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DC-Live Traces Out Analog Noise:
A Software Review by Read G. Burgan
Published In RADIO WORLD January 3, 2001:

Read G. Burgan

Imagine that you reach into your vinyl LP library and take out one of your old favorites and place it on the turntable. Then you gently drop the needle on the first track and . . . what you hear is as clear and crisp as any CD -- no pops, no clicks, no surface noise. Just music. Glorious music.

Imagine no more. Tracer Technology's new Diamond Cut-Live software goes where no other software in its price class has ever dared to go before. What do I mean?

In the past few years, several companies have released good digital noise reduction software that have cleaned away the noise that is an inherent part of vinyl and other analog recordings. But with the exception of hardware/software priced in the range of a Mercedes Benz, all of it has required that the sound source first be recorded to hard drive and then submitted to a series of digital noise reduction processes that can take several hours.

DC-Live has changed all that -- forever. With DC-Live, you plop a record on your turntable (or a reel on your tape recorder) and listen immediately to the digitally restored sound.

For a radio station, this means that those stacks of records lying fallow in a back closet can now be resurrected and played directly on the air with a sound rivaling present day CD’s. For collector’s like myself with thousands of ET’s, LP’s and reel-to-reel recordings, it is no longer necessary to spend several hours to restore a single recording that may be listened to only once-in-a-blue-moon. Anytime I want to hear an old recording, I can drop the needle on the record, sit back, and enjoy yesterday’s sound with today’s fidelity.

With Diamond Cut Live (DC-Live), your IBM PC computer becomes the center of your audio chain. The turntable preamp (or reel-to-reel or cassette deck preamp output) is connected to the input of your computer sound card, and the output of the computer sound card is connected to your stereo monitoring equipment.

How does it work? Tracer Technologies has been a leader in the field of digital restoration software with its series of products based on the Diamond Cut Audio Restoration (DC-art) software designed for the IBM PC and Windows operating systems. In the past several years, Tracer has continually improved and expanded this inexpensive restoration software until it’s features rival those found in software costing many times more.

Using the DC-art software as its base, Tracer has created a “Live Multi Filter” that allows one to chain together nearly all of its filters and effects and run them in real time. When you open the Live Multi Filter, you find a list of all applicable filters and a screen to which you can drag the ones you want to use.

The filters are applied in the order that they are dragged to the multi filter screen. Multiple copies of the same filter may be dragged to the screen. I usually have two of the impulse filters in the chain to remove both large and small clicks, plus one continuous noise filter and one graphic equalizer filter.

Once all of the filters have been selected, you click on the “Live Preview” button, drop the needle on your turntable, and the digitally restored sound issues from your speakers.

A filter’s parameters can be adjusted by double clicking on the onscreen icon of the filter. This brings up the menu for that filter. The adjustments are monitored in real time so that each filter’s effect can be fine-tuned.

How well does all of this work? Very well. One quickly gets spoiled listening to old analog recordings restored in real time. LP’s that are in moderately good condition sound bright and clean. The annoying surface noise that characterizes vinyl recordings is gone -- as are all but the most egregious pops and clicks.

There are some latency considerations, i.e.: a delay between the incoming and outgoing sound. This is dependent on the processing power of your computer, the sampling and bit rate selected, the number and kind of filters selected, and whether or not you’re processing in mono or stereo. Using a Pentium-II 650 MHz processor to process a 44.1 kHz stereo file, I experienced a latency of about one-second.

In the case of badly deteriorated sound sources, it may better to process a sound source the conventional way, first recording the sound to hard drive and then applying the filters one-at-a-time to the WAV file. By their very nature, some of the filters like the impulse filter can be applied more aggressively to an existing WAV file than they can to live audio.

In past reviews I have described the various filters and tools of DC-32, so I won’t go into detail here except to list the some of the filters more pertinent to digital audio restoration and to highlight some upgrades and additions. Central to the core of audio restoration are the impulse, continuous noise, harmonic rejection, dynamic noise, low pass, band pass, notch, graphic equalizer and paragraphic equalizer filters. Among the effects tools are the reverb, virtual valve amplifier, the dynamics processor and the channel blender.

The impulse filter has added a new recording “type”: HQ Mode. HQ stands for Hind Quaternion. According to Tracer, this new algorithm provides greater control over the variables affecting the detection of noise impulses and the rejection of transient music passages. It also requires more processing power when using the Live Preview mode.

Tracer has improved the continuous noise filter by adding a choice of resolutions for the FFT size. FFT stands for Fast Fourier Transform that is used to perform the filtering. By providing a choice of FFT size, DC-Live breaks the audio spectrum up into more bands thus increasing the frequency resolution of the filter and giving the filter greater ability to discern between frequency and noise.

In the effects menu, the dynamics processor has added an automatic level control (ALC or AGC) to its existing Expander/Gate and DeEsser functions. The ALC allows widely disparate sounds like that of an interviewer and his guest on the phone or of a baseball commentator and the crowd noise to be automatically set to the same level by bringing all sound below a set threshold up and all sounds above the threshold down.

To test the ALC, I used a recording of an oral history interview that I had made on the phone recently. The ALC balanced my overly loud level with the very low level of the interviewee on the other end of the phone. A nice tool.

Tracer has added an “Enhancer” check box to the Dynamic Noise filter. By checking this box, the DNF will expand all signals above the set threshold and above the variable high pass corner frequency. Since the DNF is attenuating hiss and other noise components below those points, it allows an increase in the brightness of the program material without emphasizing the hiss as well. I tested it on an old Armed Forces ET, and it provided a nice increase in the high frequency content with little or no increase in noise.

Two additional tube types have been added to the Virtual Valve Amplifier: 2A3 Push-Pull and 2A3 Single-Ended. The former at the suggestion of guitarist Les Paul who used the 2A3 triode in the amplifiers at his home studios where many of his recordings were mastered.

The main menu also sports a new set of colorful VU meters that are always present, much more responsive than the older ones and very easy to see.

DC-Live has also added a Channel Blender tool. No, you can’t use it to make a Daiquiri. The channel blender tool has been ingeniously designed to provide several very useful functions including the elimination of turntable rumble while improving bass response without deteriorating mid and high frequency stereo separation, reducing FM stereo multi-path distortion, taming the Ping-Pong stereo effect of early stereo recordings and extracting ambiance information from stereo recordings.

It does this through variable right and left channel sliders, plus an option to blend to mono above or below a certain set frequency, and the ability to invert one or both of the channels. While fairly simple and straightforward to use, it provides an excellent tool to deal with some common and annoying problems.

At the bottom of the effects menu is an interesting tool called: Punch and Crunch. No, it’s not a digital taco/pizza. It’s a cleverly designed expander and compressor. Punch and crunch breaks the audio spectrum into four bands, and each of them is independently expanded or compressed dependent upon where its individual threshold is set.

It was primarily designed to improve the intelligibility of forensic recordings, but can be used for radio station related applications including uncompressing an overly compressed signal, improving the signal to noise ratio of noisy recordings or compressing the output of your sound to maximize its signal on the dial. Punch and crunch is one more example of the kind of unique application that can be accomplished readily in the digital realm.

In order to use DC-Live to the fullest in its Live Preview mode, you need a well-muscled computer and a sound card capable of duplex operation. Initially I was unable to use the Live Preview mode even though the sound card I used was full duplex capable. I was unable to stop the input and output sound from streaming simultaneously. Eventually Tracer provided a sound card that solved the problem.

Early on I used a Pentium-II 350 MHz processor, and it was not able to handle all the filters I wanted to use in stereo at 44.1 kHz sampling rate. The sound output would stutter after just a few minutes of processing.

When I upgraded to a Pentium-II 650 MHz processor, these problems disappeared. Kyle K. Betts, VP Sales at Tracer, suggests that a Pentium-II 500 is the minimum for using the Live Mode and that Windows 98 SE is a must (I did my testing using Windows 95, and although it performed remarkably well, did experience a few crashes that were almost certainly operating system related). He also emphasizes that a good sound card is a must and recommends the LynxOne or the WaveTerminal 2496 from Egosys as two good examples.

As far as I know, DC-Live is the only digital audio restoration software capable of running in real time in this price range. With a plethora of well-designed restoration tools, it should prove a welcome addition to anyone who needs to digitally restore analog sound sources in real-time. Since Tracer has a history of updating and improving the DC-art software series, Diamond Cut Live should be a good long-term investment.

DC-Live can be purchased directly from Tracer Technologies for $995. For that money, one gets just about every conceivable digital audio restoration tool imaginable plus the unprecedented ability to use them in real time.

-- THE END --

Tracer Technologies, Inc., 1201 Pennsylvania Avenue Unit 101, York, PA 17404 1-888-887-2237 www.tracertek.com sales@tracertek.com.

Read Burgan is a free lance writer and a former public radio station manager who can be reached at (906) 296-0652 or through e-mail at rgb@bresnanlink.net.


Digitally restores analog audio in real time
Has virtually any restoration filter or effect you could ask for
Easy to use
Great user’s manual with loads of digital restoration information


Requires at least a P-II 500 processor, Windows 98 SE and a full duplex sound card