Thanks as always, and this time I will definitely wait for advice before getting anything. I am not in a hurry for this, Bill will loan me one of his SUT’s until I get my own.
Q1) No, 3 mv is the input voltage for the phono inputs which will result in the main output of the preamp providing its rated output (3 volts, assuming that spec is the same for the MX110Z as for the MX110), when the volume control is at max.
3 volts/3 mv = 1000x = 60 db overall gain
Also, since the sensitivity of the Aux (line-level) input is 300 mv we can deduce that the preamp’s phono stage itself provides a gain of 300 mv/3 mv = 100x = 40 db, which is typical of the gains provided by MM phono stages. The line stage provides the other 20 db.
Q2) Correct, but keep in mind that the choice of SUT gain will also affect the load impedance that is applied to the cartridge (see below).
Q3) Not correct. Doubling of gain corresponds (to a very close approximation) to a 6 db increase. So doubling the gain from 10x to 20x corresponds to 20 db + 6 db = 26 db.
db = 20 x log(Vout/Vin), where "log" is the base-10 logarithm.
Q4) Given Q3, 40 db would be way too much gain. It would also result in an absurdly low load impedance being applied to the cartridge (see below).
Regarding ...
... 10 ohm coil x 10 = 100 ohm
... That is a good basis for choosing a SUT. See this writeup, which also addresses some of your other questions.
The voltage gain of a SUT corresponds to its turns ratio (i.e., the ratio of the number of turns in its secondary (output) winding to the number of turns in its primary (input) winding. The impedance transformation provided by a SUT corresponds to the square of that ratio. So to apply a 100 ohm load to the cartridge when the SUT is working into 47K the turns ratio (and hence the voltage gain) should be:
Square root(47000/100) = 21.7.
A voltage gain of 21.7 corresponds to 26.7 db. So a 26 db SUT (i.e., 20x, sometimes also referred to as 1:20) should be a good choice. You may want to take a look at the SUTs offered by Bob’s Devices, where the paper I linked to earlier can also be found.
thanks, I could handle multi-million budgets for my clients projects, but this kind of math, my mind just won't go there at my age. I appreciate simplifying it to 20x
Given that 20x will be good for this .3mv cartridge, I suppose it might be wise to have some extra boost for a possible lower signal MC, what would you suggest as max?
That’s hard to say, Elliott (see the last paragraph on the first page of the writeup I linked to), but I wouldn’t suggest going much higher than 20x, if at all. For example, if you went to 30x (which is about 29.5 db, just 3.5 db more than 20x) you would be loading your new cartridge with only 47000/(30 x 30) = 52 ohms!
Also, given the 20 db gain of the preamp’s line stage (which is significantly higher than average), coupled with its 40 db MM gain and 29.5 db of SUT gain, the 0.3 mv rated output of your new cartridge would be boosted to about 9 volts if, hypothetically speaking, the volume control were at max. And the peaks of some recordings can cause cartridges to exceed their rated outputs (which are based on certain standard test conditions) several-fold. Which means that you may risk overloading some of the circuitry on the dynamic peaks of some recordings (especially circuitry which is "ahead" of the volume control in the signal path), causing distortion, and/or having to use the volume control undesirably close to the bottom of its range.
I use the Denon AU-320 SUT with my Denon DL-103 cartridge that specs a 0.3mv output voltage. It's set at 1:10 step up ratio and works fine into my Audio Research SP8. When using a SUT a bit of experimentation and other folks results is quite useful as a guide. Most folks settle on a 1:10 ratio for the DL-103. Seems to work quite well. The AU-320 has two ratios, 1:10 and 1:36 with primary impedance of 40ohms and 3 ohms.When I get to Elliotts we can try both ratios but I suspect the 1:10 will work quite well. Simple flick of a switch. I would research and see what folks with that cartridge have settled on. It's the best place to start. BillWojo
I definitely got your point about not over doing it, for this or any cartridge, I was just imagining a variable transformer, and a bypass would be easy to do wouldn't it?
As far as I can recall my Lionel transformer didn’t hum :-)
Also, while I’m not certain I believe that in at least most of the models made in the 1950s or thereabouts those "transformers" were actually autoformers. Meaning that they just had one winding, rather than separate primary and secondary windings, with a sliding tap on that winding to control the output voltage. The maximum setting being mechanically limited to result in a safe voltage.
20x would be a good choice for your 0.3mV 10 ohms cartridge, as well outlined previously. If you want a versatile SUT for other MC cartridges, then the Bob’s Devices Sky SUTs come with 2 gain settings. So either a Sky 30x/15x or a 40x/20x would be extremely versatile. I have a Sky 20/10 and Sky 40 myself; they’re exceedingly nice sounding boxes that work equally great with different cartridge makes.
You do have to watch out for MC cartridges that have a high coil impedance relative to a low output level. These can be trickier to match with a SUT since the higher ratios you’d normally use to bring up the low signal level will end up loading the coils down too heavily, which results in a significant loss of signal (i.e. you’re spinning your wheels or worse by going to higher SUT ratios). One example of this would be a Benz Ruby, with 38 ohm coils to 0.35 mV output (3 - 10 ohms is more typical at this output level). If you hook that Benz into a 40x you’ll lose over 7 dB of signal from loading down the coils (20dB * log(29 ohms / (29 + 38 ohms)), where 29 ohms comes from 47,000 / 40 / 40) - in effect, the net output is more like what you’d expect from a 15x SUT, and likely with other significant sonic aberrations to boot. However 40x on a 0.3 mV, 5 ohm Koetsu (which I’ve used) works just great. You could however counteract this issue with an MM stage that allows input loading settings above 47,000 ohms - which unfortunately is probably less common than it should be.
On the other side of the spectrum is the Air Tight / My Sonic Lab cartridges, which have a very low coil impedance relative to their output levels.
• Low Impedance / High Ratio (1:20): For lowest output cartridges like SPU, Lyra with an output voltage of less than 0,3 mV
• Medium Impedance / Medium Ratio (1:15): If asked for a universal "one size fits all" step-up transformer we would recommend this configuration for cartridge impedances up to 20 ohms and output levels between 0,2 and 0,5 mV
• High Impedance / Low Ratio (1:10): For cartridges with an output level of more than 0,3 mV like EMT TSD
Enclosure dimensions 4.75" dia x 6" height, weight 6 lbs. Available in black or silver finish.
Long before I started representing Music First Audio and Audio Note I gave up on fully active amplification of the tiny signal from a MC cartridge. I have compared many, many preamps, phono preamps and step-ups. Most step-up transformers do indeed sound compressed. Most fully active MC phono preamps do indeed sound "electronic". But the best transformer step-ups into a MM phono stage have sounded much better, to me, in every way compared to the best active head-amps or MC capable phono preamps.
Now that I carry transformer step-ups from both Music First Audio and Audio Note (and MM-only phono preamps from both), it has been very easy for me to demonstrate this. I have a very nice MC-capable Krell preamp, that sounds better with any of these step-up transformers into its 47000-Ohm MM input. And, I encourage anyone who is interested to borrow one of my demo step-ups, to try in their own home, and find out for themselves.
The answer to your question, in my opinion, is yes. Listen to your MC cartridge, into the MM input with a good step-up transformer that is matched properly to the cartridge. If you tell me what cartridge you have, its output impedance (or coil resistance), and output mV, I can tell you what range of step-up ratio will work well for you. ............................. later he added
So the most versatile approach is to try a 1:20 transformer which has a provision for adding loading resistors, or is adjustable with built-in resistors. The next best solution is to compare more than one transformer, within a step-up ratio range between 1:30 and 1:20.
I think I am getting this, lemme know if I got it wrong
i'm just doing some math to learn the formulas
of course when you know this stuff it's intuitive
......................
Impedance change factor is square of amount of transformer boost 47,000 (typical MM phono input) 47,000 divide by change factor = resultant actual impedance ...........................
"
The recommendation of Rothwell Audio Products is in line with Ortofon, Audio Technica and most other cartridge manufacturers - that 100 ohms is a good value for most cartridges, and that the exact value is not critical as long as it is well above the cartridge's source impedance." ...................................
signal strength: enough, but avoid too high, say 5mv max (easy math) impedance is what effects the sound too low = dull. too high = too bright ......................................
AT33PTG/2 is .3mv and coil 10 ohm impedance coil 10 ohm x 10 = 100 ohm goal (average) ......................................
working backwards from desired impedance average of 100
47,000 divided by 100 = 470. 470 is square of 21.5 (boost factor found working backwards) .3mv cartridge x 21.5 = 6.45mv = TOO HIGH SIGNAL STRENGTH ............................
lower the signal strength means lower the boost means impedance goes up, just don't go up too much
IF desired max signal 5mv divided by .3mv = 16.7 signal boost. 16.7 squared is 279 47,000 divided by 279 is 168 ohms resultant impedance, not bad! ..................................... typical boost 10x or 20x, not 16.7 unless custom built.
.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!!! ........................................
Resistors, parallel with Transformer's secondary are a method of adjusting the impedance
that denon au-320 has the 2 inputs and pass, but I would use only 1 input for rear tonearm’s cable: 3 or 40 setting for MC, and use the PASS for my any MM, typically my MONO, correct?
it shows 3 ohm and 40 ohm, how do I translate that into gain factor?
In a word, no. Re-read Almarg's post.Also, you are making this much more difficult than it needs to be.Start with the turns ratio of the SUT, which is another way of stating the boost in voltage it provides. A 1:10 SUT will boost voltage by 10X, in other words. The reflected impedance afforded by that or any SUT will be equal to the value of the input resistance of the phono stage (47K in the case of nearly all MM stages) divided by the square of the turns ratio (10^2 = 100). So, with a 1:10 SUT and a 47K resistor, your cartridge will "see" a 470 ohm nominal impedance. Since we know your cartridge has a 10 ohm internal resistance, you will be fine with a 1:10 SUT. The ratio 470/10 = 47, is way higher than the minimum goal of 10X. There is no problem with having a ratio of these parameters that is >>10. With your cartridge, you can also use a 1:20 SUT; the same 47K ohm input resistor is then seen by the cartridge as 47K/400 = ~117 ohms, which is still more than 10X the internal resistance of your cartridge. In your final paragraph, you seem to be asking what happens when you parallel 100K with 47K. I don't know where you got that idea, but maybe someone else talked about REPLACING the 47K ohm input resistor with 100K ohm (not paralleling the two resistors; replacing one with the other). This is a little trick that one can do if one wants to use a particular SUT with a turns ratio that is not compatible with the internal resistance of a cartridge that has a relatively high internal resistance (e.g., >30 ohms) but a low output voltage. For example, do the math for using a 1:20 SUT with a cartridge having a 20-ohm internal resistance; you'd want to use a 100K ohm resistor on the phono input side to achieve the desired minimum ratio of cartridge output to phono input resistances. With your cartridge, you don't have to think about doing that. You can use 1:10 or 1:20, and there is absolutely no reason to wish you could fine tune the turns ratio between those two choices. I don't want to confuse you further, but the 10X rule is "soft". You can even get away with ratios a bit lower than 10X but not much lower. For now, think of it as a hard rule.
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).
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!!!
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)
this fidelity research FRT-4 is quite versatile don’t anybody buy it, I might buy my 75th birthday gift 3 years early.
I certainly won’t be buying it :-)
Even if I needed it, which I don’t, personally I would not purchase from a seller who ...
-- has more than 3300 items listed for sale at eBay, very few of which have anything to do with audio. (His "store" states that "we mainly sell Japanese figures, apparel and daily goods");
-- lists this 40+ year old item without providing any indication of whether it has been tested and found to work;
-- has more than 2% negatives among his nearly 1000 feedback ratings in the past 12 months;
-- and is overseas, which might make returning it and obtaining a refund problematical should that be necessary. At the very least you would have to pay return shipping costs, per the stated terms.
I don’t know of any SUTs which provide a bypass function, although perhaps there are some.
The Denon au-320 most definitely has a straight through bypass option as I have told Elliot in previous threads.
I used mine to run a 0.24mv ZYX into input 1 running at the 1;10 setting and input 2 had a regular MM cart running through it on the bypass selection when in use. Both worked perfectly well to my ears running into a Manley Chinook (amongst other stages) set at 47k and 60db gain. And by that I mean QUIET! I liked the flexibility of having two SUT in one AND a bypass option, gave a lot of options re cartridge choices. Oh and I liked the prices of used AU-320 units! So the 0.3mv should be perfectly fine at 1;10 into the mx phono.
What a complex exchange for a relatively straight forward issue. Look up the Black Swan, fully front panel continuously adjustable loading and gain, tweak it by what I call earball, set all the variables while listening to it.
thanks, I'll check it out. I get the earball thing, now that I realize what it's all about.
I've resisted even mouthing the words Moving Coil since they needed humming boosters when I was young, it is all new to me. I enjoy learning, and sharing my finds with 'imagined' others.
I'm a retired Interior Designer, specialized in Corporate Headquarters: New, Relocations, Renovations. Interior Architect actually, as practiced in NYC, PA, Wash DC, traveled hither and thither. I became more informed bit by bit progressively for 50 years. I researched everything, designed much custom work, selecting, presenting options to my clients, ordering a gazillion things. Select and present a full line of chairs, mail room to President's office, for a new 250,000 sq ft headquarters project, it's exhausting. I was not going to tell a client 'this is the best choice', and find something 'better' that I didn't know about a week later.
Now, for myself, i.e. that Fidelity Research FR-4. It truly appeals to me, and it did not pop up in my search until after a lot of searching. No one mentioned it. New, it's features and quality, would cost ___? It's hard for me not to 'add to cart' and put this search to bed.
You may want to do some reading here. I think it will help answer many of your questions, and answers to your questions, about cartridges and SUT. Lots of great info on all things hi fi.
I went thru all the notes, every recommendation, every one I found. I couldn't put myself or you thru any more research. I got mail to open, bills to pay today deadline!
Except for the new Russian Blackbird 12.5" tonearm, my main Denon T81 TT, rear Acos arm (where this new MC cartridge will alternate with Mono MM), and new to me office Vertical TT LT-5V, and my Teac X2000r Reel to Reels are vintage. Speakers in my office are vintage B&W bookshelf with vintage Velodyne 12" powered sub-woofer. Can Carver 400t Cube Amp be considered Vintage? If not, I’ll haul my shop Tandberg 2080 Receiver up here. Not to forget, mx110z downstairs is awesome vintage tube tuner/preamp.
looked up the Carver cube, 1981, 39 years old, I think it qualifies as vintage, but it looks as modern today as it did in 1981. I’ve been careful with it’s cheap speaker clips, but it’s doing a very nice job in my office. No power switch, no vol or balance, just On when plugged in. Separate control needed to turn it off, or unplug it.
I’ve got his AM/FM Tuner also, same modern look. Technically amazing, but the mx110z tuner’s tube sound beats it easily. mx110z needs a good signal, I put a separate TV/FM antenna in attic aimed directly at WBGO Jazz. Someone here (my memory sucks, sorry I can't remember whom) pointed out their antenna is actually in NYC. I found it online, happily my aim goes over Newark to the antenna there. Their signal is improved but still sucks. My Volvo C70's crappy antenna isn't good enough. Oh well, public radio.
Sirius XM has the "Real Jazz" channel, which I find to be a Godsend when I am poking around in my car hundreds of miles from home. The "Sinatra" channel is excellent also. So far I've resisted the impulse to acquire a Sirius XM receiver for my home audio system, but it actually makes some sense.
Take a look at the jensen transformers, tavish design uses them in their Adagio phono amp. And just to add, my hana el likes 400 ohms or better, 100 ohms sounded dull to my ears....
you mead to use in the DIY box?. I realized, even if I did that, I wouldn’t have the versatility of the Vintage Fidelity Research FRT-4 I ordered which is coming slowly from Japan: MM bypass, 4 load choices, 3 inputs.
four resultant loads for this AT33PTG/2 10 ohm cartridge: 107; 140; 360; 419
This is my first MC, Bill’s Denon SUT and another of his SUT’s will also be here to compare.
I never thought your comment was anything but logical concern, certainly not a mistake. When I thank the forum, you are high on the list of helping members.
Once again, I learned everything I needed here to make an informed choice.
Not everyone takes the risks I do with vintage stuff, I am more careful than is apparent, and take the long view, if a THING is a problem, it should be the biggest problem in my life.
In this case, returns accepted, it was minimal risk for an extremely versatile unit with presumed quality, and settings closely bracketing the 'formula ideal' of my specific cartridge, and future options. Luckily, I have never had to return anything except new stuff, which encourages more vintage risk.
I am very happy to report the Fidelity Research FRT-4 unit arrived from Japan in 6 days, and is absolutely invisible audibly, except what it does, and the subtle differences when you alter the input settings as you experienced MC people know.
Hooked it up last night, and played my Father's Day prize from my son, 'Best of Sade' Double LP, and heard MC cartridge in my system for the first time. New AT33PTG-II, .3mv; 10 ohm, MicroLine on boron.
It sounded fantastic. Bill is forgiven for pushing me down this rabbit hole I refused to look down for so many years. All the MC boosters I heard on Stereo Row in NYC many years ago had hum, I had no idea how silent good ones are. And, let's face it, MC is an expensive road.
First listen I preferred the 10 ohm/118 ohm setting rather than the 30 ohm/148 ohm setting, however, the slight volume difference undoubtedly influenced my initial impression.
Today comparisons to my MM Shure V15Vxmr body with Jico SAS on boron, and equal volume comparisons. btw, I'm not using the Jico brush any more, it sounds better without it. The real dampened brush of Shure OEM stylus never sounded different like this one does.
The big risk was that 'no return' tonearm from Russia, whew, took me months of desire before I went for it. I had eBay/PayPal protection, and I bought a 3 year warranty from Square Trade (discussed it was singular from Russia with Sq. Trade first). Very tricky install, but paid off. Wanted long, got 12.5" effective Carbon arm.
The MC is on the vintage Acos Lustre GST-801 magnetic adjustable arm, I think you were instrumental helping me decide and get it.
You must have a verified phone number and physical address in order to post in the Audiogon Forums. Please return to Audiogon.com and complete this step. If you have any questions please contact Support.
