Amp/Preamp Asylum

Posted by E-Stat (A) on July 03, 2025 at 14:15:55

My first high fidelity amplifier following a "brown goods" Electrophonic T-600 based system was a 50 watt/channel AR AU Integrated purchased in 1972 when I was 15. It was designed to drive the AR-3a and worked equally well driving my first generation Advents. I especially liked the no nonsense aesthetics down to the pebbly finish on the top cover. Never got into the Japanese receiver thing. Used a Lenco L-75A turntable with Shure V15 and Radio Shack tuner as sources.

While it sounded fine at high output, it had an Achilles Heel that I never thought of at the time - poor low level performance. I took it to a McIntosh amp clinic and Dave O'Brien himself presented me with the distortion chart that demonstrated it worked perfectly to spec at full output. At the pp end of the dynamic spectrum, however, resolution simply disappeared. Kept it for only a year or so. Great lesson learned.

Fast forward to the current garage system using an identically priced (in inflated dollars) Fosi MC-351 sourced either by an RPi3B running piCorePlayer fed by the media server or a repurposed iPhone8 for SiriusXM or Bandcamp. Cute little unit that also contains a decent DAC. Supports USB but only to 96/24 so S/PDIF input mates well with the RPi having an Allo DigiOne board doing the work via BNC cable. Bluetooth works fine for connecting with phones. Like the AR, it sports tone controls but honestly don't have a use for them. Also includes a meter that is somewhat useful for setting initial level control.

Powered by inexpensive commodity devices (two TPA3255 chips and eight NE5532s), it's good for about 80 watts/channel. Sadly it only uses one for main output and another for a sub output. Which is largely useless as there is no crossover. I wish they had simply left out the weak sub feature and bridged the output of each chip for stereo output like found with its big brother, the mono V3. It would also be nice to socket the op amps but then again, it costs less than many cables. I went for the 10 joule 48V power supply vs the base 5 joule 32V model for better dynamic punch.

How does it sound as compared to the AR of yore? Tonal balance is dead neutral including the lower midrange. Far better focus in the midrange and lacks top end harshness. Just forget getting any upper harmonic air. And doesn't suffer at low levels demonstrating good dynamics across the range. By comparison to better, it is decidedly opaque but its sins are largely of omission which I greatly prefer to what you found in the 70s.

Considering the AR amp would cost $1900 in today's world, it offers great value for those who need an inexpensive secondary system. In my confined and hot space in the summer, I sometimes use a whisper fan to keep it from running extremely hot.

Highly recommended within its modest output power.

Edits: 07/03/25