Parallel Resistive Loading

[AvFan]

Rothwell is entirely right in this. I model my MC cartridge/pickup arm/SUT/preamp extensively and getting a good match to the actual frequency response and how it behaves as load is changed is quite tricky.
Below is a SIMPLIFIED model of such a system, just to show how complex it is. Caveat emptor...

View attachment 1480917

I recall you saying in the past you'd spent some time on the cart/SUT/preamp analysis. Wow! I will have to be satisfied with far simpler attempts. Like...trial and lots of error.

Of course, it would make sense to treat the cartridge and transformer as an integrated system and fine tune the performance that way, and in that sense these tests are valid. Just be wary about drawing universally applicable conclusions from them.

I better understand what you've said about loading the secondary side of the SUT. I can't tell from the photos if adding resistors reduced the output and the calculated load isn't correct because the SUT is now part of the system when resistors are added to the SUT's secondary side. So if I want to add resistors on the primary side of the SUT to load the cartridge what is the formula? Will this provide an accurate load on the cartridge?

Lastly, Jensen and Sowter show Zobel networks on the secondary side of their SUTs without knowing what cartridge will be used. Do you think these networks are approximations? Since the values of the resistors and capacitors are similar for both manufacturers can we draw any conclusions about how these networks perform based upon a SUT's turn ratio?

 

[edwyun]

Concluding that a particular cartridge is optimised by a particular load impedance based on this type of test would be a mistake in my opinion.
Of course, it would make sense to treat the cartridge and transformer as an integrated system and fine tune the performance that way, and in that sense these tests are valid. Just be wary about drawing universally applicable conclusions from them.

Agreed. Just a data point in a particular setup. Not universal conclusion given all of the variables.

 

[rothwellaudio]

So if I want to add resistors on the primary side of the SUT to load the cartridge what is the formula? Will this provide an accurate load on the cartridge?

The load as seen through the transformer is the load on the secondary (usually 47k) divided by the square of the turns ratio. A resistive load on the primary side of the transformer is simply the value of the resistor. The two loads (primary and secondary) combine as two resistors in parallel.
I'm not sure the idea of an "accurate" load is a particularly useful one. The idea that an mc cartridge needs to see a particular load impedance is a popular one but I'm not sure how much truth there is to it.

Lastly, Jensen and Sowter show Zobel networks on the secondary side of their SUTs without knowing what cartridge will be used. Do you think these networks are approximations?

Not approximations as such, but they will be based on the assumption that the source is a particular impedance - maybe 10 ohms for mc cartridges or 200 ohms for dynamic microphones for example.

 

[wyn palmer]

The load as seen through the transformer is the load on the secondary (usually 47k) divided by the square of the turns ratio. A resistive load on the primary side of the transformer is simply the value of the resistor. The two loads (primary and secondary) combine as two resistors in parallel.
I'm not sure the idea of an "accurate" load is a particularly useful one. The idea that an mc cartridge needs to see a particular load impedance is a popular one but I'm not sure how much truth there is to it.

Not approximations as such, but they will be based on the assumption that the source is a particular impedance - maybe 10 ohms for mc cartridges or 200 ohms for dynamic microphones for example.

Simulations, measurement and listening all confirm that there is no "ideal" load for a MC cartridge or even a common nominal load.
The responses are dominated by two completely uncoupled mechanisms- the electrical LC resonance and the mechanical cantilever resonance. The load resistor helps to damp the electrical resonance and any load capacitance adds an additional low pass, but neither effect the cantilever resonance. The best you can hope for is that the extra low pass helps to reduce the mechanical peak that likely exists at high audible or ultrasonic frequencies. The electrical series resistance and inductance in a MC can vary by at least an order of magnitude and the "recommended" load capacitances can go from zero (as low as possible in effect) to >1uFs.
This is a complex problem with no simple answer, which is why I resorted to measurements and simulations so I could better understand what I was hearing...

 

[bharry]

I just picked up a MCZ stylus off of Bartertown and while I'm waiting for it to get here I've been researching how to get it to work properly with my Grado X1+. Specifically, I want to put together a plug like DaveyW made in this thread.

I've already ordered the RCA Y splitters and the RCA plugs from Amazon.

I'm going with a 47k ohm (24k ohm load) resistor which based on what I've read, will give me the best results. I'm also ordering 22k ohm & 10k ohm just in case,

I always get confused when I look at Mouser because of all the options so I thought I would ask here before I put in my order.

Is this what I want to order from Mouser?
Vishay- Metal Film Resistors - Through Hole .4watt 47Kohms 1% 1/8watt body size
Vishay- Metal Film Resistors - Through Hole 0.4watt 22Kohms 1%
Vishay- Metal Film Resistors - Through Hole 1/2watt 10Kohms 5%

Thanks,
Brian

 

[marcmorin]

I just picked up a MCZ stylus off of Bartertown and while I'm waiting for it to get here I've been researching how to get it to work properly with my Grado X1+. Specifically, I want to put together a plug like DaveyW made in this thread.

I've already ordered the RCA Y splitters and the RCA plugs from Amazon.

I'm going with a 47k ohm (24k ohm load) resistor which based on what I've read, will give me the best results. I'm also ordering 22k ohm & 10k ohm just in case,

I always get confused when I look at Mouser because of all the options so I thought I would ask here before I put in my order.

Is this what I want to order from Mouser?
Vishay- Metal Film Resistors - Through Hole .4watt 47Kohms 1% 1/8watt body size
Vishay- Metal Film Resistors - Through Hole 0.4watt 22Kohms 1%
Vishay- Metal Film Resistors - Through Hole 1/2watt 10Kohms 5%

Thanks,
Brian

you won't need anything as big as 1/2 watt....dropping the load from 47K to roughly 23K won't be enough, you probably need to drop it to at least 14K if not down to 10K

 

[Redd House]

Vishay metal film through hole 1/4 watt 1%.
Get more than you think you need. They're cheap and you're paying the same for shipping.

 

[bharry]

you won't need anything as big as 1/2 watt....dropping the load from 47K to roughly 23K won't be enough, you probably need to drop it to at least 14K if not down to 10K

Vishay metal film through hole 1/4 watt 1%.
Get more than you think you need. They're cheap and you're paying the same for shipping.

Thank you, this is very helpful. Putting in the order right now.

 

[bharry]

I got the MCZ a little over a week ago, installed it on my Grado X1+, and dropped the load down to 10k. I haven’t experimented with any other loads yet but I’m really happy with the results so far. Here’ a few pictures of the setup.

 

[marcmorin]

I got the MCZ a little over a week ago, installed it on my Grado X1+, and dropped the load down to 10k. I haven’t experimented with any other loads yet but I’m really happy with the results so far. Here’ a few pictures of the setup.

Looks good, looks correct.............

Enjoy

 

[bharry]

I got the MCZ a little over a week ago, installed it on my Grado X1+, and dropped the load down to 10k. I haven’t experimented with any other loads yet but I’m really happy with the results so far. Here’ a few pictures of the setup.

The left channel of this Grado X1+ died on me over the summer. A couple of weeks ago I saw an ad on CL for a Grado MC+ vintage cart with a broken stylus. I bought it and the MCZ sounds excellent with it. I'm still dropping the load down to 10k.

I just picked up a Carver C1 premap and it allows for setting the phono loading at either 0pf, 180pf, or 390pf. I'm not sure how this would work with dropping the load down to 10k like I am now. Do I still continue to drop it down or do I switch to one of the settings? Is this something I just need to play with to see what sounds best?

Thanks!

 

[Thunderbox]

I have had the Y plugs and the resistors for a while but this post has givem me the incentive to start soldering the resistors in.

 

[Thunderbox]

I know these are very old comments but I'll respond anyway since this thread has been resurrected.
Yes, carbon resistors are noisy, but it isn't thermal noise. Thermal noise, also known as Johnson noise, is inevitable in any resistor and is temperature dependent, hence its name.
https://en.wikipedia.org/wiki/Johnson–Nyquist_noise
Carbon resistors produce noise in addition to thermal noise and it's known as excess noise.
Still, the advice to avoid carbon resistors is good. Metal films are much better and don't cost a lot of money.

Doubtful if there would be any thermal noise generated considering the 2.5 to 6 mv output and extreemly low amperage creat just about zero wattage.

 

[rothwellaudio]

Doubtful if there would be any thermal noise generated considering the 2.5 to 6 mv output and extreemly low amperage creat just about zero wattage.

You may doubt it, but all resistors generate thermal noise. The link in the post you quoted even gives you all the formulae for calculating it. Did you read it?

 

[Thunderbox]

You may doubt it, but all resistors generate thermal noise. The link in the post you quoted even gives you all the formulae for calculating it. Did you read it?

Considering the number of resistors in a component the noise must be so little it isn't even heard.

 

[rothwellaudio]

Considering the number of resistors in a component the noise must be so little it isn't even heard.

I'm not going to bother arguing with you. The theory of Johnson noise and noise in amplifiers in general is well researched and well understood. The knowledge is there if you should care to study it.

 

[Thunderbox]

I'm not going to bother arguing with you. The theory of Johnson noise and noise in amplifiers in general is well researched and well understood. The knowledge is there if you should care to study it.

We are done. Sorry to have pressed you for info.

 

[DaveyW]

I just picked up a Carver C1 premap and it allows for setting the phono loading at either 0pf, 180pf, or 390pf. I'm not sure how this would work with dropping the load down to 10k like I am now. Do I still continue to drop it down or do I switch to one of the settings? Is this something I just need to play with to see what sounds best?

Thanks!

Glad to hear you’ve got the MCZ singing again


Grado’s are fairly inert to Capacitive loading, much more receptive to Resistive loading.
But have a play and confirm for yourself

 

[rothwellaudio]

We are done. Sorry to have pressed you for info.

Pressed me for info? I've given plenty of info in this thread. You simply denied the facts.

 

[bharry]

Glad to hear you’ve got the MCZ singing again


Grado’s are fairly inert to Capacitive loading, much more receptive to Resistive loading.
But have a play and confirm for yourself

Thanks, I’ll try out the different settings and report back with my findings.