Rotel RA 1062

I'd be grateful if someone could explain how this 60 watt amp can have a better grip on speakers - and thus sound more powerful - than some 100 watt amps.

I have heard it said that Rotel amps like to rock. Am I right in thinking that the 1062 is therefore probably not a good first choice for Bach and Mozart?

Or could it be tamed with suitable CDP and speakers?

 

Grip is more to do with current dlivery than wattage. Rotel put out decent current (amps) for what they are.

 

The Rotel 1062 is a surprising amplifier, especially for £600. I found it was very even handed across all genres of music and would be my first recommendation for anybody looking for an amp up to £1200. It does drive speakers well and has surprising control of their drive units. Mainly I believe due to the very good quality power supply. The amplifier is able to recover very quickly from transients and supply enough current quickly enough to stop and start drive units when the signal demands it. Wholly recommended

Cheers

Jason

 

The new (50 watt) Naim Nait 5i's supposed to be a real rocker/sub-£1000 contender too....

 

Thanks, but I'm not looking for a rocker.

I want a powerful amp that's good for classical music.

 

The way amplifiers are sold is on power where power (in watts) = ( V x V ) / R, where V is the AC voltage (usually RMS rather than peak or peak-peak) and R is the resistance of the speaker.

Now, look at the specs of many amplifiers regarding power into load. For example, you might well see that an amplifier is capable of 60W into 8 ohms and 100W into 4 ohms.

Put these numbers into the above equation and things aren't adding up. An amplifier that is capable of 60W into 8 ohms should be capable of 120W into 4 ohms (as the output voltage of the amplifier remains constant, and is limited by the power rails of the amplifier). In other words, the VxV remains the same, R has halved so power should double.

Why doesn't it? Power is also equal to I x I x R, where I is the current ouput of the amplifier. Thus, if you have 100W into 4 ohms, I x I is 25, so the amplifier is putting out 5 Amps. 60W into 8 ohms gives I to be 3.5A. So, even without the power doubling, you can see that the current requirement of an amplifier into a 4 ohm load is significantly higher than into 8.

So what? I have 8 ohm speakers.... Do you indeed? The impedance trace of any speaker is not flat, due to resonant nodes (at which the driver may move freely) and anti-nodes in the cabinet. A port, for example, is a deliberately introduced resonant node. This causes the impedance trace to vary quite significantly at very low frequencies. Higher up the frequency range, the crossover network of the speaker will provide a varying impedance with frequency (that, afterall, is the job of the crossover network). A "nominal 8 ohm" speaker may, in fact, dip as low as 3 ohms somewhere in the bass region.

Coming back to the original question, Rotel amplifiers are unusual among budget amplifiers in having quite significant power supplies that will allow the amplifier to deliver significant current. Why is the RA-1062 only rated at 60W into 8 and 90W into 4 ohms then? Because of distortion. With a 4 ohm load most amplifiers will have slightly higher distortion than with an 8ohm (you can optimise for a 4 ohm load instead, but the majority of speakers that the 1062 is likely to be used with are 8 ohm). Rotel have provided both ratings at the same 0.03% distortion level.

Another issue is that of the output impedance of the amplifier. In the case of the rotel, that is 0.053 ohms (as the damping factor is quoted as 150 into 8 ohms). Generally speaking, the lower the output impedance, the better. Some of the big rotel power amps have output impedances as low as 0.008 ohms.

 

What about yer Unison research Jerry not reccomending that, hear it's pretty good with all music and powerful too 80w/ch and under a grande

 

The VA rating of the power supply is often more helpful than the watts rating at 8 Ohms or whatever, particularly when pairing the amp with difficult to drive speakers.

 

Thank you for your informative response, Isaac.

 

Thanks for the thanks, but what I really want to know is did it make sense, cos if not I'll try and explain it another way...

 

Bloody smartass

 

ak - maybe so, but it is my job....

 

I love my UR to bits mate. I was under the impression that the man wanted a 'rocking amp' and the UR's too refined for that, IMHO.

I was listening to Vivaldi just now, Anne Sophie Mutter's version, and it's simply amazing everytime I listen to it. The UR combo, with the Dynaudio's, simply does the trick with this CD. I listened to Nigel Kennedy's version just before, and the recording is really thin and recessed compared to the Deutsche Gramophone (Mutter's) version.... and earlier I was listening to Crazy Penis....

There you go. I could actually go on and on about the Unico, but I'll stop just now...

Yeah, for a great amp under a grand: You've got to audition the Unison Research Unico!