Cartridge Loading- Low output M/C

Just to elaborate on what Lewm said, a small loading resistance corresponds to a big load. The reason is that the loading is a resistance across the outputs, and so the cartridge motor has to work hard to get anything past that small resistance.

Think about water flowing in a hose - if you have a tiny pinhole in the hose (a large resistance to water flow escaping), just about everything you put it at the faucet goes out the nozzle. But if you have a great big hole (low resistance to water flow escaping), not much comes out at the nozzle.

The analogy with electric signals is pretty good. Just remember: big loading resistance, small load on the cartridge. Small loading resistance, big load on the cartridge.

I built my phono/pre to allow loading from 5 ohms to 85K. It happens to sit within the manufacturer's suggested range most of the time - it depends on the record. Higher resistance 1K2 for piano, lower resistance 30R for records which were recorded too bright.

@atmasphere 

I didn't know most of that. Thanks for sharing!

Wyn, I note the the simple expedient of putting the 2120 Hz filter first has the effect of reducing RF by 50dB at 1MHz at the first device. Is it your view that an additional pole is required?

Thanks!

@almarg 
... in a hobby where a lot of audiophiles concern themselves with dubious and unexplainable minutiae such as which way a fuse is oriented an explainable and potentially significant phenomenon such as this seems to me to be a reasonable thing for audiophiles to be aware of.

Good Lord, Al, that's physics! It strikes at the heart of all that we stand for! Say 4 Hail Snakeoils and depart!

Thank you, Wyn. Food for thought - or rather, food for experiment. Another pole means another stage and another pair of complementary devices, so the trade-off is obvious. But next is the amplifiers' turn, so it will have to wait!

Thanks again for your insights.

Wyn, your coaching is much appreciated. However, I am running discrete differential amplifiers (MATxy devices) throughout, and there is no "bias/protection resistor in series with a high impedance node in the signal path". Also, I am using air or vacuum capacitors exclusively in the signal path, and so virtually any cap, let alone a 3300pF cap, is a non-trivial intrusion into available volume.

Also, I hear no signs of the problems discussed. Pops and ticks are mostly absent and unusually nonintrusive, even on 'good' grade records. So, for now, will leave the phono/pre alone. Thinking about direct driving my ESL's, for instance - do you have any thoughts about appropriate devices?

Thanks again for your interest.

Wyn, I'm not claiming anything original here, except perhaps my anal-retentive dedication to costly devices!

Speaking of which - direct drive ESL. I have new generation Quads, which I opened up as soon as the warranty expired. I found a step-up transformer for each stator, cheap WW resistors and ceramic caps with their high dielectric constant. Obviously, all of these had to change.

As you seem to be an owner of ESL's, obviously you know that the step-up transformer tends to ring unless the input is coupled through a resistor. I changed the step-ups to a toroidal device which drove both stators, requiring an input resistor of about an ohm, which is a natural place for nichrome wire. Since I needed speaker cables anyway, I thought,"Why not use the nichrome wire for both purposes?"

Now I am thinking of high potential amps driving the stators directly, without any step-up device. I was wondering if you knew about HV transistors, and if you could save me some time and some angst with awful prototypes. That's all.

Your cautions are accepted. I've been thinking mil spec circular connectors and cables encased in grounded shields, or mono blocks bolted to the back of the speaker bases.

Interesting parallelism. I went from Magnepan to ESL-57's to Prodigies to 2905's. That's been an 'absorbing state' for 15 years now.