Class D amp with I2S input

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DcibeL

DcibeL

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Joined 2003
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#1
Hi All,
I am wanting a small amp for use with my minidsp, but want to avoid the extra DAC in between. There used to be a MiniAMP that had direct I2S input and plugged right into the minidsp, however it is NLA.

The only thing I've found so far is the TAS5713 used in the Hifiberry amp, I suppose with some finagling the hifiberry could be wired into the minidsp as well instead of a Raspberry Pi.

Are there any other off-the-shelf solutions for small amp boards with I2S input?
 
#6
Thanks for the responses. It looks like my cheapest option is the STM eval board at CAD$70ea. Not exactly what I had in mind considering I'd need two for a full 4 channel output and they are fairly low power.

Maybe it is a better option to use a pair of Curryman DACs with external amps. I was hoping that I could have a simple all-in-one solution with MiniDSP and integrated DAC/AMP. I really just wish the MiniAMP was still available.
 
#7
DcibeL said:
I was hoping that I could have a simple all-in-one solution with MiniDSP and integrated DAC/AMP. I really just wish the MiniAMP was still available.
Click to expand...

You might recognize the right side of this PWB layout: it is that miniDSP piggyback board. But the cool stuff is on the left side. It is an ADAU1701 circuit (basically the same as the miniDSP board) plus 4 nice little power amps. The amps are at the top: there are two stereo SSM3302's. These amps can be run at 15-18V and generate an honest 15W per channel. That's not a lot of power, but by using the ADAU1701 as an active crossover, you get enough crest factor improvement that 15W might be adequate. The board also has two additional analog outputs for a subwoofer or a pair of woofers (using one of the digital output lines from the ADAU1701).

soundbar_amp.JPG

I built up one of these boards but I still haven't tested it. Got the SigmaStudio program for this board ready and it has been tested, but there is still some additional firmware needed. I've got too many projects right now...so stuff is getting done slowly.

There is a "clone" of this board that was done using DesignSpark that will be made available as an "open" design. If someone wants to get a board made, I'll build one up and test it.

The STA333 doesn't look that interesting--an STA350 version would be much nicer. I was thinking about getting one of these to play with, but I'll probably end up making my own design: STA350 pure digital power amplifier board with a coaxial optical fiber USB input 50W+50W 2.1/ 2 support mode. I've built a number of boards with the STA328, so I've got working software for the STA350. The ST amps have some number-crunching limitations (24 bit coefficients), but overall they are nice amps.
 
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#8
Hi Neil, please consider the following set of boards :

SPDIF-in to I2S-out (with a SPDIF repeater function)
  • a SPDIF cinch and transformer as digital stereo input
  • a "consumer grade" SPDIF-in chip (WM8504) having no access to the "U" bit of the AES/EBU frames
  • a 6-pin header carrying GND, LRCLK, BCLK, DATA, MCLK as outputs
  • a CMOS-buffered SPDIF dumb repeater with careful cable impedance matching
  • a SPDIF transformer and cinch as digital stereo output

I2S-in filtered STA350 power amplifier (credit-card sized)
  • a 6-pin header carrying GND, LRCLK, BCLK, DATA, MCLK as inputs
  • a 6-pin header carrying GND, LRCLK, BCLK, DATA, MCLK as outputs (passive repeater function to same boards in a multiway speaker)
  • a STA350 configured in "mono parallel BTL"
  • a strap telling the STA350 what audio channel to process (Left or Right or Sum)
  • a 4-pin I2C header enabling a) the designer to program the STA350 filters, and b) the end-user to operate the volume
  • a 4-pin I2C header (passive repeater function to same boards in a multiway speaker)

Remote control receiver (RF type)
  • a remote control receiver (RF type)
  • a Cortex-M0 CPU as remote control interpreter
  • two I2C interfaces for commanding up to four STA350 boards
  • a strap telling the Cortex-M0 if this is stereo 2.0 or stereo 2.1
  • a strap telling the Cortex-M0 if the associated speaker is Left, Right, Sub, Center, Left Rear or Right Rear, or anyting else (8 choices in total).

SPDIF splitter (powered by external + 5V)
  • one SPDIF cinch and transformer as digital stereo input
  • two CMOS-buffered dumb repeaters with careful cable impedance matching
  • two SPDIF transformers and cinch as digital stereo outputs

Let's build a 2.1 system having 3-way Left and Right speakers.

First of all, we attach a SPDIF splitter to the CD/DVD/Blu-ray player SPDIF output. This way we'll have the impedance of the SPDIF transmitters carefully matched (tweaked) to the cabling we are using.

In each 3-way speaker we'll find :
1 x SPDIF-in to I2S-out boards
1 x Remote control receiver (RF type) boards
3 x I2S-in filtered power amplifier (credit-card sized) boards

In the separate subwoofer we'll find :
1 x SPDIF-in to I2S-out board
1 x Remote control receiver (RF type) board
1 x I2S-in filtered power amplifier (credit-card sized) board
Such separate subwoofer gets connected to the SPDIF-out of one of the two Speakers.
 
#10
steph_tsf said:
Let's build a 2.1 system having 3-way Left and Right speakers.
Click to expand...

Been there, done that.

sta328-USB-done.jpg


Here is a link to a briefing that I gave at DCDIY2009 that explains this amp in more detail. But that was Rev A. Rev D has SPDIF input/output using the WM8805.

The STA350 is actually a lower-powered version of the now discontinued STA326/STA328. There are some minor improvements internally, but the main difference is that the earlier chips had the heatslug facing up, which allowed more output. The STA326 was actually the same as the DDXi-2051, which was introduced way back in 2004. You can still buy the DDXi-2051 from Gerber.

BTW, I have lots of code for reading IR remote controls. But it doesn't take a 32-bit micro to decode a 1-bit stream--it just takes a chip with a good timer module and an efficient interrupt architecture. I actually have code for a number of different IR protocols--this link is a briefing on how the logic works to identify the protocol.
 
#11
I2S filter ADAU1452 (credit-card sized)

  • a 6-pin header carrying GND, LRCLK, BCLK, DATA, MCLK as inputs
  • a 6-pin header carrying GND, LRCLK, BCLK, DATA, MCLK as outputs
  • the ADAU1452 32-bit DSP
  • a strap telling the ADAU1452 what audio channel to process (Left or Right or Sum)
  • a 6-pin header enabling the designer to program the ADAU1452
This way one can add more filtering functions like a delay and a FIR filter.
Such board to be installed between the I2S audio source and the I2S-in filtered STA350 power amplifier.
 
#12
I2S DSP with ADAU1452 (credit-card sized)

  • a 6-pin header carrying GND, LRCLK, BCLK, DATA, MCLK as I2S input
  • the ADAU1452 32-bit DSP
  • a 6-pin header carrying GND, LRCLK, BCLK, DATA, MCLK as I2S output #1
  • a 6-pin header carrying GND, LRCLK, BCLK, DATA, MCLK as I2S output #2
  • a 6-pin header enabling the designer to program the ADAU1452
By hooking a board like this between the stereo I2S input and up to four I2S-in filtered STA350 power amplifiers, you can build a 4-way speaker relying on delay lines and large FIR filters. As free bonus, the ASRC that's inside the ADA1452 can act as jitter buster and can act as audio format converter like 44.1 kHz/48 kHz/96 kHz to 48 kHz.
 
#13
I2S DSP with STM32 F411RE (credit-card sized)

  • a 6-pin header carrying GND, LRCLK, BCLK, DATA, MCLK as I2S input
  • the STM32 F411RE 32-bit ARM Cortex-M4
  • a 6-pin header carrying GND, LRCLK, BCLK, DATA, MCLK as I2S output #1
  • a 6-pin header carrying GND, LRCLK, BCLK, DATA, MCLK as I2S output #2
  • a 6-pin header enabling the designer to program the STM32 F411RE
By hooking a board like this between the stereo I2S input and up to four I2S-in filtered STA350 power amplifiers, you can build a 4-way speaker relying on delay lines and short FIR filters.
 
#14
steph_tsf said:
I2S DSP with ADAU1452 (credit-card sized)
Click to expand...

Go for it! I don't have any interest in working with the ADAU1452 right now.

My current big project is a 20-channel line array board. It's got 3 ADAU1701 chips with variable delay on each channel. I want to be able to send "curvature" information via the SPDIF User Data to simulate a physically convex (or concave) line array. I'll be busy for a while 🙂
 
#15
I2S-in TDA7801 (or TDA7802) 4-channel power amplifier (credit-card sized)
  • a 6-pin header carrying GND, LRCLK, BCLK, DATA1, DATA2 as twin I2S inputs
  • a TDA7801 (or TDA7802)
  • a 4-pin I2C header for properly configuring the TDA7801 after power-up
The volume control needs to be done in digital by scaling the audio data over I2S. This must be done by the board acting as preamplifier and crossover that's preceding the TDA7801 board.
On top of this, using the I2C control port, two bits serve to adjust the full scale voltage of the TDA7801 (roughly 3.0 Volt, 5.5 Volt, 7.5 Volt, 13.0 Volt). This helps improving the S/N ratio at low listening volumes.
 
#17
steph_tsf said:
I2S-in TDA7801 (or TDA7802) 4-channel power amplifier (credit-card sized)
  • a 6-pin header carrying GND, LRCLK, BCLK, DATA1, DATA2 as twin I2S inputs
  • a TDA7801 (or TDA7802)
  • a 4-pin I2C header for properly configuring the TDA7801 after power-up
The volume control needs to be done in digital by scaling the audio data over I2S. This must be done by the board acting as preamplifier and crossover that's preceding the TDA7801 board.
On top of this, using the I2C control port, two bits serve to adjust the full scale voltage of the TDA7801 (roughly 3.0 Volt, 5.5 Volt, 7.5 Volt, 13.0 Volt). This helps improving the S/N ratio at low listening volumes.
Click to expand...

Hi,
I'm interested too at this amplifier. Do you know if exist a board with this amplifier that can be used directly with miniDSP or Raspberry?
Thank you
 
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