Crappy EQ - preout voltage issue for the replacement?

[bobdole369]

http://support.radioshack.com/suppor...oc39/39263.htm

Yup, I'm using an Optimus 7-band Passive EQ with sub output.

Here's the whole setup thus far (work in progress of course - and a bit of explanation) -

2004 PT Cruiser with the RBQ radio (Sirius antenna/radio with 6 disc CD changer - AM/FM - treble/bass/balance/fade and thats about it).

I'm an IT guy by trade and an apprentice self taught (mostly) EE wannabe. I picked up this PT Cruiser with 45k miles last fall. Its bone stock and I couldn't STAND the lack of volume and clarity on the radio. However the ease of use and listening options on the factory radio precluded me replacing it.

I know there are better decks out there that probably even sound a lot better, have more power, play MP3's, work with my Ipod, handle EQ and xover duties and all that. But there's something to be said for keeping the stock head unit. It fits quite well with the interior. Not to mention it might actually detract thieves.

Thus hatched my plans for a totally stealth setup in my car.

I'm on a pretty tight budget and I always get wife aggro for this stuff, so I found a Nakamichi PA-200 on ebay for about $40, and a Profile A6240xl for another $45, while I was at it I found a Profile AP600 for $30.

The thought was that I could use the Nakamichi up front in the dash where it would make a difference, and the lesser amps relegated to sub and midbass duty.

A couple weeks later I picked up a new set of Boston Acoustics S35's for the dash, and Pioneer TS-D161R 6.5" for the doors.

There is no preamp out on this headunit so I needed a way to come down from speaker level to line-level. I didn't want to use the crap I kept finding on ebay and I had this EQ from like 1994, and it accepted speaker level ins so I'd give it a shot.

I had to replace the lamps in front and repair a trace on the board that had become damaged, but then she lit up!

However......


Once everythings hooked up it does its job. The controls function as expected, except the fader is a bit noisy, and the Aux-In jack is just about unusable because its intermittent. Probably 14 years of being in storage has oxidized the crap out of it.

The noise is awful. It must have 50-70db of white noise on it. Its completely audible when the volume is down. I turn the deck up past 10 and the music drowns it out but its still there (between tracks and when the music goes silent).

Other than the EQ noise I'm quite pleased with the results. I have a crystal clear front stage with brilliant highs - the bass from the doors is punchy and responsive without being muddy or boomy, and the volume in the whole system goes WELL over what the factory speakers/deck ever dreamed of without clipping or harshness.


I'm planning to replace the EQ but here is my question (after all that).

I'm using old amps (Nakamichi PA-200 and Profile a6240xl currently, will add the profile ap600 shortly with a 10" sealed sub - and the other half of the a6240 will probably end up running a new set of 6x8's).

They are quite happy with the 400mv output that the EQ offers. When I get a new EQ, will it work out with the old school amps I'm using? Every single one has some different "max preamp voltage" and they are all like 5V, 9V, even 13V.

I tried going straight from the deck to the amps, and it completely overdrives them, with about a 3V signal (true RMS meter with a constant low tone).

When I put in a 9V output EQ will this also happen? How can I compensate (besides adding a resistor). A preamp would work here, but thats yet another unit.

Thanks in advance.

[phatredpt]

I can appreciate what your doing since I am currently running the factory HU on my 2002 PT myself
I am using a better quality LOC from David Navone, The NE-774V, which has adjustable output.
http://www.davidnavone.com/cart.asp?24&cat=7
I can then use standard signal level hardware beyond that point, and have the ability to adjust level if need be at the LOC to get to the "sweet spot" where I can set the amp gain for the best "tonality" and low noise floor.
(yep it does change with gain settings)
If you do stick with an EQ with speaker level in, just be sure there is a level, gain, or "master volume" adjustment and you should be able to match the input requirements on the amps fine!

[phatredpt]

BTW...

Welcome to DIYMA!

[bobdole369]

Determined the issue not to be the EQ, but the RBQ deck itself!

The Optimus EQ has low and high level inputs, but my units high level inputs are inoperative. So I connected the "front" speaker outs directly to the preamp - and I fade to R7 in order to bring the gain down to a reasonable clip free sound.

Apparently in this config the RBQ has quite a bit of noise (as essentially its putting out very little signal.)

THe straw that broke the camels back however was that the 6-CD changer broke (center spindle broke a plastic bit that raises and lowers the CD's), so I'm moving to a traditional HU in the future.

For now I just turn it up louder.