Behringer DCX2496 digital X-over

Pulse-R said:
I have used the Behringer units with analog in/out without too much trouble, and when the sound is quiet, then your ears have less resolution also, so it's not a big deal.

The purists like everything perfect, but in a less than perfect world, the analo in and out will work just fine.


That's what I kind of figured, but didn't want to say anything. Thanks.
 
DCX with 7.1 surround. Options..

I'm not up to speed in the newest digital formats and possible setups but i would like to add a 7.1 surround setup with my DCX.
I would like to keep all sound in the digital domain.

I was thinking to iether get a good performance 7.1 reciever and utilise the amp for all channels exept L+R mains

Now the problem is how do i give the DCX a digital feed if the signal must pass through the 7.1 reciever first. Some models have digital out but what signal is this exactly, unmodified ? multiplex or stereo ? How does the DCX handle different formats, it only extracts L+R ?
I dont have it running at the moment so cant test this.

Are there other possibilities?

Collin

PS: I'm planning to replace the AK4393 DAC with a AK4395 which has DVD audio capability (192/24) . An average reciever might not pass the full bandwith ?
 
I've thrown together (well, not exactly thrown, I've done it pretty carefully) an IO board with six output stages from the 4393 datasheet, three input stages as shown by Oettle, and a bit of power conditioning. It a bit shy of a 100x80mm board. I've made room for the huge MKP1837 decoupling caps, but the first cap on the output stage might be a little cramped if you go for standard values.

The point of the board is that it'll have all components on top, but pin header sockets soldered underneath so it slides straight into the ribbon cable sockets on the DSP board without any cables. The input circuits need DC caps ahead of them, and if necessary, the separate mic circuit. Mic relay signal and relay power is easily tapped from the right hand header.

Comments and tips are very much appreciated, as I have noe experience or training in board design, I just set it up so it looks more or less logical and tidy.

ZIP with board and schematics here
 

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I have, and he has a great volume control/output board project, but I just need simple outputs. I also need the inputs because I have the same "problem" chops has, that I have a receiver with an already volume controlled pre out. I will improve on that later, but that won't be before I get my digital amps up and running, which is still quite some months away.
 
Hi all.
I've read this thread for quite a while and learned a lot. Thank you very much for all that.

I run the dcx2496 quite a while with analog input. I enjoyed zhe various features - and put the dcx away eventually for the simple reason that I liked it very much only at high input levels. At low input level, the reduced number of bits in use can be clearly heard, I think.

My current conclusion: analog-digital-analog has more issues than a passive crossover (2-way speaker); I'll wait for digital radio (still using fm) etc...

Just a hint.

Ulli
 
Hi Ulli,

Isn’t it already there digital radio via e.g. Astra?

My experience over the last years is that I would clearly prefer digital crossover compared to passive crossover regarding sound quality and flexibility. How e.g. do you realize a LR-48 filter or how do you delay a tweeter with a passive crossover? Optimizing a crossover and to get a real flat frequency response takes a few mouse clicks. Have you ever designed a passive 3-way crossover? It would take days with a much worse result.
I also prefer multi-amping regarding sound quality which also gives you the freedom to use drivers with different sensitivity what is a clear advantage especially at the low end (20Hz).

To get maximum sound quality from a digital crossover it's necessary to use digital input and to have volume control after the DACs (otherwise you reduce resolution). Using DCX my experience is its worth improving analog outputs, SRC and clock.

Frank
 
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modmix said:
[snip]I run the dcx2496 quite a while with analog input. I enjoyed zhe various features - and put the dcx away eventually for the simple reason that I liked it very much only at high input levels. At low input level, the reduced number of bits in use can beclearly heard I think [snip]
Ulli

Ulli, I agree with you. In using the analog input, you go from D to A (in your source, assuming you have a CD/BVB source) then A to D in the DCX inputs, then D to A at the DCX outputs. It would be surprising if that didn't leave a mark!

Why don't you run it with digital inputs? And if you have an analog means to set your level in your power amps, even a simple pot to set it one time, you can run the DCX at 0dB levels overall, and most of the things you mention would go away.

Jan Didden
 
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novec said:
Oettle; When feeding single ended signal into the analog inputs you suggested, doesn't that effectively cut resolution in half? Would it be possible to reverse polarity on one of the opamps and have it convert the single ended signal into balanced?


Going in single-ended, you can just increase the signal in that case, watching the input level LEDs. But also in the balanced input case, you always have to adjust the analog input level for best/max resolution, i.e. a few dB below clipping.

Jan Didden
 
Hi Novec,

You are right input voltage is doubled using balanced input. But I think there is also a difference between professional and home equipment regarding level? So you have to make a decision whats your favorite input level and have to adjust R8 (gain setting) accordingly. The original DCX input has the same problem. If you want to use different input levels I only see the solution to have different R8 values and to select between them via a switch or a relay. Life is not perfect but it becomes easier with digital input.

Regarding your proposed schematic:
1. I couldn't see the AC coupling caps for the inputs.
2. I would use small COG type (~1nF) and for the +/-15V rails X7R type (100nF) caps. I can't see any benefit coming from the proposed MKT type caps.
3. There should be two caps per opamp referring to GND!
4. The +/-15 supplies could be improved by two simple coils or better by two regulators which generate e.g. a +/-12 volt output from the +/-15V rails (see my Vreg schematic a few posts before).

Frank
 
Jan: Doesn't the ADC take half the bits from the positive input and half from the negative? Or does it just take the difference between them, even if the negative is grounded, so I'll get a full resolution digital even with a single ended input?

Frank: I just want to have the highest possible input resolution at my relatively low analog input level, but all inputs can stay at the same gain. Once the digital amps go online, they'll do the crossover functions for the fronts, and I'll molest a cheap receiver to feed the Behringer directly through I2S for center and surrounds. With some luck that'll only take a few months, which is why I won't put too much effort into the analog section this time.

Over to your comments:
1. I'll keep the AC caps offboard, I have some big Mundorf RXF caps I'll stick in the open space to the left of the DSP board.
2. COG and X7R? Afraid I'm not with you there. I figured nice MKT caps would be good both in the signal path and for decoupling, but maybe they won't make much of a difference. If not, cheaper and smaller is definitely better.
3. D'oh! Just my brain stuck in neutral again...
4. You're undoubtedly right, the onboard power supply isn't the best, but I was trying to make it cheap and simple. I've got just about all the other parts I need. If I can free up some board space by using other caps, it might still be an option.
 
Originally posted by novec
4. You're undoubtedly right, the onboard power supply isn't the best, but I was trying to make it cheap and simple. I've got just about all the other parts I need. If I can free up some board space by using other caps, it might still be an option.


And a PSU need space. ;)

An externally hosted image should be here but it was not working when we last tested it.


Need to have some new 7805 like in place of originals too.

.
 
I'm not sure why, but good MKP caps are supposed to make a big differencefor proper power supply decoupling of opamps and other chips. A friend of mine, who is an electronics professor, prefers a good 100nF film cap and a ~10uF electrolytic for power decoupling, but often adds a 100nF ceramic as close to the power pins as possible.

High quality caps in the signal path is well known to have positive effects, that's pretty much like choosing good caps for passive crossovers.
 
Regarding the bias for the input circuits; does it really need an opamp? Both the circuits in the AK5393 datasheet and in the Behringer schematics use a passive bias with just a couple of caps and resistors.

Is there any way to simply eliminate one of the input opamps and short the negative inut to ground or bias? If not, I think I'll go for inverting one of them to make a full-level differential out of the single ended input. I'll also replace R8 with a trim pot.
 
DCX2496. Tranformer out with Sowter 9545. A good idea??

DCX 2496-analog stage, the week part of this unit.

After reading this site, this is my conclusion.

I look into two possibilities for better sound quality:

1.Go for Jan Diddens very smart solution. I have already bought this unit, but before I start to build I do hope that some one with experience with transformer could give me some adwise on this idea:

2.Take the signal directly and balanced from the DAC into a Sowter 9545 transformer (ratio 1+1:5+5). (http://www.sowter.co.uk/acatalog/SOWTER_OUTPUT_TRANSFORMERS_12.html#a282)

Why? I have very good experience with this transformer in my Copland 288 CD player. I take the signal directly from PCM 63. On the other side of 9545 the signal go to Lampizator, a SSRP stage with the exellent 6N6P. Sound is superband ver y much into my taste, (http://www.lampizator.eu/LAMPIZATOR/whytubes/whytubes.html)

Since I go for a 3-way speaker, I realize that I will need another 4x9545 and 6 Lmpizator stages. Exspensive, but if it is possible to realize, I will
consider this “against” Jan Diddens analog stage.

Two other things must be possible to realize before I take my final decision.

Main volume: I have found that this one will be suitable:
http://www.diy-selbstbau.de/

With 10 kohm in and 600 okm out, can I put this unit (4-channel) before four of the tube stages without audible problems(impedance)??
To compensate for different sensivety I want to go for this after the six
Lampizator stages (Broskies attenuator):
http://store1.yimg.com/I/glass-ware_1975_2011629

Today I use a 100 Kohm version after my Lamizator stage in Copland 288 to regulate for headphone listening. With two of this attenuator I can compesate for two different power amplifiers in each channel.


Power amlifier are: Woofer: NAD 208.Upper bass :The End 3.1 (danish DIY) and middel/upper: Music Angel 845 (also modded with a Lampizator input stage)

Then we will have this signal path:

Balanced from DAC>Sowter 9545>unbalanced to main volume> Lamizator>Broskies attenuator>power amplifiers

By the way I am also working on a new power unit for my DCX 2496

http://www.awdiy.com/index.php?page=deq-psu-project.

Since I do not have any theoretical backgroud, but have a background as DIY er for many years, I do hope for for comments from the many exspert on this site.

Regard

Eivind Stillingen, NORWAY