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What makes Inductor EQs sound different?
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ryansupak
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14th November 2012
Old 14th November 2012
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What makes Inductor EQs sound different?

Hi, I've got a few EQ's and Inductor EQs are my favorite, for purely aesthetic reasons.

It seems like most of the basic audio filter circuit building blocks can be realized with any two of the three of: Resistors, Capacitors, Inductors -- and Inductors tend to be the most expensive and noise-prone. Inductors, of course, are coming back into fashion.

Just what is it, though, that makes them sound different? I have read a few statements on it but have not seen them verified:

1) Inductors can saturate.
2) The turnover point of an inductor can shift in a program-dependent fashion if a high-level signal is fed through it.
3) Inductors can compress heavy bass signals.

Does anybody have insight into this?

Thanks,
rs
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14th November 2012
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wherever you find inductors some sound magic is going on.. why? good question..
I definitely dont know enough about it.. but have seen wonderfull sounding machines where big inductors played a major role for the sound..

saturation is maybe/probably a point..But there is more going on..depends on the circuit.. The inductor a frequency depended resistor.. as lower the frequency as more current can be drawn....I ve heard that they have a specific phase response that is opposite to the one of an capaciator. So brilliant designers can use them to create very phase stable amps.. The old Siemens guys was into such kind of tricks..
Interesting stuff.. but way above my limited electronics knowledge..

In equalizers big inductors allow the use of small capaciators.. and as it looks..as smaller the involved caps and bigger the inductors.. as fatter the sound.. See the moog filterbank for this..

In any case its easier to get high quality caps in low values.. while inductors are way more expensive than capaciators.. So moog made here not a economic decision.. Same filter bank could have been realized with much smaller inductors for a lower price, but than bigger capaciators.....

Thats was already about all i know about them.. when you see some in an audio circuit you better leave them where they are.. Expensive parts are not used for fun...
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15th November 2012
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There's no clear answer to this.

After working with the subject for some years, I have no conclusion.

My best guess is that there are some program dependent nonlinearities going on in the magnetic domain - unintended stuff that our ears happen to like a lot.

Probably because of having some psychoacoustic resemblance to specific by-products of the human auditory system.

And possibly also a bit of added cultural bias for many of us, because we have used and loved analogue tape, which also has some of these artifacts.

If I could pinpoint exactly what, why, and how we like this - I'd be very rich :-)

Until then, I'll just continue building stuff using the technology that makes my ears most happy - in this case large inductors in EQ's...

Jakob E.
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15th November 2012
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Thanks for the replies. What you folks are saying is more or less the conclusion I've come to for now. It seems like because an inductor is a "natural LPF" in the same way that a capacitor is a "natural HPF" you get all the complex (near-infinite?) facets of a purely physical response "for free". I didn't know if the big ones sounded better but they sure look cooler... rs
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15th November 2012
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Well, we can get it this way: if we're not using inductors in EQs, we tend to use gyrators, which are substitute for inductors, but with all "great" stuff that more complex circuit can bring, distortions is what first comes to mind, but i think engineers can tell us about all side effects more clearly.

So, it is not that EQs with inductors sounds good, it is bad designed EQs without inductors sounds bad.

BTW, there's also passive EQ circuits without inductors and without gyrators, like those in guitar amps and old radios, and they're sound very clean too, just like the inductor-based ones. I have a dream to make a small console with all-passive EQs in it, meanwhile i've built a preamp with 3-band passive EQs, and all these modern guys just shocked how great EQ can work - +20dB on bass without any unpleasant artefacts, crystal clear highs...
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16th November 2012
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Quote:
Originally Posted by zvukofor View Post
Well, we can get it this way: if we're not using inductors in EQs, we tend to use gyrators, which are substitute for inductors, but with all "great" stuff that more complex circuit can bring, distortions is what first comes to mind, but i think engineers can tell us about all side effects more clearly.

So, it is not that EQs with inductors sounds good, it is bad designed EQs without inductors sounds bad.

BTW, there's also passive EQ circuits without inductors and without gyrators, like those in guitar amps and old radios, and they're sound very clean too, just like the inductor-based ones. I have a dream to make a small console with all-passive EQs in it, meanwhile i've built a preamp with 3-band passive EQs, and all these modern guys just shocked how great EQ can work - +20dB on bass without any unpleasant artefacts, crystal clear highs...
Yeap here it is, gyrators vs inductors, which basically boils down to the same old active vs passive circuitry debate. One could argue that gyrators are the analog version of an "inductor emulation plug-in" e
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16th November 2012
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Well, i'd not say same thing about plugins as of gyrators, as good designed digital stuff much more clean than analog, it is just a matter of design, we have a lot of awful digital stuff, the same with analog. Hate all those myths about digital processing out here and there.
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16th November 2012
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Same reason as expensive transformer stuff sounds good, I imagine. Low freqency saturation!
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16th November 2012
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cool thread.
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16th November 2012
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It's always striking to me how much better analog drum generating circuits using big inductors sound, even compared to otherwise fully discrete ones. The dynamic behaviour is far more punchy, and the sonic signature a lot richer, natural and satisfying. It would be nice to know what is actually going on.
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This may have been mentioned already but the TYPE of circuit no doubt plays a big role in the "Sound", Passive vs active, how the inductors are used in both types..
I designed/built a 500 series Inductor Eq, Really like it on LF best..
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16th November 2012
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Quote:
Originally Posted by ryansupak View Post
Hi, I've got a few EQ's and Inductor EQs are my favorite, for purely aesthetic reasons.

It seems like most of the basic audio filter circuit building blocks can be realized with any two of the three of: Resistors, Capacitors, Inductors -- and Inductors tend to be the most expensive and noise-prone. Inductors, of course, are coming back into fashion.

Just what is it, though, that makes them sound different? I have read a few statements on it but have not seen them verified:

1) Inductors can saturate.
Yes a low frequency/level dependent distortion.
Quote:
2) The turnover point of an inductor can shift in a program-dependent fashion if a high-level signal is fed through it.
I'm not sure I follow this...Some temperature dependance due to wire resistance changing. Nonlinearity with current due to imperfect magnetic media, not familiar with any tube-like bias shift transiently with signal.

Another unique characteristic of inductors is that magnetic fields from closely spaced and unshielded inductors could interact, again causing deviations from predicted response.
Quote:
3) Inductors can compress heavy bass signals.
Compression is a pretty generous way to describe saturation distortion. While tape saturation was widely used selectively on some types of sources.
Quote:
Does anybody have insight into this?

Thanks,
rs
Perhaps of value as an "effect" to selectively add distortion to band passed LF fractions (band passed by EQ topology) of a wide band signal. Distorted LF signals can sound better than same amount of distortion to mid or high frequency signals due to human hearing's weaker discrimination of low frequency sounds.

====
A lot of the discussion seems to be confusing EQ topology, of which there are several, and passive component behavior.

Pursuing obscure distortions, seems to be good sport for studio engineers. Game on.

JR
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16th November 2012
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Quote:
Originally Posted by zvukofor View Post
Well, i'd not say same thing about plugins as of gyrators, as good designed digital stuff much more clean than analog, it is just a matter of design, we have a lot of awful digital stuff, the same with analog. Hate all those myths about digital processing out here and there.
OMG One cant tell a joke anymore
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17th November 2012
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Originally Posted by mixerguy View Post
cool thread.
I couldn't agree more.
rs
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17th November 2012
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The inductor can store energy, but compared to capacitor, does so in a different form. I am not sure about it, but since the inductor core becomes magnetized, the opposite pole might encounter less resistance, and present a new signal.
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17th November 2012
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Originally Posted by OpusOfTrolls View Post
The inductor can store energy, but compared to capacitor, does so in a different form. I am not sure about it, but since the inductor core becomes magnetized, the opposite pole might encounter less resistance, and present a new signal.
Indeed capacitors store energy as charge, and inductors as a magnetic field. However audio is AC so there should be no net magnetic field to magnetize metal parts one way or the other.

JR
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18th November 2012
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Quote:
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Indeed capacitors store energy as charge, and inductors as a magnetic field. However audio is AC so there should be no net magnetic field to magnetize metal parts one way or the other.

JR
How would you explain saturation?
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18th November 2012
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When I heard a 1073 and a 1084 EQ I was blown away, especially on the low end and some of the midrange. I ended up designing a 1 board clone out of this obsession.

Let's not forget that the inductor sections are passive and the amps before and/or after those parts also affect the sound some. So I think it is a marriage of both the active and passive.

Cheers

Jim
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18th November 2012
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Quote:
Originally Posted by OpusOfTrolls View Post
How would you explain saturation?
Saturation is when all the magnetic domains in the media are already pointing one way or the other, so the magnetic field can no longer be increased.

For capacitors a similar, but not exactly the same, mechanism is breakdown voltage, where no more voltage can be added without the capacitor failing.

JR
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18th November 2012
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Originally Posted by JohnRoberts View Post
Saturation is when all the magnetic domains in the media are already pointing one way or the other, so the magnetic field can no longer be increased.

For capacitors a similar, but not exactly the same, mechanism is breakdown voltage, where no more voltage can be added without the capacitor failing.

JR
Yep.
...And of course, EQs designed with inductors also use capacitors as well.

The basic idea of an L/C circuit is that capacitors "chop off" the lower frequencies as a function of their values, and that inductor coils "chop off" the highs. ...Or "choke" them, as the old-timers would say. (That's why inductors were called "chokes" in the old days.)

...And as many variables in as there are the idiosyncrasies of different capacitors, there are even MORE idiosyncrasies with different coils.

The choice of core material makes a difference. The choice of wire used makes a difference. The way the coil is wound makes a difference, and so forth and so on...

With coils, what you really have is sorta like "half of a transformer". ...And what alot of folks don't always grasp is that transformers don't just affect what is "passed through them", but that also the primary and secondary coils of a transformer interact not only with eachother, but also with the circuits on each side of the gap between the coils. (Hence the "transformer mojo" effect.)

So putting an inductor in a circuit has almost as much effect upon things in some circuits as would a transformer.

...And all of these things are also quite interactive with one-another, as well.

There is a whole helluva lot going on with regard to the various non-linearities introduced by the use of inductive coils in conjunction with capacitors, too; all very interactive with all the other components, and also myriad in complexity, and highly dependent upon choice of materials, design, and layout of parts.

Obviously, with so many variables (and uncertainties) involved, the possibilities are enless.

...Of course, when we finally get tired of analyzing all this crap, we just call it "MOJO".
.
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18th November 2012
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Quote:
Originally Posted by 12ax7 View Post
Yep.
...And of course, EQs designed with inductors also use capacitors as well.

The basic idea of an L/C circuit is that capacitors "chop off" the lower frequencies as a function of their values, and that inductor coils "chop off" the highs. ...Or "choke" them, as the old-timers would say. (That's why inductors were called "chokes" in the old days.)

...And as many variables in as there are the idiosyncrasies of different capacitors, there are even MORE idiosyncrasies with different coils.

The choice of core material makes a difference. The choice of wire used makes a difference. The way the coil is wound makes a difference, and so forth and so on...

With coils, what you really have is sorta like "half of a transformer". ...And what alot of folks don't always grasp is that transformers don't just affect what is "passed through them", but that also the primary and secondary coils of a transformer interact not only with eachother, but also with the circuits on each side of the gap between the coils. (Hence the "transformer mojo" effect.)

So putting an inductor in a circuit has almost as much effect upon things in some circuits as would a transformer.

...And all of these things are also quite interactive with one-another, as well.

There is a whole helluva lot going on with regard to the various non-linearities introduced by the use of inductive coils in conjunction with capacitors, too; all very interactive with all the other components, and also myriad in complexity, and highly dependent upon choice of materials, design, and layout of parts.

Obviously, with so many variables (and uncertainties) involved, the possibilities are enless.

...Of course, when we finally get tired of analyzing all this crap, we just call it "MOJO".
.
I would not disagree that magnetic field leakage from coil to coil would play a part in the sound. It is an interesting topic.
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19th November 2012
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I would not disagree that magnetic field leakage from coil to coil would play a part in the sound. It is an interesting topic.
Hmmm...

That's not really what I was driving at.

What I was talking about was the hysteresis characteristics of coils, and their effects upon the (non-)linearity of the circuit.

...But now that you mention it, it makes me wonder if some of what you're talking about may be going on as well.
.
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19th November 2012
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Hi
I think 12ax7 is sumarising this pretty well although a summary should be making the statement smaller not larger!
Gyrators can simulate an 'idealised' inductor up to the point where the amplifiers 'clip' or run into other boundaries, whereas a real inductor will start to either saturate at high signal level, or exhibit hysteresis at low level signals.

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19th November 2012
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Hmmm...

That's not really what I was driving at.

What I was talking about was the hysteresis characteristics of coils, and their effects upon the (non-)linearity of the circuit.

...But now that you mention it, it makes me wonder if some of what you're talking about may be going on as well.
.
You were talking about transmission line effects?
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20th November 2012
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maybe the process thru inductor is just closer to how soundpressure waves are transported thru air and that gives a more natural sound to the brain.
But that in way that something gets added to the sound.. really not a transparent process.

Inducter eq´s have somekind of a rejuvenating quality on audio sources.. That gets most realizable when you apply them on rather dead sounding digital soundsources that cant hide their arteficial nature. Flat 2 dimensional sounding soundsources get a 3 dimensional body again.. the sound gets more entity.
Thats how it appeared to me sofar.
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20th November 2012
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Quote:
Originally Posted by OpusOfTrolls View Post


You were talking about transmission line effects?

Well, I'm trying to avoid "digging a pit" here:

What I was trying to get at was that coils don't just affect the frquency response of what is "passed through them", but that they also exhibit what is known as "magnetic hysteresis", the effects of which are very complex, and (to make matters even more complicated) are also interactive with the surrounding circuitry (including the pots you're twisting).

So when you go twisting the knobs, a whole lot more changes than just the frequency response.

...In fact, a whole lot of stuff is going on even BEFORE you begin twisting knobs (which is why folks will sometimes put a pair of Pultecs across the two-bus with all the knobs set to "no change", and then marvel at what it does to the the low-end/high-end, etc.).

...But I'm not really an expert on this stuff (although I have a pretty comprehensive ignorance of the subject), so I was actually kinda hoping that someone who was a little more of a GeekSlut than myself might chime in and explain it better.

The trouble with trying to explain this sorta thing is that the more fully, completely, and accurately stuff like this is explained, the more it causes eyes to glaze over.

Sometimes it even gets to the point where I get the feeling that the only way to understand a technical explanation is if I already know as much about the subject as did the writer!
...Which is why I guess I will once again revert to the use of the word "mojo".
...Anyway, if you care to delve into more of what I'm (kinda lamely) going on about, you might start by taking a look here:
Magnetic Hysteresis - Wikipedia
.
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20th November 2012
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maybe the process thru inductor is just closer to how soundpressure waves are transported thru air and that gives a more natural sound to the brain.
Maybe. But how?
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20th November 2012
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Maybe. But how?
ask tesla... seems that he was a bit further down the road regarding the topic..

transformers are inductors too. and their side fx are pleasing to the ear too..

And as all emulations sofar fail to get that right, one could get the idea that there is more to the equation than there is known yet..or at least put in relation to audible fx.

When you send a digital track thru a transformer treatment and back into the digital domain it sounds dispite the two extra conversions still way more like transformer treated as any simulation plug i ve heard yet could do.
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22nd November 2012
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Originally Posted by audioconsult View Post
ask tesla... seems that he was a bit further down the road regarding the topic..

transformers are inductors too. and their side fx are pleasing to the ear too..

And as all emulations sofar fail to get that right, one could get the idea that there is more to the equation than there is known yet..or at least put in relation to audible fx.

When you send a digital track thru a transformer treatment and back into the digital domain it sounds dispite the two extra conversions still way more like transformer treated as any simulation plug i ve heard yet could do.

The problem with the inductor simulation in "plug-ins" is that, to do a good job, would require enormous processing power to do in anything near "real time". There's just too much energy to keep track of...

However, the simulation tools I use on circuits could absolutely process an audio track through a saturating inductor circuit. It would take hours for a pop song....




-tINY

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22nd November 2012
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[FONT="comic sans ms"][COLOR="indigo"]
The problem with the inductor simulation in "plug-ins" is that, to do a good job, would require enormous processing power to do in anything near "real time". There's just too much energy to keep track of...
Universal Audio models inductor hysteresis and saturation in their version of the Massive Passive in real time.


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