Category: Equipment

On Real Music or Lack Thereof

A common thought among many is that today’s pitch and/or time corrected music is not real. In some ways, this makes sense in that its artificial enhancement, as contrasted with live playing. On the other hand, I’ll argue that today’s music, with all of its technical enhancements is even more real than what we had prior to the digital world.

The reason for this, is emotional content, music from the heart so to speak. Back in the days of tape, it wasn’t unheard of for some tracks to require a ton of takes, in some cases, maybe even 30 or 40 of them to get a pristine version. The problem of course is that such gets pretty fatiguing on the part of the musician, and emotional content starts to wane. In todays world, maybe only a few takes are needed such that digital enhancement can take care of the rest. Such presents emotional content in a much more raw and pristine fashion, even if the technical aspects need correction. As such, the potential is there not only for real music, but music thats even more real than what we had in the multitrack tape era. Yes, I fully get that a nearly untalented individual can be pitch and time corrected, and that seems a bit shafting to the audience… but music much is much more than technical accuracy.

If real is what one is truly shooting for, I tend to think the very early era of wax cylinder recording is probably the answer… there was no possibility of digital correction, or even multiple passes with such systems. Pretty much each recording sold required the musician to perform it, with quantities limited only by the fatigue of the musicians in combination with number of parallel recorders one had available. Alas labor costs being what they were, the process soon morphed into recording one master, which would be played and linked with rubber tubing to provide inputs to multiple recorders at the same time… so yes, not very high in the fidelity realm.

The thing is, at some point or another, technology will evolve to create emotional enhancement… or even emotional masking, at that point, I think the concern over fake music would become very real very fast. Granted, such an approach, just as pitch and/or time correction is asymtotic, ie, it will get closer and closer but never get there. Alas, just as rubber tube recording was good enough… maybe time, pitch, and emotional connection will good enough, and what then???

I think we already have the answer… live, in your face music. Its as real as it gets, its where the greatest value of music truly lives, and I think the market is already pointing us in that direction. Alas, it will not be without its own set of expectations and challenges.

Mic Preamp Design & Headaches

I wrote this about 5 years ago, and just came across it a couple days back. I’ve got another mic preamp circuit I’m playing with, and figured I best go back through my old notes to avoid wheel re-invention.

Why is it that the only decent preamps were made back in the 70’s…

I’ve been fighting this for almost 2 years. Hundreds of hours of messing around trying to get the right mic preamp. When I started this project, I mistakenly thought, how hard can it be. After all, its just audio. And at this point, maybe thats the issue, its just audio!

I’ve designed thousands of boards over the last 30 years, first as a hobbyist, than as a U student, and then as an engineer. Some boards were super high gain, and super low frequency, and others were GHz boards. Audio should be a calkwalk, and its not.

The biggest issue turns out to be phase shift. Noise is solvable, as is gain, and THD. One can deal with dynamic range pretty easily if the other 3 factors are handled appropriately. Where I end up getting bitten is the transfer function of phase shift, THD, and dynamic range as a function of frequency. It seems none of the commercial mic amps want to spec this… and with two good reasons. First, for those who understand it, they would be scared off. Secondly, most people don’t understand the phenomena. The problem is that whether a person understands it, or just reads it in a spec sheet, it makes little difference…. the issue is folks can HEAR it.

More on this rant later, gotta go eat

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updated 2/27/06

Part of the deal is the cost of labor. In the 70’s common practice was to test select parts. This usually meant matching transistors and even transformers and in a few cases, not by test gear, but by sound during the final test stages. Today, most assembly houses would have a bird if you asked them to test select, and would no bid it if such required a listening test. The 70’s often required a craftsman at the test bench, and today with its penny pinching models, most of the test techs are not at that level. They want speed and throughput, and any drive and patience they once has been driven away by bean counters. The mic preamp of the 70’s is not a commodity like today.

In addition, one would like to think that non-discrete solutions such as the TI INA163 upgrade to the SSM2017 would be an even better solution that the TL074 of years past. In fact, the SSM2017 is still often designed in, even though the INA163 has better specs. There is a lot that goes on in chasing ones tail in audio. A proven pcb layout is hard to beat, and to rip up/redo a SSM2017 layout may well equate to multiple spins to get equivalent performance in the INA163, and even more spins to get the mfgrs speced performance out of it. Remember, we’re not just chasing audio performance, but in commercial gear, we also need to meet EMC standards, which often times make for really messy compromises between the audio and RF domains.

One other thing that comes to mind is servo control of the ground, and DC coupling the audio to minimize phase error. Walt Jung had a number of papers on this in the early 90’s. On the outset, this seems a better solution than transformer coupling and its high cost and space requirements. On the other hand, a properly engineered C-Core transformer is near impossible to out perform spec wise… so it all comes down to economics, and one can buy a whole ton of op amps and discretes rather than a $12 C-Core at 10K/yr. Perhaps the saddest part of this, is economics often dictates letting the phase transfer functions slide all over the place. For most apps, if the other parameters are likewise under control, if the phase varies, its not all that big of a deal… but then again this is the 2006 not the 1970’s.

Capacitive Switching of Pedal Boards

ImageI’ve been thinking a bit about the common pushbutton switch such as the Carling 110/316 series. They’ve been the standard effects pedal switch for years, albeit some outfits use cheaper knockoffs, likely to their peril. The nice thing about such switches is the great feedback they provide, even if one has a really thick boot on. Another great feature is their non-teasable nature, ie the contacts operate on an overcenter mechanism, so chattering on opening or closing is near impossible. Likewise, they are self cleaning via contact wiping.

However, if someone flings a beer, or worse, someone puts a beer on an amp, (where it is guaranteed to tip over) and you get beer in the switch, the party is likely over.

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This problem is somewhat mitigated by using a hinged cover plate over the switch such as in some Maestro pedals of years ago. Then again, hinged cover plates, whether custom extrusions as in the Moog, or plastic as in the FCB1010 serve to add extra cost. In addition, while deflecting most of the beer, ingress is still possible.

Capacitive sensing works wonders as far as providing a beer proof switch. Likewise, inductive, or even magnetic sensing can do well in the volume/wah pedal arena as far as beer proofing.

A big problem with capacitive sensing is providing feedback to the user. A LED status light while helpful is no where near as good as the massive tactile response one gets from a Carling 110/316. A possible solution to provide feedback in addition to an LED is a shaker solenoid, such that at actuation, the musicians foot would receive tactile confirmation.

Another problem is the issue of teasing, where in the over center action of a Carling 110/316 reigns, and capacitive sensing crashes and burns. Ie unlike most other apps, one cant use a long debounce time in a music application or you will aggravate the musician to no end. Adaptive tuning of the capacitive switch may or may not be an answer to this issue.

Lastly, there is the issue of musician preloading. Ie, its common practice for a musician to rest their foot on their pedal just prior to actuation. Again, adaptive tuning of the capacitive sensor may be an answer, although at this time, a mostly mechanical approach in addition to tuning on the fly seems more reasonable.

Harmonica Microphones

I came across the following from tymkrs where they discussed harmonica microphones. There seemed to be some somewhat contradictory info on google, so I asked them for some clarification. In a matter of 20 minutes, they sent me a link on the internals which filled in a lot of the back story.

A little bit of further digging, and I found out a bit about the fabrication of rochelle salts. Its a fairly old school albiet simple method of crystal growing… and it got me thinking a bit more. Ie, how are the lead wires attached, and how is the rochelle salt protected from damage.

A little bit on google patent search provided the Astatic Corps patent. Like many things of that era, labor was inexpensive, so the emphasis was more so on consistency than labor saving. In addition, the variety of materials to use in manufacturing was pretty limited.

Ultimately, this little bit of digging tonight opened up a huge number of ideas, not only in the microphone domain, but also for percussive sensing including instrument keys.

Digital Can Come Back to Bite

Tdawn shared the following AES paper titled “Stop Counting Samples” on twitter, and it confirmed a whole multitude of things I’ve run into over the past few years. In a nutshell, digital audio is a vastly different animal than analog, especially post mastering, and if such is not considered, it will come back to bite, often in a huge way. Whats perhaps most distressing is that multitudes of young engineers grew up on digital, and yet it seems, and is shown in the analysis of recordings in table 2, they are blowing it.

Historical Hot Recordings

Back in my day, if you cranked up the levels too high, waveforms would get their peaks clipped and as a result, multiple harmonics of said waveform would result. In addition, the B-H curve / saturation characteristics of mag tape can make for some really interesting types of distortion, (and it approached with moderation, might even be considered pleasing to some folks ears).

Digital Music is often Subject to Post Production Processing

Digital post production processing is very common. On the one hand, it could be tricks used within a mp3 player to save silicon die space, on the other it could be tweaks used to optimize streaming audio, or even OTA broadcasting. Post production processing assumes that the input signal is good to go… When the input signal has digital artifacts, even if normally not audible, when you post process such, they can come back in spades. Fig 7 shows how this may occur in a huge way.

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Note the 5.5Khz tone… and the big spikes in spectral content mirrored above AND below 5.5Khz.

When it such shows up, outside of a sine wave in the lab, is that something may have sounded perfect in the mastering room, and even on a few different pieces of equipment… but a slightly different CODEC / re-sampling methodology in the customers home, and boom, all bets may be off.

Whose problem is it, artist or listener?

Granted, there likely are some folks who take the stance of, hey its good to go here, and if a customer plays it back on something else and the quality takes a dive, its their problem. I can sort of understand such… but then if a customer buys music, and has a bad experience, are they likely to blame the musician, or blame the signal processing going on in their device. More than likely, the musician is going to be the one taking the heat…

What about live recording?

Now, consider a recording of a live performance, where the musicians are using DSP amplifiers on stage for psycho acoustical effect. Micing such amps and then bringing them into the desk in addition to a direct feed for effect would seem to be all analog… but is it really? What about leakage into the vocal or crowd mics? Can such bite? Perhaps… the key is being careful throughout the entire signal path, and testing. Assumptions more often than not in the analog world worked out fine, and in many cases were a positive. The digital world is different, and if left unchecked, it can bite with a vengeance.

EMC Electronic Music Corporation Info Requested

EMC made some interesting gear during the 70’s… and had something truly amazing, a lifetime guarantee! Of course being they went out of business prior to 1983 the lifetime part ended up being pretty short.

The S300 Guitar Amp had the following specs:Image

  • 125 Watts RMS
  • 5 band EQ
  • Reverb
  • Portable.. yep, it only weighed 90lbs!

 

EMC was located at

21819 Royalton RdImage

Cleveland, OK

Per google maps, the current building at that address is huge. Either they were really that big, or they just rented a portion of said building.

 

 

Beyond the S300, they also had a G200 and a line of PA systems.

In my first band, we had a EMC Gemini PA system, it was a 6 channel unit, and it had to 2 columns with 4 eight inch speakers in each one. It sounded ok, but when we paired it up with some homemade clones of a Peavey SP3, it could really rock.

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Granted, such a unit was of no comparison to the next group I was in where we had 4000Watts triamped, and 4 speaker columns reaching nearly 15 feet high… yet, for the average bar or small club, the Gemini did a super great job.

Tuck and Roll Amps

Many years ago, I had the opportunity to buy a Kustom Tuck and Roll Bass amp for a song, but being shy on cash, passed it up. On the other hand, it was the standard model, but had it been the red glitter one, I would have jumped a ton of hoops to make it happen… yep, I always thought it was super cool. Image

Its an interesting thing to consider tuck and roll as a covering in contrasted with tolex (textured vinyl), or todays textured polyurethanes (rhinolining and related coatings). Beyond its unique visual appearance, tuck and roll has some technical advantages. If one is hauling an amp in ones car, the sliding nature of tuck and roll on automotive upholstery makes life significantly easier. Having moved a ton of amps over the years, a buddys 2×12 tuck and roll cab is a lot easier to load into a sedans back seat, than a 2×12 tolex cab. Secondly, the real tuck and roll is incredibly robust, and easy to clean up too (granted, it does look really bad when folks leave a lighted smoke on top of it, or if pyro gets out of hand). Thirdly, it can also serve as a dampening material to reduce cabinet resonances… albeit testing would need to be done to see how much internal dampening material could really be removed.

However, like many things today, labor rates pretty much make real tuck and roll obsolete, except for purposes of restoration, or boutique amplifiers or cabinets. Yes, tolex is more labor intensive than spray on coatings, but its light years easier than traditional tuck and roll. That being said, there are some compromises that could be looked at.

DIY or possible Boutique Revival of Tuck and Roll

The lowest cost approach is what is called pleated vinyl to simulate tuck and roll. Depending upon the vinyls formulation, and heat sealing process, it might be on, but it will have a shorter life span than traditional tuck and roll. Many upholstery stores can provide such at around $25/yard. Its also available online at Garys Upholstery However, colors are pretty limited, and its lifespan is an unknown.

The next step up is channel quilting through the foam to simulate tuck and roll. Such is a lot less labor intensive than real tuck and roll… but there is a lot of tension on the single row of stitches, and for an amp or can which doesn’t travel much, it might be ok. A really decent approach to DIY this approach is located at Jalopy Journal. Being vinyl can be bought anywhere for such a project, the sky is the limit as far as color goes. Even blue sparkle is available.

For a more robust tuck and roll, which uses hidden stitches and heavier thread, a couple of automotive books come to mind. The Auto Upholstery Handbook by Don Taylor is a good one, as is Custom Auto Interiors by Ron Mangus and Don Taylor. There are a number of ways to approach tuck and roll. One could either sew the pleats and stuff, or actually tuck under and roll over the foam (depending upon ones sewing machine and skills).

The key though, with any of these approaches is small scale testing first. You dont want to spend a fortune on material, only to find out its no where near as good as its specs would lead one to believe. (assuming the material you get actually has a spec sheet). Ideally all automotive upholstery would be UV stable, fire retardant, abrasion resistant, and water resistant, but after market wise, specs can be all over the place. A good engineering reference for vinyl is ASTM D3690 which you can either purchase from them, or acquire from a large university library (older versions are likely more than adequate. Granted, for most folks, even boutique builders, ASTM quality standards would be overkill.

Its the same deal with the foam… there are hundreds of types of foam, and the cheapest you get from a discounter is unlikely to be the optimum long term. For engineering specifications wise, ASTM D3574 is key, albeit there is a lot of material going far beyond the needs of a speaker cab.

Lastly, should one wish to take this on, there is the issue of equipment and individual skill development. The learning curve can be a bit steep, so its always best to start out small scale first should one wish to revive this very unique approach to amplifier and cab covering.

Finale Notepad is $10, but the 2008 version is still free

I’ve been playing around with notation software a bit, and actually found Finale’s Notepad to be pretty cool… and then my pc did a crash and burn. As such, in the process of bringing it back to life, I found my backups of the programs was lacking in a huge way… thus time to go and redownload as much as I could still find.

Its cool that the link to Notepad 2008 still exists on Finales website, and you can get the serial number too. Sadly the file download didnt work, but a bit of googling, and I found np2k8win.zip on a number of filing sharing sites. Of course, such is a bit of a pig in a poke, who knows what might be mixed in with it… so either spend $10 for Notepad 2011, or cross your fingers and run antivirus/malware checks on what you download for free. Either way, Finale Notepad is a way cool program.

For more power, Printmusic really rocks, as it can scan in print sheet music with really decent accuracy. If one adds a microphone, it will also allow you to go from audio direct to notation… a feature I think is cool, albeit dangerous lol. I haven’t tested it, but the cool factor may take me there in the future.

Automated Page Turning Tablet PC for Sheet Music

Last Sunday, I get the music for the 10:45 service at 10:20, where upon I find out I have a bass solo for the postlude. As one who over the last kazillian years mostly ends up sight reading live performances, this was not a big deal… except there was a page turn right in the middle of a fairly busy solo.

So, I cheated, I took advantage of one aspct of the fair use doctrine, and made an “emergency copy” of the flip side, such that I would not have to play a series of runs and manage a page flip all the while trying to sight read the peace. (Granted, I silently sight sing all music before I play it, such that the first time I play it, I’m already pretty familiar with how it goes).

After church, I was talking to the guitar player, and said “someone should make a thin, super light weight tablet pc” that would have some type of sheet music browser, with an Amazon ebook type link where you could download any and all types of sheet music in the world. Even better, such a tablet should have provisions for automating the of turning pages. He was thinking, yep, a IR, or bluetooth foot pedal would be cool… I went one further, and said, why not have the tablet pc listen, and then automatically turn pages. We both joked about how such could turn into a nightmare pretty fast.

After a week of thinking about this… perhaps not. Back in my days of seismology, my buddies and I could see that if there were ever enough computing power, it would be possible to correct out of tune notes on the fly. Too bad we didnt run with that idea… I bet lots of seismic guys thought the same thing, but only Andy Hildebrand took the blue sky concept and turned it in something other than a discussion in the back of a vib truck.

Of course the big problem is not a technical one… its the sheet music business model. If an Amazon or Itune method of distribution were to arise, thousands of businesses would be in a real world of hurt. There is just too much money in, ordering, hoop jumping, dealing with paper, hoop jumping, printing, and, hoop jumping, and of course copyright enforcement. On the other who knows, maybe there will be a Steve Jobs of sheet music one day.

Monitor Mixer Controller Foot Pedal

Often times it would be nice to adjust the monitor mix on the fly… but alas, the monitor engineer can’t read minds, and I’ve never seen a on stage talkback microphone just to the monitor engineer. Of course a talkback mic isn’t much help if one is a vocalist either. The end result, levels are pretty much static during an entire song. The only exception being if one works out some type of hand signals with the monitor engineer.

In my situation… I dont have a monitor engineer, and often times its a challenge enough to handle page turns, much less run over to the monitor console to adjust the mix.

One concept… a foot pedal controller to adjust monitor levels.

Some features:

  • foot pedals to increment or decrement individual channel levels
  • highlighted LED bars with user customizable overlays indicate to the user which channel is being adjusted
  • a middle foot pedal which serves to select the appropriate channel to adjust
  • no master volume control on the pedal board, as that is set once at the main amplifier… ideally only individual levels would need tweaking. I may need to rethink this a bit. (its only a software and overlay mod)
  • output is digital only… in keeping with minimally invasive audio, I want to keep multiple audio signals off the stage floor as much as possible. (likely the data will be midi sysex messages to control a midi mixer)
  • a LED bargraph meter to provide feedback as to current level setting

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