Setup and Operation and Listening Tests
The Thule PA350B is a rather unique amplifier in the sense that it is the first I've run across with 3 power switches! That's no typo, there is a Mains power switch located on the back of the chassis, a Fault switch located below the unit, and a Stand By front panel power switch. I can appreciate the manufacturer's passion for safety, but I found the bottom chassis fault switch to be more of a nuisance than a benefit, especially after I loaded the unit in my Middle Atlantic Rack and found out the hard way it wouldn't power up because I accidentally disengaged power to the fault switch when installing the 48lb amp at the top of my rack.
According to the manual, the PA350B requires an unusually long 2-4 hours to warm up and reach peek performance if cold started from the mains power switch, but only requires 10-15 minutes of warm up time if the unit is left in standby mode and then becomes active. While I can understand the benefits of allowing an amplifier to reach thermal equilibrium, I am uncertain as to why it would take as many hours as the manufacturer claims from a cold start. Nonetheless, I left the amp on for several hours before engaging in any critical listening tests or undergoing my power measurements.
The PA350B can be triggered to toggle between 2CH and 5CH mode in three ways:
- Auto sense mode - if it detects signal on center channel it automatically switches to 5/7 CH mode
- Manually on front knob by pressing the 2CH/5CH button
- Their proprietary data port which interfaces with their matching preamplifier
One operational quark that irked me regarding the bridged 2CH mode is that the unit automatically reverted back to balanced inputs each time it was power cycled. Since I wasn't using their matching preamp to provide it data logic, I had to use some nifty Impact Acoustics unbalanced to balanced cables between the preamp of my Denon AVR-5805 receiver to this unit to always ensure I had audio signal present.
The PA350B sports all high quality WBT style banana speaker terminals and gold plated RCA jacks with two balanced inputs for the high power 2CH bridged mode. It has no 12V trigger options (a disappointment to me) though the unit can be trigged via the proprietary data port connection if you are using their matching preamp. The S1 & S2 connections are intended for upgrading this unit to 7 channels of amplification.
Subjective Listening Tests
I spent most of my time listening to the PA350B is 2CH bridged mode connected to the top portion of my new RBH Sound T30-LSE system. This is a special anniversary edition of the T2P System fitted with Status Acoustics driver upgrades and enhanced high excursion dual 10" subwoofers. There are also other upgrades in the crossovers and increased box volume for the bass drivers. Audio nirvana has been reached, but pairing these babies with quality amplification is a must. I used the Thule PA350B and some new, soon to be released, 1U high subwoofer amplifiers from Earthquake to power the bass modules.
When switching between 5CH mode and 2CH bridged mode, the latter seemed much more dynamic, and lively. The 5CH mode of this amp simply didn't have enough oomph to drive my 4 ohm speakers to reference levels in my nearly 6,000 ft^3 Auralex-treated Audioholics Showcase Room . While the PA350B didn't sound bad in 5CH mode, it simply didn't have the heavyweight feeling it took on once it was switched over to 2CH bridged mode. If there were ever a case of Dr. Jekyll & Mr. Hyde in amplifiers, this was it! In 5CH mode the PA350B was a mild mannered amplifier much like those found in very good mid-priced receivers. A quick switch over to 2CH bridged mode revealed the true dynamic nature of the beast while at the same time proving muscle could be matched with finesse with its dead silent noise floor and very open and natural sound. The PA350B loved to be cranked and had all of the dynamics and clarity needed to power my new reference speakers to SPL levels beyond that of what most mere mortals (including myself) could bear to listen too.
I didn't want to baby this amp, so I threw the most dynamic material in my collection at it from the likes of Patricia Barber, Diana Krall, Jaco Pastorius and Pat Metheny. The Pat Metheny & John Scofield - I Can See Your House From Here to this day remains one of my favorite CDs to listen to for critical 2CH audio evaluations. This disc quickly reveals the dynamic nature of a hifi system from amplifier stage all the way to the speakers. Wimpy amps will clip or sound stringent during drum solos and cymbal crashes. This was not the case with the Thule PA350B amplifier when bridged in 2CH mode. It was able to convey all of the dynamic nature of Track #4 "Everybody's Party" with ease. The cymbal crashes were liquid and transparent while the brush strokes retained their airy sonic signature I was familiar with when evaluating this CD on other excellent components that have graced my reference system in the past.
I have recently become acquainted with the late and great Jaco Pastorius who is quickly becoming one of my favorite bass players... yes I am a sucker for fretless bass. My neighbor brought over a multichannel SACD from him, not knowing what he had in his possession; we popped it in for a listen. It became readily apparent we had reference multi-channel material on our hands. This is perhaps one of the best sounding multi-channel recordings I've heard to date. The Thule PA350B seemed to love this SACD as well as it belted out plenty of clean and dynamic sound throughout the entire listening session.
kinda JAZZY kinda FUNKY from HighNote Records is a groovy compilation of jazz that you just don't get on the radio, and rarely have the opportunity to hear live (at least in my neck of the woods). The jazz organ was reproduced with amazing clarity and fluidity on track #7 "Peach Cobbler" by Bill Heid. The trumpet solos were so vibrant and real, I felt like I was at the Old Jazz Cellar I used to visit in Ybor City back in my college days. All I was missing in this listening session was a pint of my favorite brew.
For fun, I decided to run my RBH T30-LSE system entirely off the Thule PA350B in 2CH bridged mode, thus bypassing the Earthquake amps that were powering the subwoofer portions of my speakers. I couldn't think of a better torture test than using the Dianne Reeves Never too Far CD I had on hand.
Dianne Reeves Track#1 "Hello (Haven't Seen You Before)" bass line is quick and sustained. It tests transient response of speaker system. With the Thule PA350B running my main speakers full range, the bass was incredibly tight and well pronounced, despite the fact I shut off my additional 2 subwoofers which were strategically placed in the room to provide more uniform bass in the listening area. I was a little unsure at first if the PA350B would be up for running my speakers full range since the internal subwoofers in the system don't have a crossover network. They were designed to roll off based on the natural acoustical slopes of the drivers. As a result, they have stellar transient response but also represent a difficult load to wimpy amps since they are highly inductive. The PA350B had no qualms about accepting this challenge and effortlessly drove my speakers with ample and well-controlled bass and nuclear highs. It revealed its "Hyde" character when called upon to do so.
In track #2, "Never too Far", the chorus sounded like it emanated from the side channels. If I hadn't confirmed my processor was set to 2CH, I'd think I was listening in PLIIx Music Mode. The stereo separation was excellent and I was rewarded with a naturally LARGE soundstage just like I would expect from any well engineering amplifier.
Track #3 "Come In" literally shook the floor of my 6,000 ft^3 reference room. Plenty of power taxing bass was present while at the same time excellent vocal clarity and non sibilant highs were consistently reproduced.
Switching this amp to 5CH mode simply revealed the Dr. Jekyll side of this amplifier. The amp simply couldn't keep up with the demand of my speakers. The bass was no longer as punchy and the transients weren't nearly as dynamic. I also noticed the noise floor was audibly higher and the amp simply didn't sound as refined or effortless. For small satellite speaker systems this will likely be of no consequence, but for those budding audiophiles who require raw power for their monster-sized speaker systems, 2CH bridged mode with this product is your only logical recourse.
The Thule PA350B multi-channel amplifier left me with mixed recommendations. As a 2CH bridged amplifier, it is a very fine amplifier. Its performance and sound quality is excellent, and its cool running compact chassis is appealing for those with limited rack space and the lack of desire to lug a 100lb amp up a flight of steps to get to their theater room.
However, as a 5CH amp, it falls short of its published power specifications though still performing above average. It didn't have quite enough juice to power my reference system in the large sized room I was using it in, but may be sufficient for smaller scale installations where the user is running a bass managed satellite speaker system with multiple subs.
Thule employed a fully complimentary circuit topology from input all the way to the speaker outputs. This is very rare in the audio industry as it greatly increases component costs and circuit complexity. However, it pays dividends in achieving exemplary low distortion figures. As you can see in my test results, the Thule amp produced some of the lowest distortion figures we've seen to date regardless of price or proclaimed power. My hats off to them for designing a truly fully balanced amplifier - the only way to do it in telecom industry in order to accurately pass distortion free data over long distances. Their efforts in this capacity certainly paid off in the amplifier's sonic signature which to me seemed very laid back, natural and unstressed in 2CH bridged mode.
Considering its asking price of $4k, it's not the bargain basement of amplifier brands you may be accustomed to when dealing with many of the online manufacturers. As is the case with most European products, while you may have to pay through the nose to get these products you are sure to find a compact design that can competently serve your 2CH and multi-channel needs. If this describes you, then you should take this baby out for a test drive.