Accuphase AC-2

Accuphase AC-2 MC Cartridge Review & Repair

Take a look at this beautiful Accuphase AC-2 moving coil cartridge. It belongs to a customer, has a broken cantilever and will soon be repaired.

The Accuphase AC-2 is a high-performance moving coil cartridge from 1980, utilising a tubular sapphire cantilever and line-contact diamond. Jewelled cantilevers like those made from ruby, sapphire and diamond are fabulously stiff.

UPDATE! She has now been repaired, read through to the bottom for details.

Accuphase AC-2
Ah yes, all cartridges should have a sapphire tube cantilever…
Accuphase AC- 2 moving coil cartridge
The Accuphase AC-2, with original box and stylus guard.

….BUUUUT stiff in engineering terms also means brittle. Like glass, jewelled cantilevers break easily when excessive bending forces are applied to them. 

Broken cantilevers are common, jewelled ones especially, often as a result of mistaken attempts at cleaning. Sadly, someone broke this AC-2 cantilever but the good news is that this type of damage can be repaired.

Accuphase AC- 2 moving coil cartridge
OUCH! This is where the beautiful line contact diamond would normally be glued. It has broken away along with part of the sapphire cantilever.

There are several experts in the field of cartridge repair. This AC-2 is being retipped by Soundsmith in the USA, one of the best. They are fitting new sapphire cantilever and line contact stylus, as per original Accuphase spec and my recommendation.

I also use Garrott Brothers here in Australia. They did a great job retipping my Fidelity Research MC-202 for example, and an FR-1 for a customer of mine.

MC-202
My Re-tipped Fidelity Research MC-202, work expertly done by Garrott Bros, Australia.

Accuphase AC-2 Specifications

As always, courtesy of Vinyl Engine.

  • Generating element: moving coil
  • Output voltage: 0.18mV
  • Frequency response: 20 Hz to 60 kHz
  • Channel separation: 30dB
  • Channel balance: 0.5dB
  • Internal impedance: 4 ohms
  • Load impedance: higher than 50 ohms
  • Vertical tracking angle: 20 degrees
  • Compliance: 15 x 10*6 dyne/cm
  • Stylus type: line contact diamond
  • Tracking force range: 1.5 to 2.5g
  • Recommended tracking force: 2.0g
  • Weight: 9.5g
Accuphase AC- 2 moving coil cartridge
My customer Tim acquired this Accuphase AC-2 with all original accessories and packaging, dramatically adding to its value and collectibility.

It goes without saying that 0.5dB channel matching and 30dB separation are extraordinary specifications. If you look at the supplied frequency response graph for this AC-2, you’ll see it’s almost ruler-flat from 20Hz to 20kHz. Who says analog equipment is coloured..?! Oh, that’s right, people who forget that microphones are also transducers and capture all the music we love!

Accuphase AC-2
Yep, that’s a frequency response flat to within around 1dB from 20 Hz to 20kHz. That’s a serious transducer.
Accuphase AC-2
Crazy good specs, but this is expected from Accuphase.
Accuphase AC-2
The measured output of 0.23mV is slightly higher than the 0.18mV spec. Marketing materials are often drawn up earlier and design changes and measured specs may vary from those originally conceived.

Features and Compatibility

The most critical features of the AC-2 are that tubular sapphire cantilever, samarium cobalt magnet assembly, die-cast body and line contact diamond.

Various design elements come together to make a cartridge sound clean, agile, fast, airy and so on and the AC-2 is imbued with these desirable sonic attributes. A stiff, low-mass cantilever plays a big part, as does that lovely, line contact gem. 

Accuphase AC-2
From left to right we have the best to most basic stylus profiles. The MicroLine type digs the most detail out of the groove and has the advantage of playing a section of the groove that is essentially virgin if the record has only been previously played with cheaper spherical or elliptical types. MircoLine and linear contact types have a flat contact surface contact with the groove wall. With elliptical and spherical types, this is a curved surface. MicroLine and linear contact types are also lower in mass, improving the resolution of fine detail.

Electrically, the low 0.18mV output and 4 ohm impedance mean it will match up well with most low to medium impedance step-up transformers. The measured output seems to be somewhat higher too, which helps.

A transformer is certainly the best way to extract the most out of a cartridge like the AC-2. An active MC preamp will need lots of gain and in my experience, is unlikely to have the air, speed or low noise of a transformer. If using an active MC preamp, I’d suggest 40 – 50 ohms loading as a starting point. Less will likely crush the life out of it.

Mechanically, the AC-2 is a medium compliance, medium tracking force design that will work well on low to medium mass tonearms. It will match everything from the lighter, lower mass arms from the late ’70s through to medium mass arms common now. Be careful with high mass arms. The resonant frequency is likely to be low and this can be very bad with a jewelled cantilever and heavy bass!

Damage

Have a look at these close-ups of the damaged AC-2 cantilever.

Accuphase AC-2
Check out the fractured edge of the tubular sapphire cantilever. This type of fracture is characteristic of brittle materials, they tend to shatter when torsional forces exceed design strength.
Accuphase AC-2
Nasty
Accuphase AC-2
We’re running out of resolution here, but you get the idea.
Accuphase AC-2
Another angle. I’ll post updated images of the repaired Accuphase AC-2 soon.

Repair

We finally got the cartridge back and I have to say its a very nice job indeed. The new sapphire cantilever and line contact diamond look perfect under the loupe and you’ll see everything is nice and straight.

Accuphase AC-2
I think you’ll agree, this is a very good repair job exhibiting an almost perfectly straight cantilever and diamond set pointing directly out of the cartridge.
Accuphase AC-2
Excellent alignment accuracy can be seen here

Accuphase AC-2

Accuphase AC-2
A very nice job and the proof, of course, will be in the listening, more on that soon!

6 thoughts on “Accuphase AC-2 MC Cartridge Review & Repair”

  1. I’ve always found it fascinating how on earth someone can make such a tiny tiny diamond stylus. About 2014 I researched how it’s done but still not sure .id like to be a fly on the wall at Shelter

  2. Look forward to seeing the repair
    The photos were excellent and made the story come alive
    Cant wait for the next chapter

Feel free to leave a comment!