Behringer DCX2496 digital X-over

AndrewT said:
Hi,
what is the clipping indicator telling us when a digital input is fed into DCX?

Is it telling us that the digital signal is above the most significant bit (MSB)?

or

Is it telling us that the voltage level of the incoming digital signal is too high to allow the circuits to decode the digital information.

Since the DCX is designed to accept an AES level signal, I cannot see how an SPDIF signal could cause voltage overload.

It seems that the indicator is more likely telling us that the digital info is above MSB.

There is another old thread talking about digital clipping of signal coming off CD. Could this be a clue to what is happening?

If the DCX2496 input "CLIP" red LED lights up, it does not mean clipping if the input is digital. It means 0dB.

For example, if I play a 1kHz test tone sine wave recorded at 0dB peak level, into the DCX digital input, the red LED lights up. Nothing is clipping. If I drop the level to -0,5dB, the red LED goes out.

If the red LED is flashing a lot while you play a CD, the CD is probably recorded with a lot of overload. This could be deliberate for effect, or it could be poor recording technique.

If the red LED just occasionally flashes on music, I would not be concerned, it is just the digital signal reaching 0dB on maximum peaks, which is good recording technique. Even though the label on the LED says "CLIP", it means "0dB or CLIP".

If you are using analog input to the DCX2496, turn down the level so the red LED never lights, or only a very occasional flicker.
 
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nowater said:
[snip]If the red LED just occasionally flashes on music, I would not be concerned, it is just the digital signal reaching 0dB on maximum peaks, which is good recording technique. Even though the label on the LED says "CLIP", it means "0dB or CLIP".

If you are using analog input to the DCX2496, turn down the level so the red LED never lights, or only a very occasional flicker.



I agree. Except maybe that when the "0dB" lights, I wouldn't think it "just" reaches 0dB. It's impossible for the record engineer to keep it on "just 0dB", he cannot predict record level. So, if the led lights up, you can safely assume it IS clipping.

Jan Didden
 
With valve output stages?

I haven't yet sourced the article in Aug's AudioXpress, so am somewhat in the dark . . are the boards at Roger Pilgham's site, variations of output stages?

Some (all?) Aikido linestage circuits can be used as output stages on DACs, changing just one tube. I have spare PCBs from Bas's Aikido linestage group buy, and thinking of using them on the DCX . .

Any thoughts on how Jan's output boards might compare with Bas's Aikido valve output stages??


Thanks
 
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Ryssen said:

Yes

Don´t know if it´s better or not,but you get some kind of protection for the DAC´s anyway.I was thinking of going DC coupled,(have not inserted it in the DCX yet)was hoping someone could coment on this?:rolleyes:


If you go DC coupled, there are two issues:

- Be ABSOLUTELY sure that whatever you connect on the external side, preamp, level control, power amp, can take about 2.5VDC. It can when it itself is AC coupled; in that case you save the cost of the DCX coupling caps and have better lf response because you don't have two caps in series;

- The mute kit that I designed depends on AC coupling. I can't say for sure that it will or will not work (i.e. no turn-on/off thumps) when you go DC coupled because that depends on whatever is connected to it. Assume it doesn't work correct, forget the mute kit and make sure you power the preamp/power amp up after the DCX and off before the DCX. (Or, as I do, just leave the DCX on all the time).

Jan Didden
 
Ryssen
> all six output stages :up:

to find out exactly what the passive board does (inc the output of the dcx as standard, and with the passive board . . )

Jan
There are only a dozen odd words on Ward's site -
could the board details or article be reproduced for people here, or is it AX copyright?

Thanks
 
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rick57 said:
Ryssen
> all six output stages :up:

to find out exactly what the passive board does (inc the output of the dcx as standard, and with the passive board . . )

Jan
There are only a dozen odd words on Ward's site -
could the board details or article be reproduced for people here, or is it AX copyright?

Thanks

Yes it is (c) AX, and i really don't want to mess with this since I have a good relation to them and want to keep that. However, they will sell you the back issue or article copy, I think $ 5 including postage, so that would be worth it.

Jan Didden
 
Just spoke with Behringer USA, and only a few units got out so far, to selected dealers.

They are starting to creep their way back into the system, and many more should be available soon. Meaning..the DCX SHOULD, repeat..SHOULD..be a regular stock item again soon, as they ARE actually being manufactured again. This, Directly from Behringer, not 2 minutes ago.
 
janneman said:



If you go DC coupled, there are two issues:

- Be ABSOLUTELY sure that whatever you connect on the external side, preamp, level control, power amp, can take about 2.5VDC. It can when it itself is AC coupled; in that case you save the cost of the DCX coupling caps and have better lf response because you don't have two caps in series;

- The mute kit that I designed depends on AC coupling. I can't say for sure that it will or will not work (i.e. no turn-on/off thumps) when you go DC coupled because that depends on whatever is connected to it. Assume it doesn't work correct, forget the mute kit and make sure you power the preamp/power amp up after the DCX and off before the DCX. (Or, as I do, just leave the DCX on all the time).

Jan Didden

Hi Jan,
Why there is a need for mute kit? In my DCX mod I disabled everything after DACs and my signal goes straight to Lundahls and than further to volume control and preamps. With that my original mute control from DCX still works. So to make it clear - all preamps, caps and resistors after DACs are disabled. I am assuming mute control is ether part of DAC or DSP. Please let me know what do you think.
 
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AR2 said:


Hi Jan,
Why there is a need for mute kit? In my DCX mod I disabled everything after DACs and my signal goes straight to Lundahls and than further to volume control and preamps. With that my original mute control from DCX still works. So to make it clear - all preamps, caps and resistors after DACs are disabled. I am assuming mute control is ether part of DAC or DSP. Please let me know what do you think.


There are two mute systems actually. The mute you refer to is the one driven by the DSP when it boots, and prevents the SIGNAL from appearing until the DSP has things under control.

The mute I refer to is the mute transistor in the schematic of the output circuit. This mutes the output at switch-on/off to prevent pops, clicks and other potential turn on/off transients to get to the amp. It is this last system that I replaced with the relays on my board.

This is not easy to do because of the balanced nature of the outputs and the 2.5VDC bias of the outputs. Behringer went as far as first making the signal from balanced to single ended, then do the mute, the re-convert the signal from single ended to balanced. This means a lot of active circuitry just to get the mute right. So, because I wanted to go pasive out, I had to really think hard on the muting to get it a) right and b) non-intrusive, and I believe I succeeded.

BUT as said before if you go DC coupled it probably is not perfect for blocking the turn on/off transients so in that case it may be better to turn the DCX on before the amp and off after the amp and not use the mute kit.


Jan Didden