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REVIEW: QSC PL236 Amplifier (SS)

152.163.213.213

I ran across this amp through a customer who works for QSC. It is a compact (22 lbs)"touring amp" designed for sound reinforcement, utilizing a "two step Class H" configuration. Shades of the late, unlamented Soundcraftsmen! It is not exactly a low-bias design and gets quite warm. A fan, which I ordered set for normally off, kicks in at intervals and is not obtrusive. The power supply is the switching type (operating at 115 kHz) which accounts for the low weight. There are numerous storage caps adding up to about 30,000uF, however.

So why am I telling you about this unit, obviously not designed for the audiophile market (inputs are balanced only XLR and 1/4", though a mono 1/4" to RCA permits single-ended operation)? Because it has one specific application you may be interested in: bass.

And I do mean bass. Not the amp you want for fullrange or mid/treble use. The power supply switching frequency infects the output, folds down into the audio range, and makes your face tingle unpleasantly (I heard this effect in my system only; another system was free of it). I had to use a good RF filtering line cord (here Cardas Golden Cross) and a Bybee filter to make the problem go away even in lowbass applications only. But once done, the amp provided detail, definition, extension and dynamic impact which put every other audiophile amp--Class A, AB, C, and D--I have ever tried to shame. Yes that includes big Krells and Levinsons, my Plinius 250/IV, the BBQ, and everything else. Everything else.

For an additional $200 you can buy a plugin electronic crossover (model LF3) which provides a 24dB/oct slope at a selectable plugin frequency between about 40Hz and 500Hz, with level controls, making this very easy for driving subwoofers at the high quality level. Since the builtin amps in most powered subs are of poor quality this amp may make you bypass or take them out. I certainly hope so.

I recently used the amp in our CES booth driving the bass column of big ribbon speakers up to 124Hz, and believe me, I could have had any amp I wanted for that application. This was my choice.

Scoff scoff, you scoff. Okay, don't believe me, I have no connection to QSC, and you'd have to go to a pro audio shop to buy one (the usual discounts are available). There's several smaller models, down to 150W/ch and about $1200 retail, but the big guy (PL 236) is the smoothest and most listenable in the long term. If you've never biamped and your speaker allows it, this is a way to go. The bass quality is absolutely amazing, a new standard for any kind of amplification.

Email me if you try this amp and let me know how you like it. Remember those AC line filters.

Big B

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