Overall freq. response *that* bad? - diyAudio
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Old 12th April 2005, 08:33 PM   #1
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Default Overall freq. response *that* bad?

Hi,
I made a few measurements:
first: Sweep from CD-> Voltage divider -> phonopre -> amp -> PC Soundcard
Looks like that:
Click the image to open in full size.
please consider that linear (inside about 0,3dB), the differences at the edges are due nonlinearities of CD->amp->Soundcard loop

Now a triangle @ 1kHz of the cardas Test LP
Sweep from LP-> DL103/SME3009/TD125MKII -> phonopre -> amp -> PC Soundcard:
Click the image to open in full size.
Not that bad, I'd say.

But now the cardas sweep from 30Hz - 30kHz looks like those tiny little creatures I saw last time in schools biology lesson:
Click the image to open in full size.

I'd never thougt that this could be that bad!

The loudest part is around 14kHz, then suddenly falling

Is something wrong here? Normal? Anything else?
Rüdiger
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Old 13th April 2005, 05:54 AM   #2
Werner is offline Werner  Europe
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The frequency sweep on the HFN test record is equally useless. I also have the Cardas, but haven't found the time to try it. Your images make me desparate, though.

Try a pink noise track and use a lot of smoothing. That gives results much more in line with what you'd expect.

Ah, you could also try the Cardas at 45rpm. If the frequency anomalies scale with speed they are on the record. If they remain in place they are in the replay chain.
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Old 13th April 2005, 07:01 AM   #3
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Is this really any worse than you would expect from a moving-magnet cartridge? The tip-mass resonance looks a bit low but that's all.

It is vinyl playback for heaven's sake! You can't expect too much from it, although it would be interesting to see the response using a good moving-coil cartridge.
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Old 13th April 2005, 07:04 AM   #4
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Hi Ouroboros,
as I wrote, it is a Denon DL103 MC-Cartridge, which is not high end, but certainly we do not see the datasheets flat respons from 20Hz to 40kHz...

@Werner: I will certainly try it at 45RPM

Rüdiger
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Old 13th April 2005, 07:18 AM   #5
Werner is offline Werner  Europe
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A DL-103 measures quite flat. See here:

Click the image to open in full size.

These are response and channel separation for a pink noise track. You have to compensate mentally for the -3dB/oct droop of the noise.


Doing so with different software fooled into thinking that the output of the cartridge is the response to the input generated by the sound card (which it obviously isn't) yields this: cheap old MM top, DL-103 bottom. Much more ragged, most probably due to the lack of synchronisation between input and output.

Click the image to open in full size.



Incidentally, the 103 measures excellent in all respects. It is almost as flat as my Allaerts, has almost the same channel seperation, and one particular sample of 103 even had less distortion.
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Old 13th April 2005, 07:28 AM   #6
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Werner,
thanks for the instructive cartridge measurements. How was the test setup?

Rüdiger

edit: spelling
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Old 13th April 2005, 07:39 AM   #7
Werner is offline Werner  Europe
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HFN test record with pink noise track, turntable/cartridge (Technics SL-D2 in above pix), phono pre (probably Rotel 970, don't remember), sound card (Terratec Phase 26 with heavy mods to compensate for Terratec design engineer's incompetence, end-of-rant), PC.
Demo Audition used to record and off-line spectral analysis, demo S-lab configured for real-time analysis with pink noise out/in.
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Old 13th April 2005, 06:27 PM   #8
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It's the sweep. The maximum is now at 18kHz.


Click the image to open in full size.




I go and get me another test record, maybe I can find the HFN or somthing similar,
Rüdiger
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