Step Up Transformer Question

SUT (they are tricky, I got help here, did research, scratched my head, learned this).

Consider selected and future MC cartridges when choosing a SUT (or phono stage with MC):

You need to know both the cartridge’s signal strength AND it's coil's impedance to know what range of xFactor (enough but not too much gain) and that xFactor’s resultant impedance (that will be shown to the MM Phono Input).

Thus you want a SUT with several options of gain (xFactors) AND each of those xFactors give a RESULTANT impedance that will go to the Phono Stage's MM input (separate or in a Preamp).

Some equipment has independent options for gain and for impedance, they usually cost more, but are needed for some MC cartridges with signal strength/coil combos that need that separate adjustability. Best flexibility for unknown future cartridges.

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FORMULAS

GAIN = xFactor  = +____db.      

xFactor squared = _____?

RESULTANT Impedance ‘shown’ to MM Phono Input _____? 

47,000 (common MM phono stage is 47K) divided by xFactor squared ____ = impedance shown to the MM phono input (check your equipment’s MM Phono Input impedance, some not 47k)

The guidance for impedance shown to 47,000k is cartridge coil impedance __  x10.

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example: for current and future MC cartridges (including my friend’s cartridges we listen to here): I chose Vintage Fidelity Research FRT-4 to get PASS and 4 optional xFactors and their resultant impedance

Some/this SUT’s face numbers are confusing, I had to find the specs to know what the face settings meant: how much gain/resultant impedance shown.

PASS (for MM or High Output MC) bypasses transformers, unchanged signal to MM input

Face 3 ohm = xFactor 35.84 (+31db). 35.84 sq = 1,284. 47k/1,284 = 37 ohms shown to MM input

Face 10 ohm = xFactor 20.68 (+26db). 20.68 sq = 428. 47k/428 = 110 ohms shown to MM input

Face 30 ohm = xFactor 18.27 (+25db). 18.27 sq = 333. 47k/333 = 141 ohms shown to MM input

Face 100 ohm = xFactor 10.55 (+20db). 10.55 sq = 111. 47k/111 = 423 ohms shown to MM input

Luckily for me, it also has 3 tonearm inputs, front selectable.

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this shows it (ding in face panel) (price a bit low due to that)

 

 

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Entre ET-100 is similar (black or silver)

 

 

Other SUTs with flexibility can be found

IF you or anyone wanted a New MM/MC Phono Stage with Options, Project makes several among other companies

 

Simple right? It is, AFTER you have the chart of answers!

SUT Info Charts I gathered

 

Chart 2: Cartridge Column: my AT33PTG/II cartridge’s 0.3 mv signal strength and 10 ohm coil impedance is shown just change it to your cartridge’s numbers

When Considering a SUT or it’s setting: I start with Impedance shown to MM Phono Input, then check which xFactor ____? gives that result. Enough or Too Much gain?

The Bottom of Chart 2, Right Column: select the impedance ____ ? you want shown to the MM Input (guidance: cartridges coil impedance x10)

then go left, see if the Gain in DB of that xFactor is ENOUGH or TOO MUCH.

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Note: Calculated Signal Strength: Allow for a bit of loss, I just guess a little lower

 

 

Ortofon T30 SUT

My Phono system already sounded great, with ’regular’ phono cables.

When I bought my long tonearm, the Russian maker almost insisted I use this Ortofon

 

That TT, I had been using a basic cable from Amazon while waiting.

I heard ZERO difference, I used two ’upscale’ din cables that came with my other two tonearms. Plugged

Something wrong with the numbers

0.2 mv into 10x transformer is only 2mv signal out, that's too low for some/many phono inputs. Would cause volume controls near max, perhaps the volume control/circuit is noisy when raised so much.

10x is only +20db.

do you mean SUT xFactor 10 combined with the MM Phono gain will be 70db?

If something is great, but it hums, it ain't great.

 

 

Yes, I posted a photo of the SUT I use above: Fidelity Research FRT-4

Zero Noise at any setting, or arm selection.

My friend had some hum, Steve at VAS diagnosed it, the Grado cartridge that came with the Vintage JVC Turntable was the cause. He said MANY Grado's Hum. My Grado Mono (using PASS thru the SUT does not hum here.

My friend changed to a different cartridge on a spare similar headshell, nothing else, hum gone.

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One of the advantages of a SUT with multiple tonearm inputs, is you do not change the output cable or which preamp's input, it sends any selected arm out to preamp or phono stage.

I would check the specs of your phono Stage’s Sensitivity.

My McIntosh mx110z for instance, the MM Phono Input’s sensitivity is 3mv.

Signal Strength:

My cartridge’s output is 0.3mv. I use xFactor 18.27, thus signal strength to Phono MM input is 5.4mv. A bit of loss, guessing: perhaps 5.2mv, at least 5.0

Your cartridge 0.2mv x10 is only 2mv out to MM Phono input. I think too low, and perhaps the source of hum. A bit of loss, you might be getting only 1.8mv.

To find out, you could borrow a friend's SUT or Phono Stage with a higher xFactor, or order one from a source like amazon, with 30 day returns, try, keep or return.

Even if you don’t prefer it’s sound, it will tell you something about you existing x10’s involvement in the hum.

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I prefer a stronger signal than mx110z’s 3mv minimum, keeps preamps volume centered, and closer to my MM cartridge’s 5mv output.

Switching arms/cartridges, the volume is not that different. I change volume remotely via my Integrated Amp’s Volume, thus preamp’s volume never moves, except when I often swish it full left/full right a few times, to keep the internal contacts fresh, it’s a Vintage control. I also use contact cleaner on all the controls once per year to prevent noise.

Another Chart I had found: Cartridge Specs and Recommended Impedance Load. (you need to increase your monitor's zoom to read these).

I changed all my RCA interconnect cables to Locking Connectors. Mess with any cable, others do not get disturbed.

I got 2 sets of these video cables to make 3 pairs for audio, color coded ends, locking connectors, zero noise, great price. These are 12 ft long, I got 6 ft long, you just need to find the right length

 

these come various lengths, with Locking Connectors, many other choices. Remember, Amazon has easy returns if you find it is not the cable causing the hum.

 

 

dogberry

thanks, i'll check them periodically