could use some help with a TAS5518 amp

[legomanww]

I've built an amp based on the TAS5518 and a PIC, but I'm having a hard time getting the TAS5518 to do anything.
When I look at the I2C communications, pretty much all the time I don't get back an ack bit, it just stays high. But occasionally it appears to receive an ack bit, but there is no change in the results.
Also, the valid and PWM outputs are all at ~2-3mV, and don't change.
I already changed out the chip, in case I had damaged it previously, and there is no change in response.

Anyone have any ideas?

Thanks,
William

[legomanww]

An update, I played with it some more and it seems to be consistently getting an ack bit now, but the outputs all still remain at 2-3mV dc without any signal.

[legomanww]

I figured it out, it is all working properly now.
I think it was a timing issue in the communications, as well as the reset signal timing.
For the curious, it uses PCM1802 for input, a PIC to control the TAS5518, and TAS5342 on the output.

[SunRa]

Kind of late to revive this thread but I was just wondering, how do you find this amp? Can you compare it to other designs?

Thanks!

[legomanww]

I like it, I think it sounds very nice, but I don't have any other designs to compare it to (other than old stereos), sorry... I haven't had any noticeable distortion or hiss (other than what I believe is coming from the source) and it is plenty powerful for my needs so I am happy with it.

[Blinddot]

Nice job, I'm very interested in a project with digital Purepath HD chips, does this amp have digital input? are you interested in selling modules?

I'd love to see pics..

thanks!

[legomanww]

I did not use a digital input since I wanted to be able to use it with a variety of sources. I also wasn't convinced I could output an decoded/uncompressed stream from my computer and I didn't want to deal with decoding...

I'm not sure that I have the time to develop/sell modules, maybe if it's small or no time crunch. Which part were you interested in, in particular? The output stage?

I can try and upload pictures this weekend.

[Blinddot]

I guess you could easily use a miniDSP miniStreamer for USB, or miniDSP miniDigi for SPDIF

MiniDSP - miniDIGI
MiniDSP - miniSTREAMER

I'd personally be using SPDIF..

Regarding the parts of the amplifier I'm interested in, I'd say everything but the AD converter, but I guess it wouldn't be much of a problem to have it onboard if it makes it easier for you.

I'm wondering about the ability of this "power D/A" to get rid of incoming jitter from the SPDIF, Is jitter rejection a task for the miniDigi board or not? what would be the ideal clocking strategy on such a design?.. forgive my newbie questions.

BTW, a TAS5631 design would be very exciting as well

[legomanww]

Those are interesting boards. I hadn't heard of their products before. What is the advantage of a TAS5518+TAS5631 amp connected to one of the miniDIGIs over their amp+dsp combo? Better dynamic range? Lower noise?

I imagine the SPDIF input stage would be the part that should remove jitter, but I don't know.

[Blinddot]

I think you wouldn't need their DSP board in order to make a power D/A, their miniAMP uses TI purepath chipset as well, I'm not sure if it si "purepath HD" or just plain purepath chipset.. but anyway the difference would be POWER.. the miniAMP is 2x20W and as far as I can understand from TI site TAS5631 could output 2x300W, the last PurepathHD are suposed to have more power and more fidelity..

I'd love to get a board with I2S input and TAS5518 + TAS5631, I guess all I'd have to do is to get hold of a miniDIGI board and a power supply.

My only concerns are the volume control and the jitter rejection..

The only power D/A's I've found at a moderated price are sumoh's, but still underpowered for my needs
| SUMOH | True digital amplifiers

wadia, TacT, NAD and Steinway-Lyngdorff are out of my budget, and nobody is selling DIY modules yet, besides the very low power miniAMP from miniDSP.

I'd buy on blink of an eye a TAS5518 + TAS5631 I2s input module, if anybody was making it.. I guess purepath HD are still pretty new chips, the funny thing is that I see very nice TAS5630 analogue amps like these ones:

Class D Audio TI-600 Amplifier - Class D Audio Amplifiers - PRODUCTS

I guess digital implementation with digital PWM modulators is more complicated than analog PWM modulators, that's why I got interested on this thread, cos you were using TAS5518..

but to be honest I'm a complete newbie regarding all this stuff, I just find it a very interesting technology I want to try, since my only source is a computer, so a power D/A makes sense to me.