Loading for Air Tight PC-1 Supreme

Atmasphere:now I finaly understand this subject. Thank you.

If the preamp comes set up with a stepup transformer, about the only means available is to load the secondary of the SUT. If set up right, the load will load the cartridge and the transformer for optimal results.

IME things are rarely 'set up right'. So its a good idea to load the cartridge at critical damping, and then load the transformer for critical damping too. This can be a bit tricky, but any technician with a square wave generator and a 'scope can do it.

You can also do it by ear, but the values you arrive at will be more approximate (this happens to be one of those nice cases where the test equipment and ears agree, BTW). FWIW, the correct load for the cartridge will be the same for a transistor preamp as it will for tubes, assuming that both otherwise have the standard 47K input.

Dear Ianchang: The Dougdeacon advise to contact the manufacturers is a good one, here for Artemis: http://www.artemislabs.com/artemis-labs-contact-information.html

as a fact the Artemis comes ready to accept resistors on the step-up secondary.

Here you can contact Air Tight: Phone/Fax 072-678-0064.

I hope that you can have the right advise/support for them.

Regards and enjoy the music.
Raul.

Ianchang, The data that came with the PC-1 no doubt refer to the final load the cartridge "sees" when it looks at the phono stage input. With no SUT, all you need to do is insert a resistor in that range of values in parallel with the input of the phono stage. With a SUT, as Doug says, it's a bit more complex, because the cartridge "sees" first the SUT and then the load resistor on the other side. The intervention of the SUT will affect the load impedance by a factor related to the square of the turns ratio of the SUT. This sounds arcane, but it's really no big deal to calculate the value of a load resistor that will at least be in the ballpark. After that, again as Doug says, you may want to fiddle with the value to get optimal results, OR you may be perfectly happy. For formulae on how to calculate the load resistor, go to the Jensen transformer website or Google the question. You do have to know the turns ratio of your particular SUT, however. All of the foregoing applies to the choice of putting the load resistor on the phono preamp side or the secondary of the SUT, with the cartridge connected to the primary. I myself am not familiar with placing a load resistor between the cartridge and the SUT, and you can ignore that for the moment, just to get started. It just would change the value of the impedance reflected across the SUT. (Output R of the cartridge in parallel with the load R all on the primary side.)

With the PL-1 I seem to be only able to set the impedance based on the loading impedance and not internal impedance. From the leaflet that came with my PC-1 Supreme cartridgem, airtight seems to suggest a loading of 100ohm to 800ohm and preferrably 400ohm. But that leaflet is met for the PC-1 i believe. I wonder if the loading for the PC-1 Supreme is the same as PC-1

With a low output moving coil cartridge (LOMC) you always have to set impedance based on the internal impedance of the cartridge - no matter what kind of phono stage you have.

An active gain stage just makes calculating a reasonable value simpler.

pardon my ignorance. Does it mean that once a Phono stage utilise a step up transformer, I will have to set the loading based on the internet impedence of the cartridge?

Both your phono stages have internal stepup transformers, so Rushton's setting (based on his active phono stage) will not apply.

Loading of LOMC's with stepup transformers is both more critical and more complex than with active stages. The optimal load depends on the turns ratio of the transformer, and small adjustments can make large sonic changes.

I'd suggest checking with your phono stage manufacturers or dealers for guidance (though in my experience many offer less help than they should). Let them know the internal impedance of your cartridge (2.5 ohms) and they should be able to give you a starting place.

BTW, the brochure claims the Artemis ATE-2001's MC inputs are switchable to 3 ohms or 20 ohms. It's only the MM input that's fixed at 47K. Use the MC inputs and try both settings, just to give yourself some reference points.

With any stepup, you also have to decide whether to use primary or secondary side loading, another complex issue which was discussed on on a recent thread here. Look that thread up for an overview from someone who understands this difficult topic. I fine tuned LOMC's through stepups for several years with success, but it always took considerable experimentation to fine tune results and if I took the same cartridge and SUT to another system the optimal load was never the same.

If I'm making it sounds like there's no simple answer, it's because there's no simple answer. Loading with active gain stages is much easier.

The 47K will not work in my opinion. Tonal balance and distortion of the Air Tight is drastically changed with load.

I hv tube phonostage both the Artemis PL-1 and Air Tight Reference ATE-2001. The ATE-2001 has a fixed loading of 47k only.

It somewhat depends on the phono stage.

With my Aesthetix Io the best results are had at 121 ohms. Does your phono have tubes, FET or transformer for first stage gain?