SUT - electrical theory and practical experience

that's what you wished but JC never came to support your tale. In that regards you are very bad looser, sorry.

Aside from the very obvious turnabout/contradiction from your prior post to me, just so you know, I've never asked JCarr to give me any support- I never felt any was needed and still don't. So how do you arrive at the 'looser' comment?? You already admitted I was right, confirmed what @intactaudio had also said.

So could you just lay off the trolling?? How about for the next shall we say, 3 days?? Have a good time over the weekend- seriously!

maybe I explained in wrong way: of course that as the theory says it happens, this is not under discussion and maybe as intact said you can open the fifth thread about till you can win.

😀 Apparently, I already did...

Exist at least 4 long threads about in this forum, in all were very hot dialogues and that the end even that in theory exist the phenomenon that the cartridge cantilever could " suffer " of some kind of " stifness "  and even if happens Wynn proved in two of those thread with measurements in real time that the  effect in reality does not disturb the cartridge tracking levels and the one that really could " suffers " with that load/cartridge inductance and total nettwork capacitance is the bad phono stages designs but fortunatelly today not only Phono Stages have widebandwindth but high overload levels.

...And with that Raul has created a new branch of physics. That the cantilever is affected is a very real thing. If not- then we all could solve the world's energy problems by simply using enough phono cartridges 😂

@rauliruegas Before you implicate Mr Wyn with such a proposition, you better be sure that's what he really said! I think you'll find that he said something a bit more specific.

I believe loading of a MC cartridge has a dramatic effect on the electromechanical behavior of the cartridge but that is a topic for another thread.

@intactaudio Yes! You and I are on the same page here.

What is one to do when the two approaches listed above push you in opposite directions? Menno Van Der Veen acknowledged this and noted that after the proper secondary termination is determined, the load the cartridge sees can be further increased by placing resistance across the primary (ie to the cartridge directly).

@intactaudio I am in disagreement with Mr. Der Veen on this topic. My tests of LOMC cartridges has show that their inductance is so low that they simply do not ring at audio frequencies; they can pass a 10KHz squarewave quite nicely. This suggests that they are not in need of a 'load'. Thus the only load required is really at the output of the transformer, which will (as you point out) will need to be loaded differently depending on the cartridge used.

It is for this reason that Jensen has published a pdf of all the loading networks needed for all the cartridges known on their website. To my knowledge there are no loading values suggested for the primary side of the transformer. 

Of course it should be kept in mind that the tonearm interconnect cable and the interconnect on the secondary side be as low capacitance as possible for best results.

It looks like Bats are being catered for in the frequencies being presented and being a outcome of a Theorem presented.

@pindac The theory behind wide bandwidth in a zero feedback system has to do with filter theory. In a zero feedback system like a cartridge driving an SUT all the elements are passive so there is no correction.

To prevent phase shift (per filter theory) wide bandwidth is required.

Filter theory as it applies here:

Typically when a single frequency pole is present, it will induce a rolloff at 6dB per octave. Phase shift components of a 6dB slope will be induced down to 1/10th the cutoff frequency (the latter being defined as the -3dB point). That is why you see such wide bandwidths promoted in transformers, which typically have no feedback correction.

(As you may have surmised, if there is feedback correction the need for such wide bandwidth is reduced.)

So an SUT that cuts off at 50KHz will have some phase shift down to about 5KHz. The ear perceives phase shift over a range of frequencies although it cannot perceive it at any one frequency. Over a range of 5KHz to 20KHz where phase shift is induced by a 6dB/ocatve rolloff at 50KHz, the ear will perceive this as a ’darkness’ or ’slowness’; IOW a tonality is assigned. Conversely if there is an zero introduced at 50KHz rather than a pole, the ear will perceive this as a ’brightness’. So to maintain a neutral presentation, the bandwidth is important.

In any case what's false  is what you posted because I gave several evidences/facts/measures and in the 99% of those threads you was there and you never never proved with measurements that I was wrong, never ever.

bla bla bla... I see now that you have moved from giving 'proof' to providing 'evidence'. Gotta keep your story straight...

@rauliruegas I attacked your post and not you. There is a difference.

Your post contains false information. For example you claim to have presented ’proof’ on multiple occasions. At best you presented ’evidence’ which can be used to point at a proof but even so your evidence is sketchy.

Your comment about tubes is not reflected by people that spend plenty of time listening to real music in real music venues. It was an entirely made up story based on your own personal anecdote as best I can make out.

Your use of the word ’mediocrity’ has some kind of personal meaning attached to it. I can use the word in a similar fashion; for example I don’t care at all a phono stage is super quiet if the sound coming from it is irritating- it is mediocre regardless. Generalizations frequently result in false statements.

This comment is an attack on the integrity of another member and is thus ad hominem:

I never think to use the information you share about the RIAA deviation of your unit that as I said on the subject goes around mediocrity with that 0.66 db " fligth " in the RIAA that’s good for you because is your design but that’s a shame for a RIAA phono stage.

Being ad hominem it is a logical fallacy so false by definition.

It’s not that " do not align with your measurements " because the issue is not about just measurements.

All tube phono stages needs/necessary a SUT for LOMC cartridges and the ones active high gain tube ones are around mediocrity even the effort of the designers that’s it’s not the issue too.

If you have enough/deep live MUSIC experiences seated at near field position then you know that tubes and specially in phono stage is not the best alternative but an SS one and if you think it’s rigth then not because I say it but you are way wrong no matters what and I can prove it with facts as I did it in hundreds of threads here and in other internet forums.

 

I know that I don’t like you but that is up to you, not my problem. I never let that attitude against " some one " let me post with that kind of attitude, normally I’m unbiased about.

 

I never think to use the information you share about the RIAA deviation of your unit that as I said on the subject goes around mediocrity with that 0.66 db " fligth " in the RIAA that's good for you because is your design but that's a shame for a RIAA phono stage.

This entire post is rubbish and false, including the ad hominem attacks. 

Unlike a power amplifier, the frequency response of the RIAA implies a deeper feedback at high frequencies. Is this kind of feedback deep enough to work properly?

@alexberger 

If in a discrete solid state circuit, maybe?? -a lot will depend on the semiconductors involved!! It can work OK with tubes, but if you really want to get it right, you run the amplification flat and use passive EQ. That way you can apply the feedback needed to do the job right.

I don’t know that the method by which a signal is transmitted in a transistor is any better than a transformer

A FET works more like a valve/tube.
If you like transimpedance (current based) amps, they are more than likely a BJT.

The problem you are up against using either device above is that the input side of the device is outside of the feedback loop. You will have a rather prodigious electrical peak, likely between 1-5MHz with most LOMC cartridges. It might be as much as 30dB depending on the Q value (how long as opposed to how wide) of the coil in the cartridge. That peak can be energized and easily overload the input despite the use of feedback.

So an SUT has the advantage of not being overloaded in this way and actually blocks the RFI generated in this fashion from reaching the phono stage input! That's a pretty clear advantage!

(The overload can cause ticks and pops as well as distortion which is perceived as brightness- hence the use of 'cartridge loading' resistors, which detune the electrical resonance, preventing it from going into excitation.)

If you're going to run solid state, you need to use an opamp to get around this problem, or set up the feedback look on the discrete devices in the same manner as used in with an opamp; essentially creating a low performance opamp in the process...

I used highly regarded Cinemag transformers with my Lyra Delos cartridge perfectly matched. The sound was energetic and loud but the treble was edgy and grainy.

This is the tricky bit about SUTs. This sounds like a classic situation where the loading on the output of the SUT wasn't addressed. Depending on the cartridge's source impedance, the 47K load that was probably stock in the preamp was likely not correct. This can result in distortion and the interwinding capacitance of the transformer playing a role like a capacitor in parallel with the transformer.

So not only would the result be distorted (likely causing harshness) but it might not be flat either! I can imagine this being quite disappointing. At any rate if the loading were addressed I suspect this situation could have been rectified without replacing anything.

Look, the main SUT limtation vs an active high gain SS alternative is its way limited  frequency bandwidth

If you are using opamps, you'll need a fair amount of feedback and that feedback will correct phase shift. So even though an opamp can be really wide bandwidth, it becomes less important because phase shift is minimized.

When you have a passive device or if the circuit is zero feedback, that's when you need the bandwidth in order to prevent phase shift. Now its well-known that the smaller you make an audio transformer and if that transformer does not have any DC in its core, its actually pretty easy to get wide bandwidth, often well past 100kHz. 

Put another way, the reason to have wide bandwidth is to get low phase shift in the audio band if you don't have any other method (such as feedback) to control it.

The concern IMO isn't the high end! its how well it goes low. But again with small audio transformers this is fairly easy to do.

Btw, what atmasphere posted was theory that today it just does not happens and all that that you can use balance cable connectuion to the phono stage because th SUT is bs

@rauliruegas Clearly you have no idea of what you are talking about.

Transformers are very good at converting from balanced to single-ended and vice versa. Jensen Transformers does a very good business on this aspect of transformers alone. Most SUTs are built for certain cartridges, and so have single-ended connections, but if the SUT in that box were examined closely, it would be seen that its actually a simple matter to set it up for balanced operation.

Here is how its done: The SUT has a total of four connections, two as input and two as output. There may also be a ground connection, which is connected to the core of the part (not needed if the transformer is bolted in place). You have to identify the input (the primary side) and the output (the secondary side). If you want a balanced input, tie one connection to pin 2 and the other to pin 3. Pin 1 of the XLR will be the case/core of the transformer and is where the ground connection from the tonearm will go. The tonearm cable will thus have the + and - outputs of the cartridge traveling in a twisted pair to pins 2 and 3; the tonearm ground becomes the shield of the cable.

You do have to be careful about phase. If you mix it up, one channel could be out of phase with the other, which will seem like a loss of bass impact (and if your system is very good at imaging, the music will seem to sit in the speakers rather than in space).

Raul, when you have the idea that you want to make someone else wrong, try to resist the feeling to post. Its obvious to many here that when you don’t resist that urge, what you write isn’t correct, with the motivation is really obvious. It does not become you or lend credibility.

you have often mentioned the notion that high gain phono input stages need to be designed to be insensitive to RFI.  What design elements contribute to that good behavior?  Is it simply a matter of limiting the bandwidth?

@lewm I wouldn't say its any one thing. I've found that bandwidth (on the RIAA curve) is a good idea up to about 100KHz (I have an anecdote about that which taught me the importance of this).

Beyond 100KHz you get into RFI issues from the cartridge. That might not be a problem if the phono section input can handle the RFI without overloading. This is much easier to do with tubes than it is with solid state! If using solid state at that point I would say yes, bandwidth limiting is a good thing. You would have to be careful that any RF energy can't get rectified by a non-linear problem though! So to deal with this problem you'll be using several techniques to sort it out.

I mentioned that this is easier to do with tubes; the reason is that if solid state there is often a feedback loop involved. Its possible for the portion of the circuit that is causing the problem to be outside the feedback loop. The reason for that can be subtle; for example you'd think an opamp using feedback would be immune to this problem since the feedback is applied outside of the opamp. But if the opamp lacks the bandwidth, you can have a situation where the RFI comes in but isn't corrected because its outside of the passband of the opamp. So it distorts. The trick there is likely to not ask so much gain of the opamp but you have to be aware of the RFI problem in order to get that far...

SUTs are tricky and they do have advantages.

The tricky bit is they have to be loaded correctly. Many SUTs are meant to be used with a specific cartridge; such SUTs as a result are meant to be loaded at their output by the 47K input impedance of the phono section (47K is the standard for phono input sections).

If the loading is different, for example the load is a higher impedance, the transformer can 'ring' (distort) and so will sound brighter. This can also happen if a different cartidge, with a difference source impedance is used. Transformers are call that because they transform impedance and this goes both ways: I can't be more emphatic that transformers do not isolate impedance!

Jensen Transformers makes very high quality SUTs and have several models, some meant to be used with tubes and others with solid state. Because they have a generic quality, to deal with the loading problem Jensen has published a chart that shows what resistor/capacitor combination should be at its output so as to prevent ringing.

The advantage of SUTs are several. First, they contribute almost no Johnson noise at all (which would be heard as hiss otherwise) and so can benefit both tube and solid state phono sections if a LOMC cartridge is being used. This is the most obvious benefit.

The next benefit is that SUTs, being transformers, allow you to run the input and/or output balanced or single-ended. In this manner you can minimize the sonic artifact that is caused by the tonearm cable; so those of you that spent a lot of money on the tonearm cable take note: if you also run an SUT you can go balanced from the phono cartridge (which is a balanced source) and so get better performance from the cable, which is arguably the most important place in the audio system that the cable really be right. Any place further downstream will not be able to make up for any deficiencies or colorations imposed by the cable! You can do this even if your phono section has a single-ended input.

Finally, SUTs usually do not have bandwidth much past 100KHz. For this reason, they can effectively block the RFI that is usually caused by the cartridge inductance being in parallel with the capacitance of the tonearm cable. People that don't use SUTs often resort to 'cartridge loading' resistors to get rid of the distortion caused by this problem, although they usually think they are tuning out brightness. What they don't realize is that the brightness is the result of distortion. Take away the RFI and the overload it causes to the phono section and the brightness is gone.

I've written plenty about the adverse effects 'cartridge loading' can cause and will not repeat myself here.

For those that don't use an SUT though, the RFI generated must be dealt with; its my theory that the reason there is an SUT vs direct in debate (for those of you who have preamps that have sufficient gain) has to do with whether the RFI is dealt with properly when running direct-in.

IME, most designers of phono sections do not take the phenomena of the electrical resonance/RFI problem of LOMC cartridges into account in their designs, so the design has problems with high frequency overload as result. But if that problem is dealt with, usually a phono section that can run direct-in will sound more transparent than using an SUT. This is simply because there won't be additional distortion.

In a nutshell what I'm saying is if you need the gain because your phono section only does high output cartridges, this is a good way to go. It might sound better than a poorly designed high gain phono section as well. But if the phono section is properly designed it goes the other way!

Ultimately the designer/dealer or whatever likely isn't going to tell you what's up with all this; IME if they don't know about the cartridge electrical resonance issue you'll get snowed. So you just have to try it and see what works.

And in case its not obvious, keep the interconnect cable capacitance as low as possible. This means don't use regular interconnects not meant for use with a phono cartridge!