Jeff Rowland Model 501 - Help ...

@Macrojack

It is very difficult to find out the truth in HiFi ... in general. For example: you have different JR units (which are as far as I remember the later models) and completely different TV technology. FM is though the same.

I had for example the opportunity to talk to Jeff Rowland on Muenchen HiFi show, two weeks ago. And I asked him explicitely about radiation of 501's and he told me that they are safe concerning that matter. He told me even that JR has in their testing room an FM tuner placed on these mono's and that there are no degradation of FM signal.

I have no reason not to believe Jeff Rowland but friend of mine does not have any reason not to tell me the truth. He will though repeat the test in a completely different system (another friend of ours will be involved).

The only conclusion is that the radiation might be, under certain circumstances, an issue, depending probably on many factors. But that risk is to high for me ...

I'm very skeptical of these results. I have a Rowland Capri preamp and 102 amp stacked next to my Kenwood KT-917 tuner and sitting beneath a Panasonic plasma TV, which hangs on the wall above and behind. The amp is 7 inches from the tuner and about 18 inches from the TV. There is no indication whatsoever of interference or noise. I'm using the Rowland 102 to power a pair of 108 db efficient horns so I'm sure the noise would be obvious if it existed.

The latest Bel Cantos have a filter that keeps out the Class D generated interference.

I promised to provide a feedback from a friend who tested these Jeff Rowlands ... so here it is ...

He installed JR Model 501 monos in a system where Primare was a preamp and the speakers are Harbeth. CRT TV was about 20 cm away from monos (they were put one on another) and the FM tuner was somewhere about 80 cm away from these monos. Power cords of these monos were plugged into separate wall mains from the rest of the system.

He could hear a brum on all radio stations (cable network reception) and the picture on some (not all) TV stations was clearly degraded. It is a clear evidence of some, not negligible, radiation from these units.

Therefore I decided not to go after these babies although, as I already mentioned, the offer is really good one. That is pity, because I know that they can produce, with the right speakers, excellent sound reproduction.

I wish to thank to you ALL for your advices and comments ...

Dejanm - As far as I know tweeter has very high impedance at 0.5MHz therefore power delivered will be very low. In addition there should be no intermodulation products because membrane cannot move at these frequencies.

Kijanki,

Thanks a lot for your answer. I asked a friend of mine to test this JR's by putting them near TV and FM radio sets and after I get the message from him, I will also let you know ...

One question more: this carrier signal that you are mentioning, that travels through speaker cables - does it produce any noise in the speaker tweeters ? I have Focal Electra 1027 Be speakers with Berillium tweeter. All cables are Crystal Cable (very well shielded). Speaker cable is Crystal Cable Micro.

Dejanm

Any amplifier radiates - even linear one. The question is amount of it. I have Rowland 102 directly under TV and I don't see any evidence of it. I tried different analog (and digital) channels - some with very weak signal and I cannot see any difference between amp ON and OFF (unplugged).

Class D produces about 1% of the carrier noise on the speaker cable. This carrier is about 0.5MHz and the speaker cable is a very bad antenna to radiate is (way too short). At this frequency 1/4 wave antenna is about 500 feet. Once you get under 1/8 wave antenna becomes very ineffective. It is also matter of distance of course. Capacitive coupling might be another problem if you have poorly shielded (or not shielded) IC or antenna cable.

Jeff Rowland decided to put only balanced input on my 102 amp - very mature decision.

I mentioned that any amp radiates. Linear amp (any amp) takes its power from mains in very short current spikes of huge amplitude. These narrow spikes contain some amount of radio frequencies and can contaminate audio as well (that's why power cord shielding is so important).

If you cannot audition 501s try any other Icepower - they sound very similar. If I would buy class D again I would probably go either for the Rowland with power factor factor correction unit inside (like extra power supply) or second generation of Bel Canto Ref1000 (mk II) that has similar addition inside. If you need integrated - go for Continuum 500 that has great Capri preamp and Power Factor Correction unit built inside (great bargain). Power Factor correction unit alone (works with 102, 201, 501 etc) is $1500.

Thank you very much for your comment. You saved me from having a lot of trouble. I wonder only how they get all these certifications, when having such a product ... ?

I had trouble with FM reception with my Rowland 201 monos. I finally solved the problem by going with a FM Reflect antenna from C.Crane Co. and setting it up as far as possible from the amps (about 4 feet). Even at that distance I had to adjust it several times to finally get a signal. I am using a Sangean HD radio tuner but had the trouble with a Sony tuner as well.