6V -> 5V ?

[ggking7]

I'm isolating my Wavelength Proton USB-powered DAC from the computer with one of these which incorporates an ADUM4160 chip:

Ultravox - SGD70.00 : Welcome to the diyparadise e-store!

I'm providing power with a 12V SLA battery. The isolation removes the edge and smear from the sound but if I connect directly to the computer the sound is a bit more live and involving. I think this must be due to the circuitry between the battery and the DAC. Is there any sort of simple way to convert 6V to 5V so I can connect a 6V SLA battery as directly to the appropriate pins on the USB cable as possible?

[DigitalJunkie]

6V input for a 5V output doesn't leave much headroom. Some sort of LDO regulator might work,but even then it's close.
It might be better to use the 12V battery,and regulate that down to a clean 5V. Just about any 5V regulator that can handle the current required by the DAC should work.

[agdr]

Originally Posted by ggking7

Is there any sort of simple way to convert 6V to 5V so I can connect a 6V SLA battery as directly to the appropriate pins on the USB cable as possible?

0.45V maximum dropout at 500mA for $1.60:

Digi-Key L4941BV


0.25V maximum dropout at 500mA for $9.40:

Digikey UCC283T-5

[ggking7]

It might be better to use the 12V battery,and regulate that down to a clean 5V.

Yeah, that's what I'm doing now. The Ultravox has an LT1085 regulator:

LT1085 - 7.5A, 5A, 3A Low Dropout Positive Adjustable Regulators - Linear Technology

Is there a better choice?

Would I get better results from an 8V battery since the voltage wouldn't have to drop as far?

[!]

None of this is making any sense to me. What are you trying to accomplish? You don't need an isolation chip, you only need to use something other than the computer's 5V USB power in order to clean up the power to the DAC, and yet, when you clean up the power you find it is less lively.

Yes, many people report less accurate (distorted) output from use of a SMPS makes something sound more lively. So, which do you really want? The accuracy you were hoping for by isolating the DAC from the noisy computer SMPS? Or the liveliness that comes from having it connected to the SMPS?

12V SLA battery is not needed in any way, nor 6V SLA, BUT if you insist on using 6V SLA battery, simply put a typical 1A silicon diode in series to drop it down to ~ 5.3V. Any USB powered DAC chip that takes 5V will certainly handle as little as 0.3V increase.

BUT, forget the SLA battery as it does nothing useful. Use the computer's 12V rail (connect with a molex socket to the PSU's wiring harness plug), a basic LM317 regulation circuit to regulate down to 5V, and put ferrite beads on the LM317's input and output pins to handle highest frequency noise. Use that 5V to power the DAC.

Another alternative since you already have the 12V SLA battery is drop that down to 5V with a regulation circuit.

[ggking7]

I would like to connect a battery as directly to the DAC as possible, with as little circuitry between them as possible. It sounds like the 1A silicon diode might be just what I'm looking for. Do I just solder the diode into the lead attaching the battery to the USB pins? Would I do this on the positive lead only?

What about a 6.6V battery pack like this:

http://epbuddy.com/index.php?main_pa...products_id=25

Is there a diode that would drop the voltage to around 5V?

[nigelwright7557]

Originally Posted by ggking7

I would like to connect a battery as directly to the DAC as possible, with as little circuitry between them as possible. It sounds like the 1A silicon diode might be just what I'm looking for. Do I just solder the diode into the lead attaching the battery to the USB pins? Would I do this on the positive lead only?

What about a 6.6V battery pack like this:

http://epbuddy.com/index.php?main_pa...products_id=25

Is there a diode that would drop the voltage to around 5V?

Use 2 standard 1n4004 diodes in series or one 1v7 zener.

[!]

Originally Posted by ggking7

I would like to connect a battery as directly to the DAC as possible, with as little circuitry between them as possible. It sounds like the 1A silicon diode might be just what I'm looking for. Do I just solder the diode into the lead attaching the battery to the USB pins? Would I do this on the positive lead only?

What about a 6.6V battery pack like this:

http://epbuddy.com/index.php?main_pa...products_id=25

Is there a diode that would drop the voltage to around 5V?

At low currents a typical silicone diode will drop a little under 0.6V. Some use the generic value of 0.7V but in this case it would be better to consider the real forward drop as used in the circuit and round off to 0.6V instead of 0.7V per the example below. You put multiple diodes in series to drop each additional 0.6V in increments. This is only for silicone diodes, other types like schottky diodes have a lower forward voltage drop, BUT you don't really need to hit exactly 5.00V for the DAC, just to stay within a safe range and have the power be stable which it will be with a battery.

You could put the diode(s) on the positive power lead or on the ground, either will work but for esthetic reasons putting it on the positive lead is usually preferred. It would need to be after any point in the circuit you are using to recharge the battery if you have implemented some way to do that since a diode rectifies, lets current flow only one direction.

The linked battery pack is 2 series of 2 parallel cells. What is the peak voltage the charger you will use, terminates charge at? "Normally" it would be 4.2V per cell so your sum voltage from that pack peaks at 8.4V. You could just keep adding diodes to drop that down to a safe level, say 5.5V or so, BUT the problem is that (8.4V - 5.5V = ) 2.9V, divided by # of diodes you'd need to accomplish this (2.9V / 0.6V per diode = 4.8 diodes, rounded up to 5 diodes = 0.6V * 5 or 3.0V...

3.0V will work fine when the pack is fully charged, dropping voltage down to a safe 5.4V, but once the pack starts to drain you don't have enough voltage margin, it'll end up as low as roughly 3.0V which is "probably" (consult the DAC chips' datasheets, I don't know for sure) too low a voltage.

Thus, with the linked pack your best bet is an LDO (low drop out) regulator instead of diodes. One example of a popular LDO regulator that would work is National Semiconductor's LM1086 (or the higher current versions, LM1085 or LM1084). They have a maximum dropout voltage of 1.5V at 1.5A, but at the low current your DAC uses the dropout voltage would be closer to 0.9V, meaning you can just make the circuit output 5.0V and it'll work over the entire range the battery pack voltage spans as it discharges.

It is a similar situation with the SLA 6V battery. We're talking about 6V as if it's 6.0V but it's a battery of 3 cells in series with 2.0V nominal voltage per cell but at full charge each cell is up around 2.15V so it's actually 6.45V fully charged. However, and again you should check the DAC chips' datasheets to be sure what the maximum voltage they can tolerate is, I'm guessing there should be no problem with 6.45V - 0.6V from a single diode in series = 5.85V.

A 6V SLA battery will be considered fully discharged for the purpose of preserving its lifespan and the purpose of calculating lowest voltage in use at about 1.8V per cell if not slightly higher. 1.8V x 3 cells = 5.4V. The DAC should still be able to run at ( 5.4V - 0.6V from one diode's forward drop) 4.8V so a single silicone diode in series would work with your SLA "6.0V" battery.

lol, such a long reply to a simple question. Sorry.