Deqx?

[kjbii]

Hi Keith,

 

this provides extremely useful and detailed answers to most of my questions, and leads back to the clocking/synchronization question. I can’t wait for your report on the RME HDSP card driving 4 DACs. At this point, I would settle for two.

 

I am wed to the Directstream DSD DAC as my core component. It can be configured to accept various digital inputs, including USB and Ethernet. I prefer the Ethernet connection to avoid myriad USB issues, as well as to provide server and control capability, but can use any of the other inputs including XLR (AES/EBU). The DAC upsamples data from all sources to 10x DSD rate, buffers the incoming data, and after processing it is downsampled to 2x DSD rate and output through a passively filtered analog section rather than an active analog output stage.

 

This does not mean much to me, but it may be significant for integration/synchronization with other components such as a Hilo/Hapi/RME HDSPe AES32. The DAC “handles the PCM conversion from AES/EBU, S/PDIF, TOSLINK, I²S and USB without recovering a clock, by simply watching for the edges and making decisions about what they mean in context. The output clock’s rate only depends on the long term average rate of the inputs not on any edge or other local feature.” Maybe this explains the lack of a clock input. I would also appreciate any insights that Dallas has on this question.

 

My goal is to biamp/triamp two (or three) horns, crossing over from the bass bin to a midrange driver at 440 Hz. I have been using an ESS AMT as the high range driver in a triamped configuration, crossing over at 2200 Hz, but think that it is superfluous, in view of the very low tweeter volume at my typical (70 dB) listening levels. Crossing over at 1700/1800 does not improve speaker performance, despite (or due to?) the colorless and instantaneous response of the AMT. Instead, I will try the BMS4592nd passive crossover, using the integrated second high frequency driver. Its coaxial orientation should provide time alignment with the midrange driver, as well as vertical and horizontal linearity.

 

Apart from other advantages of DSP upstream or downstream (DEQX), time alignment of the bass bin and midrange horns is critical. A delay of about 13 ms in the mid-range is about right. One possibility (system 3) is to use an analog active crossover, and a 2-channel AD/DA delay filter, rather than a digital crossover, if such a device exists.

 

Biamping and time alignment provide an image that is almost holographic, even using an inexpensive and noisy breadboard Behringer crossover. System 1 and System 2 describe my limited understanding of a software-implemented upstream DSP crossover, and a downstream DEQX crossover, converting the “perfect” DAC two-channel output to a digital signal fed to the DEQX. It’s a lot to pay for a solution that may significantly degrade the quality of the signal. I don’t know what to expect.

 

Thanks for your suggestion of the RME HSDPe card, which is a relatively inexpensive alternative that would surely drive my essential DAC. It will take some time to go over and digest your extensive comments, which have saved me endless frustration and at least $16000 to date.

 

I'll be back when I start setting up Acourate.

 

many thanks, Ken

 

 

Hi Ken, to answer your questions:

 

1. What you need for Acourate. At a minimum you need (a) a microphone, and (b) an interface for the microphone. However, if you wish to use Acourate as a replacement for your crossover, you would also need a multi-channel DAC, enough channels of power amplification for each channel you plan to implement, and suitable software (e.g. HQPlayer, Acourate Convolver, JRiver, or BruteFIR).

 

2. Implementing Acourate with multiple DAC's. You have two options: (a) buy a multichannel DAC like the exasound E28, Lynx Hilo, RME Fireface UC, or Merging NADAC/Hapi/Horus, or (b) buy a multichannel output card like the RME HSDPe AES32 (which has multiple AES/EBU outputs) and enough individual DAC's for your needs.

 

As for "each individual DAC", I have been lead to believe they need to be clock synchronized to avoid clock drift. At least, in theory. I do not know anybody who has tried using four DAC's in an 8 channel multi-DAC setup, and this is after a year of hanging around various forums and keeping a close eye on everyone's Acourate setup. Everyone whom I am aware of who uses Acourate as a crossover replacement is using it with a multichannel DAC for simplicity and to avoid the said theoretical problems with clock drift. How much of a problem this is IN REALITY, I do not know - and I am hoping to find out. Ask me this same question in a year - my next move will be to replace my Merging NADAC with four DAC's, driven by my RME HDSPe AES32 sound card. I have not yet decided on which DAC's I will buy, because at this moment I am lacking in money, in knowledge, and because I have other audio priorities which I need to address first.

 

I have much respect for Dallas, who has actually been one of my mentors in my journey. He did this before I did, and my current system as it stands is very much a copy of his. However, he has not entirely convinced me that the clock sync issue is so serious that it is an absolute necessity. I always have time for what he says, so I would be very appreciative if he could weigh in. If you were concerned enough about this, you could always make sure that the DAC's that you purchase have clock inputs so that you could clock sync them if required. Suitable candidate DAC's which include clock inputs would include - DCS, Esoteric, and Antelope.

 

3. Can digital audio be passed through a Hapi/Horus to multiple DAC's - the answer is NO. What you need is a sound card like the RME HDSPe AES32, or equivalent (I believe Marian makes such a sound card). The RME has a single ASIO driver, which reports 16 available digital outputs to any software that asks. On the back of the RME card, you connect channel 1 to your first DAC, channel 2 to your second DAC, channel 3 to your third DAC, and so on. You then set your convolution engine to something like this:

 

Input Channel 1 (Left) --> Convolution filter 1 --> Output to DAC Channel 1

Input Channel 2 (Right) --> Convolution filter 2 --> Output to DAC Channel 2

Input Channel 1 (Left) --> Convolution filter 3 --> Output to DAC Channel 3

Input Channel 2 (Right) --> Convolution filter 4 --> Output to DAC Channel 4

Input Channel 1 (Left) --> Convolution filter 5 --> Output to DAC Channel 5

Input Channel 2 (Right) --> Convolution filter 6 --> Output to DAC Channel 6

... etc.

 

Hope this clears it up.

[Keith_W]

but thanks, and OUCH! That's quite a bite, the amps must make up the difference in $100K. What horns are you driving?

Acapella High Violon horns. I have to go to work now, i'll reply to your other post later.

[Keith_W]

Ken, some comments on your proposed systems.

 

System 1: As far as I am aware, the Merging Hapi does not have a digital output. I would forget about that DSD DAC and simply use the Merging Hapi to do all D-A conversion.

 

System 2: there is not much point in having your "good" DA converter upstream of the DEQX, only to have it reconverted to digital. This costs more, increases system complexity, introduces more points of failure, and likely sounds worse. If I were you, I would simply feed digital into the DEQX and use the digital output of the DEQX into your DAC.

 

System 3: You would lose the benefits of DSP with this system.

 

My system topology is the same as Mitchco's and Dallas'. It looks like this:

 

- PC source (running Acourate filters) ---> Ethernet (8 channels) --> NADAC or other 8 channel DAC --> power amps.

 

You could also do:

 

- PC source (running Acourate filters) --> RME HDSPe card --> 8 channels of AES/EBU out --> 8 DAC's of your choice --> power amps

 

I need to stress this point again: if you choose to string together a number of 2 channel DAC's, you will need a single ASIO driver which reports multiple available channels. Plugging two of these DAC's to your computer via USB or Ethernet will not work. I am not aware of any software which is able to output Channel 1, 2 to one ASIO device, Channel 3, 4 to another ASIO device, and then Channel 5, 6 to yet another ASIO device. All your DAC channels have to a be available on the same ASIO device.

 

Alternatively, you could set your system up like this:

 

PC --> (digital via USB) --> DEQX or MiniDSP --> (AES/EBU out) --> multiple BYO DAC's and power amps

 

In this configuration you are using DEQX or MiniDSP as the "brains" only, without using the ADC's and DAC's. The disadvantage of using DEQX in this configuration are: only 6 channels available (may not be a problem for you), and it costs more than if you were using the PC only in the first place. Also, this solution gives you less computing power than a PC, and you are limited to PCM.

[twist222]

Ken,

Keith has given you some great advice above. The only thing that might be worth following up on is Keith's comments about about digital out's from the Merging Hapi. Copying direct from the Hapi brochure the base model Hapi provides "8 (4 Stereo) AES/EBU I/O" it also provides 2 chanels of digital I/O on spidif.

The 8 channels of AES/EBU I/O is via db25 which whilst very common in pro audio will require a db25 to XLR cable to interface with audiophile dacs. If it is important to you, one that is worth further research is if the Hapi's digital outs pass DSD. 8 channels of 192kHz will not be an issue but I am not sure what it does with DSD on the digital outs. Keith may even be able to advise on this? One good thing about the AES/EBU digital outputs is that they also carry the clock signal so multiple dacs will be able to be slaved to the clock in the Hapi.

The digital ins and the option to install a ADC card in the Hapi will should give you 2 options to record and playback through the same ASIO driver. Just remember you will need to sync the 2 clocks if you are using a separate ADC for recording.

I am also planning on going to Accurate (4 way active set up at the moment) and was looking at using the Hapi as a way to interface my Metric Halo ULN8 (Mac only) to a Windows based computer whilst I am waiting for MH to release the long awaited 3d card. Hence I have been following Keith's posts with interest.

Regards

Mark

[Keith_W]

Even if the Merging Hapi was capable of 8 channels of digital output (NOT arguing with you here, I have no idea!), it would be a waste of money to do this. It would be cheaper to use the RME card. I suppose the downside is that you no longer have an Ethernet connection between your PC and your DAC, which means that your PC will have to be physically located next to your DAC's.

 

I acknowledge that the Ethernet connection is a very nice advantage. For one, it means that your PC can be a fire breathing monster with lots of cooling fans, and built into an ugly case. You just hide it where you can't see or hear it and enjoy the computing power.

[twist222]

Keith,

One of the reasons I was looking at the base model Hapi was at US$2500 it gave me the option to use an Ethernet connection and whatever DAC's and and ADC's I want. Like your internal digital card option it would also give Ken the option to start with whatever dacs he has and add higher quality or more dacs if he wish's to go 3 or 4 way in the future. Or he would have the option to install Mergings 8 channel DA8P card into one of the Hapi's slots if he preferred.

In the interests of disclosure since I only need to interface with a Windows based machine to take my measurements for Accurate and create the filters I am planning to use the ULN8 (AES/EBU inputs) with an existing Lynx AES 16e card I have for measuring and then use the Mac version of HQ Player direct into the MH ULN8 for playback. Not at your level of equipment but hopefully it will exceed what I was able to achieve previously with 2 DEQX's in a 4 way set up.

If I didn't already have the Lynx card or I needed to keep the Lynx card in the system for playback the Hapi would still be high on my options list. Longer term I understand the 3D card for the ULN8 will allow Ethernet connection between computer and ULN8.

Keith,

I have learnt a lot from your posts and appreciate your willingness to share and attention to detail. I would also welcome any thoughts or input on the way I am heading with Accurate. Although I need to make sure I do not hijack Ken's thread.

Anyway hopefully we have been able to give one more option to consider.

Regards

Mark

[kjbii]

Mark, thanks for your comments, no worries about my thread. I'm looking for the same solution that you describe, ethernet input and the ability to use different DACs in a biamped system with the advantages of Acourate correction and the possibility of adding two or four channels at some later time. The choice of DAC for the bass drivers is not important, it is the requirement of keeping my mid/upper range DAC that is my real concern.

 

Please post your experience with the Hapi, and any further refinements in your plan based on reflection or hard empirical experience.

 

I'm a complete neophyte, and greatly appreciate Keith's and your comments and corrections to rule out dead ends at the planning stage. It's helpful to know that systems 2 and 3 are not useful options, and I will read more about the Hapi and RME HDSPe card system. With luck, you both will have explored these alternatives by the time that I get there.

 

thanks and regards, Ken

[Vassago]

Seems like More than one person in this thread has made multiple Deqx upgrades as new models came out. Is there a Deqx upgrade program?