CT102 vs batteries

DACT

Danish Audio ConnecT. Switch contact cleaning. In rare cases it may be necessary to clean the contacts on DACT switches. If cleaning is required it will show as noise in the speakers when the switch is operated. Tuner 600 from Kontakt Chemie is the only cleaning agent recommend for this use by DACT.

Based on listening test and on feedback received from customers we have had strong indications that our CT102 Audio Power Supply module improves the sound from audio electronics circuits compared to other voltage sources. Even when compared to batteries, which are normally considered the ultimate power source in audio. Therefore we set out to show the differences in objective terms through electrical measurements.
At DACT we have the theory that some of the most important specifications of a good audio power supply mainly include

Low output impedance over and beyond the entire audio frequency band
Low noise
Ability to deliver large current peaks very fast
Equal ability to deliver and sink current

CT102 can easily be said to meet these requirements but to which extend; and so can batteries probably?




			Fig. 1. DACT CT102 Audio Power Supply

	With respect to output impedance comparison between CT102 and batteries please see the details below. As far as noise is concerned there is no question that nothing beats batteries. We have not been able to measure any self-noise from batteries at all, but CT102 comes very close at a so far unseen measured noise figure of -126dB (IHF A). Without having measured for comparison we know that CT102 can deliver peak currents greater than most batteries (CT102 >10A) due to the large low-ESR capacitors connected at the CT102 outputs. And just like batteries, CT102 sinks current as well as it supplies current.

Let’s go on with the measurements of output impedance, which we believe is the single most important specification for audio power supplies. Below is a graph showing our measured output impedance comparing our CT102 (set at 15V out) with what we believe are some of the best rechargeable and dry-cell batteries:

Sonnenschein Dryfit A512/2 S, 12V 2Ah, rechargeable battery, fully charged
Duracell, Ultra M3, LR 20 (D) Alkaline (8 pcs connected in series for obtaining 12V)

Test conditions:
Load: 300ohm
Measuring current: 20mA
Connected through same 2 x 60cm (24”) wires (results corrected for the impedance of the wires)




	Fig. 2. Sonnenschein rechargeable batteries




		Fig. 3. Duracell Alkaline batteries


	Fig. 4. Output impedance comparison, CT102 versus rechargeable and dry-cell batteries.

Conclusion
Please observe that the vertical scale in fig. 4 is logarithmic. This means that the difference in output impedance between the measuring objects is much larger than it appears at first glance.
At 10Hz the measured output impedance of CT102 is 0.4 milliohm. At the same frequency, the rechargeable batteries’ output impedance is 183 milliohm (450 times higher than the CT102 output impedance) while the dry-cell batteries’ output impedance is 2,013 milliohm (5,000 times higher than the CT102 output impedance).
At 20kHz the measured output impedance of CT102 is 4.6 milliohm. At the same frequency, the rechargeable batteries’ output impedance is 70 milliohm (15 times higher than the CT102 output impedance) while the dry-cell batteries’ output impedance is 486 milliohm (100 times higher than the CT102 output impedance).
Finally, at 100kHz the measured output impedance of CT102 is 14 milliohm. At the same frequency, the rechargeable batteries’ output impedance is 80 milliohm (more than 5 times higher than the CT102 output impedance) while the dry-cell batteries’ output impedance is 437 milliohm (30 times higher than the CT102 output impedance).

We believe that the findings here about the output impedances to a large extend explain why CT102 often is considered better than any other power source for powering audio electronic circuits.
Certainly, we recommend the CT102 audio power supply to be used for our CT100 phone stage module and our CT101 line stage module for the ultimate performance. We also recommend using CT102 for similar audio circuits requiring +/-15VDC or +/-20VDC power supply with less than 200mA current requirement.