Power to 703 ´s

[b&w fan]

Do you think it would make a noticeable difference in sound quality choosing the Rotel RB1090 versus the Rotel RB1080 to power the BW703?.

Is it worth the extra US$ 1000 to buy the RB1090?

(I can not audition them before making the decision of buying)

[Aussie Geoff]

Hi,

I have had both the RB-1080 and the RB-1090 in my system and, while both are good - the RB-1090 is very special indeed - it has total control over the speaker and many more watts (from memory 30-40 operating in class A before it switches to class B. You won't regret it. The other choice is the new RB-1092 all digital amps from Rotel - a little more again but (for many ears) even better...

Either way (RB-1090 or RB-1092) you are future proofing in that both are capable of driving the 800 series, well (especially the RB-1092) should you decide to sucumb to the upgraditis disease later

Geoff

[Aussie Geoff]

Hi,

I've received a PM requesting further explanation as to what Class A/B means

Original amplifiers (valve and transistor) were low powered and ran in a mode when the valves or transistors were always powered on and running at a voltage equivalent to there maximum power. Essentially they could (and can) produce their musical notes without ever switching the transistor or valves off or near off (where there is a small non-linearity) creating distortion. However the handicap is that they produce heat equivalent to their maximum power. As power demands / expectations grew - Class A amps started to warm rooms. Indeed there are still monsters out there from some companies such as 500W Class A amps that burn 700-1000W of power and run like heaters.

To solve this designers first came up with a design called Class B where they switched the transistor on and off as it passed through the sine wave cycle of musical frequencies. Early transistors weren't that good and this had a noticeable harshness. (still does)

So they came up with a compromise known as class A/B where the amplifiers run in class A up to a certain power level (you will see this referred to as the amplifiers 'bias and they feed the transistors a voltage equivalent to a few watts') and then smoothly switch to class B. This has most of the benefits of class A without the killer heat penalty.

Now the better sounding class A/B amplifiers will typically have a higher bias (class A rating) so all but the louder notes are totally reproduced in the amplifiers class A mode. Think of amplifiers such as those from Classe and Krell - who all after special complex circuits to maximise the class A operating mode - often even dynamically varying it.

So (from memory) the RB-1090 has something like 35W or more class A which is 95% of your listening. as a result - it is very smooth and sweet at low level detail.

Try this link for more

http://en.wikipedia.org/wiki/Electronic_amplifier

or use Google for 1000's of links!

Hope this helps.

Geoff