AK4396: best solution for output stage

[Joe Rasmussen]

... who actually needs such a "hot" CDP?
The arrangement is very similar to Audio Note higher priced DACs.

I know exactly what you mean. But there are many who get nervous otherwise, as if something is wrong. Take the output from a voltage DAC with tx and one side (the "+") via coupling cap and single pole filter, quite inexpensive and still quite good and done this more times that I can count. But the output I have seen have varied from 0.56V to 1.35V - but... and if they use passive preamps (booh)... use proper preamp and no problem.

Cheers.

Joe R.

 

[tvrgeek]

Hi Thomas
I don't know anything about the EMU 0404 USB. But I really do not like the idea of connectiong the computer to the stereo. Computers are a noise-nightmare.
If you do connect, galvanic isolation would be wanted. But almost any USB DAC/Soundcare do not have this feature, and will result in noise entering the stereo. This could very well lead to the symptoms that you mention.

About the 2 different schematics in the AKM datasheet. No, the 2nd one is not better. I just gives you balanced output to. But it is still an op-amp, follow by another op-amp. Not that good.
You could get OK results from trying different op-amps. But it's still an op-amp and sounds just like it.
I would go for a discrete analog stage using NO negative feedback.

If you do choose an op-amp, my suggestion is the old fashion NE5534. If you can get the "A" version it's even better.
I have seen many people change from NE5534 (5532) to newer and "better" devices, only because of the better specifications in the datasheet. People who actually run a blind-listening-test, tend to go for the NE5534. For an op-amp it's not that bad, and sonically it will run down most of these new "racing-op-amps".

I have to disagree totally. The newer National chip improvement is stunning. Granted, some drop in without checking compensation, power supply etc. so the results are worse. I mention this because I am not a fan of making chips designed to drive a buffer try and drive cables. The "softer" sound is your high end falling off a cliff. The OP is looking for a diff-output. Might I suggest a simple THAT driver rather than an op-amp?

Another idea is to use a pair of transformers. Jensen maybe.

Some sound cards have a TOSLINK output. This eliminates any fear that some magic is traveling through a USB to the output. Mine has a PCM coax as well. If not, one can convert USB to fiber at the PC with an external box. Same result. Never seen a ground loop get past fiber!

 

[Andrea:]

I have to disagree totally. The newer National chip improvement is stunning.

The LM4562 is nothing so stunning. There's better around: LME49720HA (notice the HA bit), and, even better, the OPA1612.

The LM4562NA was a mediocre sounding opamp for me. I prefer the cheaper LME49723.

 

[Andrea:]

Try replacing the NE5534 with Linear Technology's LT1357, BTW, then let me know

 

[Andrea:]

For the AK4396 specifically, BTW, the LT1357 would be a really nice match. My bet.

Otherwise, the LT1028ACN8 would be a great match as well. My bet.

 

[audiodesign]

For Cheers

 

[tvrgeek]

I can barely keep up with the chips you mention. You must have an easier access. I have to wait for Diga-Key, Mouser and auctions! I am still waiting on my test board parts. The 4562 was so much cleaner than the 5532. But I only have one.

I ordered Walt's new book. That should be interesting.

darn, it sounds like my office receiver just blew up. Better sign off and check it out. Funny noises with the CD finished.

 

[Andrea:]

Easy access is easily attained by means of free samples

Free or almost...in case you order samples from National.

Instead TI is free like LT

 

[QSerraTico_Tico]

For Cheers

Glad I got rid of the Lundahls LL1636....

 

[regal]

-+What you want to do is have 4 discrete buffers (L+-.R+-) then use a discrete balanced to unbalanced conversion to get the CMRR that give the DAC chip its good S/N specs. I can probably dig up the schematics if you can't find them.

 

[Pano]

Just FWIW - I measured the output impedance of the AKM4393 (as used in the DCX2496) and found it to be 100 ohms. I found no change in output level at all from no load down to ~80 Ohms. Then the output clips and goes into protection. Frequency did not seem to matter, but I did not do a whole 20-20K sweep.

This is posted over in the DCX thread. I have not measured a 4396 yet.
What would be interesting to know is if distortion changes with load.
Talking to the engineers at Crystal about the CS4398 they only spec it at 1K load. Anything else and they "don't know."

 

[Jaimo]

Replacing the DEQ's AK4393 with a AK4396

I'm feeling a bit lazy tonight, so maybe someone can tell me if the 93 can be desoldered and the 96 soldered in in it's place in a DCX2496? Without any other mods that is.
Cheers

Hello Brett - the AK4396 is a direct replacement for the AK4393. I just spent the morning doing the necessary micro surgery and my initial impression is that this mod is only worth doing if you rework the PSU and fit an output transformer or change the op-amps.

The 4396 also appears to have a higher output level than the AK4393 - my DEQ now clips frequently when using the levels I had set up for the AK4393.

I plan to fit a transformer next and will write up my 4393 vs 4396 impressions soon.

 

[nonsub]

When you switch to AK4396 on the stock board what follows the DAC's output before the connector? Just the 10uf caps? Thanks!

Also on another note since no one is responding on other threads... is there a 1.17 firmware?

 

[audiodesign]

Here the output stage I have designed for the CS4397 in the Monrio CD top loader (value 10000$).

THe AKM is quite similar as outputs so it could be used.

2 x ECC82 and 4 x IRF820 mosfet.

 

[Jaimo]

DEQ Firmware

Edit - this applies to te DEQ 2496 and not the DCX...

When you switch to AK4396 on the stock board what follows the DAC's output before the connector? Just the 10uf caps? Thanks!

Also on another note since no one is responding on other threads... is there a 1.17 firmware?

I upgraded my Firmware to v1.4 last fall. This fixed issues relating to the way one runs the room correction function.

Here's a note from the Behringer website re firmware versions... be sure to verify your existing firmware version before doing any upgrade. Mess up the upgrade and you could have a DEQ for a doorstop!

Question
Do I need to update the firmware for my DEQ2496 ?
If yes, what equipment do I need, and how do I procede ?
Answer
First of all - please check which firmware version is currently installed in your DEQ2496.

Press "utilities" until the page "util 1" is displayed. In the top right corner of the display you will find the firmware version number.

If your DEQ2496 has V1.3 or lower, then you may want to upgrade to V1.4
If your DEQ2496 has V1.4 - then please do not update the firmware to V2.3.
There is no need to do this, and it will not work either (see below).
If your DEQ2496 has V2.0 or higher - then yes, you may want to perform the upgrade to V2.3.

Why are there two "current" versions of the firmware ?

This is because it was necessary for our engineers to make a slight change to the hardware. The older V1 units have a different CPU chip - one which is no longer available in production.
New CPU = new firmware.

Is the V2.3 better than the V1.4 ?

These two versions are exactly the same. There are no differences to the operation of the DEQ2496 and the audio performance is also identical.

What was fixed in V2.3 ?

This is a minor bugfix for earlier revisions of V2 - which affects the phase relationship between the input and output signals. V1 units are not affected.

What do I need to perform the update ?

The simplest way is to use a computer or laptop with a MIDI interface.
You will need a software which is capable of sending "System Exclusive" files. For Windows we recommend MIDI-Ox, for Mac OS-X we recommend SysEx Librarian.
Either software may be downlaoded from their respective publishers' websites :

MIDIOX
s n o i z e : SysEx Librarian

Make sure that your MIDI i/o device is connected and functioning correctly.
Check that the relevant MIDI ports are visible and selected in the software.

What settings do I need to make on the DEQ2496 ?

press "util" until the page Util 2 is displayed. This shows the MIDI settings.
Make sure of the following settings :

MIDI = on
MIDI channel = 1
receive sysex messages = on

WARNING ! - before you send the Sys Ex file to the DEQ2496 - please be absolutely sure that all connections - this means power connections and MIDI connections - these must not be interrupted during the upgrade.
An incomplete update may render your DEQ2496 useless !

Everything OK ? - then send the file fromthe software. The display of the DEQ2496 will show the status of the update. After the file transfer is complete, power cycle the DEQ2496 (turn off, wait, turn on again)
The new version number will now be displayed on the Util 1 page of the menu.

If you do not feel confident to perform the upgrade yourself, then you may wich to return the unit to a service centre for the update.
The service centre may charge a nominal labour fee for this service !

 

[yammy1688]

I'd be very interested in your comparison. Which transformers do you intend on using?

Hello Brett - the AK4396 is a direct replacement for the AK4393. I just spent the morning doing the necessary micro surgery and my initial impression is that this mod is only worth doing if you rework the PSU and fit an output transformer or change the op-amps.

The 4396 also appears to have a higher output level than the AK4393 - my DEQ now clips frequently when using the levels I had set up for the AK4393.

I plan to fit a transformer next and will write up my 4393 vs 4396 impressions soon.

 

[Jaimo]

Transformer Selection

I am hoping to get a pair of Bud Purvine designed transformers.

 

[Jaimo]

Interim DEQ AK4396 opamp solution...could become permanent!

I haven't secured a pair of quality transformers as yet and decided to hook up the following circuit to a AK4396 as an interim measure .....

..and the results are just wonderful!!! I will build a proper regulated PSU next but at this stage, this mod along with the AK4396 swap has done wonders for my DEQ.

I also tried a bypass capacitor as well as a "cheap and nasty" transformer and neither sounded anywhere as good as this circuit.

The DEQ output is connected to my ARC SP8 Tape input!

 

[yammy1688]

Hey all, I'm pretty new at this so bear with me here.

Wanted to share my little success story connecting a pair of ll1684's to my sound card that uses the ak4396 dac (b-enspirer), and replacing some of the caps in the process. Sounds fantastic! On par with my transporter, which I plan on moving the transformers to.

I do have a few questions and was hoping someone could help me out a bit.

The diagram kevin@k&k sent me called for a 40k resistor in parallel at the outputs, which I have not installed. Nor have I grouned the transformer or rca's , as I couldn't located the ground on the board.

Any potential pitfalls I may run into by not connecting the resistor or ground?

In case anyone else is interested, here's how I've got it hooked up.

Thanks,

-Ken

 

[Puffin]

I have a CS4397 based Dac, for which I am interested in adding output transformers. Can it be as simple as the diagram in Yammy's post or is it as complicated as the output stage by audiodesign?

I have a very small brain.