Behringer DCX2496 digital X-over

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Legis. Change the opamps if you like. It could be a fun project and might lower the hiss. May even sound better, I have not tried it, so I don't know.

But get your gain structure right and it WILL reduce the hiss. By as much as 20dB, maybe more. You just need some kind of attenuation between the DCX and the amps. Simple.

Don't put the cart before the horse. Get the gain right first, then do the mods if you need to or want to.
 
Legis. ..
...get your gain structure right and it WILL reduce the hiss. By as much as 20dB, maybe more. You just need some kind of attenuation between the DCX and the amps. .....
..... Get the gain right first,...
I used between 20 and 30dB of attenuation between the DCX and the Power Amplifiers. The bass and treble drivers could not be heard emitting any noise with the CD player in standby mode.

Without the outboard attenuation and with the full 15dB of on board attenuation, I could clearly hear hiss at ~ 300mm.
 
Legis...

The source of your problem is fairly simple. What you are trying to do is simply not possible with DCX. When I tried DCX for the first time many years ago, I did the same logical mistake, just as you. I was happy camper thinking, why do I need 6 channel output volume control after DCX? I will just go with analog Preamp in front of DCX and that is where I will attenuate signal. The result and hiss was so bad, that I went back to the store to exchange for the different unit. The result was the same, obviously, unbearable hiss.

What you are trying to do is not possible and not good. Forget about analog attenuation in front of DCX and forget about your preamp. Here is the simple test for you. Set up DCX as a simple two channel DAC. No xover, no EQ, just plain full range out. Plug in digital signal to DCX. Do not attenuate outputs on DCX, keep them at 0 dB. On the output, between DCX and amp place pot, let say 100K. Use any speakers that are with passive crossovers so that you could safely run this test. Listen - no hiss.
The result of this will tell you that the source of your hiss is attenuated analog signal at the input. If you are really stuck and has to go with analog signal in, than that signal has to be at full volume, but obviously not to clip input. Analog in is OK, but why you would do that. You are introducing DA (in your CD player) and AD and than DA conversion. Instead just one DA conversion with digital in. Analog input in my mind would make only sense if you are using turntable, tape player or any other analog source. Performing triple digital conversion versus one simply is inferior and less optimal to digital in.

Next, optimizing gain in your amps will further improve your system and enhance the whole experience. Doing all of the mods mentioned will not solve your problem if you are trying to do the same, attenuate the input signal and by digital pots provided in DCX. The most optimal sound that you will get is if you give a full digital in, 0 or few less dB at the input and 6 (or 4) channel analog attenuation at the output.

Now word on mods and kits. Once you realize that you will need 6 channel analog attenuation, than you will see that are not that easy to find and are expensive solutions. That has to have housing, than add any other mods to the opamps, output boards... It easily overcomes the price of DCX itself and is not that easy to find, execute properly... In my mind Jan Diden's solution is the most elegant solution out there. It solves the input and output circuitry, it gives you remote volume for each channel plus global volume control, plus fits in the DCX case. You simply cannot go wrong about it, and in a short time you will be able to enjoy your DCX, unlike what you are going through now.

Hope this helps,
Good luck
 
I agree to 99,99% too.

The last 0,01% I'd like to point out - just for *my fun* on contrasting and to "trigger interest for some learning fun" for the novice' here.

There *is* good reason to drive stock unit with analog-IN - actually two.

- first you can use volume control of your preamp which may be convenient for one reason or another. I do not totally agree this is a bad thing to do ! - *if* signal to noise (what goes under "gain structure" here) of your chain is optimized first of course. I have done so and IMO it even can outperform the digital-IN (I have posted the reasons and what to do somewhere way back – fun to look up and check out by yourself!)
- second if you go with attenuation *in front* of the DCX there is a small benefit in that you usually do not "hit the ceiling" easily. What I mean with this is that optimizing for S/N is – to some degree – contradictorily to optimising harmonics and intermodulation distortion. (I know people will come along with "loss of resolution" story – but actually this story isn't the full truth either)

So I hope having given some hot arguments to not "just do mod's out of fun" but to take the challenge to "just read and learn about why actually doing something" which is a loooooot of fun in the long run too.....
:)

Keep swingin'
 
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I looked at the article about the broken samplerate converter issue reported earlier.
However I never understood exactly what cases where affected and to what degree. I found the article to be semantically contradicting as I understood it.

What samplerates and bitdepths will most likely trigger the problem and which will leave it alone?
 
Very well put, AR2. Thanks!

I agree to 99,99% too.

The last 0,01% I'd like to point out - just for *my fun* on contrasting and to "trigger interest for some learning fun" for the novice' here.

There *is* good reason to drive stock unit with analog-IN - actually two.

- first you can use volume control of your preamp which may be convenient for one reason or another. I do not totally agree this is a bad thing to do ! - *if* signal to noise (what goes under "gain structure" here) of your chain is optimized first of course. I have done so and IMO it even can outperform the digital-IN (I have posted the reasons and what to do somewhere way back – fun to look up and check out by yourself!)
- second if you go with attenuation *in front* of the DCX there is a small benefit in that you usually do not "hit the ceiling" easily. What I mean with this is that optimizing for S/N is – to some degree – contradictorily to optimising harmonics and intermodulation distortion. (I know people will come along with "loss of resolution" story – but actually this story isn't the full truth either)

So I hope having given some hot arguments to not "just do mod's out of fun" but to take the challenge to "just read and learn about why actually doing something" which is a loooooot of fun in the long run too.....
:)

Keep swingin'

I love when my post stirs up positive and happy response, and inspire you guys to elevate conversation to the next level!

Stay well
:)
 
I might as well throw in my 2*bits. Yep, the first effort to make is getting the gain structure correct. Most systems have way too much gain which compromises every thing else.

That is actually the main idea behind Nelson's F amps. Why provide so much gain if it is not used. If preamp provides as much gain and amp even more, that that, in many cases, is already way too much.
 
Maybe it's because the dumb (inefficient) speakers people are using. So the power requirement keeps growing, and inevitably the voltage gain must be larger to get that output.

In my system, there're only 2 (tube) gain stages from DAC chip to speaker (for the range above 200Hz or so). Like pano just mentioned, it's very clean (along with superb details and intimacy). High sensitivity of the speakers helps a lot here.
 
My first speakers - tweet ribbons use to be 100 dB and PHL mids 101 dB. Going straight from DACs to Lundahls... oh, soooo gooood. 2A3 tubes for mids, small Aleph 30 Class A on ribbons.... What else to say, a dream comes through... What is nice with this minimalistic set up I was able to hear every nuance, transparency to cry for. :yummy:
 
Yes they do! And I've never been sure why. Maybe a "just in case".

When I started use low gain systems, I started liking the sound better. At least it was cleaner. ;)

As a small data point, all 4 amps that get switched in and out of my system have gains of ~17dB as apposed to the quasi standard of 26dB or more. The local feedback tube amps, the 47, and the Tabor were happiest in that range, the gain of the SS Tabor was reduced to match the tube amps to make swapping easier. The Crown Comtech 800 used for subs has input controls that I set to match the other amps.

In short, you should be able to peg the volume control to max on normally recorded material and not clip or just clip the amps.
 
These programs are excellent for PC machines. As for relatively new kid on the block, measurement systems for MAC OSX, I would gladly recommend Faberacoustical - Electroacoustics Toolbox. Very good app. I am a Mac user, that started using PC just because of audio measurement, and finally there is a good measurement app for Macs as well. They have even apps for iPhone. Very stable app with calibration for input and output...