Stepups and MC cartridges
Seb
The secrets of a successful marriage
Part 1
Please note: I wrote this little guide using the small amount of knowledge I've accumulated until now. I don't consider myself a master in electronics. In fact, I understand nothing of that subject. Some of you may find that I’m using some inappropriate terms. The aim of this paper is to understand the way stepup transformers function, and the rules you should follow to select the appropriate stepup to use with your MC cartridge (if you want to obtain a happy marriage).
Now, things are complicated by the fact that I’m French and even if Jas took a very close look to this text, some translation problem may have occurred. You’ve been warned! I would like to thank Jas, for his proof reading and Emile and Mambojet of the LS35a forum for their correcting of the first French version of this paper. All errors remain mine.
MM (moving magnet) cartridge, it’s very simple: you plug it into the MM entry of your amplifier and listen.
MC (moving coil) cartridge, it’s more complicated. The characteristics you should take care of for this kind of cartridge to be correctly exploited by your system are:
 The output level, measured in millivolts
 The internal impedance, measured in ohms
 The load impedance, measured in ohms too
In this paper, we’ll ignore high output MC cartridges that can be used with a MM input and concentrate on MC cartridges with an output of less than 1 mV. (The output level of MM cartridges is between 2.5 and 7 mV).
The job of a stepup transformer is to raise the output of the MC cartridge in order for that output to be correctly handled by a MM phono section. At the same time, the stepup transformer adapts the impedance of the signal produced by the MC cartridge to an impedance that can be “read” by your MM input. You must understand that stepups all have different characteristics that we’re about to explore. These characteristics are such that if you select a stepup and a MC cartridge at random, your probability of obtaining a happy marriage is close to zero.
So please, don't make a definitive judgment of a stepup or a MC cartridge. Before saying “this stepup is pure BS” or ”this cartridge is pure BS”, check the compatibility of your MC / stepup combo. Most of the time, if the sound isn't good it’s because of a compatibility problem.
So, you need to amplify the signal output from a MC cartridge? In fact, you use can two different kind of devices to do that job:
active devices : head amplifier of MC section on a phono section
passive devices : stepup
How can you tell that a device is active or passive? Very simple, on active devices, there is a plug! On stepup, no plug (so, it’s passive since there is no power supply).
Another difference, that makes things unclear for a newbie, is that on active devices the load impedance is indicated (100 ohms, for instance), on passive devices you don’t have a load impedance but an internal impedance; rather than a manufacturer giving a load impedance figure you will get a statement such as: “this stepup is designed for use with cartridges with an internal impedance of 40 ohms". We’ll ignore active devices. There is no fun there; cartridge manufacturers generally specify a load impedance, so you set up your active device (head amp, MC phono section) to that load impedance and listen; game over.
By reading this paper you will find that some cartridges cannot be used with a stepup, whatever its characteristics. For these cartridges you’ll have to use an active device.
Now, on a stepup you’ll find internal impedances indicated: for instance, take a look at a DENON AU320, two positions are possible: 3 ohms and 40 ohms. So this stepup should be good with cartridges of internal impedance of 3 ohms and 40 ohms. Now the problem is, that for the moment, the load impedance used in that stepup is not known (but we’ll soon know this very important information!). We’re only sure that this load impedance is superior to the internal impedance. And secondly, the load impedance given by a manufacturer for its cartridge is the one you should use on active devices; the one you should use on passive devices is not generally the same and is superior to the load impedance given by the manufacturer.
How can you tell that the impedance indicated on a stepup is not the load impedance?
Let’s do some calculus! If a stepup has a gain of say 1:10, this means that the output of the cartridge will be multiplied by 10. If the output out of the cartridge is 0.3 mV, you’ll have, after the stepup, 3 mV, perfect for a MM input. Now, your MM input has its own impedance generally equal to 47 Kohms. The signal emitted by the MC cartridge must be in accordance to that 47 Kohms. A stepup modifies the impedance of the output by a factor equal to the square of the amplification ratio. This is known as ‘natural impedance’. A word of caution: by itself, a stepup doesn’t have any impedance. The natural impedance is directly linked to the impedance of your MM entry and to the amplification ratio.
So, a stepup with an amplification ratio of 10 has a natural impedance and load impedance of 470 ohms (if your MM input impedance is 47 kohms: 470=47000/10²). Now, let’s go back to our DENON AU320: on the 40 ohms position, since the amplification ratio is 1:10, the load impedance is 470 ohms.
You’re not convinced? Let’s do more calculus. If your load impedance was 40 ohms, your amplification ratio, in that case should be equal to (47000/40)^0.5 = 34.3. With a cartridge output of 0.3 mV, you are sending 0.3*34.3 = 10.28 mV to your MM input. This is important; you may be overloading your MM input. Let’s do the same calculus on the 3 ohms setting. If it were your load impedance, the gain in that case should be (47000/3)^0.5=125.16. Again, with a 0.3 mV output cartridge, you’re about to send 37.5 mV in your MM input: this IS overload! A MM input is generally designed to accept an output between say 2.5 and 10 mV, not 37.5 mV! And the amplification ratios calculated here have nothing in common with the stepup specs given by manufacturers (as we’ll see in a few moments).
Come on! You forgot to talk about “resistor tuning”!
Don’t worry, I’ll talk about resistor tuning in a few moments. But, as an introduction, understand that there is a way to reduce the load impedance by adding resistors inside the stepup. This is not the way manufacturers did it. In fact, a stepup looks like this (drawing taken from an audio technical manual):
No resistors here. You can do some reverse engineering by dismantling your stepup: you won’t see any resistors unless you have an Ortofon T30 (among the stepups examined in my table, I believe this stepup is the only one with resistors)
That scheme is really interesting, please tell us more!!!
My pleasure! So, for one channel, there are two coils: a primary (the ‘input’: the signal emitted by the cartridge arrives at this one) and a secondary (the ‘ouput’: the amplified signal will go out to your MM amplifier stage from this one). You will see that there are less turns on the secondary than on the primary. This is not a strange idea from the designer of this scheme. Your amplification ratio is a direct result of the turns ratio (primary/secondary) (ok, I know, I know, a perfect transformer doesn’t exist and things are not that simple but the rule indicated here is a good proxy). This explains why, on a stepup that can be used with several internal impedances cartridges, the gain differs according to the internal impedance you’re selecting. On the audio technica stepup represented by the scheme, the gains are 23, 26 and 34 db for respective internal impedances of 40, 20 and 3 ohms.
In a perfect transformer: N2/N1 = V2/V1 = x
Where:  N2(1) : number of turns of the secondary (primary) V2(1) : output out of the stepup (in) x : amplification ratio 
And  Z2/Z1 = N2²/N1² = x² 
Where:  Z2(1): impedance of the secondary (primary) 
Another « detail »: the grounding of the stepup. This is very important. If you’re having grounding problems, or shielding problems, you’ll probably have “hum”.
But, why are only internal impedances indicated on a stepup?
The main reason is certainly the fact that, as I already indicate, natural impedances are not constant: they are a function of the impedance of your MM input. For instance, if your MM input has a 10 Kohms impedance, with a 1:10 amplification ratio stepup, the natural impedance (and your load impedance) is 100 ohms (10000/10^2).
What stepup for my cartridge?
This is THE question. If you’re looking for a stepup you can buy second hand stepup transformers, brand new (most Mc cartridge manufacturers produce stepup transformers) or build them yourself using parts from manufacturers like Lundhal, Sowtek, Hashimoto, Jensen.. (See links to those manufacturers at the end of this paper).
To make things clearer, we’re going to take a look at the specifications of available products. Why? Because these products were designed by MC manufacturers, let’s assume that they knew what they where doing. Specs shown here are compiled from various sources (internet or vinylengine inmates like Yosh (Hi Yosh!). if you have data relating to other products, contact me and I’ll add them to the table. All I need to know is the gain (measured in db or in amplification factor 1:x) and the recommended internal impedance of the cartridges to use with that stepup.
Data in bold type are manufacturers specs, other data was recalculated this way:
X factor = 10^[(gain in db)/20]
Gain in db = 20*ln(x factor)/ln(10)
Natural impedance = 47000/[(x factor)^2]
Manufacturer  Model  Gain in db  x factor  Natural impedance  Recommended Impedance 
Ortofon  T5  26  20,0  118,1  340 ohms 
T10  32  39,8  29,7  24 ohms  
T10 MK2  28  25,1  74,5  26 ohms  
T20  32  39,8  29,7  24 ohms  
T20MKII  28  25,1  74,5  26 ohms  
T30  20  10,0  470,0  2448 ohms*  
29  28,2  59,2  612 ohms*  
32  39,8  29,7  5  
SPUT100  26  20,0  118,1  16 ohms  
T1000  26  20,0  118,1  26 ohms  
T2000  35  56,2  14,9  3  
T3000  30  31,6  47,0  210 ohms  
Fidelity Research  FRT4  31  35,5  37,3  3 
26  20,0  118,1  10  
25  17,8  148,6  30  
20  10,0  470,0  100  
FR XF1  30  31,6  47,0  418 ohms  
FRT3  26  20,0  118,1  30  
31  35,5  37,3  10  
XG5  34  50,1  18,7  < 3 ohms  
26  20,0  118,1  318 ohms  
22  12,6  296,5  1840  
X1M  30  31,6  47,0  418 ohms  
X1H  25  17,8  148,6  1940 ohms  
X1L  36  63,1  11,8  3  
Denon  AU 320  31,1  36  36  3 
20,0  10  470  40  
AU 340  30,4  33  43  3  
20,0  10  470  40  
AU310  20,0  10  470  40  
AUS1  22,3  13  278  340 ohms  
AU300LC  20,0  10  470  40  
Audio Technica  AT700T  34  50,1  18,7  3 
26  20,0  118,1  20  
23  14,1  235,6  40  
EAR  MC4  29,5  30  52,2  3 
27,6  24  81,6  6  
25,1  18  145,1  12  
20,0  10  470,0  40  
MC3  29,5  30  52  4  
26,0  20  118  12  
20,0  10  470  40  
Supex  SDT 3300  28,5  26,6  66,4  210 ohms 
Bryston  TF1  22,5  13,3  264,3  535 ohms 
16,5  6,7  1052,2  40250 ohms  
Rothwell  rothwell  22,0  12,6  296,5  < 40 ohms 
Nakamichi  MCB100  26,0  20  117,5  220 ohms 
Sony  HAT110  26  20  117,5  3  40 ohms 
* ortofon T30 : the natural impedance is certainly used for 48 and 12 ohms position and is reduced by “resistor tuning” – if someone here can read the value of the resistors inside the T30, that could help us a lot!
Part 2
What is there to understand here?
Let’s imagine I have a 3 ohms internal impedance cartridge. What are the devices I should buy?
Some devices from this table have a 3 ohms setting: FRT4, Denon AU 320, Denon AU 340, AT700T, Ortofon T2000, FRX1L, EAR MC4. What we can see is that the natural impedance of these devices (respectively 37,3  36  43  18,7 – 14.9 – 11.8 and 52,2 ohms) can be separated in two groups: Some of them have very low natural impedance (between 11.8 and 18.7 ohms). I think these figures are really too low and will limit this kind of stepup for use with very low internal impedance cartridges (12 ohms) especially the Ortofon T 2000. The remaining stepups have a natural impedance between 36 and 52.2 ohms.
We will consider this range as a good range for loading a 3 ohms internal impedance MC cartridge. The amplification ratios associated with these stepups are between 30 and 36 (gain is between 29.5 and 31 db).
Now, there are some other stepups in my table that have a natural impedance between 36 and 52 ohms: EAR MC3 (4 ohms position), Ortofon T3000 (210 ohms position), FR XF1 (418 ohms position), FR X1M (418 ohms position), FRT3 (10 ohms position). Conclusion: you can use that stepup at the position indicated with your 3 ohms cartridge.
One could add to this list the Ortofon T10, T20 and T30. The natural impedance is equal to 30 ohms (a little low for me – I would couple those transformers with very low impedance cartridges of say 1  2 ohms). On one hand you could say “come one, this is Ortofon, worldwide specialist of low impedance cartridges, they know what they doing”. But on the other hand I must add a very important point to understand why Ortofon may have changed their minds. These models are rather old (70’s 80’s). It seems that manufacturers realised in the 80’s that designing a high gain stepup transformer is really difficult. The more gain you have, the more difficult it is to have a flat frequency response. The difficulty of producing a quality high gain stepup with a linear response is translated in the actual price of these stepups: for instance, the price of an Ortofon T3000 is 1625 euros (are you sure you really want to buy a low impedance cartridge?)
But, from this table, you can find some other transformers that are said to treat correctly a 3 ohms internal impedance cartridge. In fact, for these transformers, manufacturers provide a range of possible internal impedances for the transformers.
Things are now a little more complicated and one could ask if we can really trust the manufacturers’ recommendations? Let’s take a look at the Denon AUS1, Ortofon SPUT100, Ortofon T1000, FR XG5, Ortofon T5, Nakamichi MCB100, Sony HAT110, Ortofon T20MKII, Ortofon T10 MK2 and Supex SDT 3300.
The natural impedance for these transformers is between 66.4 ohms (Supex SDT 3300) and 278 ohms (Denon AUS1) : there must be a problem for the Denon unit. A 3 ohms internal cartridge plugged into a Denon AUS1 is certainly producing very amplified highs. So, when a range is indicated for your stepup, there is always some kind of compromise since they cannot be good everywhere. The risk is to have a too high a load impedance for a cartridge with an internal impedance equal to the minimum of the range (too bright sounding) or too low a load impedance for a cartridge with an internal impedance equal to the maximum of the range (no high frequencies in this case).
The Denon AUS1 should work well with a 40 ohms internal impedance cartridge but no good with a 3 ohms internal impedance cartridge. The Ortofon T5 might not work very well with a 40 ohms internal impedance cartridge or a 3 ohms internal impedance cartridge, but may be good with say, a 10 ohms internal impedance cartridge. Let’s take a look now at what is proposed for 40 ohms internal impedance cartridges: there is a consensus on a natural impedance of 470 ohms (biased by the fact that we’re having a lot of Denon products in the table). Now, from the table, you can see that the FRT4 (100 ohms position) and the Ortofon T30 (48 ohms position) will give you the same natural impedance. With transformers proposing a range of internal impedance including 40 ohms, the natural impedance is generally lower, from 118 ohms (Sony HAT110, Ortofon T5) to 296 ohms (FR XG5) – for the Briston TF1, 40 ohms is the minimum of the range : the natural impedance (and then the load impedance) is much to high (1052 ohms).
Let’s assume that the loading of a MC cartridge with a transformer is not an exact science.
Loading a MC cartridge is not an exact science? Why? Simply because manufacturers never produce a unique load impedance for a given internal impedance and because, for a given natural impedance, there is frequently a range of internal impedances that suit the transformer. Now, for a given internal impedance, we should propose a range of load impedance. What I’m proposing now is just a starting point – by following my rules, I’m not telling you that you will obtain the perfect load impedance, I’m just telling you that you won’t make stupid mistakes.
So please, don’t contact me to insult me about my rule!
For this rule, we’ll use a spec given by the manufacturer: the load impedance. We’ll take this load impedance as meaning a load impedance recommended for active transformers (and not for passive devices). This data certainly includes things relavent to important characteristics of the cartridge we don’t know, but that must be considered.
A manufacturer generally gives you a minimum load impedance for active devices (or a range, but it’s less common).
If the load impedance (for active devices) is said to be > or equal to 20 ohms, the internal impedance is 3 ohms, you should try to load your cartridge at load impedances between:
 the load impedance given by the manufacturer (20 ohms)
 the load impedance given by the manufacturer + 10*internal impedance (50 ohms)
Now, for a 40 ohms internal impedance cartridge with load impedance for active devices of 100 ohms, you should try load impedances between 100 and 500 ohms. If your system is too bright (suppose you’re having triangle loudspeakers…), you will certainly be happy with something that will “cool down” your sound, so try something close to 100 ohms. On the contrary, you may be happier with something closer to 500 ohms.
Now, my opinion: I never hear satisfactory results when the load impedance on a passive device is equal to the load impedance indicated by the manufacturer (we understand as load impedance on an active device). You’ll try and you’ll tell me. We’ll see later the way to test different load impedances but you don’t need to test 100 values between 100 and 500 ohms : something like 3 or 4 value is enough and in our case, you could try 100 ohms (and you’ll tell me), 200 ohms, 300 ohms and 470 ohms (with a 1:10 transformer).
If the manufacturer is proposing a range of load impedance (say between 20 and 200 ohms), follow that range by testing say, 50 ohms, 100 ohms and 150 ohms.
Do you think things are over? No, they aren’t! The load impedance is an important thing BUT it’s only the first important thing to consider. Remember that the natural impedance is directly linked to the gain of your stepup. In the next table, you will see the maximum gain of your stepup to have a desired load impedance.
TABLE 1: Load impedance and maximum gain of the stepup
Impedance of the phono stage : 47000 ohms


How to use this table? Suppose you would like to test load impedances of 470, 300 and 200 ohms. Take the higher load impedance (470 ohms) and check the table. You now know that you’ll need a 1:10 stepup (a stepup with a gain of 20 dB). For load impedances of 300 and 200 ohms, see the resistor tuning section of this paper.
Things aren’t over! No, they aren’t!
We have not considered an important spec of your cartridge: its output level. You should not forget that the first objective of the stepup is to amplify the low signal coming for your cartridge to make that signal compatible with a MM input.
Jensen, on their website, states that the output, once amplified, must be between 2.5mv and 10mv to be handled correctly by a standard MM input. We’ll use this rule as a good starting rule. If the signal is too low, we’ll have to turn up your volume knob too high (and you’ll hear the noises coming from your amp), if it’s too high, you’ll overload your MM input. There is another difficulty here: the output level should not be considered as a constant. It seems (but someone will certainly be able to explain this better than me) that the output level is affected by your load impedance: the closer you are from the internal impedance, the lower your output will be – this phenomenon is the one that explains the under amplification / over amplification of high frequencies (now, it’s hard for me to be more precise – if someone is able to explain this in simple terms, he’s welcome!).
In the next table, you can observe as a function of the gain of your stepup, ranges of output levels coming from the MC cartridge that will let you to stay between 2.5 mV and 10 mV at the MM entry level.
Table 2: stepup gain – minimum and maximum output of the MC cartridge
Gain in dB  x factor  Min output (mV)  Max output (mV) 
14  5  0,50  2,00 
15  6  0,44  1,78 
16  6  0,40  1,58 
17  7  0,35  1,41 
18  8  0,31  1,26 
19  9  0,28  1,12 
20  10  0,25  1,00 
21  11  0,22  0,89 
22  13  0,20  0,79 
23  14  0,18  0,71 
24  16  0,16  0,63 
25  18  0,14  0,56 
26  20  0,13  0,50 
27  22  0,11  0,45 
28  25  0,10  0,40 
29  28  0,09  0,35 
30  32  0,08  0,32 
31  35  0,07  0,28 
32  40  0,06  0,25 
33  45  0,06  0,22 
34  50  0,05  0,20 
35  56  0,04  0,18 
36  63  0,04  0,16 
37  71  0,04  0,14 
Things become complicated: as we say in France, you’re running after two hares at the same time (and we’ll add two more hares in a few moments):
 you must have a correct load impedance
 you must have a sufficient gain
For some cartridges, it’s mission impossible! An example? The Denon DL1000A: the output is 0.12 mV, the internal impedance is 33 ohms, the load impedance is 100 ohms so, following the rules, you feel that this cartridge should be comfortable with say, 300 ohms.
To obtain 2.5 mV, the gain of the stepup must be, at minimum, 1:20 but with that kind of stepup, the natural impedance is 118.1 ohms: it’s lower than the desired value of 300 ohms! No passive device for this cartridge (in my opinion): find an active device!
Some cases are more interesting. For instance, let’s consider the Ortofon MC30 supreme: the internal impedance is 5 ohms, the load impedance is superior or equal to 20 ohms, and the output is 0.5 mV. Following the rule, you must try load impedances between 20 and 70 ohms.
If I only consider the load impedance criteria and by taking a look at the table 1, I’m about to order a 1:26 stepup. Now, 26*0.5mV = 13mV = overload!
“I’m about to have a nervous breakdown!” Come on! Resistor tuning will save you!
No, you don’t have to add large tyres on your turntable! Resistor tuning is a way to modify (to lower) the load impedance directly linked to the gain of your stepup transformer.
You can lower the load impedance by adding a resistor (in fact two: remember, stereo!) between the + and the – of the RCA plug (out of the stepup).
Suppose you have a 1:10 gain stepup. Your actual load impedance is 470 ohms (natural impedance). You would like to test a load impedance of 100 ohms. Let’s now calculate the value of the resistors you should add:
In fact, by adding resistors, you’re modifying the impedance of the MM entry (actually equal to 47 000 ohms  standard). To have a load impedance of 100 ohms, you need to have an MM entry impedance of 10 000 ohms (remember 10000/10^2=100).
First thing to do is to calculate the desired impedance for your MM input before calculating the value of the resistors you’ll need. Use this formula:
Wanted_IMP = (xgain)^2*(wanted_load_imp)
Now to calculate the value of the two resistors you need in our case:
Rload = 1/(1/100001/47000) = 12.7 Kohms
Generally: Rload = 1/(1/R1 – 1/R2)
Where: R1 is the impedance you want for your MM input and R2 is the actual impedance of your MM input
Let’s go back to our Ortofon MC30 supreme. With its output of 0.5 mV, I say to myself: I would like to obtain 5 mV in my MM input, so I need a 1:10 transformer.
Now, the load impedance. I would like to have a load impedance of say 40 ohms (here, the brainy guy will try different load impedances between 20 and 70 ohms, will buy several pairs of resistors to test those values and will only keep the pair that suit him the best).
With a gain of 1:10, I need an impedance of 4000 ohms on my MM input (10^2*40). The resistors I should buy must have a value equal to:
Rload = 1/(1/40001/47000) = 4372 ohms
For that cartridge, resistor tuning is very useful: you can obtain the desired load impedance with a 1:10 gain stepup. And now you remember that, the higher the gain, the higher the probability of having distortion (or the higher the price you’ll have to pay for your transformer): a transformer with a gain of 1:10, it’s not a high gain transformer (and it’s quiet cheap! Hooray!)
I know, you’ve just started saying to yourself “come on, with that cartridge, I can use a stepup with a lower gain than that 1:10 gain – that we’ll be better”. Yes, but the answer to this question will be a function of the gain of you MM input (and of its sensibility – remember, you need a minimum of say (but take a look at the specs of your MM input) 2.5 mV).
Imagine that you can use a 1:5 gain stepup (Lundhal, I have one, Jensen is proposing a 1:4 – it’s one of the most expensive of its products...). With the Lundhal, 0.5 mV*5 will give you 2.5 mV. In that case, to obtain the 40 ohms load impedance, with a gain of 1:5, the impedance of your MM input must be 5^2*40 = 1000 and the value of resistors you should buy is:
Rload=1/(1/10001/47000) = 1021 ohms
WARNING: BUY ONLY HIGH QUALITY RESISTORS!!!
More resistor tuning?
You now understand that, with resistor tuning, you can lower the load impedance. But what if you need to raise that load impedance?
It’s possible but not much fun: you understand that you need to modify the load impedance of your MM input. Open you MM stage and, somewhere (things are more complicated for me at this level), you’ll see resistors, close to the RCA sockets that determine the impedance of your MM entry (47kohms resistors), remove those resistors and solder higher value resistors.
Now, if your intention is to do that kind of thing, I deeply recommend you find yourself a real expert! There are certainly some limits to this kind of operation.
One last! For the road!
Remember the two hares you’re running after? Let’s add another one: your cables (and their inductance). The cable you’re using between the stepup and the MM input must be as short as possible and its inductance must be really low! Inductance problems can modify the linearity of your frequency response and it’s a very important factor with MC cartridges.
For more details on that subject, see: http://www.hagtech.com/loading.html
Part 3
« I’m exhausted reading you, come on, give me a break! » Not yet and it’s not time for a conclusion!
Where is that fourth hare we must run after?
There is a little problem with resistor tuning. I insisted that you buy high quality resistors but remember that the best resistor is the one that remains in the store. So, be aware that using bad quality resistors may destroy your sound and that using high value resistors can do the same thing.
So, as a pre conclusion, let’s present the four hares you’re running after:
 you must have the correct load impedance
 you must deal correctly with the output of your cartridge
 use minimal resistor tuning (+ high quality resistors are necessary)
 use short / low inductance cables
Not that easy!
A final table, for the road!
To simplify things a little and to determinate more easily the kind of stepup you’ll need for your beloved cartridge, let’s try to understand this last table.
Table 3: output, load impedance, minimum and maximum gain
Output  0,05  0,1  0,15  0,2  0,25  0,3  0,35  0,4  0,45  0,5  
x factor min  50,0  25,0  16,7  12,5  10,0  8,3  7,1  6,3  5,6  5,0  
load imp  
10  68,6  E  68,6  E  50,0  *  37,5  *  30,0  *  25,0  *  21,4  *  18,8  *  16,7  *  15,0  * 
15  56,0  E  56,0  E  50,0  *  37,5  *  30,0  *  25,0  *  21,4  *  18,8  *  16,7  *  15,0  * 
20  48,5  E  48,5  E  37,5  *  30,0  *  25,0  *  21,4  *  18,8  *  16,7  *  15,0  *  
25  43,4  E  43,4  E  37,5  *  30,0  *  25,0  *  21,4  *  18,8  *  16,7  *  15,0  *  
30  39,6  E  39,6  E  37,5  *  30,0  *  25,0  *  21,4  *  18,8  *  16,7  *  15,0  *  
35  36,6  E  36,6  E  36,6  E  30,0  *  25,0  *  21,4  *  18,8  *  16,7  *  15,0  *  
40  34,3  E  34,3  E  34,3  E  30,0  *  25,0  *  21,4  *  18,8  *  16,7  *  15,0  *  
45  32,3  E  32,3  E  32,3  E  30,0  *  25,0  *  21,4  *  18,8  *  16,7  *  15,0  *  
50  30,7  E  30,7  E  30,7  E  30,0  *  25,0  *  21,4  *  18,8  *  16,7  *  15,0  *  
60  28,0  E  28,0  E  28,0  E  28,0  E  25,0  *  21,4  *  18,8  *  16,7  *  15,0  *  
70  25,9  E  25,9  E  25,9  E  25,9  E  25,0  *  21,4  *  18,8  *  16,7  *  15,0  *  
80  24,2  E  24,2  E  24,2  E  24,2  E  21,4  *  18,8  *  16,7  *  15,0  *  
90  22,9  E  22,9  E  22,9  E  22,9  E  21,4  *  18,8  *  16,7  *  15,0  *  
100  21,7  E  21,7  E  21,7  E  21,7  E  21,4  *  18,8  *  16,7  *  15,0  *  
120  19,8  E  19,8  E  19,8  E  19,8  E  19,8  E  18,8  *  16,7  *  15,0  *  
140  18,3  E  18,3  E  18,3  E  18,3  E  18,3  E  18,3  E  16,7  *  15,0  *  
160  17,1  E  17,1  E  17,1  E  17,1  E  17,1  E  17,1  E  16,7  *  15,0  *  
180  16,2  E  16,2  E  16,2  E  16,2  E  16,2  E  16,2  E  15,0  *  
200  15,3  E  15,3  E  15,3  E  15,3  E  15,3  E  15,3  E  15,0  *  
225  14,5  E  14,5  E  14,5  E  14,5  E  14,5  E  14,5  E  14,5  E  
250  13,7  E  13,7  E  13,7  E  13,7  E  13,7  E  13,7  E  13,7  E  
275  13,1  E  13,1  E  13,1  E  13,1  E  13,1  E  13,1  E  13,1  E  
300  12,5  E  12,5  E  12,5  E  12,5  E  12,5  E  12,5  E  12,5  E  
325  12,0  E  12,0  E  12,0  E  12,0  E  12,0  E  12,0  E  
350  11,6  E  11,6  E  11,6  E  11,6  E  11,6  E  11,6  E  
375  11,2  E  11,2  E  11,2  E  11,2  E  11,2  E  11,2  E  
400  10,8  E  10,8  E  10,8  E  10,8  E  10,8  E  10,8  E  
425  10,5  E  10,5  E  10,5  E  10,5  E  10,5  E  10,5  E  
450  10,2  E  10,2  E  10,2  E  10,2  E  10,2  E  10,2  E  
475  9,9  E  9,9  E  9,9  E  9,9  E  9,9  E  
500  9,7  E  9,7  E  9,7  E  9,7  E  9,7  E  
550  9,2  E  9,2  E  9,2  E  9,2  E  9,2  E  
600  8,9  E  8,9  E  8,9  E  8,9  E  8,9  E  
650  8,5  E  8,5  E  8,5  E  8,5  E  8,5  E  
700  8,2  E  8,2  E  8,2  E  8,2  E  
750  7,9  E  7,9  E  7,9  E  7,9  E  
800  7,7  E  7,7  E  7,7  E  7,7  E  
850  7,4  E  7,4  E  7,4  E  7,4  E  
900  7,2  E  7,2  E  7,2  E  7,2  E  
950  7,0  E  7,0  E  7,0  E  
1000  6,9  E  6,9  E  6,9  E  
1100  6,5  E  6,5  E  6,5  E  
1200  6,3  E  6,3  E  6,3  E  
1300  6,0  E  6,0  E  
1400  5,8  E  5,8  E  
1500  5,6  E  5,6  E  
1600  5,4  E  
1700  5,3  E  
1800  5,1  E  
1900  
2000 
Let explain the table: you have a MC cartridge with an output of 0.25 mV. You need a stepup with a minimum gain of 1:10 (to obtain 2.5 mV in your MM input)
The load impedance you would like to try will give you the maximum gain of your stepup. Suppose, you would like to try different values between 10 and 50 ohms, take the higher value and from the table, you’ll see that the maximum gain you could use is 1:30 (I consider here 7.5 mV as the maximum possible input to the MM stage – 10mV seems to me rather high…). The star, at the right of the 30, indicates that with a higher gain transformer, you will overload your MM entry. To modify the load impedance here (and reduce it), use resistor tuning.
If you want to load that cartridge at 375 ohms, the maximum gain must be equal in that case to 1:11.2. The ‘E’ at the right of the 11.2 indicates that if you choose a transformer with a higher gain, the load impedance will be necessarily lower than the desired value.
“Damned, at the crossing of the column that corresponds to the output of my cartridge and of the line that correspond to my desired load impedance, there is nothing! »
Sorry folks, if your MM input is a standard one (with no selectable gain, for instance), no stepup transformer for you! Use an active device (and you read the whole page for nothing – sorry).
Links
Sowter
provides help to choose the correct product you need for your cartridge
Jensen
provides a lot of information too!
Bent Audio proposes some very interesting explanations
K&K Audio
specialist in Lundhal transformers
K&K Audio forum
discussion forum
Hashimoto
used to produce transformers for Sansui: they’re proposing a very interesting stepup transformer for MC cartridges, theHM3 (and the guy is very nice!)
Comments
clarification
I'd just like to point out that the data in your table of transformers states that our transformer is recommended for cartridges with an impedance of 100 ohms. This is incorrect. Our transformer presents the cartridge with a load impedance of 100 ohms when used with MM phonostages with the standard 47k input impedance. What you refer to as the "natural impedance" of our transformer is 296 oums (as you say) but we use resistors to modify the load.
Also, I would like to point out that transformers need to work into a specific load impedance to work optimally with the widest frequency response and minimum ringing. For that reason, it is not a good idea to modify the load on the secondary of the transformer to change the load seen by the cartridge.
I will post a page on our website soon with further details about our transformers and how best to use them.
Andrew Rothwell
www.rothwellaudioproducts.co.uk
re:
many thanks for your clarification. The data about your product will be updated very soon.
This is a mistake.
Please apologize ;)
best regards
Seb
Rload
Dear Sir
IMO, using active devices, Rload should be around 10 x Cart internal impedance.
Your rule Rload = cart load impedance + 10x cart internal impedance puzzles me.
Would you explain your reasoning ?
Best regards
Ricardo Cruz
Hello Ricardo well, there is
Hello Ricardo
well, there is no complicated equation behind this recommendation... it is just based on my experience :
a good starting point is to consider, when using a passive device (a step up) a load impedance of :
load impedance recommended with active devices (generally given and most of the time, this is 100 ohms)+10*internal cartridge impedance.
I had rather good results with this rule even if, again, there is no "theory" behind that (and you'll find no theory that will explain what should be the gain (and the associated load impedance) to be associated to a given cartridge.
best regards
Seb
Fidelity Research FRT3
About this transformer 118.1 and 37.3 Ohm impedance at primary are indicated , assuming a 47KOhm secondary load. But inside FRT3 there are 16K2 resistors parallel to each secondary. Primary impedance correct values are therefore 33 Ohm and 10 Ohm (measured @1Khz with 47K external secondary load).
Sony HAT30 Mini stepup with Denon 103??
Can someone tell me if this is a good match and at what load impedance I should set my MM input? Tx, sven
Right On Speedyp!!
Thanks to speedyp for those 2 REALLY GREAT links. Info presented in a form that clarifies the whole subject and is presented in a language that I can understand!
Why step up at all?
The info presented in this article is certainly noteworthy, but instead of trying to understand all of that, why not just get the correct phono stage for the lowoutput MC cartridge to begin with?? It's not like there is a shortage of products out there the sky's the limit, so why would anyone need to "step up" at all? Thankyou.
marriages ?!?
It's an impressive set of figures but I don't think we should worry too much  there are so many other factors.
I depend on a BBC spec. PPM (Calrec 100 with Sifam 74a movement)to keep signals in check. Even with a limited range of 26dB it is very useful indeed. I don't think domestic users need be so pedantic: If it sounds right  it probably is !!