A question of loading...


I have just replaced my aging tube preamp with a new model. When I was using my older model with tube phono stage, I would run my Lyra Kleos and other MC cartridges with a load of 750 ohms. So, I assumed that with my new tube phono stage, which also utilizes a transformer in the phono stage and is also built into my new preamp, that the same cartridge loading would apply. I listened to the Kleos for about a week with this loading, and frankly, while it was fine, I wasn’t bowled over. Tonight I decided to experiment, so the first thing I did was to run the cartridge straight in, with no loading plugs. WOW, the increase in overall musicality and soundstage width was eye opening! Lesson learned is that not all gear is going to react the same when it comes to cartridge loading, particularly if there is a transformer involved and even if you are using the same cartridge from one phono stage to the next! An eye opener, anyone else experience something like this?
749cdfb3 0814 490e b189 a364ad773263daveyf
I've been running MC's into 47k since the 80's sans step up transformers. Do you know what load the Kleos is seeing at the moment ?
@dover  At the moment, i am presuming that since I am not loading the cartridge at all, it is seeing 47K. This is what surprises me a little, as previously with the older tube phono stage sans the SUT, a straight in with no load was definitely inferior to the custom 750 ohm plug that i was using. Now, with the SUT and at 47K ( presumably) that is certainly no longer the case as the SQ is as described in my OP.
I have a Lyra kleos and an Ortofon Cadenza bronze and run those with no loading into a Herron VTPH-2A. 
Soon I’m going to try a Kiseki purple heart and the recommended loading is 400 ohms but I will try it without loading plugs.
As I understand, loading is for the phono stage, not the cartridge.
Loading is at the phono stage, but it absolutely has an effect on the sound of the cartridge. There is some belief that loading effects a MM cartridge more than a MC, but I am not totally sure this is the case.
The loading would seem to be dependent on the combination of what sounds best depending on the phono stage and the cartridge, wherein I was previously under the impression that it was somewhat cartridge dependent and NOT to do with the particular phono stage as much. Seems like it is both at this point.
@daveyf 

The reason I asked  about the actual loading on MC is because I was wondering how they got the extra 11db for the MC input. If they used low gain transformers then the actual load would be 47k/turns ratio (of the transformer )squared - which would result in a load seen by the MC cartridge somewhere between 3500 - 5000 ohms.
According to Steophile review of the Cat SL1 Renaissance MC unloaded measured 3560 ohms.
So it is possble your load is between 3 & 5kohms.

Jonathan Carr the designer of your cartridge says that loading does not affect the cartridge itself with modern MC designs, but what loading  can do is dampen any ultrasonics that might affect the phono stage ( solid state devices can have low overload margins at very high frequencies, whereas tube designs less so ). Thats why he specs out loading range  up to 47k.

In my view if you can run MC's into higher impedances without upsetting the phono its a good thing. Klyne has done this for years, they use higher loading combined with very high frequency contouring to tame any ultrasonic nasties.. you are hearing the benefit of "unloading" your cartridge.
@dover   Thanks. I was certainly quite surprised at the nice increase in SQ due to 'unloading' the cartridge ( even if maybe the load is as you say, at around 3500 ohms!) . Oddly, when I was using the older style CAT phono stage without the low gain transformers and the same cartridge, the SQ was definitely better at the 750 ohm level. Just goes to show that one cannot assume similarities in this area with different gear upstream.

@dover is Klyne still active?
Dear @solypsa : I think closed a few years ago. Excellent electronics designs.


http://www.klyne.com/pages/system7.html


this was its phone:

Klyne Audio ArtsOlympia, WA 98501(360) 273-8477


and here you can read the cartridge loading through Klyne  unit:

https://www.techtrader.ch/auction/2016/03/Klyne-7-PX_B-3.5.3-manual.pdf


Regards and enjoy the MUSIC NOT DISTORTIONS,
R.
As I posted elsewhere recently, with my Lyra Etna Lamda and Manley Steelhead, unloading to 25 does produce a very euphonic lively sound with more "space" in all directions. But I can hear distortion-the type of distortion one hears when there is too much 2nd harmonic. It is very pleasant but you know it is not right. It is the audio equivalent of a carnival mirror. Too much loading and the sound becomes lifeless. 100K killed the sound. You have to strike a balance. For my Etna, it is 50K. But there are so many variables-VTA, cantilever-suspension break-in, the preamp, the tonearm cabling. I use Reed 3P arms with the cryo treated Firewire that runs straight from clips to RCA's. 
Dear @daveyf : This is a " little " diferent point of view of M.Huber designer and owner of FM Acoustics about MC loading:

https://www.fmacoustics.com/products/phono-linearizers/fm-223/

just download the data sheet information at the end of the page.

His unit is a unique design.

According that that loading of the Etna Lamda at 50K says the design problem that Manley unit has as any other phono stage design where the owners needs that kind of loading values to achieve a decent sound reproduction.

In my system unit that just does not happens and that’s why I never need to use that kind of loading figure. I tested it and that's why I said that.

R.
I do rue your gas, Raul. 
There is nothing in Daveyf's posts to indicate he is using an Etna Lambda or a Manley phono stage. You seem to be confusing me with him. Second, there is nothing in your link that even remotely addresses the issue. Are you inebriated when you post sir? It would explain much.
//S// Fsonicsmith Eating Raul. 
@fsonicsmith 

Your 1st email above is impossible to decipher

unloading to 25 does produce a very euphonic lively sound
25 what ? - 25 ohms or 25kohms ?
If you mean 25ohms you are loading the cartridge, not unloading it.
If you mean 25kohms, then you are indeed "unloading it", relative to say 100ohms.
Too much loading and the sound becomes lifeless.You have to strike a balance. For my Etna, it is 50K. 
This statement is oxymoronic.
 "too much loading and the sound becomes lifeless" - I agree with this if you mean loading down to 50, 100 ohms etc.
"For my Etna, it is 50k" -  50 kohms is unloading, its higher than the standard 47k.






Dear @fsonicsmith  : I know what I posted perfectly, no problem with.

I took what you posted only as an example of what M.Huber states in his site but I know that you not download the information about that's pertinent to that 50K/Manley combination.

Read again what I posted to Davey and you will know you are wrong on your statement.

R.
@rauliruegas   Thanks for your post and the link. I did read the link. Seems like FM believes that 20-500 ohms works best for MC cartridges. While this may be true with their preamp, it was not true with my older CAT as it sounded best loaded to 750 Ohms and NOT lower and as stated in my OP, my new model CAT sounds way better unloaded! 
For my Etna, it is 50k" -  50 kohms is unloading, its higher than the standard 47k.
You are showing your ignorance Dover. 47K is not standard for a MC and not standard with the Etna Lambda, which I am listening to as I type this. 47K is the standard for MM. Not for MC. We vinyl junkies, for better or worse, refer to lower capacitance as unloading even though you are technically correct. Why is this? Because as you lower loading values, the cantilever is subject to less damping. At the end of the day it is damping and not technical numbers that counts. Someone who knows his stuff wrote this;
The loading that the owner adds is a resistor in parallel to the signal path. That means that the higher the value of that resistor, the LOWER the amount of loading. Higher loading (lower value of the resistor) tends to damp high frequency peaks. With modern cartridges, the peak is usually well into the ultrasonic range, so loading is not needed as much as was the case in the past to correct for peaks. Jonathan Carr, the designer and builder of Lyra cartridges is among those who believe that additional loading is not needed to damp such peaks and it takes away some of the extension and open and airy sound on top. However, even though the peak is outside of the normal hearing range, it can be high enough in amplitude to overload some phono stages. He believes that loading is more important for preventing such overloading than in taming the frequency response of cartridges. I tend to agree with this. I happen to have a phono stage that does not overload and I like to run my MC cartridges (Lyra Titan and Transfiguration Orpheus L) wide open.

Sometimes, loading helps to suppress RF interference. A friend had a Hovland preamp that was passing a lot of hashy noise. It turned out that the factory default loading was 100k (essentially no loading). When we increased loading, the noise went away.

There is absolutely no harm in utilizing any particular amount of loading so one can experiment. I tend to find that higher levels of loading, say any value lower than 100 ohms, makes the sound warmer, more bass prevalent and shut down on top. Also, the lower the resistor value, the lower the total output so that volume level will go down. As a very rough rule, with most cartridges, a load of about 125 to 150 works perfectly well, and no much difference is heard if a higher value resistor (lower loading) than that is used.


@fsonicsmith 
47K is the standard for MM. Not for MC.
Whats your point. Are you loading at 50k as you claim or 50 ohms ?

We vinyl junkies, for better or worse, refer to lower capacitance as unloading even though you are technically correct. 
MC's are not generally impacted by capacitance changes.
Loading generally refers to resistance with MC's.
Because as you lower loading values, the cantilever is subject to less damping. At the end of the day it is damping and not technical numbers that counts. 
Jonathan Carr, the designer of your cartridge, does not agree with this.
Your theory is old school thinking. If you search for JCarr postings on loading you will find his views elsewhere on this forum.
 


You are showing your ignorance Dover. 47K is not standard for a MC and not standard with the Etna Lambda, which I am listening to as I type this. 47K is the standard for MM. Not for MC.
Actually 47K is the standard input impedance for all phono sections, MM or LOMC.


LOMC cartridges often seem to need lower impedances, but this is really for the benefit of the phono preamp, not the cartridge, due to the reasons Jonathan Carr has talked about, mentioned earlier on this thread.


I've been telling people this for years. If your phono section does not have troubles with the RFI caused by most LOMC cartridges (and the capacitance of the tonearm cable) then 47K will sound just fine.

An additional side benefit will be less ticks and pops, since the phono preamp will generate ticks and pops if the input section is overloaded by the RFI at its input. It is for this reason that tubes have a distinct advantage over solid state, as its easier to designed a phono section using tubes that is hard to overload.
+ 1 Atmasphere.

OTOH, do tubes have a distinct advantage?? I would say that they do when it comes to overall SQ, plus the decreased likelihood of overload, BUT they are never 100% quiet...at least IME. There is always some minimal hiss..and this leads me to believe that their noise floor has to be higher than ss. 
You are showing your ignorance Dover. 47K is not standard for a MC and not standard with the Etna Lambda, which I am listening to as I type this. 47K is the standard for MM. Not for MC.
Actually 47K is the standard input impedance for all phono sections, MM or LOMC.


LOMC cartridges often seem to need lower impedances, but this is really for the benefit of the phono preamp, not the cartridge, due to the reasons Jonathan Carr has talked about, mentioned earlier on this thread.


I've been telling people this for years. If your phono section does not have troubles with the RFI caused by most LOMC cartridges (and the capacitance of the tonearm cable) then 47K will sound just fine.

An additional side benefit will be less ticks and pops, since the phono preamp will generate ticks and pops if the input section is overloaded by the RFI at its input. It is for this reason that tubes have a distinct advantage over solid state, as its easier to designed a phono section using tubes that is hard to overload.
Ralph, as I have said many times you are a great asset and resource to this Board but when it comes to phono stage topics many including myself simply feel you are somehow losing the forest for the trees, to put it politely. First, Jonathan Carr never says anything remotely similar about optimum loading for his cartridges. I am looking at Jonathan Carr's loading chart that came with my Etna as I type this and depending upon the gain setting and the total capacitance of the tonearm wire in interaction with the phono stage and the recommended loading ranges between 104 and 340 ohms for 0dB gain and between 284 and 887 in the highest gain column of +6dB. 
But that is Jonathan Carr who sees things (rightly so) from the perspective of the cartridge manufacturer. Now lets talk about phono stage producers. They don't espouse charts, they talk about listening. Each phono stage manufacturer knows the attributes of their designs. My Manley Steelhead with built in step-up transformers is not going to behave the way a Sutherland 20-20 (just for example) will. 
To say that 47K is the standard or de facto or even starting-point loading for a LOMC is ludicrous. 
Dear @daveyf  : There is no single advantage, today SS phono stages just can't be overloaded in normal condition: comes with very good headroom. That " problem " was a " problem " of the past/several years ago. Everything change SS manufacturers move on because they learn too, they are not sticked in the past as atmasphere.

In the other side in his last post @fsonicsmith is just rigth and if we read the page 3 and 4 in the FM Acoustics link data sheet M.Huber point out easy and important information about.

Atmasphere is sticked with his very old opinion and in several threads here or in WBT was defeated but is his privilege to be sticked there: just does not moves. Who cares? .

Yes, in other audio subjects he is a very good resource as @fsonicsmith  says.

R.
Actually 47K is the standard input impedance for all phono sections, MM or LOMC.
Perhaps Ralph is referring to "industry standards" which are like the  biological artifacts of teets on boars and tailbones on humans. Or better yet, like the silly 1996 standard set by the industry for headphone amps to have 120 ohm output impedance. The audio industry has a long sordid history of setting standards that made little sense other than being convenient at the time and then slavishly and stupidly following them for years until someone brave and brash yelled for truth. People like Charley Hansen for example. How I (and most all of us) miss Charley. 
OTOH, do tubes have a distinct advantage?? I would say that they do when it comes to overall SQ, plus the decreased likelihood of overload, BUT they are never 100% quiet...at least IME. There is always some minimal hiss..and this leads me to believe that their noise floor has to be higher than ss.
Yes, they are noisier but they can be quiet enough that 0.2mV is no worries.
Jonathan Carr never says anything remotely similar about optimum loading for his cartridges. I am looking at Jonathan Carr's loading chart that came with my Etna as I type this and depending upon the gain setting and the total capacitance of the tonearm wire in interaction with the phono stage and the recommended loading ranges between 104 and 340 ohms for 0dB gain and between 284 and 887 in the highest gain column of +6dB.
But that is Jonathan Carr who sees things (rightly so) from the perspective of the cartridge manufacturer. Now lets talk about phono stage producers. They don't espouse charts, they talk about listening. Each phono stage manufacturer knows the attributes of their designs. My Manley Steelhead with built in step-up transformers is not going to behave the way a Sutherland 20-20 (just for example) will.
To say that 47K is the standard or de facto or even starting-point loading for a LOMC is ludicrous. 
@fsonicsmith 

You might think it ludicrous, but 47K is the industry standard for phonograph inputs nonetheless. Because many phono sections have problems with the RFI generated by LOMC cartridges (keeping in mind how much gain they employ to work with cartridges of output this low) its common to see loading options on such preamps. Think about it this way: Since all cartridges are different, and you need an input resistance with any circuit that can amplify, what would be the correct value for that resistance?? You might ask your self why most phono sections have a 47K input impedance... the answer is that is the industry standard; it was not something that is a random coincidence that so many phono sections are built this way.


Jonathon has his recommendations for a very simple reason: He cannot be sure that the phono section to which you are connecting his product is going to be alright with the RFI generated by the cartridge/tonearm cable combination. Further, he's also go not idea what cable you're using! So he has loading recommendations on that account, and they cover a range rather than being a specific value. He also knows that most phono sections don't deal with the RFI issue very well. But if you talk to him, which I have done in person, you find out that he thinks 'no loading' (IOW the stock 47K input of the phono section) is better if you can pull it off.

Its true as you say that not all phono sections act the same :)  That is a bit of an understatement! For example, a phono section employing an SUT will not have RFI issues, since the RFI is blocked by the SUT. Instead, you have to be careful to load the output of the SUT correctly so that the transformer does not 'ring' (distort) on account of the specific impedance of the cartridge (if you want to know more about how the ringing phenomena works please ask). So you'll find that depending on the cartridge, different resistor/capacitor values are used to accomplish that loading. So yeah, that's quite a bit different from a solid state phono section using opamps or an all-tube phono section that can run the LOMC cartridge straight in!

There is no single advantage, today SS phono stages just can't be overloaded in normal condition: comes with very good headroom. That " problem " was a " problem " of the past/several years ago.
With a solid state phono section using either opamps or discreet transistors, its the part that is outside the feedback loop that is open to overload. This is the input circuit of the preamp, which might be no more than the base of the input transistor.  We're talking about an electrical peak of 20-30dB that occurs with all LOMC cartridges in tandem with the tonearm cable (the former having a high-Q inductance, the latter having a capacitance; the two in parallel form the resonant circuit, whose resonance might be at several MHz). While there are SS phono sections that deal with this properly (Pass Labs for example) its a falsehood to say that all of them do!


Its a simple fact that if the designer has not made provision for this resonant peak, it can overload the input circuit, resulting in a tick or pop when it does so. To get around this problem, you have two options: design the phono section to take quite a bit more input voltage than LOMC cartridges are known to produce (and do as much as you can to prevent RFI from coming in through the input connectors), or come up with a loading provision (the 'loading resistor'), so the resonant peak can be detuned.


Of course if you use the loading resistor option, you are asking the cartridge to do more work. If you're using 100 ohms as a loading resistor, that's a couple of orders of magnitude more work than if the cartridge is driving 47K. This results in the cantilever being stiffer- the same as what happens with a raw woofer if you short it out (they are both based on the same principle of operation).  This is not a matter of debate, if you feel the desire to do so, take it up with Mr. Ohm. Ohm's Law cannot be defeated and isn't open to interpretation. If there is more current flowing, it has to come from somewhere and that somewhere is the motion of the stylus in the groove. So the fact that the cantilever gets stiffer is not controversial. Anyone versed in the art knows this- Jonathan Carr and I discussed this issue at the Munich Show a few years ago. 


Raul's stipulation that this overload issue is something of the past is correct as most phono sections were only designed to have 'enough gain, low enough noise and proper EQ' and the electrical resonance was ignored. But he is incorrect in his assertion that this has been put to bed; this is why loading provisions exist on current equipment and are identified as 'loading' when they are really there for the benefit of the phono section, and the phono section will sound different if the RFI isn't suppressed. Its likely that the cartridge will sound different too, not because you are preventing it from ringing, but because the cantilever becomes stiffer as the 'load' resistance is decreased. This measurably affects its mechanical resonance in the tonearm. 





fsonic, May I just ask a question without making you angry or making anyone else angry.  As the owner of a Manley Steelhead myself, I am wondering how you achieve a load of 50K ohms or 100K ohms or "25", by which I take it you mean 25 ohms?  As you know, the max load if you use one of the MC inputs on the Steelhead is 400 ohms, and it offers choices going down from there to 25 ohms minimum.  I assume that is what you did in that case.  The Lyra website says the Etna Lambda has 4.2 ohms internal impedance, so 25 ohms would be a bit on the low side for phono input resistance and your description of the aural effect makes a lot of sense in that context.   The Steelhead uses autoformers in its MC section to achieve the various load resistances, which is a bit different electronically from using a SUT. I'm sure you know that.  I sure wish I could get hold of a schematic, because I would like to see how they use the autoformers.

If you connect an MC cartridge to the MM input, there you can have 47K ohms, but 50K and 100K are not offered.  However, if you change the fixed load resistor inside the chassis from 47K to 50K or 100K, by that means only can you achieve either of those two load resistances.  Is that what you have done?  I've actually purchased the resistors to change the max MM load resistance from 47K to 100K, but so far I have not done it.  I found the Steelhead to benefit greatly from a modification to its output stages (both the phono output and the passive linestage output), for what it's worth.

Not that it matters a lot, but I have to agree with Dover. In the conventional parlance, to increase the value of the load resistor is to decrease its load.  Capacitance is also a "load", but that is a different parameter.  In any case, I knew what you meant, when you discussed the effects of various load resistances, and that is what counts.
@lewm 
Not angry at all-in fact Lewm-you are among a handful of regulars on this Board that I rely upon on all analog matters and respect as having greater grasp of technical issues than I do. 
I previously acknowledged to Dover that he was correct and that I had misspoke as to loading. 
As you know, the max load if you use one of the MC inputs on the Steelhead is 400 ohms, and it offers choices going down from there to 25 ohms minimum. I assume that is what you did in that case. The Lyra website says the Etna Lambda has 4.2 ohms internal impedance, so 25 ohms would be a bit on the low side for phono input resistance and your description of the aural effect makes a lot of sense in that context.  
Yes, I meant that 25 ohms on the Steelhead with the Etna (and my VdH Crimson before it) sounded loose and sloppy, 50 ohms sounds ok on the Etna and sounded best with my VdH Crimson, and 100 sounds best with the Etna Lambda in terms of sounding tight and controlled without all the life being sucked out of the music, which occurs at all higher levels. The lower settings are euphonic but distorted. And yes, I use the two MC inputs only and not the MM. And I knew and agree that my use of the term "internal step ups" was sloppy and loose too (pun) as Manley refers to them as both in the owners manual (though I may be wrong and maybe they use the term "autoformer" exclusively) but as you stated, without seeing a schematic, even an informed person like you would find it difficult to explain what is going on and why. 

Ralph-thank you for your very polite and informative response. I apologize for my strong words directed at you. 
@atmasphere Ralph, thank you for contributing to this topic. What you posted was extremely informative and interesting. I certainly think that a lot of fellow a’philes can learn a lot from you.

In my case, i am still a little surprised as to why the new preamp which features a phono overload spec of 70mv rms for MC’s is so very different to my old model, I am guessing that this is high enough to not risk ringing with my particular cartridge, a Lyra Kleos that puts out 0.5mv. What is odd, and I am not quite understanding this part, is why with my older CAT phono stage, which did not use a SUT at all, that a load of 750 ohms was better sounding than straight in at 47Kohms, yet with my new model, this is definitely not the case. Presumably due to the SUT in my new CAT?? One thing, the CAT has a healthy output voltage at about 50 volts..
I still maintain-righty or wrongly-that two things are at play with loading. One can argue that they are interrelated. One is preventing ringing/overload and another is changing the magnetically induced behavior of the cantilever. 
My own misstatements about higher loading values being the same as higher loading is a common one and a common source of confusion. I think that the confusion stems from loading being nothing more than a resistor placed between the signal wires-left and right-and ground. A high value resistor such as 47K means less loading because the circuit is left relatively open. The cartridge/cantilever sees no electro-magnetic mechanical "constraint" because the resistor is to ground. Conversely, a low resistor value comes close to a short circuit/complete connection between signal and ground causing the cantilever to become electromechanically constrained. 
Ralph and others talk about the cartridge/cantilever having "to do more work" at higher loading. Ralph explains;
Of course if you use the loading resistor option, you are asking the cartridge to do more work. If you're using 100 ohms as a loading resistor, that's a couple of orders of magnitude more work than if the cartridge is driving 47K. This results in the cantilever being stiffer- the same as what happens with a raw woofer if you short it out (they are both based on the same principle of operation). This is not a matter of debate, if you feel the desire to do so, take it up with Mr. Ohm. Ohm's Law cannot be defeated and isn't open to interpretation. If there is more current flowing, it has to come from somewhere and that somewhere is the motion of the stylus in the groove. So the fact that the cantilever gets stiffer is not controversial. Anyone versed in the art knows this- Jonathan Carr and I discussed this issue at the Munich Show a few years ago.
I will freely confess that I thought the loose and flabby sound I heard with the 25 and 50 ohm settings on my Steelhead was the result of a LESS STIFF cantilever and not a too-stiff cantilever as Ralph explains above. It does make sense-once one understands the higher resistor value being to ground-that the lower resistor value approaches a short circuit and that the cantilever becomes stiffer and less damped, not less stiff and more damped. Damping is the absorption/dissipation of energy. You all know that. Why a less damped cantilever results in loose, flabby sound and a highly damped cantilever results in lifeless sound is still a tough concept for me to get my head around. I think I know what Ralph means when he speaks of the cartridge and cantilever having "to do more work" with higher loading by using his raw woofer analogy and imagining having to create an electric signal by applying more mechanical force-not less-pushing on a close to a short-circuited and electromagnetically stiffened woofer cone to generate a given amount of electrical output but still-this does little to explain why a less damped (stiffer) cantilever sounds livelier and why a highly damped (loose) cantilever sounds lifeless. 
Ralph-thank you for your very polite and informative response. I apologize for my strong words directed at you.
No worries- and no offense taken. But I appreciate your words.
What is odd, and I am not quite understanding this part, is why with my older CAT phono stage, which did not use a SUT at all, that a load of 750 ohms was better sounding than straight in at 47Kohms, yet with my new model, this is definitely not the case. Presumably due to the SUT in my new CAT??
A lot to unpack here....

Its a lot easier to build a tube input circuit that has much higher overload characteristics! In a tube circuit meant for LOMC, if you overload it with too much input voltage, the overload isn't occurring in the input stage- it happens further downstream. With solid state, the overload often occurs at or very near the input, often because the circuit uses feedback, and the input section might be outside the feedback loop- even if its only the base of a transistor. But semiconductors are far more likely to rectify RF energy too, since they are diodes at some point or another. Its this latter characteristic that makes them more pesky in this regard.

SUTs are another matter altogether! I suspect Ken got tired of people calling about noisy tubes and SUTs are a way to get around that. For tubes to be really quiet in the front end of a phono section, they have to be at the top of their game. As they lose transconductance with age, the noise goes up. You have to keep the tubes active even when the preamp is being used playing CDs, so the tubes are going downhill all the time. By installing an SUT, you can easily quadruple the usable life of the input tubes.


But that comes at a price! SUTs have to be properly loaded to prevent ringing (distortion) and the proper load varies from cartridge to cartridge, since transformers **transform** impedance. So if you have a 10 ohm cartridge, the output of the SUT will be an impedance much higher than if you have a 5 ohm cartridge. So the load it needs will be different too. If the load is insufficient (too high impedance) the transformer will ring, which is to say some very high amplitude harmonics will appear at its output. This makes them very tricky to use! I find that even with them set up right, you lose a bit of detail (bandwidth at this signal level shouldn't be an issue)- that's why I've really stayed away from transformers in the audio path.

It does make sense-once one understands the higher resistor value being to ground-that the lower resistor value approaches a short circuit and that the cantilever becomes stiffer and less damped, not less stiff and more damped. Damping is the absorption/dissipation of energy.
Just to be clear- if you load the cartridge more, the cantilever will be more damped in addition to being stiffer. This can affect tracking if you get the resulting mechanical resonance outside of the 7-12Hz window.

I still maintain-righty or wrongly-that two things are at play with loading. One can argue that they are interrelated. One is preventing ringing/overload and another is changing the magnetically induced behavior of the cantilever.

We need to be really specific about what is happening here. Many years ago I had this idea about building a little box that would sort out what the ideal loading value was for a LOMC cartridge. This might have been about 30-35 years ago... At any rate, what I found was that **the cartridge itself does not ring at audio frequencies**. You can pass a 10KHz square wave through it and it will look exactly like a 10KHz square wave at either end of the cartridge. Quite simply the inductance is so low that its inconsequential at audio frequencies. It can't ring (and on this point, MM cartridge most definitely **can**, so loading with them as affecting things at or very near audio frequencies). BUT- it can have effects at much higher frequencies as I described earlier. (The result of my research in this regard was that I would not be able to make such a box, since ringing wasn't the issue.)

BTW, if there is some question about what the load should be, @lewm 's rule of thumb of being 10X higher than that of the cartridge itself is a pretty good one. Such a value will detune the radio frequency issues and won't affect the output level of the cartridge.


There are more than just two things going on with loading- and they are very much interrelated as you say. Two are caused by the cantilever getting stiffer- it can affect how the cartridge tracks and its arguable that being less supple, is less able to trace higher frequencies. So that's two things. But the loading affects the preamp too; by eliminating the RFI at the phono input, it can make the preamp less bright (a common result of RFI in audio circuits) and possibly less ticks and pops if the phono section has poor high frequency overload margins.


@atmasphere  Once again, very interesting and informative..thank you.

Ken uses a SUT that doesn't really have a lot of boost because I think he believes that as the step up increases, the loss is SQ is too great. What i am still guessing at is that the SUT allows for a better synergy with my Lyra as to what it wants to see as a load than the prior 750ohm resistor that I was using. The Lyra has a fairly healthy output for a MC at 0.5 mv and I am sure this is not putting much stress on the SUT. It was not putting too much stress on the phono stage before on my old non-SUT unit. Now the advantage of using an SUT has aways been to me that I could entertain ultra low output cartridges without too much tube noise, by ultra low, I am saying below 0.3mv...which there are quite a few very good ones out there.I wonder if that would be an option with this new CAT model, somehow, I doubt it???
Ken uses a SUT that doesn't really have a lot of boost because I think he believes that as the step up increases, the loss is SQ is too great.
That's been our experience too. The more stepup you use the less bandwidth you get.


We regularly run cartridges that are 0.2mV. If you have an SUT you should be able to get in that same range quite easily. The only thing you would have to work on is the loading of the SUT, with which Ken might be able to help you. We use Jensen Transformers when we use an SUT; they have published a pdf file of all the loading values for a great deal of different cartridges including Lyras.


Keep in mind that 0.25mV is 6dB less than 0.5mV; that means you'll have to run the volume control up a few notches to get the same sound pressure. I don't think you'll have any problems doing that :)
Indeed, the CAT has plenty of gain available, almost too much. With Ken's new 47 step volume control, luckily there is plenty of control and there should be no issue running up a few steps.
With Ken’s new 47 step volume control, luckily there is plenty of control and there should be no issue running up a few steps.
47 steps in attenuators seems to be another inexplicable industry standard.
@daveyf 
@atmasphere 
I suspect Ken got tired of people calling about noisy tubes and SUTs are a way to get around that.
Yep, I know from experience that customers were complaining about their Koetsu's with the CAT - not enough gain & too much noise.
The problem was that you only needed a transformer with about 10db ( turns ratio 1:5 ). Most off the shelf audio SUT's are up around 20/26db - which resulted in too much gain. I think this is why he has addressed the gain issue in the way he has.
Daveyf, the gain is also impacted by the system gain - how sensitive is your power amp input - so there are always exceptions.

@dover   Good point about the overall gain in the system. However, my ancillary gear is exactly the same, with the exception of the old preamp vs the new preamp. So. I would have to believe the overall gain should be the same. My amps ( i use both a ss stereo amp and a tube mono block..(not at the same time) do have similar gain structures ( the ss amp has a gain switch to switch between two settings- a very useful feature that I wish more amps featured)) .