Had to look that up, never heard of it. Don't think it was ever imported here.
Designed by Tomlinson Holman, the inventor of 5.1 and all later surround formats, the Chief Engineer on the ADVENT 300 Receiver. You should Wiki him, a very interesting history in both audio & cinema audio, a former Microsoft employee, a former Professor and more.
My pair have these upgrades:
(By Peter Williams of Quirk Audio [and a former Abbey Road Recording engineer,
Australian sound engineer, worked on the London production of the stage show Evita and subsequently at numerous London studios from 1979 through to 1986.
Went on to found an equipment supply and renovation company, Quirk Audio, in Silicon Valley, CA, USA.]):
APT made both pre-amps and power amps designed by Tom Holman (of THX fame). They are both interesting from the perspective of their design and sound quality.
I have undertaken upgrades on a number of APT pre-amps, and use one in my reference “Lab” system. They have a great phono stage and are both warm and detailed. The pre amp was designed around a number of op amp IC’s, originally the TL072, with each op amp forming a “block” of functionality in the pre-amp. As with many components of this vintage, they do benefit from replacing the electrolytic capacitors and other components. My upgrades include:
- New power supply capacitors of higher capacity
- replacement of all electrolytic capacitors with new audio quality Nichicon (including bipolar and additional capacitance at appropriate circuit points) and Wima film types.
- New IC’s through out all in sockets (including the regulator IC’s)
- New higher capacity bridge rectifier
- Replacement of the relay
all of which greatly enhances the sonic performance and reduces noise and distortion significantly.
I have supplied a number of these, often used with the upgraded NAD 2200’s described elsewhere, which has results in great sounding combination.

The front and rear panels of the APT preamp


The renowned phono section showing the capacitive and resistive termination options for MM cartridges. The infrasonic filter switch is also visible
Amirm review of one of mine:
https://audiosciencereview.com/forum/index.php?threads/apt-holman-preamplifier-review-
Ken Rockwell's review of an unmodified one:
https://www.kenrockwell.com/audio/apt/holman-preamplifier.htm
I also use the afore mentioned NAD 2200's (also resto-modded by Peter [this is a combination of equipment that I have been using for 40 years, so before I ever heard about Peter around 10 years ago])
One of my 2200's tested by Amirm:
https://audiosciencereview.com/forum/index.php?threads/nad-2200-vintage-amplifier-rev