Why Tube Amps Sound Different (and better) Than SS Amps

[esldude]

Obviously, if you hear a change in sound after changing cables then the signal has changed. Just because whatever you think you are measuring hasn't changed that doesn't mean something else hasn't. Then again, perhaps the tools being used are not up to the task. For instance, did you make any DTCD measurements? I didn't think so. Who knows what other electrical properties are waiting to be discovered.

DTCD:
http://www.shunyata.com/index.php/technical-feat/technologies/78-dtcd/288-dtcd
http://www.shunyata.com/index.php/t...gies/78-dtcd/289-dtcd-measurement-comparisons

Another old cliche. If we hear it then it must be so, which presumes hearing is more accurate than good measures which isn't true.

Combined with another oldie, but goody, ridiculous measurements of some product that bear no relation in a way that can matter in how the product is used. And like many such, they even illustrate why it is a garbage measure if you look closely.

The first link is about pulsed high current through the cord. They say it is AC though we don't know if that is 60 hz or something else. When you see their impulse profile you see it must be something like a stepped square wave. 60 hz from the wall doesn't change like that. It also is a stock black cord vs their Venom 3. Quite possibly the stock cord is 14 gauge or 16 gauge maybe even 18 gauge. The Venom is 12 gauge. That alone would explain the difference they are showing. They also show the stock cord reaching a steady state at a lower amperage than theirs. A tipoff this cord is smaller gauge. And how real world is the signal? Like plenty as long as you need to suck 25,000 watts from the wall plug. Then they show voltage drop for that amount of current, which is tip off #2 the stock cord is smaller gauge. Saving you the boring math looking at the voltage drops they were using about a 32 volt source over what likely was a long power cord. Color me impressed. They show why a smaller gauge wire has more voltage drop and less current capability than a larger wire at huge currents, and low voltages and no loading other than the wire.

Now in the second link like many such ads, they even reveal the difference. They have a chart for 18, 16, and 14 gauge. Notice how the 18 gauge is just about the amount shown in the previous link. They were comparing a stock 18 gauge cord to their 12 gauge Venom. Then in their Venom vs Mamba notice the steady state current is almost the same. Both are 12 gauge. Again we don't know what frequency the pulse was. It looks to have been a step wave impulse. So the difference in time between their two cables is due to high frequency effects. One cable gets to full voltage 32 microseconds quicker. Which is barely over .1% of a 60 hz wave from the wall. Plus add any resistance and the difference in time between these cables reaching full voltage will rapidly diminish. In other words hooked to any piece of equipment the difference is truly trivial and then some. Lay a 60 hz waveform over that time and any including the stock cable would keep up perfectly well.

It was an ad intended to bamboozle one and look like a meaningful measurement. They showed their cord is superior anytime you are trying to conduct a square wave at 200 amps with no load connected to the power cord. Well worth the money as many have claimed I suppose.

 

[microstrip]

But both Stereophile and Carver later retracted the contention that the amps were indistinguishable. I don't think anyone doubts Carver's abilities as an engineer and amplifier designer (speakers, maybe), and there are quite a few examples of modern production tube amps whose sound could be mistaken for SS and vice versa.

Rob,

As far as I remember Bob Carver never wanted to comment openly on this challenge, but later he clearly regretted having carried it. The fact that it was non controlled, non documented and was never repeated with success makes it just a nice and interesting fait divers in audio history. It was surely a violent shakeup in many people convictions.

Although some modern tube amplifiers have no more the typical characteristics (that most of us perceive as faults) of older designs and SS amplifiers have evolved a lot there are some key aspects where the difference is clear. Sorry to disagree with many people, but IMHO the Dartzeel combo does not sound like a tube combo. Absence of defects does not equate to presence of the same qualities.

 

[microstrip]

Another old cliche. If we hear it then it must be so, which presumes hearing is more accurate than good measures which isn't true.

Combined with another oldie, but goody, ridiculous measurements of some product that bear no relation in a way that can matter in how the product is used. And like many such, they even illustrate why it is a garbage measure if you look closely.

The first link is about pulsed high current through the cord. They say it is AC though we don't know if that is 60 hz or something else. When you see their impulse profile you see it must be something like a stepped square wave. 60 hz from the wall doesn't change like that. It also is a stock black cord vs their Venom 3. Quite possibly the stock cord is 14 gauge or 16 gauge maybe even 18 gauge. The Venom is 12 gauge. That alone would explain the difference they are showing. They also show the stock cord reaching a steady state at a lower amperage than theirs. A tipoff this cord is smaller gauge. And how real world is the signal? Like plenty as long as you need to suck 25,000 watts from the wall plug. Then they show voltage drop for that amount of current, which is tip off #2 the stock cord is smaller gauge. Saving you the boring math looking at the voltage drops they were using about a 32 volt source over what likely was a long power cord. Color me impressed. They show why a smaller gauge wire has more voltage drop and less current capability than a larger wire at huge currents, and low voltages and no loading other than the wire.

Now in the second link like many such ads, they even reveal the difference. They have a chart for 18, 16, and 14 gauge. Notice how the 18 gauge is just about the amount shown in the previous link. They were comparing a stock 18 gauge cord to their 12 gauge Venom. Then in their Venom vs Mamba notice the steady state current is almost the same. Both are 12 gauge. Again we don't know what frequency the pulse was. It looks to have been a step wave impulse. So the difference in time between their two cables is due to high frequency effects. One cable gets to full voltage 32 microseconds quicker. Which is barely over .1% of a 60 hz wave from the wall. Plus add any resistance and the difference in time between these cables reaching full voltage will rapidly diminish. In other words hooked to any piece of equipment the difference is truly trivial and then some. Lay a 60 hz waveform over that time and any including the stock cable would keep up perfectly well.

It was an ad intended to bamboozle one and look like a meaningful measurement. They showed their cord is superior anytime you are trying to conduct a square wave at 200 amps with no load connected to the power cord. Well worth the money as many have claimed I suppose.

You are just exposing the use by marketing people of the incomplete technical aspects and measurements used by this manufacturer to develop and manufacture their cables. These measurements just show some aspects in which they are consistently different from typical cables and the scaling of them in their different ranges. It is known since long that in cables the proof of the pudding must be in the listening. Oops, I forgot you consider listening to cables a manifestation of superstition.

Cable manufacturers must create some typical characteristics that became their ex-libris. Remember that they must persuade us to buy their products, not the competition!

 

[esldude]

Have you measured the impedance, phase and efficiency of your Soundlab Aura speakers? Can you tell us what specification set you used to choose your amplifier? As far as I could see almost all the specifications available in the manufacturer site of the ST500 would receive a red warning according to the AudioPrecision white paper "How to write (and read) audio specifications". This surely does not mean that the amplifier is not excellent value for money - and I hope that you are not going to tell us you got it based on TheAbsoluteSound awards.

I agree the standard spec looks designed to impress falsely. I had read that these amps worked well with some difficult loads while sounding good. Yes plain old anecdotal reports. So I had my eye on them. One of the reps at W4S was asked and provided more detailed specs on a forum. I think it was on the AVS forum. Then I ran across a small site that had measured them (and where the same measures were done they matched pretty well with W4S claims). Most troubling is most of the specs don't specify 20-20khz results, but the extra info did. I was concerned the output filtering in these amps would match badly with the low treble impedance of the Soundlabs.

The specs are deceptive in that the amps have about half the advertised power at 20 khz. The output impedance goes up some, but actually stays as low as or lower than most other SS amps with frequency. Another oddity is the 500 wpc channel version has a small amount less steady state power at high frequencies than its smaller brother (the 250 wpc version I have). I wasn't too worried about lesser power as the treble levels are usually low as long as it didn't upset the amp to have very low impedance at the treble.

So I had hopes it would work pretty well, and specs that fit with what I needed with a couple of possible issues. I gave them a try and they worked out fine. They seem much less bothered by the load than a couple of quite hefty conventional SS amps I have used.

I have measured phase and impedance of my speakers (these basically are M3's internally and as far as the panel goes). Not the efficiency. I don't believe I measured the output in the treble with this amps at the speaker terminals. I do use a Tact for room correction, and the basic response of those measurements in the treble were a bit improved over what I was using before. Not much, but they certainly weren't worse.

 

[microstrip]

I agree the standard spec looks designed to impress falsely. I had read that these amps worked well with some difficult loads while sounding good. Yes plain old anecdotal reports. So I had my eye on them. One of the reps at W4S was asked and provided more detailed specs on a forum. I think it was on the AVS forum. Then I ran across a small site that had measured them (and where the same measures were done they matched pretty well with W4S claims). Most troubling is most of the specs don't specify 20-20khz results, but the extra info did. I was concerned the output filtering in these amps would match badly with the low treble impedance of the Soundlabs.

The specs are deceptive in that the amps have about half the advertised power at 20 khz. The output impedance goes up some, but actually stays as low as or lower than most other SS amps with frequency. Another oddity is the 500 wpc channel version has a small amount less steady state power at high frequencies than its smaller brother (the 250 wpc version I have). I wasn't too worried about lesser power as the treble levels are usually low as long as it didn't upset the amp to have very low impedance at the treble.

So I had hopes it would work pretty well, and specs that fit with what I needed with a couple of possible issues. I gave them a try and they worked out fine. They seem much less bothered by the load than a couple of quite hefty conventional SS amps I have used.

I have measured phase and impedance of my speakers (these basically are M3's internally and as far as the panel goes). Not the efficiency. I don't believe I measured the output in the treble with this amps at the speaker terminals. I do use a Tact for room correction, and the basic response of those measurements in the treble were a bit improved over what I was using before. Not much, but they certainly weren't worse.

Thanks, but your answer does not provide any factual data that can help in our debate - a few goes up, goes down, hopes, but nothing that could be used to know how the amps sound with that astonishingly tortuous and unusual load - the SoundLab. What is the version of your crossover?

I have to say that after 25 years of SoundLabs and many exhaustive measurements I still have to listen. And I do not make guesses - amplifiers that were supposed to sound good sounded miserable and a few that should not be able to move them sounded great. "I gave them a try and they worked out fine", as you say, his the most important aspect!

 

[microstrip]

Micro, if you are referring to me, tomelex, I would like you to either find anywhere on this site where i said changing a cable or interconnect is not audible, or immediately retract your statement!! I have always been very careful to state that weird cables and interconnects are often used as tone controls and gone into a great deal of technical reasons why folks hear differences between extremely different (uh, that would be a lot of so called high-end stuff) cables and interconnects

THANKS IN ADVANCE !!!!!!!!

Tom

My apologies, I was thinking about normal cables, not weird (!) cables. But as my post it could give a false idea of your position I just corrected it. Welcome to the superstition team!

 

[esldude]

Tom

My apologies, I was thinking about normal cables, not weird (!) cables. But as my post it could give a false idea of your position I just corrected it. Welcome to the superstition team!

Yes, weird enough conditions can make cables matter. But the great majority of hifi systems don't have those. Phono cable on a TT oh yeah it matters. Not exotic material or expensive construction. But capacitance effects the FR of the phone cartridge.

 

[Mark (Basspig) Weiss]

Hello Basspig, you wrote
"I will measure whatever people are willing to haul into my shop"

I won't be asking you to bring anything into your shop, but to show a measurement of your freq response. I can assume that you use REW or another measurement system. If so which one?
If using REW would you be so kind to post the m.dat of your bass response? And a full range response?

Also which SPL meter do you use for testing?

Thanks,
Wendell

We're discussing vacuum tube amplifiers. REW is irrelevant. I use HP spectrum analyzers and Tektronix distortion analyzers, audio generators and true RMS digital meters to measure power and relative dB referenced to a 1Khz tone, into a resistive load bank.


As for my own sound system, I did run some REW response curves back when I was on Windows XP, though my room suffers from a standing wave at 36Hz, the rest of the response curve was pretty flat from 14Hz to 18KHz. Now that I'm on Windows 7 64-bit, I cannot get REW to run. It installs, but I can't interact with its UI on Windows 7, so I'm unable to make any new measurements. Another item on my 'someday when I have free time' fix it list.

My sound level meter is a CEL 214/1, whose top measuring range is limited to 140dB. I've been looking for something that goes higher, though it's not a major priority and cost is a factor.

 

[Mark (Basspig) Weiss]

Sorry but look and see how many designers in those days learned their craft in the military--and if they did go to school--went on the GI Plan.

Second, if you think the old tubes amps sound better than present day models from cj, ARC, VTL, VAC, CAT, etc., then all you are listening to are euphonic colorations. Come to think of it, have you heard a new tube amp from any of these companies? Or what *botique* amplifier are you talking about? BTW, let's call them what they are, high-end audio companies.

So far, I'm basing my evaluations on offerings from Jadis, McIntosh, Altec and Carver, as those are what I've been able to physically evaluate.
And yes, the newer ones have more limited bandwidth and higher distortion at bass and treble ranges and that's all due to deficient transformers. Perhaps SOMEONE out there is making a good transformer, but I've yet to have one pass through my lab. So far, Altec and McIntosh are leading.

 

[MylesBAstor]

So far, I'm basing my evaluations on offerings from Jadis, McIntosh, Altec and Carver, as those are what I've been able to physically evaluate.
And yes, the newer ones have more limited bandwidth and higher distortion at bass and treble ranges and that's all due to deficient transformers. Perhaps SOMEONE out there is making a good transformer, but I've yet to have one pass through my lab. So far, Altec and McIntosh are leading.

And what's the relationship between power and output transformer bandwidth?

 

[microstrip]

you are a gentleman. on we go!

Thanks Tom. However can we know if cables from Shunyata, Nordost , Straighwire and Audioquest are , in your opinion , weird cables?
Most of the time people consider that networked cables are weird, even before measuring them. A clear manifestation of superstition, don't you think so?

 

[microstrip]

Yes, weird enough conditions can make cables matter. But the great majority of hifi systems don't have those. Phono cable on a TT oh yeah it matters. Not exotic material or expensive construction. But capacitance effects the FR of the phone cartridge.

Can you define "weird enough" in terms of objective entities?

 

[MylesBAstor]

Yes, weird enough conditions can make cables matter. But the great majority of hifi systems don't have those. Phono cable on a TT oh yeah it matters. Not exotic material or expensive construction. But capacitance effects the FR of the phone cartridge.

Really? For MC cartridges? Hardly. Only for MM or MI cartridges.

 

[Atmasphere]

Woah, one of these statements really got my attention!

Now there is the area i want to comment on, in bold and then in underlined.

As far as the bold, there are measurments unknown to us, with a simple audio signal? I am wondering just what you mean, or am i taking something out of context here? My background has exposed me to a lot of measurment gear, and i am convinced there aint nothing in audio signals that cant be measured. I am not referring to the stuff published by the audio manufactuers as all inclusive by any means.

As far as the underlined, yeah, we dont know much at all, but we do know that personal preferences are unassailable in any event.

Yes, I think we all know about the physical measurements. The problem is we don't know much about how our ears translate sound into a signal that travels on nerves, and we know almost nothing about how the brain processes music.

But it clearly does. We do know that limbic system processes music initially. However if the limbic system runs into problems (IOW finds that something about the sound is unexpected such as a violation of rules that it uses) the processing transfers to the cerebral cortex. There is a tipping point for that, but its not known how that works. But this does seem to have something to do with why some equipment has an 'emotionally involving' aspect whereas other equipment does not.

So it would appear that understanding human perceptual rules and designing equipment to honor those rules will result in playback that will sound better. That is the greater context of that short statement.

 

[Ethan Winer]

Now that I'm on Windows 7 64-bit, I cannot get REW to run. It installs, but I can't interact with its UI on Windows 7, so I'm unable to make any new measurements.

Just so you know it's possible, REW runs on my Windows 7 64-bit computer with no problem. Do you have the current 5.0 version?

--Ethan

 

[MylesBAstor]

Millennia Music & Media began formally as a classical music recording engineering and production company. We have recorded nearly 1,000 symphonic orchestra sessions and a much larger number of chamber orchestras, small classical and jazz ensembles, soloists, and more. Millennia continues to engineer a significant number of location recordings each year; working with many of the world's finest classical musicians.

Early on, we realized that most pro recording gear exhibited sonic colorations which limited our critical acoustic recording objectives. This general dissatisfaction with "off- the-shelf" recording products has inspired us to design our own uncompromised critical signal path. To assist our design efforts, we developed sensitive and repeatable laboratory methods to distinguish subtle sonic differences between small changes in circuit design.

Millennia employs a 40+ kHz analog listening environment in which critical audio circuits are scrutinized with live acoustic sources, including bell tree, voice, and cymbal. Sources are chosen for their complexity and difficulty & we've found that complex high frequency "partials" are the most difficult to reproduce accurately in audio circuits. We continually and alternately reference the original source in acoustic space while comparing it with a circuit under test. Each new circuit design or modification is compared with former designs:

Where are the new shadings? Where are the timbre shifts? Is it more accurate, less accurate, or just different? In which part of the spectra are differences occurring? What are its dynamic characteristics (changes in timbre versus changes in level)? What changes to circuit might improve accuracy?

Each successive circuit is also objectively characterized on one of our Audio Precision System One and Dual Domain test machines. All parameters of distortion, noise, common mode rejection, etc., are measured and logged.

There's something we encounter again and again in our tests. Similarly measuring circuits (THD, noise, frequency response, etc.) often exhibit dramatically differing sonic signatures - especially in the critical upper frequencies. As such, specifications are a guide, but are not indicators of sonic performance. The only way to learn how an audio circuit really sounds is through first-hand critical listening.

Of course, even controlled listening tests are not without variables. Every element in a fixed reference chain adds its own personality. Over time, the engineer who comes to rely on this path learns to "listen through" inherent shadings and subtleties. We feel that our unique test environment has provided the tools to produce exceptionally accurate audio circuits.

Please call us directly if you would like to learn more about the specifics of our listening lab. We have recently expanding the lab into a dedicated 6,000 cu. ft. room with 9" thick concrete walls, isolated floor/wall/ceiling structures, and a carefully controlled ambient behavior. The prime structure was designed by acoustician George Newburn, formerly of "studio bau:ton" in Los Angeles and now Chief Acoustician at "Studio 440," an acoustics design and consulting firm.

Alas, lab listening tests go only so far. Which is why, when we arrive at a favorable design, the device is taken into the field for months (sometimes years) of real-world testing. New candidate circuits are employed during rehearsals and live sessions, where dynamic stability, imaging, and ambience retrieval can be auditioned later in our listening room.

When comparing audio circuits, especially mic preamps, take time to discover the personality of the design. Use complex radiators in comparison - continuously alternating your listening perspective between the circuit path and the actual source in real time acoustic space. Use a mono source when comparing timbre accuracy. You'll begin to notice the "shadings" and nuance of different circuits. What at first sounds "more open" or "lively" is very often a euphonic coloration or subtle exaggeration in the upper partial frequencies and low-mid "warmth" region. It takes practice.

Listen especially to how a circuit performs at high dynamic levels. Very often, a good performing circuit at low to moderate operating levels will change character at high levels. This is especially true of transformer-coupled microphone preamplifiers, and those requiring attenuators (pads) to reduce input excursions.

As you'll find, it's often difficult to detect if a circuit is more musically accurate, or simply more colorful, lively, and "tweaked." There is a place in audio production for many kinds of preamp coloration; but for critical acoustic recording, musical accuracy is a requirement.

Which brings up an important point - not everybody desires accuracy. Audio circuits in use today can offer wonderful shades of coloration. Some of these audio devices are described variously as sounding "warm, in your face, round, euphonic, bigger than life, cutting, thick, soft, rich, bright, powerful" and so forth. And in pop music, these qualities are often essential tools for hit records. The Millennia HV-3 circuits do not offer these qualities, but micamps from many other fine manufacturers do. Millennia uses many of these other products for pop recording or special situations, including a wide assortment of "colorful" mic preamps from other manufacturers.

However, for those recordings where the room is correct, the instruments are beautiful, the players are first rate, and the music needs no further assistance, there is no substitute for accurate audio electronics. If it sounds luscious in acoustic space, Millennia Media electronics will simply not interfere. Assuming a fine electronics path overall, you will hear on speakers a presentation of music which your ears hear in acoustic space. At all dynamic levels. At all frequencies. With undisturbed acoustic complexity and subtlety

guitar
Learn about the next generation of sonic purity and musical accuracy in reducing 20 and 24 bit digital audio signals to the 16 bit CD standard.

Tips on Selecting a Microphone Preamplifier








Don't let anyone tell you that accuracy = sterility. If you do acoustic recording where your sources sound good (guitars, voice, percussion, acoustic ensembles, good room, great mics.. .), and there is no reason to mess with the source signatures, an accurate mic preamp will deliver the richness, depth, presence, air, ambience, and more of those original qualities you're looking to preserve, with nary a trace of electronic artifacts.

Be wary of the recent flurry of "textbook" designs using preamp function IC's, such as the Burr Brown INA-103 "transimpedance" amp, Analog Devices SSM-2017, and ultra-high speed video op-amp ICs. Video opamps are designed to carry video signals and are not optimized for audio. Certain specifications may be very good - especially "speed" (slew, transient impulse, and frequency response). But, as we've learned, specs rarely translate into sonic purity. This is especially true when applying video parts and "IC function modules" to critical audio. Listen carefully to upper partial frequencies and large dynamic excursions in such designs. For a revealing look at today's high gain technologies, see our non- technical white paper on the design of microphone preamplifier circuits.

Some other general design aspects to watch for when choosing an accurate mic preamps.

Transformer Coupling

While transformers offer better circuit protection and isolation than transformerless designs, they nevertheless present one additional layer of sonic personality. The best transformers are quite subtle at low to medium levels. Yet there is no transformer we've used which can rival the transparency of well-designed transformerless inputs & especially under higher dynamic range. Of course, sometimes transformers can offer a very desirable coloration. Some good examples are found in Rupert Neve's original Class-A designs (models 1073, 1272...) and a number of vintage and modern tube preamps. However, a transformer-coupled mic preamp, EQ, or any other signal path claiming "accuracy" should be approached with caution.

The Millennia HV-3 octal matched NPN discrete front end is protected by back-to-back zener diodes. With common care, the protection afforded is ample and authentically transparent. We have invested significant effort listening to AC coupling (phantom blocking) methods. Exotic poly caps and electrolytics (or lack of) do not necessarily translate into sonic reality. Our HV-series coupling method was painstakingly chosen as a matched set of very low impedance, high voltage electrolytics bypassed with polyethylene terephthalate film capacitors. In our final designs, we found nothing more dynamically stable and musically satisfying. When AC coupling is not required, such as when using ribbon or other dynamic microphones, all Millennia micamps can be acquired with an additional set of DC-coupled inputs.

Input and Output Headroom

Textbook mic preamp designs always require a pad (attenuator) at the input for hot mic signals. And there are very few micamps which can handle severe input levels without clipping. Millennia's HV-3 solid state micamp design is entirely balanced in a unique cross-coupled topology which requires no padding & input headroom is > +23 dBu. The Millennia mic preamp will simply not distort or overload even at extreme peak microphone levels.

Our unique approach to preamp design avoids the need for mic padding and the associated switch contacts and resistive dividers which can add another unnecessary layer of coloration and potential signal degradation. Moreover, Millennia's output headroom is > +32 dBu, which is well over twice the reserve headroom capacity of common textbook mic preamp designs. The autosensing, DC-coupled, high current output stage is capable of balanced or unbalanced operation and provides effortless performance into very low impedances and very high capacitances.

The most severe test of a preamp output stage is driving long lengths of multicore "snake" cables (high capacitance) in a hostile (RF/EMI) environment. Does the preamp maintain its stability and neutrality under these conditions? Perhaps the most grueling test so far of Millennia's preamp output stage came during Barbra Streisand's live CD recording at Madison Square Garden. Sixteen channels of Millennia preamps drove nearly 1,000 feet of Belden multicore cable which was then transformer split to FOH, video truck, and multitrack recorders. Some of today's leading engineers were on hand to handle the various feeds. The consensus was unanimous: the Millennia Media preamps sounded just as accurate in this harsh environment as in a controlled studio environment.

Design Philosophy

Often, designers will add phase reversal, ground lifts, and other utilities to their mic preamplifiers. Yet switch or relay contacts directly in the audio path can add another level of subtle audio shading and, over time, even the best switch and relay contacts will eventually degrade. For this reason, our HV-3C and HV-3D micamps avoid audio-path switch and relay contact closures whenever possible. On the infrequent occasion when such utility functions are required, we recommend that our customers carry a little collection of Switchcraft or Neutrik XLR "thru-tubes" which have these functions built-in.

 

[MylesBAstor]

Large Ensemble Listening Test Tutorial
Mondavi American Bach SoloistsMany have asked us for a “tutorial” series on large-ensemble acoustic recording. Perhaps the best way to convey the performance of different recording techniques is to simply listen and compare. This is the first in an occasional series of real-world recording discussions and audio examples from Millennia Media.

We’ll be listening to samples from a live performance of Handel’s Messiah by the American Bach Soloists. The ABS, playing on period instruments, is among the world’s finest “baroque style” orchestras. A mix of this recording was released on the Delos label (DE-3360).

Rarely (if ever) in my audio career have ALL the ideal acoustic production elements shown up in one place: a truly masterful performance in a world-class recording space captured with extremely realistic engineering techniques.

Producer and Music Director Jeffrey Thomas has allowed the “intangibles” to flourish: organic, human, visceral qualities that are so often lacking in "overly formal" acoustic music, especially Messiah readings. This recording seems to have it all. Choir dynamics and intonation are stunning; ensemble pacing and phrasing is masterful; choir and orchestra gel as one living instrument.

Twenty microphones were arranged on stage (mic chart). We’ll be comparing the acoustic properties of multi-mic versus two-mic recording technique. The main stereo microphones heard on these recordings are a pair of Josephson 617 bodies with Gefell MK-221 omni measurement capsules. Recorder is a Radar S-Nyquist sampling 44.1 kHz @ 24 bits1. A quad of 130 volt DPA 4012 mics are positioned on choir. All mics are fed to Millennia micamps. Mixes were produced on a Sequoia v8 workstation. Word length reduction (24 to 16) is via POW-R #3. Stereo pair recordings are unprocessed, straight from RADAR, natural room reverb.

The main stereo mics were fixed 290cm above stage floor, spread about 45cm wide, pointed about 45 degrees off center (left and right), and pointed about 20 degrees down from stage parallel. This effectively splits the orchestra for even acoustic coverage – recall that omni mics are not omni-directional at all frequencies, hence point does matter.

Stereo Array and AEA 88 TestThe DPA 4012 high voltage mics were stationed evenly about the choir 340cm above stage floor, with choir on risers. Point was nearly straight down into the heart of each choir section and slightly to the choir’s front.. Vocal soloists (Daniel Taylor - Countertenor, etc.) used Josephson 606A-KM25 hypercardioid mics. Mics were placed about 70cm in front of vocalist, about 30cm down from mouth height, and pointed up appropriately. Mics were placed down from mouth plane not for sonic purposes but to give better audience line of sight. Ideally, we would want to be tighter on axis.

Here are comparison audio examples of the identical performance captured with raw two-mic and mixed multi-mic techniques.
Recording Examples Stereo Pair Only Multi-mic Mix
Glory 16/44.1 MP3 16/44.1 MP3
Child 16/44.1 MP3 16/44.1 MP3
Goodwill 16/44.1 MP3 16/44.1 MP3
Daniel T 16/44.1 MP3 16/44.1 MP3
Yoke 16/44.1 MP3 16/44.1 MP3
Interlude 16/44.1 MP3 16/44.1 MP3
Amen-end 16/44.1 MP3 16/44.1 MP3

The debate over “pure” stereo orchestral recording versus multi-microphone mixes has raged for decades. Here’s a rare opportunity to hear both simultaneously as a controlled experiment.

We all know examples of poorly executed examples in both “purist” and “mixed” categories. Often, two-mic recordings employ widely spaced (Large AB) omni’s, offering a tremendous sense of orchestral spaciousness, but sacrificing accurate stereo imaging and stage placement. Conversely, coincident two-mic orchestral techniques (XY) can deliver exceptional spatial imaging, but often at the expense of a flat and lifeless ambience and loss of depth.

In this Messiah production, we chose closely spaced omni microphones (Small AB) as our main stereo pair. We find that this is often the ideal “tradeoff” between orchestral space and imaging. Even though we had numerous mics open, I estimate that >80% of the mixed program remained on these two microphones. Alas, this is often a hallmark of convincing mixed orchestral recordings – spot mics are used gently and sparingly, like spice.

Some of the finest contemporary examples of mixed orchestra are found in the motion picture industry. Today’s leading movie scoring engineers include Shawn Murphy, Bob Fernandez, Simon Rhodes, Dennis Sands, Steve Kempster, Armin Steiner, Alan Meyerson, Michael Farrow, Frank Wolf, and John Rodd. Record companies, such as Telarc International, are also making fine multi-mic recordings, with engineers like Michael Bishop, Jack Renner, and Tony Faulkner leading the way.

This of course brings up the subject of “Surround” orchestral recording, a topic that will hopefully be covered in future discussions. Please let me know if you have any questions about this recording, or suggestions for future discussions and audio examples. I will get back with you. Look for more tutorials in the future – including comparisons of our recordings with:

- Russian National Orchestra
- Academy of St. Martins in the Fields
- China Philharmonic Orchestra


Tour the Mondavi Performing Arts Center
John La Grou
Millennia Media, Inc.
California, USA

http://www.mil-media.com/LargeEnsembleListeningTest.html

 

[rbbert]

So far, I'm basing my evaluations on offerings from Jadis, McIntosh, Altec and Carver, as those are what I've been able to physically evaluate.
And yes, the newer ones have more limited bandwidth and higher distortion at bass and treble ranges and that's all due to deficient transformers. Perhaps SOMEONE out there is making a good transformer, but I've yet to have one pass through my lab. So far, Altec and McIntosh are leading.

Are these representative of today's better (much less best) tube amps? I don't think so, although to tell the truth I wasn't aware that Altec was even making tube amps, at least not in the last 40+ yrs.

 

[Atmasphere]

^^ I think that is his point, that the old Altecs had a pretty good output transformer. So did the HK Citation 2.

 

[rbbert]

^^ I think that is his point, that the old Altecs had a pretty good output transformer. So did the HK Citation 2.

But he only has "the" Carver (among current tube amps) to compare to? Which Carver? Not very convincing, to say the least, even if his underlying premise turns out to be true...