Hi Tommy,
I hate being a PITA but before I buy a amplifiers I really like to know how they work. I use to have TACT 2170s which I used to biamp before mentioned Divas. They were PWM amps that samples at 9 meg I believe the processor went to full digital output and controlled system volume by adjusting the voltage on the power supply rails. This way the system always had maximum resolution. I sold the amps because they could not handle my ESLs
Judging by what I have read so far your amps samples at 2 meg in PWM. What makes them special and why should they be able to handle the load my ESLs present when other PWM amps could not. If you have to protect some proprietary information that is critical that is fine my me if you could try and explain your way around it.
Thank You,
Mike
Mike,
From what I remember, the TACT amps had a 384kHz switching frequency. The modulation is done entirely in the digital domain, and it’s open loop. I developed similar technology nearly 20 years ago for the start-up I was working for at the time and they sold the company, along with my IP, to ST Micro. The level of performance with this method is not so spectacular (100dB SNR is barely reachable). Damping factor is also very low due to the lack of load reactance compensation.
Cherry amps are very different. Switching frequency is much higher with our newer designs (Maraschino, MEGAschino, x-CHerry), but that’s not the most important factor. Our modulation technique is unique, and is proprietary. What I can tell you is that we offer a smooth transition of control that reaches beyond the audio band with our hybrid analog/digital modulation. As far as circuit design, this is the culmination of 30+ years experience with Class-D in many of its forms. Design, simulate, prototype, measure, listen, repeat....
Cherry Amps handle ESLs well because they have great control even at high frequency and low impedance. ESLs tend to be a “heavy load” as frequency rises, so it takes a low impedance amp to drive them without worry of breaking something. On top of being able to drive ESLs with authority, DC coupling enhances bass drive by preventing phase shift down to 0Hz. Cherry Amps have great control over arbitrary waveforms (music) into reactive loads. PCB layout plays a part, as well as power supply design, and proper techniques for signal handling, etc.
The numbers (measurements) don’t tell the whole story! I’ve heard amps with amazing numbers that made certain tracks sound starved for power, or just “dull”. I’m not a big fan of subjective terminology since it’s used sometimes to deceive the consumer with phrases like “opens up the soundstage”. What’s important here is the interaction between the amplifier and the speaker.
-Tommy O
