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dbx Subharmonic Synthesizer
(1970s-today)
© 2011 KenRockwell.com. All rights reserved.

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October 2011   All Reviews    Audio Reviews

 

 

Definate lminted range of synthesis: source frequancy 110 Hz on top end, bottom end 30-40 hz depending on synthsizer's mood.

Too thick, maybe best to lower preamp bass level with all the extras added in; otherwise, knocks yout head around too much.

Same relative synth levels regardless of input levels over about a 30 dB attenuation range.

Synth not that musical; it does't always get warmed up.

Full-range output becomes high-pass when pressing button; low-pass output unchanged.

Use as pure crossover if synth bypassed

Bypass is active, not a wire-through.

Boom box: peaked response

Synthesizes on solo male voices, not good.

 

Model 500 1978

Model 100 1979

Model 120X 1995

Model 120A 2011

 

sounds great on old rock, Quadrophenia.

All this below is filler.

 

 

 

 

adorama

 
B&H Photo - Video - Pro Audio

Ritz Camera

I use Adorama, Amazon, Ritz, B&H, Calumet, J&R and ScanCafe. I can't vouch for ads below.

Introduction

Apple computers have been the standard in professional audio recording, mixing and mastering ever since computers were first used for music production.

Apple won a 2002 Grammy Award precisely for their huge contribution to the music industry. Even I was surprised, and I was at the Grammy Awards that year!

Any recorded music you're enjoying today has probably been through Pro Tools or Logic Pro or whatever, on a Mac, before it made it to vinyl , CD, SACD or whatever.

Audio professionals rarely use the Mac Pro's own analog outputs, but this is what we're going to test today. Pros usually take the data off to wherever it needs to go next in the production chain, use the DACs from elsewhere in their system, or at least use spiffy DACs from the Mac's own standard-for-years TOSLINK outputs.

In any case, let's see how the Mac's own outputs, playing-out from iTunes, measures up.

 

Line Output (rear 3.5mm jack)

Output Voltage

Maximum gain, 0 dB FS at 1 kHz:

 

Unloaded (Tektronix TX3)

Left Channel

2.0998 V RMS.

6.44 dBV.

8.66 dBu.

 

Right Channel

2.0628 V RMS.

6.29 dBV.

8.51 dBu.

 

75Ω load

Left Channel

1.9448 V RMS.

5.78 dBV.

9.99 dBu.

 

Right Channel

1.9780 V RMS.

5.92 dBV.

8.14 dBu.

 

Left/Right Channel Balance

0.15 dB at full gain, unloaded.

0.15 dB at full gain, 75Ω load.

 

Output Impedance

Loaded with a Tektronix 75Ω ±0.025% termination versus the unloaded input of the Tektronix TX3, the output voltage drops to 94.24%.

Algebra tells us that the source impedance is therefore 4.6 Ω at 1 kHz.

 

Frequency Response

Signal: -20 dB FS sine wave, 44.1 k samples per second, 1,411 k bits per second AIFF file on iPod Touch.

iPod at maximum gain.

 

100 kΩ analyzer load

5 Hz: -1.8 dB

8 Hz: -0.9 dB

10 Hz: -0.9 dB

12.5 Hz: -0.3 dB

16 Hz: -0.1 dB

20 Hz: -0.1 dB

50 Hz: 0.0 dB

100 Hz: 0.0 dB

200 Hz: 0.0 dB

500 Hz: 0.0 dB

1 kHz: 0.0 dB

2 kHz: 0.0 dB

5 kHz: 0.0 dB

7 kHz: 0.2 dB

10 kHz: -0.3 dB

12.5 kHz: -0.5 dB

15 kHz: -0.9 dB

17.5 kHz: -1.0 dB

20 kHz: -2.5 dB

22 kHz: -7.5 dB

 

75Ω load (measures the same)

5 Hz: -1.8 dB

8 Hz: -0.9 dB

10 Hz: -0.9 dB

12.5 Hz: -0.3 dB

16 Hz: -0.1 dB

20 Hz: -0.1 dB

50 Hz: 0.0 dB

100 Hz: 0.0 dB

200 Hz: 0.0 dB

500 Hz: 0.0 dB

1 kHz: 0.0 dB

2 kHz: 0.0 dB

5 kHz: 0.0 dB

7 kHz: 0.2 dB

10 kHz: -0.3 dB

12.5 kHz: -0.5 dB

15 kHz: -0.9 dB

17.5 kHz: -1.0 dB

20 kHz: -2.5 dB

22 kHz: -7.5 dB

 

Signal-to-Noise Ratio

Maximum gain, 0 dB FS versus paused or muted output (same readings):

 

100k Ω load

91 dB, 400 Hz - 30 kHz unweighted.

89 dB, 5 Hz - 30 kHz, unweighted.

86.5 dB, 5 Hz - 80 kHz, unweighted.

76 dB, 5 Hz - 700 kHz, unweighted.

 

75 Ω load

89 dB, 400 Hz - 30 kHz unweighted.

87 dB, 5 Hz - 30 kHz, unweighted.

85 dB, 5 Hz - 80 kHz, unweighted.

76 dB, 5 Hz - 700 kHz, unweighted.

 

THD + Noise

Source: 128 kbps AAC file created in iTunes from a 44.1 kHz Rohde & Schwarz test CD, 1 kHz, 0 dB FS played on iPod Touch.

Mac Pro set to maximum gain.

 

100 kΩ analyzer load

0.012% THD + N, 30 kHz measurement bandwidth.

0.014%, 80 kHz measurement bandwidth.

0.03%, 700 kHz measurement bandwidth.

 

75Ω load:

0.19% THD + N, 30 kHz measurement bandwidth.

0.21%, 80 kHz measurement bandwidth.

0.22%, 700 kHz measurement bandwidth.

 

THe distortion from the Line Output isn't anywhere near as happy at 75Ω as it is with 100k Ω, but hey, it's a line output.

Let's now look at the dedicated front-panel headphone jack.

 


 

Headphone Output (front 3.5mm jack)

Output Voltage (front 3.5mm headphone jack)

Maximum gain, 0 dB FS at 1 kHz:

 

Unloaded (Tektronix TX3)

Left Channel

1.3303 V RMS.

2.48 dBV.

4.70 dBu.

 

Right Channel

1.3374 V RMS.

2.52 dBV.

4.74 dBu.

 

75Ω load

Left Channel

1.2432 V RMS.

1.89 dBV.

4.11 dBu.

 

Right Channel

1.2476 V RMS.

1.92 dBV.

4.14 dBu.

 

Left/Right Channel Balance (front 3.5mm headphone jack)

0.04 dB at full gain, unloaded.

0.03 dB at full gain, 75Ω load.

 

Output Impedance (front 3.5mm headphone jack)

Loaded with a Tektronix 75Ω ±0.025% termination versus the unloaded input of the Tektronix TX3, the output voltage drops to 93.37%.

Algebra tells us that the source impedance is therefore 5.3 Ω at 1 kHz.

 

Frequency Response (front 3.5mm headphone jack)

Signal: -20 dB FS sine wave, 44.1 k samples per second, 1,411 k bits per second AIFF file on iPod Touch.

iPod at maximum gain.

 

100 kΩ analyzer load (measures the same as line outputs)

5 Hz: -1.8 dB

8 Hz: -0.9 dB

10 Hz: -0.9 dB

12.5 Hz: -0.3 dB

16 Hz: -0.1 dB

20 Hz: -0.1 dB

50 Hz: 0.0 dB

100 Hz: 0.0 dB

200 Hz: 0.0 dB

500 Hz: 0.0 dB

1 kHz: 0.0 dB

2 kHz: 0.0 dB

5 kHz: 0.0 dB

7 kHz: 0.2 dB

10 kHz: -0.3 dB

12.5 kHz: -0.5 dB

15 kHz: -0.9 dB

17.5 kHz: -1.0 dB

20 kHz: -2.5 dB

22 kHz: -7.5 dB

 

75Ω load (measures the same as at 100kΩ )

5 Hz: -1.8 dB

8 Hz: -0.9 dB

10 Hz: -0.9 dB

12.5 Hz: -0.3 dB

16 Hz: -0.1 dB

20 Hz: -0.1 dB

50 Hz: 0.0 dB

100 Hz: 0.0 dB

200 Hz: 0.0 dB

500 Hz: 0.0 dB

1 kHz: 0.0 dB

2 kHz: 0.0 dB

5 kHz: 0.0 dB

7 kHz: 0.2 dB

10 kHz: -0.3 dB

12.5 kHz: -0.5 dB

15 kHz: -0.9 dB

17.5 kHz: -1.0 dB

20 kHz: -2.5 dB

22 kHz: -7.5 dB

 

Signal-to-Noise Ratio (front 3.5mm headphone jack)

Maximum gain, 0 dB FS versus paused or muted output (same readings):

 

100k Ω load

83 dB, 400 Hz - 30 kHz unweighted.

81 dB, 5 Hz - 30 kHz, unweighted.

79 dB, 5 Hz - 80 kHz, unweighted.

72.5 dB, 5 Hz - 700 kHz, unweighted.

 

75 Ω load

82 dB, 400 Hz - 30 kHz unweighted.

80 dB, 5 Hz - 30 kHz, unweighted.

78 dB, 5 Hz - 80 kHz, unweighted.

74 dB, 5 Hz - 700 kHz, unweighted.

 

THD + Noise (front 3.5mm headphone jack)

Source: 128 kbps AAC file created in iTunes from a 44.1 kHz Rohde & Schwarz test CD, 1 kHz, 0 dB FS played on iPod Touch.

Mac Pro set to maximum gain.

 

100 kΩ analyzer load

0.015% THD + N, 30 kHz measurement bandwidth.

0.018%, 80 kHz measurement bandwidth.

0.037%, 700 kHz measurement bandwidth.

 

75Ω load:

0.25% THD + N, 30 kHz measurement bandwidth.

0.275%, 80 kHz measurement bandwidth.

0.28%, 700 kHz measurement bandwidth.

 

Oh well, the dedicated front-panel headphone jack isn't as good as the headphone output of an iPod touch.

 

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Thanks for reading!

 

 

Mr. & Mrs. Ken Rockwell, Ryan and Katie.

 

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