>Granted distortion is additive but 0.1% addeed to several %?
If 0.1% is audible it will still be audible with a signal
already degraded by several %.
Think about the distortion inherent in loudspeakers.
(somebody have a typical or even 'best case' number ?)
But yet we can readily hear distortion somewhere else
in the chain down to 1 or even 0.5%
At 0.1% this may be a moot point, but conceptually
it is something worth keeping in mind.
If 0.1% is audible it will still be audible with a signal
already degraded by several %.
Think about the distortion inherent in loudspeakers.
(somebody have a typical or even 'best case' number ?)
But yet we can readily hear distortion somewhere else
in the chain down to 1 or even 0.5%
At 0.1% this may be a moot point, but conceptually
it is something worth keeping in mind.
>I can't say that a single input transformer
>will completely change the sound quality
>of an audio chain, but I have spent the
>last 40 years and more, trying to provide
>an alternative.
It would be fun to visit an alternate universe
where you had spent 40 years on xfmr design.
Perhaps we could plug our MC cartridge in
one side and our speakers on the other and
save some hassle 🙂
>will completely change the sound quality
>of an audio chain, but I have spent the
>last 40 years and more, trying to provide
>an alternative.
It would be fun to visit an alternate universe
where you had spent 40 years on xfmr design.
Perhaps we could plug our MC cartridge in
one side and our speakers on the other and
save some hassle 🙂
hitsware,
I agree with most of what you are saying, but sometimes we miss the forest for the trees. We sometimes take one spec. and beat it to death ane ignore everything else.
I am the first to admit that I am not a big fan of transformers, but sometimes they have their uses. In this case a transformer might be a valid alternatine.
Jam
I agree with most of what you are saying, but sometimes we miss the forest for the trees. We sometimes take one spec. and beat it to death ane ignore everything else.
I am the first to admit that I am not a big fan of transformers, but sometimes they have their uses. In this case a transformer might be a valid alternatine.
Jam
Yea.jam said:
IIRC (I haven't been near a turntable in years)
for MC pickups the xfmrs were better sounding
(smoother, musical, whatever)
EXCEPT ......
Had a tendency to pickup mains hum 🙁
My experiences were with a limited number
of devices though.
For what it's worth, here's an excerpt from Bill Whitlock's chapter on transformers in Glen Ballou's Handbook for Sound Engineers, Third Edition:
As background, it should be said that THD or total harmonic distortion is a remarkably inadequate way to describe the perceived awfulness of distortion. Distortion consisting of low-order harmonics, 2nd or 3rd for example, is dramatically less audible than that consisting of high-order harmonics, 7th or 13th for example. Consider that, at very low frequencies, even the finest loudspeakers routinely exhibit harmonic distortion in the range of several percent at normal listening levels. Simple distortion tests whose results correlate well with the human auditory experience simply don't exist. Clearly, such perceptions are far too complex to quantify with a single figure.
One type of distortion which is particularly audible is intermodulation or IM distortion. Tests frequently use a large low-frequency signal and a smaller high-frequency signal and measure how much the amplitude of the high frequency signal is modulated by the lower frequency. Such inter-modulation creates tones at new, non-harmonic frequencies. The classic SMPTE (Society of Motion Picture and Television Engineers) IM distortion test mixes 60 Hz and 7 kHz signals in a 4:1 amplitude ratio. For virtually all electronic amplifier circuits, there is an approximate relationship between harmonic distortion and SMPTE IM distortion. For example, if an amplifier measured 0.1% THD at 60 Hz at a given operating level, its SMPTE IM distortion would measure about three or four times that, or 0.3% to 0.4% at an equivalent operating level. This correlation is due to the fact that electronic non-linearities generally distort audio signals without regard to frequency. Actually, because of negative feedback and limited gain-bandwidth, most electronic distortions become worse as frequency increases.
Distortion in audio transformers is different in a way which makes it unusually benign. It is caused by the smooth symmetrical curvature of the magnetic transfer characteristic or B-H loop of the core material shown in Figure 9. The non-linearity is related to flux density which, for a constant voltage input, is inversely proportional to frequency. The resulting harmonic distortion products are nearly pure third harmonic. In Figure 18, note that distortion for 84% nickel cores roughly quarters for every doubling of frequency, dropping to less than 0.001% above about 50 Hz. Unlike that in amplifiers, the distortion mechanism in a transformer is frequency selective. This makes its IM distortion much less than might be expected. For example, the Jensen JT-10KB-D line input transformer has a THD of about 0.03% for a +26 dBu input at 60 Hz. But, at an average equivalent level, its SMPTE IM distortion is only about 0.01% -- about a tenth of what it would be for an amplifier having the same THD.
se
As background, it should be said that THD or total harmonic distortion is a remarkably inadequate way to describe the perceived awfulness of distortion. Distortion consisting of low-order harmonics, 2nd or 3rd for example, is dramatically less audible than that consisting of high-order harmonics, 7th or 13th for example. Consider that, at very low frequencies, even the finest loudspeakers routinely exhibit harmonic distortion in the range of several percent at normal listening levels. Simple distortion tests whose results correlate well with the human auditory experience simply don't exist. Clearly, such perceptions are far too complex to quantify with a single figure.
One type of distortion which is particularly audible is intermodulation or IM distortion. Tests frequently use a large low-frequency signal and a smaller high-frequency signal and measure how much the amplitude of the high frequency signal is modulated by the lower frequency. Such inter-modulation creates tones at new, non-harmonic frequencies. The classic SMPTE (Society of Motion Picture and Television Engineers) IM distortion test mixes 60 Hz and 7 kHz signals in a 4:1 amplitude ratio. For virtually all electronic amplifier circuits, there is an approximate relationship between harmonic distortion and SMPTE IM distortion. For example, if an amplifier measured 0.1% THD at 60 Hz at a given operating level, its SMPTE IM distortion would measure about three or four times that, or 0.3% to 0.4% at an equivalent operating level. This correlation is due to the fact that electronic non-linearities generally distort audio signals without regard to frequency. Actually, because of negative feedback and limited gain-bandwidth, most electronic distortions become worse as frequency increases.
Distortion in audio transformers is different in a way which makes it unusually benign. It is caused by the smooth symmetrical curvature of the magnetic transfer characteristic or B-H loop of the core material shown in Figure 9. The non-linearity is related to flux density which, for a constant voltage input, is inversely proportional to frequency. The resulting harmonic distortion products are nearly pure third harmonic. In Figure 18, note that distortion for 84% nickel cores roughly quarters for every doubling of frequency, dropping to less than 0.001% above about 50 Hz. Unlike that in amplifiers, the distortion mechanism in a transformer is frequency selective. This makes its IM distortion much less than might be expected. For example, the Jensen JT-10KB-D line input transformer has a THD of about 0.03% for a +26 dBu input at 60 Hz. But, at an average equivalent level, its SMPTE IM distortion is only about 0.01% -- about a tenth of what it would be for an amplifier having the same THD.
se
Let's use transformers, everyone. It will make everyone happy and contented. I will save my poor efforts for paying customers, wherever they may be. SY is right, transformers are beautiful, and fix RFI and ground loops too.
john curl said:As I recall, 1 part per 1000 is 0.1%. That is a common number on the Jensen transformer data sheet. Can I rub your nose in it even further?
John,
MC transformers, when done right are a lot better than you are
giving credit. Take the Jensen JT346 range, the 20Hz LF distortion at
typ MC OP levels is 10x lower than you suggest - 0.01%. At 50Hz it
is 100 x lower - .001%. With a prim R (3 in parallel) of 0.643 ohms,
you can see that they do offer the lowest possible noise
configuration. There's no argument about it. I also know how to do
all those noise calculations just as you do.
The problem with transformers is that this level of performance just
costs too much money for most commercially viable applications.
As you well know, there's a whole lot of circuitry that can be made
for the price of one of those Jensens.
The other problem is that 95% of transformers don't sound as
transparent as these Jensens. Did you have a listen to the wav files
I posted of mic transformer comparisons? All these transformers
sound different - and only one can be closest to correct.
Steve's excerpt from Bill W. WRT transformer IMD is right on.
OK, (slight) rant over, there's enough here without me.
cheers
T
I am reading from the Jensen JT-34k-dx spec sheet. .1% at 20Hz is normal at almost all levels.
Amazing, there's more than one grade of transformer!
Let's be fair, though- to determine noise, you also have to add in the stage that the transformer drives. It won't output a universally-useful signal, it will need to be terminated properly and either be buffered or drive further high input impedance amplification..
Let's be fair, though- to determine noise, you also have to add in the stage that the transformer drives. It won't output a universally-useful signal, it will need to be terminated properly and either be buffered or drive further high input impedance amplification..
john curl said:
Yes, the JT 34k is a 1:37 step up ratio.
Anyone who knows transformers will be aware that it is impossible
to get really high performance from such a ratio at the IP Z range,
and OP level of a MC.
The JT 346 is 1:4 or 1:12 ratio, depending on configuration.
The only application that would be able to use a 1:37 ratio and still
get very high performance is a ribbon mic front end. With the
ribbons ultra low source Z, signal level and appropriately designed
TX. As an example I believe the Royer SF12, (which I have designed
mic pre's for), has around 1:40 step up ratio. It may even be an
auto former, although I'm not sure.
cheers
T
john curl said:
Maybe try sticking some Bybees in your circuit. They're claimed to reduce noise. That was their whole raison d'etre for the classified submarine sonar, no? If they can reduce the noise in a sonar system, seems they'd be able to reduce the noise of your MC preamp. Perhaps they can get your noise figure down to 1.6dB, or even less.
se
Steve Eddy said:
This describes what I hear when a transformer is inserted into the signal path. Additionally, The distortion may fill out the sound, etc. but the resolution floor will always be compromised by the ability to completely couple all of the signal from the primary to the secondary as the level drops. MC cartridges are the worst.
There I go speaking in tongues again. Pay it no mind.
Back to the distortion discussion.
By the way, can anyone actually describe the affect on the resultant sound caused by the various distortions discussed at length on this topic?
Sorry, couldn't stop myself. Back to sleep.
Steve Eddy said:
The Bybee effect is level sensitive as well. I've taken them apart and measured them.
john curl said:
Why keep obsessing over a number as if you're making instrumentation equipment? Instead of obsessing over numbers, why not consider what it really means at the end of the day? You know, with a human being, in their home, listening to reproduced music. Or does that simply not factor into the equation?
se
Steve Eddy said:
Removal of noise in preference to signal in the same BW. Violation of first principles, Claude Shannon for one. I'll bet someone in Russia can buy them, I can't even ship my 20yr. old Tek scope out of the country.
This is not a hobby circuit post.
Terry Demol said:
Not quite sure what you mean by "commercially viable." Do you mean something that's not likely to be found on the shelves at Circuit City or Best Buy?
Also, regardless of definition, of what relevance is "commercial viability" in a discussion on a forum dedicated to DIY?
For what it's worth, CineMag's CMQEE-3440A, which sells for less than half the price of the Jensen JT-34K-DX, has been very well received and CineMag has sold quite a lot of them to DIYers.
se
scott wurcer said:
Well, obviously your 20-year-old Tek scope wasn't a piece of classified technology used in the sonar systems of nuclear submarines. That stuff you can send anywhere you want.
se
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