Step Up Transformers? Pros / Cons?

[SIY]

Did you add any load resistors to your Lundahl / K&K kit?

The cartridge does not need to be loaded. This is a major myth when it comes to MCs- they're almost a pure source resistance, and there's low reciprocity so loading won't significantly affect damping. The SUT secondary loading is far more critical since its source impedance has high inductance.

 

[orangejello]

The cartridge does not need to be loaded. This is a major myth when it comes to MCs- they're almost a pure source resistance, and there's low reciprocity so loading won't significantly affect damping. The SUT secondary loading is far more critical since its source impedance has high inductance.

I think that what is being asked is "did you add any [SUT secondary] load resistors..." The K&K SUT allows the user to add secondary resistors, not cartridge load resistors. But thanks for clarifying that point. I think the confusion is largely a matter of imprecise terminology. I am sure that I have said that I was "loading the cartridge" when I should have said that I was "loading the secondary".

To his point though, yes you must almost certainly add load resistors. If you don't have a scope, you can consult the vinylengine.com database to find out what the optimal secondary loading ought to be according to the manufacturer. If you don't do this properly you will probably get ringing due to what I think of as inadequate damping (not sure if that is correct terminology) - the sonic consequences of which are usually exaggerated high frequency which can be somewhat irritating from a psycho-acoustic POV.

The secondary load resistors are usually in parallel with a 47K resistor at the input of a MM phono pre-amp. So don't make the mistake of adding a 100 ohm resistor (or whatever is the value of the optimum load for on the secondary for your cartridge). You either have to do a little math, or consult K&K cheat sheets that K&K provides for your SUT and which assumes that your MM phono pre-amp has a 47k resistor at the input.

SIY, please correct this as necessary. I am marginally technical and don't think about this stuff very frequently once things are dialed in.

 

[watchnerd]

I think that what is being asked is "did you add any [SUT secondary] load resistors..." The K&K SUT allows the user to add secondary resistors, not cartridge load resistors. But thanks for clarifying that point. I think the confusion is largely a matter of imprecise terminology. I am sure that I have said that I was "loading the cartridge" when I should have said that I was "loading the secondary".

To his point though, yes you must almost certainly add load resistors. If you don't have a scope, you can consult the vinylengine.com database to find out what the optimal secondary loading ought to be according to the manufacturer. If you don't do this properly you will probably get ringing due to what I think of as inadequate damping (not sure if that is correct terminology) - the sonic consequences of which are usually exaggerated high frequency which can be somewhat irritating from a psycho-acoustic POV.

The secondary load resistors are usually in parallel with a 47K resistor at the input of a MM phono pre-amp. So don't make the mistake of adding a 100 ohm resistor (or whatever is the value of the optimum load for on the secondary for your cartridge). You either have to do a little math, or consult K&K cheat sheets that K&K provides for your SUT and which assumes that your MM phono pre-amp has a 47k resistor at the input.

SIY, please correct this as necessary. I am marginally technical and don't think about this stuff very frequently once things are dialed in.

That's correct -- I was asking about the secondary, optional add-on parallel resistors, to the board in the K&K /Lundahl SUT.

So did you add any?

 

[watchnerd]

The cartridge does not need to be loaded. This is a major myth when it comes to MCs- they're almost a pure source resistance, and there's low reciprocity so loading won't significantly affect damping. The SUT secondary loading is far more critical since its source impedance has high inductance.

In this context, it's the SUT secondary I'm asking about.

The K&K SUT PCB has space for parallel through-hole resistors with values of the user's / builder's choice.

 

[orangejello]

That's correct -- I was asking about the secondary, optional add-on parallel resistors, to the board in the K&K /Lundahl SUT.

So did you add any?

Yes. Every MC cartridge I have used needed them. Without them most MC cartridges sound tinny due to high frequency ringing.

I bought a bunch of high quality, tight tolerance tantalum resistors quite awhile back when they were fairly readily available. Seems like they became hard to get at some point. In any case, they were said to have some nice electrical characteristics so I bought those. My version of the Premium SUT had a place to plug in the resistors without solder. So it was easy to switch them around until you got the right values. Then you could drop in a bit of solder. I nevered bothered since the mechanical connection was very tight.

 

[watchnerd]

Yes. Every MC cartridge I have used needed them. Without them most MC cartridges sound tinny due to high frequency ringing.

I bought a bunch of high quality, tight tolerance tantalum resistors quite awhile back when they were fairly readily available. Seems like they became hard to get at some point. In any case, they were said to have some nice electrical characteristics so I bought those. My version of the Premium SUT had a place to plug in the resistors without solder. So it was easy to switch them around until you got the right values. Then you could drop in a bit of solder. I nevered bothered since the mechanical connection was very tight.

Wow, I had no idea that "audiophile" resistors was a thing:

https://www.hificollective.co.uk/components/an_tantalum_nonmagnetic.html

10 British pounds for 1 resistor?!!??!!

Perhaps you used more ordinary versions?

 

[DonH56]

You can find "audiophile" versions of most anything including RLC passive components. Ironically some of the most-touted audiophile stuff actually has worse electrical performance from an engineering point of view. But of course engineering is pooh-poohed by the golden-eared crowd.

 

[audiopile]

One of my great disappointments was that within the pile -o-goldplatedcr@p that is audiophile products (my favorite :gold plated plastic Toslink cables -every once in awhile some fashionable audiophile product actually DOES make a difference (not counting those that are both very expensive and really lousy sounding- common IMO). My list is probably short : Telefunken ECC-83 tubes - it's been a number of years since I owned any equipment that uses 'em -but I'm hoarding what I've got. Very few Black Gate capacitors in specific locations are noticeable in a good way and I've bought DOA stuff in order to steal these caps out of them for future use. But it's made from expensive materials or even better - it's old and hard to find -can't think of exactly how that improves what goes thru it ?

 

[orangejello]

10 British pounds for 1 resistor?!!??!!

Perhaps you used more ordinary versions?

I bought them a long time ago. They were Japanese. The were a bit more expensive than garden variety but not ridiculous. They had very good tolerances. Not sure if there is an audible difference. I would just get a some metal film resistors. Setting the correct load is far more important than resistor material.

 

[watchnerd]

My list is probably short : Telefunken ECC-83 tubes - it's been a number of years since I owned any equipment that uses 'em -but I'm hoarding what I've got.

In my experience, tube rolling can make a difference (even within the same model types) because tubes are not uniform in their designs, all have measurable variations, and are all imperfect and defective to one degree or another (not to mention going bad over time). However, it's also a route to madness.

Case in point, last night I hooked up the K&K SUT and listed to the same album side 3 times in a row while swapping in different 6DJ8/6692/7308 tubes into my Fi Yph, which I hadn't listened to in years:

All 3 tubes sounded different, especially in the treble / cymbal region.

 

[watchnerd]

I bought them a long time ago. They were Japanese. The were a bit more expensive than garden variety but not ridiculous. They had very good tolerances. Not sure if there is an audible difference. I would just get a some metal film resistors. Setting the correct load is far more important than resistor material.

Is there a way to buy quality individual resistors at a price per unit that isn't nuts?

It seems the easiest route is to just buy one of those "variety packs" of 1-5% resistors, which typically has like 200+ resistors for $10 or so.

 

[DonH56]

Be careful buying components packs expecting to self-match to higher tolerance. I did that ages ago, bought a bag of 10% or 20% resistors figuring I could just sit down and find some at 1% or better. Thing is, they are sorted at final test, and ones within 1% are all sorted into the 1% tolerance containers so there aren't any 1% Rs (or Cs) in the 10% bag. Duh, obvious after the fact. You can usually find some that will match relatively to 1% or whatever, though their absolute values may be 10% off, but variance tends to get higher so it's a crap shoot.

Also note not all metal films are the same, just as not all capacitor dielectrics are the same. Some have lower noise, some better temperature or voltage coefficients, etc. I remember when thick film metal film Rs became the rage in the 1980's or so. They could often be had with lower (but sometimes much higher) tempcos but most had higher self-noise than a good carbon-film resistor.

I've told the story before, and someone actually found a picture for me and posted on one the other audio fora, of a preamp (I think) that touted "metal film resistors" and had a little circuit board near the top of the perforated-metal enclosure that prominently displayed them. Thing is, they were not actually connected to anything...

 

[watchnerd]

Read this today:

"But there’s yet another advantage of using a transformer rather than an active step-up device, which involves the type of distortion produced by both (and all step-up devices will introduce distortion to the audio signal. Whereas an active device has a fairly constant resistive input impedance, the input impedance of a step-up transformer is frequency dependent. This has the effect that any harmonic distortion produced by a step-up transformer is highest at the lowest frequencies and drops as the frequency rises, whereas in most active step-up devices distortion increases as the frequency rises. (There are, of course, exceptions… but they’re usually very expensive exceptions!)"

https://www.avhub.com.au/product-re...31-moving-coil-transformer-review-test-490591

It this true?

If so, from what I remember about pyschoacoustics, we're less sensitive to distortion at low frequencies than high frequencies.

Would this provide a psychoacoustic / subjective benefit for SUTs?

 

[DonH56]

LF saturation is a normal characteristic of transformers. There are also HF distortion mechanisms, natch. It is one of many variables in choosing a step-up device (active or passive). I can't speak to the subjective aspects.

 

[Blumlein 88]

https://jensen-transformers.com/wp-content/uploads/2014/09/Audio-Transformers-Chapter.pdf

Read page 5. It fits with what you are saying. The permeability effects how easily saturated an xfmr is, and permeability varies inversely with frequency. As you begin to get near saturation distortion will rise.

EDIT Don beat me to it by a minute.

 

[watchnerd]

LF saturation is a normal characteristic of transformers. There are also HF distortion mechanisms, natch. It is one of many variables in choosing a step-up device (active or passive). I can't speak to the subjective aspects.

https://jensen-transformers.com/wp-content/uploads/2014/09/Audio-Transformers-Chapter.pdf

Read page 5. It fits with what you are saying. The permeability effects how easily saturated an xfmr is, and permeability varies inversely with frequency. As you begin to get near saturation distortion will rise.

EDIT Don beat me to it by a minute.

Okay, so true....but by how much of a difference vs active ("it depends...") is ill-defined and how much it psychoacoustically it might matter is untested and unknown`....

 

[levimax]

Is there a way to buy quality individual resistors at a price per unit that isn't nuts?

It seems the easiest route is to just buy one of those "variety packs" of 1-5% resistors, which typically has like 200+ resistors for $10 or so.

Good quality 1/4 watt 1%/metal film resistors are less than $1.00 for 10 or less than $.25 if bought individually. Good quality caps in the range required for @ SUT secondary network are only about twice that much. The cost of an assortment of values to tune a SUT secondary network is not a problem.

 

[watchnerd]

Update:

I'm now past the recommended 48 hour break-in period, so I thought it was time to post an update.

Configuration:

-No extra resistors added in parallel, so the cart (AT33EV) should be see a theoretical reflected load of 183 ohms. The default setting for AT33EV with the Devialet Expert is 200 ohms, so I'm going to consider this 9% variance to be "close enough" to make valid comparisons given all the other variables and vagaries of vinyl playback.

-The SUT is set for 1:16 / 24 dB gain. The cartridge outputs 0.3mV

-Following @SIY 's calculation of 4.3mV stepped up output, I set the Devialet MM input for 4.7mV, which gives a 10% margin of error to help prevent clipping / overload

Observations vs going direct into the Devialet Expert MC stage:

Things I'm Sure Are Different:

-The noise floor / hiss has dramatically dropped. I didn't bother measuring it because it's obvious to the naked ear. At -20 dB I can't hear any hiss unless I stick the tweeters in my ear, and even then it's faint. At 0 dB I can hear hiss if I kneel in front of the speakers, angle my ear towards them from 12" or so away. In my listening seat 15' away I can't hear anything.

Things That Might Be Different (but I'll have to do some vinyl rips to know my memory isn't fooling me):

-Dynamics might be a little better. This doesn't seem crack smokingly insane if the output voltage is dramatically higher....but it might be nonsensical from a physics POV.

-Bass seems different. This seems right on the edge of psychoacoutically fooling myself (I'll have to rip to know for sure), but it seems slightly less taut, slightly more lush.

-LP surface noise seems less. How could this be? Would active gain amplify LP surface noise in a way that a SUT does not? That makes little sense to me. Is it a "loss of detail / resolution"? If so, I don't notice it on music. This could just be either my imagination or a coincidence that I've recently played a lot of virgin vinyl.

-It maybe...maybe...(I hesitate to even write this because it sounds ludicrous)...sounds slightly more like tape with a little less of the mechanical resonances that come with LP. But I'm not sure how this could possibly be true unless somehow the different electrical loading / circuit is changing the energy path in the system? But that sounds infinitesimally small, even if hypothetically possible, so I'm probably just imagining it.

If I get some time, I might make some rips if I can find a good place to post files.

 

[watchnerd]

LF saturation is a normal characteristic of transformers. There are also HF distortion mechanisms, natch. It is one of many variables in choosing a step-up device (active or passive). I can't speak to the subjective aspects.

I'm wondering if LF saturation would account for the (possibly imagined) difference in bass character that I think I'm hearing.

 

[Soniclife]

If I get some time, I might make some rips if I can find a good place to post files.

I'd be interested if you find the time.