301 Reply by Babaluma (edited by Babaluma 2022-12-13 09:16:45)

  • From: Milan, Italy
  • Registered: 2012-02-19
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Re: ADI-2/4 Prototyp

I'm using an external stereo DI/mic preamp where the maximum output level is 21dBu, plugged into the 2/4 analogue inputs/ADC with balanced XLR cables. It seems the 2/4 reference level of 24dBu or 19dBu suit it well. I'd like to match it exactly to 21dBu if possible, but am finding the L/R Trim Gain settings a little confusing. Should I:

A) Set it to 19dBu and both the Trim Gains to +2.0dB to achieve 21dBu
B) Set it to 24dBu and both the Trim Gains to +3.0dB to achieve 21dBu

Thanks in advance!

BTW, I am using a pair of the Shure A15AS attenuators between the outputs of the 2/4 and the inputs of my active ATCs, the Shures set to -25dB, and I can report it works very well. On the 2/4 main volume, I can have raw mixes set to -12dBfs, dynamic masters around -15, louder masters around -18, and slammed modern masters around -21 to achieve my reference level in the room (around 77dB SPL), with the ATC's sensitivity set to 2V. That also leaves me another 12dB for very quiet sources.

I am stunned by this thing, gonna plug the turntable in soon!

https://musicwall.app/hermetech

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302 Reply by KaiS (edited by KaiS 2022-12-13 11:36:52)

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Re: ADI-2/4 Prototyp

Babaluma wrote:

I'd like to match it exactly to 21dBu if possible, but am finding the L/R Trim Gain settings a little confusing. Should I:

A) Set it to 19dBu and both the Trim Gains to +2.0dB to achieve 21dBu
B) Set it to 24dBu and both the Trim Gains to +3.0dB to achieve 21dBu

Use B), Ref Level:+24 dB and Trim Gain Left / Right: +3 dB.

Trim Gain range is 0 to +6 dB additional gain, no negative range, so A) wouldn’t work.

A negative trim in the digital domain wouldn’t be recommended anyway, you could never reach 0 dBFS / fullscale and would lose all warning lights that the AD is already overdriven.


According Ref Levels:
• On the inputs, higher value means LESS analog Gain before the AD converter, you need more level to fully drive the AD.

• On the outputs it’s just the other way round, higher Ref Level means MORE analog gain after the DA converter, louder.

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  • From: Milan, Italy
  • Registered: 2012-02-19
  • Posts: 185

Re: ADI-2/4 Prototyp

Thanks so much for the quick response. Yes I really wasn't sure about positive vs negative values and how they relate etc. I'll go with B!

I just plugged the turntable in too, just stunning! Not had it set up in about three years, blasting The Cramps right now, big smiles! smile

https://musicwall.app/hermetech

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  • Registered: 2022-12-03
  • Posts: 6

Re: ADI-2/4 Prototyp

I apologize for the stupid question: I connected two headphones yesterday, one headphone as 4.4mm balanced and one as 6.3mm. The sound on the connection 6.3mm was very strange and I thought the connection would change automatically. 4.4mm was already connected and I wanted to listen only at 6.3mm. For this 3 questions:

1. Is it possible to possibly disable 4.4mm if I want to connect and listen to 6.3mm at the same time?
2. Is the reverse possible?
3. Can any damage have occurred to the headphones at the connection 6.3mm, since the sound has just been so strange?

305 Reply by MC

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Re: ADI-2/4 Prototyp

1. No, and that is clearly mentioned in the manual.
2. No again.
3. No once more.

Ph3/4 and PH1/2 give out one channel's sound as phase inverted mono signal. That is the expected signal for balanced mode and connection, but your headphone is unbalanced.

Regards
Matthias Carstens
RME

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306 Reply by jusu

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Re: ADI-2/4 Prototyp

hasan.ay386 wrote:

- FIR Linear phase EQ for speaker room correction. (Preferably with 65536 taps, if possible, because many high quality room correction software uses this tap size as a standard and it works well).

With 64k TAPs coefficients for the lowest filter frequency reach down to below 3Hz already regarding lamba when using 192kHz. I even operate with a 64k-TAP-FIR when treating 768kHz signals at least when it comes to low pass.

307 Reply by KaiS (edited by KaiS 2023-02-12 00:55:07)

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Re: ADI-2/4 Prototyp

jusu wrote:
hasan.ay386 wrote:

- FIR Linear phase EQ for speaker room correction. (Preferably with 65536 taps, if possible, because many high quality room correction software uses this tap size as a standard and it works well).

With 64k TAPs coefficients for the lowest filter frequency reach down to below 3Hz already regarding lamba when using 192kHz. I even operate with a 64k-TAP-FIR when treating 768kHz signals at least when it comes to low pass.

You both mix FFT and FIR filters.

A 64k Point FFT has a resolution on 3 Hz at a sample rate of 192 kHz, so it’s lowest band covers 0–3Hz.

FIR filters are a different topology that can be linear phase or minimum phase, depending on the filter coefficients.
The number of taps in an FIR-Filter topology does not need to be high, usually just a few, not in the k-taps range.

https://dspguru.com/dsp/faqs/fir/properties/


Practically I do not like FFT based filters for audio very much.
The windowing necessary for the FFT-process produces artifacts, specially at lower frequencies.
FFT is well suited just for measurements, as it has a good band separation.


I even don’t like linear phase filters sound-wise for their impulse response.
Natural filters are all minimum phase (no pre-ringing) as one cannot see into the future - that’s what linear phase filter’s pre-ringing in fact is.

In reality you cannot hear a signal before the drumstick hits the drum.
But linear phase filters produce a signal before, that makes low drums sound like having a fade-in.

ADI-2 offers a FIR based, minimum phase filter EQ, that doesn’t have this problem.

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