Sherbourn PT-7000 Processor and 7/2100 Amplifier Review

Sherbourn PT-7000 and 7/2100 Introduction

I recall our first introduction to Sherbourn electronics a few years ago was through their very impressive, powerful and value minded five channel 5/1500A power amplifier which was based on a modular mono block design with individual power supplies for each channel.

At that time, we were all living in a 5.1 channel world. However if the computer age has taught us anything it's that progress obsoletes absolutely. Consumers are always demanding to further push the envelope of technology, and manufacturers are always pleased to accommodate them. Thus as a result, the industry norm seems to now be converging on more and more channels in our home theater systems, which one day may eventually surpass those found in state of the art Cineplex's. This may sound funny to you, but lets turn the clocks back 20 years or so and try to envision a day when we would be cramming seven speakers, a subwoofer, and 103" projection screen in our living rooms. Still sound far fetched? For now however, my reference set-up remains in a 5.1 channel configuration, mostly because of limitations in my living room and the WAF (Wife Acceptance Factor) dictates enough is enough!

Separates or a Receiver ?

This has been a long time asked, but often not competently answered, question since manufacturers began producing mega receivers and separates at similar price points. There are inherent advantages and disadvantages to both, so let's do a little soul searching to find the answer to this grueling question.

It is obvious by the latest product offerings from Sherbourn that they understand the current industry trends, and as a result they have managed to intelligently design high performance products that fit quite nicely. Enter the PT-7000 7.1 Channel Preamp/Processor (MSPR: $1500) and the 7/2100 7CH 200wpc Power Amp (MSRP: $2850). This combined duo retails for $4350 and weighs in at a whopping 140lbs! At this price point, your alternative options are flagship receiver such as those from Denon, Pioneer Elite, B&K, etc, or separates from other manufacturers such as Outlaw, Adcom, Rotel, etc. This is an interesting price point to compete in as it is where a threshold is crossed between flagship home theater receivers and entry level separates. The receiver advantage is usually the convenience of an all-in-one box solution, a more sophisticated processor, THX Ultra 2 certification, better remote, and more features, etc, while the receiver disadvantage can sometimes be a less robust amplifier design unable to drive low impedance loads at high volume levels, less flexibility for future upgrading, and less snob appeal that many separates people often enjoy. Before deciding on which option is right for you, you need to ask yourself a few key questions.

• What type of speakers do you plan on using?
• What are your room size and listening level preferences?
• How often are you struck with the upgrade bug?

If your answer to these questions are as follows: "I am using low impedance, low efficient speakers in a reasonably large living room where I love to blast my neighbors while achieving THX reference levels, and often get struck with the upgrade bug when new technologies arrives.", then separates are usually a better choice for your needs. After a few years of usage, you can always dump the processor in favor for the latest and greatest, but can continue to use the monster power amp for all of your loudspeaker and listening needs. With that in mind, lets take an in depth look at the Sherbourn PT-7000 & 7/2100 combo to determine if it fits the bill for today's high performance home theater systems.

Company History (Brief)

Sherbourn was founded in 1998 by Ron Fone and Engne 'Tang'. The partnership is purely synergistic with 'Tang' heading up all aspects of design, engineering, manufacturing and technical support and Fone doing likewise for all commercial functions. 'Tang' was originally involved in engineering design with established audio companies such as NAD and Proton. In 1983, he moved to the USA and joined forces with Acoustic Research, then headed by Fone, to manage the engineering development of an electronics line. 'Tang' formed his own company in 1993, where he primarily designed subwoofer power amplifiers for some of the most well known companies in the industry.

Ron Fone, originally from England, moved to the USA in 1979 and for the next eight years presided over Acoustic Research . His involvement in the industry includes heading up Tera (a high end video company) and McIntosh, where he is credited with taking the famous company from its traditional two channel posture into the exciting world of multi channel home theater. After a period at A/D/S where he again inspired many innovative products, he and 'Tang' began discussing their long cherished dream of starting their own company. In 1998, they founded a small and personable high end audio company that is known to us today as Sherbourn.

Sherbourn PT-7000 and 7/2100 Setup and Listening Tests

Bass Management & Speaker Configuration - The Good and the Bad

On a positive note, the PT-7000 does have selectable crossover settings from 40-150Hz in six steps, and also incorporates Cirrus Logics "Triple Crossover" feature, which after experiencing it, I considered renaming it to "Triple Headache". In theory, the "Triple Crossover" is supposed to allow independent crossover settings for front, center and rear channels. One might wonder what crossover setting the subwoofer gets as a result. Well I was one who wondered and thus I tested this feature using my trusty Avia disc and Radio Shack SPL meter. What I found was the subwoofer crossover setting was dependent on the front main channels setting regardless if the front main channels were set to large or small. As a result, I found that if I had the rears and/or center set to say 160Hz, while the front mains were set to 60Hz, a gap of 100Hz of bass was prominent between the rear/center channels and the subwoofer. Thus the 100Hz gap of bass was not reproduced by any channel. For this reason, I recommend setting all channels crossover settings equal, or at least within 20Hz of each other.

Processing Modes

The PT-7000 is endowed with just about all of the latest surround sound modes, minus DTS 96/24. It even includes including Cirrus Logics "Extra Surround" which is a proprietary algorithm that creates 6.1 or 7.1 output from either matrix encoded or discrete audio signals.

Sherbourn PT-7000 Analog Preamp Evaluation

Sherbourn PT-7000 and 7/2100 Amplifier Overview and Setup

We have to eventually reach a point in home theater where enough is enough! Just how many channels can us home theater enthusiasts support, and more importantly, how many of us have racks or cabinets that can physically support the weight of these mega metal multi channel monster amps (uh oh, tongue twister)? I would venture to say that Sherbourn has approached this limit with their new 7/2100 200 watt/ch x 7 channels, 110lbs heavy power amp. What is interesting about the 7/2100 is it shares the same footprint as their new 5/2100 ($2250) five channel power amp (3u height by 17.7" width). Also, should you decide on a 5/2100, you can always send it back to the dealer to upgrade it to a 7/2100 for an additional $900 or so, when the wife and/or room accommodations allow for a seven channel home theater configuration.

I literally almost ruptured myself hoisting the 7/2100 on my top shelf of my entertainment center and prior to doing so, I had to verify with the manufacturer of my cabinetry to ensure it could handle such weight. (See Staff Reference System 1)

The 7/2100 is a mono block construction, just like its five channel predecessor 5/1500A previously reviewed here, which essentially means each amplifier has a dedicated power transformer and associated supply. Sherbourn feels the advantage of this type of construction is better channel to channel isolation and power reserves since each channel has a dedicated power supply not taxing a common supply like many single supply multi channel amplifiers tend to do. While this can often be true, I have mixed feelings about this, especially since I am an owner of a power amp that shares one huge supply for all three channels. Grant it, my three channel reference power amp has a retail price similar to the Sherbourn so it is really not a fair comparison. However, to prove my point, if budget allows for an amplifier construction to utilize a very large power supply, with separate rectification for each channel, then each individual channel would have the potential for more reserves at any given time, assuming the output devices are robust enough to take advantage of it. This is especially true since in most instances, home theater does not demand nearly full power to all channels simultaneously. However, in reality, when we reach power levels this high, we begin splitting hairs. Given the retail price of the 7/2100 of about $2850, I haven't been able to find a single alternative manufacturer that offers this much power, especially in 4 ohms with all channels driven. In fact only a few other amplifier manufacturers offer similar power capabilities for all seven channels, but at a premium of at least $1000 more money. There are cheaper seven channel alternatives to the 7/2100 with alleged similar power ratings into 8 ohms, but what some of these manufacturers don't tell you is that their solutions are not rated with all channels driven, or they don't specify the total power output into 4 ohms loads.

One point of interest about the 7/2100 is its multi biasing scheme that keeps the amp biased at Class AB for lower power levels and then switches to Class G for high power output to maintain high efficiency and reduce power and heat consumption. Class G operation involves changing the power supply voltage from a lower level to a higher level when larger output swings are required. There have been several ways to do this. The simplest involves a single class AB output stage that is connected to two power supply rails by a diode, or a transistor switch. The design is such that for most musical program material, the output stage is connected to the lower supply voltage, and automatically switches to the higher rails for large signal peaks. Another approach uses two class AB output stages, each connected to a different power supply voltage, with the magnitude of the input signal determining the signal path. Using two biasing schemes improves efficiency enough to allow significantly more power for a given size and weight. I suspect Sherbourn has employed the first method in their design. Employing Class G biasing schemes could arguably not be a preferable option for audiophiles who commonly insist on the linear and usually lower distortion Class A or AB amplifiers, but it never presented a problem in my critical listening tests. In fact, had I not questioned Sherbourn as to why the 7/2100 ran so cool in my rack compared to my reference amps, I would have never known they employed this multi biasing scheme. In any event, the Sherbourn 7/2100 is a true mono block constructed Class AB/G multi channel power amp. Based on their competition, I certainly could agree that their mono block construction does have its advantages.

The Set-Up of the Sherbourn 7/2100

The 7/2100 is by far the heaviest amplifier we ever reviewed, and consequently the most challenging to install into my entertainment center. Placing the 7/2100 on the top shelf of my rack brought me back to the days of standing 225lbs overhead shoulder pressing. It seemed like a good idea at the time, it yielded excellent shoulder growth, but eventually wrecked havoc on my rotator cuffs in the later years to come. My advice here is to place this amplifier as close to the ground as possible, or get one or two people to help you set it up. The 7/2100 comes with all the fixings demonstrating it is truly a high end amplifier meant for the most serious custom installs demanding gut wrenching power reserves. The backpanel consists of single ended and balanced inputs for all channels, a 12V trigger, quality binding posts for the speaker level connections, and the Sherbourn patent pending LDS switch. The LDS feature allows installers to speedily check the correctness of their speaker connections without needing an ohm meter or a walk-through inspection. I found this particularly useful when configuring my system and wished more amplifier companies would offer a similar feature.

The 7/2100 can also be configured in bridged mode to yield a whopping 400 watts/ch for three channels into 8 ohm loads, or 600 watts/ch x 3 channels into 4 ohm loads. However, use this feature with caution, as Sherbourn also states in their manual, when connecting to low impedance speakers. In a bridged configuration, each amplifier see's half the load impedance, thus if you are connecting an 8 ohm speaker for example, each bridged amp would see an equivalent 4 ohm load. Sherbourn explicitly cautions against bridging with speakers less than 8 ohms. I of course didn't listen and attempted to bridge my 4 ohm RBH 1266-LSE towers. When I turned the system on, I was greeted with a psychedelic light show as all the lamps in my living room began dimming due to the 7/2100 short circuit protection circuitry tripping on to protect the amplifiers. I immediately shut the unit off and waited about 10-20 seconds for the lightshow to stop and the DC pulses to stop pounding my speakers while the power supply capacitors discharged. Luckily the 7/2100 and my speakers suffer no damage, but I learned a hard lesson. Later I found out through Sherbourn that they set the impedance threshold on their amplifiers to about 2 ohms, thus the reason why they originally recommended 8 ohm minimum speakers when bridging the amps. I also noted that the manual had a technical error about bridging the 7/2100. It stated for line level connections to use channels 1,3 and 5 for respected speaker level connections of channels 2, 4 and 6, when in fact the line level connections should have been 2,4 and 6 respectively. Sherbourn claims they have corrected this misprint on all new manuals shipping with their current products. I was unable to connect the 12V trigger to the PT-7000 since I only had a cable with plugs that fit the PT-7000 side.

It didn't make sense to me that the PT-7000 employed a headphone type connector for the 12V trigger, but the 7/2100 implemented a bare wire connection 12V trigger mating connection. It didn't really affect my set-up however since the 7/2100 had an auto on detect mode (set to music) that powered the amplifiers immediately after they detected an audio signal. This was another great feature commonly employed on subwoofer amps, but rarely on multi channel power amps. What initially surprised me about the 7/2100 was its usage of dual power cords. However, it made perfect sense considering that under heavy loading, with all channels driven, the 7/2100 could easily consume greater than 15 amps on the primary, thus splitting this current consumption amongst two power cables reduces resistive losses to allow for maximum power transfer when it's needed most. It was obvious to me that the 7/2100 was quite a feature packed amplifier not meant for the typical neophyte looking to set up their first home theater system. The consumer would really benefit from having someone familiar with this type of amplifier to do the install for them, especially since in all likelihood they could have them do the lifting. In fact, I strongly recommend connecting this amplifier and associated audio equipment to a dedicated 20A line to ensure maximum power availability as the 7/2100 could surely deliver if tasked.

In my application I wasn't testing the Sherbourn combo in seven channel configuration, but I didn't want to let those two extra channels simply go to waste. Therefore, I decided to biamp my main speakers since this was something I never did before, mostly because of unavailability of extra amps or shelf space. I realized that I wouldn't be able to achieve the full benefits of biamplification since I had no plans, or means, to physically separate my loudspeakers crossovers and apply active filtering line level to each amplifier.

Sherbourn PT-7000 and 7/2100 Listening Tests and Conclusion

It was clear that some of the benefits of biamping the 7/2100 for my main speakers was realized after a few short listening sessions, especially at extreme volume levels which I don't usually listen at or recommend. The sound emanating from my reference speakers seemed to have a tad more punch and bass impact when comparing biamp configurations verses single amp configurations of the 7/2100. However, the benefits weren't overly dramatic, especially considering how well a single channel of amplification of the 7/2100 drove each speaker in my reference system. In fact, the more I cranked up the volume, the more at home the 7/2100 seemed to be. I felt the sonic merits of the 7/2100 were very close to that of the 5/1500A previously reviewed here, but perhaps subjectively a tad warmer sounding. I also felt the 7/2100 sounded best after a period of warm up of about 30 minutes or so.

I played quite an extensive selection of my CD and SACD collection on the PT-7000 and 7/2100 Sherbourn combo, and never did I find the fidelity lacking. The noise floor was admirably low, the dynamics endless, and the integration seamless. While I would have liked to see some of the previously mentioned bugs worked out of the PT-7000, it never deterred my listening enjoyment from either music or multi channel surround applications. Playing well recorded SACD's from artists such as Patricia Barber and Grover Washington Jr. was a real treat on the Sherbourn combo.

All of the subtle nuances of these recordings that I was familiar with while listening to them on my reference system were well preserved.

Home theater seemed to be the Sherbourn combo forte. Channel separation was excellent. I never heard any bleed over between channel to channel. The panning between channels was about as good as I have heard on past products previously evaluated. It was obvious to me that the PT-7000 and 7/2100 mated well together both sonically and functionally.

Conclusion

The Sherbourn PT-7000 and 7/2100 are quality products that will deliver very satisfying performance for large, upscale, home theater installs that demand high power output capable of achieving almost limitless SPL levels. These products however are not for everyone. Great care must be considered in their handling and set up, especially the 7/2100, and should be done by experienced home theater enthusiasts or professional custom installers. If your home theater needs coincide with high power demand, easy configurability and usability, and overall excellent performance, than the Sherbourn PT-7000 and 7/2100 combo should be on your shopping list as a viable alternative to mega receivers and other entry level separates alternatives.

The Score Card

The scoring below is based on each piece of equipment doing the duty it is designed for. The numbers are weighed heavily with respect to the individual cost of each unit, thus giving a rating roughly equal to:

Performance × Price Factor/Value = Rating

Audioholics.com note: The ratings indicated below are based on subjective listening and objective testing of the product in question. The rating scale is based on performance/value ratio. If you notice better performing products in future reviews that have lower numbers in certain areas, be aware that the value factor is most likely the culprit. Other Audioholics reviewers may rate products solely based on performance, and each reviewer has his/her own system for ratings.

Audioholics Rating Scale

• — Excellent
• — Very Good
• — Good
• — Fair
• — Poor

Metric	Rating
Multi-channel Audio Performance
Two-channel Audio Performance
Video Processing
Bass Management
Build Quality
Fit and Finish
Ergonomics & Usability
Ease of Setup
Features
Remote Control
Performance
Value