Another project, all digital DDX amplifier

[SoldierAnt76]

Hifimediy and Nick,

Whatever happens with this board, I hope you keep experimenting with the DDX digital chips. In the near-future, almost all music and video will be PC-based and a lot of us would like to see a good digital amp. Analog is so twentieth-century.

One thought: you're spent a lot of time working on the hardware interface, but it sounds like the chip is actually software-based. I don't know what the software support for DDX is like, but a USB interface (like MiniDSP) might be a useful addition. Maybe even a critical one.

[nakamoomin]

I've encountered a similar problem in HW.

It sounds a bit like a floating port (i.e one that is not terminated high or low) We had a similar issue when upgrading from a pin-compatible 1Mbit to 2Mbit Ram chip on one of our products.

One of the pins that was NC on the 1Mbit chip was "address bank selector" on the 2Mbit version. As the HW design was for the former, the gate was left "in the air" this caused the DDR to write/read randomly between bank 1 and 2. BAD chip!

However: as SoldierAnt says; the STA320 seems to be SW based, but make sure there are no HW selector for high/low bitrate..

Also: a USB-interface to set custom EQ biquads, enable/disable "night mode", etc would be very much appreciated!

[SoldierAnt76]

Originally Posted by nakamoomin

It sounds a bit like a floating port (i.e one that is not terminated high or low) We had a similar issue when upgrading from a pin-compatible 1Mbit to 2Mbit Ram chip on one of our products.

Nakamoomin's suggestion has the ring of plausibility; hopefully the problem is hardware-related, and easily fixed.

Even so, it's worth pondering what would happen if a software bug ever surfaced. How would any of us diagnose the problem, or update/modify the firmware? Swapping out resistors or capacitors is relatively easy, but a problem with the code would be difficult for users to troubleshoot, much less fix.

So a USB port and software interface ought to be standard-equipment on a product such as this one. Besides, if people had the ability to customize their board through software, they wouldn't need to pester you so much to keep making new versions.

[hoxuanduc]

and makes music!

Initial impression:

- Strength: Sounstage and imaging,PRAT, midrange clarity
- Weakness: treble sharpness. Perhaps I need to play some more?
Excellent build quality

Comparison system: Audiosector USB DAC -> B1 preamp -> Modded sure amp (Dayton input & output caps, air core coils), not as good PRAT but smoother.

Speakers are Pispeakers model 2 (Suits me better than RS Natalie P.)

Thinking about replacing the coil with Wurth. I think the stock coils are 11uH, which Scott Endler recommended replacing them with 4.7uH 9.3A Wurth.

At first I had some trouble getting it to play. Things to watch out for:

- Main connection to the Connex SMPS is GND - AC - AC
- Out from SMPS is GND - POS into GND - V2 in the DDX320
- DIP switch set to ON-ON-ON-ON (pass thru). The default setting is OFF-OFF-OFF-OFF which is 320Hz High pass. Make the sound tiny and stuck to the speakers

[rew432]

You bought this amp, there are a couple of questions.
** Do I understand that it is sufficient to use the AC?
** What power is required transformer?
* Sorry if errors translate into English with the help of the program.

[hoxuanduc]

Originally Posted by rew432

You bought this amp, there are a couple of questions.
** Do I understand that it is sufficient to use the AC?
** What power is required transformer?
* Sorry if errors translate into English with the help of the program.

I used the Connexelectronics power supply but I think you can use a 20-0-20 VAC transformer rated about 300VA without any problem.

Duc

[Nick122147]

Any other opinions on this now after we've shipped a few?
3 left in stock and we will probably not make more until we fix the problem (which we are not any closer to unfortunately).

[soundcheck]

Originally Posted by Nick122147

Any other opinions on this now after we've shipped a few?
3 left in stock and we will probably not make more until we fix the problem (which we are not any closer to unfortunately).

If you ask me. Full digital amps have the capacity to blow away standard DAC-amp setups at a fragment of cost.
I do own a TAS5706 amp since almost two years and wouldn't swap it against my TP Sabre+amp anymore.

I'd more than understand why the audio industry is not interested to go the full digital route.
There'd be a high risk that you'd kill large parts of the DAC market as well as amp segment as well as analog IC cable segment.
(Of course that would apply also to your own portfolio.)

Last Sunday I decided to order one of your products. Unfortunately I'd been late. All modules were gone. ( I had PMed you guys)

Some feedback:

(A friend of mine gotta DDX320. His findings match my experiences with my TAS5706)

1. What's needed is a highest quality digital transport, since the input stage
is not able to recover rather average quality input signals at highest quality.
The same rules apply as for top quality DAC input/recovery/reclock stages.
2. Your amp seem to lack a high quality spdif pulsetransformer on the input. That one is needed to keep the noise out and ususally makes a hell of a difference.
3. As usual and being discussed a hundred million times: A top PS is key to success.


Full digital amps are IMO the best kept secret in the audio world. And I'm sure many manufactures want to leave it this way.


Please put some more effort on getting your problems fixed and you might want to have a look at improving your input stage.

Rev 2 of your product could be a real winner.

Put me on the waiting list. Good luck.


Cheers

[soundcheck]

Hi folks.

I just installed a DDX320. Got one ( or better a friend of mine) from the last 45$ batch.

After a couple of hours my first impressions are pretty positive.

Out of the box it sounds pretty good. The sound signature is pretty similar
to my TAS5706. The greater muscles of the DDX make the amp more
dynamic even on my 98db/SPL speakers.
Compression at higher levels disappeared. Great stuff.

Right now It's breaking in. It still seems to improve from hour to hour.
I'm sure the DDX got greater potential then my 5706 installation. It'll stay.
(The pity:I'd need one more amp for my woofers - hopefully we'll see a new batch coming out soom)

I'm wondering now what power supply to go for?!?!? Right now I'm using a decent switching single voltage 24V 6.5A device. Nothing spectecular.

What should I Iook at when selecting the best possible PS for the DDX:

SMPS or linear PS
Single voltage or double voltage
Power ratings ( bigger = better ??).
What brand!?!? Many people seem to rave about Connex SMP500R 24 V ( single or double voltage?) Are there alternatives?

Please let me know any other tweak potential.

Thx.

Cheers

[soundcheck]

after being positive in the early hours, i have to report that i'm experiencing a pretty high noisefloor on this amp.

and i'm not talking about the general noise flaw here. that one i experienced too.

i tried two different power supplies. the better supply made the high noisefloor even more obvious.
i've been also running that amp on 24Vbatteries. same thing.

i also tried toslink vs. spdif. same game.

it starts with playback start. it seems to be related to the processing. if playback is stopped it's dead quiet.

it's on any samplerate i tried.

i'd appreciate any hints what to do next - maybe i've done something wrong.
though you can't do much wrong here -- i guess.

my tas5706 still plays dead quiet in comparison.

cheers