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Amp Match for Vintage JA Sound

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mellotone View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mellotone Quote  Post ReplyReply Direct Link To This Post Posted: 16 February 2017 at 5:07am
Originally posted by Earplug Earplug wrote:

Originally posted by mellotone mellotone wrote:

Yes DubSS, I'll need to revisit this for guidance when it comes time to connect.
Many thx!


You need to check which pin on the input XLR of your amp is 'hot', ie in phase. Most amps use pin 2, the (old) Crests, pin 3.

So, if you mix amps, you need to make some special cables for the input (Pin 2 on crossover/desk to Pin 3 of amp), use the phase flip on the crossover, or swap the speaker cables around, ie '+' on the speaker to Black binding post, '-' on speaker to Red binding post.    Smile



Thanks for sharing that nugget of info Earplug, I've added it to my build notes and will make sure to revisit when the time comes.

Just wanna thank those who've chimed in to share advice and opinions on this topic - much appreciated.

My 8001 arrived today and am currently seeking a healthy 7001/6001 for mid-duty to complete my amp needs at this time.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote mellotone Quote  Post ReplyReply Direct Link To This Post Posted: 16 February 2017 at 5:30am
Originally posted by Elliot Thompson Elliot Thompson wrote:

On the used market scene, lower wattage Crest Amplifiers tend to cost more than higher wattage Crest Amplifiers when you take into consideration how much power each amplifier offers. It is a matter of supply and demand. Do not be surprised if you see a used Crest 7001 costing less than a Crest 6001.

 

I cannot count the amount of times I have purchased amplifiers on eBay that were four times the rated wattage required for the loudspeaker. This is due to having more high wattage amplifier listings on eBay offering a better price than, low wattage amplifier listings based, on the brand I was seeking. 

 

Best Regards,

 


@Elliot
Noticed you also reside in the states and have recognized your endless source of knowledge with all-things-sound on countless other threads over the years. 

So just curious if you (or anyone else) have any thoughts on how to safely supply power in the land of 120v to an amp rack that consists of these 3 power amps (8001, 7001 & RSD 800B) + additional components associated with a small/medium size reggae soundsystem, such as custom preamp, echo/delay unit, valve phono stage, turntable etc.

What's the best way to link it all up together in a way that allows for the most versatility / compatibility at small venue types (bars, hotels, community centers, ect.)?

Guessing a power distro unit is overkill for this modest setup? Or is there a unit made for this type of smaller application I should consider?

Or is this a non-issue and just plug it in?




Edited by mellotone - 16 February 2017 at 5:44am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Elliot Thompson Quote  Post ReplyReply Direct Link To This Post Posted: 16 February 2017 at 9:37am

The Crest 8001 will be fine on a 20 ampere circuit driving a 4 ohm per channel load.

Power Consumption is 20.4 amperes at maximum output using a sinusoidal waveform.

 

The Crest 7001 will be fine on a 15 ampere circuit driving a 4 ohm per channel load.

Power Consumption is 13.8 amperes at maximum output using a sinusoidal waveform.

 

The Studiomaster RSD 800B requires the least amount of current of the three and would operate properly on a 15 ampere circuit. The Sudiomaster RSD 800B consumes a mere 3.8 amperes at maximum output using a sinusoidal waveform.

 

The above current requirements will be lower as music has a lower duty cycle than a sinusoidal waveform. So you should be able to operate everything on a single 20 ampere circuit. However, if there are two circuits available (Such as a quad receptacle with each pair offers 20 amperes) it will ensure unexpected power outages if you decide the drive your system very ragged.

 

Most commercial buildings have multiple 20 ampere circuits available and, can guide you to such receptacles to attain the proper termination. If you need an extension cord, do not buy anything smaller than 10 AWG cable. That should prevent any heavy loss of transmission (voltage drops) from the receptacle to your amplifiers up to 50 feet.

 

You can buy the cable and build your own extension cord from Home Depot as it will cost less than buying one ready made.

 

While you are there, pick up a Multi-Meter. Multi-Meters come in handy to check the voltage rating of a receptacle. Since you are planning to play in bars, you want to know where the voltage stands before you plug your sound system in the bars receptacle(s). Any voltage rating ranging from 121.6 - 125.5 volts is fine. Any thing lower than 120 volts could possibly have something else running heavily on that circuit.

 

 

 

Best Regards,  



Edited by Elliot Thompson - 16 February 2017 at 9:39am
Elliot Thompson
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