Single rail splitter for preamp for TPA3116

[undefinedza]

Hi there,

I'm looking to put together a simple integrated amplifier based on a high quality preamp and the new Sure TPA3116 Class D board.

The chassis will accept 24vdc input for the sure board, but I'd like to use this supply to power a preamplifier board too.

I suppose that means I'll need to split the rail from +24vdc into +12vdc/-12vdc for the preamp board.

Questions:

1. Is it wise to run the (rail splitter + preamp) and (amplifier) in parallel off the 24vdc supply?
2. What is the best way to split the rail? A TLE2426?

Thanks in advance!

Chris

 

[doctormord]

When using capacitor-coupling, you wont need a split-supply. The get the voltage down, use a step-down-converter followed by a linear regulator to get a better PSRR.

24V -> 15V (Step-Down) -> 12V (LDO)

 

[jackinnj]

1. Is it wise to run the (rail splitter + preamp) and (amplifier) in parallel off the 24vdc supply?
2. What is the best way to split the rail? A TLE2426?

Even with the TLE2426, the potential at the output is going to be half the rail voltage, so you will need a coupling capacitor. The TLE2426 will source or sink 20mA -- probably enough for one opamp, but barely two.

You can make a higher current functional equivalent of the TLE2426 with a pair of resistors and a buffer like the LME49600, or one of TI's higher current unity gain stable opamps.

 

[xrk971]

You can also use two voltage isolated DC-DC converter chips that will let you make a dual rail supply from a single. I have used these parts from Murata before, about $6 ea and size of a 7812 regulator. With dual rail transformer you will also need a 7812 and 7912 to regulate the supplies and their ancillary parts. These isolates also eliminate ground loops in your supply vintage when powering preamp and amp from same source.

 

[jackinnj]

If using the Murata converters, make sure to use a small choke on the input, bypass the output both at the converter and opamps power pins with 0.1uF ceramics. The linear post regulators are not very effective at eliminating the switching noise above some 10s of kiloHertz.

 

[undefinedza]

Thanks for the replies guys!

It looks like splitting the rail isn't going to be easy.

jackinnj: Do you know if I can get a small pre-assembled module like this? I don't have PCB fabrication facilities.

As an alternative: Are there any high quality preamp modules available that take a single supply up to 24vdc?

 

[xrk971]

jackinnj: Do you know if I can get a small pre-assembled module like this? I don't have PCB fabrication facilities.

Preassembled Murata DC to DC modules was what I was telling you in the above post. They probably make dual rail DC DC converters so you only need to buy one.
Not hard at all.

I don't know how much current you need but this is good for 83mA. Bigger ones are available.

NMK2412SC | Bipolar / Dual Output Isolated | DC-DC Converters | Products | Murata Power Solutions

 

[Nisbeth]

I have experimented a little with some DC-DC converters, so this may be of interest to you: dc-dc | theslowdiyer

/U.

 

[undefinedza]

I have experimented a little with some DC-DC converters, so this may be of interest to you: dc-dc | theslowdiyer

/U.

Thanks Nisbeth, I read your posts.

Do you have prepopulated PCBs available?

I suppose it would be rise to regulate the output too?

 

[Nisbeth]

I have some blank PCBs left over, but nothing populated. This is diyaudio after all 😀

/U.

 

[sarathssca]

Hello,

What option was used to power the preamplifier? and how is it performing?

I am also looking for a similar thing, like, i will be powering my main amp TPA3116 board with 19.5v laptop power supply brick, and thinking if we can share the power supply for the low powered preamplifier (opamp based or DCB1 buffer, yet to decide). But the preamplifier needs split rail +/-10v.

Any idea how is LTC3260 , it has switcher to generate positive and negative voltages and has LDOs also builtin.
Or IH1215S 2w, +/-15v output dc-dc converter

thanks and regards
S Sarath

 

[Series2]

I know this is an old thread, I was searching for something else, but.........

Why not just use a single supply for the opamp(s)? This is what I have done for my tpa3116 amps, it works just fine with most opamps, even ones not specifically designed for single supply operation, as long as you make sure to keep the signal a volt or more lower than the supply.