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Advice for a preamp/DAC build for digital crossover
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Hi! I’m planning to realize a project I have been thinking about some time now and would need some advice on this. I am kind of new to all this so I'm grateful for all comments! For my speaker setup I'd like active crossover (FIR) so my plan is to use a computer based convolution (BruteFIR or perhaps VST convolver). Therefore I also need a preamp and multichannel DAC. My plan is to use Buffalo III with 4 IVY's. I would like several digital inputs: coax, balanced EBU, toslink and I2S (in order to connect a Philips CDpro transport). As an interface to the computer I’ve been thinking about the USBStreamer from miniDSP (actually, I wanted to do the processing without using an external computer but I haven’t found a good way of doing this...do anyone have suggestions?). I also want a display for showing information about volume and selected input and a microprocessor (PIC) for input selection. See the image below:  I have a few questions: - Does it make sense??
- Can one Placid HD be used for powering everything (except the IVY:s)? I need 5V for the PIC pocessor (don’t now about the current it uses). The USBStreamer can run om 5V also and need about 300 mA
- Do I need to put a Metronome somewhere in the signal chain? I think I’ve read somewhere that the I2S output from CDPro isn’t compatible with the DAC?
- The USBStreamer works as a I2S master device only. Would this cause any problem?
- Any other comments/suggestions for this project?
Best regards, Mattias Edited by user Saturday, December 15, 2012 8:45:25 AM(UTC)
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Looks to me like a well thought out system. You will need a second power supply in addition to the Placid HD. I would suggest running the Buffalo III dac board from the Placid HD, and run all the other modules from a LCDPS. One side of the LCDPS set to 5V to power the USB board, OttoII, Teleporter, The optical input board, Metronome (yes you will need that for the CDpro), etc. and the other powering the control modules (PIC, LCD etc). Also 4x Ivy`s may be a bit much for a single Placid HDBP. As far as I can see the only option missing is an analog input. Perhaps a AD converter will be awailable from TPA at some stage. And with that you would get a complete pre with digital cross over from the PC. I have also been looking for a solution to leave the computer out of this as a friend of mine has a 4way system that could realy benefit from a digital cross-over. But atm that is left to an Anthem surround processor. I do not have ice running in my veins so I have not opened that and looked for a i2s signal to tap after the dsp before the DACs. Edited by user Saturday, December 15, 2012 11:22:06 AM(UTC)
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Thank you gkwise, that was really helpful!
Yes, I have been thinking about adding an analog input as well. There is one unused input to the 4:1 MUX, and maybe an AD converter would fit in there . I'll be looking out for an AD converter from TPA then!
In the integration guide I read that a single Placid HD BP could provide power for 4 IVY's, but then a large heatsink would probably be required? Maybe it's safer to use two Placids then?
What would be the right spot for the Metronome? Before the Teleporter, after the Teleporter, after the OTTO II or perhaps right before the Buffalo?
Any thoughts about the USBStreamer working as I2S master?
Thanks again,
Mattias
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A proper AD converter would possibly be with an i2s output, so it would likely mean a second OttoII. At least that is what I would leave room for in the case. I have no experience with the USB solution you are referring to, but are you sure that they are talking about i2s master (signal) and not i2c master (control)? But I have no idea how that card works, so I would ask the developer for help with the integration if I were you. I have seen a couple B3 multichannel setups that otherwise could be helpful for you to read through. http://www.twistedpearau...uild-Considerations.aspxAs well as the blog`s of both glt: http://hifiduino.wordpress.com/ and Corpius: http://ce-designs.net/Corpius had to use the Metronome f.instance. And he used the CDpro2 transport. However, this may not be neccessary due to the fact that you would have the signal route through the USB card. So that would depend on how the USB card is designed.
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Thank you again! Those links were very informative! :) Regarding the USBStreamer the manual states the following: Quote:Note that the USBStreamer can only operate as an I2S Master (clock being outputs from the device). One more thing: can the Placid HD and the LCDPS use the same transformer? By the way, I read in one of those links that the DAC can be used without I/V conversion (with a slightly worse THD+N). Are there any issues regarding this? I'm planning to use Hypex modules as power amps (if that matters). Best regards, Mattias
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Originally Posted by: Crumboo  Regarding the USBStreamer the manual states the following: Quote:Note that the USBStreamer can only operate as an I2S Master (clock being outputs from the device). I think it only matters when the DAC and source work in synchronous mode. Because of the BIII works in asynchronous mode, you just have to connect the following pins: BII --------------- USB J1 expansion connector DCK -------------- 10 - SLCK D1 ---------------- 12 - LRCK D2 ---------------- 1 - Data out Ch 1&2 D3 ---------------- 3 - Data out Ch 3&4 D4 ---------------- 5 - Data out Ch 5&6 D5 ---------------- 7 - Data out Ch 7&8 GND -------------- GND Regards Edited by user Sunday, December 16, 2012 12:39:11 PM(UTC)
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BIII is designed to work with master mode sources.
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Originally Posted by: Amaro
I think it only matters when the DAC and source work in synchronous mode.
Because of the BIII works in asynchronous mode, you just have to connect the following pins:
BII --------------- USB J1 expansion connector
DCK -------------- 10 - SLCK
D1 ---------------- 12 - LRCK
D2 ---------------- 1 - Data out Ch 1&2
D3 ---------------- 3 - Data out Ch 3&4
D4 ---------------- 5 - Data out Ch 5&6
D5 ---------------- 7 - Data out Ch 7&8
GND -------------- GND
Regards
Wow, that was really good info! Can you show the corresponding connections between the S/PDIF 4:1 MUX (or Metronome) and USBStreamer (input)? Best regards, Mattias Edited by user Sunday, December 16, 2012 8:04:03 PM(UTC)
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By the way, I noticed from the Metronome manual that it can be configured to run in other modes than Master, and I guess it should be set to slave mode then in order to work with the USBStreamer (which only works in master mode). I guess I have to disable the internal clock by using the jumper. But what about the switches?
It seems that the correct place for the Metronome should be between the OTTO II and the USBStreamer. It is not clear to me however how the connections should be done.
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I don´t understand the reason of I2S and spdif inputs. I think is better rip yours CD into computer.
However, I think that the way to connect everything is:
usb streamer-metronome-otto II. In an Otto II input plug the MUX4:1, and in the other the Teleporter.
The configuration of Metronome should be:
Put disable jumper.
Mode0 -- 0
Mode1 -- 0
Mode2 -- 1
IFMT0 -- 1
IFMT1 -- 0
IFMT2 -- 0
OFMT0 -- 1
OFMT1 -- 0
OWL0 -- 0
OWL1 -- 0
BYPPASS --0
LDRP -- 0
Metronome PcmOutput port ------- USB J1 Expansion port
BCK ---------------------------------- 10 - I2S System Clock
SCK ---------------------------------- 9 - Master Clock Out
LRC ---------------------------------- 12 - I2S frame synch (LRCKL)
D ------------------------------------- 2- I2S Data In Ch1&2
GND --------------------------------- GDN
Regards
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Thank you so much Amaro! Maybe I'm just old fashioned and like to use the old CD:s I have as they are  but I definitely see your point!
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Originally Posted by: Crumboo By the way, I noticed from the Metronome manual that it can be configured to run in other modes than Master, and I guess it should be set to slave mode then in order to work with the USBStreamer (which only works in master mode). I guess I have to disable the internal clock by using the jumper. But what about the switches?
It seems that the correct place for the Metronome should be between the OTTO II and the USBStreamer. It is not clear to me however how the connections should be done. I don't know about the USB streamer, but when conencting it to the BIII you can set the Metronome according to page 63 of Leon's integration guide. I think that the jumpers override the DIP switches, but I might be wrong. Originally Posted by: Crumboo Maybe I'm just old fashioned and like to use the old CD:s I have as they are I know what you mean. There is something to it... Having to get from the couch to change the disc.  |
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Hi again, Amaro: Just to be sure about this: so the pins 10 (SCLK) and 12 (LRCLK) on the USBStreamer should then be connected to both the Metronome and the BuffaloIII?? "Corpius" wrote:I think that the jumpers override the DIP switches, but I might be wrong. Any input on this from the designer of the Metronome? Oh, and about my previous question: can I use a common transformer for both PlacidHD and LCDPS? Can't wait to start putting it all together! :) Best regards, Mattias Edited by user Wednesday, December 19, 2012 6:52:18 AM(UTC)
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You should use either the switches or the header to control. Using both at the same time is asking for trouble. You could easily create a short. :)
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Originally Posted by: Crumboo Hi again,
Amaro: Just to be sure about this: so the pins 10 (SCLK) and 12 (LRCLK) on the USBStreamer should then be connected to both the Metronome and the BuffaloIII??
Yes, I´m sure. However, try to ask to USB Streamer manufacturer to confirm it. Originally Posted by: Crumboo
Oh, and about my previous question: can I use a common transformer for both PlacidHD and LCDPS?
No. You must use one transformer for Placid and another for LCDPS Regards
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Hi,
I tried the USBStreamer from MiniDSP. It does work but had lots of dropouts. It might work better if you increase the DPLL bandwidth greatly. I did not mess around with it too much. I don't really need 8 channels for now. The Teleporter works better in that respect.
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