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Rotel OMG!

I haven't had a whole lot of experience with Rotel products in the past but I had a receiver laying around RX-940 AX which is very pleasant and actually quite good sounding but I never thought of on an audiophile scale as a must have. I dusted it off and plugged it into my new Elac B6 speakers and it sounded really good but again- I wasn't blown away. On a whim I tried the phono stage (running Tape out which taps right off the output stage before the volume and tone controls) and OMG!. This must be one of those hidden treasures but it sounds amazing! It's just rich and full sounding- very British Hi-fi type of warmth, laid back but great detail and most of all I found myself listening to albums for several hours because it was just so much fun to listen to. I would put it up against stand alone pre-s in the sub $1000 category with no problem, honestly, if you have a Rotel of this vintage give it a try. I downloaded the schematic and it's a rather simple feedback circuit running on balanced 19.6 volts with active RIAA (feedback) and using a single Signetics biFET op Amp NE5532AN. For kicks I decided to see how the tuner sounded and again I was pleasantly surprised with a similar quality and musical sounding presentation. The phono stage, however, is special.
pokee1016

Showing 1 response by kijanki

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kijanki
4,446 posts
 
Signetics NE5532 was a one of first op-amps designed for the audio.  It was a little thin sounding until Signetics factory burned down around year 2000 and they stopped making it.  Texas Instruments acquired license, made larger die and produced better (fuller) sounding amp.  Chips from TI have small outline of the state of Texas on the top.

I had them in my Benchmark DAC1.  I replaced them with LME49860, an audio op-amp that Benchmark ended up using in current products.  Sound became a little fuller and more vivid. Still, we're talking about minuscule changes here and even chief engineer of Benchmark John Siau praised NE5532.  Here is his exact quote:

Don't underestimate the NE5532. We have just completed a very comprehensive set of tests on the NE5532 and on various substitutes. We have not found anything that will equal the tranparency provided by the NE5532.

Some have suggested susbstituting OPA2134 op amps in place of the 5532s. This is a bad idea! Our tests show an increase in both 2nd and 3rd harmonic distortion, and the addition of higher order (4th, 5th, 6th, and 7th) harmonics that are virtually absent from a stock DAC1. In addition, IMD will increase, and SNR will degrade.

The NE5532 is power hungry, it has high input bias currents, and high offset voltage, but it can drive high-level low impedance circuits with ease. The 5532 should not be used with low signal levels, and it should only be used in low gain circuits. Also, the offset voltage must be managed with appropriate design techniques. I believe the NE5532 has aquired a bad reputation because it has often been missapplied. The DAC1 is carefully designed specifically for the NE5532 op amp. It may surprise you that the NE5532 was selected for transparency and not on the basis of cost.

John Siau
Director of Engineering
Benchmark Media Systems, Inc.

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