Rotel RA870BX vs Sanui B2102

hifi junky

Hi everyone.
I have question concerning two amplifiers that I am using.
First off I am using a pair of SDA 2B's.
I recenyly bought a Rotel RA870BX, this is a 1980's intergrated amplifier, rated @ 80 wpc into 8ohms. (common ground). I only used this amps preamp output.
The power amplifier that I was using to drive these speakers is a Sansui B2102, 200wpc into 8ohms. (non Common ground)
But using this power amp, I am not able to use the provided interconnection cable with the SDA's.
I decided to connect my speakers to the Rotel, use the interconnection cable between them, and give them a listen.
Wow! To my surprise, the sound level from Rotel was just as compareable and equel to that of the Sansui. I had expected a obvious noticable differance based on the specs alone.
I am now considering selling the power amp, as I am now able to take advantage of the interconection cable with no comprimise to the volume output and my prefered listening levels.
Any explinations and opinions welcome.
Thanks

agfrost

Well, the 2Bs are not overly demanding of wattage to attain volume (~90dB efficiency), so you can attain decent volumes with your 80wpc amp. Just don't go berserk with the volume knob and life should be just fine.

On the other hand, by having the SDA cable connected, you're finally hearing the speakers as they're meant to sound, with the wide soundstaging that is the hallmark of the breed.

In the future you can look to source a higher-powered amp that's common ground (I've got a 200WPC B&K amp at the moment for my 2Bs), or if your 2Bs are pin/blade models with serial numbers above ~14120, you can look into an isolation transformer option. Many members, myself included, have built/are currently building a "Dreadnaught" isolation transformer that will improve sound of common ground amplifiers, as well as allow for the use of non-common ground amps such as your Sansui. *Or*, you could try to source the quite-rare Polk AI-1 interface, which is a smaller transformer built into the interconnect cable, which would allow you to use your current Sansui as well.

Here's a couple of links for your reading pleasure:

http://vr3mods.com/uploads/SDA_Handbook_2011_Rev2.pdf
http://forum.polkaudio.com/discussion/comment/950393#Comment_950393

Good luck!

Jay

hifi junky

Looking forward to reading the provided info.
Thank you for your reply.