In a thread on Class D amps I mentioned that I was planning to use two MiniDSPs 2x8 to allow active crossovers. This will be for our Klipschorns Left and Right and LaScala clone Center that I am converting to 2 way. Also for EQ and HPF for our Danley DTS-10 sub The MiniDSP 2 x 8s will be very expensive and since I already have a DCX2496 Jack suggested I use it with some mods.
I thought this discussion would be more on topic in this forum section, thus this new topic( hope you don't mind Jack). Here was his last post to me:
So Jack thank you again for all your good suggestions. The output mod sounds simple enough. I have long heard that the DCX is excellent for sub duties, but not very good for full range use. What I'm getting from you is that by eliminating the output op amps the worst of the SQ problems with the DCX are eliminated. Sounds great!
Some time back I bought some boards from William DiPoala to do mods on the DCX but haven't used them. I believe they would make some excellent improvements but after getting them realized I would be soldering SMDs. Thirty years ago I would not have hesitated, but now that I'm 2 months from being 70 my thumbs seem to have gotten huge and my eyesight is a long way from being what it used to. So these boards have just sat and when the MiniDSPs became available I thought they might be a good way to go.
Since I already have a DCX2496 here's what I'm now thinking.
1. Do the output mods to my DCX as Jack suggested which will eliminate the Behringer op amps.
2. Use the DCX 3 inputs for L,C & R. This will use all 6 outputs for our two ways.
3. Buy a MiniDSP 2 x 4 in a box for our sub EQ and HPF.
If this works it will save a lot of money over two MiniDSP 2 x 8s, as well as the work of putting them in cases.
Any other thoughts on this approach will be greatly appreciated.
Thanks,
Rod
I thought this discussion would be more on topic in this forum section, thus this new topic( hope you don't mind Jack). Here was his last post to me:
So Jack thank you again for all your good suggestions. The output mod sounds simple enough. I have long heard that the DCX is excellent for sub duties, but not very good for full range use. What I'm getting from you is that by eliminating the output op amps the worst of the SQ problems with the DCX are eliminated. Sounds great!
Some time back I bought some boards from William DiPoala to do mods on the DCX but haven't used them. I believe they would make some excellent improvements but after getting them realized I would be soldering SMDs. Thirty years ago I would not have hesitated, but now that I'm 2 months from being 70 my thumbs seem to have gotten huge and my eyesight is a long way from being what it used to. So these boards have just sat and when the MiniDSPs became available I thought they might be a good way to go.
Since I already have a DCX2496 here's what I'm now thinking.
1. Do the output mods to my DCX as Jack suggested which will eliminate the Behringer op amps.
2. Use the DCX 3 inputs for L,C & R. This will use all 6 outputs for our two ways.
3. Buy a MiniDSP 2 x 4 in a box for our sub EQ and HPF.
If this works it will save a lot of money over two MiniDSP 2 x 8s, as well as the work of putting them in cases.
Any other thoughts on this approach will be greatly appreciated.
Thanks,
Rod
Having modded DCX's both passive and active, I can tell you that you don't have to trace and fly wires etc. All connections are brought out directly to the connector for the cable that goes from the DSP board to the analog out board. Unplug that cable, put in your own cable and presto! Pin numbers on plugs and schematics can be found on the Yahoo DCX forum.
Anyway, I don't understand why you want to use miniDSP WITH the DCX? The DCX already has a capable DSP and the user interface is really neat.
jan didden
Anyway, I don't understand why you want to use miniDSP WITH the DCX? The DCX already has a capable DSP and the user interface is really neat.
jan didden
Wow what a fast response! Thanks very much jan.
With all three inputs, and six outputs being used for my L, C & R, the DCX can't handle the sub. Thus the MiniDSP. And in a case the 2x4 is only $150.
My source all comes from a HTPC with a Asus Essence ST & H6 daughter board sound card. I'm using it in a 5.1 system. The plan is that the the L, C & R outputs will go to the DCX. The LFE (sub) output will go to the MiniDSP. The outputs from the DCX will go to individual Class D amps (probably HiFiMeDIY T1s or T2s) and the Mini DSP sub output will go to my existing Behringer EP4000 amp.
So jan your way of bypassing the output op amps sounds easy. I will look things up on the Yahoo DCX Forum.
Re the DCX user interface, I find the computer software easy to use, but the DCX front panel feels very unintuitive to me. Guess I have some kind of block there.
Thanks again for your help.
Cheers,
Rod
With all three inputs, and six outputs being used for my L, C & R, the DCX can't handle the sub. Thus the MiniDSP. And in a case the 2x4 is only $150.
My source all comes from a HTPC with a Asus Essence ST & H6 daughter board sound card. I'm using it in a 5.1 system. The plan is that the the L, C & R outputs will go to the DCX. The LFE (sub) output will go to the MiniDSP. The outputs from the DCX will go to individual Class D amps (probably HiFiMeDIY T1s or T2s) and the Mini DSP sub output will go to my existing Behringer EP4000 amp.
So jan your way of bypassing the output op amps sounds easy. I will look things up on the Yahoo DCX Forum.
Re the DCX user interface, I find the computer software easy to use, but the DCX front panel feels very unintuitive to me. Guess I have some kind of block there.
Thanks again for your help.
Cheers,
Rod
Yahoo DCX forum
Hi Jan, thanks for the heads up. In the case of the DEQ2496 I've wanted to keep the functionality the same as the stock unit, except for the analog outputs.... so, for the simplest mods I've preferred to run the flying leads rather than disconnecting the ribbon.
I'm taking the same approach on the DCX as in the case of the simplest mods I would not want to lose the digital input and other connectivity and pulling the ribbon connectors would have that effect, wouldn't it?
For a more ambitious mod then yes, replace the connectors board and upgrade the PS and the clock and so on, but that's a lot more involved and costly.
BTW, I'd really like to look at the YahooDCX forum you referred to, but for some reason am having trouble finding it!... would you post a link to it?
Thanks for your great contributions to these forums!
Hi Jan, thanks for the heads up. In the case of the DEQ2496 I've wanted to keep the functionality the same as the stock unit, except for the analog outputs.... so, for the simplest mods I've preferred to run the flying leads rather than disconnecting the ribbon.
I'm taking the same approach on the DCX as in the case of the simplest mods I would not want to lose the digital input and other connectivity and pulling the ribbon connectors would have that effect, wouldn't it?
For a more ambitious mod then yes, replace the connectors board and upgrade the PS and the clock and so on, but that's a lot more involved and costly.
BTW, I'd really like to look at the YahooDCX forum you referred to, but for some reason am having trouble finding it!... would you post a link to it?
Thanks for your great contributions to these forums!
I'm probably missing something, but to me L, R & C are three output channels....?
Edit: got it, you're going 2-way active.
jan
Here's the link to the Yahoo Group. Haven't looked through it yet, but wanted to get this link here first.
Cheers,
Rod
I spent some time on the Yahoo board looking at DCX2496 mods. Jan Didden has done a lot there including extensive articles.
At this point I'm into keeping it as simple as possible. I would like to try just bypassing all the output junk and just go straight from the DAC to RCA single ended.
Jans approach apparently does some high freq (20k and above?) filtering while others don't seem to think this is necessary.
So it looks like the very simplest is to somehow disconnect the output from the DAC to the rest of the stuff and connect it to a coupling cap. Use the sig gnd on the XLR output connectors as the new RCA sig gnd.
This all brings up a few questions:
1. What's the best way to get to the DAC output?
A. Cut the ribbon cable and tack onto the ends that go to the DAC?
B. Make and install a new ribbon cable?
1) Does this eliminate some functions of the DCX that are needed?
C. Cut the output leads on the DAC chip and fold them up. Then solder the new output wires to them?
2. Do we need any kind of output filtering?
3. What values for the output caps? In my case I will probably be feeding amps with 50k input impedance.
4. What type of caps.
I'm sure there will be more questions but hopefully this will get some discussion going.
Thanks,
Rod
At this point I'm into keeping it as simple as possible. I would like to try just bypassing all the output junk and just go straight from the DAC to RCA single ended.
Jans approach apparently does some high freq (20k and above?) filtering while others don't seem to think this is necessary.
So it looks like the very simplest is to somehow disconnect the output from the DAC to the rest of the stuff and connect it to a coupling cap. Use the sig gnd on the XLR output connectors as the new RCA sig gnd.
This all brings up a few questions:
1. What's the best way to get to the DAC output?
A. Cut the ribbon cable and tack onto the ends that go to the DAC?
B. Make and install a new ribbon cable?
1) Does this eliminate some functions of the DCX that are needed?
C. Cut the output leads on the DAC chip and fold them up. Then solder the new output wires to them?
2. Do we need any kind of output filtering?
3. What values for the output caps? In my case I will probably be feeding amps with 50k input impedance.
4. What type of caps.
I'm sure there will be more questions but hopefully this will get some discussion going.
Thanks,
Rod
Just to show an example, I am following the French school, cutting the cables (as you see here),
and soldering them to the new output stage, whatever could it be.
That's simple and fast, it's not a SMD surgery, just not so clean than the Didden solution.
All the functions are still operational, no hum, no short cuts.
For the low pass filter, here they use a first order, I think it's a safe precaution.
The blocking cap is mandatory, except if your amps have already one.
and soldering them to the new output stage, whatever could it be.
That's simple and fast, it's not a SMD surgery, just not so clean than the Didden solution.
All the functions are still operational, no hum, no short cuts.
For the low pass filter, here they use a first order, I think it's a safe precaution.
The blocking cap is mandatory, except if your amps have already one.
Thanks very much for posting this. It looks really straightforward and fairly simple. I do need to study it a little more. Have you done these mods?
Here's an English version of the mods: passive output stage for DCX2496
Has anyone else here done this? Any thoughts on it?
Thanks,
Rod
Thanks for the decoupling as a minimum suggestion.
For now lets just call going two way an experiment.
Cheers,
Rod
What mods I want to do on my DCX, if any.
Have you done these (the French mods or something similar) and if so what did you think of the results?
Thanks,
Rod
Thanks for your response which I find very interesting. There seem to be many supply mods for the DCX - which one did you do and might you have a link to it?
Cheers,
Rod
Subsonic
What is the easies way to calculate right butterworth subsonic filter?
What effect makes -3dB, -6dB and -12dB filter drops to cone excursion?
What is the easies way to calculate right butterworth subsonic filter?
What effect makes -3dB, -6dB and -12dB filter drops to cone excursion?
An externally hosted image should be here but it was not working when we last tested it.
Last edited:
I've completely redesigned the I/O stages and am adding PGA chips for volume control. These units will be used for my surrounds and subs.
In the end, no. I decided to go with individual main freq supplies for each unit.
Use Unibox, and get the filter calculator from FRD Consortium, design filter and import and add it to the model you're looking at.
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