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Old 17th January 2010, 08:10 PM   #2381
mige0 is offline mige0  Austria
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Quote:
Originally Posted by panomaniac View Post
Hey Michael.

So the output of the DCX was never full scale, but -6dB. Driven with a digital input only.
Not really sure why ARTA places the noise floor below -120dB. That should not be possible working in 16bits, as I was. RightMark tells me the noise floor is about -94dB.


Yeah, I had sort of feeling your ARTA measurements are not calibrated the right way.
With 16bit measurement resolution your traces must be waaaay higher - even for a clean 24bit measurement plots are too low !
- did you use averaging ?

In general its no good idea to measure a 24 bit device with a a 16 bit soundcard - so I'm a little bit lost about the validity of plots shown - possibly have to check out myself

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Originally Posted by panomaniac View Post
Obviously the stock DCX outputs had to be (analog) attenuated much more than the simple transformer outputs to reach that level.
Did not get your point ? - do you say the transformer in your plots (multi-tone measurement stock versus transformer ) is driven at a different level – though plots show roughly same levels?

How much was the difference in drive level then?
Confused...

Michael

Last edited by mige0; 17th January 2010 at 08:22 PM.
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Old 17th January 2010, 08:51 PM   #2382
mige0 is offline mige0  Austria
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Originally Posted by mige0 View Post
Fed by 100mV, distortion is down to ~ 24bit territory, up form ~200Hz – not that bad !
Have to correct myself.
We are roughly ~ 80dB below signal level up from 200 Hz with that transformer – by no way 24 bit !
Possibly down at ~ 100-110dB up from 1kHz - if I extrapolate distortion linearly.

Michael

Last edited by mige0; 17th January 2010 at 08:53 PM.
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Old 17th January 2010, 10:53 PM   #2383
Pano is offline Pano  United States
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The reason I used 48KHz/16 bits is so that Windoze won't resample and recalculate everything.
I'd use 24 bit mode if the silly soundcard drivers would allow it. They do in ASIO, but not MME or DS. As I don't have the pay version of ARTA, I can't use the ASIO function. I do use ASIO in HOLMImpulse

All drive levels for all ARTA tests were the same. -6dBFS from the computer. It's the outputs that needed attenuation to match the sound card inputs. Just the built in pad and/or volume knob were used to attenuate.
Linear averaging was used on all plots - 20 passes. Kaiser5 window. FFT 65536
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Old 18th January 2010, 01:39 AM   #2384
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I am the proud owner of a brand new in the box DCX-2496. For some time I have been using a DEQ-2496 Real Time Analyzer followed by a 3-way Rane analog crossover that feeds a Rane MA-6 , six pack amplifier. The speakers are Linkwitz style open baffle panels. Please do not tell the single end tube guys.
I am pulling the Rane crossover out and putting in the digital crossover. I want to possibly keep the DEQ-2496 in the loop, it is dialed to the equalization required the open baffle speakers. I also like being able to plug in the Behringer microphone and check out the speaker and room performance.
Do any of you long time users have any thoughts, ideas or recommendations? And a related question , will the DCX-2496 do the needed open baffle equalization without the RTA in the loop?
Thank You
DT
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Old 18th January 2010, 03:54 AM   #2385
Pano is offline Pano  United States
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Hey DT we won't tell the tube fans you're here.

The DCX can do almost all of what the DEQ does - and more. Tho I'd rather do room EQ with the DEQ - it's just easier and more powerful. I do think that the DCX will be fine for your open baffle rig, it worked for me on several I built.

I use a DEQ in front of the DCX for a bit of room EQ and also just for the pretty RTA graphics. I found that the better and better I got at using the DCX and building crossovers, the less I needed the DEQ. But it was a wonderful tool for getting there.

Bottom line, they can work well together. Just come digital (AES - balanced) out of the DEQ into the DCX. Easy.
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Old 18th January 2010, 07:03 AM   #2386
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Thank you panomaniac for being discrete.
I will hook it all up and report back. Also I enjoy seeing the test graphs, cool.
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Old 18th January 2010, 09:25 AM   #2387
Rudolf is offline Rudolf  Germany
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Originally Posted by DualTriode View Post
I also like being able to plug in the Behringer microphone and check out the speaker and room performance.
Caution! In the DCX the microphone only works for measuring the delay between speakers. It does NOT measure the frequency response of room or speaker.
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Old 18th January 2010, 01:00 PM   #2388
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Why do you say that? I've found it pretty good for room EQ using the built in pink noise.
Oh, maybe you mean for the DCX. True. It doesn't do FR measurements, just delays.

I thought DT meant using the mic with the DEQ2496.
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Old 18th January 2010, 01:57 PM   #2389
mige0 is offline mige0  Austria
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Originally Posted by panomaniac View Post
These plots show how the DCX stock output has a distortion that rises with frequency and the transformer has a distortion that drops with frequency. To my ear, this must be why I feel that the transformers remove a lot of digital glare or brittleness that I don't like. The swept FR is so close between these two there is no point to post it.

Quote:
Originally Posted by panomaniac View Post
The reason I used 48KHz/16 bits is so that Windoze won't resample and recalculate everything.
I'd use 24 bit mode if the silly soundcard drivers would allow it. They do in ASIO, but not MME or DS. As I don't have the pay version of ARTA, I can't use the ASIO function. I do use ASIO in HOLMImpulse

All drive levels for all ARTA tests were the same. -6dBFS from the computer. It's the outputs that needed attenuation to match the sound card inputs. Just the built in pad and/or volume knob were used to attenuate.
Linear averaging was used on all plots - 20 passes. Kaiser5 window. FFT 65536



Hi Panomaniac,
did the multi-tone measurement with my unmodified soundcard – here is what I found:

1.) ARTA shifts down 0dBFS to the –20dBFS line in multi-tone measurement – bug or feature ?
2.) As expected – If you change your output signal other than with a pure voltage divider there is no guarantee that the observed differences in performance are from the insertion of a transformer.

To show how the output stage (2 opamps after the DAC in case of my soundcard) produces different results below two measurements
– first one with digital signal OUT at –3dB
– second with digital signal OUT at –13dB


Output digitally attenuated by 3dB :

Click the image to open in full size.



Output digitally attenuated by 13dB :

Click the image to open in full size.


For both measurements input gain of the soundcard was adjusted to provide roughly same resolution ( ~ -10dB record level).
We see that the hasch at the top end gets increased when approaching 0dB digital attenuation.
Depending on design this may or may not clear up at the levels you have measured at with the transformer variant.


Michael

Last edited by mige0; 18th January 2010 at 02:01 PM.
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Old 18th January 2010, 02:07 PM   #2390
Pano is offline Pano  United States
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Quote:
Originally Posted by mige0 View Post
did the multi-tone measurement with my unmodified soundcard – here is what I found:
Interesting. This is just a loop back on your soundcard, right?

Quote:
As expected – If you change your output signal other than with a pure voltage divider there is no guarantee that the observed differences in performance are from the insertion of a transformer.
Right. That is why I tried to keep the digital level always at -6dB and used the analog volume control (pot) on my soundcard for level adjustments.

Quote:
Output digitally attenuated by 3dB :
Output digitally attenuated by 13dB :
Where was this attenuation done? In Arta or somewhere else?
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