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Jambo DAC - Build Thread

post #1 of 40
Thread Starter 
Yes folks, finally some kits have been posted out! I am currently waiting on the remaining optical receivers and then everyone else who has ordered will get their kits. Anticipate shipping again on the 21st or 22nd of July.

For those who don't know what the Jambo DAC is, here is the discussion thread:
http://www.head-fi.org/forums/f6/jambo-dac-288159/

I would rather that any design related questions are kept in that thread, and this thread can be kept for linking to design material and discussion of results and any problems with the build. But I realise that it may not work out that way.

I have linked to the user manual below, also the most recent schematics and the .hex file that will be required if programming the micro yourself. More stuff will become available over time.

Obviously the manual is a work in progress - any comments on what is missing are welcome.

As always, keep the questions coming and those that have kits - let us know you get on with the building.

Cheers

Jamie

User Manual
Schematics
.hex File
LL
post #2 of 40
My kit arrived earlier today! I'm going away for the weekend so I won't have a chance to start building until Monday.

Had a quick look at it anyway, and it all looks good!
post #3 of 40
where can I buy the kit? How much is it?
post #4 of 40
Thread Starter 
Nice to here it has arrived safely pete

yzriver, http://www.head-fi.org/forums/f6/jam...ml#post4312743
post #5 of 40
DAC-construction is coming along well. I did the IC's last night and they went down fine - I was expecting them to be more troublesome, only took about 30-40mins to have them all done.

Anyway, today I went to do the resistors, and I've got a couple of questions:

There was no 720Rs in the kit, but there were 2x 715R (83A is the code on the resistor). I assume these are what I should use for 720R?

On the parts list, R34-R37 are listed twice...once in the 22R section, and once in the 27R section. I guess that I just use the 22R's for R34-R37? (I guess they are only relevant for the LEDs anyway)

I'm a bit undecided about the LEDs I'm going to use, is it ok for me to test the DAC without connecting any? (I was thinking of getting some of them switches that have LEDs in the button - but the ones I found so far are 50mA).

Also, last question, just as I was about to order my +/- 12V switcher I found some rails I can use from the power supply in the cdplayer I am going to use for an enclosure. I didn't expect it to have so many rails in it, but it turns out it has a +12.9, -14.9,and +8 (amongst others). I'm gonna use the +8 for the two treads I have (to give me a well-regulated 5 and 3.3V). Would it be ok to use the -14.9 supply for the -12 on the DAC? or is there an easy way for me to get it closer to -12V?


Thanks,

Pete
post #6 of 40
Thread Starter 
Hi Pete,

Glad to hear construction is going well and I appreciate the help in ironing out errors in my documentation!

Quote:
Originally Posted by pistolpete111 View Post
Anyway, today I went to do the resistors, and I've got a couple of questions:

There was no 720Rs in the kit, but there were 2x 715R (83A is the code on the resistor). I assume these are what I should use for 720R?
Ah, sorry about that. Yes, that's correct, I'll get the manual/schematic etc changed.

[QUOTE=pistolpete111;4507903]
On the parts list, R34-R37 are listed twice...once in the 22R section, and once in the 27R section. I guess that I just use the 22R's for R34-R37? (I guess they are only relevant for the LEDs anyway)
[quote]

Correct again. Sorry, I thought I had removed that! Originally I calculated them as 27R, but I reckoned that since I was already using a couple of 22Rs that that would do (has worked just fine in my experience).

Quote:
Originally Posted by pistolpete111 View Post
I'm a bit undecided about the LEDs I'm going to use, is it ok for me to test the DAC without connecting any? (I was thinking of getting some of them switches that have LEDs in the button - but the ones I found so far are 50mA).
Yeah, no problem to test without the LEDs, if you want to check that that is working you should be able to see 3.3V on the relevant through hole with a scope or DMM. Yeah 50mA is a bit much I think (according to the datasheet anyway, I haven't tried it). You could rig up some discrete logic gates to work as buffers I guess...

Quote:
Originally Posted by pistolpete111 View Post
Also, last question, just as I was about to order my +/- 12V switcher I found some rails I can use from the power supply in the cdplayer I am going to use for an enclosure. I didn't expect it to have so many rails in it, but it turns out it has a +12.9, -14.9,and +8 (amongst others). I'm gonna use the +8 for the two treads I have (to give me a well-regulated 5 and 3.3V). Would it be ok to use the -14.9 supply for the -12 on the DAC? or is there an easy way for me to get it closer to -12V?
I'm not absolutely certain what difference having different +/- supply values makes, I'll try and look into it for you.

You can however get negative voltage regulators which work just the same as positive ones and you could regulate the -14.9 'down' to -12V (2.9V is a more than adequate drop). A quick search of Farnell shows the L7912 as a suitable part, I've never used it and don't know what its performance is like but as I've said before, the opamps have decent PSRR.

I hope this helps

Jamie
post #7 of 40
Hey,

Almost finished building the DAC. I have one quick question however - are the crystals polarised? There is a dot beside one of the pads on the PCB for them, but the crystals themselves don't seem to have a + marked?

Thanks
post #8 of 40
Thread Starter 
Hi Pete,

I hadn't noticed that - but no, it makes no difference.

Cheers

Jamie
post #9 of 40
Great thanks.

I'll put them down today and then I'm finished the DAC. I'll post some pics of it soon I'm just waiting for a parcel to arrive with some power supply parts now - should be able to post about some listening impressions in the near future as well

Should I expect it to have some "burn in time"? I've seen some people on this forum before talking about how some amps/dacs need 20 hours of use before they sound their best?
post #10 of 40
Thread Starter 
Great to hear you're making swift progress! Look forward to seeing the pics.

Re "burn-in time", I'm more of an engineer than an audiophile but I think it does sound better after time. Whether that is due to changes in the components or some placebo effect, I'm not sure - I suspect the latter! Let me know what you find.
post #11 of 40
Another question - Do you have a part number (radionics/farnell) for sockets for the header pins on the board? I figured it's best to ask before I tryed to guess what might fit

I'm looking to have the power leads connected via a socket and a socket for programming the micro as well.

Thanks,

Peter
post #12 of 40
Thread Starter 
Hi Peter,

The pins are on a 2.54mm/0.1" spacing which is very standard so a range of things will fit. Molex connectors will fit on the header pins that I put in the kit, but you may have a job getting them to stay put. An actual Molex header such as this one with a retaining tab may be more suitable, Farnell # 9731172.

For terminating the cable, part number #143129 looks to be the mating half of the above. By the looks of it you'll also need to buy the crimp pin things, part #9773789.

Alternatively, the connectors used on PC motherboards fit well on the headers I provide with the kit and provide a nice cheap DIY alternative if you have access to some old computers.
post #13 of 40
I received my kit on Friday, and I spent about 5 hours stuffing the board today. It's all done, except for the jacks and the SIP pins.

I'm just need to find an enclosure, build up the PS, solder down the jacks, LEDs and the SIP pins. Casework always kills me, but this one is going to be a bit tricky as it's all panel mount.

Can you link the datasheets for the panel jacks, for lining up and making a template for the panels.

The kits are nice and easy to work with. I just had one little scare, a little spasm which sent a resistor flying, but that's pretty standard for me. I'll be blessed if I don't drop anything.

One small comment, if you ever tweak the boards. Since the pieces are panel mount, the board standoff locations won't work with all cases. Some cases have a small ledge or tubes in the way. I don't know if it's possible to add some extra holes for standoffs further in from the back edge. The back side of the PCB can be supported by the panel components. Also, keep the existing standoff points, in case people air wire the jacks, like I'm considering.

Do you see any issues with longer leads on the jacks?

Thanks!

Edit: Some possible spots for additional standoffs, could be behind J4 and P1 near R2 and C4, and near the HID and GND pads.
post #14 of 40
Thread Starter 
Hi Holland,

Glad you got the kit ok, sounds like you have made rapid progress.

Thanks for the feedback on the standoff locations, a very valid point. With a steady hand you could add these yourself so long as you make sure you avoid the tracks on both sides of the board! The top is mostly ground plane so no issues there although your standoffs will most likely end up being grounded, no bad thing in most cases.

Re long wires on jacks, obviously the longer they are the more impedance there will be and the more susceptible they'll be to picking up noise, but keep them as short as you can and route them sensibly and don't anticipate you having any problems.

I will post links to the datasheets as soon as I can - currently recovering from a major computer failure which is making things harder than they should be. Thankfully I had a spare disk which I have put windows on so I should still be able to get at my old files.
post #15 of 40
Hey,

I finally decided to just power up the DAC and see if it worked. It was my first DIY project so I was trying to be extra safe by checking everything again and again before powering up!!!

Turns out it worked first time! I've only tested it on USB, but the USB and switching works fine.

It's too early for me to give a proper sound review of it, I will do with photos some day soon.

My final configuration was 4 TREADs to get the necessary power with a torroid in the case.

Oh, and the HID works perfectly

I post a proper review of it soon, but in the meantime, I just wanted to say thanks for all the work you put into the kit. It's been a very enjoyable project!
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