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Discussion Starter · #1 ·
I've been using an Alpine 3656 electronic crossover in my truck for the past 5 or so years.



It's about 20 years old, and so is a lot of my system as I love old school audio. It's worked great. Always quiet, never an issue until lately. I first started hearing lots of system noise ie. very high noise floor. Sounded like AM radio static. Then I started getting some alternator whine. I went through a system check and when I plugged my Alpine 3539 150x2 (midbass/midrange) straight into my deck RCA's, no noise. When I plugged my Alpine 3525 60x2 (tweeters) straight into my deck RCA's, no noise. When I removed the AudioControl ESP-3 from the signal chain, no difference. So I tracked it down to the 3656. Now there is a loud buzzing when the engine is running that goes up and down with RPM. It's an alternator buzz, if you will.

It would be easy enough to just get another crossover I suppose but I really like my 3656. Anything I could possibly check with my multimeter to determine the cause? Is it a ground that is going bad or cap(s) that are drying up or???
 

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Very likely a bad solder or connection issue with an RCA plug, possibly a bad or dirty switch. I'd measure ohms from ground terminal to all the RCA shields and see what they were, but the ground can be handled different ways. If you still have it mounted try moving all the switches a few times and try it again. Gently wiggle the RCA plugs, etc, maybe gently thump it while playing see if it changes. It sure sounds like a ground loop. It needs to handle the shield ground for the amps, but usually that will not be the ground that comes to the xover from the HU the xover makes a new ground so to speak. Anyway, they last a long time I'd look for connection issues first is most common.
 

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I've seen very few bad caps in old alpines, but always a possible issue with old equipment.
 

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I've seen very few bad caps in old alpines, but always a possible issue with old equipment.
I tend to agree with this. I have a 20 year old 3552 amp, and in the day they used Raycon, and Nichicon caps (great quality Japanese caps), and mine has no leakage, or signs of bulging.

The first thing I always check when I find a component in the loop, that introduces noise, is to check for loosely soldered RCA input jacks to main circuitboard.

Good luck!
 

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Discussion Starter · #6 ·
Thanks for the replies. I wouldn't doubt the RCA jacks need to be checked. I have a matching 3401 eq that needs to have the RCA jacks resoldered as they have been touchy ever since I bought it several years ago off Ebay. I have had to replace bad RCA jacks on 3 of my old Alpine amps. If that's all it is, it's not so bad I think. I do have an Altec Lansing ALC-20 that I could replace the 3656 with :) The 3656 is such a nice crossover though. So flexible. The one and only thing I would change about it is the fixed 12 db slopes.
 

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I have more than a few of them including 3518, 3527, 3542, 3555, some more 35xx, and some old mrv a 1002, T757, T407, maybe more. No bad caps I know of, except the 3555 that blew the voltage reg it burned the caps up. I have an old Nakamichi xover, so simple but so clean its amazing. Also have a couple ere g190 EQs for the PEQ on them.
 

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Discussion Starter · #8 ·
I had to re-do the RCA jacks on one of my 3 3525 amps and two of the 3 3539 amps I have. I put RCAs on pigtails on them. I also have two 3523 amps. One has a dead channel and the other is running an old DVC ThunderPro MTX 8" in an ABC box I made for my wife's van.
 
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