Running a Crown D45 power amp in bridged mode

[robertbartsch]

I bought this used Crown D45 for a center channel play and would like to bridge the amp.

I attached the speaker wires into the two (+) outputs, one for the left and one for the right channel but no sound. When I attached the speaker wires to a single (+) and minus (-) outputs, the amp plays well from the right or left channels.

Is there a "bridged" switch somewhere on the amp?

Thx...

[speakerdave]

Google tosses the manual up on shore. That amp must be modified by a technician for bridged mono mode. It warns specifically against using the positive terminals. Hope you have not damaged your amp.

Correction: I misread the diagram. You do use the positive terminals. Why they show you how to wire it and than warn you not to do it is a puzzle.

[robertbartsch]

.....there is a JBL tag on the back that says, "use channel 1 for bridged mode."

[speakerdave]

There are instructions in the online manual for a so-called bridged mono mode without really bridging the channels. It is intended for running the same signal to SEPARATE speakers. The earlier D60 had a switch for bridged mode. Removed because? Cost cutting maybe? Your sticker and the language in the manual look like obfustication to me, meant to make a person think something is there that is not really there in the usual sense. The manual clearly states internal modification required to add the voltage of the two channels. Maybe a D60 or if you have more rack space a 6230 JBL UREI. The 62xx series has a three-position switch: Stereo, dual mono and bridged mono. Meanwhile, your D45 is said to be a very nice headphone amp.

[BMWCCA]

Maybe a D60 or if you have more rack space a 6230 JBL UREI.

The D75A is the same 1-RU space as the D45. But then it's apparent we're trying to use what we've got here!

I believe others here—maybe even GT?—recommended the D45 as an excellent amp for the 2405 in a 4-way JBL. I bought three of them just to try it out but haven't yet had the time to play.

[audiomagnate]

If you do get it working be aware that a bridged amp "sees" an 8 ohm load as 4 ohms, a 4 ohm load as 2 ohms etc.

[speakerdave]

According to the manual online, which covers both the D45 and D75A, neither has a bridging switch. In case the owner has a tech modify the amp to bridge the outputs instructions on how to use it are given, to prevent the owner blowing the amp and giving the company a warranty problem. The instruction in the manual for "bridged mono" really bridges just the inputs and is, like the dual mono switch on the UREI amps, comparable to the mono position on a preamp mode selector, making it possible to send the same content to both outputs, connected to separate speakers, when only one input signal is available. Only when the voltages of the two channels are added, with a bridging switch or internal modification, is it possible to safely connect both outputs to the same speaker terminals.

[Allanvh5150]

Most amplifiers are not bridgeable unless they are built for it, regardless if you feed one side an inverted input. Bridge mode increase the voltage to the load by a factor of two and consequently tries to increase the power output of the amplifier by a factor of 4 into the same impedance load. The first thing that will not be up to snuff will be the power supply. The second thing, the current needed from the output devices will double which could easily put them well outside their safe operating range.
A good rule of thumb when bridging an amplifier is to double the output load impedance. Then all will be safe.

Allan.

[hjames]

I'm missing something here?
Since there are so many good Crown Amps -
if you need more power, go to the next larger amp.
D75 or D150 ought to do ...


The only amp bridging I did was to feed my 4641 sub ...
since high frequency fidelity wasn't important,
it didn't matter if the HF noise floor moved up in the process.

But with a center channel being so important for dialog -
the converse is true ... noise would be SO evident!

[Mannermusic]

Most amplifiers are not bridgeable unless they are built for it, regardless if you feed one side an inverted input. Bridge mode increase the voltage to the load by a factor of two and consequently tries to increase the power output of the amplifier by a factor of 4 into the same impedance load. The first thing that will not be up to snuff will be the power supply. The second thing, the current needed from the output devices will double which could easily put them well outside their safe operating range.
A good rule of thumb when bridging an amplifier is to double the output load impedance. Then all will be safe.

Allan.

Yep. Actually tried the bridging exercise on the D60. Shut itself down when pushed significantly. Not stable. These used to run UHF just fine in a tri-amp but are not intended to do what a D150, etc. can do. Also don't sound as good. Not to mention, this stuff is old! I miss these old amps, SAE as well, but even when "refurbished" they don't sound the same. There were proprietary parts involved. So it goes.

[BMWCCA]

Yep. Actually tried the bridging exercise on the D60. Shut itself down when pushed significantly. Not stable. These used to run UHF just fine in a tri-amp but are not intended to do what a D150, etc. can do. Also don't sound as good. Not to mention, this stuff is old! I miss these old amps, SAE as well, but even when "refurbished" they don't sound the same. There were proprietary parts involved. So it goes.
The D75A is, or was, still in production quite recently. My PS200/PS400 amps still sound fantastic. I even bought one that had recently been back to Crown for a performance check and was supplied with a complete measurement report needing only some minor adjustment. These are tough amps. I'd call them "missionary" tough but then I really haven't recently met any missionaries I thought deserved the comparison! ;)

[1audiohack]

...I'd call them "missionary" tough...

It sounds like you may know the history of "Crown" pre Harman.

Side note, saw Jerry Stanley at INFOCOMM. :)

Barry.

[Baron030]

Your D-45 should be like the D-75A, and converting the amp from stereo mode to bridged mono is not a big deal. In the case of the D-75A, there is a small PC board pin “jumper” that must be moved and it acts just like a switch. If you open the case and look at the PC board, you should see written somewhere on the board. The words stereo and mono next to a connector with 3 pins, two of the three pins will be covered with a small plastic “jumper”. Pictured below, is what the pins and the plastic “jumper” should look like. You should find the “jumper” covering the two pins next to the word “stereo”. Just gently pull up on the “jumper” and then move it over to the mono side and press down on the connector. In all cases the “jumper” should always connect to the center pin. You are just moving the jumper from the stereo pin to the mono pin. And that is all there is to it. From that point, just close the case and follow the instructions in the owner’s manual for running the amp in bridged mono mode.
Baron030:)
Here is a link to a copy of the owner’s manual: www.crownaudio.com/media/pdf/amps/125243.pdf (http://www.crownaudio.com/media/pdf/amps/125243.pdf)
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