phono/preamp analog front end

Hi,
i can understand that energy has to go somewhere but still.

He doesn’t refer to the actual stiffness of the cantilever, but to the electromagnetic damping effect the loading applies, which affects the compliance of the moving system, I think...

@testpilot 

The Herron uses external loading plugs, although the designer feels it sounds best unloaded.

Interestingly I have always found my Herron to sound better with loading - and in fact at a loading usually very close to cartridge manufacturer recommendations.  I know some stages like Sutherland's Little LOCO uses transimpedance amplification so you never dial in the loading using a switch but there is still loading.  And then you have some Boulder stages that have fixed loading but with no switches.  It seems that @atmasphere is saying that only phono stages they don't present any cartridge load are properly designed...I'm still not totally understanding this, especially since the cart manufactures recommend a load.

I like the Tavish design preamps....I paired the classic with jensen transformer and running a hana el. The adagio comes fully equipped with the Jensen’s for more money....I think its Herb’s reference phono preamp....they are tube preamps made in NY USA....

Can you explain how the resistor loading makes the cartridge cantilever stiffer? This absolutely does not make sense to me.

Sure! All inductive electro-mechanical devices (like loudspeakers for example) have a magnet and a coil that interacts with that magnet. Now there’s a rule in electricity called Kirchoff’s Law which basically says that whatever energy you put into a system will be dissipated by that system. Its like Ohm’s Law in that it can’t be broken (unlike a speed limit); literally if you were able to get around it you would be creating Free Energy and with it a new branch of physics :) Seriously though, that’s the truth.


So in the case of a phono cartridge, normally it is driving a 47,000 ohm load which is the industry standard for the input impedance of a phono stage. Now let’s do a little math- if we put 5 millivolts into that 47000 ohm load, the resulting current is 0.00000011 amps. If we then change the load its driving to 100 ohms, then the current goes up if the voltage stays the same- it becomes 0.00005 amps; increased by a couple of orders of magnitude (since the resistance is reduced by a couple of orders of magnitude).


I used the 5mV number as an example. Obviously LOMC cartridges put out less voltage but are governed by the same rules.


If you multiply the volts times the amps you get watts. That’s the energy that the cartridge puts out. That comes from the cantilever, which is driven by the groove information interacting with that magnet. So now you’re asking it to put out a bit more energy and that energy has a price- whatever is causing it is going to be harder to move. In this case, the cantilever.


You can simulate this easily with any woofer. Without anything connected to it, its easy to move with your hand. But if you short out its terminals, it gets quite stiff! Try it sometime- this happens for the exact same reason.


Now I’ve known about the effects of loading, the RFI issue and the ticks and pops issue with phono sections for about 30-35 years. But I’d not really thought about the effects on the cantilever until Jonathon Carr (of Lyra fame) pointed it out to me in a conversation about loading we had at the Munich show in Germany a few years ago. Of course what we are talking about are very small forces, but the groove itself and some very audible changes that you can do by adjusting the cartridge are all microscopic. So this should come as no surprise.

It seems that atmasphere is saying that only phono stages they don’t present any cartridge load are properly designed...I’m still not totally understanding this, especially since the cart manufactures recommend a load.

They do- and its hard to say how many cartridge manufacturers actually understand what’s happening here. But some do (Lyra for sure), even so they won’t have any idea what phono stage the customer is going to use (nor for that matter the tone arm cable, whose capacitance is a variable in all of this) so they usually specify a ’load’ resistance regardless. But it should be understood that the actual correct value will vary from system to system as the tonearm cable capacitance and the input capacitance of the phono preamp are variables.


Here’s a link that gives a bit of info on how the resonant peak sets up:

http://www.hagtech.com/loading.html