[Aerobat]

I've been reading all over the net about MC loading, and I have to admit none of it makes any sense to me.  Say I want to use an Audio-Technica OC9 MK2 with the Piccolo.  The specs for the OC9 state a 20 ohm load impedance. 

Another MC cart I have is a Technics 310MC.  I found specs on Vinyl Engine that give an output impedance on 30 ohms.

Is there a simple way to translate a cartridge's specifications to the load setting on the Piccolo?

Thanks!

[Brinkman]

I've been reading all over the net about MC loading, and I have to admit none of it makes any sense to me.  Say I want to use an Audio-Technica OC9 MK2 with the Piccolo.  The specs for the OC9 state a 20 ohm load impedance. 

Another MC cart I have is a Technics 310MC.  I found specs on Vinyl Engine that give an output impedance on 30 ohms.

Is there a simple way to translate a cartridge's specifications to the load setting on the Piccolo?

Thanks!

Depends on how handy you are with a soldering iron. Are you building the Piccolo kit or buying it assembled? There's also no provision on the Piccolo for variable capacitive loading, not that it's even necessary.

FYI, output impedance and load impedance are not the same thing. The input impedance of a device "loads down" the output voltage of the device upstream of it (i.e. the variable input impedance of the Piccolo is a load with respect to the output signal of the cartridge). Output impedance is the reluctance of a device to allow current to flow out of it. We typically want this to be as low as possible. It is the result of how a device is designed and the components used and there's nothing that can be done to change this.

AT OC9 MK2:
# Specifications: Mounting: standard 1/2"
# Stylus: MicroLine
# Frequency Response: 15Hz-50kHz
# Stylus Construction: Nude Square Shank
# Cantilever: Gold Plated Solid Boron
# Output Voltage: 0.4 mV @ 1kHz, 5cm/s
# Channel Separation: 21 dB @ 10 kHz 31 dB @ 1kHz
# Channel Balance: 1dB @ 1kHz
# Tracking Force: 1.25-1.75g
# Dynamic Compliance: 9 cm/dyne
# Load Impedance: 20 ohms
# Weight: 8g

Piccolo:
Specifications
Gain   12, 20, 26 dB
Input Impedance   47, 100, 220, 470, 1k, 47k
Output Impedance   300 ohms
Bandwidth (-3dB)   10Hz to 1MHz
Distortion   <0.01% @1kHz
SNR   85dB ref 5mV A-weighted
Overload   140mV @1kHz @26dB
Size   3" x 5" x 2"
Power   6Vdc to 24Vdc @15mA
Battery Life   4 alkaline AA, 200 hours

The load settings in the Piccolo are useful, typical values. However, these values can easily be changed to any other values you may require. For instance, you could replace the 47-ohm load resistors with 20-ohm load resistors, or even replace all the load settings with a range of values more suited for MC only. Sometimes the manufacturer's suggested loading is not what ends up sounding the best to your ears, so leave yourself some wiggle room.

[Aerobat]

Thanks for the help -- I need to study this more.  I'm building the Piccolo. 

The 310MC is the only MC cart I currently own, but once the Piccolo is up and running (I'm using the Bugle as my Phono pre) I plan to get more into the world of LOMC carts.  I'm trying to gain a better understanding of them, and how the Piccolo and Bugle interact with MC carts.

Mark

[Brinkman]

Research the piccolo threads here. Others (and myself) have soldered sockets where the load resistors go so the resistors are easily swapped in and out. This means to don't have to desolder and resolder every time you would like to experiment with a different range of values.

I'd be more helpful but I have to leave the apartment really soon. Just search the piccolo threads here. Suffice it to say, I had planned on using my piccolo with MM carts as a slight gain stage with variable resistive and capacitive loading. That signal was going to be fed into my computer (via the Ripper) so I could endlessly fine-tune and analyze my turntable/cartridge set-up.

Unfortunately, this recent move postponed all such matters and now my only source is an ipod ran through the Castanet and a pair of AKG701s.

Good luck!

[poty]

Is there a simple way to translate a cartridge's specifications to the load setting on the Piccolo?

First of all - read the JH article about loading on his site (http://www.hagtech.com/loading.html).
Then - theoretically speaking the biggest power will send to the amplifer input if the output impedance of the source is the same as the input impedance of the the amplifier. But as soon as both output and input impedances are complex (and unknown) and not just resistive, the analysing is almost impossible. To complicate things even more - the load value will have impact on the amount of force the needle should overcome to move. Together with the stylus force this defines the ability to move freely, safety for grooves and tracking precision. So, the starting point (if the manufacturer has not specified the recommended load) should be load=output impedance.
In practice - you should experiment with the loading (that is why it is on Piccolo) and choose the value you like best.

[Aerobat]

Thanks -- I read the JH article, and it might as well be in Chinese.  But I'll take your advice to start with load=output impedance, and experiment from there.

[analog97]

There is nothing peculiar about your cartridge.  I would just build the Piccolo stock..I'll bet your cart sounds just fine and dandy at 2 or 3 of the standard settings.  Go for it.  The Piccolo is a wonderful device. 

[poty]

There is nothing peculiar about your cartridge.  I would just build the Piccolo stock.

Agreed.

[rublyow]

I'm not sure if you're actually considering buying the OC-9, or just using it as a hypothetical example, but to quote the At-OC9 ML/II manual:

"If a transformer is used, input impedance should be 20 ohms or higher. If a headamp is used, ideal input impedance is 100 ohms."

So you'd be just fine with the Piccolo headamp, as there is a 47 and 100 ohm impedance setting.