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Step Up Transformers? Pros / Cons?

SIY

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Given all of the above, and knowing that my MM input is configurable for inputs from 1mV to 15mV, is there any benefit to using the lower 1:8 ratio instead of the 1:16 ratio?

Also, do I need to worry about capacitive loading, like with a "true" MM cart, or does that not apply to stepped up MCs?

In order:

There may be, but without doing some scope testing, you won't know. The step up calculations don't take frequency response into account (that's a far more complex situation) and that's where one configuration might be better than the other. As I've said over the years like a broken record (!), the details of loading the transformer secondary are extremely important and are not attended to in 99% of setups, despite involving about ten cents worth of components and two minutes of soldering. IMO, anyone charging more than a couple hundred bucks for a transformer box ought to do this for the customer.

The loading of low output MC cartridges is, despite legend, extremely non-critical: unlike MMs, their inductance is negligible. Loading of the transformer secondary (when used) is the key issue. The only things the cartridge load resistance affects is level and (to a small degree) noise.
 
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watchnerd

watchnerd

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In order:

There may be, but without doing some scope testing, you won't know. The step up calculations don't take frequency response into account (that's a far more complex situation) and that's where one configuration might be better than the other. As I've said over the years like a broken record (!), the details of loading the transformer secondary are extremely important and are not attended to in 99% of setups, despite involving about ten cents worth of components and two minutes of soldering. IMO, anyone charging more than a couple hundred bucks for a transformer box ought to do this for the customer.

The loading of low output MC cartridges is, despite legend, extremely non-critical: unlike MMs, their inductance is negligible. Loading of the transformer secondary (when used) is the key issue. The only things the cartridge load resistance affects is level and (to a small degree) noise.

Thanks.

I'm going to restate the question more pragmatically and specifically to make sure I'm clear in my understanding:

My phono input in MM mode has configurable capacitance in pF.

What's the proper pF on my phono input when using a SUT?

0 pF?

Or something else?
 

SIY

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Bad news- there's no magic formula without doing a detailed model and knowing a lot of details. And I will nearly guarantee that your MM phono input does not have a well-specified input capacitance.

The only way to do it is on test, using a scope and square wave generator. These are relatively inexpensive instruments and the optimization is easy to do.
 

sergeauckland

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Bad news- there's no magic formula without doing a detailed model and knowing a lot of details. And I will nearly guarantee that your MM phono input does not have a well-specified input capacitance.

The only way to do it is on test, using a scope and square wave generator. These are relatively inexpensive instruments and the optimization is easy to do.
On top of that, there's the capacitance of the pickup arm to phono stage cables, which can be anything, although if they're the originals, the manufacturer may be able to tell you what they are .

On my EMT TSD15 cartridge, I use a standard MM 47k input as it's quite low noise enough so not bothered by trying to match a third party SUT to a cartridge. On my AT33ML cartridge, I use AT's recommended AT630 SUT but haven't tried to do any more detailed matching.

S
 

SIY

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On top of that, there's the capacitance of the pickup arm to phono stage cables...

Exactly so, and that's a factor that must go into the adjustment, either by using a dummy cap that is equal to the input plus cable capacitances or measuring in situ. Oh, and you have to use a 10x probe, otherwise the test lead capacitance will throw things off.

Like I said, not hard, but there's details to be attended to.
 

JP

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Exactly so, and that's a factor that must go into the adjustment, either by using a dummy cap that is equal to the input plus cable capacitances or measuring in situ. Oh, and you have to use a 10x probe, otherwise the test lead capacitance will throw things off.

Like I said, not hard, but there's details to be attended to.

Mind writing that up for those interested?
 

JP

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:thumbsup:
 
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watchnerd

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Bad news- there's no magic formula without doing a detailed model and knowing a lot of details. And I will nearly guarantee that your MM phono input does not have a well-specified input capacitance.

The only way to do it is on test, using a scope and square wave generator. These are relatively inexpensive instruments and the optimization is easy to do.

Given that most folks using SUTs probably don't use a scope and wave generator, what do most SUT users do with regard to capacitance (not resistance) loading when running MC->SUT->MM input?
 

SIY

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Given that most folks using SUTs probably don't use a scope and wave generator, what do most SUT users do with regard to capacitance (not resistance) loading when running MC->SUT->MM input?

If you're buying it new, the dealer ought to be able to set it up properly and earn their markup.

If you're doing it yourself or buying used, make friends with a local tech type and put it on their bench. In Seattle, that should not be difficult to find.
 

Blumlein 88

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Given that most folks using SUTs probably don't use a scope and wave generator, what do most SUT users do with regard to capacitance (not resistance) loading when running MC->SUT->MM input?
A scope.....A SCOPE......are you crazy???? You tune it by ear like a real audiophile. Guaranteed satisfaction. ;)
 
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watchnerd

watchnerd

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If you're buying it new, the dealer ought to be able to set it up properly and earn their markup.

If you're doing it yourself or buying used, make friends with a local tech type and put it on their bench. In Seattle, that should not be difficult to find.

It's a Devialet Expert 400 with software configurable inputs. The phono stage is assignable to any RCA inputs, goes through an ADC, applies RIAA (or other alternative LP EQ, like Decca) via DSP.

It can be in MM or MC mode, input voltage is configurable, as is loading, both ohms and, for MM, pF.

Does the oscilloscope method apply equally well to software/DSP based phono stages?
 
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watchnerd

watchnerd

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A scope.....A SCOPE......are you crazy???? You tune it by ear like a real audiophile. Guaranteed satisfaction. ;)

Seriously, though, what do most SUT users do?

Because they're sure as heck not busting out oscilloscopes.

Do they just set the MM to 0 pF?
 

Tom C

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If you get frustrated when trying to fine tune by ear because you’re not sure you can tell which setting is best...because you’re not sure you’re hearing a difference...maybe it’s because there isn’t much difference. Which could be why most people don’t fret too much about it. Myself, as a rule of thumb, if I add something and I don’t clearly hear an improvement, I take it back out. So, when running an MC cart to an SUT and into a phono MM input, I set capacitance at the lowest possible setting. It’s often done that way, just put it at the lowest setting, and that was what was recommended to me by Bob of Bob’s Devices. I’ve been quite happy with the result.
Of course, systems differ in myriad ways, so if you are able to find a setting that sounds better than the others, go for it.
If you want to do a Rothwell style optimization, like a professional would do, you have to get a scope. But it’s not going to change the outcome much.
 

Frank Dernie

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@Frank Dernie when you used a SUT with your Devialet Premiere, what did you you set the pF loading for the MM input?
Sorry I didn't use the SUT with the D-Premier. I only put it back in the system after I updated to a 250, as was then, and thought the phono input was a bit noisy. I didn't even do a comparison of with and without SUT on the D-Premier.
In my ignorance I had no idea the capacitance would be an important factor with a MC>SUT installation. I know it is with a MM cartridge.
I am due to see the guy who designed the D-Premier phono stage today and ask him some questions, but i doubt he will publically make comment on this.
FWIW I use the word "update" rather than upgrade since, for me it wasn't an upgrade. I have no chance of ever having a SAM profile for either of my main speakers so the extra DSP capacity hasn't been any use to me yet and the loss of the HDMI input and apparently more noisy phono input were backwards steps in my system. I do use the USB and Ethernet inputs but they aren't as beneficial to me as the losses.
Mind you I part exchanged my 800 for an Original d'Atelier for the colour so I am pretty capable of illogical impulse buys.
 
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watchnerd

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In my ignorance I had no idea the capacitance would be an important factor with a MC>SUT installation. I know it is with a MM cartridge.

Likewise. I know it is with an MM cart. But I've never even seen pF calculations / setting mentioned in MC>SUT>MM inputs.

With the 250, did you just set it to 47k ohm / 0 pF with the SUT?
 

Frank Dernie

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Likewise. I know it is with an MM cart. But I've never even seen pF calculations / setting mentioned in MC>SUT>MM inputs.

With the 250, did you just set it to 47k ohm / 0 pF with the SUT?
Yes, and that is where it still is with the Original d'Atelier, which is the same.
I sort of assumed that Ortofon's transformer was an appropriate match for their low output MCs into a standard MM input.
 

Blumlein 88

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Seriously, though, what do most SUT users do?

Because they're sure as heck not busting out oscilloscopes.

Do they just set the MM to 0 pF?
Well I had an Ortofon SUT with no settings and at the time a CJ PV5 preamp with also no settings on the MM input. It had 100 picofarads permanently shunted on the phono input with polystyrene capactors. You could have soldered in different values.

I later switched to the SOTA headamp, and all my later preamps had MC as well as MM phono inputs. On MC phono units, I would currently use an ADC to check for a near ultrasonic peak and adjust accordingly. You'll need a test record with some tones or sweeps on it. I think the old CBS test record went to 20 khz, and you could usually see a rise if a peak was just past 20 khz. The Ortofon test record went above 20 khz.

Then I've not used LP's in a couple decades though I from time to time help a couple friends who have them. Just reminds me of how great CD and digital wav files are for musical enjoyment. And if my friend with the Souther Triquartz arm needs me to adjust it again, I'm not sure my eyesight or hand steadiness are up to it anymore. Not to mention how much of a brain twister that Souther arm is. Every adjustment effects all the others, and it takes some visualizing to move it from one condition to another the way you really want it to end up.
 
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