Lowering noise floor with a Rotel 1090 and RF7s

[Zen Traveler]

I just realized there are two of you with the same problem. [^o)] The difference between my mid level Denon AVR 3805 driving my HT below and the Denon THX ultra II AVR 4806 (and prior AVR 4802R) was considerable, especially at louder volume. I've balked at trying a 2 channel amp with my RF-7s because A) I already love the sound and I have no hiss at all with my ear to the speaker and the volume turned to "0" (with nothing playing, but everything on).

Fwiw, I wonder if in the $2,000 to $3,000 range, for driving speakers in a Home Theater situation it would be more prudent to get an upper end AVR instead of trying to piece together a (relatively) cheap AVR with a 2 channel amp. {edit: although I realize both posters are in a situation where they already have their older AVR}

[MrMcGoo]

I like leok's solution to the problem. It has a good chance to work and should not be too expensive.

The idea that receivers cannot work well with external amps is incorrect. Receivers do need extra engineering to quiet the digital noise created by the many DSPs used. Most consumers are not willing to pay the bucks needed to get the better preamp section.

The biggest weakness in receivers is that they cannot drive difficult loads with 5 or 7 channels driven at the same time. They tend to lack the needed power supplies and sufficient output devices.

Bill

[Fast1]

I guess the way I am understanding the voltage attenuator, you are wanting to half the input voltage to the amp? Or is this a separate variable rheostat? My concern is that I am able to use all of the volume out of the receiver so if I simply half the voltage, I will drop my output too. One of the things being done in car audio I think is to boost the voltage to help with noise. I will have to check.

One of the other things that surprised me is how much mid range I am missing with the Denon!!! I think more because the crossover points and not able to full range the mains and run the sub. The xover is set on large and at 80hz. I am not sure if I can getting a cascading xover effect or just mismatch but with the Outlaw, the 7s woofers actually move! With the Denon, things are just sounding thin and light.

Like I say, the Outlaw was well known for having noise problems so I guess now I need to test something else that is more silent. I would also like a better explanation of how the attenuator will repair this problem.

[leok]

Brandon,

If you half the voltage (and you may want to drop it by something greater like 1/5) you will be able to use all of the volume out of the receiver, it will simply be moved so that you get a better ratio of signal to noise. You're not having any problem getting things loud enough are you? It's just that there is a lot of background noise.

By attenuating the output, the noise floor is reduced and you have to turn the pre volume higher to get the amplitude you want (that's a good thing). It's worth a try if you can easily obtain a simple stereo variable attenuator or can make a 1/5 divider.

Leo

[NewMount]

As everyone has already pointed out: The less noise, the better (obviously), both in the preamp and in the poweramp. Generally speaking, surround receivers are horrible when it comes to noise, so you might consider stepping up to a better unit or a dedicated high-quality surround preamp. However, even with a low-noise preamp and a low-noise power amp, the noise can still be audible since the gain of normal pre-power combos is tuned for much less efficient speakers than Klipsch. The solution is, as several people have already mentioned, to reduce gain in the power amp thus forcing the preamp to output a higher signal (using more of the dynamic range). For some strange reason, very few power amplifiers have a gain switch or potentiometer. In the old days (80's to mid 90's), most power amps had a gain potentiometer: Denon, Sony, Luxman, Accuphase, McIntosh, etc. The only power amp brands I can think of today that have a gain switch are Accuphase (I have one, it works great at -12 dB) and GamuT (selectable gain using jumpers on the inside of the amp). Do you know of any other brands? Could it be that the vast majority of power amp buyers have inefficient speakers (sensitivity around 90 dB) and that the audio electronics firms concentrate on them?

By the way, has anybody tried the Rothwell in-line attenuators? You can find information about them here:

http://www.rothwellaudioproducts.co.uk/html/attenuators.html

http://www.enjoythemusic.com/magazine/equipment/0803/rothwell.htm

I'm a bit sceptical towards attenuators since they can affect the sound, though. Does anybody have any experience from introducing attenuators in the signal path? I think they must be of high quality in order not to degrade the sound.