Switchable circuit mic

[pasarski]

That's true.



If you're in a situation where you need a pad, the noise floor is very unlikely to be any sort of issue.

But nothing in your reply is an actual answer to any of my questions, i think..?

The goal would be minimizing the negative effects introduced by the two common methods. And as I said I agree that it would not make sense in most (if not all) of the real life situations.

Edit: Maybe the goal would be better described as one circuit optimized for not so loud sources and the other one for sources with large dynamic range.

 

[garp]

An interesting design would be to mix a LDC tube mic with ribbon motor correctly placed and some "mix" pot to blend the two sources, i've always tought that could be interesting.

 

[Emmathom]

Very Interesting idea.

But should’t contemporary companies concentrate R&D in making just ONE microphone in a metal tube, that actually sounds real GOOD! As in: just right for most vocals Male or Female (Music or VO) and or for a variety of instruments?
And that at decent (not extortionary) prices. Maybe too much asking?!?


M

I would like to follow up on what @Migs 31 said and ask a question that seems fundamental to me: do we tweak out of necessity or for pure pleasure? (both I guess but seems not only for pure pleasure)
because something escapes me...
Manufacturers surely work hand in hand with sound engineers, musicians, have their own studio, read forum posts like groupdiy (which is renowned for the quality of its articles and the technical level of many of its members) so why don't they take inspiration from our comments & tweaks to improve their products???

Lewit, Universal Audio, Warm Audio, Universal Fet etc: has their internet been down for years?

I'll take the example of the AKG P220 and P420 where you just need to modify the value of ONLY ONE capacitor to free the microphone and get it closer to the sound of a U87 (@Wordsushi won't contradict me to name only him)

If you have the beginnings of an answer...

 

[Khron]

If you have the beginnings of an answer...

The marketing / management people pay the salaries of the engineers...

 

[Emmathom]

The marketing / management people pay the salaries of the engineers...

Ok but they would benefit from selling improved products rather than ones imperfect (or perfectible)

 

[Khron]

Ok but they would benefit from selling improved products rather than ones imperfect (or perfectible)

Would they, though? How successful was Neumann's TLM line?

 

[untamedfrontier]

... But why? Or rather, why "two circuits" as opposed to one with some tonal options? Or, at the very least, what would be the goal, at the end of the day?

At least from my perspective when I was first thinking about this, my main thought about having 2 circuits rather than one with different tonal options is to have something that could really showcase a great capsule's versatility, and have a mic that could potentially sound great on any source. Since capsules are (usually) the most expensive part of a solid state build, I'd really like to only buy 1 nice capsule to figure out what circuits I like since I'm still fresh on this mic building addiction journey.
I'm strongly considering picking up an Arienne K47 and it would be really fun to have the option to switch between something that:

• Is basically just the sound of the capsule, with no transformer or other coloration - as far as I've seen an Alice type circuit may be appropriate
• Has the added color of a transformer, and perhaps other circuit choices - perhaps something like a FET847 or just FET47 might be a good choice?

 

[Khron]

the added color of a transformer,

Has anyone looked into what sort of distortion products come out of a transformer, at the signal levels one might expect out of a mic? I've just always wondered how much of the transformer "sound" is actually the sound of the circuitry driving it...

I say that because the frequency response is trivial to measure, if not even also reproduce.

 

[kingkorg]

Transformers in mics usually saturate in the low end, at pretty high SPL. Vocals don't have that much power down there, so it can't be harmonics. Good transformers won't saturate at all. Tube (fet) plate (drain) out > transformer > preamp and you might get some funkynes due to matching/mismatching.

For whatever reason my 1176 into La2a clones produce HF roll-off, but not when used on their own. Hadn't i measured this, i'd think it was magic.

 

[pasarski]

Transformers in mics usually saturate in the low end, at pretty high SPL. Vocals don't have that much power down there, so it can't be harmonics. Good transformers won't saturate at all. Tube (fet) plate (drain) out > transformer > preamp and you might get some funkynes due to matching/mismatching.

For whatever reason my 1176 into La2a clones produce HF roll-off, but not when used on their own. Hadn't i measured this, i'd think it was magic.

I've come to a conclusion (not a definite one but how I currently see it) that "the transfromer sound" - especially when talking about microphones - is much about the resonant high pass filter formed by the output topology (plate/drain and preamp impedance, output cap's capacitance and the primary inductance). There might be some "magnetic mojo magic" happening, but I'm not sure if it's the dominant factor, considering that changing a trafo to an other one with same ratio but lower primary inductance can introduce a 10db bump in the low end.

Also yes, as you said, transformers only saturate at high level low frequency signals and they do it abruptly (they clip asymmetrically) and it doesn't sound nice. At least that's what I've read. Maybe there's a a very small sweet spot of saturation between the linear and clipped signal, but there's probably easier ways to achieve that sweet saturation.

I know there are a actual transformer experts on the forum, please correct me if I'm wrong.

 

[Khron]

"the transfromer sound" - especially when talking about microphones - is much about the resonant high pass filter formed by the output topology (plate/drain and preamp impedance, output cap's capacitance and the primary inductance).

If the capacitor value is high enough, there's no resonance to worry about, so that's out.

https://sound-au.com/articles/audio-xfmrs.htm#s3

 

[Paul W]

I've come to a conclusion (not a definite one but how I currently see it) that "the transfromer sound" - especially when talking about microphones - is much about the resonant high pass filter formed by the output topology (plate/drain and preamp impedance, output cap's capacitance and the primary inductance). There might be some "magnetic mojo magic" happening, but I'm not sure if it's the dominant factor, considering that changing a trafo to an other one with same ratio but lower primary inductance can introduce a 10db bump in the low end.

Also yes, as you said, transformers only saturate at high level low frequency signals and they do it abruptly (they clip asymmetrically) and it doesn't sound nice. At least that's what I've read. Maybe there's a a very small sweet spot of saturation between the linear and clipped signal, but there's probably easier ways to achieve that sweet saturation.

I know there are a actual transformer experts on the forum, please correct me if I'm wrong.

I'm curious too. Something I read recently talked about how asymmetrical transfer functions generate even harmonics but symmetrical ones only generate odd harmonics, which some people say are less "musical," all other things being equal.

That would seem to imply that asymmetrical saturation is good, if you're going for color.

Does that have implications for biasing FETs in condenser mic head amps, or other "colorful" amps? I'd think that if you want maximum clean dynamic range you'd aim for symmetry, but if you want color you'd avoid it. (And of course you'd want a circuit that saturates gracefully rather than suddenly going into hard clipping.)

If any of that's right, should there be a bias level switch so that you can choose between symmetrical and asymmetrical saturation?

(I assume it's way more complicated than this, becaouse once you feed complex waveforms into saturation, you get all sorts of weirdness... but is there a useful kernel of truth to it?)

 

[Khron]

Does that have implications for biasing FETs in condenser mic head amps, or other "colorful" amps?

Yes and no - a single-ended circuit WILL always clip asymmetrically, even when biased for maximum dynamic range.

 

[pasarski]

The "musical" clipping is more about the softness/hardness of the clipping than the symmetry, at least if we're not talking about Swedish death metal. Also mastering engineers who digitally hard clip the masters may disagree. Even more off topic sorry, but can't help not to mention that a friend once saw a live mixing engineer of a well known act using two tube screamers on the master bus.

 

[kingkorg]

The "musical" clipping is more about the softness/hardness of the clipping than the symmetry, at least if we're not talking about Swedish death metal. Also mastering engineers who digitally hard clip the masters may disagree. Even more off topic sorry, but can't help not to mention that a friend once saw a live mixing engineer of a well known act using two tube screamers on the master bus.

I agree 100%. It's mostly about how much clipping you can get away with, without ruining the material. I clip things on every track that requires it, so i don't have to clip the master.

Hence my latest obsession with extremely high headroom mics on drums so i can microscopically control clipping later.

I don't think anyone likes how hard clipped signal sounds unless it's for special effect or style.

 

[Paul W]

The "musical" clipping is more about the softness/hardness of the clipping than the symmetry, at least if we're not talking about Swedish death metal.

I've heard the claim that asymmetry (and resulting even harmonics) is important in non-metal contexts, like tube amps for stereo playback systems and (IIRC) almost-clean microphone preamps, for "tube warmth," or digital effects for similar purposes.

Even if that's what a single-ended amp normally does, I'm wondering if you can carefully construct a transfer function so that it optimizes the ratio of even to odd harmonics in a way a normal amp would not. (If in fact that's actually a good thing to do.)

 

[Paul W]

I agree 100%. It's mostly about how much clipping you can get away with, without ruining the material. I clip things on every track that requires it, so i don't have to clip the master.

Hence my latest obsession with extremely high headroom mics on drums so i can microscopically control clipping later.

My understanding is that normally if you're getting a modest amount of saturation for the loud stuff, you get almost none at significantly lower volume levels.

That makes me wonder if it would make sense to use an envelope-following compressor-distorter-decompressor to turn the gain up in quiet passages so they'll saturate a little too, but then back down so that you restore the dynamics.

 

[kingkorg]

My understanding is that normally if you're getting a modest amount of saturation for the loud stuff, you get almost none at significantly lower volume levels.

That makes me wonder if i would make sense to use an envelope-following compressor-distorter-decompressor to turn the gain up in quiet passages so they'll saturate a little too, but then back down so that you restore the dynamics.

Great idea. Even though i've never used this technique, there is possibility of using two mics for quiet and loud parts. Usually used the other way around to avoid clipping and saturation for extremely dynamic singers. Or two cardioid capsules in one body, same orientation, two different circuits.

Also knee of the saturation curve will depend on topology. Plate out tube circuit has very soft gradual curve, opamp will go from .000001%thd to 30%thd within a fraction of a volt.

 

[jp8]

I've come to a conclusion (not a definite one but how I currently see it) that "the transfromer sound" - especially when talking about microphones - is much about the resonant high pass filter formed by the output topology (plate/drain and preamp impedance, output cap's capacitance and the primary inductance). There might be some "magnetic mojo magic" happening, but I'm not sure if it's the dominant factor, considering that changing a trafo to an other one with same ratio but lower primary inductance can introduce a 10db bump in the low end.

Also yes, as you said, transformers only saturate at high level low frequency signals and they do it abruptly (they clip asymmetrically) and it doesn't sound nice. At least that's what I've read. Maybe there's a a very small sweet spot of saturation between the linear and clipped signal, but there's probably easier ways to achieve that sweet saturation.

I know there are a actual transformer experts on the forum, please correct me if I'm wrong.

I don't want to pretend to be an audio transformer expert, but low-end FR and distortion of a transformer coupled output depends not only on the transformer used and the size of the coupling cap, but also on the load and to a large extent on the output impedance of the driving stage. I will show some REW FR and distortion plots of my KM84 experiments later when I'm back home from travel. I will also present a simple method with an additional cap and resistor to control the peaking, even when using a small DC blocking cap. I haven't seen that method being used anywhere, so it could have disadvantages that I missed somehow, so I'm curious what you think of it.

Jan

 

[jp8]

My understanding is that normally if you're getting a modest amount of saturation for the loud stuff, you get almost none at significantly lower volume levels.

That makes me wonder if it would make sense to use an envelope-following compressor-distorter-decompressor to turn the gain up in quiet passages so they'll saturate a little too, but then back down so that you restore the dynamics.

I had a similar idea, but that would shift the operating point of a distortion circuit instead of using compression/expansion. LTspice simulations did not work, so I'm back to the drawing board. The circuit should only add harmonics below an adjustable frequency, to avoid harshness in the highs.

If this would work and would yield sonically pleasing results, I would have assumed it already exists, either in hardware or as a plugin. AFAIK, harmonic content of instruments or a voice increases with amplitude, so it might sound unnatural if harmonic content was also increased at low levels. Anyone who knows more about that?

Jan