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Thread: Crown DC-300A & D60 service

  1. #1
    Member mark214's Avatar
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    Question Crown DC-300A & D60 service

    I have pair of DC-300A and a D60 amps that have been sitting unused for 10+ years, I am looking to have checked/serviced.
    Any recommended techs out there?
    Thanks
    Last edited by mark214; 10-28-2021 at 12:39 PM. Reason: correction

  2. #2
    Heather [Senorita member] hjames's Avatar
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    Quote Originally Posted by mark214 View Post
    I have pair of DC-300A and a D60 amps that have been sitting unused for 10+ years, I am looking to have checked/serviced.
    Any recommended techs out there?
    Thanks
    I see your location is "Low Earth obit" but perhaps if we knew better where you are actually located we could offer more helpful info.
    I've had good luck with Music Technology in Springfield, VA - but no idea if that's local to you or not.

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  3. #3
    Dang. Amateur speakerdave's Avatar
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    There's an outfit in Crown's home city that specializes in legacy Crown products.

    AE Techron, Elkhart, Indiana.
    "Audio is filled with dangerous amateurs." --- Tim de Paravicini

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    Quote Originally Posted by speakerdave View Post
    There's an outfit in Crown's home city that specializes in legacy Crown products.

    AE Techron, Elkhart, Indiana.
    AE Techron was the industrial amp division of Crown, some of the original Crown audio techs also work there
    now.

  5. #5
    Member mark214's Avatar
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    I hooked up the first DC300a to a pair of speakers and looped it off of an iPod for 12 hours a day it ran well, without a fan the heat sinks were warm but not hot the pots were noisy as heck but a blast of DeoxIT ended that issue.
    The other DC300a will be run through the same thing.
    The caps look original, I am going to look at having them replaced, neither amp looks like they have been serviced.

  6. #6
    Senior Member BMWCCA's Avatar
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    Quote Originally Posted by mark214 View Post
    The caps look original, I am going to look at having them replaced, neither amp looks like they have been serviced.
    Are these the original series A, not the DC300A-II? Either way, one tough amp that may still be performing perfectly. Though not saying you shouldn't have it checked out. The years fly by but my original D150 went back to Crown sometime around 1977 when it was still in warranty and has been soldiering on just fine ever since.
    ". . . as you have no doubt noticed, no one told the 4345 that it can't work correctly so it does anyway."—Greg Timbers

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    Do both channels of the amps sound the same?

    Keep in mind the DC (direct coupled) 300 has no coupling caps in the signal path, not saying there could
    be a few other small electrolytics that maybe could be needing changed.

    Remember that direct coupled means that amp will pass and amplify DC voltage if there is any on the input!

    The D60 amps do have coupling caps in the signal path.

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    Member mark214's Avatar
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    Quote Originally Posted by Mike Caldwell View Post
    Do both channels of the amps sound the same?

    Keep in mind the DC (direct coupled) 300 has no coupling caps in the signal path, not saying there could
    be a few other small electrolytics that maybe could be needing changed.

    Remember that direct coupled means that amp will pass and amplify DC voltage if there is any on the input!

    The D60 amps do have coupling caps in the signal path.
    Are there any way or ways to protect speakers from the potential of passing DC from a DC 300a? Or is that not a major concern with the direct coupled amps?
    Yes both channels sound about the same.
    Protecting at best hard to replace JBL speaker components is a primary consideration.

    Thanks to You and all who have posted to this thread, if has been very helpful.
    Last edited by mark214; 10-31-2021 at 06:00 PM. Reason: added comment

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    Member mark214's Avatar
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    Quote Originally Posted by BMWCCA View Post
    Are these the original series A, not the DC300A-II? Either way, one tough amp that may still be performing perfectly. Though not saying you shouldn't have it checked out. The years fly by but my original D150 went back to Crown sometime around 1977 when it was still in warranty and has been soldiering on just fine ever since.
    Mine are the pre series II amps.

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    For use when driving compression drivers its standard procedure to install DC blocking capacitors in the speaker enclosure for just that purpose usually sized to roll off about two octaves below the desired crossover frequency. Not terribly practical for speakers with crossovers below a few hundred Hz. Its a big part of the reason that DC300s went out of favor with professional users back in the 80s. It's not out of the question to build an outboard relay protection circuit to emulate that used in most large power amps but I don't know of any off the shelf versions these days.


    Quote Originally Posted by mark214 View Post
    Are there any way or ways to protect speakers from the potential of passing DC from a DC 300a? Or is that not a major concern with the direct coupled amps?
    Yes both channels sound about the same.
    Protecting at best hard to replace JBL speaker components is a primary consideration.

    Thanks to You and all who have posted to this thread, if has been very helpful.

  11. #11
    Senior Member BMWCCA's Avatar
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    Quote Originally Posted by Riley Casey View Post
    For use when driving compression drivers its standard procedure to install DC blocking capacitors in the speaker enclosure for just that purpose usually sized to roll off about two octaves below the desired crossover frequency. Not terribly practical for speakers with crossovers below a few hundred Hz. Its a big part of the reason that DC300s went out of favor with professional users back in the 80s. It's not out of the question to build an outboard relay protection circuit to emulate that used in most large power amps but I don't know of any off the shelf versions these days.
    Not to diminish the value of what is said here, above, but I wrote this over seven-years ago and can still say the same today:

    I've used PS200, PS400, D150, D150A-ii, and DC300A-II amps (some) for over 45 years. Never a problem with speaker damage. Not saying it couldn't happen but it's not really an issue that should cause you to run away from them. Every Crown manual shows how to fashion a simple in-line fuse to protect your speakers. I ran my first D150 that way with my first JBL 030s. At some point I quit doing it and those 030s are now nearing 60-years old and the original Crown passing 45. Both still work great!
    And others concurred:
    Quote Originally Posted by KentTeffeteller, post: 9995213, member: 13294
    Yes, Crown owners who read their manuals can find out speaker protection. And BMWCCA speaks truth here. Never had a Crown amplifier in studio service fail like that and this is many a D 75, D 150, DC 300a, DC 300a II, and Studio Reference.
    ". . . as you have no doubt noticed, no one told the 4345 that it can't work correctly so it does anyway."—Greg Timbers

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    Senior Member Odd's Avatar
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    It is becoming more and more difficult to replace old JBL drivers.
    I have therefore mounted speaker protection on all old power amplifiers.
    And on class A amplifiers.
    I have used a kit from Velleman.
    There are many who deliver similarly.

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    I suspect the salient element of the discussion now is the consequences of a failure when driving speakers that simply cant be repaired under any circumstances. I was a service tech for a Crown dealer back in the late 70s to early 80s and by definition saw the results of the few amps that did fail more than the many more that worked without trouble. But trouble when it comes on a DC300 can mean 90 - 100 VDC ( don’t remember the actual rail voltages ) delivered to the speaker until the rail fuse opens. An expensive nuisance for the owner of a JBL 4343 or Altec 604 speaker owner in 1985, a catastrophe for that same owner today. Output relay clicking closed on my Tandberg 2080 these days give me a warm fuzzy feeling.

    Quote Originally Posted by BMWCCA View Post
    Not to diminish the value of what is said here, above, but I wrote this over seven-years ago and can still say the same today:



    And others concurred:

  14. #14
    Member mark214's Avatar
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    Thanks again for the responses.

    I found a service center that has been servicing Crown JBL and many other lines of pro gear for many years about 100 miles from me and will be working with them directly.

    The post on Velleman protection gear or for that matter any other manufactures of devices that will protect my valued JBL speakers looks like something I will be looking into as well.

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    I still use blocking caps on HF drivers and the days of powering them with DC300's are long over.

    If I'm not mistaken the Crown manual had a schematic for a relay DC protection circuit to put between the amp and speaker.


    Edit......I just looked up a DC300 manual and the relay circuit was for general overload protection where the a relay would switch a light bulb in series between the amp and speaker. It would most likely help save your speakers for a DC accident.

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