Audio Purists

March 20, 2009

There is a group of sound guys I call “audio purists.” These are people who eschew anything which colors the sound, such as EQ. To them, “purity” of sound is the ultimate goal, above all else.

All EQ colors the sound, not only by varying the frequency response, but also, as a side effect, affecting the phase angle at certain frequencies. This is most apparent when boosting frequencies, and, in extreme amounts causes “ringing,” or resonance at the boost frequency. While this is clearly heard at extreme levels of boost, it is present to some degree at more moderate amounts of boost. This is what purists object to.

Because of this, a “purist” will, when using the 31 band EQ to tune the system, only use it to cut frequencies. In fact, there are a few graphic EQs on the market that are “cut-only.” They do not boost at all. In theory, this should be a good idea. But, what of a situation, where the system sounds pretty good, but has one frequency area that is slightly lower in response to the rest of the spectrum? Most people would simply use the 1/3 octave to boost those few frequencies the 1 or 2 dB needed to smooth things out. The “purist,” however, would prefer to cut all other frequencies, to avoid boosting any band. However, one thing often overlooked is that cutting adjacent bands does NOT result in a flat response. For example, if you cut every band on a graphic EQ by 3dB, the resulting curve would not be a flat response which was simply 3dB lower than the input. Each band has the most affect at its center frequency, and gradual shoulders which boost or cut less and less the further from the center frequency you get. Also, phase shift problems are most apparent in these “shoulder” areas. These shoulder areas are additive, which means that the cut (or boost) of two adjacent bands combine where the shoulders of the filters for those two bands overlap. Therefore, the result from pulling every band down 3dB would be a response which was down 3dB at each center frequency, with ‘ripples’ between bands of lesser or more attenuation. In addition, there would be phase shifts across the entire spectrum. The end result is that, to avoid boosting in one small area of the frequency range, you would be introducing an odd frequency response in the entire spectrum which would be filled with phase anomalies. This in the name of “audio purity?”

A related thought is that they will refrain from using any (ANY!) channel EQ. In fact, they will switch it out of the circuit. This idea actually has some merit, of not carried to the extreme. Their thinking is that EQ is bad, for the reasons I stated above, and since they aren’t going to use the channel EQ, they might as well take it out of the signal path. Since every circuit adds some small amount of noise, you can avoid adding it by not having that circuit in the path at all. Consider that each EQ adds some noise, if you remove the EQs from all 32, 48, 64, or however many channels you are using, this can add up to quite a bit of noise you are avoiding. The thought goes that you should get your sound solely from mic choice and placement. In a situation where you want the most natural sounds possible, and if you are working with acoustic instruments where a “natural sound” is desired, this may be possible. I agree that you should do everything you can to get the sounds you need with mic choice and placement, but in a live situation, it’s not always possible, and you are most likely not working with cellos, violins, violas, etc. So, what is a “natural” sound for a synthesizer, electric guitar, or bass? Odds are, you are going to want to do some EQ to each one, or you will end up with a lifeless and unexciting mix. Can you imagine the average kick drum in a rock mix if you couldn’t have any EQ on it? Cheap EQ sections can sound pretty bad, but if you have good channel EQ, there’s no reason not to use it. Every board sounds different, and the EQ is a big part of this. It is one of the major things you should listen carefully to when shopping for a new mixer.

Another technique that is rather common, or at least was, among the purists,  is to put all of the channel faders at the +/-0 line, and do all of the mixing with the mic trim pots. I’m not real sure where this technique came from, other than the “purists” see a point on the fader where it is neither attenuating or boosting, and they figure that is the “natural” (or “neutral”) spot. However, if you read one of my earlier posts, you may remember that, on instruments that need to be quieter in the mix, this can result in added noise, since you are turning it down at the trim pot, and then running the fader at 0. Whatever noise is added by the channel’s electronics would be better reduced by getting a good strong signal through the channel, and then running the fader at -15dB, or where ever you need it. In my opinion, it is far better to get as hot of a signal as you can coming in to the channel. During sound check, have the player go through his loudest part, and use the PFL meter to set the input level to 0VU and do your mixing with the channel fader. That way, you have plenty of signal to work with, and if you are also sending monitor mixes from the FOH console, makes it MUCH easier to deal with.

A lot of the ideas that the “audio purists” have are based on situations in the mythical ‘ideal situation,’ but don’t often translate well to the real world of mixing a rock band. As always, use your ears and judge for yourself, but keep these things in mind when some “helpful” purist starts making suggestions. Try everything, and keep what works for you – just always consider every aspect and consequence of every technique you try. Otherwise, you may not know what is causing other, seemingly unrelated problems.


Sometimes I Just Don’t Get it

February 22, 2009

There are a lot of things I write in my blog that I expect to create controversy; to make people think. I know that there are some that won’t agree with some (or any) of what I say, and that’s fine. Most of the comments I get are positive, some say they don’t understand (which means either I didn’t do a very good job of writing my opinions, or maybe they just don’t want to understand). I’ve only gotten one nasty comment – and it wasn’t even about any of my political posts!

I got a comment which said “this post is bullshit” in response to something I had written, so I went to the post in question, and guess what it was:

How Loud Do You Want To Be?” was the target of this person’s anger. This post is about the most NON-controversial thing I’ve ever written, and yet someone felt strongly enough about it to take the time to express their displeasure.

For those of you who aren’t into pro-audio, or music, that post basically boils down to “make the music as loud as is appropriate for the type of music and the crowd” and gives some tips on how to deal with musicians (and drummers, too).

Oh well. I guess I can write that “politicians are a bunch of thieving liars and tyrants, who are only concerned with their own power, wealth, and importance” and that’s alright. But if I say “Don’t mix too loudly or quietly,” then it’s ‘bullshit.’

As I said: sometimes I just don’t get it.


Tools of the Trade

January 18, 2009

One area that is often overlooked is that of tools to always have in your tool kit at every show. You’ll need tools to test, and tools to fix.

You’ll need a fairly good multimeter. With this you can test the AC line voltage. If you seem to have lousy headroom, and some of your switching doesn’t work well, check the line voltage. It should be somewhere in the 115V-125V range. You usually won’t have a problem with the voltage being too high, but you will sometimes run into voltage that is on the low side, and it can affect how much headroom your power amps have. In drastic cases, it can cause distortion at nearly any volume.

You can also use it to test cables, guitar pickups, and components of gear when you have to pop the hood on something.

Also, go to Radio Shack and buy a $6 “Line Tester.” This is a real life saver (possibly literally!). It checks the outlet to make sure that none of the conductors are switched. I use these on every outlet I will have to use before I plug a single thing into them. The most common flaw they will find, which is difficult to check without one of these, is that of the neutral and ground being switched. If you try to use an outlet wired like this, you will end up with hum at the very least.

A 9V battery is a requirement. A quick, easy, and reliable test for speakers. Don’t leave it connected for long, and never use it on a compression driver! Use a jumper to connect the negative connection to the (-) side of your speaker, and briefly touch the positive side to the (+) terminal on the speaker. The cone should jump forcibly OUT. You should hear a ‘thump,’ but no scraping or rattling. Connect it to the speaker cable leading to your speaker, and all of the speaker cones should move the same direction. This is VERY important. If any of them move in while the others move out, then the one that moves in is wired out of phase. Fix it right now. It’s killing your low end.

You can also use it as a ‘down and dirty’ way to quickly check cables when you can’t get both ends close together (such as a snake you’ve already laid out). Connect the battery (-) to Pin 1 and (+) to Pin 3. Grab your multimeter and go to the other end of the cable, put your meter on a DC Voltage setting that will cover 9VDC, and you should find +9V on Pin 3 (referenced to Pin 1) and nothing on Pin 2. Connect the (+) terminal of the battery to Pin 2, go back and re-test with the meter. You should now have +9V on Pin 2 (referenced to Pin 1). You’ve just completed a very basic test of that snake channel. You haven’t tested everything that can go wrong with it, but it should pass sound. If you don’t get a reading on either Pin 2 or Pin 3 with either test, then there is a problem with the Pin 1 connection (the shield). If one gives a reading, but not the other, then the one with no reading has a problem. The problem is usually at the mixer end (the pigtail). Pull that XLR shell and examine the connection.

A soldering “iron.” Actually, I would carry two. One fairly hefty one to repair connections on larger cables, patch bays, etc. And one smaller one for mic cables and for fixing the insides of your equipment. Also, be aware that if you are doing an outdoor show when it’s chilly and windy, a smaller soldering iron may NEVER get your connection hot enough to make a good solder joint.

Solder wick, and good solder. (Don’t forget to tin your wires before soldering!!)

Pliers, needlenose pliers, vise-grips, wire cutters, a good razorblade, electrical tape, a MiniMag, or other flashlight small enough to hold in your mouth so you have both hands free.

A good selection of screwdrivers. As basic as this is, you wouldn’t believe how many people don’t carry even a basic set. You’ll need a tiny flathead for those screws in XLR shells. You’ll need a few good Phillips (or whatever matches the fasteners you used to mount all of your rack gear). Wrenches and whatever you need to take the back off of a cabinet and replace a speaker.

Spare everything.


Random Stuff About Speakers

January 1, 2009

Speakers are the last link in your audio signal chain, and can have the most dramatic effect on the overall sound of your system. They not only determine how efficient your system is overall, but also the frequency response, transient response, and how loud you can be.

A speaker consists of a very few parts.

1) The frame – simply the metal frame in which everything else is mounted. They can be stamped metal, which is the cheaper method, lighter, and potentially not as rigid; or they can be cast metal, which is usually used in the more expensive speakers.

2) The magnet – a magnet attached to the rear of the frame. The heaviest part of the speaker. The heavier the magnet is, the better the efficiency and low end response.

3) Voice coil – A coil of wire wrapped around a “bobbin” to form a cylindrical coil, which rides in a gap in the magnet. The two ends of the coil are connected to terminals on the frame of the speaker. The output of the amplifier is connected directly to the voice coil. When power is applied to the voice coil, the magnetic field in the gap causes the voice coil to move. (the stronger the magnetic field, the more movement for a given power input, all other things being equal)

4) The cone – The conical shaped thing that faces the front of the speaker. Traditionally, these are made from a type of cardboard. Sometimes you will see metal or plastic used as cone material, but not usually in pro-audio applications. The cone is attached to the voice coil, whose oscillations are transferred to the cone, which in turn, moves air.

5) The surround – This is the wavy part around the outside edge of the cone, just inside where the cone is glued to the frame. Is is most often cardboard, but in some speakers can be cloth, or foam rubber(!). The surround doesn’t really serve any audio purpose – it exists merely to connect the moving cone to the non-moving frame.

6) Dust cover – the little dome in the center of the cone. This keeps dust from getting into the voice coil gap. These can be vented, having a small (1/2″) section of screen in the center, to aid in cooling and to allow more unrestricted movement.

Barring physical damage, such as dropping the speaker, the most common parts of the speaker to fail are the voice coil, cone, and surround.

How they fail, and why

The surround can fail due to a couple of causes, neither of which is much of a mystery. The surround can just simply wear out. The cardboard of the surround is much thinner than the cone material, and, by necessity much more flexible. Over time, the constant flexing of the surround weakens it, and it can eventually just start developing rips radially. Or, in some closed-box applications, the air pressure inside the box can actually blow a hole in the surround. A hole in the surround doesn’t necessarily make a noise itself, but it can change the frequency response of a cabinet, since it is effectively a port. Also, once the rip or hole in the surround gets bad enough, the cone can become misaligned (off-centered) which will cause the voice coil to rub, which you will definitely hear.

A cone is more trouble-free, as long as you don’t stick a screwdriver through it while installing the speaker. Unlike the surround, a cone’s job is to remain rigid, so the entire surface area moves as one unit. Like the surround, a cone can, after time, wear out from the constant movement and humidity. The cone becomes flimsy and “soft.” Once this happens, the cone no longer moves as a single unit, which will affect the frequency response and efficiency.

Check your speakers every couple of months to make sure the cone and the surround are intact. If you are REALLY paranoid, rotate your speakers 90 degrees. Yes, if they hang the same direction over a long period, and are also exposed to travel bumps, the weight of the cone over a long period can possibly cause cone misalignment.

The dust covers aren’t usually a source of much trouble, although they can occasionally come loose because the glue holding them on dries out, and the combination of the dust cover’s inertia and the air pressure behind it can cause one edge to come loose. Do NOT try fixing them with tape (even duct tape isn’t going to work, believe it or not). Even if you can get it to stick, it’s not going to hold the dust cover firmly enough to keep it from rattling, so not only will the dust cover still rattle, but now the tape is going to rattle as well. If you have a rattle and find out that it is a dust cover, you can get through a show by CAREFULLY removing the dust cover entirely. Take it to your recone expert the next day.

Voice coils are the most common part to fail on a speaker, and there are two different results when they do: The speaker will rattle; or the speaker will be silent. (There is also the not entirely un-humorous “flaming speaker” which was usually caused by a Crown DC-300 dumping its DC supply into your speakers, but that’s another story)

All of the current flowing through the wire of the voice coil causes heat. This heat is mostly transferred to the metal of the magnet, which has a heat sink to dissipate the heat into the surrounding air. The movement of the speaker itself also helps keep it cool. However, if you exceed the power handling of the speaker continuously for an extended period, the voice coil will overheat. This overheating causes the adhesive used to bind the wire to the “bobbin” to come loose, the wire will partially unwind, and will either rub the voice coil gap, which you hear as a severe rattle, or will bind completely, which you hear as silence. There’s nothing you can do at the show venue. Replace it with a spare and take it to your recone expert when you can.

The voice coil can also jump out of its gap. If it remains aligned while it’s out there, it may slip back into the gap with no ill affects, other than you will hear distortion caused by the non-linear response of the speaker. If, however, it doesn’t quite remain aligned perfectly, it won’t hit the gap, and will instead slam down beside the gap, and will be essentially “locked up.” It will be silent. The cone won’t move when you push it. You MAY be able to pull the cone outward carefully (putting equal pressure on all sides of the cone) and get it to slip back into the gap, but don’t bet on it. Be aware, that since the speaker will not move, it will draw more current than normal, and since it doesn’t have the cooling action of the movement, will overheat more easily. In other words, if you notice a speaker not working, troubleshoot it as soon as possible.

As with all repair and maintenance work, if you have to open a cabinet, while you’re in there, check all electrical connections, and check the cabinet integrity. If you see any loose braces or stripped screws, FIX THEM. If they remain unfixed, they WILL be a future source of a rattle.


Troubleshooting Audio Problems in Your P.A.

December 18, 2008

As with anything, eventually, you’re going to have something break, stop working, or just plain not “sound right” in your sound system. You will have to diagnose the problem, and find the easiest, fastest solution to the problem and get it fixed with the least amount of drama or attention being drawn to the situation.

The first step is to diagnose what the issue is in a broad sense. To do this, you’re going to need to hear it and be able to try certain things, so this part of the procedure will be behind the console. What is, and what isn’t working? Once you figure out what isn’t working, you need to figure out in what way isn’t it working? Is there just no sound? Is there sound, but it is distorted? Is there clean sound, but the level isn’t right? Etc. (It takes longer to read this paragraph than it should to perform this step.) This has to be done in a logical sequence to zero in on what piece of gear has broken in the least amount of time, and in a way that doesn’t waste effort. Start with the most likely cause, and if that isn’t it, move on to the next most likely cause. Eventually, you will find it.

Once you’ve narrowed down the result of the problem, it’s time to begin to narrow down the offending piece of equipment. You do this by swapping parts for known good parts, or connecting them to a known good piece.

Here’s an example: Let’s start with the easiest possible example – a vocal mic doesn’t work, and you are sending a monitor feed from the FOH console, so there is no splitter or monitor console. You solo that channel, and it’s dead – no sound at all. All of the other mics work and sound fine. It’s a dynamic mic, so it doesn’t need 48V phantom power, so that’s not an issue. There is no distortion in the FOH system or monitors. That narrows it down: you know that the basic system works – the speakers work, the amps are alive, the crossovers, EQ, and snake returns work. The thing that is not working is limited to one channel. The possible causes are (in order of signal flow): mic; mic cable; snake channel; console channel.

So, let’s re-arrange that to the order of likelihood of failure: mics rarely fail, and console channels don’t fail very often, and usually not total failure. That leaves the mic cable and that channel of the snake. From experience, I know that mic cables fail much more often than snake channels, so the first thing I would do is replace the mic cable with one that you KNOW is good. Then test the mic. If it works, great! If not, go to the next step. Still using the known good replacement mic cable, plug that mic cable into another channel on the snake, and test.
If it STILL doesn’t work, plug that snake channel into a different mic input on the console, and test. If it STILL doesn’t work, the only thing left in that chain is the mic.

It is this process of elimination that will help you find and fix a problem in the least amount of time, and with the least amount of effort. A problem like this isn’t a time to drag out cable testers or the like. You’d spend about as much time testing the cable in awkward locations (like beside the drummer, in the dark, with everyone waiting on you) with your tester, as it would take to swap it out.

As you might have gathered from this example, it’s easiest to fix things that don’t work at all – totally dead.

You WILL run into situations where things work fine . . . sometimes. Things will be going smoothly, and suddenly something breaks. Just as you start to troubleshoot, it starts working again! These problems can be the most difficult and frustrating problems to deal with, because you can’t find out what is broken while it is working. Sometimes it will only happen once in a great while. You can still go through the troubleshooting exercise to narrow it down to one particular group of parts.

Let’s say that all of the subwoofers cut out for a few seconds, and then just as suddenly, start working again. In your mind, you can do some troubleshooting. You know, for example, that it wasn’t a problem with any of the mics, snake, or console. It had to have been “behind” the crossover – and that chain would include the output of the crossover itself, the cable from the crossover to the subwoofer amps. the amps themselves, the cabling from the amps’ outputs to the connector on the panel of the rack, the speaker cables that go to the subwoofers, and the subwoofers themselves.

Since ALL of the subwoofers stopped, it also can’t be anything that is specific to one cabinet or pair of cabinets. It must be something that is common to all of the subwoofer cabinets, output of the crossover, cables from the output of the crossover to the input of the amps, or (if you drive all of your subwoofers with one amp) the amp.

Think about the rate of failure in a subwoofer system. Speakers are probably the first, amps next, then cabling, and lastly crossover. Since all of the subwoofers just stopped working, and didn’t make any nasty rattling noises first, and then just started working, I’d rule out speakers. The odds of you blowing every single subwoofer at the exact same time are extremely low, plus speakers usually give some sounds of distress first. Plus, blown speakers do NOT start working again. Once they die, they don’t resurrect themselves.

Some amps have thermal protection which can shut them off until the cool enough, and then they come back on. Check the amp’s fan to make sure it’s working, and the cooling fins are relatively clean and not obstructed. It could be the connection between the output of the crossover and the amp. You can swap that out with a known good cable to eliminate this cable as the problem. You can eliminate the crossover itself by connecting the input of the subwoofer amps to the mid-bass output of the crossover (this won’t hurt anything). If the subwoofers put out sound connected this way, but not when plugged into the low-frequency output of the crossover, it could be a crossover problem. Swap it out with your spare (you DO have a spare of all of the “show-stopper” parts of your system, don’t you??).

The key here, is that you can’t actually DO any of this until it fails again, but you will at least have a plan of action in mind, and may be able to have some of the swap-out parts handy so you can cut a few extra seconds off of your down time.

Using your knowledge of your sound system components, some very basic understanding of electronics, and a lot of logic, you can quickly and easily get your system back up and running in very little time. Once you have identified a bad part – MARK IT AS BAD!! I can’t stress this enough. Nothing will take the wind out of your sails faster than the next day when you intend to repair a bad mic cable you found, you remember that you didn’t mark it, and it looks just like the other 40 mic cables in your cable trunk.

If you find a bad mic cable, slide the XLR shell back and see if there is a broken connection where the wire is soldered to the connector. If so, fix it, and also re-do the other end. When one end fails, the other end may be close behind. If both of the ends look good, cut the cable in half, and use your ohm-meter to find which half is bad. Take the XLR connector off the bad half and use it on the good half. Throw the bad half away, unless you want to spend the time to keep cutting it in half to find a good part that’s still long enough to use for anything.


Transformers . . . .

December 13, 2008

No, not “Robots in Disguise,” but rather the electronic kind.

Often misunderstood and mysterious, their basic function is to do as their name says: transform. Their primary purpose is to change something – a voltage or impedance. They can be very useful in a variety of ways, and are present in nearly every piece of electronic gear.

The most basic of transformers consists of two coils of wire wrapped around a core, usually of metal. The two wires are not connected to each other electrically. They interact due to the magnetic field they create and their close proxomity to each other. One other, but equally as useful result of their construction is that they will not pass any DC at all. Any DC applied to the “primary coil” is not induced into the “secondary coil.”

They change voltage in a ratio that is determined by the number of turns each of these coils has. For instance, if the primary has 10 turns, and the secondary has 100 turns, then 1VAC applied to the primary results in 10VAC signal on the secondary.  This would be a 1:10 winding ratio transformer, and could be used as a “step up transformer.”

At first glance, it would seem that this would be an amplifier, but there is a very important law that comes into play. That is the law which states that “energy is never created or lost, but only converted into something else.” Therefore, while the voltage may be “stepped up,” the current available at the secondary is reduced by the same ratio. If the transformer were 100% efficient, these figures would be exact, but nothing is 100% efficient. A little energy is “lost” (mostly converted to heat) through the resistance of the wires used to construct the transformer, and various magnetic losses – including stray magnetic fields that ‘escape’ from the transformer and can affect nearby circuitry).  A fairly standard efficiency rating for a transformer would be in the 85%-90% range.  So, any time you use a transformer, there is actually some loss involved, but the benefits usually outweight the losses.  A transformer is what is called a “passive device.”  It draws no external power, and can generate no power gain, and in fact, always results in a slight power loss.

What, you may ask, are transformers used for in the audio realm?

Probably the most common use of a transformer (besides the internals of your equipment) is the lowly direct box (usually called a “DI“).  It interfaces the high impedance (10K-12K ohms or so) of a guitar or bass to the low impedance (600 ohms to 1K ohm) of a mic preamp.  In this function, it is called an “impedance matching transformer.”  Without this, if you plugged a guitar or bass directly into a mic preamp, the relatively low impedance of the mic preamp would “load” the guitar’s pickups too much and would adversely affect frequency response.

Another use of transformers is in the splitter systems used to split the signal from a microphone and send it to two consoles (FOH and monitor).  In this case, the transformer has one primary winding and TWO secondaries, and each winding is isolated from every other winding.  In this design, the transformer is a 1:1 ratio – there is no voltage step up or down, and there is no impedance matching function.  This not only splits the signal, it also isolates the two consoles from each other so there is no interaction as can otherwise happen if the consoles have a particular preamp design.  If you simply used a “Y Cable” to split between the two consoles, the mic preamps of the two consoles would be in parallel, which would reduce the “load impedance” seen by the mic to one half, which may be low enough that it would begin to affect the response of the mic.

One thing to be aware of when using transformers is that they not only create magnetic fields, but they also will interact with magnetic fields that may be nearby.  For instance, if you set a DI on top of a bass amp, the magnetic field created by the bass amp’s power transformer may be ‘picked up’ by the DI’s transformer and cause a 60Hz hum in the low impedance (mic) output of the DI.  Simply move the DI.  I would suggest putting it on the floor.

The coils of which a transformer is made are not purely resistive.  They present what is called an “inductive load.

The design of a good quality transformer for a specific purpose is a skilled art that requires extensive knowledge of electronics, magnetics, metallurgy.  And, just like everything else, there are good quality transformers, and there are crappy transformers.  It can be the difference in design or materials.  Also, using a transformer for something other than it was designed for will result in poor results.

 


Tubes??

December 6, 2008

I see a lot of audio products for sale recently that have a tube inside, and claim to provide “that vintage sound.” The odd thing is that the “vintage” period they all talk about is a period where transisters were already widely used in pro-audio equipment.

Tubes have their place . . . . in guitar amps. Tubes add something to the sound, due partially to the way they distort, but primarily because they add second-order harmonics to the original signal, and this tends to sound “fuller” and “warmer.” These are good qualities in a guitar amp, but not necessarily in pro-audio gear. There is one major difference between guitar amps and pro-audio gear. A guitar amp is a part of the sound generation (production) process. It is the various distortions, non-linearities, and non-flat responses that make a guitar and guitar amp sound ‘good.’

Conversely, pro-audio gear should add nothing to the sound, the frequency responses should be flat, and the dynamics should follow the original exactly, with no compression (except what you purposely add) and no ‘ringing.’  It is sound RE-production.  It should neither add, nor take away, anything from the original – unless you purposely do that.

A guitar plugged directly into a hi-fidelity system sounds horrible, and likewise, playback of a mix through a guitar amp is even worse.

Beware of claims that a tube mic preamp will provide you with cleaner sound somehow. If used on someone’s vocal mic, it may indeed make it sound somehow “warmer.” But, don’t be fooled. What you are hearing is simply distortion (“distortion” technically is anything that changes the waveform).  You are using the tube mic preamp as an effect. It (as an effect) is not a normal part of the signal chain, and you wouldn’t want to use it on everything (just as you wouldn’t stick a chorus on everything in a mix).

Tubes would have some serious problems if used in pro-audio gear: size, weight, heat, reliability, durability, as well as sound quality.

There is a reason that all of the manufacturers went to solid state as soon as it was possible, and this is what made portable sound systems as we know them today possible. Don’t get sucked into the marketing hype. Certain companies hope that you buy into their marketing hype so that you’ll shell out a couple of thousand dollars for a tube mic preamp. There are an awful lot of six and seven figure consoles out there, (both recording and live consoles) such as Neve, SSL, Harrison, NeoTek, MCI, Soundcraft, Allen & Heath, Yamaha, that have been the top brands for the past 30-35 years, and not one of them has a tube preamp. Most of the major recordings you heard between the late 70’s and about 5 years ago were made using one of the first 5 in that list. (they were also being tracked on Studer, 3M, or MCI 24 track machines using (probably) Ampex 456) . THAT is the “vintage sound,” and no $2000 tube mic preamp is going to recreate that.

If you are used to using cheaper consoles, the internal mic preamps are probably not all that good quality-wise, and a $200 tube mic preamp is very likely a better preamp – NOT because it is a tube preamp, but simply because it is a $200 mic preamp.

If you really want to spend a couple of thousand to improve the sound of the vocals you record, I would suggest a Neumann U-87 might be money better spent.