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D75A


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#1 Fred

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Posted 28 February 2006 - 10:34 PM

Hello to all,

I have an opportunity to purchase two used D-75A Crown amplifiers, and would appreciate it if you could shed some light on any the following questions:

1- Would this amp pair well with the Electro-Voice (EV) S40 speakers? Also, would you recommend any other speakers to go with this/these amps ?

2- When the amps are in mono mode are they only able to power 8 ohms and above speakers, but can go below 8 ohms when not in mono mode, why the difference ?

3- Most amps also have a rating of AMPS as well as watts, why is the amps rating not available for this AMP?

4- What is the going used price for this amp in U.S. dollars.

5- Is there an adapter available to go between the amps inputs and RCA connectors, and if so, is there an easy to find distributor that carriers them ? All of my components only accept RCA connectors.

6- How can I tell how old the amp is ?

7- What year was the D75A amp first made ?

8- Are these amps still in production today ?

9 - What type of customers purchase this type of amplifier, I assume that in most cases they are not used for home use.

Thanks to all, and please excuse any fairly obvious questions, I am far from an expert in this field, as I am sure you can tell.

Fred

#2 DGlass

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Posted 01 March 2006 - 01:03 PM

1- Would this amp pair well with the Electro-Voice (EV) S40 speakers? Also, would you recommend any other speakers to go with this/these amps ?

I couldn’t find the S40 speakers on EV’s Web site so I had to Google a Data sheet……….
Although the D75A would power the S40 speakers I wouldn’t push it as it would be under powering the S40s. The S40 speakers are rated for 160 watts Power Handling Capacity (approx. Continuous Power).

2- When the amps are in mono mode are they only able to power 8 ohms and above speakers, but can go below 8 ohms when not in mono mode, why the difference ?

In Bridge-Mono the speaker load is floating between the two positive output terminals of an amplifier. As the one output side swings high the other side is swinging the exact same amount low. The load basically has a floating ground so the two sides of the amplifiers would see a maximum of ½ the load impedance.
A 4-ohm load in BM mode would "basically" be the same thing as a 2-ohm load on each channel in stereo mode.
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Since speakers are not fixed impedance devices the impedance will very with frequency. At certain frequencies the impedance of a particular speaker could be below the listed nominal impedance. So a 4-ohm load could be well below 3-ohm at certain frequencies. Divide 3-ohms in half and each side of the amplifier could be looking at 1.5-ohms or less. This is basically a short to an amplifier and will cause an amp to eventually thermal and go into protection.

3- Most amps also have a rating of AMPS as well as watts, why is the amps rating not available for this AMP?

This number can be given in one of two ways sometime both are given sometimes both are not. From the Engineering and Data sheets the specs for the amplifier AC main Current draw is less than 100 watts and 150 watts max.
http://www.crownaudi...ents/138308.pdf ://http://www.crownaudio.com/gen_htm/e...nts/138308.pdf ://http://www.crownaudio.com/gen_htm/e...nts/138308.pdf
http://www.crownaudi...amps/136711.pdf

Using these numbers and plugging them into Ohms Law were A=W/V we get A=100/120 or .83 amps and a max of A=150/120=1.25 amps.

A better look at this would be to look at the current draw under a test application that would be close to real world use under load. This can be seen in the Power Matrix found in the back of the amplifier’s owners manual on page 16.
http://www.crownaudi...amps/125243.pdf

In this you will see that the D75 amplifier max average power draw to be about 55 watts(.46amps)/4-ohms per channel, 40 watts(.33)/4-ohms per channel, 25 watts(.2 amps)/4-ohms per channel, 110 watts (.92 amps) Bridge-Mono

4- What is the going used price for this amp in U.S. dollars.

I would say to check E-bay or some place like Daddy’s Junkie Music, Pro Audio Marketplace (just to name two that I Googled),  that deal in used pro audio gear as we do not keep a running list of amplifier used pricing.

5- Is there an adapter available to go between the amps inputs and RCA connectors, and if so, is there an easy to find distributor that carriers them ? All of my components only accept RCA connectors.

You have two choices either an XLR to RCA adapter cable available at most music stores or a ¼” to RCA that is also available at most Stereo Dealers and Radio Shack.

6- How can I tell how old the amp is ?

There are two ways to tell. One is if on the serial number sticker there is a four digit code. The middle two numbers, of this code, will be the month of manufacture and the outer two will be the year.
i.e. 0123 the “12” would be December and the “03” would be 2003.
The other is to call us and we will try and run the serial number to see when it was originally invoiced.

7- What year was the D75A amp first made ?

The D75A came out in the late 90s

8- Are these amps still in production today ?

Yes.
http://www.crownaudi...m/amp_htm/d.htm


9 - What type of customers purchase this type of amplifier, I assume that in most cases they are not used for home use.


Some are used for Home, some are used for monitor amplifiers for for recording studios, broadcast studios, video production to live sound. If the amp matches the speaker power need it will do the job.