Archive for August, 2010

A/D and D/A Conversions

by on Aug.22, 2010, under Music

A point often overlooked by home recording engineers is that for every digital unit in an analog instrument chain an A/D and D/A conversion is being performed. Doing this once or twice with high quality converters is probably not very noticeable, but chaining several digital pedals together is probably not wise. Each pedal will do a full round of conversion and introduce their own ‘flavor’ of signal degradation.

Most home recorders are already converting twice by necessity, getting the sound in and out of the computer. Intuitively, it makes sense to leverage analog processing whenever they’re appropriate to avoid these additional conversions prior to the sound interface. The other option is to record dry and use digital processing ‘in the box’ as there are no additional conversions in this case. There are no shortage of high quality software DSPs.

Most folks, including myself, likely have more pressing problems to address in their home studio. However, A/D conversion is certainly a factor to consider before mindlessly stacking another gadget on the signal chain. Think about where in the chain the gadget is being placed. Could the number of conversions be reduced by rearranging the chain? Could this gadget be placed in a digital loop with the sound interface, thus avoiding another conversion entirely? Most modern rack-mount DSPs do indeed have this capability.

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Guitar Cabinet Simulation

by on Aug.18, 2010, under Music

The amount of ‘color’ imparted to a distorted guitar sound by the speaker cabinet is often understated. Guitar speakers are not high fidelity. Rather they’re designed to roll off high frequencies, typically those over 8khz or so, and usually have poor response to frequencies under 120hz. The high frequency attenuation is particularly important for high gain distorted styles. If absent, listeners will suffer fizz and sizzle.

However cabinets present problems. They’re expensive, heavy, and need to be driven loud to impart the impulse characteristics associated with modern metal and rock. This doesn’t gel with living in a 900 sqft house in a major metropolitan area. Many home recorders and musicians need an alternative.

One alternative is to simply record via the line out on a pre-amp…this sucks big time. You can compensate a bit with high and low cuts on an EQ but it will sound very thin and fizzy. Leaving the power amp in the chain and brining the signal back down to line level through a load box and speaker simulator is better. Many of these units feature adjustable high cut and voicing controls. Additionally, you retain the color of the power amp section. But the results are usually still disappointing. There’s something missing, speaker impulse response.

The sound heard on most rock and metal recordings of guitar is the result of miking a speaker cabinet. Without a cabinet in the chain, it’s virtually impossible to reproduce certain dynamics captured by the microphone. Enter speaker impulse samples. Thanks to Prof. Fourier, it is possible to tease apart the speaker impulse data for all possible tones given any guitar speaker. These impulse ‘deconvolutions’ may then be convolved with any digital audio track to replace the otherwise missing impulse dynamics. Several ‘convolution reverb’ plug-ins are available for the task.

With well captured data from a good cabinet and microphone, the results are amazing compared against the unprocessed track. Many free guitar speaker impulse deconvolutions can be found via Google. At least one free convolution engine exists for Linux platforms, jconv, and can be integrated with Ardour via the Jack protocol. I highly recommend anyone recording guitars direct-to-console check these tools out.

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Song Demo 1

by on Aug.09, 2010, under Music

Here’s a song created using the Ubuntu Studio tool chain discussed in previous posts. The drums are programmed using Hydrogen but the guitar and bass are real instruments. Both were recorded ‘direct to console’ with the bass going through a Sansamp NYC. The guitar chain is Engl 530 -> VHT 2/90/2 -> Palmer ADIG-LB (load box).


This was after spending about a month’s worth of solid weekends learning the tools and reading some advice from professional metal producers/engineers. In the field of sound engineering, I’m still very green.

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Gear Research Syndrome

by on Aug.01, 2010, under Music

I’ve been reading a series of informative and entertaining articles on home recording by Brandon Drury. The articles say less about what ‘to do’ and more about what ‘not to do’. This is not a criticism, rather it’s very appropriate for this craft. One particular pitfall illustrated, under which I’ve self diagnosed, is Gear Research Syndrome. Countless hours studying details of amplifier design, tube characteristics and other issues that have much less impact on an overall mix than many non-gear related issues.

Symptoms of the disorder include attention on manufacturing differences between Russian KT88 tubes and various knock-offs at opposed to important factors such as the instrument, skill, and the physical recording and monitoring environment.

Cognitive behavioral therapy is indicated in any instance of this disorder. The individual must be trained to recognize the excessive research behavior and reduce the amount of gear research. The additional attention redirected to more important issues will result in sound improvement and reinforce the behavioral change.

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