Added an SUT...not sure I understood this

@dover 

The recommended loading for your cartridge is Min 100 ohms.

Min means minimum

and

If it sounds better at 20 ohms, there must be something wrong with your system.

since the OP has solved his issue I have to ask if 100Ω is minimum and 20Ω means something is wrong, what would happen if he used the MCCI current injection stage that would provide a less than 3Ω load and liked the sound?

dave

getting back to the OP.... He seems to state that he expects 6-8dB of gain in place of the nearly 20dB that a 1:10 suggests.  He then says he is getting the opposite effect which I take as less gain.  

for the OP.

In sticking with just the 40Ω (1:10) tap.  Does the gain increase, decrease or stay the same compared to the same cartridge directly into the MM input?

dave

@dover 

Do you not think the cartridge designer and manufacturer knows what they are doing when they recommend a minimum of 100ohms ?

If I had to guess that spec is set to assure near maximum output of the cartridge.  Changing the loading value makes subtle but easily audible changes for many.  I know of several people who routinely load MC carts at 3-5X the internal impedance.  They do this out of sonic preference and not out of ignorance or to thumb their noses at "accepted practice".  I have yet to see a published minimum load that comes anywhere near the <3Ω of the MCCI which precludes their use in general if one were to adhere to the manufacturer's suggestion.

but for those who are more open minded

Odd... it seems to me that insisting one trust a published suggested load over their ears is just the opposite of open minded.

I am not saying that the OP is correct in their 20Ω choice or exactly why that value was chosen.   It may very well be that the 4dB reduction in cartridge output from that cartridge-load ratio may be partially responsible for some additional noise.  The point I was / am trying to make is the disconnect between minimum recommended load and the use of a stage such as the MCCI.

dave

apologies to all for veering off topic here....

@dover 

I have yet to se actual measured frequency sweeps from a MC cartridge that show the ""rolled off" top end you suggest above.  Can you point me to some?

The only reason I took the time to write my post with regards to published specifications and recommended load was to inform the thousands of readers of these forums whom do not post, but might rely on what they read in the thread.

I have the same belief.... kinda...  I was just trying to point out to the 'thousands of readers of this thread' that the whole concept of "current injection" flies 100% in the face of blind adherence to the manufacturers minimum load spec.  ie...I see the natural conclusion of your logic to be:  if 100Ω is the minimum <3Ω cannot sound good so it need not be tried.

dave

@dover 

the last post in this thread from the OP is below:

@dover The sheet that came with my cart says 20 ohms. AT has not been consistent with their specs on the OC9 series.  More importantly, it sounds better around 20 ohms than at 100.  Plenty of people agree with me on this.  I'm not going to load it at 100 just because you won't stop yelling at me.  I'm going to load it at whatever achieves the best sound in my system. 

to which you responded with the text quoted in my first post here where you insisted there must be something wrong with his system.  

I applaud and support the OP's POV that what sounds best is best. I brought current injection into the topic because it is a perfect example on how an amplification method that many find appealing provides a load that is in stark contrast with what any cartridge manufacturer suggests as optimal.  I for one would like to see more discussion about how to reconcile this discrepancy.

dave

The maximum output of the cartridge will be with little or no load. 47K is the industry standard in this regard.

the industry standard of 47kΩ was adopted from the MM cartridge world and applied to the MC realm because is first and foremost "does no harm".... until you throw a SUT into the mix that is.  Once a SUT is added the load the cartridge can see can get vanishingly low to the point where you actually start losing gain as you increase turns ratio.  My best guess is that the min load value specified for a cartridge is a value that still assures nearly full specified cartridge output and has little or nothing to do with the sonic behavior of the cartridge.   

What I want to know is why the minimum load value that has to be strictly adhered to in the case of a traditional phono stage can be completely ignored in the specific case of the MCCI with a published input impedance of <3Ω.  

This is completely ON topic since it relates directly to the OP's insistance that a 20Ω load sounds best on his AT-OC9XML.  

dave

@woofhaven1992 

 The reason a cartridge sounds different under a heavy load is because the low load impedance suppresses output voltage.

so add more gain.  I'm not trying to be cheeky here but this becomes a problem related to what happens downstream of the cartridge and not with the load the cartridge sees.  If you load a cartridge severely and do not have a capable low noise good sounding stage after it things will indeed go south.... this is not a problem with the cartridge load per se but with the behavior of what follows.  

In the case of the IV preamp, the low input impedance (not quite the same as load impedance)

how can the two be separated form each other?  from the cartridge POV, how can 3Ω be different than 3Ω?  I am speaking primarily about the effects of the load on the electromechanical behavior of the cartridge and what impact that may have on the sound.

 but those changes cannot be attributable to the effect of loading on voltage output since the IV preamp effectively ignores that effect.

Sure the IV preamp can ignore that its low input Z effectively reduces the output voltage to 0.  My question is how can the cartridge ignore that it is seeing a load that is possible a fraction of its internal impedance?

Lets get back to the simple question I asked....  If going well below a cartridge manufacturers load is not recommended, how can we reconcile the use of transimpedance amplification or in your case a load that is 1.7X the cartridge internal impedance?

It is my belief that when specified by the cartridge manufacturer the load value range would relate to the behavior of their cartridge and not in response to the unknown capabilities of what follows.  In any case... Like you I feel that number is only a suggestion and people should feel free to use whatever load sounds best to them.

dave

JCarr makes the exact point I am ultimately trying to get to when he says the below.

 Also, IV phono stages sound qualitatively different to voltage amplification phono stages., and part the reason is that undoubtedly the cartridge is forced to operate into a zero-ohm load (or some other values that is quite close to the cartridge's internal resistance).

I don't necessarily agree with his use of the term "forced" but that is for another day.  He attributes  "part of the reason" for the difference  in sound to the load the cartridge sees and I fully agree with that thought. Since this branch of the  topic is about the load the cartridge sees and not how that load is obtained, discussing the difference between current and voltage amps is not at issue.  It just so happens that a current amp gives an extreme example of "non-traditional" loading.

 A cartridge is a two terminal device that sees a two terminal load downstream.  It doesn't know or care what form of amplification that load takes, it just does what the load tells it to do.  

dave

You are correct in your conclusion, but IMO asking the wrong question.

I am the only one here asking the relevant question in this situation. This all goes back directly to the insistence that something was broken in your system if your cartridge sounds better with a 20Ω load.  The only question I asked (and has yet to be answered) is how does one account for the use of a load well outside a manufacturers recommendation (ie a current amplifier as an extreme example) and still adhere to the wishes of the manufacturer?

In your particular case I trust your assessment that the sound is good and suspect that anyone that insists otherwise based on a published spec is in error.  Who knows I may be he only one with this belief.... it wouldn't be the first time.

I did not  drag this off topic into how current amps differ from voltage amps, others took it there.  I really think this is a simple question that apparently nobody seems to have a good answer to.

dave

Ralph...  we have been over this.  I made a point above to never mention ground and simply referred to the cartridge as a two terminal device feeding a two terminal load.   If the goal of that load is to maximize current draw then by necessity it must be low in value.  Since both Ohm and Kirchoff must be obeyed.... all of the current leaving one terminal of the two terminal cartridge must traverse the load and return to the other terminal.  The application of Ohm to this situation clearly defines all of the parameters at hand.

dave

@dover 

I cannot fathom how you cant see the difference between increasing gain and reducing gain.

again... not the topic at hand.  The cartridge doesn't magically see a sut and say 20Ω is fine and scoff at that same 20Ω if it is a load resistor to ground before a Jfet.

I concur with lew and it makes no sense to me how a loading a cartridge can have different "ideal" values for different amplification types.  I think much of the confusion here stems from AT expecting you to pair their cartridge with their SUT.  The AT1000T has a 20Ω input setting that claims a 26dB gain and specifies a 47kΩ termination.  Simple math tells us that 26dB = 1:20 which reflects back 117Ω to the input labeled 20Ω.  In this convoluted  case 20Ω really does = ~100Ω!  Assuming there are not other loads or networks inside the AT1000T to truly provide a 20Ω load,  this small part of the discussion now makes sense.    This labeling system is typical to the Japanese SUT's and the Denon that started this whole thread uses a similar input labelling method.  Essentially the inputs are labeled  with the approximate impedance of the cartridge they expect you to feed it with with no hard and fast rules as to how those numbers were devised.

Now back to the OP and his finding that a 20Ω actual load sounds best.  Sure he possibly got to that value by following a bunch of conflicting / confusing data but ultimately that is where he stayed.

dave

@dover 

This splinter of the OP's tree is in reference to the load a cartridge sees and in particular any variance from the cartridge manufacturers suggestions. 

Lewm was comparing active mc amplification vs SUT's.

No....  Lew was wondering in what world  20Ω = 100Ω. How can 20Ω be unacceptable from an active stage but perfectly OK from a SUT?  I entered my guess at an explanation that the 20Ω value is not an actual load value but the recommended input to use of the AT1000T.  This input happens to load the cartridge at just over the 100Ω manufacture spec.  Simply put a somewhat confusing manufacturers data sheet reconciles the difference and keeps the manufacturers suggestion consistent.  

It is clear from your conclusion that you do not understand how current mode and voltage mode gain stages work

Other than the load value presented to the cartridge, how a gain stage operates has zero bearing on the topic of cartridge loading.  My only reference to current amplification used a specific model (MCCI) since it has a published input impedance number of <3Ω.  To be clear... it is the 3Ω that is the issue here NOT that it is a current amp.  From the most basic perspective I want to know from you how a <3Ω load can be used with a cartridge that has a 100Ω minimum recommended load and possibly sound good?  I can't be the only person who sees this disconnect.

Since you seem unwilling or unable to answer that simple question, let me frame the same situation differently:

Can we agree that the OP's cart into a 1:20 will see just over a 100Ω load and present approximately 8mV to the input of a "generic" gain stage?   Now lets change that 1:20 to a 1:50 and then place an 11Ω resistor across the primary to add an additional load to the cartridge directly.  The voltage output of this combo will be the same 8mV into the same "generic" gain stage. Now the load the cartridge sees will be 7Ω which is well below what you would deem acceptable.  Both the measured and the subjective sonic results of the above experiment surprised me and really got me thinking about what loading a cartridge really does. It also makes me wonder what the manufacturers published values are based on.  

dave