Antique Instrumentation Relay Rack
This series of 3 photos is from an audio experiment. Direct-Stream Digital, DSD, is the digital audio format that is the basis for the SACD. The Tascam DA-3000 is a new recorder which uses this format. An artifact of this recording method is ultrasonic distortion. These images provide an idea of what this distortion looks like.
A 1 kHz sine wave was generated by the internal oscillator in an Otari 5050 at a level of 0 dBVU. This signal was applied to a Hewlett-Packard 120B oscilloscope setup for a vertical displacement of 10 mV/cm and horizontal sweep of 250 u-sec/cm. The crest of the sine wave is shown. Note how clean this sine wave appears. The distortion as measured on a Hewlett-Packard 130B distortion analyzer was about 0.3 %. This signal was then digitized using DSD 2X on the Tascam DA-3000 and converted back to analog on the Tascam DA-3000. Note how there is now high frequency ultrasonic distortion of about 10 mv peak-to-peak being carried by the 1 kHz sine wave. A distortion measurement gave a value of about 2 %. A Krohn-Hite 3202R low pass filter was swept down to a cutoff of 70 kHz to bring the sine wave reasonably back to the shape of the straight analog signal. This cutoff is consistent with filters used for this purpose.
These measurements were performed on antique instrumentation I have restored as shown in the photo of the relay rack. The 120B and 130B are both vacuum tube instruments. I can not say these measurements of of high quantitative quality. However, it does illustrate the presence of the expected ultrasonic distortion present in this recording method. I will be checking to see if this distortion finds its way through the power amplifier to the speakers and if so, will consider using an audio shelving filter during playback.
Photographed using a Sony A7S with a Micro Nikkor 105 f/2.8 lens.
Antique Instrumentation Relay Rack
This series of 3 photos is from an audio experiment. Direct-Stream Digital, DSD, is the digital audio format that is the basis for the SACD. The Tascam DA-3000 is a new recorder which uses this format. An artifact of this recording method is ultrasonic distortion. These images provide an idea of what this distortion looks like.
A 1 kHz sine wave was generated by the internal oscillator in an Otari 5050 at a level of 0 dBVU. This signal was applied to a Hewlett-Packard 120B oscilloscope setup for a vertical displacement of 10 mV/cm and horizontal sweep of 250 u-sec/cm. The crest of the sine wave is shown. Note how clean this sine wave appears. The distortion as measured on a Hewlett-Packard 130B distortion analyzer was about 0.3 %. This signal was then digitized using DSD 2X on the Tascam DA-3000 and converted back to analog on the Tascam DA-3000. Note how there is now high frequency ultrasonic distortion of about 10 mv peak-to-peak being carried by the 1 kHz sine wave. A distortion measurement gave a value of about 2 %. A Krohn-Hite 3202R low pass filter was swept down to a cutoff of 70 kHz to bring the sine wave reasonably back to the shape of the straight analog signal. This cutoff is consistent with filters used for this purpose.
These measurements were performed on antique instrumentation I have restored as shown in the photo of the relay rack. The 120B and 130B are both vacuum tube instruments. I can not say these measurements of of high quantitative quality. However, it does illustrate the presence of the expected ultrasonic distortion present in this recording method. I will be checking to see if this distortion finds its way through the power amplifier to the speakers and if so, will consider using an audio shelving filter during playback.
Photographed using a Sony A7S with a Micro Nikkor 105 f/2.8 lens.