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The sound of tube mics


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Why do people love tube mics? What is that special "tube sound" ?

 

I'm taking a poll. I'd love to collect opinions from people with engineering experience. WHat do you hear when you plug in a tube mic that you typically don't hear from a solid-state mic?

 

Options include, but are not limited to:

- harmonic content or "richness"?

- softened transients?

- rolled-off top end?

 

Penalties apply for anybody who says tube mics sound "warm," because until someone designs a device that measures the sonic temperature of a signal, that word has no meaning. :-)

 

By the way, I'm not implying that solid-state mics can't have softened transients or a smooth top end or rich even-order harmonics, because clearly they can. But there are generalizations to be made, and I think most people do have a baseline impression/expectation of what tube mics ought to sound like. That's what I'm interested in hearing from you.

 

RecordingHacks.com | MicParts.com | RoswellProAudio.com

 

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People love tube mics because certain tube mics have become favorites of producers, engineers, and artists who get interviewed in the popular magazines.

 

Tube or no tube, a mic is a mic. The construction is the important part. "Tube distortion" can be introduced anywhere in the signal chain if you want it. I don't see any reason to design a new tube mic unless you're trying, primarily for marketing purposes, to make a "just like the famous one" mic. Mic manufacturers may disagree.

 

I accept that there's a reason why, for a given capsule and body, it's likely to sound different when a tube is swapped out with a FET, all other things being equal like the source, distance, and environment. Transistors have different distortion characteristics than tubes, but which one is better in any particular circumstance is a matter of taste and can't be generalized.

 

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People love tube mics because certain tube mics have become favorites of producers, engineers, and artists who get interviewed in the popular magazines.

 

I'm sure that's true for many people, but my question wasn't about marketing. It was about the actual sound of tube mics. Presumably there are some people here who, in their minds, associate certain sonic characteristics with tube mics -- whether that's right or wrong or accurate or not from a circuit design perspective.

RecordingHacks.com | MicParts.com | RoswellProAudio.com

 

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We did a microphone comparison earlier this year and I just re-listened to it to refresh my memory. I wanted to compare two different microphones that differed only in the fact that one had a tube front-end and the other a FET front-end. I chose a RØDE NT-1000 and a RØDE NTK, These two mikes have the same HF-2 capsule, no transformer and the same transistor output circuit. They are physically very similar. The only real difference is that one is tube and the other is FET.

 

I compared the microphones on acoustic guitar and female vocal. The difference was subtle, but the NTK had a bit less high-end detail than the NT-1000. I preferred the sound of the NT-1000. The subtle sound of the fingers moving along the strings was much less in the NTK, in the acoustic guitar recording. That was really the only noticeable difference on guitar.

 

The vocalist, Danielle, has an amazingly clear and beautiful voice with no excessive sibilance. The NTK captured less of the high-frequency detail and airiness in her voice.

 

That said, the differences were subtle, and I can see that the NTK might be preferable on certain voices. Also, recording an acapella voice or a solo guitar is different than recording voices or instruments that have to fit into a mix.

 

So, in answer to the question, what I heard in the tube mike was softened transients and slightly rolled off high-end. I didn't notice any added harmonic richness.

Mark Karney

 

StudioMicZone.com

Norwest.net

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I'm not sure which of those A-T mics is which, so I'm not clear as to what you prefer - more detail or less detail. Usually masking detail like finger noise is good, as long as it doesn't take away something you want to hear. But I get that for certain types of guitar music, particularly in a solo piece with lots of brightness in the strings, finger noise can be a significant part of the instrument's sound.
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Guess I never answered the question about preference. All three of us, myself, Danielle the vocalist, and her husband Bill, the guitarist, preferred the RØDE NT-1000 which was the FET mike. My opinion might have been different if these tracks had been in a mix or if it had been a different style of music or different musicians.

 

I think this is the downside of microphone "shootouts". They are conducted under very controlled and specific conditions and may tell you something about a microphone's characteristics, but won't be much help telling you how a specific mike will sound in a different room with different musicians and in a mix of a totally different song. Choosing the right microphone requires knowledge, experience, and sometimes auditioning mikes within the context of the specific song and mix.

Mark Karney

 

StudioMicZone.com

Norwest.net

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I think this is the downside of microphone "shootouts". They ... won't be much help telling you how a specific mike will sound in a different room with different musicians and in a mix of a totally different song.

 

... which is why I'm always astounded that some people want to hear audio samples before they buy a mic... as if anything I record would be predictive of someone else's results with a different signal chain, different artists, different room acoustics, etc. But I guess that is a question for another thread.

 

One thing worth noting about Mark's experience is that some of the tonal difference could be attributed to capsule variation. I do not have insider information on Rode's tolerances or QC processes, but I would not be surprised if any two HF2 capsules different by a couple dB at any given point in the frequency response. That is in no way a criticism of Rode. Just as an example, the Neumann U87 costs $3200, yet IIRC allows for a 4dB variance on a frequency sweep -- that is, plus or minus 2dB from the target curve. That's just the nature of capsule manufacturing.

 

Anyway, Mark, thanks for sharing your insights, and for listening closely to the mics you have available!

RecordingHacks.com | MicParts.com | RoswellProAudio.com

 

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  • 3 weeks later...

Currently I have no tube mics.

I haven't seen "tube rolling" mentioned in this thread yet.

I had a Rode NTK a while back. I didn't make any A/B comparisons and don't hold much stock in them anyway.

What works, works.

 

I will say that opened up the mic and took a look at the tube. I googled for equivalent tubes and poked around in a stash from my Dad's estate. He loved garage sales and would buy boxes of assorted old tubes so he could try and fix the malfunctioning old televisions he accumulated.

 

I found a pair of what appeared to be NOS Siemens E88CC tubes made in Germany, a match for the tube in the NTK.

To my ear, the mic had slightly lower noise and I liked the tone on my voice better. It just seemed more "real" (descriptions of sound are ridiculous, no?).

But that could be an advantage of a tube mic, the fact that you can change the sound of the mic by using a different tube.

Certainly there are many variants of the 12ax7 tube and other designations that can be plugged in without harming the circuit.

So a tube mic that used a 12ax7 could be "re-voiced" with a 5751, a 12at7, a vintage Sylvania (these tend to be higher gain), etc.

Would love to hear an EF86 in a mic, they have nearly double the gain of a 12ax7 (not interchangeable!!!!).

 

Not much but all I know at this point.

It took a chunk of my life to get here and I am still not sure where "here" is.
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