Question about passives

[DrWho]

That Merlin has a noise floor of -67dBu and 93dB of dynamic range...

1. That's through the analog I/O. With digital I/O the dynamic range is on the order of 138 dB.

2. You have not taken into account that I was a member of the design team. I have a Merlin ADC, built and tweaked from hand-selected components, with measured dynamic range of 119 dB.

So you're using outboard ADC/DAC devices?

I've been on the hunt for a good DSP unit (including ADC/DAC) that is optimized for consumer voltage levels. We just released a digital mixer at work that is pushing 110dB dynamic range (analog in/out) with a -88dBu noise floor, but I still think things need to be lower for the consumer world if you want true "audiophile" transparency through the xover....while using horns. Direct radiators will buy you a good 10dB of noise margin.

Does the Merlin have multiple digital outputs? That would actually be an interesting approach if someone wants to roll their own converters...still makes "ideal" volume control difficult though.

[Edgar]

Forgive me if this is a duplicate -- the forum lost my first response so I repeated it as best I could remember.

So you're using outboard ADC/DAC devices?

Actually, I found the Merlin DACs (with "insider" tweaks) to be adequate for my application.

I've been on the hunt for a good DSP unit (including ADC/DAC) that is optimized for consumer voltage levels.

I'd advise against considering the Merlin. First, it's a pro unit, with pro voltage levels and balanced I/O. Second, it was designed in the mid-1990s; it requires Windows 95/98 for the user interface (it won't run under later versions -- I've tried), and parts are impossible to find. In a word: it's obsolete. I keep using mine because it continues to work well, but once it fails I will replace it with something more modern (possibly using a PC as the processor).

We just released a digital mixer at work that is pushing 110dB dynamic range (analog in/out) with a -88dBu noise floor, but I still think things need to be lower for the consumer world if you want true "audiophile" transparency through the xover....while using horns. Direct radiators will buy you a good 10dB of noise margin.

Exactly. One thing that I do is attenuate the analog signals between the DACs and the amplifiers. This accomplishes two things: 1) it lowers the noise floor, and 2) it allows one to set up the gain structure such that the maximum position of the volume control corresponds exactly to the point where the amplifiers start to clip.

Does the Merlin have multiple digital outputs? That would actually be an interesting approach if someone wants to roll their own converters...still makes "ideal" volume control difficult though.

It accommodates up to four AES/EBU 2-channel digital outputs.

Volume control is problematic. I use a six-channel passive.

[mark1101]

I'm using Ashly Protea 3.6SP and 4.8SP active crossovers. I would not consider returning to passives for the system I use these on.

[DrWho]

Did you have any PC based processors in mind, or was that just a rolling thought? I'd think it would need some kind of dedicated hardware in the PC to have the bandwidth for crunching through all the filters without dropouts?

So what are you using for passive volume control?

[Edgar]

Did you have any PC based processors in mind, or was that just a rolling thought?

I've had very good luck with the Lynx AES/EBU I/O card, available in both PCI and PCIe. Beyond that, just about any PC will suffice.

I'd think it would need some kind of dedicated hardware in the PC to have the bandwidth for crunching through all the filters without dropouts?

Frankly, the processing load for filtering is trivial, even for LOTS of filters. The biggest problem is ensuring bit-accurate throughput of audio samples -- both Windows and MacOS tend to resample "under the hood" without telling you. I've found that ASIO is very good for sidestepping those kinds of issues.

So what are you using for passive volume control?

Wow, I don't even remember. As I said, at the moment my system is in storage. I think that it is an old Yamaha unit.