Jeff Rowland


I was reading in Stereophile about how the older Jeff Rowland Amps sounded great and were classics. The writer said Rowland was good up to the Concentra II but not the Concerto and anything with "rounded corners." I think the Concertos were where JR started using class D amps. Is that the case? Do all models use Class D now?

I'm sure I don't want anything with class D at this time as many reviewers have commented on the treble as being glassy or something wrong with the sound of it. The highs are what make or break a piece for me so I'm not going anywhere near Class D right now but am considering giving Rowland a try for a third system I'm building.
wireless200

Showing 3 responses by wireless200

Chad, I am a tube fan, just don't want the longer term maintenance issues. You can read threads and reviews and time after time the highs are always mentioned as not being quite right on Class D. Maybe it doesn't bother a lot of people. I've certainly heard my share of A and A/B amps that I didn't like the highs on too.

I'm an electrical engineer and know a little about amplifiers and after doing a little studying on how Class D works, I could see why it would sound not quite right. It works in a quite different manner from standard amplifiers. Class D is often referred to in terms of digital amplifiers and that's more or less how it works, doing very fast pulses almost like a bitstream but more like a discrete Fourier transform IMO. I think it probably suffers the same problems as digital recordings do. I think they could improve it if they increase the switching speed to a much higher rate. I'm sure technically the engineers decided to make it fast enough that it meets predetermined specifications but I think there's still a difference. An analogous situation exists for CDs. That's a 44.1 kHz sampling rate is supposed to be able to reproduce all the freqencies that the human ear can hear. I bought an album off of HD tracks and downloaded free samples recorded at the 96 kHz rate. I hear a big difference. Not in the audible frequencies but in the warmth I used to hear with albums and analog. I know I'm not supposed to be able to but I do. It's very clear and I had a friend over recently and he said the same thing.

I think Class D will clearly improve but like CDs it'll take some time. It clearly has some benefits such as power consumption, efficiency, and easy power. I think it's probably great for the consumer electronics, the HT crowd and others.

OTOH, according to Dan D'agonstino the output waveform is not clean. That's something fairly easily objectively verified. Lastly when someone says, this or that item is great but you have to be concerned with cables or upstream components, that's a red flag for me. I went through a lot of expensive equipment and I definitely know what you mean. A lot of the good stuff requires a lot more of the good (expensive) stuff to make it sound good. I don't like that. I finally settled on McIntosh for my main system and it makes 90% of what I listen to - which is pretty much everything - sound very good. Yeah, I don't get the amazing jaw-dropping sound I used to get on 10% of my recordings with some of the high-end stuff I've owned but I can listen to current system for hours. I have good cables, speakers, interconnects but I don't sit there and think about how I need to improve it all the time like I used to. Anyway kind of a long rant but why not? It makes for interesting discussion. And who knows - one listen to a JRDG Class D piece might and I might find it's what I've been looking for all this time.
Guido, when you say the modules are analog devices, I think that paints with too broad a brush. The actual switching controller and output stage still put out a series of variable width pulses or rectangle waves that are subsequently fed into a filter that converts or "filters" them back into analog looking sine waves. The *input* to the switching controllor can be analog (or digital). Still, ultimately the signal is formed by rapidly switching or pulsing a circuit on and off. This technique is how the effeciencies are gained and basically what a Class D amp is. This is different IMO than simply amplifing an analog signal. Maybe they've got it worked out. I think I noticed a Bel Canto device in the Class A components of Stereophile. I don't think it could be that bad since that's the case. The idea and benefits are appealing but the implementation and sound of Class D I'm not so sure about. I bet you find 10 to 1 posts saying it doesn't sound right. Kind of like what you read about McIntosh or Krell. :)
Brian, I agree. I got my answers on the JR "classic" JR products and kind of steered the thread to a class D discussion.

Guido, I think you miss my point - meant to be mildly humorous - about Krell and McIntosh. I was simply acknowledging the fact that even good gear gets bashed regularly. I'm open minded but no local dealers here for Bel Canto and JR. I may buy a used piece to try.

One area I think Class D may work well in is for speakers that need a lot of power with low impendance drops. Those characteristics apply to a lot of high-end speakers including a pair of Aerials I own.