View Full Version : DC protection with Crown amps?

Doc Mark
07-15-2008, 08:26 PM
Greetings, Friends,

I have several Crown power amps, and have used them for years in PA applications. In all that time, I've never had a lick of trouble with them. However, I do know that once our band was using an old Crown DC300, with 802 Bose (PATOOIE!!) clones that our drummer cobbled up, and the amp passed DC to the speakers and fried the works!! We got the amp fixed, and used some other speakers whilst our little Bose copies had all their little speakers replaced.

Now, since I'm going to be using Crown power as part of my "new" stereo system, I'm wondering if there is something I can do to protect my speakers, should any of those amps decide to pass DC along the line? Any thoughts, comments, or suggestions would be greatly appreciated. Thanks, very much, in advance! Take care, and God Bless!

Every Good Wish,

Fred Sanford
07-16-2008, 04:17 AM
I have a DC sensing relay card in a little project box for use with my DC300A. I'll find you the Parts Express part # for the kit, and maybe snap some pics. The idea is that when DC is sensed on the speaker line, a relay coil energizes and disconnects the amp from the speaker loads.


Fred Sanford
07-16-2008, 04:25 AM
Parts Express part # 320-225, you'd need two for stereo.




Doc Mark
07-16-2008, 05:24 AM
Morning, Fred,

Outstanding info! Thanks, very much! I just told Sweet Bride about this idea, and she thinks it's a good one, too. When all is said and done, before I begin using this system too much, we'll avail ourselves of several of those little disconnects. I'll get some boxes for them, and call it good. I guess you just mount some input and output terminals on the sides of the box, eh? Sounds simple and quite easy, actually. Thanks, again! Great info, and much appreciated! Take care, and God Bless!

Every Good Wish,

Fred Sanford
07-16-2008, 06:37 AM
I didn't have a lot of time to type earlier, so here's the rest of my disclaimers: I use my Crown DC300A as a utility amp- sort of a loaner if any other amp in circulation goes out for repair. I can't say that I've done any critical listening with these boards in line, just tested them for function with meter and then with speaker load. Others here may have more to add, either good or bad. This project box was made with whatever was around at the time, in retrospect I'd have put binding posts as the speaker terminals in case of use in a PA situation.

Pics as promised...


07-16-2008, 11:07 AM
Are you going to be running any passive sections in the crossovers?? If you are any series capacitors will protect the driver behind it. So if you were biamping say a 4344 or 4333 as examples you would need it on the woofers and the 2122 only. The rest of the drivers all have a series cap in the crossovers. Always check the schematics to be sure.


09-26-2008, 02:09 AM
I was going to put mine inside each encloser but I like Fred's L&R project box better. Also like the fact that Fred's (older kits ?) have clear/see-through relay cases. They are opaque now with the kits.......

09-26-2008, 11:53 AM


Thanks for the info!!!!!


09-26-2008, 01:16 PM
Fred's relay board looks like it uses either the MY-2 or LY-2 type relay. Nice layout.:applaud:
Anyone know the relay contact rating of the PE board? You'll need at least a 5A rating.