Are there any high quality Class D (or equivalent) amps that do not interfere with FM reception. (I read that NuForce amps, for example, destroy FM reception.)I would like to try one out in my bedroom system but I listen to FM a lot in that room and don't want to lose my recetion. Thanks.
All the NuForce amps currently available have chokes on the output wiring to supress FM interference. That said, it is possible that if the amps are located very close to the tuner it might still nock out a few weak stations. Stations with moderate to good signal strength should be unaffected.
Other class-D amps do not sample at the ultra-high frequencies that the NuForce does, and so would be less likely to cause this problem. Of course many other class-D amps do not sound nearly as good as the NuForce, but heck, choosing a poorer performing, less musical class-D amp may be an acceptable tradeoff to be able to pull in a couple of weak stations that you can barely get anyway...
The Nuforce made FM reception almost impossible. It messed with the Tivoli One of a friend of mine while auditioning the amp at home. This situation was a little better with a sSiltech shielded cable. Now some say that FM reception is not important. Maybe, but that is not the real question. Remind that almost every audiophile wants an RF/EM free enviroment, for the blackest background, noise free purer tone. And for that lot's of them use shielded power cords on their digital gear (CD and DAC) for less interference and better music. I've never heard about a CD or DAC making interference in radio reception!! The NOISE made by this amp is really a issue. Just for the record, the Bel Canto class D amp that were also demoed made FM reception possible. At the end the question is "who want's a amp that causes RF noise?".
PS- This comments are aonly about the noise question and not about the sound of the amp.
The review of the H20 M250SA amp over at Ultra Audio compared the effect on FM of the H20 amp (none) with that of the Nuforce Reference model. The Nuforce caused interference in other rooms of the reviewer's home. It sounds as if the Nuforce choke is optional and that makes me wonder if it has an effect on the sound.
I have had no FM issues with either my eAR Two or H20 S250. This with my vintage tuner placed 6 inches above the amp. I use RG6 quad shield to connect to the attic-mounted attenna using a balun-free adapter to the tuner's 300 ohm connection.
The eAR has a thin stainless steel chassis and the H20 has a heavy metal chassis. Both use the same B & 0 module. And, both amps can be powered up with no load without endangering the amp.
BTW, the reviewer did not find a tremendous difference between the Nuforce and H20 amps soundwise - more of a flavor preference. I am not sure that the higher bandwith equates to wonderful sound theory holds water. High bandwidth designs have come and gone over the years.
I will chime in on this one- my experience was with the Bel Canto Ref 1000 monos (similar topology)- same problem, even worse- actually made a few of my television stations snowy when the tv was even plugged into the same line conditioner (BPT 2.5) as the amps!! Not to mention my fm reception was non-existent once the amps were on- no way could they stay in my system...
I must be eating right because I haven't any FM issues with my SE's. I have clock radios, HT receiver with FM, and even some boom boxes. My yagi antenna is on the roof of my ranch style house and I'm using 75 ohm shielded cable.
As Dotsystem said above there is no interference whatsoever with the H20 amplifiers. I should mention that I have a pair of them for sale currently but that does not take away from the fact that they don't effect FM at all. I must say that the H2o's sound wonderful and they are no compromise to the Nuforce. Bob
Interestingly, no one except Vic said anything about the antennae they're using. And he has a directional yagi that's well away from his locally generated rfi. So if you're using a dipole FM antenna in the same room as your digital gear, what do you expect?
That said, a lot of rfi can be dumped into your power lines by the PC on the digital equipment -- shielded PCs help keep it from broadcasting into the air but not from contaminating the house wiring itself. Using a conditioner or regenerator with digitally filtered outlets can keep this from becoming a problem -- and eliminates the necessity of plugging the digital gear into a separate circuit. .
I use shielded power cords and an Exactpower EP-15A. The antennas I have used are a Magnum Dynalab ST-2 and a large Godar. I remember trying each in the same room as the system. In the case of the ST-2, the eAR amp was in use and the H20 with the Godar.
There was no noise problem. The reception is better with the antenna in the attic through.
I am doubtful of of typical filters curing a noise problem of sufficient magnitude. I wonder where the FCC stands on components generating noise...
The Nuforce is the only brand I recall as having the reported noise problem as well as turn on noise and the no-load vulnerability. These strike me as implementation issues and not reflective of class D amps in general.
It may be that only the Nuforce models have FM noise problems to solve.
I just received my H20 Stereo 250 Sig back with an upgrade to the newest version ICE modules and V-Caps ugrades. I am presently breaking it in with a JVC FM tuner and have absolutely no problems with FM interference.
I have my vintage tuner sitting right besides (6 inches away) two Bel Canto S-300 amplifiers and have had no trouble with FM interference. I am using a small passive FM antenna located about 1 foot above the tuner.