Crown DC300A

[Passinwind]

Thanks Passwind.

Got hold of the service manual for the DC300A --- the version I have. And, my bandmate has already placed an order for the resistor.

Cheers!

Cool. Be careful, those huge power supply caps can pack quite a bite.

 

[BassmanPaul]

Crown actually just called bridge mode mono back then, just looked at a couple of manuals to confirm.

Interesting Charlie. That's not how I remember it BUT it was forty odd years ago!!

 

[busmandan]

But there were some hugely unreliable amps on the market in the 70s as well, and Crown looked good compared to those.

Phase Linear, anyone? I've actually seen these burst into flames (which is also why many referred to them as Flame Linear).

 

[Passinwind]

Interesting Charlie. That's not how I remember it BUT it was forty odd years ago!!

Paul, IIRC some of the commercial install series amps indeed had parallel mono mode and one or two even had summing parallel mono. I definitely had to go to the manual to double check what I posted above, even though I serviced many installs with these amps and owned a few myself too.

 

[Gizmot]

Even if your amp can go to dc, you don't want to feed that to your speakers no matter what kind they are or how much power they can handle.

Back in the 70s, the Crown was more thermally stable than the Phase Linear and Harmon-Kardon amps people used. They need a fan or a lot of air circulation if you're going to push it hard

 

[drummer5359]

I used my DC 300 A for DJ work for a long time. It's been semi-retired for the past few years. I use it down in my music room with a Numark dual deck CD player for music play back through some Peavey SP 2G speakers. I just bought a set of powered QSC speakers, so it is close to full retirement soon. I'll likely give it to a nephew (drummer) who is much younger and stronger than I.

Back in the day a bassist that I worked with cooked his Crate bass amp. He used a Peavey preamp and ran the Crown as a power amp into a Fender bass cab for six months or so until he bought a new Fender bass head. He really liked the Crown as long as someone was available to help carry it.

When I used it to DJ it was in a rack case with wheels.

 

[pbassnut]

I had a DC 300A Series II for many years that I ran bridged mono driven by various tube and solid state preamps which powered a Mesa Boogie Road Ready 1x15. An audio classic workhorse amp to be sure. I, as most people do/did, had a rack mountable cooling fan in back of it. I sold the Crown amp and Mesa cab years ago as I'm just too old and decrepit to haul those cinderblocks around anymore. They sure served me well, though.

 

[83_Silberpfeil]

Success! Was able to open up the amp. Per the user/maint manual rewired it for mono / single channel @ 300 W. Also, removed the 3rd prong on the power cord. Works like a champ w very little heat. It is powering a twin 15" Gauss 5640 (16 ohm) cab. At times it powers a single 15" Mesaboogie cab.

 

[agedhorse]

Success! Was able to open up the amp. Per the user/maint manual rewired it for mono / single channel @ 300 W. Also, removed the 3rd prong on the power cord. Works like a champ w very little heat. It is powering a twin 15" Gauss 5640 (16 ohm) cab. At times it powers a single 15" Mesaboogie cab.

Any particularly good reason why you would want to do this?

Note to others reading this post, never, ever remove the ground pin from the power supply of any piece of equipment designed with a grounded chassis. This is essential to the safety scheme in the event of a power supply fault to ground which would otherwise allow the chassis to raise up to line voltage (either 115 or 230V depending on the market).

If there is an audio ground loop that's causing hum, use the proper and safe tool for the job which is a 1:1 audio isolation transformer that isolates audio grounds while allowing the safety grounds to remain intact. Ebtech is one company who makes these, but Radial, ProCo, and others have them as well.

 

[agedhorse]

Also, note that in bridge mono mode, the DC-300 is only rated to drive a single 8 ohm load in bridge mono mode. I too worked on Crown products back in "the day". Folks driving 4 ohms bridged was a common cause of overheating, but even at 8 ohms bridged or 4 ohms stereo they did get very hot. I recall there being an accessory fan kit available but I may be confusing this with the D150.

 

[svtb15]

Way back i used a Crown 300A with my old API preamp or alembic f2B into 2 separate cabs .. a custom Bag end 215 and an SVT 810.. I had a fan on each side of the crown . i never had an over heat..
I later moved onto a crown PSA2 from showco after the 300A was stolen... we did have a road crew though... heavy Mother it was... these days i play bigger rooms with a small amp and 210 or just a 115 Uber cab... and PA support.. Wow have times changed

 

[Bill Whitehurst]

For years I used one for PA mains and another for monitors.
At 8 ohms/channel, they'll go on forever.
My back, not so much.

In the 70's I knew a guy that ran an Alembic pre into a bridged DC300A, into a Dual Showman cabinet with D140Fs.
Sounded great.
Blew JBLs on a regular basis.
Why it didn't cook the outputs is a mystery.

 

[agedhorse]

In the 70's I knew a guy that ran an Alembic pre into a bridged DC300A, into a Dual Showman cabinet with D140Fs.
Sounded great.
Blew JBLs on a regular basis.
Why it didn't cook the outputs is a mystery.

Perhaps because they were D-140J's (16 ohm) which were very popular back then...

 

[83_Silberpfeil]

SVTB15 --- Thanks for chiming in. I just acquired an Alembic F2B and tried connecting to the Crown. I now have two DC300a's --- one with the Dual/Mono switch and one without the switch (but rewired to operate mono only). Getting lots of buzz and not much bass guitar signal. Any ideas? Here's how I'm connecting...

Bass >>>Alembic Front Input Channel A port 1 >>>Alembic Back output Channel A (also tried MONO) >>> Crown input 1>>>Crown output RED+ on both channels >>> cab

Way back i used a Crown 300A with my old API preamp or alembic f2B into 2 separate cabs .. a custom Bag end 215 and an SVT 810.. I had a fan on each side of the crown . i never had an over heat..
I later moved onto a crown PSA2 from showco after the 300A was stolen... we did have a road crew though... heavy Mother it was... these days i play bigger rooms with a small amp and 210 or just a 115 Uber cab... and PA support.. Wow have times changed

 

[Stank56]

I think that I ran mine many years ago on channel one only when bridged. Meaning channel one output as well, just wanted to add that as to not confuse.

 

[agedhorse]

Bridged output load connects between 1+ and 2+ outputs.

 

[svtb15]

Sounds like you are correct.. .Bridged Output should be the Two RED terminals..
Mono or Stereo should not give you extra added Buzz sounds.

are you getting a hum sound or a OR buzz?

IIRC, The out of the ALEMBIC preamp Channel A or B(whatever you are running on the front of the pre) should go into Channel A on the 300A.
If the amp is in MONO setting Vol A or Channel 1 on the crown should be your MASTER VOL. Channel B or 2 should have no effect when in MONO.
Speaker terminals on the Crown WHEN IN MONO should be the two RED terminals and NO BLACK. Attack Positive to Channel 1RED and Negative wire to channel 2RED.
I would run teh Crown Wide open and adjust VOL with the Input on the Alembic preamp..
Make sure that you have a good quality Shielded wire on the output of the preamp going to the input on the rear of the crown. Any 1/4" to 1/4" mono phone jack should be fine..

Does the Crown work without the ALembic pre.. Maybe try another input source... Check your Jumper wire... Make sure that the input to the crown is not full of corrosion.... Thats an old amp and there may be corrosion build up..

SVTB15 --- Thanks for chiming in. I just acquired an Alembic F2B and tried connecting to the Crown. I now have two DC300a's --- one with the Dual/Mono switch and one without the switch (but rewired to operate mono only). Getting lots of buzz and not much bass guitar signal. Any ideas? Here's how I'm connecting...

Bass >>>Alembic Front Input Channel A port 1 >>>Alembic Back output Channel A (also tried MONO) >>> Crown input 1>>>Crown output RED+ on both channels >>> cab

 

[83_Silberpfeil]

Crown DC300a --- have two of them, both working like champs directly w bass and Mesa cabs.

Alembic Club forum moderator helped me figure it out.

Inside the Alembic are 4 blue capacitors. They sit on top of a foam pad. The foam pad got old and brittle after 30+ years. I take it that during shipment it got thrown around by USPS and the foam fell apart. That caused 3 of 4 caps to shear off the circuit board --- only connected by one solder point. I sent it back to Alembic for cap replacement ($65) and general inspection/tune-up, etc. Can't wait to get it back.

Thanks again all for chiming in. Great bunch here!

Sounds like you are correct.. .Bridged Output should be the Two RED terminals..
Mono or Stereo should not give you extra added Buzz sounds.

are you getting a hum sound or a OR buzz?

IIRC, The out of the ALEMBIC preamp Channel A or B(whatever you are running on the front of the pre) should go into Channel A on the 300A.
If the amp is in MONO setting Vol A or Channel 1 on the crown should be your MASTER VOL. Channel B or 2 should have no effect when in MONO.
Speaker terminals on the Crown WHEN IN MONO should be the two RED terminals and NO BLACK. Attack Positive to Channel 1RED and Negative wire to channel 2RED.
I would run teh Crown Wide open and adjust VOL with the Input on the Alembic preamp..
Make sure that you have a good quality Shielded wire on the output of the preamp going to the input on the rear of the crown. Any 1/4" to 1/4" mono phone jack should be fine..

Does the Crown work without the ALembic pre.. Maybe try another input source... Check your Jumper wire... Make sure that the input to the crown is not full of corrosion.... Thats an old amp and there may be corrosion build up..

 

[Bill Whitehurst]

Almost a year since the last post here.
Time to wake up this thread for a classic power amp.

Although I have lost interest in moving any of the monsters,
I may have found a good use for the ones I have.
My guitard/BL is trying to buy a bar.

Since I already have 3 300As and a D150
(that all need work), I am thinking about trying
to rebuild and update these things and use them in a big rack
for a house PA.

After some internet snooping I see that the MJ21194
should be a good choice for outputs.
My thoughts are that with the IOC option, new outputs, fresh e caps
and some sort of DC blocking for the speakers they may be happy for a lot of years.
I'd be happy to see them back on the job, without me having to hump them around.

Is there any good reason not to use isolation transformers for the output to block DC.
I ask because I have seen drivers and predrivers short and fry speakers.

I think I want to run a pair bridged for subs, one for mains and use the D150 for monitors.

 

[agedhorse]

Yes, several good reasons why transformers are not good (though sometimes necessary):

It's difficult to find such output transformers that are 1:1 ratio

It's difficult to find such transformers with wide bandwidth (esp. LF response) and high power levels.

Such suitable transformers are going to be fairly large, heavy, and expensive.

There are better ways to protect from DC faults.