“Let our rigorous testing and reviews be your guidelines to A/V equipment – not marketing slogans”
Facebook Youtube Twitter instagram pinterest

Classe CT-2300 Two-Channel Amplifier Design Overview

By

Classe electronics are designed and engineered in Canada and built at a state of the art facility in China. They offer two versions of this amplifier, the rack mountable CT-2300 (MSRP: $6,500) and the stand alone CA-2300 (MSRP: $7,000) Delta series. Both amps share identical internal components only the Delta version offers spruced up cosmetics since it’s meant to be out in the open as a showpiece instead of rack mounted and out of sight like the CT series. The $500 difference in cost between the two units reflects Classe’s extra manufacturing cost for the fancier housing. The CT-2300 was sent to me because it’s more readily available, but had I been on the market to buy this amp, I’d have opted for the CA-2300. In my opinion, it’s well worth it if you’re thinking about showcasing this amp out in the open. It just looks awesome.

CT-Tunnel_C_LG.jpg     CA2300-InsideShot-RGB.jpg

 Classe CT-2300 (left pic); CA-2300 (right pic)

The Classe design goal for their Delta/CT series was to produce an amplifier module that would be as simple and compact as possible. Signal paths were kept as short as possible to preserve fidelity. Their 6 layer PCB board ensures this, and Classe claims these are their finest sounding and performing amplifiers they’ve built to date.

The CT-2300 employs a class AB amplifier topology with 18 bipolar devices per channel and 67,200 uF of capacitance (12 x 5,600uF) per channel. Ganging up multiple smaller caps is a great way of not only saving space but also lowering ESR (Effective Series Resistance) since each capacitor in parallel halves resistance while doubling in capacitance value assuming the same values are used throughout. The power capacitors are rated at 100V / 85 deg C. The voltage rating is plenty big to meet the 300 watt continuous rating (and 87.5V DC rail voltage), but I was a bit surprised Classe didn’t employ 105 deg C parts. 85 deg C is pretty much industry standard, but some companies go that extra mile and use higher temperature parts for increased longevity. As an EE myself that loves to overdesign stuff, I appreciate those little details. The amplifier topology is differential through the entire circuit path all the way to the final current stage. The power transformer is a torodial type rated at 2356VA which is nice and meaty. I have no doubt based on the sum of the parts thus far that this amplifier has a pair of cojones.

Classe talks about the CT-2300 requiring a break in period of up to 300 hours for the capacitors to fully form to provide the best audio quality. While there is some merit to this, I often feel manufacturers exaggerate the break in periods as a talking point for salespeople to convince their unwary customers debating on returning the product that performance will get even better over time. Take it with a grain of salt. Break in is real for bass drivers and to some extent capacitors. If someone tells you speaker cables break in too, suggest to them a healthy dose of Audioholics rehab and send them to our Cable University section of the site. Thermal equilibrium is however a different matter and Classe recommends a warm up period of 10-15 minutes before conducting critical listening. I do this with pretty much all amplifiers I listen to and also let them run 30 minutes loaded at 1 watt prior to engaging bench tests.

Classe has designed the CT-2300 amplifier to be safe from various fault conditions such as output overload, DC offset and the AC mains operating out of their nominal range (for 120V models that +15% to +10%). I find it commendable that the fine folks at Classe put forth so much effort to engineer proper protection into this amplifier. I was a bit surprised that the CT-2300 wasn’t switchable between 120/220V operation. I’ve reviewed much less expensive amplifiers that not only were switchable, but were also auto-detectable switchable.

A unique feature of this amp is how Classe chose to keep it running cool. Their proprietary method is what they refer to as ICTunnel. Their ICTunnel system is said to operate like the human hypothalamus which regulates body temperature. The ICTunnel utilizes an aluminum bonded-fin heatsink. It exploits the principle of low thermal mass, so it heats quickly but can also be cooled quickly. Inside its relatively small sized chassis are heatsink fins providing nearly 31 square feet of surface area. The fins are closely spaced to each other to maximize the surface area inside the tunnel, but not so close as to heat each other up. In conjunction with the critical spacing of the fins, a low noise fan along with pressure and temperature sensors maintain the amplifier's target temperature.

ICTunnel allows the amplifier to reach thermal stability within 15 minutes from power up. Once thermal stability has been reached, the heat sensors and the fan will keep the operating temperature stable regardless of how long the amp will be used (hours, weeks, months). The amp will also run cooler than a conventional amplifier using heat sinks which is a very important factor for both sound quality and long term reliability. The front face plate protruding nature is a result of the shape of the air intake that has been designed to allow air to circulate freely in the IC Tunnel while keeping turbulences and the resulting noise low. I even measured the idle power consumption when plugging this amp into my ACP S20 power conditioner and it was well under 100 watts. This is a lot of cool (no pun intended) tech for an amplifier and it works per my testing.

The CT-2300 includes adjustable rack rails to accommodate racks of different depth. I didn’t use them in my Middle Atlantic Rack since I already had a shelf in place. But, for those wishing to install the amp into their racks with the included rails, simply loosen the screws, extend the rails to the desired depth, fix to the front and back of the rack, and then re-tighten the screws. The user manual gives clear instructions and illustrations on how to do this and most consumers purchasing this amp will likely have a professional installer (recommended) do it for them anyways.

CA2300-BackPanel-RGB.jpg

Classe CT-2300 / CA-2300 Back View

A good portion of back panel real estate of the CT-2300 is dedicated to fan exhaust for the ICTunnel system. The CT-2300 has quite a lot of connection points for a two-channel amplifier. That’s because it sports CAN-Bus controls to interface to other Classe products, USB & RS232 for firmware updates and to interface with Crestron/AMX devices, 3.5mm +5V trigger inputs/outputs, two sets of WBT 5-way speaker binding posts for bi-wiring, balanced and unbalanced input line level connections and a 3 prong power receptacle with a supplied 2 meter 14awg 3 prong power cord. The balanced input pin assignments are in compliance with AES14-1992 where pin 1 is Signal ground, pin 2 is Signal+(non-inverting) and pin 3 is Signal- (inverting). Make sure to check the polarity of your mating preamp when making your connections. I have found some gear flips pins 2/3 which would essentially flip the phase of the signal between the preamp and power amp.

CAN-Bus will allow a Delta or CT series Preamp/Processor touchscreen to:

  • Display status information for every connected unit, including amplifiers which do not have a touchscreen display.

  • Create a “PlayLink” that allows an SSP or Preamp to automatically switch to the correct input when a Delta series source component starts playback.

  • Adjust the global system brightness.

  • Configure the entire system to go in and out of standby at the touch of a button and also bring individual components in and out of standby.

  • Mute any connected unit


CT-2300_B_LG.jpg      CLASSE_CA_2300.jpg

Classe CT-2300 (left pic) & CA-2300 (right pic) Front Panel View

The Classe CT-2300 won’t win any beauty prizes but the CA-2300 probably could. Both units are exceptionally crafted as expected for products of this price class. The only front panel user interface is the front panel illuminated button which serves as a status indicator and on/off switch.

  • On (dim red) = standby

  • Flashing blue (on power-up) = initialization

  • On(blue) = operating normally

  • Flashing (after power-up) = AC mains voltage out of range

  • Flashing (alternating red/blue) = the air intake filter needs to be cleaned

  • Slow flashing (red) = protection circuit(s) engaged

Set-Up

ShowcaseUnboxing the CT-2300 was a bit unusual. The entire box literally collapses as you open it to take the amp out. The thick cardboard and ample framed foam inserts demonstrates that Classe has put a lot of effort in ensuring this amp shows up at the customer’s home damage free. The 90lbs CT-2300 was as brute to haul up the flight of steps for testing in the Audioholics Showcase Theater room. I connected the CT-2300 to my Denon AVP-A1HDCI A/V processor via Bluejeans Cable balanced interconnects and Kimber 8PR speaker cables with compression WBT banana plugs to the new Status Acoustics 8T speaker system I currently have under review. The source devices included the Oppo BDP-95 and Yamaha MXC-2000 MusicCAST system. The listening space is a 6,000 ft ft^3 room that is moderately acoustically treated, courtesy of Auralex Acoustics.

I spent most of the time evaluating the CT-2300 using two-channel music sources but I also tortured it by running my reference speakers as Large with all of the LFE/Sub info directed to them when engaging multi-channel sources. This is something I NEVER recommend unless: your speakers are up to the task (most aren’t) and your amplifier has enough power reserves to handle the strain. We did some brief comparative listening tests between my reference Denon POA-A1HDCI amplifier, an Axiom Class D amplifier, and a Pass Labs X350.5 that I currently have in for review.

The CT-2300 front panel power switch blinks blue for a few seconds while the fan kicks on and a series of internal clicks can be heard with a very slight pop sound from the speakers once the amp circuits are engaged. The fan then powers down never to be heard again in most circumstances unless you’re sitting right on top of the amp in a separate room from your speakers. Seriously, I’m not a big fan (no pun intended) of using forced air cooling in amplifiers. But, the Classe ICTunnel system is so well executed that it rarely turned on unless I was beating the snot out of the amp. At those listening levels, it was impossible for me to hear fan noise. Don’t sweat the fan, it’s a good thing that keeps the amp running cool and allowed Classe to reduce the product weight by not having to build in more heat sink area to cool the beast.

 

Confused about what AV Gear to buy or how to set it up? Join our Exclusive Audioholics E-Book Membership Program!

Recent Forum Posts:

AcuDefTechGuy posts on March 13, 2014 10:27
RichB, post: 1022651
any votes for an ATI Signature Series.

- Rich

I assumed that ATI was the better value, but perhaps I may be wrong. Parasound Halo might be the better value. I will have to look into that.

I mean if you could get the Parasound Halo A21 250WPC amp brand new for a few hundred dollars less than the ATI AT2002 200WPC amp, I don't know if I can recommend the ATI.
RichB posts on March 12, 2014 21:09
PENG, post: 1022880
I feel the same way in that regard. For me, when I say amps sound the same I always meant mid range to high end class A, A/AB and AB amps in perfect condition and operating within their specified limits with adequate headrooms. I would not expect an Outlaw monblock m2200 or an Emo upa-200 sound the same as any classe monoblocks. They may, but I just would not expect them to and would not believe it, not until I have heard them side by side in a blind test.

I am on the same page. I never don't worry about was about small levels of distortion.

I suspect some amps produce less harmonics played at low levels and that may matter if you have a system/room capable of resolving them.

Some amps may handle complex loud better than others.
Dynamic content can have greater demands than you can account for.
It is not easy to determine how much power is needed for a given system and I suspect we are pretty tolerant to clipping.

Well made A/B amps are more alike the different.
There are certainly better places to put money than some of these rarified amps.

- Rich
PENG posts on March 12, 2014 21:03
RichB, post: 1022876
I know why.

I guess I will never experience that final bit of control, heft, and air.

I think sometimes it is unclear that if we are discussing $400 receivers versus ATI 3000's or
Pass Labs and Parasound.

- Rich

Of course, I totally forgot the heft and air lol!!
PENG posts on March 12, 2014 21:02
RichB, post: 1022876
I know why.

I guess I will never experience that final bit of control, heft, and air.

I think sometimes it is unclear that if we are discussing $400 receivers versus ATI 3000's or
Pass Labs and Parasound.

- Rich

I feel the same way in that regard. For me, when I say amps sound the same I always meant mid range to high end class A, A/AB and AB amps in perfect condition and operating within their specified limits with adequate headrooms. I would not expect an Outlaw monblock m2200 or an Emo upa-200 sound the same as any classe monoblocks. They may, but I just would not expect them to and would not believe it, not until I have heard them side by side in a blind test.
RichB posts on March 12, 2014 20:53
PENG, post: 1022875
They all distort but differently in many forms. My point is, when blindfold most people couldn't tell those distortions (0.05, 0.001, or 0.0001% of any distortions) apart.

How many times have you read a professional review that claims a $2000 amp such as the A21 that sounds as good or better than a $100,000 Boulder, Goldmund, or even the lower high end in the $10,000 range from McIntosh, Krell, Conrad Johnson, Pass Lab etc.? I have never come across one. Invariable they would praise the entry level high end A21 or Bryston SST2 to the nth degree and then would add something like, that is not to say it is as good as the $10,000………….., for example the $10,000 xyz amp just give you that extra bit of warmth, and that final touch of details in the highs, blablabla etc etc… Ever wonder why?

Yep I'm having fun too, fun is good.

I know why.

I guess I will never experience that final bit of control, heft, and air.

I think sometimes it is unclear that if we are discussing $400 receivers versus ATI 3000's or
Pass Labs and Parasound.

- Rich
Post Reply