DCX Fried???
I have been doing some mods on my DCX2496. This is the digital input and clock change from Frank Oettle. At this point I have removed the digital input/sample rate converter chip and disabled the crystal oscillator. I just tried to power up as is and the LCD display just goes blank or sometimes random stuff. I'm sure all the cabling is OK. This is with no new input board attached yet.
Have I already hurt something or is the 24MHz clock needed.
I have been doing some mods on my DCX2496. This is the digital input and clock change from Frank Oettle. At this point I have removed the digital input/sample rate converter chip and disabled the crystal oscillator. I just tried to power up as is and the LCD display just goes blank or sometimes random stuff. I'm sure all the cabling is OK. This is with no new input board attached yet.
Have I already hurt something or is the 24MHz clock needed.
Can't see anything wrong with the circuit as such but the resistor values are not optimal.
On the input side, you have those 300 ohms loading the DACs. That's much too heavy; I think the datasheet says min 1k or so.
Then on the output side there's some 10k's; I'd think that's too high. The OPA can easily drive a few 100 ohms and you want low impedance to drive the output cable and its capacitances and keep low impedance to limit interference etc.
jan didden
@Jan Thanks so much for your reply. So, change R input to 1K. May change R feedback to have some gain like 2+.
On the output side, I would like to do volume control with LDR that is why I put 10K there and 10K variable resistor is my LDR. I can lower them to 5K but lower them less than 3K would be tricky. If I use 5K and drive cable with no more than 3 meter long, will there be problem.
I get confuse with akm4393 datasheet, is there dc at the output of this DAC?
On the output side, I would like to do volume control with LDR that is why I put 10K there and 10K variable resistor is my LDR. I can lower them to 5K but lower them less than 3K would be tricky. If I use 5K and drive cable with no more than 3 meter long, will there be problem.
I get confuse with akm4393 datasheet, is there dc at the output of this DAC?
All DACs with +5V (unipolar) analog supply always have DC at the output, otherwise they can't give out ac signals.
Generally the 'zero signal' level at these outputs is half the supply, 2.5V. Each output swings around this 2.5V, up to the supply and down to ground, so about 2.4V peak or 2.4*0.7 or less than 1.7V RMS.
BUT because there is 2.5V on each balanced output, if you put it into a difference circuit like the OPA1632 there will be NO output DC because the difference between 2.5VDC and 2.5VDC is, errr, zero.
The only thing left to do now is to make sure that the two OPA1632 outputs are nicely around zero so you can chuck the output coupling cap(s). Those smart engineers who designed the OPA1632 foresaw that you would want that and provided an 'output common mode pin'. The DC output will be whatever you connect that OCM pin to. Just ground it and both outputs sit at ground with zero signal.
Neat huh?
jan didden
DCX2496 digital input seems dead
I've had a DCX2496 in a triamp setup for about 2 years, with no problems. Thinking myself clever, I sold my Musical Fidelity CD player, and bought an E-mu soundcard with an AES/EBU digital out. But no amount of fiddling has caused the DCX to show in any way that its reading the digital signal, despite telling it to use AES for A and B in.
In frustration, I bought a DVD player and tried running the digital coax via a 10 inch cable - no luck at all. Ive searched all over this forum for a similar problem, but I cant find anything. Has anybody had any similar problems getting the digital input to work? At what point should I head to the nearest authorized repair depot?
I've had a DCX2496 in a triamp setup for about 2 years, with no problems. Thinking myself clever, I sold my Musical Fidelity CD player, and bought an E-mu soundcard with an AES/EBU digital out. But no amount of fiddling has caused the DCX to show in any way that its reading the digital signal, despite telling it to use AES for A and B in.
In frustration, I bought a DVD player and tried running the digital coax via a 10 inch cable - no luck at all. Ive searched all over this forum for a similar problem, but I cant find anything. Has anybody had any similar problems getting the digital input to work? At what point should I head to the nearest authorized repair depot?
I need a little definition help.
I believe the DCX2496 increases the Hiss I hear in my ribbons or compression drivers. Others have simply said its nothing to do with the DCX and its my gain structure. I get the gain structure can be controlled with a amp/gain control but I have one setup that has outlaw amps with no gain controls so the gain structure is what it is, its static.
When I add the DCX I get about a +6dB gain in the "Hiss" I hear when no content is playing so the DCX 100% does something. I know this is a common opinion with the DCX but I lacking the right information to set things right against some very aggressive individuals on the topic.
A great explanation of what is happening here would help me a great deal and putting this debate to bed.
Thanks!
I believe the DCX2496 increases the Hiss I hear in my ribbons or compression drivers. Others have simply said its nothing to do with the DCX and its my gain structure. I get the gain structure can be controlled with a amp/gain control but I have one setup that has outlaw amps with no gain controls so the gain structure is what it is, its static.
When I add the DCX I get about a +6dB gain in the "Hiss" I hear when no content is playing so the DCX 100% does something. I know this is a common opinion with the DCX but I lacking the right information to set things right against some very aggressive individuals on the topic.
A great explanation of what is happening here would help me a great deal and putting this debate to bed.
Thanks!
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the DCX puts a lot of gain between input and output. With that gain comes added noise. It is designed for PA line levels, not normal domestic systems.
If you remove the extra gain stages at the output, you will reduce the gain and reduce much of the added noise.
Alternatively, you can add an attenuator between the DCX outputs and the amplifiers. This reduces the signal level and with it the noise. This adds a tiny bit of noise due to the resistances in the attenuator, but it can be ignored at our signal levels.
Basically I am confirming that in a domestic system you probably have too much gain built in and you are attenuating the signals in the wrong place, such that you does not reduce the noise pro rata with the signal level.
If you remove the extra gain stages at the output, you will reduce the gain and reduce much of the added noise.
Alternatively, you can add an attenuator between the DCX outputs and the amplifiers. This reduces the signal level and with it the noise. This adds a tiny bit of noise due to the resistances in the attenuator, but it can be ignored at our signal levels.
Basically I am confirming that in a domestic system you probably have too much gain built in and you are attenuating the signals in the wrong place, such that you does not reduce the noise pro rata with the signal level.
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Its not the "frying bacon" stuff, I had one with that and sent it back.
This is simply a normal hiss with very high sensitivity tweeters when using amps without gains on them. The hiss in the tweeter exists when connected alone to the amp and if I add the DCX into that chain, the hiss is increased by 6dB. My goal is to get the exact explantion down so that when the debate rages on I can post the exact details.
This is simply a normal hiss with very high sensitivity tweeters when using amps without gains on them. The hiss in the tweeter exists when connected alone to the amp and if I add the DCX into that chain, the hiss is increased by 6dB. My goal is to get the exact explantion down so that when the debate rages on I can post the exact details.
Yes, That is what Im looking for but is there some real tech stuff or specs on the gain the DCX adds.
Your post is more or less what I have posted in the past or alteast what I thought I have always posted so thank you for atleast confirming what I believe.
I also 100% agree with the gain structure of the comercial system (or lack of one) as an issue but my main point was that the DCX will 'ADD' to that setup if inserted in the mix. Others fired off the same dumb ** "Its your issue not the DCX".....
I can understand the sentiment.
Where are you attenuating the signal to give listen-able SPL at your seat?
The one setups is PS3 -> OUTLAW 970 -> DCX2496 -> Outlaw amps. Its been fine for a couple of years. soon it will be replaced by the MiniDSP but I was doing comparisons and I explained that that Pro nature of the DCX had issues and one of them was the hot outputs and how they increased the hiss of my Ribbons (Easy to hear and measure that hiss diference in dB so its not subjective).
My HT setup is the Onkyo 885 -> DCX2496 -> collection of pro amps with gain controls.
Im not debating the issue of gain control at all, I fully understand the compromises that come with that issue.