Possibly Dumb Question re:Battery as a power supply

@terry9-

ELECTRICAL CHARACTERISTICS (Vin = 19 V, IO = 500 mA, TJ = Tlow to 125°C (Note 17), unless otherwise noted)

That is the standard disclaimer at the top of the chart of parameters. It is the operating point used in all of the measurements below it. One of those parameters is DROP OUT VOLTAGE which was listed as 2.0VDC (assuming 500mA load) on the datasheet I found on-line. The disclaimer does not mean the device has to be operated at those parameters, only that the published specifications were measured at that operating point.

Agree with your point about noise not being an issue. I don’t know that I’ve ever seen a measurement for this on a battery, but the internal resistance of a fully charged battery is extremely low so the equivalent noise resistance should be microscopic.

I would think a Sealed Lead Acid battery would be better (and cheaper) than a NiCad. SLAs tend to last longer and don’t suffer from memory effect if they are not fully cycled between charge and discharge as NiCads do. YMMV.

Phoenix, agree with what you say, but let me add that 19VDC is the voltage at which the part is known to meet spec. With obvious consequences - which, to an engineer such as yourself, pose no issues.

Battery noise was measured by someone in Germany some years back. I think they were looking at powering phono stages. He found that all technologies made a fair bit of noise, except NiCd, which measured at the noise floor of his HP instrumentation.

Anyway, I'm in the process of designing a new phono power supply based on NiCd's for listening and a linear PS for warming, and the unexpected issue is charging. Seems that no-one does it right - i.e. warning at 1.1VDC per cell to avoid memory effect and separate current source for each cell.

Expect to start building in a couple of weeks, will let you know if it makes a perceptible improvement over alkaline with LC filter.

Previous experience with improving power has shown a worthwhile improvement in sound. This manifests as smoother with no shrill overtones or sibilance (dare I say 'more musical') as well as quieter. 

1. Isolation transformers
2. Brute force DC rails for amps: 200kg inductors and a Farad of capacitance
3. Alkaline battery with LC filter for phono/pre
4. Quadrature AC adjusted to AC motor

My experience. YMMV

@phoenixengr, glad to see you join in this discussion, your expertise is greatly appreciated!
BTW, I’ve been using the Teres battery power supply on my turntable for more than 15 years without any problem and only replaced the SLA battery about 5 years ago. The SLA battery will charge up to 13.8V if not in use.

I found an internal image on the Hifitest.de review of Clearaudio smart power 12V.

https://www.hifitest.de/images/testbilder/big/clearaudio-smart-power-12v-hifi-sonstiges-57224.jpg

I can clearly see a LM317T regulator chip in the circuit, I could be wrong, but I think the LM317T is to regulate the output voltage while the 19V wall wart charging the NiMh battery and at the same time supply power to the turntable. In pure battery mode, I not sure if the regulator chip is in circuit or not. Without a schematic, just take a wild guess.
The user manual also warn that if connect the 19V wall wart directly to the turntable instead of the OEM 12V wall wart can seriously damage the turntable!
Since we don’t know what is the highest voltage the turntable can safely take, and OP also concerned if 14V will be too high for his turntable, that’s why I came out the " overthinking " dumb idea of install a simple voltage regulator between the battery and turntable.

The LM317 has a drop out voltage of ~3V, so I doubt it regulates the battery output to the table. NiMH batteries need to be charged at 1C and negative delta V slope detection, thus the higher voltage input, the PIC processor and complex charging circuitry (another argument in favor of SLA batteries which are simpler to charge).

If the input of the table is designed for 12VDC, then 2 possible problems occur if you provide a higher voltage: Power dissipation and exceeding maximum voltage ratings on the input devices. Regulators (even low voltage output devices) typically have 18-26VDC input ratings. CMOS logic is usually rated to 15VDC (some CMOS devices are rated to 12V, but it would be bad practice to operate those at 12V so I doubt you find any devices with a max Vcc of 12VDC in a 12V table). Tantalum caps have standard voltage ratings of 6V, 10V, 16V, 25V or higher (6 & 10V devices couldn’t be used safely with 12V input so we can eliminate those). Power dissipation at 13.6 would only be ~13% higher than at 12V but 58% higher at 19V.

If the OP really wants to regulate the battery supply, then look at the LT3080 (or similar devices i.e. Micrel MIC29150 series which have fixed or adjustable outputs); the LT3080 is a LDO regulator (350mV) and 1.1A current rating. The output cap is critical for stable operation and should be a low ESR ceramic type located close to the output pin and ground.