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Old 1st June 2010, 10:31 AM   #1
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Default NAD372 query

hi, i wonder can anyone help?
RE my NAD c372 integrated amplifier. it says in the manual that if connecting two sets of speakers do not let the impedance go below 8ohms. i wish to use a combined value of 6 ohms. obviously the amp continues to work, i assume all that can happen is that if driven to hard the amp will over heat and i assume an auto reset cut out will be activated.

does the amp thermaly cut out? if used at moderate volume levels only is damage likely to occur?

thanks for your time.
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Old 1st June 2010, 12:01 PM   #2
Mooly is online now Mooly  United Kingdom
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It's almost certainly OK.

Speaker impedance is a dynamic quantity... it's not what you get when you measure the "resistance" on ohms.
My B&W 703's for example are classed as "8 ohm" yet the minimum impedance at certain frequencies is 3 ohm (they are the manufacturers figures)

So I wouldn't worry... yes the amp will run hotter, but normal listening levels are low compared to sine wave testing.
Is the amp thermally protected... I would say not... as that adds cost.
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Old 1st June 2010, 01:12 PM   #3
Bill_P is offline Bill_P  United States
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Quote:
Originally Posted by Mooly View Post
It's almost certainly OK.
Is the amp thermally protected... I would say not... as that adds cost.
Instead of guessing I looked at the owners manual (PDF from the NAD site) and it indicates thermal protection is a feature. A quick perusal of the service manual shows two thermal protection devices on both the left channel and right channel amplifier boards.
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Old 1st June 2010, 01:49 PM   #4
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Default thanks

thanks for the quick replies, i did not know that impedance varied dynamically. i suppose i will chance using the two sets together at reasonable volume. but it sounds as if there are some safety features anyway.

if anyone has the time or can be bothered: if the amplifier is fine to drive a single 6ohm set of speakers, why is two sets totaling 6ohms more of a no no. surely if just driving a single set, i could be driving large speakers perhaps requiring more power than two smaller sets.

also, are there any pitfalls in running speakers of different impedances in parallel other than watching that the total impedance does not get too low?

thanks again, very helpful. ben
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Old 1st June 2010, 03:10 PM   #5
Bill_P is offline Bill_P  United States
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Speaker impedance varies greatly with frequency. The single published number like 6 Ohms is of almost no value in assessing amplifier load. The C372 has comprehensive enough protection that if it isn't shutting down then the load is ok. Do be sure not to stack equipment on top of the C372 as it needs unrestricted top side ventilation. The C372 is a nice amp - I have one and enjoy it.
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Old 1st June 2010, 04:45 PM   #6
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NAd ..."equipment "of this class has a reputation of blowing transformers before blowing the outputs... often their transformers are way to marginal
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