I got no noise with the IMG Stageline 2000, the bigger brother, 4 channels instead of 2. Sensitivity was 89 dB and my new pair of speakers are 96 dB. Will test tomorrow.
@Kjeldsen: Yes you are right, it's actually more my miniDSP 2x4s that seem to produce the noise. The LJM15Ds are probably good enough for me.
Nevertheless, ...
@TabCam: I'm looking forward to your report. For the time being, I have referenced your post in another forum, for those who might be concerned: Multi-Channel, Multi-Amplifier Audio System Using Software Crossover and Multichannel-DAC | Page 8 | Audio Science Review (ASR) Forum
Unfortunately, I immedieatly got a lot of hum on the right channel. It helped to lower the gain but then I had to max my Chord Hugo. I deduced it has to do with the power. It increases tenfold when I get too close to the mains line. I ended up disconnecting the Chord Hugo, and the hum was gone, maybe a ground loop?
Then I did have a hiss, but with my ear at tweeter (very sensitive horn) level. It starts at about the middle of the gain. I have no hiss with the Purifi amplifier I normally use. I used to have a similar hiss with my Anthem I225.
Then I did have a hiss, but with my ear at tweeter (very sensitive horn) level. It starts at about the middle of the gain. I have no hiss with the Purifi amplifier I normally use. I used to have a similar hiss with my Anthem I225.
Hi TabCam,
thanks for your effort, much appreciated!
I think hiss at the middle of the gain doesn’t sound too bad at 97dB sensitivity. The Stageline seems to have sufficient headroom.
The Stageline is a PA tool, so to assess its capabilities appropriately, we should perhaps apply the methods the PA pro-audio guys use to maximize the signal noise ratio in their systems while preventing clipping.
I guess this is what the Stageline’s clipping indicators are intended to be used for.
So we might proceed as follows:
- Set the Stageline’s gain to zero.
- Play a 1 kHz sine wave (50 Hz for subwoofers) at max output of the DAC or preamp.
- Raise the Stageline’s gain until the LEDs indicate clipping (or you can no longer bear the noise).
Alternatively, to avoid the noise and maximize the gain, we might disconnect the speakers and raise the gain until the amp output measures 1 Volt at our multimeter.
1 V ist he Stageline’s so-called input sensitivity (that’s where they start to clip). - Lower the gain a little bit so that no clipping is indicated anymore.
We should be set. Even at max preamp output there should be no way the Stageline will clip and thus produce this ugly and easily audible form of distortion. - Perform the most rigorous measurements and tests to assess the signal/noise ratio:
- a. Theoretical feasability: At max preamp output, do we hear hiss or hum when we stick our ears into the tweeter?
- b. Practical feasability: Do we hear hiss or hum at our listening position?
- c. Listening test: At typical listening volume level, play a very good recording (with high dynamic range) of John Cage‘ s „4‘33“ for piano“: If we don’t hear anything but our refrigerator humming, the birds singing or our tinnitus whistling, the amp might be good enough for us.
- Repeat the procedure with a 50 Hz sinewave, to assess whether the amp is good enough to at least drive your subwoofers.
If you perceive hiss in step 5.a, it might be interesting to know what happens if you disconnect the S Pro2 module from the input stage. It should be easy to remove the 26-pin plug temporarily.
The Stagelines have an input sensitivity of 1V. If I’m informed correctly, a preamp (or DAC) should be able to output more than that, to have headroom and get a satisfying result.
If you perceive hum, it might indeed be a ground loop issue or perhaps a DAC/amp gain structure mismatch. In case of a ground loop, a balanced preamp and XLR cables might help.
I hope other enthusiasts with more technical expertise chime in to correct our assumptions and the test procedure outlined above, if required. It might, for example, be adequate to use calibrated test signals or check the Stagelines max output with the help of a multimeter, or perform other more sophisticated procedures or to optimize the gain structure of your system.
It might be the case that your DAC and the amp don’t match quite well, so that our test procedure above might not make sense either.
Anyone to give advice?
Hi daniboun
i opened my DAC and there are BB opa 1632 inside for each AKK4497 chip for sure
chris
In my understanding it means if your DAC output is at 0 dB, say 3/4 of your volume knob, you will not have to turn the IMG's pots a lot to get the clipping LEDs lit (the IMG has a high input sensitivity of 1V), so the noise should be minimal, if perceptible at all even with the ear stuck into the tweeter.^
For me, as I now see, it means that our situations are not comparable. My miniDSPs have only 0.9V output, so I would have to turn the IMG's volume knobs far more to drive the unit into clipping, so more noise to be expected in addition to the miniDSP's noise. If I upgraded to an Aurora board to do the DSP+DAC it would be better with 1.55V output.
Nevertheless, in your case, just out of curiosity, it might be interesting to know whether you can detect a difference between the Purifi at full output, and the IMG with adjusted input sensitivity.
My IMG StageLine is lend out but even so, the Purifi at full output just passes on the noise from the preamplifier. With my Arcam it has a very slight hiss with ear close to tweeter, with a Chord Hugo it has zero hiss. The IMG StageLine always had a hiss. Wil verify but probably will happen during summer holiday
Hi, image from inside the 400D and 800D here Opinion on IMG Stage line STA-400D amplifier with Hypex modules | Audio Science Review (ASR) Forum
Installed my 400D today. Only using it for 100hz downwards so not a lot to report yet. Need to give it a movie workout.
Only comments I can make is that the heatsink side gets very hot and the fan noise is only audible when you put your ear to it. Not silent but close enough.
Only comments I can make is that the heatsink side gets very hot and the fan noise is only audible when you put your ear to it. Not silent but close enough.
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It is a 1u amp after all. Fans that small need to make a bit of noise in order to have any effect on airflow whatsoever.
I've seen some other more quiet compact designs have used larger fans tilted at an angle inside the enclosure and a bit of creative ducting.
Small fans need higher rpm than bigger fans to move the same amount of air, same as with woofers.
I've seen some other more quiet compact designs have used larger fans tilted at an angle inside the enclosure and a bit of creative ducting.
Small fans need higher rpm than bigger fans to move the same amount of air, same as with woofers.
No, I'm not vcomplaining about the fan noise. Just drawing it in to comparison to the manual stating silent operation. I guess in an industrial or installation setting this qualifies. Mine is in a cabinet so is inaudible.
My wife and I just bought a house and I did my first sweeps for the set up and it does show a roll up at 20hz. Again, fine with me as we are in a Victorian terrace in London and pays to not bother your neighbours with infrasonic noise.
My wife and I just bought a house and I did my first sweeps for the set up and it does show a roll up at 20hz. Again, fine with me as we are in a Victorian terrace in London and pays to not bother your neighbours with infrasonic noise.
