# Jambo DAC



## Jambo

Hi Folks,

 I thought I'd share my DAC PCB design with you. Got the PCBs today and have it working in hardware mode.

 The design is as follows: 

 Inputs:
 Burr Brown PCM2707 USB to SPDIF converter
 2 x Optical SPDIF
 1 x Coaxial SPDIF (although I made a mess of the PCB footprint for the RCA socket)

 Outputs:
 RCA
 De-jittered Optical SPDIF

 SPDIF transciever: Wolfson WM8805 (multiplexed version of WM8804)

 DACs: Wolfson 8740/41 in dual differential mode

 Output filters: Analog Devices AD797s

 Control: Xilinx FPGA over I2C bus to WM8805.
 I have the Verilog written for this but underestimated the size of FPGA required so need to get the board re-spun. At the moment the WM8805 is configured in hardware mode (I thought ahead here and provided that option), and receives data nicely from one of the optical inputs.

 NO caps in signal path, plenty of sites for decoupling caps. Pictured below...





 Let me know your thoughts, I'll do a run of these if anyone's interested?

 Cheers...


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## Hoyo

I'm interested


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## d-cee

yeah looks very interesting. how's it sound?

 expected cost?


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## FallenAngel

Sounds interesting, any reason you are using SPDIF for transmission and not I2S?

 A schematic would be really nice to see how everything works together


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## borisov57

Great work Jambo. Maybe you can get same size xilinx with more logical cells?


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## Jambo

Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_Sounds interesting, any reason you are using SPDIF for transmission and not I2S?_

 

Simply because the WM8805 is an SPDIF multiplexer and I wanted Toslink and Coaxial SPDIF it seemed logical to also connect the PCM2707 in this fashion. I2S still runs between the WM8805 and the DACs though. 

  Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_A schematic would be really nice to see how everything works together 
	

	
	
		
		

		
		
	


	


_

 

Sure, I'll get the schems into a nice format and post them....


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## Jambo

Quote:


  Originally Posted by *borisov57* /img/forum/go_quote.gif 
_Great work Jambo. Maybe you can get same size xilinx with more logical cells?_

 

Thanks. I have looked, there is one with a few more but not quite enough, I think respinning the board is the only option! I guess a micro would be a much more cost/space effective way to do this, but I have FPGA/verilog experience so this was the obvious choice.

 Something I didn't explain earlier is that there are headers on the PCB for LEDs and switches to connect to the FPGA for controlling source selection


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## Jambo

Quote:


  Originally Posted by *d-cee* /img/forum/go_quote.gif 
_yeah looks very interesting. how's it sound?

 expected cost?_

 

It sounds great so far! 

 Cost will depend greatly on volume - it has a lot of quite expensive components on it, but if ordered in quantity this comes down a lot.

 I have some ideas for a costed down version too:

 1. Use in hardware mode only - don't need FPGA/PROM and can also get rid of extra toslink/USB circuitry.
 2. Use something other than AD797.
 3. I expect half of the OSCONS could be ditched without a noticeable degredaton in sound quality.
 4. Use WM8740 instead of WM8741 (the WM8741 is hard to get right now anyway, but I have designed this so that both will work and so that the WM8741's digital filters can be used, though WM8741's DSD mode will not work).

 I have acquired an FPGA development board so I am going to test the I2C functionality using flying wires before respinning the board, hope to get that working within the next couple of days.

 Keep the questions coming!


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## naamanf

What about volume control of the DACs?


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## Jambo

Quote:


  Originally Posted by *naamanf* /img/forum/go_quote.gif 
_What about volume control of the DACs?_

 

The DACs are in hardware mode so this feature isn't available yet. But I think I might make it available on the new board revision - would this be useful? I personally prefer to use my amp as my only volume control.


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## naamanf

I think it would be. Then it could also be used with speaker amp that don't have volume control and also ditch volume controls in headphone amps.


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## amb

You would lose bit-resolution with such a volume control, no? That is, if it's done by scaling the digital audio data...


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## Jambo

I have had a quick look at the datasheet and it is indeed done in the digital domain. Although I think I can see what you're getting at, I'm pretty sure the bits aren't truncated at all. Volume control looks easy enough to implement, only the WM8741 supports 2-wire control though, the WM8740 doesn't.


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## aamefford

Jambo, If you are or plan to start keeping a list of interested folks for a group buy once the design is finalized, I am interested, at least one, possibly 2 or 3 boards, and same for any component group buys. Thank you!

 aamefford


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## cgrums

I'd be in for a board or two definitely.


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## kipman725

I'm learing verilog at the moment... finding it slightly dificult to get my head around.. any recomended reading? (my board is an Altera cyclone 2 one). So far all I have manged to code have been replacements for MSI logic chips which use about 0.1% of the FPGA


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## Jambo

aamefford and cgrums, thanks for the interest - I'll keep you posted.

 Currently, I have the FPGA and my board connected up but the WM8805 doesn't want to do what I'm telling it!

 Kipman - there are plenty of books on it, but I always find the best way is just to get stuck in. I still have plenty of learning to do myself, but I'm pretty good on the basics. Something to bear in mind when getting your head round it is that you are coding up hardware, it isn't programming. So the next person to tell you that "Verilog is just like C" should be shot on the spot!


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## Jambo

Hi guys,

 I thought a block diagram would be more useful than the multiple schematics, hopefully everyone can get a better idea of what is going on from this. 








 Oh, and the software control is still not going well! It simulates great but reality, not so much. Will keep trying though!


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## error401

If you really run into trouble with the FPGA (you're right, it doesn't really seem the tool for the job), I've had good success with Peter Fleury's I2C routines for AVR.

 Grab a $2.50 ATtiny2313, avr-gcc, build a cheap parallel port programmer (or a kit) and you should be able to knock something together in a couple hours (assuming you know C). It's really quite fun 
	

	
	
		
		

		
		
	


	




 Looks like a nice idea. Not many DACs actually use the source multiplexers - in fact I was designing one myself the other day (not done yet). Good luck.


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## Jambo

I have messed about in C a fair bit, but my Verilog is much better (or so I thought...). But you're right, from the point of view of cost and board space if nothing else the micro is a much better approach. I guess since I have to respin the board I might as well see how I get on with C, thanks for the links to those routines, will save me a LOT of work!

 Cheers.


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## kipman725

I have used pleanty of PIC microcontrollers and find that programing them in asyembler is far faster and easier than C If you need a high performance micro consider the SX micros (never used on but they are very fast):
Parallax SX - Wikipedia, the free encyclopedia 

 I dunno I have a rather low level mind and think in terms of the bits in registers so asyember is good for me (although the erata and finer points of the data sheets can bite). I managed to get A pic16F84A fast enough to record a PWM bitstream for audio recoding using 18instruction cycles per bit R/W which definatly wouldn't be posible with C (still not fast enough for high fidelity but heh).


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## error401

Quote:


  Originally Posted by *kipman725* /img/forum/go_quote.gif 
_I have used pleanty of PIC microcontrollers and find that programing them in asyembler is far faster and easier than C If you need a high performance micro consider the SX micros (never used on but they are very fast):
Parallax SX - Wikipedia, the free encyclopedia 

 I dunno I have a rather low level mind and think in terms of the bits in registers so asyember is good for me (although the erata and finer points of the data sheets can bite). I managed to get A pic16F84A fast enough to record a PWM bitstream for audio recoding using 18instruction cycles per bit R/W which definatly wouldn't be posible with C (still not fast enough for high fidelity but heh)._

 

You can easily use inline assembly for critical sections or routines in C
	

	
	
		
		

		
		
	


	




. The compiler doesn't do a bad job either, it's smart enough to distill your bitwise statements into single bit set/bit clear instructions if it makes sense.

 PIC assembly is especially strange, I never could wrap my head around it. AVR's more like architectures I used before I got into embedded, so I prefer it - and there aren't wonky memory banks. Plus the C dev tools are a lot more refined and easier to use, and I like C .

 You're right though, for something simple like this it doesn't really matter what you use. I just assumed the OP might be more familiar with, or have less trouble learning C

 Jambo, if you decide to go with AVR instead of your FPGA, drop me a line if you need any help.


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## Jambo

Error401 - your assumption is correct, I'm quite familiar with C,though I've never used it in a microprocessor sense, so small syntax things such as allocation of output pins are confusing me a bit, I think this may be done in the inline assembly that you speak of. Thanks for the offer of help, I will send you a PM if I don't sort it out soon, my Atmel chip should be with me tomorrow and I'll see how I get on.


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## Jambo

Allllright! The micro is setting the WM8805 up in software mode with no problems, just need to get the switches sorted out, watch this space!


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## error401

Quote:


  Originally Posted by *Jambo* /img/forum/go_quote.gif 
_Allllright! The micro is setting the WM8805 up in software mode with no problems, just need to get the switches sorted out, watch this space!_

 

That was quick! Nice work


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## Jambo

Hehe, thanks. Got my head around the i/o pins thing so the switches to mux the sources are working now 
	

	
	
		
		

		
		
	


	




 I'm getting a slight bit of noise when changing sources, I think this must be the WM8805 locking back onto the clocks as it doesn't happen when there is no music... Then again it doesn't happen at startup so I don't really get it. The next board rev will allow me to use the micro to mute the DACs while switching sources, for the best methinks.

 Also need to sort out the USB, think my PCM2707 might be fried.


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## Jambo

Ahhaa... all working! Tomorrow I'm going to add the micro to the schematic/pcb layout and sort out the various PCB issues that I've mentioned so far, and then I'll get some new PCBs. 

 I've got 3 bare boards here that can be easily made to work in an optical>WM8805>dual WM8740/WM8741s>filters> RCA configuration, give me a PM if you want one cheap or hold out for the fully working one.

 Error401 - thanks again for pointing me in the direction of that I2C stuff!


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## lordmozilla

wow i'm interested in this - i'm interested in a group buy for parts too. I'm the uk.


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## Hoyo

Looks like you are making good progress


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## bearmann

hey there! I'm definitely interested in ~2 boards of the next/new charge... as I've seen on the wolfson website, you can order samples online. So probably this could become a decent and (relatively) low-priced DAC! 
	

	
	
		
		

		
		
	


	




 How do you power it up at this time? Don't know how important the power supply on DACs is...

 best regards and keep up that good work! 
 bearmann


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## Jambo

Thanks everyone for the interest.

  Quote:


  Originally Posted by *bearmann* /img/forum/go_quote.gif 
_hey there! I'm definitely interested in ~2 boards of the next/new charge... as I've seen on the wolfson website, you can order samples online. So probably this could become a decent and (relatively) low-priced DAC! 
	

	
	
		
		

		
			



_

 

Cool. We'll see how cheap it'll be, group buying components will definitely help. If I make up build kits (which there does seem to be demand for?), I aim to provide two options, a no expense spared one and a more budget one. An idea I'm having just now is to use OPA134s instead of AD797s - saving there is £14 per board and the specs on the 134 look pretty decent. Anyone have any comments, I've never used the 134? It seems to be pin compatible apart from it lacks the compensation pin that the 797 has but that's easy to deal with.

  Quote:


  Originally Posted by *bearmann* /img/forum/go_quote.gif 
_How do you power it up at this time? Don't know how important the power supply on DACs is...

 best regards and keep up that good work! 
 bearmann_

 

The power supply is pretty important, for prototyping just now I'm using a bench supply that I designed which takes a 12V wall wart supply and using LM317s provides 3.3V and 5V and then a small switcher provides +/-12V. I haven't checked but I'm pretty sure that the TREADS will also work.


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## rustbucket

I don't think this is practical, but I'd love a DAC that had multiple outputs that were switchable - I don't suppose there's any demand for that?


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## MASantos

Quote:


  Originally Posted by *rustbucket* /img/forum/go_quote.gif 
_I don't think this is practical, but I'd love a DAC that had multiple outputs that were switchable - I don't suppose there's any demand for that?_

 

YOu just need to connect the output of the DAC to a rotary switch or a relay based selector like the darwin from twistedpearaudio.com

 No need for this to be in the DAC board.


 Jambo, don't forget that if you go ahead with your idea of selling kits, don't forget to post a mall-fi. They're cheap, you'll get much more attention and salles and still support head-fi! good luck and keep us posted.


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## Cankin

How does it sound? is it comparable to Opus DAC? 
 If yes, I'd like somebody to build me one(depending on the price, of course)


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## noveltone

I'm interested in two boards. Looks great!


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## Jambo

Quote:


  Originally Posted by *Cankin* /img/forum/go_quote.gif 
_How does it sound? is it comparable to Opus DAC? 
 If yes, I'd like somebody to build me one(depending on the price, of course) 
	

	
	
		
		

		
		
	


	


_

 

I've never heard the Opus, but I'd be surprised if it were siginificanlty different. 

 Comparing it to my cheap (single CMEDIA chip) PC sound card is night and day, very very clear, the stereo sounds very wide, bass is tight and there is no background hiss at all when the amp is turned right up. Sorry, I'm not particularly good at hifi speak, but I'm really pleased with it. Compared with my Wharfedale CD player which has a reasonably decent DAC from Burr Brown the differences aren't as great, but it is still better. Obivously this isn't just a DAC though - it has the advantages of multiple source selection and USB input so it's a pretty useful bit of kit.

 Edit: Re building, cool, I will probably offer to solder the ICs for a modest fee if people want, then you could probably manage the rest yourself.


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## lordmozilla

damn wrong thread.

 sorry for not getting back to you. but i decided i'd rather wait for the full thing. Any idea on rough pricing?


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## Jambo

Quote:


  Originally Posted by *lordmozilla* /img/forum/go_quote.gif 
_Hey, i was just looking into this product then came across what you said. How do you change the inputs? This is really interesting to me, in fact this feature will probably mean i'm going to buy one. Please explain how it is done and how easy it is to do. Thanks!_

 

If you look on the second page of this thread where I posted the block diagram, that might help you follow what I'm saying here - picture says a thousand words and all that. The WM8805 is an SPDIF transceiver but it has 8 inputs, I've used 4 of them - USB, Optical x2 and coaxial. The microcontroller (shown as an FPGA on that diagram) receives inputs from momentary switches and then tells the WM8805 which input to choose. I've created the code for this, so it's easy for you! Depending on your idea of what is fun, I could supply the board with the micro soldered and flashed.

 There are headers/solder holes on the PCB for attaching the switches to so that it can be mounted in a case nicely, rather than having the switches on the board and there is a similar header which will drive LEDs to show the current input source.

 I hope that answered your question but if not let me know.

 While I'm here, power supply requirements are +3.3V, +5V and +/- 12V, although I dare say that you could run the analogue stages of the DACs off +3.3V as well thus doing away with the 5V supply, but then there wouldn't be much isolation between analogue and digital supplies.


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## lordmozilla

sorry changed my question since i got the wrong thread. I thought this was about the 707 dac and got really exited since i disregarded it because you couldn't change the inputs. Your product sounds like a winner though


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## dgbiker1

Sorry guys, noob question. What is I2C? Based on your block diagram I'm guessing that's just a control signal from the FPGA to the Wolfson for switching inputs?


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## Jambo

Yup exactly, stands for inter integrated circuit if i remember correctly. It's a two wire interface, devised by Phillips I think. It's quite cool because each device has a unique address, so you don't need chip select wires.


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## n0ll4k

Looks very nice. 
 At the moment I am looking for a inexpensive USB DAC and this looks very interesting. 
 If there ist a group buy I am definatly interested in a board.


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## Jambo

Quote:


  Originally Posted by *lordmozilla* /img/forum/go_quote.gif 
_damn wrong thread.

 sorry for not getting back to you. but i decided i'd rather wait for the full thing. Any idea on rough pricing?_

 

The full thing will be rather cool 
	

	
	
		
		

		
		
	


	




 I've just been doing some rough pricing. If ten people will commit and my Excel sheet is correct, kit prices should be no more than £70 (~$140). 25 kits and it gets close to £60 (~$120). That's parts and PCB, however I decided not to include LEDs or switches in the pricing as I thought people would probably want to do their own thing - how's that sound?

 I'd be prepared to solder all of the ICs and flash the micro for around £10, assembling the whole thing could be negotiated too, but that takes a lot of the fun out of it...


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## lordmozilla

If you can keep the price equal to the DAC super pro 707 shipped with IC's soldered and micro flashed, then you got my money  (its £70 shipped to the UK)

 Are you in the uk? Also will this thing need an external power source or will usb be feeding it +5V ?

 lastly, when do you reckon you'll get the first kits ready?

 Thanks
 Brendan


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## Jambo

I am in the UK yes, and I have no intention to profit from postage charges, they will not be above cost.

 I should point out that that price above was using OPA134s in the output stage, not the AD797s. I think they're just going to be too expensive, but I'll offer both options or people can buy their own amps.

 RE the DAC Super Pro 707... I just had a quick read of a web page about it and can't figure out if the Optical/Coaxials are inputs or outputs? Anyhoo, my DAC has much much better components in it than that does, so it sounds better (I hope) and as such costs me more so unless we get into serious volumes I can't see that target being met. I'm confident it'll be worth the extra cash.

 USB power doesn't cover this unfortunately. You'll need to make/buy/rip out of an old cd player... a +3.3V, +5V, +/-12V supply. Depending on the success of this I might design a power supply next...

 I hope to get a couple of prototype revised boards here within the next fortnight. Once they're tested I'll make any corrections necessary and order a larger number which should be here within a fortnight of then. So, around a month I hope.


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## naamanf

What DAC chips are you planning on including?


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## Jambo

Those prices are for the WM8740 - the board is compatible with the WM8741 but it's hard to get hold of. It is also ~3x the price of the 8740...


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## sid_

I'm very keen on getting one of these. I'd love to see this as a full kit for both the DAC and, if we're lucky, a matching power supply 
	

	
	
		
		

		
			





 I'm no electronics expert, but I would be interested in having a look at the full schematics if you were willing to make them available.


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## Jambo

I'll see what I can do on the power supply front - I guess it's a bit of a chicken and egg situation with that really...

 Yeah, I'm happy to make the schematics available though I'd rather tidy them up first!


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## bluemoon

Im interested in a board when the design is finalized, from the specs it should sound awesome


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## lordmozilla

I've just got hold of a nice case and a powersupply, It's off an old mini-itx system, so should be able to provide ample 3,3V, 5V and 12V in large amounts. I'm also guessing the power would be quite stable and clean, am I wrong in this assumption?

 Are pc power supplies not very clean or are they pretty good?


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## Jambo

I have never used a PC power supply for this sort of thing, but I haven't heard great things about them. Remember you also need -12V which I don't think you can find inside a PC.

 However, you could make it work... I have used this part with a lot of success for easily generating -12V from +12V: C&D NMA1212SC

 It's obviously switched mode, so some people will complain at that but I certainly can't hear any problems with it. It only powers the output stage and the PSRR of opamps is generally pretty awesome. I have actually tested this part on an AP2700 in the past powering a similar circuit with no change in THD+N readings compared to a bench supply.

 The DACs are another story. For the WM8740, AVDD (5V) needs to be very stable (see if you can find PSRR on the datasheet!). The WM8741 however has a pretty good PSRR so if we can get hold of them it is less of a concern.

 You could rig up some linear regulators on the output of your PC supply to get it a lot cleaner.

 A bit of an update on the project as a whole.... I have re-done the PCB layout to get everything on a nice big ground plane as best as I can. This was a bit of a challenge as there is a hell of a lot of routing required, but I think it's as good as I can get it. 

 I have also added the microprocessor. I haven't added the software control for the DACs mostly because the WM8740 doesn't support I2C. I have however added a header for the WM8741 digital filter selection which could be wired to a switch.

 The incorrect footprints have been fixed (I hope!) and a few other things have been tidied up, I hope to send the PCB files off within the next couple of days so should have the (hopefully final) prototype here in a little over a week 
	

	
	
		
		

		
		
	


	




 Also... this thing needs a better name!


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## lordmozilla

thanks for the reply, a pc powersupply does have -12V (1A of it usually - so should be plenty).

 Computer PSU's are usually very stable in the 5V and 3,3V, less so in the 12V department from my experience, but since the loads would be very minimal, i would not think the 12V would be unstable.

 I'm guessing the exact voltage of the 5V rail doesnt matter so much, but it's stability does? Here is a typical fluctuation graph for 2 quality PSU's
Review of the SilverStone Tek ST46F Power Supply

 Usually voltage on the 5V rail doesnt fluctuate more than 0.03V either side at worst. Would this be bad for the DAC?

 I found the datasheet for the WM8740 and it recommends 10% either way for the 5V input to the chip. 
WM8740 Datasheet pdf - HIGH PERFORMANCE 24-BIT, 192KHZ STEREO DAC - Wolfson

 I couldn't find the PSRR - whatever that is.

 It even states under extreme conditions the unit can go up to -0.3V to 7V without damage. 

 Good to know you are making good progress, as for a better name, I kinda like Jambo DAC...


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## tomb

The problem is not with stability with a switching supply - switching noise is the issue. That noise is audible and is often magnified to the point of being unusable in a quality audio circuit. There are exceptions, to be sure, but the choice for linear regulation is often preferrable.

 Note that even with USB power, the choice is usually to linear regulate with another chip (REG101, REG102 as in the Alien) in supplying a DAC.


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## Jambo

Quote:


  Originally Posted by *lordmozilla* /img/forum/go_quote.gif 
_thanks for the reply, a pc powersupply does have -12V (1A of it usually - so should be plenty)._

 

Oh right, nice - sorry I didn't realise that. Yes, 1A is more than enough, the output stage should only be using in the 10s of mA.

  Quote:


  Originally Posted by *lordmozilla* /img/forum/go_quote.gif 
_I'm guessing the exact voltage of the 5V rail doesnt matter so much, but it's stability does? Here is a typical fluctuation graph for 2 quality PSU's
Review of the SilverStone Tek ST46F Power Supply

 Usually voltage on the 5V rail doesnt fluctuate more than 0.03V either side at worst. Would this be bad for the DAC?
_

 

Yes, the absolute value is not important (within limits) but the ripple that is present on it is - stuff such as switching noise as stated by Tomb. The fluctuations that you describe are not important as they happen over relatively long periods of time. We are more concerned with high frequency AC components imposed on the DC supply.

  Quote:


  Originally Posted by *lordmozilla* /img/forum/go_quote.gif 
_I couldn't find the PSRR - whatever that is._

 

It stands for Power Supply Rejection Ratio. It is a measure of how robust a component is to power supply ripple. Probably the easiest component for visualising this is an amplifier configured as a buffer (gain of 1). Say it has a 2V DC input, and then a 20mV 1kHz signal is superimposed onto the positive power supply rail. If we then look at the output, in an ideal world we would see the same 2V DC value as was applied to the input, and no AC component. This would give an infite PSRR as power supply variations aren't affecting the output. If however, we saw 2V DC + 20mV 1kHz on the output, the PSRR would be non existent, or 1, or 0dB. If we saw 2V DC + 10mV 1kHz, the PSRR would be 2, or 6dB. The same situation exists with DACs but it is easier to think about with amps. Hope that makes some sense?

 The WM8741 has 80dB PSRR at 1kHz which means that 1V of power supply noise will be seen as 0.1mV of noise on the output.


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## lordmozilla

Cheers for that, as you can probably tell my electronic knowledge is very very limited. So I guess even a pc psu has to be regulated. 

 Would a PSU of a cdp work then? I have a cambridge audio CD34 that I don't use and i'm trying to sell but I could just rip the PSU out and use that ? Do all CDP PSU's have the required voltage rails in sufficient amounts?


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## Jambo

Yeah I think that would be a better start. Erm they vary, I just looked at one that I have here and it has +/-12V and 5V, but not 3.3V, so you would need to derive that somehow if using this one. I would say that they will all have the necessary current capability though. Try opening your CD player up, often when there is a separate power supply board, you'll see the voltages marked on the silkscreen of both boards.


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## lordmozilla

thanks, I'll go and see tonight what the PSU of the CDP looks like.


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## Jambo

Hi RFL,

 The WM8805 is a superior receiver to the Cirrus part in the DAC super pro. My design uses two DAC chips in a dual differential configuration too, so whether or not you feel the WM part is better than the CS one, this is a funky implementation. It is also an expensive one.

 I have no experience of how the LT1364 compares to the AD797, but the AD797 is significantly more expensive and due to the context of the above post I was using a more expensive = better approach which I appreciate is rarely the full story.

 Putting some finishing touches to the PCB layout just now... think I'll send it off tonight otherwise I'll start making a mess of it!


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## lordmozilla

hey, just opened up the CDP, and the rails off the PSU are :
 +5V
 +5V
 GND
 +9V
 -9V
 MIC
 GND

 also there is :
 -24V
 AC3.3
 AC3.3
 GND

 AC3.3
 AC3.3
 AC4.7
 AC4.7
 AC13
 GND
 AC13

 So i guess I've only got the +5V, thats alot of voltages missing. What do you think?


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## Jambo

PbFree, thank you for your opinion, but please do not state it as if it is fact.

 Lordmozilla - sorry for the delay in getting back to you. You have 5V so that's fine, I reckon the output stage would be adequately powered by +/-9V though I'd have to double check. You could use an LDO to derive 3.3V from one of the 5V rails quite easily.


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## FrederikS|TPU

How much do you think a complete DAC based on your design would cost all parts included except chassis?

 If it is a cost effective design then I am definitely interested.


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## Jambo

Well, I think the DAC kits will be coming in at around £70-80. 

 Then for a power supply, make a pair of TREADS for the 3.3V and 5V and power them from a wall wart, and put a NMA1212SC on the same board to generate +/- 12V, that wouldn't cost much. Also Frederick I guess you can do quite well out of the £'s current weakness against the Euro!

 I will do my best to make a power supply for this, but I need to do some reading first. I also need to recoup some funds, a student budget doesn't really lend itself to this kind of R&D!

 Quick update on the project... Parts are here for another build, and I'm told that two of the new prototype PCBs will ship out to me on Friday, so I'll have them early next week, whooop!


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## Marzie

This sounds interesting, I will be watching this thread. Please PM me if/when a group buy is going to happen or if you decide to offer kits. Also, an up to date bom would be nice, just to get an idea of the parts cost.


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## jgonino

This is the perfect DAC for me! Only one other question:

 Would it be possible to have 2 or 3 switchable RCA-outs?

 PM me when/if you are planning a group buy.


----------



## Calroth

I can't exactly see how your output circuit goes, but since it's a WM8740, I presume it can be tweaked (for a given level of "tweak") for balanced output?


----------



## Jambo

Quote:


  Originally Posted by *jgonino* /img/forum/go_quote.gif 
_This is the perfect DAC for me! Only one other question:

 Would it be possible to have 2 or 3 switchable RCA-outs?

 PM me when/if you are planning a group buy._

 

Thanks for the continued interest guys - will PM you all. BOM and schematics will follow soon!

 I have no plans to have switchable RCAs I'm afraid.

 Calroth - You could extract balanced output perhaps from some vias on the PCB but it was not designed with this in mind. I don't have any balanced equipment and I originally designed this for myself, so that is why! There also is no room on the PCB for XLRs.


----------



## Calroth

Quote:


  Originally Posted by *Jambo* /img/forum/go_quote.gif 
_Calroth - You could extract balanced output perhaps from some vias on the PCB but it was not designed with this in mind. I don't have any balanced equipment and I originally designed this for myself, so that is why! There also is no room on the PCB for XLRs._

 

Oh, 'twas just a passing fancy, sparked by the idea of building this bad boy. I guess it could be possible to re-wire the entire output stage from the DAC chips onward, just by hooking on to their tiny tiny legs. But, again, it's more of a fancy than anything grounded in reality, and I'm sure your design will be awesome either way


----------



## Jambo

I just finished building one of the newest boards, I put WM8740s on this one and OPA134s on the outputs and it still sounds great. I haven't AB'd it with the other one though. This has all of the improvements I was looking for though, micro now sits on the board etc. I have a LOAD of uni work to do over the next fortnight but after that I have a good few weeks which I can spend pretty much full time on kits so if anyone interested hasn't spoken out yet, get in touch. Here's a pic of the assembled board:


----------



## fault151

How much you charging for the dac?


----------



## lordmozilla

that looks lovely! Nice work,

 How is the input switching done?


----------



## Jambo

Fault151 - I've indicated what I think it will cost a few times on the previous pages, I'm looking to finalise that pretty soon, but I need an indication of volumes as it makes a big difference.

 Lordmozilla - thanks 
	

	
	
		
		

		
		
	


	




 See the set of 8 header pins near the bottom left? 4 of them are grounds, the other 4 tell the micro to switch to the relevant source when grounded. I've been touching a jumper across the pins for testing, but when you build it into a case, you would attach four momentary switches to do this nicely. 

 Then the eight holes half way up the left edge where I haven't soldered anything, they are for the LEDs to indicate the current input source. Below that are two more grounds and two more micro pins which as yet aren't used, but I have an idea for that 
	

	
	
		
		

		
		
	


	




 Oh, and there are two more holes to the right of the switch headers which are attached to the 3.3V supply and ground, I thought that would be useful for a power indicator or something.

 Any more questions, just let me know.


----------



## Marzie

Any new info? I had a dream the other night that I went into a local electronics supply shop and found a kit right on the shelf for the Jambo DAC, parts, boards, everything... I think its a sign...


----------



## sid_

Quote:


  Originally Posted by *Marzie* /img/forum/go_quote.gif 
_Any new info? I had a dream the other night that I went into a local electronics supply shop and found a kit right on the shelf for the Jambo DAC, parts, boards, everything... I think its a sign..._

 

Jambo has already said that he is going to put kits together but that he's busy with coursework for university for the next few weeks - so everyone will have to wait until then.

 You should let him know that you'd like a kit when they're available - the more people that want one, the cheaper it should be.


----------



## fault151

Quote:


  Originally Posted by *lordmozilla* /img/forum/go_quote.gif 
_that looks lovely! Nice work,

 How is the input switching done?_

 

I might order one if you were on about the group buy. Im also in the UK.


----------



## d-cee

I'd be interested in a kit as well, count me in!


----------



## Jambo

Quote:


  Originally Posted by *Marzie* /img/forum/go_quote.gif 
_Any new info? I had a dream the other night that I went into a local electronics supply shop and found a kit right on the shelf for the Jambo DAC, parts, boards, everything... I think its a sign..._

 

Haha... nice.

 As imported_sid says, I'm quite busy just now, or at least I should be, but I'll get it done ASAP. 

 In the mean time, I've attached the schematics, comments welcome.

 Cheers

 Jamie.


----------



## Jambo

Just discovered that the Micro operates by default without the crystal, DOH! Oh well, that lot can be unpopulated and take 30p off the cost...


----------



## Marzie

NP, I know how it can get with school, I'm glad to be done. I am still trying to make sure I have enough funds and courage to try SMD soldering. My hands shake like an old mans... Speaking of funds...

  Quote:


  Originally Posted by *Jambo* /img/forum/go_quote.gif 
_Just discovered that the Micro operates by default without the crystal, DOH! Oh well, that lot can be unpopulated and take 30p off the cost..._

 

Is that 30 p as in pounds? So that would be around $50 GBP or so (or $100 USD)? If so, then I am definitely in for a kit, probably the lower end version, depending on the price difference between the two (if you still plan to offer two versions) plus any of the SMD soldering you would be willing to do, I would be willing to go in for that also. I am considering the "completed version" you talked about, but definitely the ICs.

 I'm also wondering about an enclosure, did you size the board to fit into any of the Hammond's? Or do you have you given any thought to panels? I know I am putting the cart before the horse here, so don't feel rushed by me, but any of this would be useful, should you decide to design anything like that.

 EDIT: And I do hope we are lucky enough to get a power supply...


----------



## nine

This sounds like a great project. I'll definitely be interested in a kit when they're available.

 nine


----------



## bowraboy

I am also interested.


----------



## FallenAngel

Quote:


  Originally Posted by *Marzie* /img/forum/go_quote.gif 
_Is that 30 p as in pounds? So that would be around $50 GBP or so (or $100 USD)? If so, then I am definitely in for a kit, probably the lower end version, depending on the price difference between the two (if you still plan to offer two versions) plus any of the SMD soldering you would be willing to do, I would be willing to go in for that also. I am considering the "completed version" you talked about, but definitely the ICs._

 

Lol, keep dreaming, I think that's 50 cents, a crystal doesn't cost that much 
	

	
	
		
		

		
		
	


	




 But it does look like a nice project, nice multi-input DAC, good luck with getting it produced, I'm definitely following this thread


----------



## lordmozilla

ahaha p is abbreviation for pence. not pounds. pounds is £


----------



## Jambo

Quote:


  Originally Posted by *Marzie* /img/forum/go_quote.gif 
_Is that 30 p as in pounds? So that would be around $50 GBP or so (or $100 USD)? If so, then I am definitely in for a kit, probably the lower end version, depending on the price difference between the two (if you still plan to offer two versions)plus any of the SMD soldering you would be willing to do, I would be willing to go in for that also. I am considering the "completed version" you talked about, but definitely the ICs._

 

Afraid Lordmozzilla is right, the price difference is going to be negligible! I changed my second board to AD797s over the weekend which has had a marked improvement in the clarity of the high end (could easily be placebo though, I haven't been able to A/B), so I would recommend these over the OPA134s. Can someone recommend an opamp that is somewhere between these two in performance but much cheaper than the 797?

 Been thinking about SMD soldering... I'm not bad with ICs but the problem is that with 7 of them on one PCB, there is bound to be a bridge/dry somewhere and they're hard to test for without being able to fire up the board. So currently I'm giving serious thought as to whether or not I want to send out partially built boards - anyone got any opinions on this?

  Quote:


  Originally Posted by *Marzie* /img/forum/go_quote.gif 
_I'm also wondering about an enclosure, did you size the board to fit into any of the Hammond's? Or do you have you given any thought to panels? I know I am putting the cart before the horse here, so don't feel rushed by me, but any of this would be useful, should you decide to design anything like that._

 

No thought to doing panels I'm afraid - remember this is a project I initially did for myself, I just tested the water here and since there was interest I'm going to let it evolve into something bigger... Maybe one day but it's well down the list... The board is sensibly designed though - all I/O connectors are on one edge of the board, power connnection is on the opposite side. The board is 5.5 x 4 inches - does that work? This does remind me that I'm yet to put my own one in a box


----------



## error401

Quote:


  Originally Posted by *Jambo* /img/forum/go_quote.gif 
_Afraid Lordmozzilla is right, the price difference is going to be negligible! I changed my second board to AD797s over the weekend which has had a marked improvement in the clarity of the high end (could easily be placebo though, I haven't been able to A/B), so I would recommend these over the OPA134s. Can someone recommend an opamp that is somewhere between these two in performance but much cheaper than the 797?_

 

Maybe LME49710. On price it competes directly with OPA134, but I like it much better. Specs are quite a bit better than OPA134 as well.

  Quote:


 Been thinking about SMD soldering... I'm not bad with ICs but the problem is that with 7 of them on one PCB, there is bound to be a bridge/dry somewhere and they're hard to test for without being able to fire up the board. So currently I'm giving serious thought as to whether or not I want to send out partially built boards - anyone got any opinions on this? 
 

IMO if you can't test it, you shouldn't offer it this way, it'll just be a hassle for you and people that buy from you. Personally I don't think I'd offer pre-soldered parts unless I could set up a reflow setup.


----------



## Marzie

Quote:


  Originally Posted by *lordmozilla* /img/forum/go_quote.gif 
_ahaha p is abbreviation for pence. not pounds. pounds is £ _

 

LOL, well I can hope, can't I? 
	

	
	
		
		

		
		
	


	




 I understand what you are saying about the SMD soldering and I can respect that. I don't want you to feel like you are forced into become a vendor or having to spend all your free time doing this, that could easily sap all the "fun" out of a nice project like this. When I was "in business" for myself, it felt as if the demand was so great that I would be a fool not to take advantage of the market. After having almost all my free time dominated by this, I really lost all interest that I had in it to begin with.

 But keep going with it! It still sounds much cheaper than going with an Opus, when you consider 2 optical, 1 coax, AND a USB.


----------



## lordmozilla

uhm, doing the SMD soldering myself would definately be an experience but I'm not sure if the board would agree. 

 But it's your decision, I can see why you wouldn't want to do it. I for one would find it very hard to solder the board completely myself.


----------



## Jambo

Thanks for the opamp suggestions error401. 

 Been thinking some more about the partially built boards... I totally understand why people find SMD IC soldering intimidating, I did too until very recently. I'm glad people also see my reasoning for not wanting to send out boards that I can't test. So, a compromise I thought of... I could solder all ICs and flash the micro, also solder on the USB socket and all configuration (pull up/down) resistors. That would allow me to test that the USB path works and the rest should also then work. That still leaves the owner the through hole connectors, decoupling caps (through-hole and 0805 SMD) and output filters (0805 SMD and 1x 0603) to solder. Any thoughts on this? I think it's a good compromise between making the kit still a DIY job but the chances of new comers getting it working first time are still pretty high.


----------



## Marzie

That sounds good to me! If you are up to it, of course. If there is a problem (which is what I imagine you are worried about, an unhappy customer can make for a real PITA...) troubleshooting should not be difficult, considering that the real "meat" has been tested already...


----------



## lordmozilla

Quote:


  Originally Posted by *Jambo* /img/forum/go_quote.gif 
_Thanks for the opamp suggestions error401. 

 Been thinking some more about the partially built boards... I totally understand why people find SMD IC soldering intimidating, I did too until very recently. I'm glad people also see my reasoning for not wanting to send out boards that I can't test. So, a compromise I thought of... I could solder all ICs and flash the micro, also solder on the USB socket and all configuration (pull up/down) resistors. That would allow me to test that the USB path works and the rest should also then work. That still leaves the owner the through hole connectors, decoupling caps (through-hole and 0805 SMD) and output filters (0805 SMD and 1x 0603) to solder. Any thoughts on this? I think it's a good compromise between making the kit still a DIY job but the chances of new comers getting it working first time are still pretty high._

 

That sounds perfect, I mean i've done a bit of SMD soldering before but only a few resistors, so if you've at least tested most of the more complicated chips it would definately help me out!

 Sounds like a good compromise!


----------



## Jambo

Thanks for the responses - glad you think it's a good idea.

 I've pretty much finished up at uni now so going to get on with this. I have a couple of very small changes to make to the board, then I'm going to get a reasonable number of them made. 

 Currently working on a user manual and a couple of different versions of the micro code.


----------



## pistolpete111

Sounds like a great project. I'm interested in getting 2 kits!


----------



## pistolpete111

Jambo - I have a couple of questions about your DAC:

 1) Is there any concern about going from USB->SPDIF->I2S? I guess there shouldn't be any disadvantage to this but you know more about this stuff than I. 

 2) Would it be possible for the boards to have a layout where using more of the inputs on the 8805 could be optional? So say, some day if I have a need for a few more TOSLink sockets, i could just add them to the existing board?

 Sounds like a great project anyway - hope your work on it is coming along nicely 
	

	
	
		
		

		
		
	


	





 Thanks,

 Pete


----------



## Jambo

Hi Pete,

 1) Yes, some people find this a concern - they suggest that the SPDIF interface is more prone to jitter. Also, since the USB standard for audio is I2S (someone correct me if I'm wrong), it does seem odd to go from USB (I2S) to SPDIF to I2S again - it clearly can't do anything positive to the signal. 

 However, I wanted a USB input and coaxial/optical inputs and the WM8805 is a nice SPDIF multiplexer so this seemed the natural route. Also, the WM8805 is superb at recovering the I2S signals with very high jitter rejection, so I am quite confident that any impact on the signal will be small - it certainly sounds good to me. The only alternative that I can see is to have used an FPGA as a multiplexer between the SPDIF receiver and the DACs to switch the I2S signals around. I personally didn't feel that this would be worth the effort and extra cost.

 2) I'll look into this - microprocessor pins may be the limiting factor assuming that we want an LED and switch for each source, but I'll see what I can do. I also need to check just how much space I have along the edge of the board where the connectors are.

 Hope this helps,

 Jamie.


----------



## FrederikS|TPU

This is going to be one killer DAC. And for under £100 it is going to be hard to beat. I am so looking forward to seeing a final version, perhaps with a nice enclosure as well!


----------



## CountChoculaBot

How much more does a kit cost with the WM8741 instead of the WM8740? Also, is the 8741 a significant SQ improvement over the 8740?


----------



## pistolpete111

Quote:


  Originally Posted by *CountChoculaBot* /img/forum/go_quote.gif 
_How much more does a kit cost with the WM8741 instead of the WM8740? Also, is the 8741 a significant SQ improvement over the 8740?_

 

The overall kit cost has not been decided yet as far as I know. The current problem with the WM8741 is that it is generally not available yet. Some of them exist, but from what I can see, they are not available to order yet.

 When they do go on sale to the general public, I think I read somewhere their price will be 3 times that of the 8740. Although I have not heard the 8741 yet, its spec sheet makes it look like a significant improvement over the 8740. Although, in practice I guess the improvement will be hardly audible. I guess it depends on the rest of the components in your DAC. The 8741 offers 128dB SNR as opposed to the 8740's 120dB SNR (and it has a few more advantages too). While that value sounds huge, i'd expect that unless your using the highest quality of PCB, and components on it, with a very careful design, and have a serious hifi setup, the difference will not be that big - I guess we'll have to wait and see. As the chip is not available yet, I'm really only guessing right now.

 The two chips are pin-compatible, so if you went with the 8740's now, you could upgrade them in the future with no other changes required to the DAC.

 Pete


----------



## Jambo

Spot on Pete - the Wolfson site lists the 8741 at around $15 while the 8740 is listed at around $5, so since the kit needs two the difference will be of the order of $20. Also as Pete correctly said, the problem at the moment is getting hold of these, but the kit will definitely work with them and has the ability to switch the switchable digital filters.

 Interestingly the WM8741 actually has worse THD than the WM8740, but as we all know music is not a 1kHz sine wave... The filters do a nice job of reducing pre ringing but whether it's worth the extra cash is up to you...


----------



## Marzie

Jambo, this might be a little nit picky but I like the look of these panel jacks (the analog rcas) a little better,although the ones you selected may be fine, I see a little black in the first picture, I just don't like the plasticky white look. Actually the black pcb is pretty cool too, but that adds to the cost, I'm sure... anyway, how are things coming?


----------



## Jambo

Hi Marzie,

 Thanks for the suggestion. As you say though, there is actually some black on them and you could easily make a case capable of hiding the white altogether. Also I really don't want to change this aspect of the PCB as knowing my luck I won't get it right first time and I've spent enough on prototype runs so far! I've got a better pic of the jacks for you:






 As for how things are going, I'm currently trying to resolve a small software issue. When changing source, about 1 time in 10 the DACs fail to mute and there is a horriffic noise through the outputs. The other 9 times, the DACs mute nicely and the source changes and they come back up again. If anyone with some software knowhow has any ideas why this may be, they'd be gratefully received!

 Here is a sample bit of code for looking at the switches:

  Code:


```
[left]if (bit_is_clear(PINB, 3) && (current_src != 3)) { for (counter = 0; counter <= mute_time; counter++) { PORTD &= ~(1<<1); // Mute DACs } //SPDIF source = 011 i2c_start(WM8805+I2C_WRITE); i2c_write(0x08); // write address = 08 i2c_write(0x1B); // data = 1Bh i2c_stop(); // stop, release bus current_src = 3; //put on corresponding LED: PORTB = 0x8f; // source 3 - output 3 on; inputs with pullups. for (counter = 0; counter <= mute_time; counter++) { PORTD &= ~(1<<1); // Mute DACs } PORTD |= 1<<1; //unmute DACs } else {//no change in source, move on... counter = 0; //do something useless }[/left]
```

I know I haven't done a lot to deal with switchbounce, but my feeling is that the opening 'if' means that this is only ever executed once and the 'if_bit_is_clear' decision decides that the switch is or is not pressed, after that it should be immaterial. Oh, also, the two 'for' loops is just me trying stuff to try and make it work, there was originally only one.

 I have considered that it may be due to the optimiser removing what it considers to be useless instructions, but then I think the mute would fail every time.

 As I have said, my C and, in particular, microprocessor knowledge is limited so any advice gratefully received!

 A second issue is what looks on the face of it to be oscillation at the output filters. When probing the outputs with no music, I can see a sine wave of a few 10s of mV in the 10's of MHz region. I am convinced that this is being caused by the capacitance of my cheap 'scope probe - i.e. it isn't there unless I'm looking for it! It only happens with the AD797, not the OPA134. I am further convinced that it is caused by the probe since changing the probe to x10 mode (this changes the capacitance of the probe) changes the frequency and amplitude of the oscillation - the amplitude isn't changed by the factor of 10 expected, it is much less. Anyone got any views on this? As I say, I'm fairly sure it is caused by the probe so it isn't a problem, but I don't want to pass this problem onto other people until I'm certain!


----------



## error401

Quote:


  Originally Posted by *Jambo* /img/forum/go_quote.gif 
_Here is a sample bit of code for looking at the switches:

  Code:



		Code:
	

[left]if (bit_is_clear(PINB, 3) && (current_src != 3)) { for (counter = 0; counter <= mute_time; counter++) { PORTD &= ~(1<<1); // Mute DACs } //SPDIF source = 011 i2c_start(WM8805+I2C_WRITE); i2c_write(0x08); // write address = 08 i2c_write(0x1B); // data = 1Bh i2c_stop(); // stop, release bus current_src = 3; //put on corresponding LED: PORTB = 0x8f; // source 3 - output 3 on; inputs with pullups. for (counter = 0; counter <= mute_time; counter++) { PORTD &= ~(1<<1); // Mute DACs } PORTD |= 1<<1; //unmute DACs } else {//no change in source, move on... counter = 0; //do something useless }[/left]


I know I haven't done a lot to deal with switchbounce, but my feeling is that the opening 'if' means that this is only ever executed once and the 'if_bit_is_clear' decision decides that the switch is or is not pressed, after that it should be immaterial. Oh, also, the two 'for' loops is just me trying stuff to try and make it work, there was originally only one._

 

Just a small comment: you really should generalize this function and have a separate function scanning the inputs and figuring out which SPDIF address to send to the WM8805. Then you just need a select_input(3) call, and one block of code that looks like this instead of 'n' blocks that are almost identical.

 Otherwise your code seems fine to me. I believe you're probably just unmuting too soon. The receiver PLLs will take some time to lock to the new signal. There is an UNLOCK flag available in WM8805, it can be mapped to a GPO or read as a register. It can also generate an interrupt when lock is acquired.

 If you're not monitoring the receiver status, you'll need to wait a while, definitely longer than 255 cycles - and I think the compiler is smart enough to simplify those loops to a single statement anyway. If you #include<util/delay.h>, avr-libc provides timed busy-waits for you in _delay_us(double) and _delay_ms(double). Read the manual for them because there are limits (max of 32ms delay with 8MHz clock), and make sure you set F_CPU properly. That'll be a little nicer than looping a bajillion times.

 Finally, the compiler can generate assembly output you can read and make sure the optimization isn't doing anything funky.

 As for switch debouncing, it shouldn't be much of a problem with this approach since so much happens between detecting the initial event and checking again. The I2C transfer alone probably takes long enough to deal with switch bounce. You need more robust switch handling if you're using interrupts for input or scanning the inputs quickly enough to catch the bounces; I don't think that will be the case here. Worst case, if you do have problems, just add a few ms delay after handling the input.


----------



## sleepy dan

Hi Jambo, looking at your schematics, I couldn't see any resistive buffering on the outputs of the AD797s. Adding an R of ~100 ohms may stop the ringing.


----------



## Jambo

Error401 - thank you for your helpful response once again.

 You're quite correct - my coding style leaves a lot to be desired.

 I have tried using the UNLOCK flag available as GPO1 to mute the DACs while the WM8805 is upset. Unfortunately however the noise still occurs sometimes - I guess that means it must be coming from the DAC....?

 Using fixed delays, it usually works fine and the output is silent for an appreciable amount of time. But when the noise occurs the delay/mute just doesn't happen - the music starts straight away with the fuzz over the top.

 I have tried to use delay.h already, but I found that (since it turns the optimiser off) the code then ended up far too big for the ATTiny2313.

 I'm sure it'll be something simple once I eventually find it!


----------



## Jambo

Tidied it up a bit 
	

	
	
		
		

		
		
	


	




  Code:


```
[left]int spdif_select(int next_src, int current_src, int mute_time) { unsigned int counter; if (current_src != next_src) { PORTD &= ~(1<<1); // Mute DACs for (counter = 0; counter <= mute_time; counter++) { PORTD &= ~(1<<1); // Mute DACs } //I2C writes to change SPDIF source i2c_start(WM8805+I2C_WRITE); i2c_write(0x08); // write address = 08 i2c_write(0x18 + next_src); // data = 0x18h + next_src i2c_stop(); // stop current_src = next_src; //put on corresponding LED: PORTB = (0x0f + (1<<(next_src+4))); for (counter = 0; counter <= mute_time; counter++) { PORTD &= ~(1<<1); // Mute DACs } PORTD |= 1<<1; //unmute DACs } else {//no change in source counter = 0; //do something useless } return current_src; }//end spdif_select[/left]
```

It behaves the same as before but uses a good bit less of the memory, nice. 

 I'm going to get the scope out at some point and check if the mute pin is actually being pulled low when the filthy noise occurs, I can't help but feel that the DACs are choosing to ignore it!

 sleepy_dan - thanks for the idea, I'd rather avoid this if possible though. As I say, I'm confident that it's the scope probe just wondering if anyone has seen this sort of thing before?


----------



## willisv

I am interested in a kit!


----------



## error401

Quote:


  Originally Posted by *Jambo* /img/forum/go_quote.gif 
_Error401 - thank you for your helpful response once again.

 You're quite correct - my coding style leaves a lot to be desired.

 I have tried using the UNLOCK flag available as GPO1 to mute the DACs while the WM8805 is upset. Unfortunately however the noise still occurs sometimes - I guess that means it must be coming from the DAC....?

 Using fixed delays, it usually works fine and the output is silent for an appreciable amount of time. But when the noise occurs the delay/mute just doesn't happen - the music starts straight away with the fuzz over the top.

 I have tried to use delay.h already, but I found that (since it turns the optimiser off) the code then ended up far too big for the ATTiny2313.

 I'm sure it'll be something simple once I eventually find it!_

 

In that case I'm not really sure what else to suggest. Verify that the pin is being asserted low, but I don't see why it wouldn't be if the rest of the code is working. Are you using any interrupts at all? You might be right that it's just the DAC, but that seems kind of odd to me...

 Your new code looks much nicer 
	

	
	
		
		

		
			





. Also, delay.h _requires_ optimization or it doesn't work properly, I think you're a little mixed up there 
	

	
	
		
		

		
		
	


	




.


----------



## BIG POPPA

I would like a kit too.


----------



## Jambo

Willisv and Bigpoppa, thanks for your interest - I'll keep you posted.

  Quote:


  Originally Posted by *error401* /img/forum/go_quote.gif 
_In that case I'm not really sure what else to suggest. Verify that the pin is being asserted low, but I don't see why it wouldn't be if the rest of the code is working. Are you using any interrupts at all? You might be right that it's just the DAC, but that seems kind of odd to me..._

 

Thanks for the response again. It does seem odd, I'll see what I find out. No, I'm not using any interrupts, a good few years since I was taught them and I didn't fully understand them at the time either!

  Quote:


  Originally Posted by *error401* /img/forum/go_quote.gif 
_Your new code looks much nicer 
	

	
	
		
		

		
		
	


	




. Also, delay.h requires optimization or it doesn't work properly, I think you're a little mixed up there 
	

	
	
		
		

		
		
	


	




._

 

Ah, indeed I was - thanks. This is the warning AVR Studio is giving me:

  Quote:


 Compiler optimizations disabled; functions from <util/delay.h> won't work as designed 
 

So I guess I need to turn the optimiser on - I can't find in the help file how to do this - don't suppose you could share!? I imagine this will also make the code fit inside the micro


----------



## mustang

Quote:


  Originally Posted by *Jambo* /img/forum/go_quote.gif 
_So I guess I need to turn the optimiser on - I can't find in the help file how to do this - don't suppose you could share!? I imagine this will also make the code fit inside the micro 
	

	
	
		
		

		
		
	


	


_

 

Project -> Configuration Options -> Optimization (Drop Down Menu)


----------



## user18

Add me to the list of those interested in a kit.


----------



## Jambo

Quote:


  Originally Posted by *mustang* /img/forum/go_quote.gif 
_Project -> Configuration Options -> Optimization (Drop Down Menu)_

 

Ah, thank you kindly - don't know why I didn't see that!

 User18 - will do, thanks.


----------



## shinew

Jambo, please add me to the list as well. thanks!


----------



## xmokshax

jambo, i might be interested in a kit as well, pending the final details. add me to the list, please!


----------



## joze7205

Looks good! I'm interested in a kit.


----------



## BrianDonegan

You might consider changing your Toslink connectors to 142's (TORX142 and TOTX142) so you can support 192kHz. The footprint should be the same.


----------



## Jambo

Hi Brian - thanks for the tip. I had no idea about that. I've had a quick look and the parts you mention seem quite hard to get hold of (especially in the UK) but I'll keep looking.

 shinew, xmokshax and joze7205 - thanks, will keep you updated.

 Jamie


----------



## recephasan

Quote:


  Originally Posted by *Jambo* /img/forum/go_quote.gif 
_Afraid Lordmozzilla is right, the price difference is going to be negligible! I changed my second board to AD797s over the weekend which has had a marked improvement in the clarity of the high end (could easily be placebo though, I haven't been able to A/B), so I would recommend these over the OPA134s. Can someone recommend an opamp that is somewhere between these two in performance but much cheaper than the 797?

 Been thinking about SMD soldering...



_

 

AD 8610 is a possibility, though not too much cheaper. And I'd consider 744, as well, though it's not as fun. 

 Something I don't understand: the 797 runs ~10USD. What's the big deal if the whole thing costs 14USD more? 

 How about sockets? People have had much fun playing around with the iBasso D1.


----------



## Jambo

Thanks for the suggestions. 

 The 797 has recently dropped in price a little at Farnell, which is nice.

 Yeah, sockets are an idea I've been toying with, I think I might well go along with that...


----------



## TSi

Jambo, if you are planning to do a US/Euro kit group buy thing, I suggest contacting a devoted US member.

 This is because you can ship out 1 whole package to that US person and that US person can distribute it him/herself around North America. I think this will lower the price of each kit (in terms of shipping) and in bulk order, may save us all cost!

 I will probably be interested in this too!


----------



## Marzie

I would have to agree with TSi, if there is someone in the US who would do this. And I'm not sure of this, but having someone in the US source some of the hard to find or expensive parts here, then either shipping them to you or distributing them with the kits might be a good idea also. Maybe compare your bom to the US based stores such as Mouser or Digikey (there are others too...)?


----------



## Clutz

Jambo, I need another project like I need a hole in the head - but I would be interested in a kit if you put this together. The only thing that would hold me back is the power supply, but I think I would probably use a Sigma22 and then an LDO.

 Brad


----------



## Jambo

The ideas about someone helping me in the US are good - not quite sure how I'd work it, but it's a good idea.

 Really sorry but I'm afraid this is going to have to go on the back burner a bit again as I have a project to do. It's due in ten days so the delay won't be too long.

 Things are looking good though - I've pretty much got the thing to stop making the horrendous noises when changing sources, and I have a couple of ideas for things to add.

 The output amplifiers are definitely going to be changed to DIPs - the main advantage being that people can then socket them if they want. And also I have realised through a comment on diyaudio that I forgot to add support for deemphasis - that's easily done. 

 I've also been playing with an LCD and reading up on power supply design.


----------



## TimmyMac

Quote:


  Originally Posted by *Jambo* /img/forum/go_quote.gif 
_The ideas about someone helping me in the US are good - not quite sure how I'd work it, but it's a good idea._

 

What about Glass Jar? He's been selling kits for a while now.

 Anyways, if you're looking for numbers, I'd be down for a kit (or two) for sure.


----------



## Marzie

Quote:


  Originally Posted by *TimmyMac* /img/forum/go_quote.gif 
_What about Glass Jar? He's been selling kits for a while now._

 

x2

 I believe he even offers alien DACs with the "difficult" chip soldered down, so that might be an idea as well, to save you some time/effort.


----------



## Jambo

Thanks for the suggestions. 

 Currently looking at changing to the PCM2706 so that I can add switches for play/pause, next track, previous track etc when playing over USB, I think that would be pretty neat. The other thing is that I can easily get the 2706 in the UK, the 2707 is a struggle.


----------



## lordmozilla

hey, good to hear some progress, some added control features would be really cool!


----------



## sid_

Surely it'd be best to control playback on the transport, keeping the whole thing modular? Would playback controls not be better to be implemented via some kind of control panel that plugs into the PC's USB port and controls Foobar, or similar?

 I believe that some USB DACs use the PCM2706 to send I2S to an upsampler like the AD1896 before sending it into the 8740, but you're already using the TI PCM2707 and WM8805 eliminating a need for the PCM2706 - an upsampler could be cool but I have no idea how much it affects sound quality.

 If you were to go for playback controls on the DAC, I'd be slightly concerned about the sound quality of the PCM2706 vs. the WM8740.


----------



## Jambo

I should have made myself clearer 
	

	
	
		
		

		
			





 The PCM2706 is pretty much the same as the PCM2707, it is that that I am looking to replace. The DACs will still be the 8740s. 

 The 2706 and 2707 are pin for pin compatible, but the 2706 makes access to the HID endpoints easy (ie they are available in hardware), the 2707 requires you to talk to it by I2C to access the HIDs.

 I have just put 7 headers on the board that connect to the 2706 and send the control signals over USB to the PC as you suggest. Totally up to the user whether they are used or not, the rest of the design is unchanged


----------



## sid_

Ah OK, gotcha! Giving the board headers for playback control so that users have the _option_ is certainly a good idea. I was concerned that you were intending to use the PCM2706 for the actual D/A conversion! 
	

	
	
		
		

		
		
	


	




 Out of interest, what is your opinion on adding upsampling before the DAC stage?


----------



## Jambo

Also... firmware and hardware for deemphasis handling is done, though the support for this is probably limited to 44.1kHz. And it seems to have stopped making the nasty noises when changing sources.

 The user manual is coming together.

 I've got a quote for some good quality Scottish made PCBs - the last cheap Malaysian prototype I got had a track attached to the ground plane, was a disaster! Will place an order for 20 PCBs by the end of the week


----------



## Jambo

I should have said that I have sorted the software to get it to stop making nasty noises, rather than implying that it happened by chance.

  Quote:


  Originally Posted by *imported_sid_* /img/forum/go_quote.gif 
_Ah OK, gotcha! Giving the board headers for playback control so that users have the option is certainly a good idea. I was concerned that you were intending to use the PCM2706 for the actual D/A conversion! 
	

	
	
		
		

		
		
	


	




 Out of interest, what is your opinion on adding upsampling before the DAC stage?_

 

Hehe, good good. 

 On the subject of upsampling, I have never tried it or (knowingly) heard it, and I don't know much about it, so it would be unreasonable of me to have a strong opinion on the matter!


----------



## Jambo

20 PCBs ordered yesterday 
	

	
	
		
		

		
		
	


	




 I also have a tube of AD797s sitting beside a tube of WM8805s. I hope there's still plenty of interest in this as it is getting a bit expensive for me!!


----------



## pistolpete111

Excellent news! 
	

	
	
		
		

		
		
	


	




 When do you think the kits will be available? I'm really looking forward to this now!


----------



## TheRobbStory

Ooh, exciting news! How soon can we order boards? I'm chomping at the bit here.


----------



## Jambo

Well, I made some small changes to the boards, so I'll need to build one up and make sure it all still works. I guess I can take orders then 
	

	
	
		
		

		
		
	


	




 I will have the boards by the end of the month.

 I just ordered the PCM2706s from Digikey, they're on back order and should ship on the 20th, I'm not sure if I trust that though. They're the only component that will be tricky to source that I haven't already got.

 I finished my degree this week so I've got plenty of time to spend on the manual and tidying up a few other things. I'm quite conscious of the fact that releasing 20 of these into the wild without adequate documentation could cause some real headaches! 

 The only other thing that I'm not entirely sure of is how I'm going to package the kits. Lots of little SMDs, many different cap values and they're all unmarked so can't be mixed up. And the ICs need ESD protection as well as protection from having their legs bent. To do this in a way that is affordable both in terms of money and time will be a challenge!


----------



## user18

Quote:


  Originally Posted by *Jambo* /img/forum/go_quote.gif 
_20 PCBs ordered yesterday 
	

	
	
		
		

		
			





 I also have a tube of AD797s sitting beside a tube of WM8805s. I hope there's still plenty of interest in this as it is getting a bit expensive for me!!_

 

I'm still interested. If you need a pre-deposit to offset some of your initial costs, let us know. I'm willing to pre-pay for a kit.


----------



## error401

Quote:


  Originally Posted by *Jambo* /img/forum/go_quote.gif 
_I just ordered the PCM2706s from Digikey, they're on back order and should ship on the 20th, I'm not sure if I trust that though. They're the only component that will be tricky to source that I haven't already got.

 I finished my degree this week so I've got plenty of time to spend on the manual and tidying up a few other things. I'm quite conscious of the fact that releasing 20 of these into the wild without adequate documentation could cause some real headaches!_

 

Congrats!

 I wouldn't count on getting those PCM2706, unfortunately. TI's site says they have 0 in stock and > 10,000 in progress, but not due until August. PCM2707 seems to be available though, so you might want to substitute, at least in the short term. I've had good success with DigiKey meeting the quoted dates on non-stocked TI parts in the past - provided TI has the parts in inventory. Ditto for ADI.

 Packaging the little buggers has got to be one of the main reasons nobody seems to offer SMD kits. I just can't think of a labour efficient way to do it.


----------



## BrianDonegan

The PCM2707 (probably 2706) come in a tape package, much like smd caps and resistors. For those you could just cut up the tape.

 For chips in a plastic rail, I just chop up the rail and use masking tape to cap the ends. Depending on the size of the rail, I use my bandsaw (not often) or a hot wire cutter. I picked one up for $2 at a craft store that runs on a couple D batteries.

 For the R's and C's, just cut the tape and label them.

 Of course, this is part of the reason I ended up pre-building modules.


----------



## Jambo

Brian - thanks for the advice. I had considered that but thought that perhaps the tape wouldn't give adequate ESD protection. I can only assume that you haven't had any problems.

 Error401 - I'll see what happens on the 20th, if they don't ship then I'll change to the PCM2707. Chips are on their way to you btw 
	

	
	
		
		

		
		
	


	




 User18 - a great offer, thanks. I will probably take money between getting the boards and ordering the bulk of the parts for this reason - they'll all be on next day delivery anyway, but I think it would be foolish to take cash at this stage until I've checked that the new boards work.


----------



## malldian

Price point? I might have skimmed over it but I am interested in building something like this, and need to choose between alien or jambo


----------



## Clutz

This DAC should beat the pants off of the Alien DAC. If you can afford it, this is the way to go.


----------



## holland

Jambo, I'm interested. What is the final config (some parts went back and forth) you are putting together and the cost?


----------



## CingKrab

Just read this thread -- definitely put me down as interested as well.


----------



## ziplock

Mark me down. Looks good!


----------



## Jambo

Holland - I've just put together an updated block diagram which I hope answers all questions about the parts! USB receiver is undecided at the moment but will be PCM2707 or PCM2706, it is exactly the same chip (in this application) apart from that the PCM2707 doesn't allow control of the PC by simple switches that I have provided support for.

 Other things that I either haven't pointed out before or have changed or may have been missed: Caps in the output filters are film caps - they're still 0805 SMDs though. The opamps are now in DIP packages rather than SOIC which allows for easy swapping especially when socketed (which they will be). 






 Now for the prices... In kit form, it will be £85 for the PCB and all parts (apart from power supply, switches and LEDs). Postage will be charged on top of this, but at no more than what it costs me. Apologies if this seems a lot, but it really has not been a cheap exercise to get this as far as it is!! Additionally, 20 is still low volume so parts/PCB discounts are not that great, and I've gone for domestically made PCBs this time as my last Malaysian ones weren't up to scratch. Not really price competitive with the Alien DAC I'm afraid but it couldn't be with these components!

 Partially/fully built boards will be slightly more obviously, but I'm unsure how much more yet. I need to find out if I can solder SSOPs with lead-free solder and/or if I can legally post these out full of lead - I suspect that I shouldn't.

 Listening to a bit of Ray Lamontagne through it right now, so clear!


----------



## holland

Thanks, that looks good. Did you switch to the torx142 or the totx142? If not, how hard is it to retrofit to handle 192Khz (possible external reclocker)? Cut the power trace, and lower voltage coming in, right?

 I'm definitely in for 1 unless you're going to do another build with a reclocker inserted and pins to pull the differential signals out. If so, I'll wait for that one.


----------



## rds

That looks pretty sweet. I'll be ordering one soon.
 Have you thought of doing a ps board?


----------



## malldian

Can you just purchase a board and give us a parts list?


----------



## rds

do you enjoy purchasing parts that much?


----------



## 00940

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_do you enjoy purchasing parts that much?_

 

some people have plenty of leftover parts from other projects


----------



## Jambo

rds - yeah, I do plan to do a power supply subject to this being a success!

 Holland - I did look into the 142 parts briefly, but none of my suppliers carry them. Also, I don't have any 192kHz equipment so I wouldn't be able to test that adequately if I did add it on. 

 As for retrofitting, I would think that the footprint would be the same, I'm not sure why the voltage would need to be lowered though - do these parts run off a lower supply than 3.3V? The software configuration of the WM8805 would perhaps need altered as I think 192kHz operation is slightly different for it, I could help you with that though. I have no plans to add a reclocker. 

 The (unbuffered) differential outputs are available on some vias but I really don't know what they will be capable of driving. Afraid I don't plan to change that.

 Holland asked me some good questions about the micro via PM, I'll put the answers here... The micro is in an SOIC package, and it can be programmed in circuit. In fact, this is by far the easiest way. The programming pins are on the board as shown in this pic:






 I used cable like this one as suggested to me by error401:
	

	
	
		
		

		
		
	


	



 I find that the unbuffered version works just fine. I put a 6-way molex connector on the other end of the cable which I push onto the pins when programming. The board has to have 3.3V and GND connected for programming.

 I obviously I would distribute the hex code for flashing the micro, and it can be flashed using the freeware Ponyprog. I can do the soldering/programming of this part if needed - as it's an SOIC rather than an SSOP it's easy to see if it has been soldered correctly so there shouldn't be any bad soldering issues!

 Malldian - I'm happy to sell a limited number of boards by themselves though I may wait until the second batch before doing this.


----------



## rds

00940 - yeah, that makes good sense. That didn't occur to me. When I read that I was like good god someone actually likes doing that?!
 Jambo - this should be a big success - the dac looks fantastic. I'm too lazy to build the supply, so I'll wait for the pcb. Plus pcb looks so much nicer.
 I think flashing the micro with the kits would be a very good idea. I've done that lots but it's a pain in the ass to set up. For people who haven't done it it would be a very big pain in the ass. Also, a lot people only have laptops and don't even have serial ports.
 You could build a header that you simply push the chip onto (pcb) with a little weight on top.


----------



## holland

Jambo, IIRC Torx177 is @ 5V. The 142s are at 3.3V.


----------



## MASantos

Jambo, everything looks great. I believe that most people wouldn't need both optical inputs though.

 I would suggest you ordering the parts for the kits from the US form mouser or digikey. Even with added shipping costs and VAT it will probabyl be MUCH cheaper than ordering from farnell or other EU supplier.


----------



## royewest

Or better yet, just sell us the boards and give us a good set of part numbers for digi-key or mouser in the US (as the wonderful AMB kits do). We all save $. I'm really looking forward to trying this project.


----------



## TimmyMac

I'm so torn. I want to build a nicer DAC but if I'm going to spend the money I would prefer balanced outs. Too bad the buffalo DAC costs a whole lot more.


----------



## Jambo

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_I think flashing the micro with the kits would be a very good idea. I've done that lots but it's a pain in the ass to set up. For people who haven't done it it would be a very big pain in the ass. Also, a lot people only have laptops and don't even have serial ports.
 You could build a header that you simply push the chip onto (pcb) with a little weight on top._

 

Good idea, thanks - I could perhaps set aside one of my PCBs for that purpose.

 Holland - aha, I see, thanks. I'm using the 147s though which are also 3.3V (the WM8805 is a 3.3V part so I didn't want to throw 5V TTL at it even though it would probably be ok). So, 147 to 142 should be a straight swap.

 Cannot wait til these boards are here, there's an added change that I haven't mentioned yet


----------



## Jambo

Woohoo, look what just arrived:






 25 of them, nice.


----------



## rds

sweet


----------



## qib

This might be a silly question but how would this compare to commercial dacs such as the modded zero or the trends dac sq wise? Also would this be a difficult job for me as the only diy i've done are recabling jobs. Thoughts?

 Also this would be used to in between the source and a tube amp...

 Regards


----------



## error401

Nice! I guess they do exist after all!


----------



## Jambo

Quote:


  Originally Posted by *qib* /img/forum/go_quote.gif 
_This might be a silly question but how would this compare to commercial dacs such as the modded zero or the trends dac sq wise? Also would this be a difficult job for me as the only diy i've done are recabling jobs. Thoughts?

 Also this would be used to in between the source and a tube amp...

 Regards_

 

Hi,

 I'm not familiar with the models you mention so I'm afraid I can't really comment. It sounds nice though 
	

	
	
		
		

		
		
	


	




 If you haven't soldered surface mount devices before, I think you'll find this pretty difficult. You could easily learn to do it, but really you don't want to practice on this. Have you got an old PC motherboard lying around? That's how I learned...

 Yes, this would go between source and amp and I see no reason why it wouldn't sound excellent with a tube stage after it.


----------



## Jambo

Well folks, the 20 PCBs are here, I've just finished soldering one up and here it is:






 I haven't managed to get the HID functions (play/pause, skip etc.) working yet, I think that must be a computer issue though as there is little to go wrong with it.

 The caps on this board are bigger than what will come with the kit as I had them lying around (Rubycon 2200uF 25V versus Rubycon 2200uF 10V). I ran out of header pins so not all are populated. A couple of very small software things to tweak but it's looking great


----------



## TheRobbStory

Awesome! Let's hope it sounds half as good as it looks!


----------



## BIG POPPA

I still want one.


----------



## Jambo

Ok guys, I'm going to let this into the wild....

 Some points to note:

 -Please read the whole of this thread so that you know what is, and what isn't included in the kit (eg a power supply IS NOT included).
 -Please make sure that your soldering is up to it
 -The HID functionality doesn't seem to work on my PC so please take this as untested and not guaranteed.
 -Same goes for deemphasis - the hardware is there but I haven't done the firmware. I also may not ever do it but I'll gladly send you my ideas on how to do it.
 -Kits cost £85 plus postage. Import duty will be your problem (if applicable). Microprocessor is available programmed and soldered for no extra charge. 
 -I will provide as much support as I can between now and September, but on September 1st I start work in Baku and I can't guarantee to help as much as I would like.
 -A user manual will be available as soon as kits are shipped out. It is nearly finished and it will be constantly updated.

 Now... There are 19 of these available in this batch. The PCBs are sitting on my desk, as are a lot of the ICs. As soon as I have received payment for 19, I will order the remaining parts - they will arrive next day and I will make up the kits and post them out within a week of receipt.

 If all 19 aren't sold within a reasonable time (2 weeks?), then a refund will be available and/or we can discuss an alternative way forward.

*Postage Costs:*
 Kits will be posted by Royal Mail and delivered by your local mail company. I will get a service which requires a signature IF it is available in your country. I'm a believer in easy numbers so here are my proposed postage charges:
 UK: £4
 Europe: £7
 Rest of World £10

*Partial Kits/Assembled Kits*
 I do not intend to supply partial kits/bare PCBs at this stage. This is because I have a lot of costs to cover and all budgeting has been around 20 kits and the associated bulk discounts. If this is a success then I will order further batches of PCBs and bare boards will be available. Assembled/partially assembled kits available by negotiation.

 Please contact me by PM for payment details. If you have any issues with my integrity, please see my feedback on ebay, jambo0885.

 I have tried to post a mall-fi but haven't heard back from the mods yet.

 Any further questions, feel free to PM or reply to the thread.

 Cheers,

 Jamie


----------



## TSi

damn... tat looks really really clean! is it possible to get a few more pictures on it?


----------



## pistolpete111

I had posted the guts of this in a PM to Jambo, but I guess it's relevant to everyone.

 What do people plan to do about a power supply for their Jambo DACs?

 I recall someone on this thread mentioned using a PC PSU, but they are normally not recommended for hifi stuff I think. I'm no expert, so I'm a bit unsure about how I should go about the power supply - are voltage regulators the only difference between a good and bad PSU? I guess there is more to it than this?

 Could the power supply kit that the guys at twisted pear sell for the Opus be modified for this DAC? I guess that their power supply is pretty good...

 Any opinions/advice would be great,

 Thanks


----------



## Beefy

Quote:


  Originally Posted by *pistolpete111* /img/forum/go_quote.gif 
_Could the power supply kit that the guys at twisted pear sell for the Opus be modified for this DAC? I guess that their power supply is pretty good..._

 

I think that they would be the best option IMHO.
 Use Low Current Dual Power Supply (LCDPS) - A Dual Regulated CLRC Supply for 3.3V and 5V.
 Use Low Current Bipolar Power Supply (LCBPS) - A Regulated CLRC Supply for ±12V.
 ...... assuming the LM317 regs can go as low as 3.3V.....?

 If I thought that I could manage that SMD soldering, I'd be over this project in a heartbeat. But anything smaller than a SOIC OPAMP would probably cause me problems


----------



## akione

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_...... assuming the LM317 regs can go as low as 3.3V.....?

 If I thought that I could manage that SMD soldering, I'd be over this project in a heartbeat. But anything smaller than a SOIC OPAMP would probably cause me problems 
	

	
	
		
		

		
		
	


	


_

 

Yes, they do. 1.2V min. 
	

	
	
		
		

		
		
	


	




 Should be easy to knock up a suitable supply on perfboard. 
 Or maybe build a SuperReg if you want the best.

 [My problem with SMD is the little 0805 resistors .... they shoot off when I 
 pick them up in my tweezers and I can never find them again. 
	

	
	
		
		

		
		
	


	




 ]


----------



## pistolpete111

The SuperReg kits don't seem to be available from VSE at the moment - the "buy" link just gives an error.

 The Twisted Pear route sounds like a good one - everyone has only good things to say about them. The only disadvantage is that the two twisted pear kits needed (LCDPS, LCBPS) and the cost of a transformer will work out on the dear side - well over half the price of the DAC itself.

 The third option, I think Jambo mentioned it before was to use a wall wart with a DC converter for the 12V. I see the advantage of it being that the transformer is housed far away from the DAC, but I assume that if the wall wart was a good solution the Twisted Pear guys would just use it and not have gone through all the work invovled in designing their power supply units.

 Did any of you ever play about with using different power sources for a DAC? How would a wall wart with good regulators compare to the Twisted Pear power supplies?

 Thanks again,


----------



## Beefy

Quote:


  Originally Posted by *pistolpete111* /img/forum/go_quote.gif 
_The Twisted Pear route sounds like a good one - everyone has only good things to say about them. The only disadvantage is that the two twisted pear kits needed (LCDPS, LCBPS) and the cost of a transformer will work out on the dear side - well over half the price of the DAC itself._

 

TREAD perhaps? You'll need *4* though! Tangent Regulator, Adjustable, plus Diode bridge

  Quote:


 The third option, I think Jambo mentioned it before was to use a wall wart with a DC converter for the 12V. 
 

The DIY darlings TREAD, STEPS, LCDPS/LCBPS σ11/22 etc are good for audio because of their incredibly high performance. You won't get nearly as good performance from a wallwart, and you will probably compromise the DAC performance as a result.


----------



## error401

If you're okay with a switcher, a wall-wart is fine, since you'll be regulating its output for the critical supplies anyway. I'd then use a TREAD for the DVDD and a JSR-03 for AVDD (or another TREAD). Use the switcher to generate -12V. Should be pretty cheap. Another option for the switcher IC is the TI DCP02 series, like the DCP021212D. These are isolated 2W supplies, so you give it 12V (or 5V or whatever) and you get two 12V outputs that can be connected in series to get +/-12V and ground. They're pretty noisy and expensive and have poor load regulation - but they come in DIP and don't require any external components really. I've found them useful for powering things from the USB power supply, since you don't need to use a virtual ground with them. If you wanted, you could even post regulate them.

 Unless you home-grow it on a protoboard, I think you're looking at a fairly expensive PSU. The cheapest way I can think to do it without using any switchers, and using easy to get boards is to get the LCBPS and transformer from Twisted Pear (probably cheaper if you buy parts yourself, but not sure). Add a pair of TREAD kits from tangent and you're set.

 The farthest I would go as far as 'niceness' would be the σ22 (or something similar like LCBPS), followed by a pair of JSR-03 or similar super regulators from peranders.


----------



## pabbi1

You can also go cheap linear on eBay  or here - casing is the challenge. Just search for 'linear power supply' - sometimes you can get what you need.


----------



## pistolpete111

Thanks everyone for the replies.

 I've looked into it a bit more myself, and the Twisted Pear route seems to be the best alright. Think I might add a few extra kit's of theirs into my order as well


----------



## Jambo

In agreement with all that has been said really! 

 As ever, it's a trade off - As I've said before, I have acheived nice results with a wall wart powering a pair of LM317s for AVDD and DVDD and an NMA1212SC switcher for +/-12V. This is easy to put on veroboard, only the regs and some caps needed and some resistors if you go for adjustable regs. In fact, I haven't been able/felt the need to try my DAC with anything better as yet.

 Also to emphasise again that AVDD (+5V) is BY FAR the most crucial supply, the WM8740 is very sensitive to ripple on its analogue supplies, ripple on DVDD and +/-12V has thousands of times less effect! 

 I think the Twisted Pear supply would work great and would definitely look nicer, but it is more expensive.

  Quote:


  Originally Posted by *akione* /img/forum/go_quote.gif 
_[My problem with SMD is the little 0805 resistors .... they shoot off when I 
 pick them up in my tweezers and I can never find them again. 
	

	
	
		
		

		
		
	


	




 ]_

 

What you probably need is a better set of tweezers - changed my (soldering) life when I got a decent set! I like the crossed over kind, the ones you squeeze to let go of things and when you let go of them, they still hold onto whatever you picked up. 

 You'd be surprised how easy it is to solder SSOPs if you have the right gear (that's a chisel tipped iron, lots of flux, leaded solder and braid for me) - but this DAC is potentially an expensive way of learning.

 TSi - I'll get some more pics up, afraid photography isn't a strongpoint of mine though and I am limited to the camera on my phone!


----------



## akione

Quote:


  Originally Posted by *Jambo* /img/forum/go_quote.gif 
_.....What you probably need is a better set of tweezers - changed my (soldering) life when I got a decent set! I like the crossed over kind, the ones you squeeze to let go of things and when you let go of them, they still hold onto whatever you picked up._

 

.... Funny you should say that ........ that's exactly what I've done. 
	

	
	
		
		

		
		
	


	




 Haven't built anything else with SMD, yet, but it should be a lot better now. 
	

	
	
		
		

		
		
	


	




 [Actually, the problem's more likely to be because of the Arthritis I have in my hands. 
	

	
	
		
		

		
		
	


	




 ]


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## Jambo

As promised, some new pics:


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## pistolpete111

The pics look great 
	

	
	
		
		

		
		
	


	




 Can't wait to get my hands on this now. I really like the way it has a good few inputs, all lined up on a single side - will fit neatly into the enclosure I have for it.

 Just out of curiosity, I see a "SPDIF Config" section on the board. What can it be used for?


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## decayed.cell

Hm I find those two caps at the end a bit tall, is there enough room to mount them on their side, say one over one under?


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## Jambo

Pete - the SPDIF config bit has the pull-up/down resistors for the WM8805. Normally, they're set to tell it to operate in software mode and not much else - but you can also by changing these operate it in hardware mode. Useful to have for debugging, but once you've got it working best left alone.

 Decayed.cell - not sure, will have to look, but remember those caps aren't the ones that come with the kit - they're the 25V Rubycons, the kit will have the 10V ones, they're significantly shorter.


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## Jambo

The components for all the kits will be with me by the weekend, so should be shipping kits early next week. There are a few left so give me a PM if you want one.


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## Jambo

Just to let you know, ALL components are now here for the kits, all orders received so far are now shipped.


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## Jambo

Hi everyone, just to let you know that I can only ship kits for one more week due to my move abroad. In an effort to try and shift these remaining kits quickly I am offering postage to anywhere at the UK price.


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## ak40ozKevin

Hi Jambo,

 I've been loosely following your DAC and I'm pretty interested in it. I read that you are moving abroad and was wondering if you would still be available for any support in the Jambo DAC build thread after you move?

 Also how much would 1 kit be shipped to Portland, Oregon in the USA?


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## Jambo

ak40ozKevin, I will reply to the thread as often as I can, I just can't guarantee the rapid responses that I am putting in at the moment! 

 I'm currently offering postage worldwide at £4 so total cost £89. Paypal charge pretty hefy fees though so if paying by paypal please add an extra £2 (the fees will be around £4).

 Jambo.


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## Jambo

Hi everyone, a bit ahead of time but just a heads up that I have flights booked for a trip home mid January so I can ship some kits then if anyone is interested.


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## sputnik13

Hey Jambo,

 How do I place an order for one of your kits?


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## Jambo

Sputnik, best plan is to PM me then we can take it from there. I accept payment by paypal though, it's very straightforward so long as you remember that I can't ship til January.


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## Jambo

Guys, I'm home for a short time so if anyone wants a kit let me know. 85 GBP including shipping to Europe and the US, contact me for a price for elsewhere.


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## user18

I bought the Jambo DAC kit over a year ago and planned to build it. But, then I moved and the project got sidetracked. To make a long story short, I don't have time to build this and I don't see it changing in the foreseeable future. So, rather than see this go to waste, this post is an interest call for any DIYer wanting a go at the Jambo DAC. **edit -- TAKEN -- edit**

 Many thanks to Jambo for releasing this project.


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## holland

wrong thread


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## Jambo

I'm going to be home for about a week from Dec 6th - I still have a few kits, drop me a PM if you want one.


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## free2dev

Hello Jambo,
   
  Do you still have any more kits left? I need one 
   
  Thanks
  free2dev


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## Jambo

free2dev,
   
  Thanks for the interest, I see you left no stones unturned while trying to contact me!
   
  Yes I still have some left but I'm not at home just now.. In Dubai right now, Ghana tomorrow then Texas in a week.. Hopefully will be spending a bit of time at home late June/early July and I should be able to post some kits around then. PM me at the end of June and we can sort something out.
   
  Cheers
   
  Jamie


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## Jambo

All,
   
  For anyone else who is interested, I'll be home from June 27 - July 1st, give me a shout if you are interested in a kit.
   
  Cheers
   
  Jamie


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## phishhead92

I was looking on audiologica about the TREAD power supplies and i noticed the new version of the STEPS called the YJPS, has anyone tried this? i was wondering because i hopefully will be trying this for my first build and i want to start on the power supply before i get the kit.


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## JamesL

The yjps is a very nice single rail power supply with very low output impedance and good ripple specs, but I think you need a few different supply voltages with this dac.. Probably the AVDD and DVDD for the wolfson chip, and +/- supply for the output stage.  
   
  4x yjps would cost more than the DAC itself and would take up a lot of physical space.  I think twisted pear's dual and bipolar psu offerings would make the most sense, while amb's sigma25 and tangent's treads would also work well.


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## phishhead92

o alright, i did look at TREADs and they seem simple enough, now i have no idea whats what when it comes to like power (this will be my first official audio DIY) so could you explain to me how these work, i do keep seeing you need 4 TREADs is that like one for 3.3V, 5V and then +/-12V each? if so is there a way on the chip to change the output or how does it all work?.
   
  or if i were to do the sigma 25, do you just need the one and its can handle all of the different power needs?
   
  also last question, can you hook up all 4 treads like in one box so it only has one power cable or something like that?  (probably a dumb noob question haha)
   
  EDIT: i thought i read earlier in the thread that the DAC only supports 44.1kHz and i assume only up to 16bit playback is this true?


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## JamesL

Quote: 





phishhead92 said:


> o alright, i did look at TREADs and they seem simple enough, now i have no idea whats what when it comes to like power (this will be my first official audio DIY) so could you explain to me how these work, i do keep seeing you need 4 TREADs is that like one for 3.3V, 5V and then +/-12V each? if so is there a way on the chip to change the output or how does it all work?.
> 
> or if i were to do the sigma 25, do you just need the one and its can handle all of the different power needs?
> 
> ...


 

 Yes, you would need 4 treads.  A TREAD uses the lm317 by default which is an adjustable regulator.. you should choose the components based on the approximate voltage you want, and you can fine-tune the voltage through the trimpot that is on-board.  One board would supply the 3.3v, one would supply the 5v, and two boards would be used to provide the +/-12v.
   
  The sigma 25's work the same way.  The main difference is that it uses the lm78** series of regulators instead of the lm317.  The lm78** is not a adjustable regulator, but is a series of regulators that have a fixed output voltage.  
   
  tangentsoft and amb's website both have diagrams to show how to wire the transformers to make a bipolar supply
   
  yes, you could put all 4 treads in one box and use a single power cable, as long as the connector has enough contacts.


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## phishhead92

well since from what ive read the Jambo only supports 44.1kHz i decided to go with the AMB y2 (with the y1 full++)
   
  thanks for the info i might build this later just for fun though, so good to know


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## Jambo

I'm pretty sure that it will support higher sampling rates but I haven't tested it so can't guarantee it...


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## Mercator

The Jambo DAC and AMBs gamma 2 use the same wolfson dac chip.  If the gamma 2 supports a higher rate then the Jambo DAC should also.  I have built two Jambo DACs and think they are fantastic but it is a very complex build so maybe not the best candidate for a first DIY project.


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## Nebby

The gamma2 can be built with an ASRC, so it might not be directly comparable in terms of rates supported. Haven't looked it up but that might be a factor.


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## cobaltmute

ASRC has nothing to do with data rate supported by the chip.
   
  the issue would be what SPDIF receiver in on the Jambo DAC and if it can handle the higher sample rates.


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## Nebby

Thanks for clearing it up, wasn't sure myself.


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## Jambo

Evening folks, finally got some decent time off work and I've done some more work on this project. I've finally got round to adding an LCD screen!
   
  You'll notice that I have used one of my old prototyping boards rather than the smart black ones that are available for those who order a kit.
   
  Here's the startup screen, shown each time the power is cycled:
   

   
  And then the current input source is displayed along with the SPDIF interface status (read from the WM8805):
   

   
  By changing just a few lines in the C source code you can name the inputs as you like.
   
  When the SPDIF interface is locked I want it to show the sample rate. However, so far as I can ascertain the WM8805 does not allow this to be done precisely, it seems like it can only indicate the following:
   

 32 kHz
 48 or 44.1kHz
 96 or 88.2kHz
 192kHz
   
  I don't think I really want to put '48 or 44.1 kHz' on the display!? I may assume that 48kHz and 88.2kHz are never used, we'll see...
   
  I had to sacrifice some switches and the LEDs to do this. It now only has one source selection switch which cycles through the available inputs, rather than having a switch for each input. Aside from the LCD screen itself (with HD44780 driver) and wiring, no hardware modifications are needed, except that the 5V supply for the LCD should probably be isolated from the analogue 5V supply.
   
  The LCD screen in the picture I picked up on ebay for 3 GBP delivered, I'm sure it's possible to get a much nicer display.
   
  The hex will be available to anyone who wants it. If ordering a kit, specify which version of the hex you want on your micro, of course the previous version is still available. My recommendation would probably be to go with the 'basic' version first and get everything working, then make your own programming cable if and when you go down the LCD route.
   
  I'll release an updated schematic when I get time to show how the LCD is wired up.
   
  Questions welcome.
   
  Cheers
   
  Jamie


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## holland

Quote: 





jambo said:


> When the SPDIF interface is locked I want it to show the sample rate. However, so far as I can ascertain the WM8805 does not allow this to be done precisely, it seems like it can only indicate the following:
> 
> 
> 32 kHz
> ...


 
   
  That's great, Jamie.  Hmm, I might have to recase for this.  You do want to put 44.1.  I also think some people like to upsample to 88.2KHz.  You seem to come across this quite a bit in the Computer Audio sub-forum, as 88.2 is a 2x upsample instead of fractional.


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## Jambo

I've just realised that DAT is 48 kHz so really I need to be able to determine that one also.
   
  What were wolfson thinking!!
   
  Turns out R16 will let me get the indicated sample rate from the SPDIF stream (to be honest, I didn't realise that that was included in the stream), rather than the recovered frequency from the WM8805 which I really wanted to get. I guess it should be accurate enough. It's a 4 bit word, but the Wolfson datasheet says to refer to the SPDIF spec for how to decode it. Argh. It is not free.
   
  I found this much from the helpful people at minidisc.org:

```
27 26 25 24 Sample frequency Fs ------------------------------------------- 0 0 0 0 44.1kHz 0 0 1 0 48kHz 0 0 1 1 32kHz or sample rate converter - - - - Reserved
```
   
  Odd that only 3 rates seem to be defined when the bits allocated can indicate 15 different rates...
   
  Anyway, if I read these two registers then hopefully the only uncertainty would be between 96kHz and 88.2kHz...
   
  Jamie


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## free2dev

Jamie,
   
  This is great, I would certainly try out your new  code which supports LCD. Also is the LCD interface serial or parallel. I picked up a parallel LCD locally here for $4 and was planning to wire it up with the DAC.
   
  Regards
  free2dev


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## Jambo

Hi Subbu,
   
  Glad to hear some interest.
   
  You'll need a parallel LCD with HD44780 driver. I've set it up to use 4 bit parallel mode as I didn't have enough spare pins for anything else.
   
  Pretty busy just now but I'll get the code to you when I have time and also a schematic.
   
  Regards
   
  Jamie


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## geekagent

I found an official pdf that lists all the sampling frequencies from S/PDIF.
   
   
http://tech.ebu.ch/docs/tech/tech3250.pdf


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## free2dev

Hi Jamie,
   
  Could you post the schematic and the code when you get some free time? 
   
  Thanks!


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## Jambo

Hi Folks,
   
  Home again - so if anyone wants a kit please let me know this week.
   
  Subbu,
   
  Sorry for the delay. Please find the pinout below - but crosscheck it with the particular HD44780 LCD that you get, the below is quite standard but not 100% in my limited experience. I've noticed that Pin3 on the LCD varies a bit. From memory I think Pin3 and Pin15 can be used to vary the contrast and brightness.
   

 LCD Pin Description Board Pin Micro Pin 1 GND     2 +5V     3 GND     4 Register Select SW3 13 (PB1) 5 R/W SW5 14 (PB2) 6 Enable SW7 15 (PB3) 7 NC     8 NC     9 NC     10 NC     11 DB4 LED1 16 (PB4) 12 DB5 LED3 17 (PB5) 13 DB6 LED5 18 (PB6) 14 DB7 LED7 19 (PB7) 15 +5V (     16 GND       Source Select SW SW1 12 (PB0)
   
  Code/hex to follow!
   
  Cheers
   
  Jamie


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## free2dev

Hi Jamie,
   
  Thanks for the pinout. Let me know once you have the new code/hex ready. 
   
  Cheers!


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## Jambo

Howdy folks,
   
  I'm  home at the moment, if anyone wants a kit let me know within the next 24 hours!!  I'm testing the LCD firmware a bit more just now, it looks pretty good so I think I'm going to release it.
   
  I also made a power supply control board which makes the LED on my on/off switch sleep like an apple LED and controls some relays. Remains to be seen what kind of audio performance will result from using relays however.
   
  Cheers
   
  Jamie


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## Jambo

Evening!  I'm home this week if anyone is interested in a kit!
   
  Cheers
   
  Jamie


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## onyu

I think i want one


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## Hugo Meekes

Dear Jambo,
   
  I have been trying to get the WM8805 working in hardware mode to connect it to a TDA1541(A) using SPDIF as input.
  I have trouble getting it into I2S 16 bit mode (in hardware mode).
  If you could provide me with a schematic with your solution, I would be very greatful.
   
  Kind regards,
   
  Hugo


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