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Behringer DCX2496 digital X-over
Behringer DCX2496 digital X-over
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Old 9th January 2010, 07:46 PM   #2251
Pano is offline Pano  United States
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Behringer DCX2496 digital X-over
I get very consistent results with auto-align. I use only the the short delay and phase (polarity, actually) and use the ECM8000 mic. You might try that. Check your settings.

You can improve on the auto-align settings - but it takes some work.
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Old 9th January 2010, 08:04 PM   #2252
SQLGuy is offline SQLGuy  United States
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Auto-align is pretty consistent for me as well.

Legis, does your setup still have passive crossover components between the amps and speakers? You might also double-check, and try swapping, the absolute phase of the bass or treble components.
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Old 9th January 2010, 08:08 PM   #2253
mige0 is offline mige0  Austria
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Gary, I remember Lynn having mentioned elsewhere, that you did a output mod on the DCX with some hi-grade transformers by your own.

What I am specifically interested in is, if you've done some quality measurements of such transformers - simple harmonics would do here.

The reason I ask is that I never got around transformers to *not* add significant 3nd order at low frequencies - what I call the "iron sound" by myself.

Can this be overcome by selecting core material ?

To show an example - below we see those distortion.
It may be remarkable that these are pretty heavy toroidal monsters spec'ed for 100W power amps (Plitron / Amplimo pat2100-cfb).

But even more amazing for me was that they show this behaviour even at veeeery modest 760mV rms !!!


Behringer DCX2496 digital X-over


Behringer DCX2496 digital X-over


The levels here are –60 dB / -65dB for 30Hz / 90 Hz respectively.
You know, I don't wanna go into a discussion about perception of these 3rd harmonics – just want to know what possibly is "common"

So, what realistically to expect in this regard form much smaller – signal level - types ?

Michael

Last edited by mige0; 9th January 2010 at 08:23 PM.
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Old 9th January 2010, 08:21 PM   #2254
Legis is offline Legis  Finland
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Quote:
Originally Posted by SQLGuy View Post
Auto-align is pretty consistent for me as well.

Legis, does your setup still have passive crossover components between the amps and speakers? You might also double-check, and try swapping, the absolute phase of the bass or treble components.
Yes, Monitor Audios still have passive x-overs, I'm planning to sell them and buy speakers without passive x-overs though. Could this be the actual cause for very inconsistent distance measurements? This would be odd, since my Marantz sr5004 was very consistent every time, when I had RX6s plugged to it. I will take 5 measurement in a row now and will give you specifict data soon --->
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Old 9th January 2010, 09:08 PM   #2255
Legis is offline Legis  Finland
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Inputs:
1&4 = subwoofers (no subsonic filter/passive x-over)
2&5 = RX6 woofers (with passive x-over)
3&6 = RX6 midrange/woofers & tweeters (with passive x-over)

25mm = 1 inch

Short delays ON
Long delays ON
Polarities ON

Equipment: Behringer EMC8000 mic


Measurement 1

Delays:
1&4 = 1120mm (3,26ms)
2&5 = 1010mm (2,94ms)
3&6 = 1900mm (5,53ms)

Polarities:

1&4 = inv
2&5 = inv
3&6 = inv

Measurement 2

Delays:
1&4 = 1806mm (5,34ms)
2&5 = 1000mm (2,91ms)
3&6 = 2030mm (5,91ms)

Polarities:

1&4 = inv
2&5 = norm
3&6 = inv

Measurement 3

Delays:
1&4= 1306mm (3,80ms)
2&5 = 692mm (2,01ms)
3&6 = 1374mm (4,00ms)

Polarities:

1&4 = inv
2&5 = norm
3&6 = inv

Measurement 4


Delays:
1&4 = 1962mm (5,71ms)
2&5 = 956mm (2,78ms)
3&6 = 2034mm (5,92ms)

Polarities:

1&4 = inv
2&5 = inv
3&6 = inv

Measurement 5

Delays:
1&4 = 596mm (1,68ms)
2&5 = 448mm (1.30ms)
3&6 = 1460mm (4,25ms)

Polarities:

1&4 = inv
2&5 = inv
3&6 = inv


Variance: (smallest value - greatest value)

1&4 = 596mm - 1962mm; (difference 1,33 metres = approx. 4,5 feet)
2&5 = 448mm - 1010mm; (difference 0,58 metres =
approx. 1,8 feet)
3&6 = 1374mm - 2034mm; (difference 0,66 metres =
approx. 2,2 feet)


Is this variation within normal variance? Could someone alse do the same and report using the same layout (easier to compare)?

I don't get those inverted polarities since all my my speaker cables are right of course. And there is variance even in polarity...

Last edited by Legis; 9th January 2010 at 09:16 PM.
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Old 9th January 2010, 09:40 PM   #2256
Legis is offline Legis  Finland
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I get more consistent values by testing only left or right side speakers at a time (since microphone might not exactly in the middle of the speakers). Still it thinks that all speakers are inverted.

I highly think that the setting it persistently proposes (that outputs 2&5 are 80cm - 1m closer than others) sounds "wrong phased". It sounds almost like when you have othes speaker's + and - leads wired wrong. In my case: auto-align FTW
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Old 10th January 2010, 03:03 AM   #2257
Gary P is offline Gary P
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Quote:
Originally Posted by mige0 View Post
I'm interested if you come to the same findings and conclusions !


Michael
I've got the system setup so I can switch between the 2 setups, one with teh BlueCat Gain plugin and the other with Nyquist Eq setup for gain control. First impression is I can't tell much if any difference at -30dB. It's hard trying to compare sound quality at low level. The instinct is to turn up the volume to hear more but that defeats testing SQ at low volume... I need more test time late at night when things are quiet.

Have you tried the BlueCat gain control?

It did not take long to decide I don't like the way the system responds to volume changes with Nyquist EQ in place of the BlueCat gain control. With Nyquist EQ you end up with a range of -60dB (or so) to +12dB. There does not seem to be a way to limit the range. With BlueCat I'm able to set the range of the volume control to the MIDI range. I've settled on 0 MIDI = -50 dB and 127 MIDI = 0dB.
On the music server/home theater PC we are using an Electrone 9006 wireless keyboard (Electrone - Problem Solving Peripherals) that has a track ball built in. For MIDI control we are using the virtual MIDI XY controller program vimidi. To get the MIDI controls into Console the program MIDI Yoke is used.

We have the ~ key assigned to volume control. Keys 1 through 6 are used to control the 6 input signal pairs. Hold down the ~ key and move the mouse left and right with the track ball to control the volume. This works great because the volume control is available regardless of what window has focus. I can use the volume control even when the 42" monitor is off. Only gotcha is you don't want to adjust the volume if a text entry box in focus...

With Blue Cat gain control the usefull range of control is full left mouse for minimum volume to full mouse right for loud. With the Nyquist EQ the extra 12dB of gain causes loud to occur when the mouse is only 25% of the way across the screen cutting down the resolution of the volume control.

I'll update after some good quiet listening time.

Gary
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Old 10th January 2010, 08:26 AM   #2258
AR2 is offline AR2  United States
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It has been a while since I did any work on my DCX. I have been in the mood to do something, but didn't find anything interesting so far until recent. As some of the readers recall many pages back, I described my mods in detail.

http://www.diyaudio.com/forums/multi...ml#post1370646

http://www.diyaudio.com/forums/pass-...tml#post872582


I did digital and analog mods. Both were very rewarding. I didn't do much with power supply as I do not believe there is much to be gain there unless the whole circuitry on the board is changed, what is not feasible. As someone mentioned a few posts back, there are some benefits to the switching supply which I do agree with. Really what would be improvement is bypass to the chips that are on the board and maybe little bit more sophisticated regulators.

Anyways, I have been using my Lundahls in the output 1:2 and I ether had them straight to amp or with CCS XBOSOZ preamps that were giving 13 dB gain. My preference would be to use 1:1 Lundahls with no preamps after, just straight to the amp, but that is not possible with speakers and amps I am using. So since that is the case I wanted to see if I could make something little bit more sophisticated and up to date and to replace XBOSOZ as preamp.

The goal was not to have any caps in the signal path, and still to use my Lundahl 1674 amorphous core transformers. Next I wanted to use jFets. So I enlisted help of the mighty Zen Mod. We decided to utilize Lundahls to provide voltage gain since they are 1:4 and than to provide balanced B1 buffer in order to provide proper impedance to the DACs and to isolate DACs from the rest of circuitry. In my case I need to use the Lundahls in 1:4 configuration, but this circuitry would work with 1:2 as well as with 1:1 Lundahl configuration, but RC configuration needs to be adjusted - Located on secondary of transformers. With 1:4 and buffer I have 18dB gain when the circuit is balanced . As you could see in the schematic, Choky designed Cap Multipliers and very good regulation for the power supply.

So far I completed this circuit on the test board and I am listening it now. It sounds really good. The transparency is even better than what I had before with XBOSOZ, very delicate an open. I am planning to produce circuit boards with the help of another good friend Cviller! This circuit is pretty much universal, not just for Behringer but for any other voltage DAC output. Transformer provide DC block as well as attenuate any RF garbage as they have very flat response up to 48 - 50 KHz. The choice of transformer and voltage gain is dependent of the minimum impedance that could be connected to the DAC.

Here is the schematic, for your review. Just to add in order to avoid the confusion the bottom power supply is for my digitally controlled relay volume control.

Thank you Zen Mod and Cviller!
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File Type: pdf DAC, Lundahl, Buffer.pdf (75.1 KB, 107 views)
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Old 10th January 2010, 08:59 AM   #2259
AR2 is offline AR2  United States
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Here is the measurement taken from the circuit on the test board, and without cap multipliers and regulators. I used Tektronix Power supply, and I do expect even more improvement once mounted on the board and with complete power supply as shown in the schematic. This is measured in 1:4 ratio on the Lundahl. Any other lower ratio combination such as 1:2 and 1:1 would yield even better results.
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Old 10th January 2010, 10:27 AM   #2260
mige0 is offline mige0  Austria
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Quote:
Originally Posted by AR2 View Post
Here is the measurement taken from the circuit on the test board, and without cap multipliers and regulators. I used Tektronix Power supply, and I do expect even more improvement once mounted on the board and with complete power supply as shown in the schematic. This is measured in 1:4 ratio on the Lundahl. Any other lower ratio combination such as 1:2 and 1:1 would yield even better results.
Is the "Intermodulation Distorion" plot - where the 3rd order harmonics I mentioned (plus a whole bunch of odd order harmonics) can be seen as well - calibrated in dBu or dBV ?

Michael
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