Recording - February 2010 - 6

Note to faithful writers: When sending email to talkback@recordingmag.com, please remember to include your name and where you hail from. A warning on amplifier loading In our November 2009 article on the Hybrid Guitar Recording Method, Fernando Curiel wrote about using the Recording Out that’s available on some guitar amps to get sound into your computer. His original language was tweaked by the Editors for space considerations, and a couple of layers of safety warnings were scraped off in the process, which led to this reponse from a wellrespected guitar amp maker: STOP! Never, repeat NEVER, power up a tube amp without the proper load attached! On page 26 of the November 2009 issue, Fernando Curiel states, “And best of all, you don’t necessarily need to run out and buy a power attenuator to interface it with your computer ” Yes, he goes on to say: “Still, to avoid serious damage ” but I know guitar players only too well, and 90% think, “If it might work, why not.” And Fernando opened the door! Every amp varies on how much abuse it can handle, but you MUST have a load on the transformer. No ifs, ands or buts there. Some are very picky about the attenuator you use. Impedance is a very complex study and suffice to say a purely resistive load (think a bunch of high power 4 or 8 ohm resistors) isn’t always safe. In the good designs (THD’s is one) the impedance varies over frequency, just like a speaker. Tom Deering deeringamps.com Kent, WA Al: Most DAW software and controllers send a specific MIDI message when you hit Record—it could be a Continuous Controller or a MIDI Machine Control event, often it’s programmable. If you had a box that listened for that particular message and tripped a relay to turn on your light, that could then be adapted to almost any sort of DAW and your existing studio lights. At least one box already exists ready-made for this, from a reliable maker: http://midisolutions.com/prodrel.htm Alternatively you could scrap your existing system completely and look for something self-contained that just plugs into your PC, which saves effort. Let me know what you pick.—MM Al replied: Hi Mike, I ended up getting the RSPE Audio Solutions PunchLight Recording Lamp USB and it works prefectly. Just what I was lookin’ for. www.rspe.com/Metering-Studio-Displays/PunchLight.html Thanks for your help.—AB What do we mean by ‘desirable’ audio electronics? Hey Paul Stamler: I have a question in regard to your article “Good As New (or maybe better)” in the December 2009 Recording. I have been an audio recording professional for the last 5 years or so, and I’m about halfway through my Electrical Engineering degree at the University of South Alabama, so I’m not afraid of a technical answer. My question is this: on page 36, with respect to Figure 2, you write, “C5, C6, and C7 are where the rubber meets the road; here’s the place where you have the chance to upgrade the equipment’s original sound here I like to use the Panasonic FM series, which have characteristics desirable in audio circuits.” What makes these capacitors sonically superior? And further, what would you describe as “characteristics desirable in audio circuits?” Do you mean Neve-style desirable (“nice” harmonic distortion) or Earthworks-style desirable (super clean)? This subject is of particular interest to me, as I am beginning my foray into the world of audio nerdery with two projects: building a modified JCM800 and Pultec-style eq. Any illuminating thoughts on this matter would be greatly appreciated. Thanks so much for your time, and thanks for writing a meaningful article. Cade Cashen via email Fernando Curiel replies: Tom, thanks for writing and for your important warning. To restate: you don’t need a power attenuator to use the Recording Out of the amp, but that says nothing about what the speakers are doing at the time. Some amps let you turn the speakers down while still getting a hot signal from the Recording Out to your computer interface, while others demand that the speakers be at full volume. In the latter case, if you want to work at night or in a noise-sensitive environment, you’ll have to disconnect the speakers but for safety’s sake that can only be done, as you point out, if there’s a proper load attached in their place.—FC Another sort of warning Do you know of a Recording Warning Light Controller for Cubase, using a PC in a project studio? I currently use a manual switch, but this is not practical. I need to automate it. The Recording Light control surface plug-in would enable me to control an external light or sign, warning visitors not to enter the recording studio before or during recording. I need it to send a signal to switch on the external device when a track is record-enabled or when recording starts, and then switch off the device when tracks are made record-safe or when recording stops. I only use Cubase so I need this controller for that DAW. Sixerdoodle Electronics has an interface for SONAR, but, he told me, not for Cubase. Any ideas? Al Berntsen / Kekoa Grover Hummingbird Hill Studio via emailRECORDING FEBRUARY 2010 Paul J. Stamler replies: Cade: I’m usually erring in the direction of clean and neutral rather than sonically colored. The capacitors in question have nice low ESR (equivalent series impedance) and leakage, which are both good qualities for audio. I’m told they also have low dielectric absorption, but have no verified info on that. By the way, there’s a very interesting thread on the ProdigyPro “Drawing Board” internet forum about reduced distortion when connecting a pair of electrolytic capacitors in “anti-parallel”—parallel connection with opposite polarities. Samuel Groner includes a graph showing much reduced low-frequency harmonic distortion with this hookup. I still usually prefer a non-polarized electrolytic cap when there’s no polarizing voltage present and you need large values—essentially “antiseries” (two electrolytics in series with the + terminals or – terminals connected to each other). Peace—PJS

http://midisolutions.com/prodrel.htm http://www.rspe.com/Metering-Studio-Displays/PunchLight.html http://www.deeringamps.com

Recording - February 2010

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