, just soldering their outputs together will not work. In fact, it might even damage them. You need either a switching system or a mixer to combine outputs.

Yeah, I wasn't sure how to explain that any better and can't picture an ASCII diagram. Attached is a rough diagram of the way my 2 HUs are wired up (I'm sure I missed a couple of the wires in there, but you get the idea).

All the connections in there are wiring harnesses so that if I want to sell the car some day, I can unplug them all. Re-connecting #1 and #2 puts the system back to the way it originally was.

So what I'd like to do is unplug #2 which exposes a forward and reverse pair of Nissan wiring harnesses and put the device in between there. If they don't sell those, then I'd go for something like:
#2 HU side ---> New Rev Nissan Harness==solder==New ISO Harness ---> "OEM-1" ---> #2 Amp side.

The phsycal wiring is a bit goofier than the diagram attached above because each of the Nissan harnesses is really two connectors. So I've got this big ball of wires with 5 connectors plus a buch of RCA jacks. Here's a photo from before I put it in the car.

Attached is a rough diagram of the way my 2 HUs are wired up (I'm sure I missed a couple of the wires in there, but you get the idea).

Ah, OK. You're doing a standard daisy-chain, using the empeg's aux input.

The first problem I see with this is that you're connecting the head unit's "amp out" directly to the empeg's "aux in". If my guess is correct, those wires coming out of the head unit are not line-level, and could overdrive or even damage the empeg's aux-in. They are somewhat amplified already, if I remember the way these Bose systems work.

Are you saying that you hooked it up that way already and it worked?

The first problem I see with this is that you're connecting the head unit's "amp out" directly to the empeg's "aux in".

Yes, if I turn the volume on the Bose HU up past about half way, it starts to distort. So I just keep the volume on the Bose HU at half all the time and use the empeg's volume knob.

I've been using it like that for about 4 months now and it works well. I don't often switch to radio or CD, but when I do, it works as expected.

Okay, so then the only missing piece is that PAC OEM-1 to boost the level of the empeg's outputs up to the level that the Bose amp seems to want.

Ah, good. That's the kind of confirmation I was hoping for.

Any recommendation on what I should fill in on the web page for HU type?
"Alpine 16 pin"; "Audiovox 14 pin";"Blaupunkt 16 pin"; "Clarion 16 Pin"; "Eclipse 16 Pin"; "JVC 16 pin"; "Kenwood 16 Pin"; "Panasonic 16 pin"; "Pioneer 12 pin"; "Pioneer 14 pin"; "Sanyo 12 pin"; "Sony 16 pin"; "Universal speaker"; "Universal RCA";
I don't know which one of those choices would ship with a standard wiring harness that I could buy a mate to (or cut off and spice to a new Nissan harness).

Universal RCA. The empeg has RCA outputs.

That's the empeg side. For the bose side, you have to make another selection that matches your exact vehicle.

So the OEM-1 arrived in the mail today.

I've been pretty excited to install it so I pulled my dash apart, took out my custom wiring (dual head units in series) and wired up this guy. I get done putting all the connections together, take it out to the car, and it's exactly the same as it was without the thing installed!

So now I'm pretty peeved that I went through all that work for naught... and now I've gotta put it all back so I can return the stupid thing.

Yes I played with the adjustment knobs on the box... I can make it quieter, but the empeg itself supports -infinity db so that end of the spectrum is covered. Turning the knobs all the way up and setting the empeg for 0db, it's exactly the same as it was with the empeg plugged directly into the Bose amp.

So did I buy an $80 volume dampener?

Wow.

You know... I never even tried to find the pinouts to the Dodge harness and just see if hooking it up the RCAs directly sounded any different...

One thing I do know is that, in the install we did, with the OEM-1, it's adequately loud. It's not as loud as the factory stereo, but it's loud enough to crank. So there's something going on that's different...

Well, for now, I've re-wired again and have the empeg's output plugged into one of those tape adapter thingies. It's kinda ugly to have a wire sticking out of my tape deck and it's notably lesser quality (as should be expected).

At half volume, I don't notice any distortion (with the empeg direct to the bose amp half volume was all I had anyway). So now I have the option of upping the volume more at the cost of a little distortion.

The plus is that I can use my steering wheel remote for volume again (factor remote for Bose HU, just select tape to hear empeg). And for the rare times I play CDs, they play at full volume without distortion (as they did before I added the empeg).

If I were a true audiophile, I'd go buy a real amp and get rid of the Bose one.... maybe next year. The patchwork job I've got now should tide me over.

I don't often read the Maxima forums, but was looking for something else when I ran across this Aux Input Adapter. I'd go with that option, except I have the one known model that doesn't work as listed on the bottom of this page.

Also of note is this post in which he seems to have the same problem I had:

I wanted to run from the HU's RCA preamps to the Bose amp, but the volume wasn't there. I had the HU all the way maxed out at 35 and the sound wasn't all that loud. So I tried hooking up the HU's RCA preamps to the PAC kit, but I had the same problem.

I guess I should've done more research before buying stuff...