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TOPIC: 3x AN-FPs & 3x miniSHARCs in parallel

3x AN-FPs & 3x miniSHARCs in parallel 4 years 2 months ago #23879

  • Thunderstruck
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Dear Community,

I want to start a thread to discuss my existing Analog In / Analog Out setup which uses 3 AN-FPs attached to 3 miniSHARCs in parallel.
A picture of my box is attached below.
First of all, I am in search of audio perfection. This setup is not needed in any way as you can achieve great sound from a single miniSHARC.
I want something excessive as I will describe below.

1) I want a mono speaker because I don't believe in STEREO (anti-stereo is another topic).

2) I want 6-ways to reduce intermodulation distortion and reduce the freq range sent to the drivers.
20-63, 63-200, 200-632, 632-2000, 2000-6325 and 6325-20000 Hz.
This is the full-range divided logarithmically into 6 equal bands. Sqrt(2,000*20,000)=6,324.555

3) A lot of other stuff about the speaker but we are talking about our preamp.

4) I want to process the 2000-6325 and 6325-20000 Hz bands at 96kHz sample rate.
This is accomplished by inputting 2 full range L+R=Mono analog signals into the 1st miniSHARC's AN-FP XLR inputs.
I need the mono signal later because the 2x2 48kHz plugin doesn't support summing the two input signals.
I'm inputting in parallel to avoid multiple AD/DA conversions.
The trick I use to sum L&R works perfectly but is not shown in this older picture.
I use an ART Clean Box Pro to convert unbalanced L&R -10dBV to balanced +4dBu.
Knowing that XLR Pin 1 is ground, Pin 2 has positive signal, Pin 3 has negative signal and the AN-FP's balanced input will subtract the signal on pin 3 from the signal on pin 2 ...
I cross the pin 3 wires form the L to the R and the R to the L.
Now, the AN-FP inputs take +L-(-R)=L+R on the 1st input and +R-(-L)=R+L on the 2nd input.
This is done actively in the AN-FP so the summing is perfect and I now have mono signals (L+R) on both inputs of all 3AN-FPs.

5) I use the miniSHARC 4x8 96kHz Plug-in on the first miniSHARC to process the two highest ranges and output them on the 1st AN-FP's analog outputs. The FIR taps are extremely limited on the 4x8 96kHz plugin. I am only processing 2 ranges so I put all the taps I can on the two ranges as follows. 2000-6325 gets the 2048 maximum possible taps. The 6325-20000 range gets all the remaining 1316 available taps. The other 6 channels are not used but they require a minimum of 6 taps each. So, 2048+1316+6+6+6+6+6+6=3400 taps. Rephase process the 6324-20000Hz range at 96kHz sample rate nicely because the cutoff of 6324Hz is so high. Remember that double the sample rate means half the FIR length so processing lower freq requires massive amounts of taps which is exactly what the 96kHz plugin doesn't have. I chose the 96kHz plugin because:
2048 is enough taps to cover a LR8 2000Hz high pass & LR8 6325Hz low pass at a 96kHz sample rate
1316 is enough taps to cover a LR8 6325Hz High Pass at 96kHz sample rate.

6) I chose the OpenDRC 2x2 48kHz Plug-in for the 2nd miniSHARC.
I could use the miniSHARC 4x8 48kHz Plug-in or the miniSHARC 4x8 96kHz Plug-in but the following is the reason for my choice.
The 2nd miniSHARC is used for the two ranges of 200-632Hz and 632-2000Hz.
There are not enough FIR taps on the 96kHz plugin to process these ranges. See rephrase.
The 4x8 48kHz plugin has the same sample rate as the 2x2 48kHz plugin (48kHz) but the FIR taps are limited to 2048 max per channel. I only need to process two channels so I can only make use of 4096 of the 9600 taps on the 4x8 48kHz plugin. I have proven that 2048 taps at 48kHz sample rate is enough taps for LR8 filters at 200Hz (remember, the low freqs are the problem for FIR filters). So, I chose the 2x2 48kHz Plugin because it has 6148 taps on each channel. The 48kHz sample rate doesn't matter for lower freqs. The 96kHz sample rate is to get high frequency resolution. Remember these tips. They come in handy.

7) I chose the OpenDRC 2x2 48kHz Plug-in for the 3rd miniSHARC.
There is no way to get steep FIR filters at 63Hz with only 2048 taps. (Not steep anyway). With 6148 FIR taps on the 2x2 48kHz plugin you can get awesome filters in the two low freq bands of 20-63Hz and 63-200Hz. I only need a low pass at 63Hz for the 20-63Hz range along with all the other typical linkwitz transform to boost low freq roll off and some EQing. The 6148 48kHz FIR taps do this very well. I had trouble with just 2048 taps on a 4x8 48kHz Plugin and had to limit myself to way less steep filters to get an acceptable FIR solution at 63Hz.
Tip: Just download re-phase and you can play with everything I'm talking about for free. Just thank POS for developing such a wonderful program that we all can't live without.

I guess that's about it. I pause now and see how this goes.
Remember I started a new thread to discuss how to do all this with SPDIF inputs on 3 DA-FPs and 3 miniSHARCs.

Searching for audio perfection!
Thunderstruck in Marietta, GA USA

File Attachment:

File Name: 3xParallel...HARC.pdf
File Size:506 KB

File Attachment:

File Name: Speaker.pdf
File Size:336 KB

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Last Edit: 4 years 2 months ago by Thunderstruck. Reason: Make it easier to read
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3x AN-FPs & 3x miniSHARCs in parallel 4 years 2 months ago #23892

  • Thunderstruck
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Here are current pictures of my box.

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Last Edit: 4 years 2 months ago by Thunderstruck.
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