Which SUT? .... for .3mv/10 ohms MC cartridge into 3mv MM input sensitivity

I wouldn’t worry about 6 mV signal after the SUT being "too high" - most decent MM stages will handle that perfectly fine, and personally I don’t like being in the reverse situation where I’m pushing my preamp volume control too high and still wanting more volume. And keep in mind you will often lose around 0.5 - 1 dB or so from the cartridge being loaded by the SUT - depending on its coil impedance and SUT ratio - so in the case of 20x and 10 ohms coils you lose 0.7 dB of signal from the loading, so that’s actually netting you about a 5.5 mV signal (down from 6 mV) anyways. 5.5 mV is pretty close to ideal for most MM stages.

Heck, my 0.3 Koetsu into a Sky 40 sound awesome on my VAC MM stage, and that’s netting over 10 mV of signal after the SUT! You certainly don’t want to overload the MM stage input, but good stages have lots of margin and will still sound good until you’re way off base.

I also wouldn’t worry too much about hitting a specific target loading number with a SUT. You definitely want to avoid loading the cartridge down too much, keep the load at least 6x - 10x the coil impedance. But beyond that, it’s mostly about choosing a ratio to the right output level. It’s not like active MC stages where you can get obsessed with finding the "perfect" load number. Once you get a good SUT match you will hear it and be happy! Recommendations from those who have your particular cartridge can be very valuable. But like I said before, the Bob’s Devices Sky have been great all-’rounders from what I’ve thrown at them.

impedance is what effects the sound
too low = dull. too high = too bright

As a general rule of thumb that is often true in the case of low output moving coil cartridges. But the effect is also dependent on the phono stage, and for that matter on the capacitance of the cable connecting the output of the SUT to the preamp. (The shorter that cable is and the lower its capacitance per unit length is the better, assuming accuracy is the goal).

.3mv cartridge x 21.5 = 6.45mv = TOO HIGH SIGNAL STRENGTH

Nope. See below.

.3mv x 10 is 3mv, TOO LOW? (mx100z phono sensitivity is 3mv)
.3mv x 20 is 6mv" TOO HIGH?

I PICKED THE WRONG DAMNNN CARTRIDGE!!!

While sensitivity specs for power amplifiers can be useful, I suggest that you completely ignore such numbers in the case of preamps. All it means in the case of a preamp is what I described in my initial post, and pretty much all it is useful for is calculating the gains of the phono and line sections of the preamp (if they are not explicitly specified), as I did in that post.

A 20x (26 db) SUT will boost the rated output of the 0.3 mv cartridge to 6 mv, as you indicated. 6 mv is only about 1.6 db greater than the 5 mv ratings of two of your present MM cartridges. For a single-turn rotary volume control (as is provided on your MX110Z) a 1.6 db change in volume typically corresponds to around 10 degrees of rotation, and perhaps even less. So with the new cartridge and a 20x SUT you would simply be setting the volume control a tiny bit lower than the settings you presently use with those two cartridges, to achieve the same volume.  (This assumes that the specs are reasonably accurate, of course).

Regards,
-- Al

AU-320 at 40 ohm position the step-up ratio: 1:10  and at 3 ohm position ( if I remember. ) : 1:33.

 When you have it you can try it both positions and decide which works better for you. I t think the 40 ohm position but......

R.

Cartridge just delivered, ordered 2 days ago. Amazon Prime is a waste of a lot of fuel for single item deliveries, but nice when you want it quick.

I jerk myself around when learning new stuff, so thanks for all your patience. And I always imagine others learning like myself following along

certainly I like the features of the Denon AU-320, and you have all given me confidence,

not to mention, Bill will be bringing his Denon SUT, that's what I will hear for the first time.

Nice to know 6mv is not too high. Changing the volume is easy, using 11 o'clock with 5mv shure now.

I just found an Ortofon ST-7 (single input, no bypass) it's specs:
Frequency response: 15-45 kHz (+0 dB -2,5 dB)
Gain: 24 dB at 1 kHz
Recommended cartridge impedance: 2 Ω - 60 Ω
Recommended load: 47 kΩ // 200 pF

chart I found converted +24db to 15:81x
result then 4.75mv (before loss); 188 ohms

I like how many Denon's are for sale, not too costly.

Yes, Bob's Devices Sky looks awesome, I am hoping to keep the cost down

AT-650, I like the three options 3, 20, 40 and it has Pass, the 20 input gives an optional/potentially preferable sounding choice. (for this or future MC after I get hooked, the Pandemic never goes away, I keep wearing out cartridges!!!

this fidelity research FRT-4 is quite versatile
don't anybody buy it, I might buy my 75th birthday gift 3 years early

3 inputs; 3;10; 30; 100 settings AND Pass


https://www.ebay.com/itm/Fidelity-Research-FR-FRT-4-MC-Step-Up-Transformer/224002964237?hash=item34279dfb0d:g:z9MAAOSwGhRetPWr

specs

ManufacturerFidelity-Research/ Fidelity ResearchModel number: FRT-4.
specificationModel Model MC Cartridge Toroidal Core Step-up TransformerNext Impedance 3 ohm/10 ohm/30 ohm/100 ohm switchPASS(selectable) Load impedance 47kΩ to 57kΩ 50kΩPressure increase3Ω:31.1dB(35.84 times)10Ω:26.3dB(20.68x)30Ω:25.2dB(18.27 times)100Ω:20.0dB(10.55 times)
Frequency response 20Hz to 30kHz
Distortion Within measurement error range up to 2 Vrms of output voltage
External dimensions: 170mm (W) x 60mm (H) x 180mm (D)
Purchased new decades ago.Price at the time.54,000 yen (circa 1978)