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Topic: Epected life of a QSC DCA1644

Jarod Reddig
Jedi Master Film Handler

Posts: 513
From: Hays, Ks
Registered: Jun 2011

posted 11-24-2014 03:54 PM

Damn great deal on those man! Ya for that price it would have been hard to pass those up.

Ya I have a deep deep passion for Cinema and all the gear related to it. I really love this site as well.

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Tony Bandiera Jr
Film God

Posts: 3067
From: Moreland Idaho
Registered: Apr 2004

posted 11-28-2014 09:19 PM

quote: Jarod Reddig
HT wise Crown amps are great amps. Don't be fooled.

LOL sorry Jarod, have to disagree 100% on this one. For the reasons I gave in my first post, Crowns are amongst the WORST amps for home theatre use. Two reasons:

quote:
The XLS models do have some fan noise but I bet anyone designing a no frills HT has there own equipment room in an adjacent room or closet. There are also fan mods for them if they must be placed in the room,

I was not referring to the fan noise in my previous post....the noise floor refers to the standby "hiss" in those amps. Crowns are very noisy in that respect...and in one of the other threads on Crowns, a poster there mentioned having to replace and "mix and match" several Crowns to get all of them quiet enough for the application. Unacceptable in a close-quarter screening room. (And for the price of those amps.)

Second:

quote: Jarod Reddig
Ive used Crown DC300A series II amps for years in my HT with no problems at all and they were over 20 years old when I bought them used.

The DCxxx series amps are NOTORIOUS for failing without warning and impressing the FULL DC power supply bus on the speaker terminals at FULL current. You were extremely lucky. BTW, those amps were originally designed for use with "Shaker tables"..they drove linear motors and transducers to provide high-amplitude motion at frequencies from DC to over 40khz. (The same wide range capability, while excellent for audio fidelity, can be and often was fatal to speakers and HF drivers due to lack of protection from DC offset and HF oscillation.)

Crowns are an amplifier that survives on hype and imagined reputation of quality rather than reality. [Wink]

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Sam D. Chavez
Film God

Posts: 2153
From: Martinez, CA USA
Registered: Aug 2003

posted 11-28-2014 11:45 PM

quote: Tony Bandiera Jr
The DCxxx series amps are NOTORIOUS for failing without warning and impressing the FULL DC power supply bus on the speaker terminals

I'd say notorious is too strong a word. This amp had its day in late '70s and early '80's and was the best sounding commercial amps around at that time, partly because the others were so bad. There were high numbers of DC300's that worked flawlessly for 20 years without incident.

BGW's were very good back then but the company was badly run to say the least.

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Jarod Reddig
Jedi Master Film Handler

Posts: 513
From: Hays, Ks
Registered: Jun 2011

posted 11-29-2014 05:03 AM

Much agreed Sam they have one hell of a track record, even considering its issues.

Tony I guess we can agree to disagree. No harm in that.

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Mark Gulbrandsen
Resident Trollmaster

Posts: 16657
From: Music City
Registered: Jun 99

posted 11-29-2014 11:13 AM

Crown amps suck. Crown has been Harmonized much the same way JBL has been!

The part that fails mostly in the DCA's is the input level pots. They are absolute crap in what otherwise is an excellent amp series. Not sure why QSC chose to use a part that becomes intermittent and some times just completely fails. Sometimes a little Pro Gold fixes them up but they are actually plastic attenuators of the very cheapest variety. Ugh!

Yes... I have driven hundreds of miles because of these DAM pots!

There! That is my one and only RANT about QSC.

Mark

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Jarod Reddig
Jedi Master Film Handler

Posts: 513
From: Hays, Ks
Registered: Jun 2011

posted 11-29-2014 02:19 PM

Define suck lol.

Ya I had cleaned the pots when I first got them. They were a bit scratchy.

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Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12814
From: Annapolis, MD
Registered: Dec 1999

posted 11-29-2014 05:18 PM

QSC claims it is a particular run of pots that have the issue. I'll admit, I don't have the noisy pot issue on all amps...just a particular generation (I want to say 2007-2009 are the most suspect).

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Mark Gulbrandsen
Resident Trollmaster

Posts: 16657
From: Music City
Registered: Jun 99

posted 11-30-2014 09:43 PM

Also on other models of amps but not on USA or the later DCA. The fan blows the crud right into the pots!!

Mark

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Brad Miller
Administrator

Posts: 17775
From: Plano, TX (36.2 miles NW of Rockwall)
Registered: May 99

posted 11-30-2014 10:36 PM

Very odd. I've not had the issue AT ALL with QSC DCA amps, and I'm quite sure I installed more than enough in the 2007-2009 time frame.

Now the mx series...UGH!!! I'll just leave it at that.

I'm not saying it isn't/wasn't a problem, but I've not personally experienced it. Those amps have been nothing short of awesome for me in every regard.

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Mark Gulbrandsen
Resident Trollmaster

Posts: 16657
From: Music City
Registered: Jun 99

posted 12-01-2014 09:18 AM

If your booths are really dust free you may never experience it. The pots are not sealed so the fan blows crud right into the pot. I've had it happen at a half dozen locations.... and yes! It is dusty around here. A huge waste of time and expense the customer shouldn't have pulling amps out of a rack opening them up to clean a 20 cent pot.

Mark

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Scott Norwood
Film God

Posts: 8146
From: Boston, MA. USA (1774.21 miles northeast of Dallas)
Registered: Jun 99

posted 12-01-2014 09:49 AM

WRT the MX series...I have had to replace a bunch of pots on MX-1500a units. That seems to be about the only part that goes bad on them, but it is annoying. Is there a better quality replacement than the one that QSC sells?

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Ron Lacheur
Jedi Master Film Handler

Posts: 650
From: British Columbia, Canada
Registered: Feb 2002

posted 12-01-2014 11:07 AM

A 10k Bourns or Clarostat pot should do the trick for a sealed replacement. Not sure what the taper is though.

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Marco Giustini
Film God

Posts: 2713
From: Reading, UK
Registered: Nov 2007

posted 12-01-2014 02:44 PM

I haven't seen completely faulty trimpots, but seen 'dead' DCA amps where the problem was fixed by cleaning the pots by rotating them back and forth a few times. Seen it several times unfortunately. But DCA's are still the best out there - IMHO.

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Jim Cassedy
Phenomenal Film Handler

Posts: 1661
From: San Francisco, CA
Registered: Dec 2006

posted 12-01-2014 04:05 PM

quote: Mark Gulbrandsen
The pots are not sealed so the fan blows crud right into the pot. I've had it happen at a half dozen locations

No kiddng, Mark! [Frown]

I've had the same problem here with a wholebuncha Ashly amps.

Ashly used the cheapest unsealed pots & mode switches on the input modules of
some of their amplifiers and at least once a year I have to pull the modules
out & douse them with Cramolyn or some similar contact cleaner/lube.

I'll bet they spent less than 50cents each on those pots in the quantities they
were buying them. A couple of even cheap sealed pots & switches wouldn't
have added that much to the overall cost of their amps.

The problem here is not only dust, but the "salt air" since the theatres I've
got the most problems with are located near either the ocean or SF Bay.

I just had to go down & pull all the modules out at one theater due to the
"noisy pot problem" just last week.

Fortunately, the theater owner (and I ) am getting tired of doing this,
so we've begun to swap out the old Ashlys for some new QSC's. thank gawd!

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Steven Smith
Film Handler

Posts: 35
From: Boyce, La/ USA
Registered: Jul 2014

posted 01-07-2015 01:04 PM

Figured I'd give an update. Well I received and really like the Crown. Plenty of power and sounds great...as long as it's on speakers below 96ish db. I tried it on a 97db and my QSC 2150 @101db sensitivity and there is just too high of a noise floor IMO.

So I ended up buying the same QSC 1644 from the guy who bought it from the guy I almost bought it from.. for a little less $$ too. I got lucky!

You guys were right...the QSC is in another league which is evident with the two just sitting side by side and comparing build quality, of course this is the Crown XLS series, so it's one of the cheaper Crowns. And it's so much quieter. with Crown the noise floor was evident from 8 feet plus with the QSC 2150s, and with the DCA amp it disappears around 2 feet away. It should be perfect for my setup.

I just have to swap the fans as it's kinda noisy but I already have one being shipped and it's no big deal to swap it out, I actually had to unplug the fan so i could quiet the room to test the noise floor, Of course I won't use it without a fan.

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