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Jones Audio PA-M300 Series 2 Solid-State Monoblock Amplifiers Review

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Compared to PASS XA-160.5

For quite a while I had been working with the Pass XA-160.5 Monoblock Amplifiers, a Class A design. As previously indicated, PAM does not have a regulated power supply, while Pass Labs is all about proper regulation of power. Here were two radically different design philosophies in a head to head listening comparison. The XA-160.5 was characterized by me as light and airy, with less dynamic impact than might be expected from an amp weighing 130 pounds. It had a huge amount of headroom, and an accompanying vast soundstage. PAM, on the other hand, was capable of more raw dynamic power and much more impact.

A parable of component selection was about to play itself out. For these comparisons, I ran the Pass monos with the reference-worthy VAC Signature Preamplifier MkII.  I heard something I never dreamed I would, a rather insipid and uninspiring sound quality. I was shocked, as here was the better part of $50K of gear, good gear, sounding languid. What was wrong with the sound? Predominantly, these two as a pair were lacking in weight, density of images, and macrodynamic fortitude. Clearly they were not a match made in heaven.

This is the kind of situation which surprises not just average audiophiles but hardened system builders. The output impedance of the VAC is sufficiently low that it should work quite well with any amp. The input impedance of the XA-160.5 is 30/20kOhms, considering either Balanced or Single Ended connections, so there is no obvious mismatch in terms of ideal output to input of preamp to amp. Yet, the result was uninspiring.

Nevertheless, there was a solution found in the ever-dependable “Digital Toolkit,” the Eastern Electric Minimax DAC Plus with aftermarket discrete Opamps from Burson Audio and DEXA (NewClassD). By rolling discrete Opamps into the DAC I was able to secure a fix, and I do mean a fix. The power of the Opamp rolling is difficult to overstate, as this has not been the first time that a personally unacceptable result has been reversed by swapping them. I was able to mix and match the Burson and DEXA pairings until a goodly amount of the weight and punch of the music had been restored.

I had no such issues when I moved out the Pass amps and moved in the PA-M300 Series 2’s. The Jones amps with the VAC preamp were dominant. The low end impact and presence were visceral and with no loss of detail and ease. The dynamics were solid, so impactful that I determined to roll back in the DEXA discrete Opamps to moderate it. PAM exhibited a crushing grip on the entirety of the frequency spectrum. The nearly elemental power it possesses was such that when I took the system to live listening levels with music having synthesized or electric bass, the ceiling Panels began to vibrate, something which very few amps have been able to elicit. The entire time these amps seemed coasting, entirely effortless as there was no strain, no brittleness in the sound as the level ramped up.

I have a few demo tracks from speaker manufacturers such as Usher, which incorporate Kodo drums. The entire surface of the drum was heard, not just the impact point where the mallet struck. I could actually hear decay as well as a seemingly limitless expansion of the sound wave prior to its hitting the wall of the hall in which the recording took place. Sam Jones puts a lot of emphasis on Slew Rate, which I understand to be a measurement of “recovery time” for an amp. Sam intones that it is among the most important specifications of an amp, “We don’t see why there is not more discussion of slew rate. We believe it is a strong indicator of high frequency smoothness and openness.” I can’t remember the last time I saw a specification of Slew Rate accompanying an amp, including the PA-M300 Series 2.

Perhaps Slew Rate is critically important at Jones Audio, but not important enough to give the consumer the measurements. If Sam wants it to become more of a topic of consideration perhaps is should be included in the amp’s Specs.

PAM has a dual differential input stage, which is said in the company’s discussion of the Design and Features to improve the relationship between the amp and the power supply, lowering high frequency distortion. The improved efficiency of the amp and power supply causes a quicker response time of the amp. A regulated power supply is slower, and thus, according to Sam causes more noise. I did notice a decrease in the noise floor moving from the Pass to the Jones amps. A practical result is that the treble comes off as quite nimble and delicate. There is also a significant decrease in the solid state “etched,” character of the highs, especially cymbals. The delicacy of the treble is exemplary and makes more laid back tube amps sound somewhat indistinct or unrefined in comparison.

I sighed heavily when I read Sam’s conclusions about power cords, “We have not experienced any sonic improvement with other high performance designs, but do not want to discourage customers from experimenting.” I found that PAM is quite reactive to power cables and I urge owners to try several. This may not please Sam; it seems designers of amps think their best designs are somehow impervious to cabling, but actual use shows otherwise. My conclusion is that you use the supplied cords to your detriment. Take the time and spend the money on some good power cables and the amp’s performance will elevate nicely. (Dan Meine, Jones Audio’s Business Manager, confessed that it was he who provided the original comment, not Sam Jones. Dan also offers the following: “There are a myriad of power cables on the market. Some are very good. This is an area where the ideal cable may be different in different installations. The cables that we supply are very high quality conventional cables.  We have not tested other power cables with the goal of making specific recommendations for our amplifiers. Each customer should work with their dealer or consultant to find the best power cable for their unique situation.” – Pub.)

Jones Audio PA-M300 Series 2 Solid-State Monoblock Amplifiers

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