Re: An Improved Dual Class-A Output: The "DCAO2"
Posted: Mon Oct 10, 2016 8:11 pm
I have a construction thread for the Dual Class-A II DCAO2 and have been busy writing the instructions, ordering a test bill-of-materials and construction of a second unit.
See viewtopic.php?f=7&t=825
With a second unit built and tested I decided to do some additional measuring.
One of the questions I have is how much power is available for 'phones more difficult to drive than my 106 dB/mW Sony MDR-7506s.
There are combinations of impedance and low sensitivity that are pretty demanding.
Beyer and HiFi Man come to mind.
Some, such as the Beyer DT-880 Pro (available in 32, 250 and 600Ω) require lots of drive voltage because they are 600Ω, others such as the HiFi Man HE6 are in the 30-50Ω range with low 83.5 dB/mW sensitivity requiring almost 5W to produce 120 dB SPL.
Today I ran some maximum power levels for various load impedances.
The DCAO2 can be run in mono as fully-balanced output in a bridge-tied-load "BTL" configuration as well as stereo with single-ended "SE" outputs.
The following maximum power outputs were measured with +/-15V supplies just below clipping.
The DCAO2 is operating closed loop.
15Ω SE 7.5 Vrms 3.75W
15Ω BTL 12.1 Vrms 9.76W
30Ω SE 8.1 Vrms 2.1W
30Ω BTL 14.8 Vrms 7.3W
60Ω SE 8.7 Vrms 1.26W
60Ω BTL 16.1 Vrms 4.32W
120Ω SE 9 Vrms 675 mW
120Ω BTL 17.3 Vrms 2.49W
>120Ω the maximum output is 9 Vrms SE, BTL >17.3 <18 Vrms.
Measuring distortion presents additional challenges because at all but the higher power levels the DCAO2's distortion is less than the generator and analyzer.
In my next post I intend to show distortion measurements made using null testing where one channel of the DCAO2 is used to measure the other.
With null testing I'm able to see distortion products in the -130 (0.3 ppm) to -120 dB (1 ppm) range.
See viewtopic.php?f=7&t=825
With a second unit built and tested I decided to do some additional measuring.
One of the questions I have is how much power is available for 'phones more difficult to drive than my 106 dB/mW Sony MDR-7506s.
There are combinations of impedance and low sensitivity that are pretty demanding.
Beyer and HiFi Man come to mind.
Some, such as the Beyer DT-880 Pro (available in 32, 250 and 600Ω) require lots of drive voltage because they are 600Ω, others such as the HiFi Man HE6 are in the 30-50Ω range with low 83.5 dB/mW sensitivity requiring almost 5W to produce 120 dB SPL.
Today I ran some maximum power levels for various load impedances.
The DCAO2 can be run in mono as fully-balanced output in a bridge-tied-load "BTL" configuration as well as stereo with single-ended "SE" outputs.
The following maximum power outputs were measured with +/-15V supplies just below clipping.
The DCAO2 is operating closed loop.
15Ω SE 7.5 Vrms 3.75W
15Ω BTL 12.1 Vrms 9.76W
30Ω SE 8.1 Vrms 2.1W
30Ω BTL 14.8 Vrms 7.3W
60Ω SE 8.7 Vrms 1.26W
60Ω BTL 16.1 Vrms 4.32W
120Ω SE 9 Vrms 675 mW
120Ω BTL 17.3 Vrms 2.49W
>120Ω the maximum output is 9 Vrms SE, BTL >17.3 <18 Vrms.
Measuring distortion presents additional challenges because at all but the higher power levels the DCAO2's distortion is less than the generator and analyzer.
In my next post I intend to show distortion measurements made using null testing where one channel of the DCAO2 is used to measure the other.
With null testing I'm able to see distortion products in the -130 (0.3 ppm) to -120 dB (1 ppm) range.