J2B's Moving Coil Step-up Transformer

Johnny2Bad

Johnny2Bad

Audioholic Chief
A while ago I posted a teaser in the "what have you bought lately" thread about a project I've been working on, a Moving Coil Phono Cartridge Step-up Transformer.

With Gene's gracious permission, I've been allowed to create a thread and, with some limits on what I can and can't say and do ... this will be a commercial product available for sale at some point during 2018, and normally such a thread isn't allowed.

So, starting with my original post, quoted below, I will periodically update the progress. (Click on the "view attachment" links to see photos of the populated PCB).

This might be against the forum rules, as it will eventually be a commercial product. To that end I have obscured some parts of the assembly so that the brand can't be read, and I'm not at this point offering any clues as to price point, where to buy (eventually), and so on. Hopefully that gives me the room to leave this up. This is the first and only forum where this will be posted.

If anyone has had the patience and curiosity to read my sig, they might have noticed the lines:
" ...
Under Evaluation:
...
Various Phono Preamp designs (DIY)
...
Currently developing a commercial Moving Coil Step-Up Transformer product.
..."

Well, the first prototype has been built, and it will be making the rounds for evaluation over the next few months. I'm excited about the whole project and just want to share. It is, technically ... some "new stuff that I've bought (for much more than just one copy is worth) and I do "care to share". That's all I will say as of now.

View attachment 23498 View attachment 23497
 
Johnny2Bad

Johnny2Bad

Audioholic Chief
There is a lot of things that come into play when you are looking at small-scale manufacturing versus a DIY project one-of for your own personal use. On one hand, when you purchase in quantity, you can lower the cost per unit. On the other, that means cash outlays that are significantly higher.

Some things are relatively inexpensive ... setting up a website, securing domain names, organizing your twitter and social media accounts, and product development and documentation when you do a lot of the grunt work yourself, at slave wages (in other words $0).

Other things are quite costly ... in order to get good pricing, you have to order parts in quantity. Things that would be un-necessary for a one-of, like product packaging so that whatever you are offering can arrive across continents in one piece need to be sorted out, and you can't usually buy just one cardboard box, you typically need to buy at least 50, sometimes more.

The net result is your upfront costs are quite significant. For my transformers, my minimum order is in the four figures, for example. PCBs at low quantity are quite expensive per-board; again the real price break doesn't normally happen there until you are ordering perhaps 50 copies. And so on.

Had I just wanted to make one for myself, I could have been all-in for a cost that is actually near my target retail price, boxed, shipped, and finished to a level at least consistent with the competition. A bare box with some connector and control indicators made on a label printer would have been fine; for a retail product that just won't do. As it is, my initial outlay is going to be equivalent to many DIY copies, even though I am getting some cost savings on a per-unit basis by buying parts in quantity.

I'm not complaining, just laying out some factors that, in the end, make up whatever profit per unit that can be reasonably made justifiable.

There is a standard "rule of thumb" in electronics manufacturing that the raw parts count will equal 20% of the retail price. My target price is nowhere near that ... I don't think I will even make a 50% ratio. Part of that is the direct-to-consumer marketing model, which shaves 30 to 40% (typically) off the final retail price. Without revealing exactly what the industry expects for a retail margin on this type of product, except to say that it's amongst the lower range, versus, say, accessories, there are additional costs that reduce the savings to the consumer somewhat. Put another way, I'm doing things that the retailer would otherwise take care of, and some of them cost money.

Still, in keeping with my philosophy in Audio that goes back to my days as a retailer, many years ago, I am a "value" kind of guy. People who read some of my posts might be a little surprised to read that ... but value does not necessarily equal "lowest price". It rarely does, actually. But in Audio there are certain thresholds where, once you spend X dollars, you get tremendous performance gains versus saving a few dollars. I like stuff that sits at those thresholds.

A large part of value, in my opinion, is quality. You can't have a high value product if the quality is not also high, especially as viewed versus the retail price and versus the competition.

So, I am hoping that when this eventually becomes available, people will be happy with the quality and the price paid, with "quality" also extending to the sonics, of course; that combination in my opinion equals good value.
 
Johnny2Bad

Johnny2Bad

Audioholic Chief
I've sent my pre-production prototype to a lab for measurements. I have a distortion analyzer, which can measure THD + Noise, THD, Signal-to-noise and distortion ratio (SINAD), and individual harmonics to the fifth harmonic (H5) and with some measurement techniques that can be extended. It's limit, taking in consideration of things like the function generator's inherent distortion, etc is down to around 0.03% THD, a little lower for individual harmonics. I also have a Tektronics Oscilloscope that can measure lower, but requires interpretation of waveforms on the display, so is not quite as precise although certainly you can interpret the numbers to be plus/minus a small value.

Those units will be used in production as a Quality Control check. But if you want "state of the art" measurements, you need to use the test equipment that the "big boys" use. For Audio in 2018, that means an Audio Precision distortion analyzer, which costs in the neighborhood of $US 15,000 or so. I don't have one of those ;-) Maybe some day. Mine costs about half that. (My test equipment is worth more than my main system).

Sooo ... I sent the pre-producition unit out to a lab for testing. (As an aside, the AP generates charts with specific attributes that indicate whether the graphs are genuine AP output. Some offshore vendors fake the charts to look like AP output, but if you know what to look for, you can tell. Just so you know).

Some of those results are reproduced below. (Yes, this testing cost me more dineros. More costs associated with bring a product to market). Note that these graphs contain some "grass" which doesn't reflect performance issues, but is due to the fact that the assembly was measured without an enclosure and the AP is picking up noise from cellphones, two-way radio traffic from police, aircraft, taxi cabs, etc, the other test equipment in the Lab, cables, and so on. These are also sums of multiple measurements (x16) added together, so that interference from each iteration is added to the charts; for one pass they would be significantly lessened.

The following is the THD plus noise level measurement. I am quite happy with the result. Note that you can see the highest values at 60 and 180 Hz, which would be due to the unshielded prototype picking up AC line frequency noise. Still, at -130dB, that is equal to 0.0000316%. Note as well the excellent channel matching.

Also, the text reproduced at the top is entered into the AP software. My Lab used an abbreviation of the company name (it's not K&K Audio) but I'm not disclosing the actual name at this point, because I still need to secure the domain names. To change the chart text, I'd have to pay to have the tests re-done.

The way domain name registration works, if you search a name and don't buy the domain that very second, whomever did the search will often buy the name and then try to re-sell it to you at a higher cost. However, I have to also mention that there is a company called K&K that makes a similar product. This is not a copy of their results (they don't publish them anyway). But, just as a FYI.

K&K Audio_ MC Phono Transformer_ Output Noise (LOW GAIN, 1M FFT, 16 averages).PNG
 
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Johnny2Bad

Johnny2Bad

Audioholic Chief
That's all for now ... it's late and I need some sleep. Stay tuned if you are interested in this thread.
 
TLS Guy

TLS Guy

Audioholic Slumlord
A while ago I posted a teaser in the "what have you bought lately" thread about a project I've been working on, a Moving Coil Phono Cartridge Step-up Transformer.

With Gene's gracious permission, I've been allowed to create a thread and, with some limits on what I can and can't say and do ... this will be a commercial product available for sale at some point during 2018, and normally such a thread isn't allowed.

So, starting with my original post, quoted below, I will periodically update the progress. (Click on the "view attachment" links to see photos of the populated PCB).
I see only one photograph at present.

That looks like a passive unit to convert an MC cartridge to MM output, and a switch to change form MC to MM input. We used to use transformers years ago. Ortofon made very high quality Mu-Metal shielded ones. They also made a version of their SPU MC cartridge that had the transformers on the back of the cartridge. This was the SPU-GT. The problem was that it added a lot of mass to the cartridge. My father was a great MC enthusiast and we had the SPU-GT first and then the SPU. I have his final MC the SL 15/E in my collection. Ortofon transformers were used. Ortofon have reintroduces these classic cartridges from the 50s and sixties by popular demand.



The issue is that while the transformer can match the impedance, it can not increase gain which is often required.

I have to say, I think Op-amp based circuits were an advance.

I assume the dip switches are to match cartridge/cable capacitance.

In closing I have to say that solid state phono stages MM and MC are much better than tube ones. Why people would spend a fortune on tube ones is totally beyond me. This is an area where noise in the device matters and Op amps win this horse race by miles.

In the 78 era and the early LP era, small powerful magnets were not available to allow for MM cartridges. So magnetic cartridges were either moving coil or moving iron also known as variable reluctance. So at the dawn of the stereo era that was your option. MM cartridges were pioneered by US manufacturers as powerful small magnets became available.

In 1959 when stereo records hit the store shelves you were pretty much either in the Orofon or Decca camp.



Nothing has ever really touched the transient response of those Decca cartridges. I was in the Decca camp.
 
Johnny2Bad

Johnny2Bad

Audioholic Chief
The switches select two different gain ratios, to match the SUT with various cartridges. There are two because the unit is fully dual-mono ... a significant effort was made in layout to minimize crosstalk between channels. (That is why the switches / resistors are not symmetrically laid out on the PCB ... the signal paths for each channel are exactly equal length and trace widths).

With MC cartridges, capacitance isn't a big issue like it is with MM cartridges. What is sometimes desirable is adjustable output resistance ... with some MC cartridges this can fine tune the high frequency response when you employ transformers.

The selector switches on the board will be used for that (there is only one resistor installed at present ... in the production unit there will be more at different resistances. But for this prototype, I will be installing resistors from various manufacturers at the same value, to sort out best cost and to check for sonic variations).

(Obviously) I disagree that active MC pre-preamps are the best option for this application. I have an excellent active MM/MC pre-preamplifier that I will be checking performance against, (Fremer considered it the equal of the Lehman Black Cube) and I intend to also compare against other well regarded active and passive (transformer) units available in the market, including one that is considered "Class A" by the usual reviewers.

I have to say that there is no way you would get S/N of -160dB (average) with an active MC pre-preamplifier at these signal levels. Once the board is installed in an enclosure, I expect that the interference seen on the AP chart I posted will be eliminated ... certainly there will be an effort to that end, as product development progresses. Does that matter? It doesn't hurt, especially considering any noise at this first stage will be amplified by the MM stage and the line level preamplifier.

I do also have to say that in my experience over the years I've always found that transformers produced the best sound from Moving Coil cartridges. There is also the matter of value ... for an active MC device, you need to spend much more to equal a SUT sonically.

With regard to transformers and low output MC cartridges, they do in fact increase gain (output voltage increases). How they do so is via impedance matching which is somewhat different than how active gain stages work, but the end result is the same.

In a step-up transformer, the primary and secondary have a different number of windings, and therefore they have different impedances. Different impedances cause the signal level to change as it goes through the transformer.

When the secondary has more windings, and therefore a higher impedance than the primary, the signal level at the output of the secondary will be a higher voltage than at the primary input. Unlike most transformers, the ones specially wound for Moving Coil cartridges will pass DC (0 Hz).

I agree that those Deccas were special in ways that aren't normally found in many modern MC cartridges (or MM for that matter). With any phono cartridge, since it is a transducer that generates it's own voltage (no power supply) you are going to have qualities that vary, just like other transducers like microphones and loudspeakers. But that is the interesting part of vinyl reproduction in my opinion.

I'm not sure why you can only see one image ... I am able to see two when I check the OP. But I will be posting other photos in any case. Because I was cautious not to indicate some information on those original photos (blocked out in an image program before posting), in order to comply with posting guidelines, you will see more details in those newer inline images, but not tonight.

Thanks for your interest, without it this thread would probably never have been created. Gene asked me to keep my posts "educational"; so I can't be drawn into subjective debates. Hope you understand.
 
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TLS Guy

TLS Guy

Audioholic Slumlord
I have some fundamental difference with your reasoning. A passive circuit will NOT increase gain. It takes addition of external energy from a source other then the driving device to increase gain.

I agree that the transformer will increase voltage, but that is not gain. Like in all passive solutions gain is negative even if the loss is small.

So when you increase the voltage with the transformer you increase the current load on the cartridge. What you are actually doing is optimizing the impedance for the cartridge. The energy coming out of a transformer can never be greater then the energy going in. It will be less because if inevitable losses.

Now I agree that if you just consider the active solution in isolation a passive solution will be less noisy. That however is irrelevant as you have to consider the total system. What I am saying is that using the transformer solution usually requires higher gain in the preamp, and therefore negates the passive transformer solution.

I think if you used a Quad preamp with the inserted MC module you would be convinced.

Nothing plays vinyl better than vintage Quad in my view. Optimizing LP playback was another skill Peter Walker absolutely excelled at.
 
highfigh

highfigh

Audioholic Slumlord
Thanks for your interest, without it this thread would probably never have been created. Gene asked me to keep my posts "educational"; so I can't be drawn into subjective debates. Hope you understand.
What is the usable range of output voltage from the cartridge? I have a Denon 103d and it's not always easy to find a MC preamp that will produce the same output with that as with the average MM cartridge since its output is lower than most.
 
TLS Guy

TLS Guy

Audioholic Slumlord
What is the usable range of output voltage from the cartridge? I have a Denon 103d and it's not always easy to find a MC preamp that will produce the same output with that as with the average MM cartridge since its output is lower than most.
The output is 0.3 mv at 40 ohms max modulation. So to match the impedance to a 47 Kohm MM input would need a turns ration of 1: 34. Theoretically that would give you 10 mv, but I doubt it would due to losses and cartridge loading.

By even mc standards, that is a very low output cartridge.
 
Johnny2Bad

Johnny2Bad

Audioholic Chief
The output is 0.3 mv at 40 ohms max modulation. So to match the impedance to a 47 Kohm MM input would need a turns ration of 1: 34. Theoretically that would give you 10 mv, but I doubt it would due to losses and cartridge loading.

By even mc standards, that is a very low output cartridge.
You do not want 10mV; that will overload most Moving Magnet phono stages (except probably the ones highfigh doesn't like, a vacuum state one).

Remember a phono cartridge is a transducer and it's output is dependent on the excursions of the stylus.

Try to limit the input voltage to the 47kOhm MM section to 5mV, which leaves some headroom before the phono stage will overload. Such things like a record scratch might elevate the level briefly enough to cause clipping of the MM phono stage if your cartridge is (effectively) much higher output than this.

The Slew Rate of a click or pop is probably the fastest rising/highest transients ever encountered in audio outside the live studio itself (and they make generous use of comp/limiters).

Many modern preamps, having (temporarily at least, for a couple of decades) ditched the phono input, employ slew rate limiting since other sources don't require as much, which allows them to deal with other issues, not the least of which is cost.

Generally speaking most MM phono stages offer about 45dB or so of gain, which is adequate. Add 20 dB or so for your Moving Coil step up (passive, active, doesn't matter) and you are at 65 dB or so, which is enough to output a line level signal that is within the usual variations for a source and any reasonably good preamp should be quite happy with.

As a point of reference, +60dB = 1,000x gain.
 
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Johnny2Bad

Johnny2Bad

Audioholic Chief
I have some fundamental difference with your reasoning. A passive circuit will NOT increase gain. It takes addition of external energy from a source other then the driving device to increase gain.

I agree that the transformer will increase voltage, but that is not gain. Like in all passive solutions gain is negative even if the loss is small.

So when you increase the voltage with the transformer you increase the current load on the cartridge. What you are actually doing is optimizing the impedance for the cartridge. The energy coming out of a transformer can never be greater then the energy going in. It will be less because if inevitable losses.

Now I agree that if you just consider the active solution in isolation a passive solution will be less noisy. That however is irrelevant as you have to consider the total system. What I am saying is that using the transformer solution usually requires higher gain in the preamp, and therefore negates the passive transformer solution.

I think if you used a Quad preamp with the inserted MC module you would be convinced.

Nothing plays vinyl better than vintage Quad in my view. Optimizing LP playback was another skill Peter Walker absolutely excelled at.
There is no "reasoning" going on. I didn't invent this stuff, it's the way it is, at least according to some dead guy named "Ohm". "Disagreeing" won't change it.

Think about it, TLS Guy. I know you are smarter than this. Were it not true, then Solid State amps could not output more power in watts into a lower impedance loudspeaker, tube amps would not need more than one tap on the output transformer, or the Bell Telephone System would not have worked.
 
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Johnny2Bad

Johnny2Bad

Audioholic Chief
THD + Noise vs input level. No issues with overload.

With the DL-103r mentioned earlier in this thread, at 0.3mV (300uV) THD is 0.04% and falling with increased output. In practical terms, as long as the cartridge can handle it, the SUT shouldn't have any problem with falling into congestion as the program material reaches maximum level.

K&K MC Phono Transformer_ THD+N vs Input Level (LOW GAIN, 1 kHz, 20 kHz BW).png
 
TLS Guy

TLS Guy

Audioholic Slumlord
There is no "reasoning" going on. I didn't invent this stuff, it's the way it is, at least according to some dead guy named "Ohm". "Disagreeing" won't change it.

Think about it, TLS Guy. I know you are smarter than this. Were it not true, then Solid State amps could not output more power in watts into a lower impedance loudspeaker, tube amps would not need more than one tap on the output transformer, or the Bell Telephone System would not have worked.
This has nothing to do with Ohm's law, but everything to do with the laws of thermodynamics. Unless this is a nuclear explosion energy can neither be created or destroyed.

In a transformer the energy in will never be greater than the energy out, and will always be a bit less due to heating in the wiring and eddy current losses in the core. All a transformer does is change the relationship of current and voltage between primary and secondary. So if you have a 1:2 transformer the voltage on the primary will half that on the secondary and the current on the primary will be twice that on the secondary. If it was a perfect device power drawn form the secondary would be the same as the power input to the primary. Because the device will not be operating close to absolute zero there will be losses. So the power draw from the secondary will be a bit less than the power put into the primary. So in other words efficiency will be a bit less than 100%. However the above model can also be looked at as impedance conversion that optimizes the relationship of current and voltage for source and load. That is the best way of looking at the MC transformer situation. There is no gain. There is some inevitable loss. All of the energy going into and out of the transformer is supplied by the cartridge from the vibrating stylus. All of the energy comes from the motor driving the turntable.

Now in an active device be it tube, transistor or IC, energy not only comes from the cartridge, but rather more from the power supply powering the active device. This occurs because both on the case of tubes and transistors, including ICs, the inputting device is controlling a gate which allows electron flow.


In a triode tube above, the small voltage from say the cartridge between grid and cathode, allows a much higher voltage to swing between cathode and anode. Energy for this is added from the power source. That is true gain. A tube is in essence a voltage amplifier. It is high impedance and needs a transformer to couple it to low impedance loads.

A transistor on the other hand is primarily a current amplifier.


If we connect a cartridge at 1 between base and emitter it sneaks electrons into the base. This opens the gate and allows a larger electron flow between the emitter and collector (2). Again all the energy does not come from the source, but is heavily supplemented from the energy source V1. As before there is true gain. The tube being a voltage amplifier has a much higher output impedance than a current amplifying transistor which has a low output impedance and can drive speakers directly without a transformer.

That is the way it is. You can argue all you want, but that is the physics behind the situation.

I have to say that the last paragraph of you post is total nonsense and gibberish.
 
Johnny2Bad

Johnny2Bad

Audioholic Chief
" ...
This has nothing to do with Ohm's law, but everything to do with the laws of thermodynamics. Unless this is a nuclear explosion energy can neither be created or destroyed.
..."

Not sure what the debate is about ... using Ohm's law if one parameter falls, one is fixed, the other rises. In a Moving Coil Step Up Transformer, current is fixed (produced by the generator, or motor, which is a transducer, aka phono cartridge), impedance changes, thus voltage changes.

There is no "creation" of energy nor destruction via nuclear or any other means, and no loss ... some, for example, is dissipated via heat but that is not a loss of energy in the system, it's a conversion ... not even at the phono cartridge (which itself is a conversion of the energy contained in the groove when modulations are combined with rotational speed of the album. That energy is derived from the turntable motor's rotation which is again a transfer, from the motor's AC mains power supply, and the non-rotational factors which are the modulations in the groove).

Transformers work via the magnetic properties of the windings and the impedance changes due to different windings in the primary and secondary. Were the windings identical, the impedance ratio is therefore 1:1 and via the current introduced by the transducer the voltage at the secondary would be identical to the voltage at the primary (ignoring losses via heat).

When the windings differ, in the case a typical MC SUT perhaps a ratio of 1:20, the impedance also differs and the voltage at the secondary is higher than at the primary. Reverse the transformer (a transformer can be used either way) and the voltage would be reduced at the secondary (recognizing that the "secondary" is now the "primary").

This is well understood and has been for more than 100 years. No magic, just basic electromagnetic theory.

At the cartridge end, taken to it's basic elements, there is a magnet and a coil. When either moves, also via electromagnetic means, a current is created*. Of the two elements, the magnet is the heaviest element. A moving magnet cartridge has the magnet move with a fixed coil. A moving coil cartridge has the coil move with a fixed magnet. Being the lighter of the two constructions, all other things being equal, a moving coil cartridge can react more quickly and more accurately to the groove modulations.

* This is also how an electric guitar works. The string is the moving element, the coil and magnets are both fixed. Because the string is metal, when it vibrates it induces an alternating current in the pickup. If it were nylon (like with a spanish guitar) then one or the other of the coil and magnet would have to move to induce the current, and since guitarists don't strum coils or magnets, no current would be created. The player himself is the introduction of energy to the system.
 
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Johnny2Bad

Johnny2Bad

Audioholic Chief
At the currently ongoing (April) AXPONA 2018 show, the RIAA has reported the state of the music industry in America (RIAA members are only US-based) from the past year.

Overall music sales are up for the second year in a row, after many years of declines. Streaming is the rising revenue stream and comprises a major amount of revenue (about 60%). Total revenue 2017 is about $8.7 Billion, with about $1.5 Billion of that via physical media.

Of those physical media revenues, vinyl comprised about 30% ($ 400 million), up 10% year-over-year.
 
TLS Guy

TLS Guy

Audioholic Slumlord
" ...
This has nothing to do with Ohm's law, but everything to do with the laws of thermodynamics. Unless this is a nuclear explosion energy can neither be created or destroyed.
..."

Not sure what the debate is about ... using Ohm's law if one parameter falls, one is fixed, the other rises. In a Moving Coil Step Up Transformer, current is fixed (produced by the generator, or motor, which is a transducer, aka phono cartridge), impedance changes, thus voltage changes.

There is no "creation" of energy nor destruction via nuclear or any other means, and no loss ... some, for example, is dissipated via heat but that is not a loss of energy in the system, it's a conversion ... not even at the phono cartridge (which itself is a conversion of the energy contained in the groove when modulations are combined with rotational speed of the album. That energy is derived from the turntable motor's rotation which is again a transfer, from the motor's AC mains power supply, and the non-rotational factors which are the modulations in the groove).

Transformers work via the magnetic properties of the windings and the impedance changes due to different windings in the primary and secondary. Were the windings identical, the impedance ratio is therefore 1:1 and via the current introduced by the transducer the voltage at the secondary would be identical to the voltage at the primary (ignoring losses via heat).

When the windings differ, in the case a typical MC SUT perhaps a ratio of 1:20, the impedance also differs and the voltage at the secondary is higher than at the primary. Reverse the transformer (a transformer can be used either way) and the voltage would be reduced at the secondary (recognizing that the "secondary" is now the "primary").

This is well understood and has been for more than 100 years. No magic, just basic electromagnetic theory.

At the cartridge end, taken to it's basic elements, there is a magnet and a coil. When either moves, also via electromagnetic means, a current is created*. Of the two elements, the magnet is the heaviest element. A moving magnet cartridge has the magnet move with a fixed coil. A moving coil cartridge has the coil move with a fixed magnet. Being the lighter of the two constructions, all other things being equal, a moving coil cartridge can react more quickly and more accurately to the groove modulations.

* This is also how an electric guitar works. The string is the moving element, the coil and magnets are both fixed. Because the string is metal, when it vibrates it induces an alternating current in the pickup. If it were nylon (like with a spanish guitar) then one or the other of the coil and magnet would have to move to induce the current, and since guitarists don't strum coils or magnets, no current would be created. The player himself is the introduction of energy to the system.
You still have not quite got the hang of it.

The current in the coil is a function of the velocity of the coils and not constant. Once the transformer is entered into the equation then at any moment there is a reciprocal change in voltage and current. If the secondary voltage is doubled, the current is halved and in the primary current is doubled and voltage halved. As stated before this can be regarded quite properly as impedance conversion.

Now for mc cartridges it gets complicated as the eddy current losses, which are much greater than resistive losses, become significant. These losses are currents induced in the transformer core and lost as heat in the core. These currents also load the cartridge. The upshot is that the turns ratio needs to be less than you think for a transformer. This ends up limiting the step up voltage, and is one of the biggest limitations of the transformer approach. I alluded to this previously but did not expand on it.

This matters because frequency response of the cartridges is highly impedance dependent with HF rise as impedance increases.


Now unfortunately mc cartridges have a very wide range of optimal impedance loading because of wide variability in internal resistance. This results in a wide range of optimal loading impedance.

So if a transformer is to be used optimally it should be designed for a specific cartridge which is the Ortofon approach.

Now in the Quad 44 the input impedance is adjustable and so is the loading capacitance.

Whether you use a transformer or active interface it is often necessary to use a combination of resistance and capacitance.

This whole issue is why mc systems so often sound over bright. I have found this to be more often true than not. The devotees call it "air". I don't like it. Getting this right takes extreme attention to detail. Seldom is this carried out optimally.
 
Johnny2Bad

Johnny2Bad

Audioholic Chief
... which is why this particular SUT employs user selectable output impedance, which also reflects a change in input impedance as it's in parallel with the transformer secondary. This allows configuration of the HF rise characteristics of the cartridge.

This was referred to in the general description of the circuit.

... {snip} ...

With MC cartridges, capacitance isn't a big issue like it is with MM cartridges. What is sometimes desirable is adjustable output resistance ... with some MC cartridges this can fine tune the high frequency response when you employ transformers.

The selector switches on the board will be used for that (there is only one resistor installed at present ... in the production unit there will be more at different resistances. But for this prototype, I will be installing resistors from various manufacturers at the same value, to sort out best cost and to check for sonic variations).

... {snip} ...
 
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Irvrobinson

Irvrobinson

Audioholic Spartan
I have some fundamental difference with your reasoning. A passive circuit will NOT increase gain. It takes addition of external energy from a source other then the driving device to increase gain.
Surprisingly considering his posting history, Mark, Mr. Bad is actually correct. There are two types of gain, voltage gain and power gain. Transformers can have voltage gain, albeit with a small loss of current. Passive circuits cannot provide power gain; in fact they always have an insertion loss. (Otherwise they'd violate the 1st Law of Thermodynamics.) Active circuits can have both voltage and power gains.
 

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