Amp question

[Kevin Poirier]

Question. How good is a Rotel RB-985 MK II? And is getting one for $375 a good deal?

 

[lovinthehd]

They have a good reputation. 5 x 100 wpc (@8 ohm, don't see a 4 ohm spec) amp for $375 sounds like a decent price if in good shape, comparing to some sold units on fleabay. Hard to know if that will work for your purposes, tho. Any idea how old it is? Looks like it was released about 18 years ago...and had an mrsp of $999.

 

[Kevin Poirier]

No idea. It’s being sold by a high end store a state over

 

[PENG]

I wouldn't pay more than $150 or $200 if in top condition. It's not that powerful for a "power" amp, compared to a $599 AVR-X3400H, it may get you 1 to 2 dB at the most more output at clipping.

 

[Kevin Poirier]

I wouldn't pay more than $150 or $200 if in top condition. It's not that powerful for a "power" amp, compared to a $599 AVR-X3400H, it may get you 1 to 2 dB at the most more output at clipping.

Thanks

 

[lovinthehd]

Kevin, it would help to know what speakers you need to drive and your other equipment...

 

[Kevin Poirier]

Kevin, it would help to know what speakers you need to drive and your other equipment...

Denon AVR-X4300H & B&W 683 S2, 685 S2, & HTM-61 S2

 

[lovinthehd]

Thanks. What problems are you having now with the Denon where you're looking at external amplification? If you do add amplification I would suggest at least double the power of what you already have....which that Rotel unit doesn't have...as Peng pointed out. You might also want to look at amps that have better 4ohm capabilities than that Rotel seems to have. Your avr is possibly already more capable than that Rotel in that regard, but hard to know (couldn't find much on the 4 ohm capabilites in the way of a bench test).

 

[Kevin Poirier]

Thanks. What problems are you having now with the Denon where you're looking at external amplification? If you do add amplification I would suggest at least double the power of what you already have....which that Rotel unit doesn't have...as Peng pointed out. You might also want to look at amps that have better 4ohm capabilities than that Rotel seems to have. Your avr is possibly already more capable than that Rotel in that regard, but hard to know (couldn't find much on the 4 ohm capabilites in the way of a bench test).

Those speakers seem to lie thee power. Also, in the next year I want to heights and the Denon will only do out of the four without external amp.

 

[lovinthehd]

Like the power? That boils down to impedance and phase angle. B&W speakers do usually present such challenges from what I've read. I'd get a much more powerful amp if you want to address that more than your avr does....but somewhat depends on budget, which is?

 

[PENG]

Those speakers seem to lie thee power. Also, in the next year I want to heights and the Denon will only do out of the four without external amp.

HD is spot on about the Denon may actually be more capable, in terms of 2 channel driven simultaneously. Below is the bench test results by S&V for the AVR-X4200W. The AVR-X4300H should performed equally well if not slightly better.

Test Bench

0.1% THD 1.0% THD
Two Channels Continuously Driven, 8-Ohm Loads 124.3 watts 149.2 watts
Two Channels Continuously Driven, 4-Ohm Loads 215.9 watts 239.7 watts
Five Channels Continuously Driven, 8-Ohm Loads 94.6 watts 118.0 watts
Seven Channels Continuously Driven, 8-Ohm Loads 76.8 watts 91.9 watts

Read more at https://www.soundandvision.com/content/denon-avr-x4200w-av-receiver-review-test-bench#cH1skKxfqviF8u0f.99

You can see from the graph the total harmonic distortions stayed below 0.05% right up to 120 W and around 0.01% around 100 W, 2 channel driven.

It is easy to find out if you need more power, use the calculator below to get the max spl, come back to tell us the results and then we can make some recommendations before plunging $375 into an unknown quantity due to the relatively anemic output and age of that Rotel amp.

http://myhometheater.homestead.com/splcalculator.html

Note: For sensitivity, enter 85 dB instead of the specified 89 dB because this calculator based on dB/1W/1m, not the specified dB/2.83V/1m

 

[Kevin Poirier]

HD is spot on about the Denon may actually be more capable, in terms of 2 channel driven simultaneously. Below is the bench test results by S&V for the AVR-X4200W. The AVR-X4300H should performed equally well if not slightly better.

Test Bench

0.1% THD 1.0% THD
Two Channels Continuously Driven, 8-Ohm Loads 124.3 watts 149.2 watts
Two Channels Continuously Driven, 4-Ohm Loads 215.9 watts 239.7 watts
Five Channels Continuously Driven, 8-Ohm Loads 94.6 watts 118.0 watts
Seven Channels Continuously Driven, 8-Ohm Loads 76.8 watts 91.9 watts

Read more at https://www.soundandvision.com/content/denon-avr-x4200w-av-receiver-review-test-bench#cH1skKxfqviF8u0f.99

You can see from the graph the total harmonic distortions stayed below 0.05% right up to 120 W and around 0.01% around 100 W, 2 channel driven.

It is easy to find out if you need more power, use the calculator below to get the max spl, come back to tell us the results and then we can make some recommendations before plunging $375 into an unknown quantity due to the relatively anemic output and age of that Rotel amp.

http://myhometheater.homestead.com/splcalculator.html

Note: For sensitivity, enter 85 dB instead of the specified 89 dB because this calculator based on dB/1W/1m, not the specified dB/2.83V/1m

Thank you. This is helpful