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    Building, troubleshooting and testing of these amplifiers should only be
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    the safety precautions around high voltages.

Input inpedance

Building my own amplifiers I’ve always loaded my mc cartridge according to the supplies advice (most often 100R seen by the cart throw the step up transformer).

However. Many, many years ago Allen Wright (Vaccum state) advice me not to load the cart that hard. He advised me to keep the 47K load at the phonoamp input, making a 470R load seen by the cart throw a 1:10 step up.

I didn’t follow his advice then. But now I have seen several post where others claim that to hard loading could making less than optimal conditions for the step up (Lundahl transformers in my case).

I can’t say that I can hear huge difference loading my mc (ZYX R100H) with 100R or 470R (I have old ears)

But how do you load your carts?
 
@ejp
I’ve spoke to Per Lundahl about optimal loading of their mc step-up transformers, and they don’t specific that (Im currently using LL9206/1:10/Dynavector Carat Ruby (30R) and LL1931/1:8/ZYX R100H (8R), both carts currently see a mirrored load of 100R).

Surelly, I could try to measure/tune it by myself, but still. I wanted to hear from you, how you do it, and if you had give it a thought.
The optimal transformer loading is by the way, seldom a pure resistive one. But include a notch. a rc-link or something controlling a resonance peak. The resistive loading is not the optimal way to do it. But perhaps it’s good enough?

In my previous post I mentioned a discussion with Allen Wright. He claimed that the 100R loading, stated by the cartridge manufacturers, was picked for optimal frequency response, but that with a purelly resistive load, not the reactive load that a step up transformer with a resistive loaded secondary winding give.

He claimed that the step up transformer has some many stray components, that it would be impossible to take all into account.
I’m not saying this is a fact. But according to Allen a 47K loading (470R seen with 1:10 winding ratio) would be a better choice than the specified 10K (100R seen with 1:10 winding ratio) taking t some of he stray components in to account.
 
But how do you load your carts?
I have made some of this stuff some years ago


1751539451516.jpeg


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Three gain
Trafo custom by Brian Sowter ( now I have a clone for the future)
24 position of resistors in parallel to MM input.
The best way is to have the MM set at 100kohm ( as my phono)
In this case the range of optimization is almost perfect


Walter
 
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Allen Wright ... claimed that the 100R loading, stated by the cartridge manufacturers, was picked for optimal frequency response, but that with a purelly resistive load, not the reactive load that a step up transformer with a resistive loaded secondary winding give.
I don't buy this reasoning. At the frequency extremes (<40 Hz, >10 kHz), perhaps.
I just load my DL-103 with a 1:16 Lundahl and 47 k on the secondary, that is about 180 R on the primary. I am happy with it.
 
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A properly loaded s.u transformer presents a resistive value to the primary, not reactive.
Yes sure, that’s obvious.
But what is a “properly loaded s.u transformer”?

I would say it depends on how close you look. All winded devices has inductance, wich means they are all reactive devices.
If “properly loaded” means zero reactance, all inductive- and capacitive- components must fully be compensated for to fully be a resistive device.

Yes. You can tame ringing (resonance) with a resistive loading. But it’s that to say that it is “properly loaded”?
It might be good enough for this application. But what Allen ment, was that a trasformer is not just a winding ratio, it has several stray components that will influence just as much as the resistive loading.
 
The coupling with step up is not only the electrical specs, cartridge and trafo; each configuration has a proper results in terms of electrical voltage who involved the mechanical part of the installation.
Every MC installed in a turntable show a different andament of the dynamic signal strictly related with the arm and the turntable with a little contribution of the cable .
And this is mainly on a low end due the non perfect rigidity of the system in addition with the (in case ) low value of inductance of trafo.
So the trimming of the load seen by trafo can set a "gold point" who is the best sonic result . ( that is personally, of course)

In attach some tests

This is a Tango 999 freq. response, ratio 1:10 with different setting on the Z on secondary; Ap sys2 with 40 ohm Zout and a signal standard cable to simulate a real connection.
1751631014155.jpeg

The response is good and the level drop around 1 dB for wide range of Z; different load for MC, some changes on sound


999 with 1:20
Z s = 10 ohm

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999 with 1:40, a little more complicated but good results.

Zs = 2,5 ohm

1751631632548.jpeg