Another project, all digital DDX amplifier

[soundcheck]

Originally Posted by ackcheng

Hi Soundcheck,

Where can I buy the Wuerth PD Typ XXL you mentioned? Any model number?

Ackcheng

Würth or english Wurth

Partnumber:

7447709100

RS-Online
Mouser

[soundcheck]

Another update.

This new amp is kind of weired.

On one hand it does a lot of stuff better then the old one.
E.g. Resolution is better, stage is deeper, everything gets more realistic.

On the other hand it also seems to add some little flaws. You sit there and think "Hey great". But still you got a feeling that something is not quite
right.


Today I continued my tweaking journey.

1. bypassed (wire) the power supply diode D7 - it's not needed for DC (Hifime
should consider a clean DC input for the next revision.)
2. removed L7 and D2 (output filter for the Techcode DC/DC converter that
I removed earlier)
3. Replaced the 330uf Panasonic FC with a 1000uf Blackgate NP.
4. Decoupled the TSCO with a 330uf Oscon (There is no decoupling cap at
the clock pin - just a little ceramic smd)

Result:

Afer 3 hours break-in I can say it's getting better again. Impressive stage
depth and air. I like what I hear.
At this stage you don't realize that you listen much too loud at earbleeding levels. If you stop playback, Tinnitus says "here I am" .



However. I do have the feeling that it is still not perfect.

E.g. Somehow metal percussion instruments ( those little hanging chimes) still don't develop that perfect 3 dimensionality that I listened to before.

Let see maybe I get that fixed.

Enjoy.

[glt]

Following with interest. Is the chip still the STA320?

[soundcheck]

Yep. STA320.

[CFT]

Thanks for sharing your upgrade journey!!

[soundcheck]

Hi there.

Today I received the remote control. Batteries are not included!

Advise:

Look for those button cell battery sets.
You'll usually get 24 button cells at 1.99 or similar. Usually 4 cells per type.

I was first in a shop where they charged 4.79 for one of these cells !!
Now I'm down to 8ct.


#####

Those, who even want to save the batteries or don't have access to them, can try to setup a Linux remote control - if the PC comes with IR transmitter.

LIRC (Linux Infrared Remote Control) Profile

You can make your Linux PC a remote.

I already recorded and tested the DDX remote keys on my Ubuntu installation. It's working.

I sent the lircd.conf profile for the "DDX320 V2" over to the lirc database manager for publishing. It should be available soon.

PM me, if anybody is interested in this file already now.



Cheers

[soundcheck]

Short update.

Since I'm now in the position to turn on the HP crossover again, I just did it.
The HP also works on a 2.0 setting.

I used to run the HP at 80Hz on the V1.

It seemed to lift some low-end load off my Bastanis fullrange speakers ( or perhaps also off the amp).
The speakers usually run free (without any crossover parts) up to ca. 9k. Dipole rolloff starts at around 200

I had the impression that it got better (little more air and a little cleaner) with the HP turned on...
...on the V1.


The situation IMO changed now with the V2.

As I mentioned once or twice already, the resolution increased more than obvious.

Now.

With the HP in the loop, you can easily hear the losses caused by the DSP. Fine details just seem to get slightly smeared.

This effect I consider worse, then the advantages of having a HP in the loop.

Bottom line. The HP/DSP will stay off from now on.

Speaks for the quality (after tweaking) of the V2.


Note: I hope an on-the-fly HP configuration -- that's what I did - can be done without causing some nasty sideeffects.
I didn't reset the device after the config was done. I just would like to mention it.


Cheers

[soundcheck]

Final update ( will be on a trip for the next 2 weeks).


I reported that I wasn't really happy with the upper register micro dynamics (e.g. chimes with limited 3-dimensionality and attack)

I think I managed to improve that situation.

I now bybassed the Lelons with 2* 0,52uf KP and also hooked up a little silver-mica cap. My guess. The Lelons needed a little turbo in the upper
range. I like what I hear.


My Tweak-Summary:

* Decoupling needs to be improved. E.g. Clock/Vdd STA320/Toslink.
Maybe all ( just 6) Elna Stargets should be swapped

* The choice of small caps can be improved - IMO at least Silmic II should be used. Extra cost are almost neglectable. For digital lowest ESR Oscons Sepc should be considered.

* Output coils need to be swapped (e.g. shielded Wurth). And best
mounted underneath the board.
If not possible current coils needs to be stabilized ( e.g. BluTack or similar). The mounting is pretty poor. They vibrate and ring.

* Use of LipOFe4 3.3V supply instead of DC/DC converter+filter. (IMO most important tweak!)
For future board revs HifiMe should consider an option for an internal/external 3.3V supply switch

* Lelon caps need a bypass turbo. You also need to stabilize the Lelons
to avoid vibrations.

* In case of DC operation input diode should be shorted. In the
future HifiMe should consider a 4th input for DC only.


* For those who run SPDIF. Get yourself a pulsetransformer ( e.g. from Pulse) to isolate your source.
Though --- avoid double isolation! Check if your source comes with pulsetransformer already.
Unfortunately HifiMe didn't follow my earlier advise on this one. There are plenty of inputs.
At least one should be transformer isolated.


As you can see above, I'm talking mainly about PS related stuff.

I'm not a board designer, though when looking at the board the routing of powerlines and the positioning of decoupling caps can and should be improved - even if the board gets a bit larger. I also think that the output section needs some more air to breathe.


Bottom line. All above tweaks cost you ( and HifiMeDIY in case of a little re-design) close to nothing. With those
being implemented, you'll end up with a pretty high-end full digital amp.

As I said before . Our TP Buffalo (LiPofe powered+ more tweaks) + amp chains are no longer needed. (but that I achieved with my tweaked DDX320 V1 already.)


Just to mention it. I'm not using the amp for < 100Hz..
I'm running from the SB Touch Toslink to the DDX and SPDIF to a Behringer DCX2496 for the subwoofers.

Make sure you have a clean and fast 24V supply and a very good transport feeding that amp.

For less sensitive speakers (<<89db/w) these amps might lack a little bit of steam.



To avoid that the list of my tweaks makes the stock V2 amp look a questionable choice.
I'd like to say that even without all these tweaks the stock DDX320 V2 is a very nice sounding all-in-one solution.


Enjoy.

Cheers

[ctkhaw]

can I use this amp with .1 channel without amplification and feed the line level signal to a powered sub?

[goosewing]

Does anyone have any idea or information on whether these amps implement a negative feedback lop and how they go about it?