Yes, there were subtle audio differences that I still preferred with the original DSD, yet this $900 PCM multitrack recorder, that runs on batteries, captured much of the essence, detail and imaging of the master recording.
The DR-680‘s operational software, in conjunction with the push-button and rotary controls, is very intuitive; you can easily set up the project, make recordings, mix and transfer the finished audio project to PC — without ever consulting the manual.
Input options include six balanced mic/line jacks (four are XLR/TRS 1/4-inch combo jacks; two are TRS 1/4-inch only), stereo SPDIF digital connection, and a live monitor mix can be selected to feed channels 7 & 8.
by Bascom King
The TASCAM DR-680 is a member of the multi-channel compact class of digital recorders. This one can record up to a bit density and sample rate of 24/192 in stereo, or up to six channels at 24/96. Although the DR-680 unit has digital I/O and analog I/O, most end-users are going to download the finished recording to a computer, so we decided that the A/D measurements were the more important measurement parameters, though we did make A/D-D/A calculations as well.
Frequency response at 0 dBFS at a sample rate of 192 kHz is shown plotted in Fig. 1 for analog inputs 1 & 2 and for the digital output for both the line input and the mic inputs at the high gain setting. Surprisingly, the flatter response is for the mic input here. The channel tracking is so good here that one can’t see any difference between the channels at this graph vertical resolution.
The analog output response for the same input conditions is down a bit more at 90 kHz due to the D/A filters and is at about –10 dB. The low frequency response was down about 1 dB at 10 Hz. When the response was measured at lower sample rates of 96 & 44.1 kHz, the response shape was much flatter up to the filter cutoff – a result I usually see in digital audio device measurements.
An interesting and revealing measurement is in the distortion vs. level of a 1 kHz tone in the digital output with input signals applied to the line inputs. Fig. 2 shows this plotted in a 20 kHz measurement bandwidth and at a sample rate of 192 kHz. This indicates a S/N ratio of 100 dB. This is quite good for an integrated all-in-one, rather inexpensive recorder/player (though the best converters can exceed -115 dB). This same test on the analog outputs showed some lumps upwards in the curve caused by some D/A misbehavior at sample rates of 192 & 96 kHz from –5 to –30 dBFS. In these deviations, the amount of distortion was still better than –83 dBFS. At sample rates of 48 & 44.1K, the curves were smooth like in Fig. 2.
S/N ratios at the digital outputs for sample rates of 192 kHz, 96 kHz, & 44.1 kHz and in a measurement bandwidth of 20 kHz were 100.0 dBFS, 95.5 dBFS and 95.5 dBFS respectively. Dynamic range measurements for the same sample rates were 102.8 dBFS, 98.1 dBFS, & 98.0 dBFS. Finally, for the digital output, the quantization noise measurements came out to be –96.0, 93.6, & - 93.6 dB. Again, these are very good measurement results.
In general, the same measurements at the analog outputs were just a few dB worse. When going through the mic inputs at the high gain setting, measurements were yet a few more dB worse for both analog and digital outputs, but still well into -90 dB+ range. That is still pretty quiet.
Adjacent channel separation was quite similar in both directions for both digital and analog outputs. What was a bit odd was that the nature of the separation was typical rising with frequency for the mic inputs but had a characteristic of rising at low frequencies for the line inputs.
All in all, the DR-680 performs pretty well on the bench — especially for its small size, features and what it costs.
Bascom King is owner and chief technician for BHK Labs in Santa Barbara, Ca.