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Jeff Rowland 535 Stereo Amplifier Review

amirm

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#1
This is a review and detailed measurements of the Jeff Rowland 535 stereo (bridgeable) amplifier. It is on kind loan from a member. I believe it costs US $5,900.

If you are not familiar with Jeff Rowland, it is a high-end audio company, known for their gorgeous machining of their cases that imparts a 3-D look. You can see that coming through the protective film which I chose to leave on:

Jeff Rowland Design 535 stereo amplifier Audio review.jpg

The unit is incredibly heavy for its small size. The back panel shows the most unusual binding posts I have seen:

Jeff Rowland Design 535 stereo amplifier back panel speaker connectors Audio review.jpg

Those big knobs rotate to tighten bar on two spade terminals. The feel incredibly nice. Alas, they don't mate with banana leads and I had to screw around to connect mine.

The amplifier is said to be balanced throughout including input transformer which is made with wire from Cardas (!).

Company only states that a switching power supply is used but says nothing about the rest of the functionality. From my testing, it seems to be class D which would explain why the amp stayed completely cool to touch under testing as if it was never on! The massive chunk of chassis aluminum is likely responsible for great thermal performance.

Amplifier Audio Measurements
As usual we start with our 1 kHz dashboard at 5 watts into 4 ohm:

Jeff Rowland Design 535 stereo amplifier Audio Measurements.png


Ah, this is disappointing. Distortion peaks to -80 dB which sets SINAD at an average number of 77:

best high-end stereo amplifier review 2020.png


This is way below stated of the art in switching amplifier design. Company specs are similar by the way so this is representative performance as designed.

Where specs don't match is in signal to noise ratio:

Jeff Rowland Design 535 stereo amplifier SNR Audio Measurements.png



Crosstalk curve usually gets worse with frequency (due to increased effect of stray capacitance) but here it is rather flat:

Jeff Rowland Design 535 stereo amplifier Crosstalk Audio Measurements.png


Frequency response is very good with no indication of interaction with the load:

Jeff Rowland Design 535 stereo amplifier Frequency Response Audio Measurements.png


Another shortfall from the spec is in power department:

Jeff Rowland Design 535 stereo amplifier Power into 4 ohm Audio Measurements.png


Jeff Rowland Design 535 stereo amplifier Power into 8 ohm Audio Measurements.png


Letting distortion peak up to 1% still doesn't give us what the spec says:

Jeff Rowland Design 535 stereo amplifier Peak Power Audio Measurements.png


I don't know how they get to 500 watts unless it is at even higher distortion levels.

As a way of comparison, let's see how the power curve looks like relative to noise and distortion of Hypex based NC400:

Jeff Rowland Design 535 stereo amplifier Power into 4 ohm Compared to Hypex NC400 Audio Measur...png


We have slightly more power although the NC400 I tested had a shared power supply. That aside, there is no comparison in noise and distortion department. The 535 way underperforms the Hypex.

Finally, here is an unfiltered output of the amplifier at 5 watts:

Jeff Rowland Design 535 stereo amplifier 1 kHz FFT Audio Measurements.png


We clearly see the switching waveform. Attenuation is better than 30 dB which is more than a number of other amps I have tested so that is good.

Conclusions
The Jeff Rowland 535 amplifier has beautiful fit and finish. And is solidly engineered to run cool and I am sure reliable as a result. It produces good bit of power which should be able to drive many speakers to desired loudness. Alas, it reinvents the wheel and makes it less round. Any amplifier based on Hypex modules will have as much or more power with far less noise and distortion and lower cost.

Bottom line, I can't recommend the Jeff Rowland 535 due to its high cost and average noise and distortion.

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amirm

amirm

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Thread Starter #3
I have a very positive impression of the company as well, having seen them at many audio shows.
 

wwenze

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I don't know how they get to 500 watts unless it is at even higher distortion levels.
The old peak vs rms trick?
 

direstraitsfan98

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#10
53ADF29E-8F26-4024-A721-16418089407D.jpeg


I’ve experienced using these binding posts myself when I was playing around with some Nagra gear. I really like these kinds of screw terminals. Current Pass Labs gear also uses a similar style of connector. It can get awfully cramped awfully quick, though.

Speaking of... would be excellent to get some of the current Nagra Classic line in for review. Has anyone expressed interest in loaning in one of those?

Thanks for the review.
 
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Chrispy

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When one sees all the various units Jeff Rowland Design Group has to offer at shows it's very impressive. There are some veryyyy amazing products that are built reallly solidly and are beautiful to look at too. It's easy to like the product.
I meant products at "high end" shows in general. Not a lot of substance in general but not familiar with his products as am simply not interested.
 

Doodski

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I meant products at "high end" shows in general. Not a lot of substance in general but not familiar with his products as am simply not interested.
I've been to the Vegas CES show 5 times attending as a salesperson and then as a buyer. You get to see a vast amount of high end gear. After awhile it becomes a mundane task but you keep going looking for those gems that people near never get to see but are legendary. Jeff Rowland is one of the gems. As a side note the porn section of the show is a real eye opener. Men and women hanging from chains with barely any clothes on and such. One meets the porn stars. I got many posters for the shipping receiving staff with signatures and commentary on the poster from the porn stars. The shipping receiving staff loved it and posted them on the walls of the warehouse.
 

Chrispy

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I've been to the Vegas CES show 5 times attending as a salesperson and then as a buyer. You get to see a vast amount of high end gear. After awhile it becomes a mundane task but you keep going looking for those gems that people near never get to see but are legendary. Jeff Rowland is one of the gems. As a side note the porn section of the show is a real eye opener. Men and women hanging from chains with barely any clothes on and such. One meets the porn stars. I got many posters for the shipping receiving staff with signatures and commentary on the poster from the porn stars. The shipping receiving staff loved it and posted them on the walls of the warehouse.
Meh. Legends are like those created by the usual idiots in audio?
 

Doodski

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I’ve experienced using these binding posts myself when I was playing around with some Nagra gear. I really like these kinds of screw terminals. Current Pass Labs gear also uses a similar style of connector. It can get awfully cramped awfully quick, though.

Speaking of... would be excellent to get some of the current Nagra Classic line in for review. Has anyone expressed interest in loaning in one of those?

Thanks for the review.
Put your pic(s) back up. :D
 

direstraitsfan98

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#19
Seeing gobs of goo like that dripped over the board gives me the heebie jeebies. I still have PTSD thinking of the time I had to undo this bad mod job to one of my retro consoles. Removing that gunk is the worst, just the biggest PITA ever. You have to apply heat enough to melt it, taking care not to heat up other things soldered onto the board near it and painstakingly remove it by dragging thin tools across to essentially slide it out.

I suppose the idea with this gear is he would swap out the entire board for a new one if something went wrong.
 

Doodski

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#20
Seeing gobs of goo like that dripped over the board gives me the heebie jeebies. I still have PTSD thinking of the time I had to undo this bad mod job to one of my retro consoles. Removing that gunk is the worst, just the biggest PITA ever. You have to apply heat enough to melt it, taking care not to heat up other things soldered onto the board near it and painstakingly remove it by dragging thin tools across to essentially slide it out.

I suppose the idea with this gear is he would swap out the entire board for a new one if something went wrong.
Yeah that white goop is a pain in the azz. The filter caps and coil oscillate with a high frequency square wave pulse width modulation (Maybe 30KHz - 60 Khz+?) and I suppose the goop helps to dampen the noise and mechanical vibration that breaks solder and stuff.
 
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