# Comments for my PCM2702 DAC layout?



## cetoole

When I missed the 1st round of Alien DAC boards, I decided to do my own board layout to best suit what I wanted. The following is what I came up with. It measures 50x26mm, and for the most part, I just copied the schematic used by the Alien DAC, dropping the BUF634 section, as I only plan to have this bus powered, replaced the regulators with the SOT23-5 versions, which allows the use of TPS79333 and TPS793475 3.3v and 4.75v fixed regulators, which are less expensive than REG101, and pin compatible. I also went to 6.4x13.3 mm film coupling caps for the output, instead of 6.3mm electrolytics. Anyways, I am looking for comments on the DAC and layout, especially ones relating to how to improve it.


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## t52

looks pretty good imo.
 one question: are the beads for the analog supplies directly under the bypassing caps on top?


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## cetoole

Quote:


  Originally Posted by *t52* 
_looks pretty good imo.
 one question: are the beads for the analog supplies directly under the bypassing caps on top?_

 

Yes.


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## MASantos

Would low value film caps cause a bass roll of? I remember from the Alien dac thread that one should use at least 4.7uf do that you have a low frequency filter.


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## steinchen

depends on the input impedance of the following stage. for an amp the value is far from critical, e.g. (@ -3dB)
 10k 2uF -> 8Hz 
 15k 2uF -> 5Hz


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## cetoole

I finally got around to having some boards made up by BatchPCB. It will be definitely easier to get the necessary vregs in SOT23-5.


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## tomb

These things are very cool! They're only 1" x 2" - about the size of a couple of postage stamps (the little ones)!


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## rds

That is very nice. How about squeezing one of those on the miniMax?


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## tomb

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_That is very nice. How about squeezing one of those on the miniMax? 
	

	
	
		
		

		
		
	


	


_

 

Nope - the fit is too tight. The regular MAX is a different matter, however.


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## tomb

The prototype boards shown above are on their way to several people right now. Things have been a madhouse at work this week, but I hope to have a preliminary BOM posted tomorrow evening. Except for the SOT-23 regs, commonality with Alien DAC parts should only be limited by the pad sizes.


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## error401

Nice work tomb, maybe a replacement for the AlienDAC project with its pesky, difficult to find SO-8 REG101s. The silk could use a bit of cleanup I guess, but other than that it looks great.

 PS. You "stole" my DAC project name! http://www.head-fi.org/forums/f6/min...ve-i-v-292673/


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## cetoole

Quote:


  Originally Posted by *error401* /img/forum/go_quote.gif 
_Nice work tomb, maybe a replacement for the AlienDAC project with its pesky, difficult to find SO-8 REG101s. The silk could use a bit of cleanup I guess, but other than that it looks great.

 PS. You "stole" my DAC project name! http://www.head-fi.org/forums/f6/min...ve-i-v-292673/_

 

I'm not tomb, but that is basically what this project was intended to be, when I missed the Alien DAC group buy, I redid the layout for my own preferences, and when I saw they were going to make more, I bought some of those, and put this on the back burner until now where the regs are getting extremely difficult to source. There is definitely a few things that need to be cleaned up, and that will happen before any more are made.

 Sorry about the name issue, I didnt even think about it. Tom an I have just been calling it the mini DAC in our emails since we started looking at actually getting boards made for it, and just stuck with it as a name. That is the problem with generic names like miniDAC, they have already been used. Guess I could go back to the name of the folder the layout files are kept in on my PC, "PCM2702 DAC".


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## error401

Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_I'm not tomb, but that is basically what this project was intended to be, when I missed the Alien DAC group buy, I redid the layout for my own preferences, and when I saw they were going to make more, I bought some of those, and put this on the back burner until now where the regs are getting extremely difficult to source. There is definitely a few things that need to be cleaned up, and that will happen before any more are made._

 

Sorry cetoole, I saw tomb's response and assumed he did it all! Silly me.

  Quote:


 Sorry about the name issue, I didnt even think about it. 
 

Totally kidding, go ahead and use whatever name you want, I don't plan on my project going anywhere, and even if it did, it's such a generic name...


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## tomb

Well, I _am_ tomb
	

	
	
		
		

		
		
	


	




. Colin and I make a great team and I feel privileged to work with him. However, I am _not _the acomplished board designer. My job is documentation and support.
	

	
	
		
		

		
		
	


	




 EDIT: Not a very good documenter at that, I guess this is another instance where I sat on the post too long before submitting it. Sorry for being redundant.


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## Citizen86

Would this board be easier to work on than the original Alien DAC? And if so... anyway some more people can get a hold of them?


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## ruZZ.il

Redundant?!? I've seen you up to this stuff at the earliest hours of the morning, and not after waking up! For the basically non-profit work both you guys do, you're certainly very dedicated(Thanks!
	

	
	
		
		

		
			





). And what too late? the prototypes haven't even been built yet


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## tomb

Quote:


  Originally Posted by *Citizen86* /img/forum/go_quote.gif 
_Would this board be easier to work on than the original Alien DAC? And if so... anyway some more people can get a hold of them? 
	

	
	
		
		

		
		
	


	


_

 

It's probably a tradeoff. We hope some parts (REG or TPS chips) will be easier to get, but they will be smaller than the SOIC-8 of the Alien. Combined with the compactness of the layout, that could mean the actual soldering may be slightly more difficult.

 Assuming the prototypes work out, we hope that a _lot_ more people "can get a hold of them" shortly.
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *ruZZ.il* 
_Redundant?!? I've seen you up to this stuff at the earliest hours of the morning, and not after waking up! For the basically non-profit work both you guys do, you're certainly very dedicated(Thanks!). And what too late? the prototypes haven't even been built yet _

 

Thanks - I woke up again.


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## cetoole

Noting the name overlap with error401's DAC project, tomb and I have been discussing possible new names, and have settled on calling this the BantamDAC.


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## tomb

A couple of updates -

 1. I've got a rudimentary webpage started with the important files developed so far - most importantly, the first cut at a BantamDAC Bill Of Materials:

TooleAudio BantamDAC

 2. Just to give you guys an idea of how small the BantamDAC really is, I did a little pic with a quarter for comparison:







 Since they're fresh in my mind after just finishing the BOM, there are some important features about cetoole's design that deserve mention:

 1. Note that the TPS79XXX series LDO's come in a TPS79475 version, with a fixed 4.75 regulated output. No ratioed resistor pair is needed. 

 2.Besides both Mouser and DigiKey having literally thousands of the TPS regs, they're only 88 cents each. That's about 1/3 the price of the former REG101's.

 Mouser has over 27,000 of the 3.3V TPS's and 2,890 of the 4.75V.
 DigiKey has over 2,100 of the 3.3V TPS's and 3,095 of the 4.75V.






 EDIT: Looks like I was mistaken on the ceramic pads - I'll make the corrections.


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## Citizen86

Looks great guys! I'm looking to build a DAC/Amp for my laptop's audio out. This would be my first DIY project though, heh....

 2 Questions:
 1. How long before you think we can order the PCB? Also, price?
 2. Are the alternatives of the TPS Regs, you think they are comparable quality, or is it worth it to spend 3x the price on the REGS used originally?

 Thanks.


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## FallenAngel

Sweet! Looking forward to it.


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## tomb

Quote:


  Originally Posted by *Citizen86* /img/forum/go_quote.gif 
_Looks great guys! I'm looking to build a DAC/Amp for my laptop's audio out. This would be my first DIY project though, heh....

 2 Questions:
 1. How long before you think we can order the PCB? Also, price?
 2. Are the alternatives of the TPS Regs, you think they are comparable quality, or is it worth it to spend 3x the price on the REGS used originally?

 Thanks._

 

1. This is highly variable and dependent on the prototypers' schedule, but I'm hoping it will go quickly. Colin has already done some pricing research and I think it will be safe to say under $5, perhaps less - but don't hold us to it, right now.
	

	
	
		
		

		
		
	


	



 2. Just MHO, but I see no benefit to the REG101's, period.


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## Citizen86

Awesome! I'll keep an eye on this thread then. Maybe I'll try to put together a simple Cmoy in the meantime


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## error401

Quote:


  Originally Posted by *Citizen86* /img/forum/go_quote.gif 
_2. Are the alternatives of the TPS Regs, you think they are comparable quality, or is it worth it to spend 3x the price on the REGS used originally?

 Thanks._

 

These selected regulators seem to best REG101 in almost every specification, and they're considerably cheaper. They have better ripple rejection, especially at HF, and lower output noise. Just be careful with them, since the max input voltage is only 5.5V. I see no reason to want the REG101 other than for higher voltage input - but since the TPS793xx uses a standard SOT23 regulator pinout, you can substitute the REG101 or just about any other SOT23 regulator you want.

 I missed them on my last 'regulator search' somehow. I don't know what it is about TI's site but I always seem to miss perfect parts when I search for things there.

 I have been using LP2985 lately myself with good success, and I think I'll switch to these - they seem to spec better and they're a few cents cheaper. If you wanted to use something else, LP2985 make a good substitute as well - it's what's used on the Opus DAC which seems to have a good reputation. It also has a high-ish input max of 16V (REG101 is 10V, TPS793xx is 5.5V), which I have made use of to power directly from my bipolar 15V supply. But really I would stick to the TPS793xx, or if you must, the REG101, since this board is not set up to handle external power anyway.

*cetoole/tomb*
I know you mentioned it earlier in the thread, but in the interest of flexibility maybe it is worth adding a header and jumper to allow external power?
 Actually, nevermind, you're right. It'd be tricky to add to your layout, and really you should have the logic gate to disable the chip when USB power is not connected anyway, which isn't appropriate to add here.


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## JamesL

Is there any decent substitute for the soic8 reg101 that is used on the alien dac?


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## cetoole

Quote:


  Originally Posted by *JamesL* /img/forum/go_quote.gif 
_Is there any decent substitute for the soic8 reg101 that is used on the alien dac?_

 

Not AFAIK, which is a large reason for the use of SOT23-5 regs on this board, and actually, a large reason Tom and I thought to finally do something with this layout.


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## Listen2this1

Colin, have you thought of making these boards fit a case? I can see my self building a Pcm2702/mini3 in the same case. It would be nice if the DAC would be 54mm 
	

	
	
		
		

		
		
	


	




. they would both fit in the http://www.hammondmfg.com/pdf/1455C1201.pdf case. It would be great for listening to my headphones at class. 

 I will build one at any size though.


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## cetoole

Its funny you mention that case, because it fits just fine. If you look at the datasheet again, 54mm is the exterior width of the Hammond 1455C cases, while 51mm is the maximum width of the PCB that can fit in the slots. The BantamDAC is 50mm wide, so it gives 0.5mm wiggle room each direction in that case. All you need to do is find some way to keep the board from sliding back, like had to be done on the Alien. You certainly could work up something to put it in a 1455C1201 with a mini3, though you would need to do something about the DC jack for charging the mini3. 

 Tom and I also have another different plan for where this could be used that we are working on.


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## digger945

So your waiting for the prototypers to build and test before releasing the pcb for a possible group buy or something?
 This looks like a fun little build.


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## tomb

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_So your waiting for the prototypers to build and test before releasing the pcb for a possible group buy or something?
 This looks like a fun little build._

 

Yes. FallenAngel has built one, but is troubleshooting a channel issue. I'm going to put one together Friday.

 Colin has changed the layout slightly - based on FallenAngel's comments. It was only a slight re-arrangement, though - fairly trivial.


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## FallenAngel

I'll have a fire lit under my tail with this project on Friday/Saturday because I want to integrate it into the same case as a Starving Student 
	

	
	
		
		

		
			





 I'll do my best to update how it goes before then.


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## LostMoogle

I gotta say that this looks pretty cool. You've got me interested so I will be looking back at this thread often and so I am self-signing me up to see when the first batch is out.


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## MASantos

Looks nice, one could cut a hammond1455 120mm case in order to make it just the right lenght to fit the mini3 and this new bantamdac! Shouldn't be too hard.


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## Citizen86

Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_I'll have a fire lit under my tail with this project on Friday/Saturday because I want to integrate it into the same case as a Starving Student 
	

	
	
		
		

		
		
	


	


_

 

That's what I was thinking as well! And with the ptp layout shouldn't be too hard to reconfigure I believe to add in the DAC later if I built the amp first (which in my case is most likely how it will happen).


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## joneeboi

I'm wondering much clearance there is above the tallest part. Rather, can the DAC be slipped into the higher slots of the 1455C801/2 such that a different board can be placed in a slot underneath it?


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## JamesL

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_I'm wondering much clearance there is above the tallest part. Rather, can the DAC be slipped into the higher slots of the 1455C801/2 such that a different board can be placed in a slot underneath it?_

 

It'll be as tall as the tallest electrolyte you put in, which will likely be 10-20mm. Even if the 'other' board is perfectly flat, with no components, it will likely not fit with the bantam in the 1455C801 - notice that there is only 14mm between the highest and lowest slots.


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## tomb

Quote:


  Originally Posted by *JamesL* /img/forum/go_quote.gif 
_It'll be as tall as the tallest electrolyte you put in, which will likely be 10-20mm. Even if the 'other' board is perfectly flat, with no components, it will likely not fit with the bantam in the 1455C801 - notice that there is only 14mm between the highest and lowest slots._

 

Yes, but FYI - I have built an Alien DAC with one 1000uf and three 330uf capacitors laid horizontal with extended leads and it tested equal or slightly better than an Alien with standard components. So, there are possibilities if you want to build one really flat.


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## JamesL

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yes, but FYI - I have built an Alien DAC with one 1000uf and three 330uf capacitors laid horizontal with extended leads and it tested equal or slightly better than an Alien with standard components. So, there are possibilities if you want to build one really flat._

 

Very true
 In fact, I already bought a case for it.. the usb connector fits flush inside if I trim a half mil off the support-pins and has about a mil on each side of a TREAD board, so heres hoping I find someway to make this work. =]
 Can't wait for the board release.


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## MASantos

I know this has been answered a dozen times, but how low can we go on the output capacitors? With such a small board, it might be possible to fit a couple of PIO caps inside the hammond 1445C801.


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## error401

Quote:


  Originally Posted by *MASantos* /img/forum/go_quote.gif 
_I know this has been answered a dozen times, but how low can we go on the output capacitors? With such a small board, it might be possible to fit a couple of PIO caps inside the hammond 1445C801._

 

Depends on the impedance of what you plug it into. The corner frequency of the filter will be 
	

	
	
		
		

		
		
	


	




, where R is the input impedance of the amp and C is the output capacitor value. You probably want to keep this corner below 10Hz.

 I wouldn't go below 2.2uF unless you know you'll be using it with a high input impedance amp only.


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## ruZZ.il

Colin, Tom, KUDOS! Another BantamDAC lives! 
	

	
	
		
		

		
		
	


	




 With Pavels C16 note, it all works first shot. A little shaving was needed, as he mentioned too, on the USB jack, but that's not much of a problem. I was worried for a bit since I broke a pin on IC1. It happened to be the NR pin, so I've still got a seemingly perfectly functional DAC. I haven't got much test equipment here, other than an old dodgy multimeter, so I'll have to take proper measurements some other time and see if I need to replace that chip.. though so far, so good.


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## tomb

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_Colin, Tom, KUDOS! Another BantamDAC lives! 
	

	
	
		
		

		
		
	


	




 With Pavels C16 note, it all works first shot. A little shaving was needed, as he mentioned too, on the USB jack, but that's not much of a problem. I was worried for a bit since I broke a pin on IC1. It happened to be the NR pin, so I've still got a seemingly perfectly functional DAC. I haven't got much test equipment here, other than an old dodgy multimeter, so I'll have to take proper measurements some other time and see if I need to replace that chip.. though so far, so good. 
	

	
	
		
		

		
		
	


	


_

 

Yay! Way to go!

 Questions, of course -
 What'd you use for CL/CR and how does it sound?


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## ruZZ.il

I'm using BGs, 47uf. It sounds pretty much like the alien does and considering the size and cost of it, thats dang good! No noise when paused and max volume (mini^3, ultrasone PL750s) These BGs are new though, and just started getting muddy (just 2 hours in). I'd like to compare it with a BG alien sometime since mine's been dissected already . Offset is pretty low, <2ma, but I don't trust this multimeter much v=4.73, 3.27. I'm not sure what implications the lack of NR on IC1 has yet though.. I'll try get a replacement soon anyway.

 Edit: just to clarify, I'm pretty certain the muddyness I mention is from the blackgates. I'm pretty familiar with it by now. From memory alone, this is pretty much how I remember an alien sounding when firing up with them, I probably wouldn't be able to tell the difference.. I'm happy with this tiny thing 
	

	
	
		
		

		
		
	


	




 I'm bobbing along to some electronic tunes right now. It has not let me down! 
	

	
	
		
		

		
		
	


	




 thanks!


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## tomb

Cool! If it sounds pretty much like the Alien at this reduced size, then cetoole has another winner!


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## tomb

The BantamDAC prototype has been declared a success! Boards have been ordered and should be available in early October.

 Pics below are of one I put together on Sunday. It took me about 4-1/2 hours, not counting scrounging around for parts.
	

	
	
		
		

		
		
	


	




 Sound is very similar to the Alien, but with the recommended 3.3uf Wima MKS's, the BantamDAC is a bass puncher with great detail. IMHO, it sounds better than the Black Gate Aliens I have built.













 [size=xx-small](click for bigger pics)[/size]

 Cetoole has altered the productions boards slightly. I'll post pics of the new layout tonight, unless Colin beats me to it today.
	

	
	
		
		

		
		
	


	




 Here are the important changes from the prototype in the photos:
Layout was altered to allow clearance from the USB connector (note the surgery around the USB socket in the pics)
A power LED was added.

 Further details will be updated in the coming weeks at the BantamDAC website: http://www.diyforums.org/BantamDAC. Our intent is to have the board and build cost, without case, limited to $25. In addition, we have a couple of unique applications planned for the BantamDAC, so stay tuned!


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## ruZZ.il

VERY clean build, Tom. Almost as if you aligned those little buggers with a laser  That must be where your time went though.. and scrounging around for parts. Say, do you use mousers custom labeling? I guess I spent the extra time there, but once I had all the bits in labeled bags, build time was around 2~3 hours.. even with being somewhat finicky about alignment, etc..


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## tomb

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_VERY clean build, Tom. Almost as if you aligned those little buggers with a laser  That must be where your time went though.. and scrounging around for parts. Say, do you use mousers custom labeling? I guess I spent the extra time there, but once I had all the bits in labeled bags, build time was around 2~3 hours.. even with being somewhat finicky about alignment, etc.._

 

Thanks - I guess that's why it takes me so long. To tell the truth, I thought that was quick.


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## MASantos

Looks great! I love the new smaller layout without all the powering options. 

 Are you considering doing kits for this?


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## tomb

Quote:


  Originally Posted by *MASantos* /img/forum/go_quote.gif 
_Looks great! I love the new smaller layout without all the powering options. 

 Are you considering doing kits for this?_

 

Thanks! Yes, we are planning on making kits (the boards will be sold separately as well), but "when" for kits depends on how much I can do in the next few weeks. We have a lot of things coming in the pipeline - this is just one of them.


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## error401

I guess you've already gone to fab, but if not you might want to connect one of the mounting holes to the ground plane and put some bare copper for an easy ground test point and connection to chassis ground. Might add a second OG point as well to make wiring easier. I should've come up with these when you first asked, but that's what prototyping is for right 
	

	
	
		
		

		
		
	


	




.

 Great work Tom and Colin, this should outperform the Alien and it's smaller.


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## tomb

Quote:


  Originally Posted by *error401* /img/forum/go_quote.gif 
_I guess you've already gone to fab, but if not you might want to connect one of the mounting holes to the ground plane and put some bare copper for an easy ground test point and connection to chassis ground. Might add a second OG point as well to make wiring easier. I should've come up with these when you first asked, but that's what prototyping is for right 
	

	
	
		
		

		
		
	


	




.

 Great work Tom and Colin, this should outperform the Alien and it's smaller._

 

Good comments!

 There isn't much room for test points. We'll document some of the pads for checking voltages, however.

 There will be a 2nd OG in the production boards.


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## error401

I meant add a bare pad around the mounting hole so the mounting screw will connect ground to the chassis, since they're currently just holes with no pad.


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## tomb

Quote:


  Originally Posted by *error401* /img/forum/go_quote.gif 
_I meant add a bare pad around the mounting hole so the mounting screw will connect ground to the chassis, since they're currently just holes with no pad._

 

Yes - I understood what you meant, but didn't address it.
	

	
	
		
		

		
		
	


	




 There are some peculiarities with the applications we have planned. One of the biggest is to have a prepared mounting position for the Bantam with traces on a new version of the Millett MAX PCB. The area where the Bantam will go is in the rear around the MAX's Power Supply portion of the board. Most of that area is AC groundplane, so it may not be a good idea to mix up the grounds. However, the ground plane is there under the mask, so a little scraping would probably ground the plane to a mounting screw if a washer was used.


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## Citizen86

Do you guys think this will be easier to build also than the Alien?


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## ruZZ.il

its much of a muchness.


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## tomb

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_its much of a muchness._

 

OK - you've got to translate that for us.


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## ruZZ.il

I actually pondered if it were actually something ever used or me being silly.. 
 I found things like these:
much of a muchness - Wiktionary
 and some others..
 It's pretty much: "Pretty much the same"


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## tomb

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_I actually pondered if it were actually something ever used or me being silly.. 
 I found things like these:
much of a muchness - Wiktionary
 and some others..
 It's pretty much: "Pretty much the same"_

 

OK, very good!

 I agree with Russ, then: much of a muchness.
	

	
	
		
		

		
		
	


	




 Actually, I don't know how he feels, but I thought the board was a little bit easier to solder than the Alien board. It seemed to me that there was less of a tendency for bridging, but it could very well be my imagination. Even if not, it has to be categorized as a "nuance" at best.

 Some things are easier - Colin mixed in 1206 parts wherever he could. So that makes things a bit easier to handle. On the other hand, the TPS regulators are harder. I was a bit taken back at how tiny those things are. So, it's probably a wash: much of a muchness.


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## pinkfloyd4ever

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_On the other hand, the TPS regulators are harder. I was a bit taken back at how tiny those things are._

 

tom you know we're putting cover sheets on the tps reports now right. mmk great i'll just send you another copy of that memo


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## Citizen86

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_I actually pondered if it were actually something ever used or me being silly.. 
 I found things like these:
much of a muchness - Wiktionary
 and some others..
 It's pretty much: "Pretty much the same"_

 

haha glad you cleared that up. I'm looking forward to this one, hope you guys make a kit that ships internationally, that would be great for people like me where it's difficult and expensive to order from more than one place


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## tomb

Quote:


  Originally Posted by *Citizen86* /img/forum/go_quote.gif 
_haha glad you cleared that up. I'm looking forward to this one, hope you guys make a kit that ships internationally, that would be great for people like me where it's difficult and expensive to order from more than one place 
	

	
	
		
		

		
			



_

 

Yep - that's the plan and definitely international. I haven't calculated it, but my guess is that international customers make up about 30% of Beezar's business.


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## tomb

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_tom you know we're putting cover sheets on the tps reports now right. mmk great i'll just send you another copy of that memo 



_

 

Where's my stapler!?


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## JamesL

Oh man.. Is there any good substitutes to the Pana FM/FC, Nichicon PW? Maybe 0.5-1mm shorter? The 12.5mm cap is gonna make for a veeery tight fit. =x


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## tomb

Quote:


  Originally Posted by *JamesL* /img/forum/go_quote.gif 
_Oh man.. Is there any good substitutes to the Pana FM/FC, Nichicon PW? Maybe 0.5-1mm shorter? The 12.5mm cap is gonna make for a veeery tight fit. =x_

 

You can save a millimeter if you go down to a 560uf 6.3V Pana FM, but that's about it. I'm sure I don't need to suggest this to you, but if your clearances are go/no-go based on a 1mm difference, you may be designing things too close.
	

	
	
		
		

		
		
	


	




 Sometimes there's that much variance in the capacitor's rubber pad or the plastic wrap.


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## ruZZ.il

you could maybe save that much by mounting it laying down on top of the dac chip ?


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## JamesL

Hehe, I like to play it close.. I didn't even look at the specsheet when I got this case, but everything is working out perfectly. 
	

	
	
		
		

		
		
	


	



 Turns out I had an extra half millimeter available in the case.


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## tomb

After listening to the BantamDAC for awhile, I have to say that cetoole was 100% right about the Wima MKS film caps. They are just tons better than Black Gates as output couplers. I can't tell whether it's the Wima's or the Bantam, but it sounds better than the VitQ Alien I built, too.

 EDIT:
 Speaking of which, that VitQ Alien bit the dust. Cetoole and I have talked about this for awhile: I've blown 3 or 4 Aliens in the last couple of months while fiddling with different output coupling caps.

 In the Alien and Bantam design (and others) the DAC chip is directly connected to the input of an amp, with only a small capacitor protecting it (the coupling cap). There are instances where plugging and unplugging the DAC exposes it to shorting from the plug, spikes, etc. We conjecture that this is what's blowing out mine and other's Alien DACs.

 I think it's prudent to always connect the USB power source first and wait awhile before connecting it to an amp. This ensures that the coupling caps are fully charged. If you always have your DAC connected to your PC and it's always on first, there seems to be little danger. I have a couple of Aliens that have lasted a year under a constant connection. However, start plugging/unplugging and fooling around with powering up the amp, DAC and connectors at different times, and it seems there's a good chance you can fry the DAC chip.


----------



## Pars

Any thoughts as to the benefit (if any) of putting small resistors in series with the outputs to help protect the DAC chip from shorts? 100 ohm or so?


----------



## ruZZ.il

Any space on there for a delay circuit? 

 ( we believe in you Colin! 
	

	
	
		
		

		
		
	


	




 )

 Tom, Thanks for those cautionary words. It may be what killed the single channel on a chip I had to replace on an alien recently. It had a switch on it, so it's not unlikely to be linked.


----------



## tomb

Well, it's just conjecture so far - and no indication that the Bantam would be susceptible. However, the precaution seems prudent and not very imposing.


----------



## Citizen86

Real good info, thanks tomb!! Something I'll definitely remember when using the DAC. And still looking forward to the Bantam!!


----------



## tomb

Quote:


  Originally Posted by *Pars* /img/forum/go_quote.gif 
_Any thoughts as to the benefit (if any) of putting small resistors in series with the outputs to help protect the DAC chip from shorts? 100 ohm or so?_

 

As it turns out, Colin had sent me an e-mail just before you made this post.
	

	
	
		
		

		
		
	


	




 I'll test it out when the boards come in. It should be easy enough to solder a couple of 100 ohm resistors in the output leads.


----------



## tomb

Based on comments from the prototypers, this is the final layout:





 Bottom:





 The changes were relatively minor, but due to the very small size of the board, some of the larger components were relocated. In summary:

1. The selected USB Type "B" jack had a conflict with C14.
 The prototypes that were built solved this by cutting away some of the metal casing of the USB jack.

 The new layout basically swaps the positions of the USB jack with C7, the large electrolytic. This places the USB jack close to the PCM chip, but all measurements indicate more than enough clearance.

2. An LED was requested.
 While an LED is not necessarily functional to the DAC, it was still felt that the visual power indication from connecting to a USB cable was a valuable feature to have. A standard 3mm LED was added and an LED resistor (R9).

3. It was noted during prototyping that using the TPS regulators required tantalums between output and ground instead of electrolytics (C11, C13).
 The new layout uses dual SMD and through-hole pads at these positions to preserve the dual compatibility with the REG101/2, if those become available again in the future. However, the TPS chips perform well and the use of the SMD ceramics and no electrolytics seems to work quite well - more convenient, too! I have remarked before that there seems no reason to persist with the REG101/2's and haven't changed that opinion.
	

	
	
		
		

		
		
	


	




4. An extra output ground wire position was requested for convenience and performance advantages in braiding and grounding output leads.

 Two "OG" positions are now on the board.

 Also, we are recommending the Wima MKS caps in all cases as the default build. Frequency response with loop-back to an M-Audio Transit is only down 0.5dB at 20Hz, and equals or exceeds the Transit's response at 20KHz. I suspect the Transit has a lower input impedance than the typical 50K pot input of our headphone amplifiers - I have not noticed any loss of bass, period - after repeated listening. On the contrary, the Wima's bass response is thumping and slamming with outstanding detail - it beats my Black-Gate-output DACs to pieces. All of a sudden, I can hear this metal sheen with the BG's that I never noticed before.
	

	
	
		
		

		
		
	


	




 The Wima's do take a while to break-in. There is a mid-bass "thickness" that is not unpleasant in the beginning, but it disappeared completely in about a week. Humble Homemade HiFi recently added Wima's to his list - it's an interesting read for their use in the Bantam and also the Millett Hybrid/MAX/MiniMAX:
Humble Homemade Hifi - Cap Review

 He reviews the MKP10's that we use on the MAX, but the MKS's for the Bantam are very similar. (MKP10's are unworkable for the Bantam, due to the size at the ratings needed.)


----------



## error401

Nice work! I haven't tried it, but do you think maybe an LED on the /SSPND pin is more useful than a generic power LED? It should give more information about system status.


----------



## tomb

Quote:


  Originally Posted by *error401* /img/forum/go_quote.gif 
_Nice work! I haven't tried it, but do you think maybe an LED on the /SSPND pin is more useful than a generic power LED? It should give more information about system status._

 

Good suggestion, but - 

 the BantamDAC boards have arrived(! 
	

	
	
		
		

		
		
	


	




 ) and will be available for purchase this weekend.


----------



## JamesL

woah, I didn't see that coming!..
 Sign me up!


----------



## Citizen86

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Good suggestion, but - 

 the BantamDAC boards have arrived(! 
	

	
	
		
		

		
			





 ) and will be available for purchase this weekend. 
	

	
	
		
		

		
		
	


	


_

 

Well I'm excited! When do you think you will have kits ready? (If you are planning on doing that)


----------



## tomb

It seems I caused a bit of a row over on Headwize, due to my use of the word "tantalum" relative to the TPS regulators. Admittedly, I made that huge post from memory and I can't tell the difference visually between an SMD tantalum and an SMD ceramic. Ceramic it is, and I've now edited it - but the important point was that electrolytics are not mentioned in the TPS datasheets. The ceramic cap we used and have specified in the BOM is exactly what the datasheet recommended.

  Quote:


  Originally Posted by *Citizen86* /img/forum/go_quote.gif 
_Well I'm excited! When do you think you will have kits ready? (If you are planning on doing that) 
	

	
	
		
		

		
		
	


	





_

 

No kits. I checked into the pricing and I can't sell them for enough to fund the up-front costs for buying all the parts. I just don't have that kind of buying power with Beezar.

 However, the BOM totals to less than $25 and the boards will be very, very cheap.

 There are a few special items that I will stock for it, however, such as the main power cap. The Pana FM is really the best cap in that position, but just about all of the other parts are more economical from Mouser. So, that's an opportunity to help people out with the multiple sources problem and is one of the primary charters for starting Beezar.

 There is also a very nice - and tiny(!) - box that is just perfect as a case for the Bantam. It will also serve well for making a USB Cable-DAC with the Bantam, too. So, I hope to carry those boxes and perhaps the USB pigtail cables, as well.


----------



## Citizen86

Well that works for me. I'm willing to buy from Mouser if it's only going to be from Mouser and Beezar 
	

	
	
		
		

		
		
	


	




 Great job guys, I'm looking forward to this after I get my Starving Student up and running


----------



## JamesL

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_There is also a very nice - and tiny(!) - box that is just perfect as a case for the Bantam. It will also serve well for making a USB Cable-DAC with the Bantam, too. So, I hope to carry those boxes and perhaps the USB pigtail cables, as well. 
	

	
	
		
		

		
		
	


	


_

 

You thinking the same thing I'm thinking?


----------



## tomb

Quote:


  Originally Posted by *JamesL* /img/forum/go_quote.gif 
_You thinking the same thing I'm thinking? 
	

	
	
		
		

		
		
	


	






_

 

That looks like it! Box Enclosures #RX2KL07-S


----------



## JamesL

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_the BantamDAC boards have arrived(! 
	

	
	
		
		

		
		
	


	




 ) and will be available for purchase this weekend. 
	

	
	
		
		

		
		
	


	


_

 

Where is it! Where is it!!!? 
	

	
	
		
		

		
		
	


	




... 
	

	
	
		
		

		
		
	


	



 It's sunday!

 I need to build something badly..


----------



## tomb

Quote:


  Originally Posted by *JamesL* /img/forum/go_quote.gif 
_Where is it! Where is it!!!? 
	

	
	
		
		

		
		
	


	




... 
	

	
	
		
		

		
		
	


	



 It's sunday!

 I need to build something badly.. 
	

	
	
		
		

		
		
	


	


_

 

The BantamDAC will be on beezar.com sometime tonight. I've been working constantly on the website, so that you guys at least have something to go by to build one.
	

	
	
		
		

		
		
	


	




 Please be patient - I'm pedaling as fast as I can.


----------



## JamesL

=D 

 *goes to beezar*...
 refresh...
 refresh...

 ...
 refresh
 ...

 Actually, are you planning on stocking the FM's today?
 I just made 2 digikey orders, and I'll probably use the FC's otherwise.


----------



## tomb

Quote:


  Originally Posted by *JamesL* /img/forum/go_quote.gif 
_=D 

 *goes to beezar*...
 refresh...
 refresh...

 ...
 refresh
 ...

 Actually, are you planning on stocking the FM's today?
 I just made 2 digikey orders, and I'll probably use the FC's otherwise._

 

I can't - DigiKey is out until October 7.


----------



## tomb

This will remain a work in progress for awhile, but the BantamDAC website is up and running. 
	

	
	
		
		

		
		
	


	




 BantamDAC PCB's are now available at you-know-where.
	

	
	
		
		

		
		
	


	








*NOTE: If any of you are speedy at ordering and building, C16 must go in the R8 position when using TPS regulators (R7 and R8 are not used at all).*


----------



## error401

Nice! Great price, good work guys!


----------



## Citizen86

$2 for the board??? Man, you guys are killing us 
	

	
	
		
		

		
		
	


	




 Nice website for the DAC, very nice. I'll probably put an order in near the end of the month...

 Edit: Reading the history, I had no idea this thread originated in 2006....... wow. Anyways, glad this board finally came into fruition! hehe


----------



## tomb

Thanks for the comments, guys! I'll try to have the rest of that website filled in by the end of the weekend.

 Meanwhile, just in case - another parts change I forgot to update on the production BOM:

*C11 and C13 were upsized to 1206 parts for the production boards.*

 You will note that those are dual SMD/through-hole pads to maintain compatibility with REG chips if those ever become available again. Even though we don't believe the market will run out of TPS regs anytime soon, you never know about the future.
	

	
	
		
		

		
		
	


	




 Regardless, this keeps the flexibility in place.


----------



## GeWa

Yikes, believe it or not but I was just in the process of making my order ready for Mouser!! Any other stuff that have or will change?

 BTW, congrats on the Bantam pages man.

 Regards

 [size=xx-small](P.S. Beezar.com can expect an order from me also)[/size]


----------



## patton713MW

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Meanwhile, just in case - another parts change I forgot to update on the production BOM:

*C11 and C13 were upsized to 1206 parts for the production boards.*_

 

Have these changes been made on the BOM on the website?


----------



## GeWa

Yes.


----------



## LowFi

Hi! New user here, I am filling out a BOM at mousers for a BantamDac or two. When searching for the regulator (IC1) i came across this one: TPS79333DBVRQ1, wich appear to be the same as the one in the BOM, but a newer model.

 Just wanted to double check if this one will do? 
 you aslo save a whopping 10cents to change it. breathtaking i know.


----------



## GeWa

It looks like a good contender, also the fact that one can save a bundle of money is an additional benefit.
	

	
	
		
		

		
			





 Regards


----------



## MASantos

tomb, I con't open some of the pages in the bamtamdac site, such as the one regarding building it as a cabledac. Is this normal or am I experiencing problems?

 Manuel


----------



## GeWa

I think the poor guy is still working on some of the pages.

 Regards


----------



## tomb

Quote:


  Originally Posted by *MASantos* /img/forum/go_quote.gif 
_tomb, I con't open some of the pages in the bamtamdac site, such as the one regarding building it as a cabledac. Is this normal or am I experiencing problems?

 Manuel_

 

Must be just you Manuel. 
	

	
	
		
		

		
		
	


	










 Seriously, GeWa is correct. From post #89 awhile ago:
  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Thanks for the comments, guys! I'll try to have the rest of that website filled in by the end of the weekend.</snip>_

 

There's enough up there right now for you pro-builders. I'll try my best to have the rest of it this weekend. There's only so much I can do without sitting down, building another one, and taking photographs along the way - that more or less takes another weekend before my day job is not in the way (it's a shame how that happens). Maybe I should've put an "under-construction" for those pages, but that's almost as much trouble for me to go ahead and do the pages.
	

	
	
		
		

		
		
	


	




 I will update this thread and on DIYForums.org as more pages/details become available.


----------



## MASantos

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Must be just you Manuel. 
	

	
	
		
		

		
		
	


	










 Seriously, GeWa is correct. From post #89 awhile ago:


 There's enough up there right now for you pro-builders. I'll try my best to have the rest of it this weekend. There's only so much I can do without sitting down, building another one, and taking photographs along the way - that more or less takes another weekend before my day job is not in the way (it's a shame how that happens). Maybe I should've put an "under-construction" for those pages, but that's almost as much trouble for me to go ahead and do the pages.
	

	
	
		
		

		
		
	


	




 I will update this thread and on DIYForums.org as more pages/details become available.
	

	
	
		
		

		
		
	


	


_

 

That's what I tought! Now go away from head-fi and finish those pages!!!
	

	
	
		
		

		
		
	


	







 I'm not building one ATM since my bugdet for DIY is pretty low, but I'll keep an eye on it!

 Looks good!

 ps: have you found any "boutique" film caps that might fit a hammond 1455c801 enclosure? I guess the main problem might be the diameter of the cap, but having one of these with nice PIO caps might be worthy. What do you guys think?


----------



## tomb

Quote:


  Originally Posted by *MASantos* /img/forum/go_quote.gif 
_That's what I tought! Now go away from head-fi and finish those pages!!!
	

	
	
		
		

		
		
	


	







 I'm not building one ATM since my bugdet for DIY is pretty low, but I'll keep an eye on it!

 Looks good!

 ps: have you found any "boutique" film caps that might fit a hammond 1455c801 enclosure? I guess the main problem might be the diameter of the cap, but having one of these with nice PIO caps might be worthy. What do you guys think?_

 

Well, putting one of these into a Hammond 1455C801 leaves a heckuva lot of room for boutique caps. I certainly would encourage anyone to try other boutique caps when using such a configuration (you have the room). Multiple parallel VitaminQ's certainly worked well with the Alien. If 6 x 0.22uf VitQ's fit in a mint tin, then maybe they'd stagger in a 1455C801, too - but I haven't tried it, yet.

 I'm looking at the Box Enclosure RX2KL07-S case as the standard BantamDAC enclosure. I have a couple of those in hand and will be attempting to case a couple of Bantams this weekend. Looking at the cases and comparing them to the actual built board, it seemed that the Bantam would fit. However, referencing the actual dimensions and the recommended Pana FM 1000uf/6.3V electrolytic indicates that there may not be enough headroom. So, the safest thing is to let me attempt it, first. I'll report back when I know.


*P.S. Please note that the C11 and C13 SMD caps have been revised to a much less expensive part #.*


----------



## tomb

I haven't done anymore building tonight, but I did make extensive measurements of the sample cases I'm going to use - to make absolutely sure that things will fit (they will!).

 The recommended case, for both a traditional configuration and a CableDAC, is the Box Enclosures "Precision Miniature Case," #*RX2KL07-S.* These are available at Allied and Newark (when in stock) and directly from Box Enclosures. Beezar will also carry them in a few days.
	

	
	
		
		

		
		
	


	




 Also, a question came up about the smaller electrolytic - C12. The uf rating of this cap is not critical. You will note that the description mentions a 68uf cap, but up to 330uf is OK, if it will fit. The idea is to put a cap there with as low ESR as possible. Typically, this is where an Os-Con has often been used. The Mouser number on the BOM is for a 220uf, low-cost alternative to an Os-Con, but with identical construction (super-low ESR, gel-electrolyte). The Mouser part number for C12 is our primary recommendation.


----------



## Nicolas2305

Hi there, I've just read the whole thread because I'm searching for a DiY DAC to build to go along with a Mini^3. I don't intend to put the DAC into the Mini^3 case because I want to use the Mini^3 with my portable player. 

 I'm the noobest of the noobs in the DiY community and wondered if I could manage to build this after building only a Mini^3. I'd surely order few boards with all the parts required and if I don't mess up I'll end up with few bantam DAC.

 Edit: I also wonder why you didn't use a mini USB instead of the full size B-type USB?


----------



## tomb

Quote:


  Originally Posted by *Nicolas2305* /img/forum/go_quote.gif 
_Hi there, I've just read the whole thread because I'm searching for a DiY DAC to build to go along with a Mini^3. I don't intend to put the DAC into the Mini^3 case because I want to use the Mini^3 with my portable player. 

 I'm the noobest of the noobs in the DiY community and wondered if I could manage to build this after building only a Mini^3. I'd surely order few boards with all the parts required and if I don't mess up I'll end up with few bantam DAC.

 Edit: I also wonder why you didn't use a mini USB instead of the full size B-type USB?_

 

ruZZ.il has a great post in the Aussie BantamDAC Group Buy thread right now. I suggest you refer to that for an un-biased take on things.

 As for building this if you built a Mini3, unfortunately, the skills needed to solder the PCM2702 at SSOP-28 are much more difficult than the SOIC-8 opamps in the Mini3. The TPS chips are also a bit more difficult than the SOIC-8 REG101's in the Alien. That said, I am preparing a much higher-level of "how-to" than existed for the Alien, so I hope that will help. Certainly, many people have successfully built an Alien. The BantamDAC is very slightly more difficult - mostly because of the small size (less room to move around). 

 As for a mini USB, we considered it, but there's little to gain considering that the one power electrolytic is taller than the Type B USB jack, anyway. Ultimately, the Type B is more robust, especially if mounting the BantamDAC board into a case such as the Millett MAX. Plus, I'm predicting that the BantamCableDAC build option will remove most of the desire for having a mini-USB anyway.


----------



## Gross

I used up all of my Aliens, So once caps and cases are in stock, you can count me in for an order at beezar.


----------



## tomb

Well, the BantamCableDAC is a success! I built this one using BG's and it sounds just like an Alien DAC, perhaps a bit better, but I'm biased, obviously.

 I'll have lots of pics tomorrow.


----------



## Citizen86

So by cable dac, you mean SPDIF or optical in as well?


----------



## Forte

TomB, Apart from the board and the Panasonic Cap are you planning to carry any other parts at Beezar?


----------



## ruZZ.il

Quote:


  Originally Posted by *Citizen86* /img/forum/go_quote.gif 
_So by cable dac, you mean SPDIF or optical in as well?_

 

No, The BantamDAC is still strictly USB input, by design.

 You'll have to look elsewhere to have those features in a DAC.. but it wont come at the same price


----------



## tomb

Quote:


  Originally Posted by *Forte* /img/forum/go_quote.gif 
_TomB, Apart from the board and the Panasonic Cap are you planning to carry any other parts at Beezar?_

 

Yes - I will be carrying the Wima caps, the Box Enclosure cases and the USB pigtail cables. I may also carry the United ChemCon low-ESR gel cap. There's nothing special about any of those except the cases are only in stock at Newark or directly from Box Enclosures themselves. Allied also carries them, but they're normally a special order, I think. The USB pigtails are available at Mouser, but I'd like for everyone to be sure to select one that's shielded. The Wimas and the United Chemcon gel cap are also at Mouser, but Beezar has a lot of international customers where Mouser's shipping is prohibitively expensive.


----------



## error401

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The USB pigtails are available at Mouser, but I'd like for everyone to be sure to select one that's shielded._

 

USB specifies a shielded cable, so you shouldn't really have to worry about that, an unshielded cable is not compliant and can't use the name.

 Good of you to carry the other stuff though, especially the enclosure (DigiKey carries the rest and has good shipping to a lot more places than Mouser).


----------



## tomb

Quote:


  Originally Posted by *error401* /img/forum/go_quote.gif 
_USB specifies a shielded cable, so you shouldn't really have to worry about that, an unshielded cable is not compliant and can't use the name.<snip>_

 

Sub-channel vs. full-rated makes the difference. You can select one or the other at Mouser and DigiKey. A sub-channel USB cable is _not required_ to have shielding. There are other differences, too. I think we're better off with full-rated.


----------



## GeWa

Quote:


 I built this one using BG's and it sounds just like an Alien DAC 
 

Which type BG and what value did you used here?

 Regards


----------



## tomb

Quote:


  Originally Posted by *GeWa* /img/forum/go_quote.gif 
_Which type BG and what value did you used here?

 Regards_

 

BG NX-HiQ, 47uf 6.3V.


----------



## Citizen86

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_No, The BantamDAC is still strictly USB input, by design.

 You'll have to look elsewhere to have those features in a DAC.. but it wont come at the same price _

 

Alright, well then everyone is going to have to excuse my ignorance, please... but what is the cable dac mod going to do then?


----------



## rhester

Instread of having a USB connector on the borad, the usb cable will be directly conneccted to the dac. less coneections so sound should be a lil better and more convenient since you will not need a usb cable.


----------



## Citizen86

I see, thanks for the quick reply!


----------



## tomb

Ask a question - 
	

	
	
		
		

		
		
	


	




 The BantamCableDAC is a variation on building the BantamDAC. Essentially, the USB Type B jack is left unpopulated. The selected case, Box Enclosures #RX2KL07-S, is very small - 2.48x1.10x0.63" inside dimensions - and light. This allows one to wire the case directly into the ends of a USB cable and to terminate the other side with standard leads and RCA jacks. In one fell swoop, you've eliminated any plug-in connection to the BantamDAC board, and eliminated any patch cords in connecting the BantamDAC to an amp.

 I drilled the Box Enclosure in seven places:
Four holes for 4-40 screws on the bottom of the case for the board mounting holes
Two 1/4" holes on both ends at approx. mid-height on the case, and
One 3mm hole for the LED in the case lid.

 The case itself is closed up with four tiny Phillips screws at the four corners on the top (provided with the Box Enclosure). On the ends, I put a rubber grommet in each hole to act as a strain relief. The cables on both ends are extremely tight. My guess is that the case will crack before the cables will pull out, despite any lack of hard clamp on the interior side of the grommets.

 Wiring the USB cable into the board is a piece of cake. USB wiring is an international standard - all wiring positions are defined down to the color:







 (Note that the BantamDAC board is the same as the diagram for "B". A Type B jack simply turns those wire positions 90 degrees.)

 The trick becomes wiring the board with the cables routed through the grommets on the ends. Pulling slack was not too difficult, but taking the slack back out while pushing the board back down into the case onto the mounting screws was a bit difficult. Smaller wiring on the RCA Jack side would probably make this easier. Also, there's a 1/6" nylon washer underneat each mounting hole. This corrects for the thickness of the C8 SMD cap on the bottom of the board, which is the thickest part on the bottom of the board (you don't want to stress the board by clamping down over that SMD cap in the middle).

 Finally, mark the hole in the lid for the LED (after soldering the LED at the proper height) and screw the lid on. Voila - BantamCableDAC!


----------



## tomb

Here are some results of RMAA testing for the BantamCableDAC with BG's versus an Alien DAC w/BG's (one of my Penguin Mint Tin Aliens):

RightMark Audio Analyzer test: comparison of BantamCableDAC with the Alien DAC (both with BG NX-HiQ's on output)

 Keep in mind that my setup is far from ideal. I have a bunch of wireless powering my keyboard, mouse, and other items. Cable differences and location of the test can make huge differences. In addition, it's fairly easy to game certain aspects of RMAA, IMHO. Depending on how you set levels, you can vary distortion relative to signal-to-noise. However, the comparison is valid because the test for both DACs was made under the same conditions.

 The only purpose for posting the results of the test is to demonstrate that the BantamDAC is functionally equal to the AlienDAC, perhaps a tad better in some respects.


----------



## Citizen86

Well there's a good answer 
	

	
	
		
		

		
		
	


	




 That looks very do-able, looks great as well! I was thinking of trying to stick this DAC in with my Millett Starving Student, but I think the CableDac looks good, plus I'd be able to use it with more than one amp.


----------



## 00940

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_You can see the full details and a couple of other graphs at the link given above. Keep in mind that my setup is far from ideal. I have a bunch of wireless powering my keyboard, mouse, and other items. Cable differences and location of the test can make huge differences. However, the comparison is probably valid because the test for both DACs was made under the same conditions.
	

	
	
		
		

		
		
	


	


_

 

Ok, I was wondering why the results were so bad... Amb measurements of the Alien are far better and so were the measurements of the usb dac I designed with Guzzler.


----------



## tomb

Quote:


  Originally Posted by *00940* /img/forum/go_quote.gif 
_Ok, I was wondering why the results were so bad... Amb measurements of the Alien are far better and so were the measurements of the usb dac I designed with Guzzler._

 

Yes, well, not many of us have the extent of AMB's equipment.
	

	
	
		
		

		
		
	


	




 It's fairly easy to game certain aspects of RMAA, IMHO, too - which is why I felt that comparisons are what's important. As evidence, these are much better measurements than most of the RMAA results posted by users in the Alien DAC thread. In particular, the AlienDAC got a bad rap from some of our more experienced members as having a steep roll-off at 15KHz. One can see that this is not true. It's also easy to see that the BantamDAC is a functional equivalent of the Alien, if not a tad bit better in some aspects.


----------



## 00940

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_It's fairly easy to game certain aspects of RMAA, IMHO, too - which is why I felt that comparisons are what's important._

 

For sure... I always wondered how long the engineers at TI had worked to get the -100dB measurements they claim for the pcm2702. 

 Good work on this pcb anyway. It looks really clean (certainly cleaner than the USB DAC sitting in a tin on my desk).


----------



## error401

How feasible do you think it'd be to use the Box Enclosures case with a 'standard' non-Cable DAC?


----------



## tomb

Quote:


  Originally Posted by *error401* /img/forum/go_quote.gif 
_How feasible do you think it'd be to use the Box Enclosures case with a 'standard' non-Cable DAC?_

 

Completely feasible.
	

	
	
		
		

		
			








 That's the regular case option, too - just haven't documented that one, yet. Essentially, one just needs to take a razor saw to the plastic to cut out a notch for the USB jack.


----------



## error401

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Completely feasible.
	

	
	
		
		

		
		
	


	







 That's the regular case option, too - just haven't documented that one, that. Essentially, one just needs to take a razor saw to the plastic to cut out a notch for the USB jack._

 

Excellent! Awaiting the arrival of the Box Enclosures on Beezar


----------



## tomb

Still quite a few pages left to do, but I've added some extensive Step-by-Step Construction and Preparation pages on the website - under "Construction". 
	

	
	
		
		

		
		
	


	




http://www.diyforums.org/BantamDAC


----------



## MASantos

Jantzen 4.7uF 400V Crosscap Capacitor fits the hammond case.

 TPA used this brand of capacitor in their kokaburra pre amps just as a pointer and brian recomended me these as output caps for an opus dac, anyone want's to give them a try?


----------



## tomb

Quote:


  Originally Posted by *MASantos* /img/forum/go_quote.gif 
_Jantzen 4.7uF 400V Crosscap Capacitor fits the hammond case.

 TPA used this brand of capacitor in their kokaburra pre amps just as a pointer and brian recomended me these as output caps for an opus dac, anyone want's to give them a try?_

 

They look like they might be re-branded Solen's - the physical size is similar, too. If that's the case (not saying for sure that it is), then there are better caps to pick from.

 Honestly, I can't imagine a PCM2702 DAC with direct output capacitor coupling sounding better than with VitaminQ's. I have that one Alien DAC with 6 x 0.22uf on each channel (it died I thought, but miraculously came back to life). That's 0.66uf and there's no loss of bass, while the sound is great. Maybe a Mundorf would sound better, but those are out of my price range.
	

	
	
		
		

		
		
	


	




 EDIT: This is of course, if we are talking about something advanced. The BG's and film caps sound just great within the footprint of the BantamDAC board. What we're talking about with Jantzens, VitQ's and Mundorf's is an _extreme_ build.


----------



## MASantos

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_....What we're talking about with Jantzens, VitQ's and Mundorf's is an extreme build.
	

	
	
		
		

		
		
	


	


_

 


 yada yada blackgates yada yada wimas....

 tomb, what would head-fi be without a few momentary insanity moments where you spend more on the output caps that the rest of the parts???


----------



## tomb

Quote:


  Originally Posted by *MASantos* /img/forum/go_quote.gif 
_yada yada blackgates yada yada wimas....

 tomb, what would head-fi be without a few momentary insanity moments where you spend more on the output caps that the rest of the parts???
	

	
	
		
		

		
		
	


	








_

 

True.


----------



## FallenAngel

That's why you buy some 1uF VitaminQ of ebay and use the DAC with 50k impedance amps


----------



## Nemo de Monet

I've now built two BantamDACs, having received the bits last week; the working one is, as has been said before, very much like an Alien (of which I've built two), only much smaller. Thanks for making an alternative DAC that's easier to integrate with DIY amplifiers!

 The non-functioning one, incidentally, is a classic example of the risks of being an 'early adopter' of new technology: when I built it last Friday, the construction pages for the Bantam hadn't been created yet, so - silly me - I put c16 in the obvious position. Doh! Now, having rectified that - and having figured out why the 4.75v regulator went "poof" - as soon as Mouser delivers a new regulator, I should have *two* working Bantams, bwahahahaha...

 One will wind up feeding an "original SOHA", I'm not sure about the other. Maybe I'll put it - and some enormous 4uf KGB PIO caps - in a case with a spare Pimeta, or something...


----------



## tomb

Quote:


  Originally Posted by *Nemo de Monet* /img/forum/go_quote.gif 
_I've now built two BantamDACs, having received the bits last week; the working one is, as has been said before, very much like an Alien (of which I've built two), only much smaller. Thanks for making an alternative DAC that's easier to integrate with DIY amplifiers!

 The non-functioning one, incidentally, is a classic example of the risks of being an 'early adopter' of new technology: when I built it last Friday, the construction pages for the Bantam hadn't been created yet, so - silly me - I put c16 in the obvious position. Doh! Now, having rectified that - and having figured out why the 4.75v regulator went "poof" - as soon as Mouser delivers a new regulator, I should have *two* working Bantams, bwahahahaha...

 One will wind up feeding an "original SOHA", I'm not sure about the other. Maybe I'll put it - and some enormous 4uf KGB PIO caps - in a case with a spare Pimeta, or something..._

 

Glad to hear that at least one went together well.

 On the other hand, I am so sorry that the C16 tripped you up. I made a post in this thread in BOLD about that, but we can't expect that everyone will read all of these posts, either. I will try to emphasize it everywhere I can - even putting it on Beezar on the catalog page.

 Colin and I debated the silkscreen before ordering the production boards. However, we felt the dual-compatibility with the REG101's was important. The prospect of labeling that one pad with C16 and making alternate silkscreen labels for three pads was daunting. So, we decided to leave it as is. My fault for not making the change clear enough.


----------



## Nemo de Monet

Yeah, and I *read* that post, too - I've been following this thread pretty closely for a few weeks, had my parts ordered back before the "final" BOM was out (oops!), and was one of the many who kept re-visiting Beezar looking for the boards that joyous weekend - but it was late at night/very early in the morning, and I kind of saw "REG101" and didn't really pay any attention, as I didn't think it was relevant. 
	

	
	
		
		

		
		
	


	




 I'm not blaming you; I jumped the gun, and the time I spend wondering "but *why* did IC2 go kerplooey?" is entirely my own fault...


----------



## ruZZ.il

hey you learned what (not) to do next time! 
	

	
	
		
		

		
		
	


	



 we've all somehow been there abouts...


----------



## joneeboi

I hope to make my order before the end of the day at Digikey (for that oh, so sweet next-day shipping), but it seems R4's 541-1.00MCCT-ND and C7's P12340-ND from the BOM are backordered. Just thought at least one person might like to know. I switched to Nichicon PW (493-1707-ND) for C7 and Panny for R4 (P1.00MCCT-ND).


----------



## luvdunhill

Tom: are you going to offer a kit?


----------



## tomb

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_Tom: are you going to offer a kit?_

 

I sort of doubt it in the near term. There's very little price break in volume for most of the parts. Plus, we've geared the boards and selected the BOM to be as cheap as possible - $2 and less than $25, respectively. I would probably have to sell at higher than that $25, which would ruin our biggest bragging point.
	

	
	
		
		

		
			





 Beezar will carry, starting this weekend:
the low-ESR gel cap,
the Box Enclosure, and
the shielded, full-rated USB pigtail cables.
That's mostly because many of Beezar's international customers have trouble with Mouser's international shipping costs (evidence Joneeboi's post). In the case of the Box Enclosure, they're not even available at Mouser or DigiKey. I'm also trying to carry the Pana FM power cap for similar reasons if DigiKey would ever get more stock. (Most US customers would order from Mouser, leaving out the excellent Pana FM cap.) They'll be overdue from Panasonic by 10 days tomorrow.
	

	
	
		
		

		
		
	


	




 I'm not really anticipating carrying any of the SMD parts - for the time being. The PCM2702 is phasing out at Texas Instruments, but there are still hundreds in the inventory at Mouser (781 with >2000 in 10 days), DigiKey (919), and elsewhere. The TPS chips number in the thousands, perhaps tens of thousands counting various differing part numbers.

 Any of this could change if I start getting feedback to the contrary, however. If international customers start having difficulty with the PCM or TPS's, it would make sense to just start carrying kits at that point. That's not that I'm pre-disposed in any way to international vs. domestic customers, but as indicated, US customers can do the whole thing for less than $25 by ordering from Mouser directly.


----------



## luvdunhill

yeah, but beezar isn't on the wife's radar like Mouser is 
	

	
	
		
		

		
		
	


	




 good to know though. I for one wouldn't want to stock kits with SMD parts either... I've had lots of problems with Panasonic parts in general from Digikey, so good luck there. They're discontinuing all the Panasonic 1% polypro film caps, which is sorta annoying. The replacement part is a 5% tolerance SMD part...


----------



## error401

Didn't realize the PCM2702 was NRND 
	

	
	
		
		

		
		
	


	




. Wonder how they managed to get it to spec so much better than the rest of the series. Anyone actually measured real-world comparisons between the different chips?

 I guess amb and MisterX's gamma1 project becomes even more relevant in the not-so-distant future.


----------



## tomb

Quote:


  Originally Posted by *error401* /img/forum/go_quote.gif 
_Didn't realize the PCM2702 was NRND 
	

	
	
		
		

		
		
	


	




. Wonder how they managed to get it to spec so much better than the rest of the series. Anyone actually measured real-world comparisons between the different chips?

 I guess amb and MisterX's gamma1 project becomes even more relevant in the not-so-distant future._

 

Golly, I sure have to be careful what I post in this thread.
	

	
	
		
		

		
		
	


	




_Au contraire!_ - cetoole will modify the Bantam layout to accept the PCM2704 or PCM2705 when supplies of the PCM2702 run thin. We've already been planning for that - but again, with almost 1000 at DigiKey and almost a similar number at Mouser, that's not going to be happening anytime soon. I would expect that to be a year or two, at least - especially since we and the Alien may be one of the few applications with TI claiming NRND.


----------



## cobaltmute

If you look at the TI page on the PCM2702, TI is stating they have 2051 in stock as of today with ">10K" in progress.


----------



## Forte

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Any of this could change if I start getting feedback to the contrary, however._

 

Hi, As far as suppliers go in Australia a lot of parts would be a problem. Farnells carry a PCM2702EG4(Is this the same?) but only 1 of the 2 TPS's. As to the SMD parts could not find most of these in the correct values. Gave up looking at the rest after that.

 I would have no problem paying a premium(preferably a small one
	

	
	
		
		

		
		
	


	




) for a kit from Beezar. My last Mouser order cost $45 
	

	
	
		
		

		
		
	


	




 for shipping, my Beezar order for Max parts only $9.40 
	

	
	
		
		

		
		
	


	




 for shipping.

 So if it was $2 for board, $25 for BOM and $10 for shipping thats still less than Mouser shipping alone!

 Put me down for the first kit if you change your mind!


----------



## tomb

Quote:


  Originally Posted by *Forte* /img/forum/go_quote.gif 
_Hi, As far as suppliers go in Australia a lot of parts would be a problem. Farnells carry a PCM2702EG4(Is this the same?) but only 1 of the 2 TPS's. As to the SMD parts could not find most of these in the correct values. Gave up looking at the rest after that.

 I would have no problem paying a premium(preferably a small one
	

	
	
		
		

		
		
	


	




) for a kit from Beezar. My last Mouser order cost $45 
	

	
	
		
		

		
		
	


	




 for shipping, my Beezar order for Max parts only $9.40 
	

	
	
		
		

		
		
	


	




 for shipping.

 So if it was $2 for board, $25 for BOM and $10 for shipping thats still less than Mouser shipping alone!

 Put me down for the first kit if you change your mind!_

 

Hmm ... I'll keep it in mind. Maybe after the MiniMAX Case Group Buy is over and done with, I might be able to consider it.


----------



## luvdunhill

Tom:

 Do you feel that an isolator for the crystal is in order? I've always used them, but did it because there very first project I built with one speced one out, so I just did it by habit after that.


----------



## tomb

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_Tom:

 Do you feel that an isolator for the crystal is in order? I've always used them, but did it because there very first project I built with one speced one out, so I just did it by habit after that._

 

Colin will have to answer that one, I don't really know.

 There were crystal spacers included on a single Alien DAC BOM early in the Alien thread, but as far as I can remember, there was never a single reference to them from anyone, nor were they used in any of the builds. I actually still have a set from my first Alien DAC order, but never used them and still haven't. My guess is that they're probably needed for portable use where shocks are common or on a big board with other crystals, but I doubt their usefulness on something like the BantamDAC.

 Most likely he will see this, but I'll send him an e-mail, anyway.


----------



## GeWa

My order from Beezar.com has arrived. I must say that those BantamDAC boards look reaally small !!

 Regards


----------



## joneeboi

My new tools from Spark Fun Electronics came in Thursday and my Digikey order Friday, but I don't have any boards to work with. 
	

	
	
		
		

		
		
	


	




 I have midterms two and three Mondays from now, so the next two weekends are out of the question for me. Maybe I could crunch out the build in a morning before leaving for school...


----------



## cetoole

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_Tom:

 Do you feel that an isolator for the crystal is in order? I've always used them, but did it because there very first project I built with one speced one out, so I just did it by habit after that._

 

Yeah, I saw this, and I got Tom's email. My understanding is that those mylar spacers are for electrical isolation, as opposed to vibration damping. There isnt actually much this could do for vibration, as the xtal leads are hard soldered to the PCB. Basically, the xtal is in a metal can which can short traces on the PCB if it scratches through the solder stop mask. In the case of the BantamDAC, the xtal is sitting mostly on a groundplane, but there are also the XTI and XTO (oscillator IO) traces to the PCM2702 running under it, so potentially one of these could get shorted to ground, or possibly to each other. This seems very unlikely to me, but I guess it is possible. I say use 'em if you got 'em, but dont worry about it if you dont.


----------



## royewest

My parts arrived over the past week. What with travelling and my kid's birthday and work (of all things), I only got to solder it all up today.

 tomb's instructions are just great and it all went together without a hitch. Sounds great, too! Thanks cetoole and tomb for making this astonishing and cheap gem available!

 __Roy


----------



## royewest

I just finished another Bantam DAC, this time as a BantamCableDAC ( BantamCableDAC ). I'm sure it sounds great, but my wife snatched it immediately and I haven't had a chance to listen for more than 20 seconds after making sure music came out. I'm letting her break it in for me -- yeah, that's it.

 It's a great and minimalist companion to my Mini^3 amp. I'll probably figure out a way to build them together into the same chassis one day...

 In any event, if I can make two of these anyone can do it. The first one I made still sounds just great. As I posted earlier, I have DACs that cost 20X that do sound better, but man, not 20X better.

 Two slight differences from the BantamCableDAC as shown on the project site:

 * I used a 3.5 mm Neutrik stereo plug instead of RCAs, so I can more simply connect it to my Mini^3 amp

 * I cut a U rather than a hole in each end of the beezar.com supplied plastic box, which made it much simpler to fit the whole thing together. About 1% less professional looking if you really stare at it, but fine by me. I'll probably add some zip ties for strain relief in a day or two, also because I didn't bother to bolt the board to the box (my local hardware store didn't have nylon bolts smaller than 6 this afternoon).

 Thanks once again to cetoole and tomb for making this delightful little project available to the DIY community.

 __Roy


----------



## srserl

royewest;4906505
 It's a great and minimalist companion to my Mini^3 amp. I'll probably figure out a way to build them together into the same chassis one day...
 __Roy[/QUOTE said:
			
		

> Just what I was thinking. I was staring at the bantam dac wondering if it would fit...I think I'll do one even if I have to get a slightly thicker or longer version of the case. I'll just have to order a couple boards when I order my mini-max pcb.
> 
> Scott


----------



## royewest

I almost ordered a "slightly thicker or longer version of the case" from Mouser but really, there wasn't an obvious choice. I'd be interested in what you pick. Or course, I'd like to add a switch so I can bypass the Bantam if needed...


----------



## srserl

1455C1202 is 4.72 inches long. I used one of these to case a Twisted Pear Opus USB receiver module which was too long for the 1455C802. I just used a carbide blade in a 10" chop saw to cut it down to the exact length I needed. I'll have to wait and see if there will be room on the back panel to wire an alternate power jack and a switch for bypassing the dac.

 Scott


----------



## TzeYang

hey guys, when using the PCM2702, do you need to put some digital attenuation (lowering the volume on your foobar) to avoid clipping like most sound card do?


----------



## jERiCOh

Quote:


  Originally Posted by *TzeYang* /img/forum/go_quote.gif 
_hey guys, when using the PCM2702, do you need to put some digital attenuation (lowering the volume on your foobar) to avoid clipping like most sound card do?_

 

I finished my first out of 4 last night and tested on Ubuntu and MacOS. I did not experience any clipping by not lowering the volume. The only clipping I got was on Windows running in my virtual machine and it was only caused by an overload of the cpu. It is amazingly well sounding for the size and the price ...


----------



## royewest

Quote:


  Originally Posted by *TzeYang* /img/forum/go_quote.gif 
_hey guys, when using the PCM2702, do you need to put some digital attenuation (lowering the volume on your foobar) to avoid clipping like most sound card do?_

 

I'm connected to a Macbook Pro using iTunes, set to max volume. I get no clipping. I gather that in the most current iTunes/MacOS systems you can use the iTunes volume control without degrading the digital signal, but I'm not inclined to mess with it if I don't have to.

 On a related topic, I'm one of those folks who find most amps impossibly loud, so I do have my Mini^3 volume set very low.


----------



## TzeYang

Hearing it is hard since dynamic peaks vary too often and they are often forgiving to the ears. 

 I've never heard of any good soundcard that does not clip when set to 0dB (highest output). I own an EMU1212M and EMU0404 myself and I understand how it's necessary to do some digital attenuation for DACs.


 The PCM2702 does not have a peak meter like the EMU does, so it's quite impossible to "measure" whether the dynamic peaks are clipping.

 Any suggestions?


----------



## error401

0dB, by definition should imply that no clipping is being introduced by that device. I don't trust the clip indicators on my e-mu 1212m. I'm pretty sure they're triggered whenever a sample hits 0dB, which doesn't mean clipping is being introduced by the card. It's either in the source material (lots of modern music) or a valid 0dB sample.

 I'm fairly sure that no digital amplification is occurring inside the chip.


----------



## tomb

I'm fairly certain that unless you run the Bantam (or Alien and other similar DAC's) at full volume, the S/N Ratio will suffer greatly.

 Someone correct me if I'm wrong, but I could swear I read somewhere that we should operate the BantamDAC {AlienDAC} with full volume set in the OS. Use your amp to adjust the volume.


----------



## Citizen86

How I understood it was that you are not running an analog signal at all, it's a digital one (obviously), so unless you are running it at full volume, like tomb mentions, then you are altering the signal and changing it from it's original form. You want the DAC to work with an unaltered signal for cleanest and most original sound.

 Isn't that why people use things like ASIO4ALL? I've read in some threads that if it is truly working then in many programs you shouldn't be able to change the volume at all via the computer...

 Don't quote me on any of this though, I don't know for certain...


----------



## TzeYang

I think my question was based on the "demands" of the digital signal being too high for the chip's output voltage swing.

 Yeah that's probably what i meant, but thanks I'll run it at 0dB and try to get a scope to test the output.


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I'm fairly certain that unless you run the Bantam (or Alien and other similar DAC's) at full volume, the S/N Ratio will suffer greatly.

 Someone correct me if I'm wrong, but I could swear I read somewhere that we should operate the BantamDAC {AlienDAC} with full volume set in the OS. Use your amp to adjust the volume.
	

	
	
		
		

		
		
	


	


_

 

Oh crap, really? I always use the volume knob on my keyboard as well as on my amp. I've actually wondered about this alot, but had never really looked into it since I'd never heard anything either way, and I can't tell a difference.

  Quote:


  Originally Posted by *Citizen86* /img/forum/go_quote.gif 
_How I understood it was that you are not running an analog signal at all, it's a digital one (obviously), so unless you are running it at full volume, like tomb mentions, then you are altering the signal and changing it from it's original form. You want the DAC to work with an unaltered signal for cleanest and most original sound.

 Isn't that why people use things like ASIO4ALL? I've read in some threads that if it is truly working then in many programs you shouldn't be able to change the volume at all via the computer...

 Don't quote me on any of this though, I don't know for certain..._

 

I use ASIO4all and I can still adjust the volume with my keyboard. To switch between my alien and my soundcard (which I use for speakers right now) I have to switch it in both ASIO4all and in the Windows Sounds and Audio Devices Properties...Am I throwing away signal quality
	

	
	
		
		

		
		
	


	




 Anyone an expert in these issues or know of any good reads on the topic?


----------



## Citizen86

Well I was reading in a thread quite a while ago that ASIO should disable volume control... but then some people are still able to. If you don't hear any audible difference, then I wouldn't worry about it too much. But I would also say, that if you are able to set your DAC to receive 100% volume while still giving your amp enough space to use the volume control, I would do that preferably.


----------



## TzeYang

You can still control the volume using foobar because the volume affects the "gain" of the digital file. 

 That's why I pondered if digital attenuation was necessary to avoid clipping.


----------



## tomb

Quote:


  Originally Posted by *TzeYang* /img/forum/go_quote.gif 
_You can still control the volume using foobar because the volume affects the "gain" of the digital file. 

 That's why I pondered if digital attenuation was necessary to avoid clipping._

 

Here again, whenever I tried the attenuation feature in foobar, it sounded very bad.


----------



## luvdunhill

has anyone experimented with other coupling caps?


----------



## cobaltmute

Quote:


  Originally Posted by *TzeYang* /img/forum/go_quote.gif 
_I think my question was based on the "demands" of the digital signal being too high for the chip's output voltage swing.

 Yeah that's probably what i meant, but thanks I'll run it at 0dB and try to get a scope to test the output._

 

Take a look at page 3 of the data sheet. Full Scale (-0db) is rated at 62% of Vcc so I would think not. As well several of the measurements later in the datasheet (like THD and S/N) are rated at -0dB.


----------



## Nemo de Monet

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_has anyone experimented with other coupling caps?_

 

Yes. 
	

	
	
		
		

		
			












 It kind of makes a mockery of the tiny size of the DAC, but 4uf, _MBGO_ caps sound very, _very_ nice. 
	

	
	
		
		

		
		
	


	




 Obviously, a larger-than-specified enclosure may be required...


----------



## tomb

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_has anyone experimented with other coupling caps?_

 

So far, I like the 1.0uf MKT Vishay-Roederstein the best for film. I've run with it for a week or two now and it seems to be pretty good - a bit better bass than the Wima MKS's, even at only 1uf. It's also very quiet (black background) with loads of detail. Some of you may run into trouble if you have a 10K input load, though, it may have a bit of bass loss with lower input impedances. (At 50K it should be plenty at fc of ~3.) It's available at Mouser:
75-MKT1817510064

 I'm going to give more details on that one shortly and will probably sell them for our international folk - they're the same size as the 3.3uf Wima's in the BOM.

 I hope to try some Elna RFS and Cerafine electrolytics this weekend.
	

	
	
		
		

		
		
	


	





 P.S. I haven't tried anything as big as the caps in that pic up there.


----------



## luvdunhill

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_So far, I like the 1.0uf MKT Vishay-Roederstein the best for film. I've run with it for a week or two now and it seems to be pretty good - a bit better bass than the Wima MKS's, even at only 1uf. It's also very quiet (black background) with loads of detail. Some of you may run into trouble if you have a 10K input load, though, it may have a bit of bass loss with lower input impedances. (At 50K it should be plenty at fc of ~3.) It's available at Mouser:
75-MKT1817510064

 I'm going to give more details on that one shortly and will probably sell them for our international folk - they're the same size as the 3.3uf Wima's in the BOM.

 I hope to try some Elna RFS and Cerafine electrolytics this weekend.
	

	
	
		
		

		
		
	


	





 P.S. I haven't tried anything as big as the caps in that pic up there.
	

	
	
		
		

		
		
	


	


_

 

I'm using 22uF/25V blue OS-CONS that were taken from a Twisted Pear Opus DAC. I prefer them to the Wima and Black Gates so far.


----------



## qusp

I'm new to amp/dac building; but have good soldering skills from modding ipods and making LOTS of LOD's and cables. I'm looking to up the specs on the signal caps (and wherever else I can afford to) by doing the regular add BG her add BG there and perhaps a couple of mundorfs. What would be the best place to start with using better caps/resistors? me and some other guys from australia are putting together a group order but I would like to know exactly how much of the default BOM list I should order and what parts I can up the anti on. sorry for my ignorance, i'm really looking forward to this. 
	

	
	
		
		

		
		
	


	




 BTW is spending that sort of $$ on this build worth it? or maybe just a couple of BG caps for signal. this dac is to be used portable


----------



## JamesL

Quote:


  Originally Posted by *qusp* /img/forum/go_quote.gif 
_I'm new to amp/dac building; but have good soldering skills from modding ipods and making LOTS of LOD's and cables. I'm looking to up the specs on the signal caps (and wherever else I can afford to) by doing the regular add BG her add BG there and perhaps a couple of mundorfs. What would be the best place to start with using better caps/resistors? me and some other guys from australia are putting together a group order but I would like to know exactly how much of the default BOM list I should order and what parts I can up the anti on. sorry for my ignorance, i'm really looking forward to this. 
	

	
	
		
		

		
		
	


	




 BTW is spending that sort of $$ on this build worth it? or maybe just a couple of BG caps for signal. this dac is to be used portable_

 

I think a good sweet point for the configuration would be pana FM's at the power rail, and wima polypropylene or polyester at the output.
 I can't tell from experience, but I don't think the blackgates would improve on the wima's. Blackgates may be ideal for positions where size and capacitance is a concern, but film caps by nature make much better coupling caps than electrolytes.
 I may go as far as putting $6 soniccaps or such at the output but IMO, the Bantam dac has two neat things going for it, including small footprint, and great price/performance. Once you start putting big expensive film caps in, you lose both of those advantages.


----------



## royewest

Beezar isn't the only source of perfect-size enclosures for the Bantam DAC!


----------



## DaMnEd

LOL! Geat idea, love it.


----------



## tomb

Quote:


  Originally Posted by *royewest* /img/forum/go_quote.gif 
_Beezar isn't the only source of perfect-size enclosures for the Bantam DAC!_

 

That's hilarious!! 
	

	
	
		
		

		
		
	


	







 Is that a Duplo block or something bigger?


----------



## royewest

The standard Duplo 2 X 6 brick turns out to have been engineered as the perfect enclosure for a Bantam DAC. 

 Clearly this is only the beginning. I'm sure there's a cmoy or comparable amp that fits in a Duplo and could be made to mate via modified studs...

 I obviously need to do this again with a cleaner opening for the USB port. I also believe that a 2x6 Duplo flat would fit onto the bottom of this, if you carve off the middle 4 studs.


----------



## joneeboi

After three attempts at a PCM2702 DAC, I have finally succeeded. I have it hooked up to my recently completed MHSS. I think the fine tip on the Hakko wand made a big difference. I'm so relieved to have a working USB DAC. I have mine set up with, you guessed it, Black Gate NX Hi-Q 47uF 6.3V. They are fresh, this DAC is fresh, this amp is fresh. The sound impressions shall come later when I get a better feel for this baby.


----------



## tomb

Way to go, joneeboi!!


----------



## pinkfloyd4ever

OMG that's f-ing awesome


----------



## royewest

Clearly the election distracted me from work today....

 FWIW, I carved a new brick and flipped the LED so it shines through one of the studs (not too apparent with my cheap camera's flash).


----------



## qusp

Quote:


  Originally Posted by *JamesL* /img/forum/go_quote.gif 
_I think a good sweet point for the configuration would be pana FM's at the power rail, and wima polypropylene or polyester at the output.
 I can't tell from experience, but I don't think the blackgates would improve on the wima's. Blackgates may be ideal for positions where size and capacitance is a concern, but film caps by nature make much better coupling caps than electrolytes.
 I may go as far as putting $6 soniccaps or such at the output but IMO, the Bantam dac has two neat things going for it, including small footprint, and great price/performance. Once you start putting big expensive film caps in, you lose both of those advantages._

 

cool i'll go for the pana's; but i've just bought some 3.3uf Vcap VIOP for a swiss army knife type output coupling dock like the regular VCAP dock but i've ordered eichmann rca's for in and out, neutrik mini in and out and ipod dock in; also putting a lithion battery or similar in there and wiring that to the dock for charging on the go. so this capped docking station will serve as the output caps on the bantam, ny DIYMOD, as well as any other output that I have anything to do with building. I achieve this by leaving the output coupling caps out alltogether and just wiring direct to the rca outs instead. all this in a hammond case. now I just need to find a sexy case for the bantam hmmmm that brick looks sweet roy; how much would you sell me one of those for?? have you got any spare??
	

	
	
		
		

		
			





 all this remains somewhat portable by using a blue 1060 Pelican case.

 how about you contact punslayer I think she'd let you into her cute-fi club lol. we need a male to reprezent


----------



## royewest

Quote:


  Originally Posted by *qusp* /img/forum/go_quote.gif 
_that brick looks sweet roy; how much would you sell me one of those for?? have you got any spare??
	

	
	
		
		

		
		
	


	


_

 

My kid says if I want any more bricks I have to go to Toys R Us and get my own.


----------



## qusp

oooooohhhhhhhhhh.... I WANNA BWICK. 
	

	
	
		
		

		
		
	


	




 nah; its awesome but I dont think it would match the rest of my kit


----------



## royewest

OK, I promise, last one....


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *royewest* /img/forum/go_quote.gif 
_OK, I promise, last one...._

 

yeeehehehessssssssss I usually don't make two useless posts in the same thread in 2 days, but that is WAY fnckin awesome


----------



## tomb

That deserves a post repeat!!





 Bob the Builder loves headphones and the BantamDAC!


----------



## qusp

classic
	

	
	
		
		

		
		
	


	




 wish I could steel that for my avatar


----------



## Nicolas2305

Heeehehehe!! Nice case!!

 I'm planning (in the future) on enclosing a bantam DAC with a Mini³ and wondered If I should put a switch as an input selector or an "OR" diode as an "automatic" input selector. Either way I'm still new in DiY and wondered about the proper way to do it. Does a plain switch would do the job? Are diodes enough?


----------



## cetoole

Nicolas, you want an input switch of the DPDT variety, though ideally, 3pdt would be better, as it would allow you to switch the ground. You really dont want to try using diodes as you propose. Simple is best here, go for a switch. The main issue I see here though is both the mini3 and bantamdac require the rear panel of the case, the mini3 for the DC input, and the bantam for the USB. There are ways around this, such as a panel mount DC jack, but then there is the issue of where to put the switch. You know there is no way this is going to fit in the 1455C801, right?


----------



## qusp

hey guys. since there is no amp section in the bantam i'm assuming that its best to run it at full volume. is there a sort of preferences/settings panel in the OS , or do you just alter the digital gain in itunes/foobar etc??. I'm assuming if you can it would degrade the SQ somewhat through digital attenuation. This question is more for somebody else in our Aussie group buy, but i'm interested too. I'll be using it with the capped dock and pico so i'm fine but my friend is using speakers/cans directly out of the mini line out. Or at least he hopes to. I wasn't certain about the details so I thought I'd pose the question here. what is the output power of the bantam??

 thanks in advance


----------



## JamesL

^
 similar question was discussed in this thread not too long ago I think.
 post 154 or so.


----------



## qusp

thanks


----------



## Gross

Can the C16 in the wrong spot damage anything? I populated the board last night, without checking out the website, so I put it in the wrong spot. I have since moved it to the right spot

 I get 3.2v and 4.72v after each regulator respectivly, and at the power pins at the 2702. My PC does not recognise it when i plug it in though. I have built 6 AlienDACs, so I know I can build these things properly.

 I did continuity checks between all the pins, and to thier pads, and I have reflowed about every connection on this board, but still no go. No chips get hot.

 I would think the regulator would not put out anything if I blew it.


----------



## tomb

Quote:


  Originally Posted by *Gross* /img/forum/go_quote.gif 
_Can the C16 in the wrong spot damage anything? I populated the board last night, without checking out the website, so I put it in the wrong spot. I have since moved it to the right spot

 I get 3.2v and 4.72v after each regulator respectivly, and at the power pins at the 2702. My PC does not recognise it when i plug it in though. I have built 6 AlienDACs, so I know I can build these things properly.

 I did continuity checks between all the pins, and to thier pads, and I have reflowed about every connection on this board, but still no go. No chips get hot.

 I would think the regulator would not put out anything if I blew it._

 

According to FallenAngel, who discovered the situation with C16:
  Quote:


 C16 must NOT be populated for TPS version, it connects NR to Vout which is not what it should be doing, NR can have a cap to Ground for noise reduction, but if it is between NR and Vout, the regulator doesn't work properly (voltages moves between 3.9V - 4.2V). You can though install C16 in R8 position for the desired result. 
	

	
	
		
		

		
		
	


	



 

Now, whether that condition can actually damage the DAC, I don't know. There are other things that can do that, though, but I can't hazard a guess from the info you've related at this time.

 If the regs are putting out what you measure - they're working and they are not the problem. I'm sure all the other parts are probably correct from what you imply, which leaves the DAC chip itself as the source of the problem.


----------



## Gross

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_which leaves the DAC chip itself as the source of the problem.
	

	
	
		
		

		
		
	


	


_

 


 That is kinda what I was thinking, but thought I would run it past everyone.

 I purchased 5 boards, so I guess here goes #2. The case is allready, with nice grommets, and some Canare on the output, I just didnt feel like populating another board today...

 Thanks anyways.


----------



## Nemo de Monet

Not that it helps much, Gross, but I'm in a similar boat - the BantamDAC I incorrectly installed the regulator cap on isn't recognized, even after replacing the cap and regulator. Like you, I've built several Alien DACs, and don't find the SMD stuff particularly difficult. I've gone over everything on that particular board twice, and have to believe that installing C16 in the "wrong" spot probably killed the DAC chip, but can't really say for sure. Just live and learn, I guess.


----------



## Gross

Thanks for the words of encouragement. However, 1 hour later, and number 2 is working. I took all the through hole stuff off of the first board, but otherwise used all new SMD parts. Now that board 1 is mostly clean, I suppose I can attempt a heart transplant, just not today. So for those just tuning in, *IF USING THE TPS REGULATORS, PUT C16 ON SPOT R8*. I don't know 100% if it causes the problem, but it sure does not help. I guess when all else fails, RTFM.


----------



## tomb

Sorry about this, guys. I have a warning and layout diagram on the Bantam DAC PCB catalog page at Beezar.com, too. So, hopefully the chances of this happening again will be reduced.

 We actually thought even up to the time of the production boards that maybe the provision for the SOT23-5 version of the REG101 was more important (they use C16 in its silkscreened position). As it quickly turned out, the TPS chips are a no-brainer. We'll get it corrected on the next round of boards.


----------



## Gross

Don't worry about it, I wasn't paying attention. That is all part of the fun anyways, isnt it?

 I am using some Canare L-4E6S and that makes it a bit tough to do the cable dac, as there isnt a lot of room with the caps in the way.. I am using the 1uf Vishay/Roederstein caps, but I think I am going to replace them with the Wimas for better bass response, as I will use this on a lot of different soundsystems, and I know a bunch of the mixers I use are only 10k inputs. The only problem with that is even less room for the wires, Not a biggie, I will just need to strip back more of the jacket to maintain flexibility. 

 Damn, I ramble.


----------



## jERiCOh

The desktop version is all built. Now, I'm working on the cable Bantam.


----------



## rhester

What size VitaQ and what are the blue caps?


----------



## jERiCOh

Quote:


  Originally Posted by *rhester* /img/forum/go_quote.gif 
_What size VitaQ and what are the blue caps?_

 

VitQ's are 0.68uF and Blue caps are 0.047uF MKP. I'm not sure if it really does something to bypass VitQ's, but at least I tried with some caps I had laying around for a while...


----------



## czegevara

I want to buy Bantam Dac board through beezar.com site, but "page cannot be found". I there any other way to buy this little board?? (I'm from Poland...)


----------



## DaMnEd

Quote:


  Originally Posted by *czegevara* /img/forum/go_quote.gif 
_I want to buy Bantam Dac board through beezar.com site, but "page cannot be found". I there any other way to buy this little board?? (I'm from Poland...)_

 

No. You should contact TomB regarding the Website issue, I'm sure it can be easily fixed.


----------



## tomb

Quote:


  Originally Posted by *czegevara* /img/forum/go_quote.gif 
_I want to buy Bantam Dac board through beezar.com site, but "page cannot be found". I there any other way to buy this little board?? (I'm from Poland...)_

 

Can you be a bit more specific? How and from what page are you trying to access it? I'm not seeing any issues and can access it just fine on my end. I'm continuing to receive orders, too:

beezar.com welcome page


----------



## czegevara

Even when Im trying to use your link - it doesn't work - Error 104 (net::ERR_CONNECTION_FAILED). The same effect when I type beezar.com welcome page into the browser window. Im using IE and Chrome on Vista. I also have full acces to any other site and there is no firewall (only windows standard firewall).


----------



## DaMnEd

Works here, but try the direct link: Beezar.com


----------



## Nemo de Monet

Try googling the error message; it seems to be a fairly common issue with Chrome, usually caused by a firewall issue. You could try using a web-based proxy, like this one, and see if that helps, if any.


----------



## czegevara

Now it works! Thanks Nemo de Monet.


----------



## Nicolas2305

Hey there, Just ordered parts for 2 Bantam DAC yesterday night. Planning on mounting one in a mini³ with a switch and the other as a cable DAC.

 I've been advised not to try this one yet because I only made 3 CMoy and 2 Mini³ up to now but I found those to be easy as pie to populate and tought I could give it a try.

 I'd wanted to have any useful input(if there are) not mentionned in the already more than complete How-to from the Bantam DAC website by TomB.

 I only fear the PCM2702 DAC soldering but will be more than careful with this little guy.


----------



## Nicolas2305

Holy S**T!!!! just received the parts from Digi-key, those are sooooo small, especially the DAC chip "legs".

 I could really use any hint you can give me before getting in populating the board (when they arrive from TomB).


----------



## royewest

You can do it. You need magnification (more if you're my age, less if you're young with the eyes I used to have). I use a dissecting scope nowadays. Even if you can see what you're doing to solder, good magnification is really helpful to review your work.

 There are also some good tutorials on line.

 Tangent has a video on SMD soldering here: Tangent Tutorials

 The Bantam instructions also offer some good advice.

 There are some other approaches with videos -- search on YouTube but take some of the more imaginative approaches with a grain of salt, or flux or whatever...


----------



## DaMnEd

Magnification is always a good idea even with 20/20 eyesight, with such small components, no need to force your eyes, that will only hurt you latter. 
	

	
	
		
		

		
			





 I have a lamp with magnification, great tool, even with something not so small, it helps!


----------



## Nicolas2305

I already went thru all tangeant video and text tutorials before starting my first CMoy, I read Bantam instructions and I just haven't tought of magnification but it was obvious.

 I think I just need to gather my courage and make sure I'm not on an overdose of sugar, cafeine or something of the kind to help to have steady hands...


----------



## tomb

Quote:


  Originally Posted by *Nicolas2305* /img/forum/go_quote.gif 
_I already went thru all tangeant video and text tutorials before starting my first CMoy, I read Bantam instructions and I just haven't tought of magnification but it was obvious.

 I think I just need to gather my courage and make sure I'm not on an overdose of sugar, cafeine or something of the kind to help to have steady hands..._

 

Good thought.
	

	
	
		
		

		
		
	


	




 I try to do the same thing - make sure you have everything organized, distractions minimized, and wait until you feel comfortable, rested, and calm. It seems to help me a lot on soldering that PCM chip.


----------



## JamesL

Remember, flux is the secret sauce.

 I remember trying to de-bridge the pcm on my alien dac without flux for bout half an hour, and it was a nightmare. 

 With flux, it took me about 1-2 minutes to get the pcm's on all three of my Bantam dacs.


----------



## Nicolas2305

I don't have any "secret sauce" because I haven't needed any up to now. Should I go get some right away or I should see if I can work it out without any flux of some kind? I do have wick with flux in it, I tought it would be enough...


----------



## error401

Get the flux first, just buy a cheap flux pen. It's indispensable with SMD, and I'd consider it a necessity, especially if you're inexperienced. Wick may be enough, but lots of flux makes life easier, and easy is good.


----------



## tomb

Quote:


  Originally Posted by *error401* /img/forum/go_quote.gif 
_Get the flux first, just buy a cheap flux pen. It's indispensable with SMD, and I'd consider it a necessity, especially if you're inexperienced. Wick may be enough, but lots of flux makes life easier, and easy is good._

 

Agree 100% - X10, even. Excellent point as usual, error401!


----------



## Hayduke

Quote:


  Originally Posted by *Nicolas2305* /img/forum/go_quote.gif 
_I already went thru all tangeant video and text tutorials before starting my first CMoy, I read Bantam instructions and I just haven't tought of magnification but it was obvious.

 I think I just need to gather my courage and make sure I'm not on an overdose of sugar, cafeine or something of the kind to help to have steady hands..._

 

I like to solder while drinking something strong 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Good thought.
	

	
	
		
		

		
		
	


	




 I try to do the same thing - make sure you have everything organized, distractions minimized, and wait until you feel comfortable, rested, and calm. It seems to help me a lot on soldering that PCM chip.
	

	
	
		
		

		
		
	


	


_

 

I'm not kidding about the above statement 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Agree 100% - X10, even. Excellent point as usual, error401!_

 

Get the little bottle of flux, a dispenser bottle (it has the skinny metal tube sticking out of the top), and the giant size bottle of alcohol to clean it all up. While I probably use a lot of flux compared to other DIYers here, I still don't really use a lot. As a result though, I also use a HUGE amount of alcohol. I'm spoiled from working in electronics manufacturing for many years, so I got a dispenser bottle for that as well (I bought this one 35704 ) You might also want a brush like this one 577-2020

 Yes I know buying tools costs more then the projects, but you can use them forever. Can you get by without them? Probably, but I built my skillset using them, so I need them 
	

	
	
		
		

		
		
	


	





 EDIT:
 I forgot to ask my questions  I came to this thread because I built a Bantam last night, but it isn't performing well.

 First off, I made it a cable DAC. I ordered the board, case, cable, and Panasonic FM cap from the website. I didn't use RCAs though, I wired on a mini phono since that's what my amps have as inputs. All parts not from Bazaar came from Mouser.

 I got it all soldered up fine. The only difficulty were the 4 test pins on the IC. Those pads aren't as well tinned or something, because I couldn't get a good joint there. After I looked at the schematic and realized those 4 pins (2 pairs on each side at the end away from the polarity mark) weren't used, I moved on. Everything went OK. As I alluded to above, I used to work in SMT assembly for many years. I mostly ran the pick & place machines, but I did plenty of hand soldering and rework. So I was comfortable with the components.

 When I hooked it up, Windows XP installed it fine. Fired up Foobar and I got it to make sound feeding a cmoy with some cheap earbuds. Once I knew it was functional, I started listening. Immediately I could tell the right channel was louder. It sounds like the balance control is shifted to the right. I'll go over all the solder joints again, but it was late last night, so I didn't do that right then. I didn't use 2 wires for the ground to the output. It looked like both of the attachment points we connected, so I didn't think it would matter. Could this have anything to do with the imbalance? I still think it has to do with a solder connection somewhere. I suspect it's the phone plug. Is was a style I had never used before. I thought I had good connections, but maybe not. I'll try reflowing the joints there first then reflow everything inside the DAC.

 When I hooked it up to my Millet Hybrid Starving Student, it had a horrible hum. I'm pretty confident I can fix the balance problem, but the hum has me concerned. Any ideas what it might be?


----------



## Nicolas2305

thanks all for your advices, I will get flux as soon as I can (might be in more than a week) and wait for the appropriate moment to build everything (have parts for 2) and will then see how to stuff one of those with my uncased Mini³


----------



## tomb

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_<snip>
 EDIT:
 I forgot to ask my questions  I came to this thread because I built a Bantam last night, but it isn't performing well.

 First off, I made it a cable DAC. I ordered the board, case, cable, and Panasonic FM cap from the website. I didn't use RCAs though, I wired on a mini phono since that's what my amps have as inputs. All parts not from Bazaar came from Mouser.

 I got it all soldered up fine. The only difficulty were the 4 test pins on the IC. Those pads aren't as well tinned or something, because I couldn't get a good joint there._

 

Actually, they're attached to the ground plane, so it takes a much hotter touch of the iron to get the solder to stick properly there. I've found if those are the last pins soldered, usually the iron and the surrounding area is hot enough to make this a bit easier. Quote:


 After I looked at the schematic and realized those 4 pins (2 pairs on each side at the end away from the polarity mark) weren't used, I moved on. Everything went OK. As I alluded to above, I used to work in SMT assembly for many years. I mostly ran the pick & place machines, but I did plenty of hand soldering and rework. So I was comfortable with the components.

 When I hooked it up, Windows XP installed it fine. Fired up Foobar and I got it to make sound feeding a cmoy with some cheap earbuds. Once I knew it was functional, I started listening. Immediately I could tell the right channel was louder. It sounds like the balance control is shifted to the right. I'll go over all the solder joints again, but it was late last night, so I didn't do that right then. I didn't use 2 wires for the ground to the output. It looked like both of the attachment points we connected, so I didn't think it would matter. Could this have anything to do with the imbalance? I still think it has to do with a solder connection somewhere. I suspect it's the phone plug. Is was a style I had never used before. I thought I had good connections, but maybe not. I'll try reflowing the joints there first then reflow everything inside the DAC.

 When I hooked it up to my Millet Hybrid Starving Student, it had a horrible hum. I'm pretty confident I can fix the balance problem, but the hum has me concerned. Any ideas what it might be? 
 

Hum most definitely can indicate a ground connection problem. Plus, a hum plus channel imbalance can easily be caused by incorrect wiring to an output plug.

 One way to confirm is if you have correct voltage at the output of the DAC. If you can measure the DC voltage to ground of OL and OR just prior to the output caps, that should tell you whether there's an imbalance/problem with the DAC chip. It's a little bit awkward, but probably safer than putting a probe to one of the DAC pins while it's power - flip the board over and see if you can carefully place one probe on the first coupling cap lead (closest to the PCM chip output) and the second probe on OG. Do this for Left and Right channels. You should be able to measure about ~2.3 to 2.4VDC for each channel. If so, then the issue is most likely with how you wired the jack/plug. If not, then there's a problem with the DAC chip.


----------



## Hayduke

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Actually, they're attached to the ground plane, so it takes a much hotter touch of the iron to get the solder to stick properly there. I've found if those are the last pins soldered, usually the iron and the surrounding area is hot enough to make this a bit easier._

 

So do they need to be soldered? I used the solder wick to take most of the solder out of that area since they were bridging pretty bad. I got nice joints on all the other pins, but I couldn't get those 4 to work well. In the schematic they don't seem to be connected to anything, so I didn't think it would matter.

  Quote:


 Hum most definitely can indicate a ground connection problem. Plus, a hum plus channel imbalance can easily be caused by incorrect wiring to an output plug.

 One way to confirm is if you have correct voltage at the output of the DAC. If you can measure the DC voltage to ground of OL and OR just prior to the output caps, that should tell you whether there's an imbalance/problem with the DAC chip. It's a little bit awkward, but probably safer than putting a probe to one of the DAC pins while it's power - flip the board over and see if you can carefully place one probe on the first coupling cap lead (closest to the PCM chip output) and the second probe on OG. Do this for Left and Right channels. You should be able to measure about ~2.3 to 2.4VDC for each channel. If so, then the issue is most likely with how you wired the jack/plug. If not, then there's a problem with the DAC chip. 
 

I'll check those values. I didn't get any time last night to troubleshoot the issues I'm having with the DAC. My meter works fine, but my brother borrowed it and somehow managed to break the pointy tips off my probes 
	

	
	
		
		

		
		
	


	




 They still work, but they are kinda "stubby" now hehe. I need to get new ones or files these back down to a point. Hopefully the points you're suggesting I test are big enough. I have trouble with measuring tiny contacts. I couldn't probe the DAC chip's legs, but I have the attachments with little wire hooks that I could grab the legs with. Enough of that little sidenote 

 I realize that hum is usually a grounding issue, so that's an area I was going to look into. The problem is the worst with my MHSS amp. It sounds great with a signal from the line out of an iPod, but it was absolutely unlistenable with this DAC 
	

	
	
		
		

		
		
	


	




 It's not a little bit of hum, it's LOUD. I'm not saying that it's the DAC for sure. It certainly could be partially the amp's problem, and I suspect it is. I just completed the amp this week also, so I may give my wiring another going over.

 Thanks for the help Tom


----------



## kuroguy

Not suggesting that this is the problem, cause I've been known to be wrong, but are the heatsinks in your MHSS greased?


----------



## jERiCOh

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_So do they need to be soldered? I used the solder wick to take most of the solder out of that area since they were bridging pretty bad. I got nice joints on all the other pins, but I couldn't get those 4 to work well. In the schematic they don't seem to be connected to anything, so I didn't think it would matter.



 I'll check those values. I didn't get any time last night to troubleshoot the issues I'm having with the DAC. My meter works fine, but my brother borrowed it and somehow managed to break the pointy tips off my probes 
	

	
	
		
		

		
		
	


	




 They still work, but they are kinda "stubby" now hehe. I need to get new ones or files these back down to a point. Hopefully the points you're suggesting I test are big enough. I have trouble with measuring tiny contacts. I couldn't probe the DAC chip's legs, but I have the attachments with little wire hooks that I could grab the legs with. Enough of that little sidenote 

 I realize that hum is usually a grounding issue, so that's an area I was going to look into. The problem is the worst with my MHSS amp. It sounds great with a signal from the line out of an iPod, but it was absolutely unlistenable with this DAC 
	

	
	
		
		

		
		
	


	




 It's not a little bit of hum, it's LOUD. I'm not saying that it's the DAC for sure. It certainly could be partially the amp's problem, and I suspect it is. I just completed the amp this week also, so I may give my wiring another going over.

 Thanks for the help Tom 
	

	
	
		
		

		
		
	


	


_

 

I had the same problem with my first Bantam. It sounded like a loud glitch and the music was quieter than it was supposed to be. I resoldered the chip and it was gone. I hope it will help.


----------



## tomb

Quote:


  Originally Posted by *kuroguy* /img/forum/go_quote.gif 
_Not suggesting that this is the problem, cause I've been known to be wrong, but are the heatsinks in your MHSS greased? 
	

	
	
		
		

		
			



_

 

Please leave it alone. We beat it to death in the Starving Student thread. It has no relevance over here.


----------



## bperboy

Just finished my CableDAC this afternoon. Problems though. I plugged it in to my Mac, and the DAC showed up, but when plugged into my speaker system, only emitted a high pitched whine. Also, the power LED didn't come on. I'm not entirely sure that the LED is oriented correctly. Could this also cause no sound to come out?


----------



## Nicolas2305

The led shouldn't cause any problems to your sound. I have checked the schematic and abolutely no led at all shouldn't cause anything.


----------



## royewest

The polarity of the LED is not clearly printed on the board (at any rate, I didn't understand how to read the label).

 I plugged the bantam into a USB port and inserted the LED to see which way would light it up; then I soldered it in place.

 You might pull the LED and try that, particularly if you have a spare....


----------



## JamesL

Look at the bottom of the board. 
 You should see a trace connecting R9 to one of the holes.
 This is the positive lead. The other side connects to ground.


----------



## bperboy

Yeah, I'm pretty sure now the LED is in correctly. Long lead should go in the pad closest to the USB jack. I'm a bit stymied as to why the DAC is recognized, but no sound is coming out.


----------



## bperboy

Voltage check on regulators:

 IC1 3.28VDC
 IC2 2.15VDC** I'm assuming this isn't correct. What can be done to fix? reflow joints? or is it a bad chip?


----------



## bperboy

I measure 4.97VDC across the leads of the LED. That might indicate a short somewhere, and the LED is likely blown, correct?


----------



## Nicolas2305

if you have a short somewhere, you might not have enough juice to power your led.

 Anyway, I don't think your first problem here is your led. you should concentrate on your output problem first.


----------



## bperboy

Reflowed the 4.75 V TPS chip. Now have sound. No LED though. Think that might just be dead, as I measured ~5VDC over the leads.

 EDIT: In backwards. All Fixed and working correctly.. melted a bit of the wima cap.. I think it's only superficial though.


----------



## tomb

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_Reflowed the 4.75 V TPS chip. Now have sound. No LED though. Think that might just be dead, as I measured ~5VDC over the leads.

 EDIT: In backwards. All Fixed and working correctly.. melted a bit of the wima cap.. I think it's only superficial though._

 

Glad to hear you got it working.
	

	
	
		
		

		
		
	


	




 One other thing - when you can, replace those Wima's with the Vishay-Roederstein MKT. I made it the first choice in the BOM back on Nov 1st. It beats anything I've tried by a mile - including Black Gates and the Wima. The Wima was OK on mine for awhile, but then as the midrange came in and some of the mid-bass fog disappeared, the deep bass and slam dropped off a cliff. The Vishay-Roederstein has fantastic bass and slam - with every bit the detail of the Wima, perhaps more. I've used it constantly for almost a month, now. It's even more of a testament that the Roederstein is only 1uf, whereas the Wima is 3.3uf. However, I can't recommend the green Roederstein enough ... simply splendid in every single way. I hope everyone who has a Bantam tries them:

https://www.mouser.com/Search/Produc...-MKT1817510064

 A ridiculous 82 cents each at Mouser.:


----------



## bperboy

That fits right on the board? The wimas I have now squeeze together.. they're just a bit too wide.


----------



## Hayduke

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_A ridiculous 82 cents each at Mouser.:
	

	
	
		
		

		
		
	


	





_

 

Ridiculous good or bad?


----------



## bperboy

What about Mouser P/N: 594-2222-370-11105? I only ask, because I've already got 4.


----------



## tomb

Of course, you're welcome to try anything ... I only mentioned it because it's the best. 
	

	
	
		
		

		
		
	


	







 Yes ... it fits on the board. Lead spacing is only 5mm.


  Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_Ridiculous good or bad? 
	

	
	
		
		

		
		
	


	


_

 

A V-cap in that rating is $270 ... you tell me.


----------



## rhester

Didn't somebody use some larger VitaQ's for ahome build. I have one in a ciogar base box with polenty of room for exotic caps. Any recommendations?

 Thanks


----------



## jERiCOh

Quote:


  Originally Posted by *rhester* /img/forum/go_quote.gif 
_Didn't somebody use some larger VitaQ's for ahome build. I have one in a ciogar base box with polenty of room for exotic caps. Any recommendations?

 Thanks_

 

I did with 0.68uF VitQs bypassed by 0.047 MKPs. It sounds warmer more defined to my ears than the 1uF Vishay MKPs. Although the Bantam sounds great I would not spend more on output caps because the DAC is limited by its chip.


----------



## Hayduke

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_A V-cap in that rating is $270 ... you tell me.
	

	
	
		
		

		
			



_

 

That's what I thought 
	

	
	
		
		

		
		
	


	




 I'm hoping to solve the problems with mine tonight. I ended up at work today 
	

	
	
		
		

		
		
	


	




 We had a drive failure, so now I'm watching the array rebuild.


----------



## tomb

Well, I'll disagree a little bit with jERiCHOh. I think my BantamDAC with the Vishay-Roedersteins sounds better than my 0.66uf (three 0.22uf in parallel) Alien DAC. The VitQ's are just a trifle light on bass, while the Roedersteins are just d*mn fast, meaning highly detailed compared to the VitQ's. Yes, the VitQ's sound more refined in the mids and have outstanding musicality, but paired with my MiniMAX, the Roederstein BantamDAC sounds like a better combination.


----------



## jERiCOh

I totally agree with you tomb ! But bypassing them with MKPs seemed to give the output more fastness. Well... to my ears. I must say I'm more into trying to correct the sound from my "downloaded" music than full bass response.


----------



## rhester

Jericho, where did you find the VitaQ's at?


----------



## jERiCOh

Ebay... The seller I bought it from has no more big ones but I found those ones for you.


----------



## royewest

Quote:


  Originally Posted by *rhester* /img/forum/go_quote.gif 
_Jericho, where did you find the VitaQ's at?_

 

beezar.com, which tomb runs, sells them in two values, at a couple few dollars each -- a generous service to us DIYers. You can configure them in parrallel to get higher values.


----------



## qusp

sorry guys i'm a total SMD noob other than ipod mods. the bantam kit arrived today. i'm assuming the resistors are non polar there are a couple with numbers on that would have some way of orienting them if that was the case, but most have no distinguishing marks whatsoever and look the same one way as the other


----------



## JamesL

Only the IC's, the two electrolytes, LED, and usb connector are polar.


----------



## tomb

Quote:


  Originally Posted by *JamesL* /img/forum/go_quote.gif 
_Only the IC's, the two electrolytes, LED, and usb connector are polar._

 

Exactly right.

 BTW, in the layout pic below - *"+" is at left for the LED*.


----------



## bperboy

TomB, is the long lead +? I swear that's how I put mine in a few days ago, but it was definitely backwards.

 EDIT: Is leaving the DAC plugged in, but not to a source, beneficial for burning-in? I don't have my amps home on break with me, but I've still left my BantamDAC plugged in anyways..


----------



## tomb

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_TomB, is the long lead +? I swear that's how I put mine in a few days ago, but it was definitely backwards._

 

Long lead is "+", positive. Quote:


 
 EDIT: Is leaving the DAC plugged in, but not to a source, beneficial for burning-in? I don't have my amps home on break with me, but I've still left my BantamDAC plugged in anyways.. 
 

No, but it won't hurt it. I typically have mine connected to a USB port on the computer all the time. However, no current flows through the output caps unless it's connected to something and playing music.


----------



## qusp

Quote:


  Originally Posted by *JamesL* /img/forum/go_quote.gif 
_Only the IC's, the two electrolytes, LED, and usb connector are polar._

 

cool thats what I thought
	

	
	
		
		

		
		
	


	




 thanks lol @ the usb connector hehe, but i've heard they sound better when you reverse the polarity


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## qusp

again sorry for the noob question. when reading the schematic am I to assume that + will always be on the left when oriented the same way as the lettering indicates ie. with the output caps and everything that IS polar. so when oriented on the same way as the text for C7 or whatever the positive lead will be on the left as a rule??

 ok i'm going to sleep its 4am and i've got a big bantam day tomorrow 
	

	
	
		
		

		
		
	


	




 will check back in the morning befoer I have my jug'o'coffee and get going on it.

 also is there any booze that I can substitute for pure alcohol for cleaning the PCB after i'm finished?? ie vodka 
	

	
	
		
		

		
		
	


	




 one for me one for the bantam


----------



## tomb

Quote:


  Originally Posted by *qusp* /img/forum/go_quote.gif 
_again sorry for the noob question. when reading the schematic am I to assume that + will always be on the left when oriented the same way as the lettering indicates ie. with the output caps and everything that IS polar. so when oriented on the same way as the text for C7 or whatever the positive lead will be on the left as a rule??_

 

NO. All I said was,  Quote:


 "BTW, in the layout pic below - "+" is at left for the LED." 
 

That didn't say anything about any other part on the board. There have been some posts about the missing "+" sign in the silkscreen for the LED, so I clarified that omission, *nothing more*.

  Quote:


 ok i'm going to sleep its 4am and i've got a big bantam day tomorrow 
	

	
	
		
		

		
			





 will check back in the morning befoer I have my jug'o'coffee and get going on it.

 also is there any booze that I can substitute for pure alcohol for cleaning the PCB after i'm finished?? ie vodka 
	

	
	
		
		

		
		
	


	




 one for me one for the bantam 
 

Remember that C16 goes on the R8 pads while you're drinking that vodka.


----------



## Hayduke

Quote:


  Originally Posted by *qusp* /img/forum/go_quote.gif 
_also is there any booze that I can substitute for pure alcohol for cleaning the PCB after i'm finished?? ie vodka 
	

	
	
		
		

		
		
	


	




 one for me one for the bantam_

 

Why would you want to share?

 My booze is for ME! Let the PCB get it's own damn booze. If it's getting drunk, it better not start sluring the lyrics in my music 
	

	
	
		
		

		
		
	


	




 just in case you aren't entirely kidding...
 You use a different kind of alcohol to clean the flux off


----------



## qusp

yeah isopropyl right??

  Quote:


 My booze is for ME! Let the PCB get it's own damn booze. If it's getting drunk, it better not start sluring the lyrics in my music 
 

LOL and stop playing those dodgy old love balads


----------



## JamesL

isopropyl's the easiest to get.
 liquor would work to get the flux off, but it'll also leave other kind of crap on your board.


----------



## qusp

Quote:


  Originally Posted by *JamesL* /img/forum/go_quote.gif 
_isopropyl's the easiest to get.
 liquor would work to get the flux off, but it'll also leave other kind of crap on your board._

 

yeah; I figured as much, I was actually joking, but also interested to see if it could be used in a pinch. bourbon and coke would be bad!! sticky and would smell like a bad night out after a day or two


----------



## bperboy

Tomb, current's still going to be flowing thru the caps if I play music but don't hook up another amp further down the chain, correct? Like, I can plug in the DAC, set my iTunes to play, but not hook it into anything, and burn-in will occur? I just didn't bring any of my amps home on break, and I wanted a head-start for when I get back.


----------



## JamesL

current won't flow without a circuit.
 Theres no circuit if nothing's plugged into a dac.


----------



## cetoole

Quote:


  Originally Posted by *qusp* /img/forum/go_quote.gif 
_yeah; I figured as much, I was actually joking, but also interested to see if it could be used in a pinch. bourbon and coke would be bad!! sticky and would smell like a bad night out after a day or two
	

	
	
		
		

		
		
	


	


_

 

In a pinch, yeah, booze can work. I have used rum to clean a friend's CPU and heatsink before, as we didnt have anything else available. Less ideal when cleaning a PCB, because there is other stuff in the mix that wont evaporate and can cause shorts, or simply increased capacitance in bad areas. Everclear would be just fine though. Acetone works GREAT (but not for drinking).

http://img.photobucket.com/albums/v3...e/heatsink.jpg

 Bperboy, I wouldnt worry about trying to force burn in. Just wait until you get back, then listen to some good tunes. Besides, this is a perfect excuse to build another amp!


----------



## bperboy

Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_
 Bperboy, I wouldnt worry about trying to force burn in. Just wait until you get back, then listen to some good tunes. Besides, this is a perfect excuse to build another amp!_

 

Hah, i've already got two Minimaxes in a cardboard box... haven't tried tunes thru them yet, but I'm bringing home some prewired RCAs to hook up... should be quite excellent! Plus I'll have another Bantam to build! (need a source to give my dad for xmas to go along with the starving student I built him!)


----------



## qusp

ahhhh!!!! step 1 and i'm screwed I think. I had the dac pretty much done with point to point. and then I remembered the post on the beezar bantam thread that recommended using the tinned solder wick with some flux in it too to run the tip down the pins and clean it up and make sure everything is soldered at the same time. well I heated the iron up nice and hot prepared the braid and started my way down. of course while you are doing this you cant see whats happening underneath. and when I had finished my way down I noticed that all the ****in traces were crooked 
	

	
	
		
		

		
		
	


	




 so the het and force needed to get a good bit of squeeking action happening obviously unglued the trace from the pcb.. so looks like i'm oredring another PCB and a dac to make sure. just in case I cant get the dac off without damaging it. I spent a while trying to fix it and its hard to tell whether the bits that snapped off while the pins were still soldered down were just the bits protruding past the joint or whether the whole trace somehow pulled out from underneath also I cant be sure without removing the dac whether some of the traces have become so misaligned that they are now shorting against the one next to it. I had no idea the trace was held in place so tenuously or I would never have even attempted that method especially as you cant really see whats going on. and the 3 pins just above the 2 bottom left unused ones. the 3 that dont seem to be connected to any trace on the board: what are they?? the ones opposite audio ground they are the main problem because they actually broke off (not the pins the trace) when I tried to push them back. alhough i'm pretty sure those pins are still connected . its night time here and I dont think I can get enough light to get you a decent pic. i'll do in the morning. with a macro lense and flash I could get it but because I would heve to get so close the lense would cast a shadow over the dac.

 anyway that really pisses me off. had it all fairly well lined up with only a couple of suspect areas where I thought I may have had to realign the pins by pushing them that way and down at the same time with the iron. but nothing drastic. and i'm unwilling to just push ahead and risk doing it all only to find out the one of the traces is gone and then have to desolder everything again. oh well i'll post in the morning and see what you think. but i'm afraid I wont be able to show the extent of the movement of the trace on camera


----------



## vattern

An easy way of desoldering the dac is as follows :

 Turn the board upside down, and heat the back of the board with a heatgun . Once the solder starts melting, give it a sharp tap, the dac tends to fall of , assisted by gravity.


----------



## qusp

well I got it off. here was a pic before and now I look at it it really would've been fine with just a dry tip on a couple of the pins certainly didn't need the wick so much oh well the joy after afterthought






 this is the pcb now notice the three that I mentioned earlier that I couldn't see any trace for the pads to actually go to whats the go with them?? please dont tell me they aren't needed because they were the only problem before I did that wonderful heatgun trick thankyou for that BTW (now that I can see what was going on under there there wasn't any shorts after all doh). but one pin didn't come off properly and the trace came with it. other than that there wasn't any shors like a thought. 


 so anyway below is a couple of ideas that I have:






 provided those three pads I have circled in white on the left aren't connected to anything, like it seems. if they are vital then i'm screwed BUT...

 can I solder the pin related to the missing trace to the bit of trace on the right next to C5 (the left output pin it seems) I have exposed with my scalpel on the right?? or could I use some cardas tonearm wire to connect directly to the left output cap after bending the pin up ever so gently and soldering direct to it?? the one underneath that is actually still there and intact its just bent, so I could solder to that or to the pad on C5?? correct??.

 or should I just order another PCB and wait the extra week. and pay the extra shipping. the dac came off perfectly so it'll be fine


----------



## tomb

There are several pins on the DAC that aren't used. You should study the schematic - it has all of your answers. Pins 10, 11, and 12 are not connected to anything. Pins 9, 13, 14, 15, and 16 are only tied to ground.

 I hate to say this, but the board doesn't look too good in that pic. Yes, the traces are thin and fragile, but this is no different than any other DAC board, per se. It would be a shame to go through all the trouble again and not have it work because a pin on the DAC is bad or a trace on the board is torn up.

 Just an FYI, but I don't really recommend cleaning up the traces in a wholesale manner with a wick unless needed - for the very reasons you discovered. At the same time, I try to stay away from these conversations too much because everyone has their own preference for soldering. If it works, who am I or anyone else to say it's not proper?

 That said, the ideal way to "finish" off the pin joints is to wipe in a downward and sideways motion with a _hot_, _dry_ iron, only. As a matter of fact, that's how I solder a DAC chip, period - the only difference being that I add tiny bits of solder to the iron tip while I'm doing this. When all the pins are shiny, then I quit.
	

	
	
		
		

		
		
	


	




 The sideways finishing technique is described on the Bantam website and also illustrated in an excellent manner in Tangent's tutorial on soldering SMD components:
Surface Mount Soldering Techniques

 EDIT PS: Just an FYI, but if the iron is _dry_, it will pick up as much stray solder/bridges as a wick, anyway - just keep wiping the DAC pins and drying the iron tip. A brass wool soldering iron cleaner as opposed to a cold, wet sponge will really benefit this technique.


----------



## qusp

yeah I read the schematic and it seemed to say that 12 was zero (which was cool) 11 was suspend (which could be cool) and 10 was playback (which isnt cool at all or at least doesn't sound cool) but then I see that 10 doesn't seem to match with the schematic because in the schematic 10 would connect to something and the fifth from the bottom in reality doesn't seem to connect to anything on either side of the board. am I reading it wrong??? and a brass sponge is the only thing like that I didn't pick up. only got the wet sponge.I saw tangents tutorial and was going to do all that I know I should have because as you can see in the first pic I wasnt far off track. then I read that post and went with a technique I hadnt tried before stupidly and look where it got me.

 edit: you better not tell me that PLAYBACKVOUTR is the full name for VOUTR on pin 19 but it starts next to 10 so it looks like 10 is PLYBCK and 19 is VOUTR and youve included it (PLYBCK) in the schematic because there was room for it with that pin because the left pin is unused and you have only called it VOUTL on 23 because there isn't room. If so then i'm a little confused as to why you would put something so inconsistent in a schematic.That was the main reason I pulled the dac off to see what was going on underneath it, to see whether 10 was connected when it didn';t need to be connected.. sure if you were experienced in reading this stuff maybe you would just go with your gut and what you know. but in my case this is the first SMD or really anything like this so I didn't know to disregard it.

 I know this is a work in progress and you guys are doing a wonderful job for us noobs. But might I suggest that you use a smaller type so it is clear that it is all one name rather than looking like 2 that are joined together. and please keep naming consistent or have some other mark to suggest that this pin is unused. i'm going to see if I can do it anyway. because it seems that I still have all the required pads available except for Lout on 19 and I can jerry rig that I think. (you didn't answer that) will that cause any sort of phase in-discrepancy if one is a slightly long??r wire or a different type of wire. perhaps I'll do it with Rout 23 as well


----------



## Hayduke

Quote:


  Originally Posted by *qusp* /img/forum/go_quote.gif 
_yeah I read the schematic and it seemed to say that 12 was zero (which was cool) 11 was suspend (which could be cool) and 10 was playback (which isnt cool at all or at least doesn't sound cool) but then I see that 10 doesn't seem to match with the schematic because in the schematic 10 would connect to something and the fifth from the bottom in reality doesn't seem to connect to anything on either side of the board. am I reading it wrong??? and a brass sponge is the only thing like that I didn't pick up. only got the wet sponge.I saw tangents tutorial and was going to do all that I know I should have because as you can see in the first pic I wasnt far off track. then I read that post and went with a technique I hadnt tried before stupidly and look where it got me.

 edit: you better not tell me that PLAYBACKVOUTR is the full name for VOUTR on pin 19 but it starts next to 10 so it looks like 10 is PLYBCK and 19 is VOUTR and youve included it (PLYBCK) in the schematic because there was room for it with that pin because the left pin is unused and you have only called it VOUTL on 23 because there isn't room. If so then i'm a little confused as to why you would put something so inconsistent in a schematic.That was the main reason I pulled the dac off to see what was going on underneath it, to see whether 10 was connected when it didn';t need to be connected.. sure if you were experienced in reading this stuff maybe you would just go with your gut and what you know. but in my case this is the first SMD or really anything like this so I didn't know to disregard it.

 I know this is a work in progress and you guys are doing a wonderful job for us noobs. But might I suggest that you use a smaller type so it is clear that it is all one name rather than looking like 2 that are joined together. and please keep naming consistent or have some other mark to suggest that this pin is unused. i'm going to see if I can do it anyway. because it seems that I still have all the required pads available except for Lout on 19 and I can jerry rig that I think. (you didn't answer that) will that cause any sort of phase in-discrepancy if one is a slightly long??r wire or a different type of wire. perhaps I'll do it with Rout 23 as well_

 

The schematic looks clear to me. The pins are labeled above the pin. The text inside the DAC is lined up with each pin.

 I had problems soldering the 4 test pins at the "bottom" of the DAC. When I went to see what they did, I used the schematic AND the layout pictures. If you look at the layouts provided on the site, it seems pretty obvious to me which pins are not used.

 It's a bummer you're having all this trouble, but there is a silver lining. The difference between an expert and a beginner is the expert has already made the 1000s of mistakes the beginner has yet to experience 
	

	
	
		
		

		
		
	


	




 I'm sure your SMD soldering skills have improved as a result of this project, and, in the long run, it didn't cost you a lot of money.


----------



## tomb

Quote:


  Originally Posted by *qusp* /img/forum/go_quote.gif 
_yeah I read the schematic and it seemed to say that 12 was zero (which was cool) 11 was suspend (which could be cool) and 10 was playback (which isnt cool at all or at least doesn't sound cool) but then I see that 10 doesn't seem to match with the schematic because in the schematic 10 would connect to something and the fifth from the bottom in reality doesn't seem to connect to anything on either side of the board. am I reading it wrong??? and a brass sponge is the only thing like that I didn't pick up. only got the wet sponge.I saw tangents tutorial and was going to do all that I know I should have because as you can see in the first pic I wasnt far off track. then I read that post and went with a technique I hadnt tried before stupidly and look where it got me.

 edit: you better not tell me that PLAYBACKVOUTR is the full name for VOUTR on pin 19 but it starts next to 10 so it looks like 10 is PLYBCK and 19 is VOUTR and youve included it (PLYBCK) in the schematic because there was room for it with that pin because the left pin is unused and you have only called it VOUTL on 23 because there isn't room. If so then i'm a little confused as to why you would put something so inconsistent in a schematic.That was the main reason I pulled the dac off to see what was going on underneath it, to see whether 10 was connected when it didn';t need to be connected.. sure if you were experienced in reading this stuff maybe you would just go with your gut and what you know. but in my case this is the first SMD or really anything like this so I didn't know to disregard it._

 

You're over-analyzing this. The first place to look when you have a question like this is the data sheet for the part. This can be found on the BantamDAC website under "Technical Highlights"

 Here's a diagram of the pinouts from Texas Instruments in that data sheet:






 As you can see, we're only interested in VOUTL and VOUTR for output - those are the signal outputs. "PLYBCK" has to do with _software control_, which is not used in the BantamDAC.

 All that said, it's not fruitful to analyze each individual pin, IMHO. Read the soldering techiniques that we've listed - Tangent's, on the Alien DAC website, and the BantamDAC website. The DAC chip is sort of an all or nothing proposition in my experience. It's not something that you can really trouble-shoot with much success. True, you need to get bridges cleared (except for those tied to the ground plane on the bottom), and try to make certain there's contact, but that's about it. Quote:


 
 I know this is a work in progress and you guys are doing a wonderful job for us noobs. But might I suggest that you use a smaller type so it is clear that it is all one name rather than looking like 2 that are joined together. and please keep naming consistent or have some other mark to suggest that this pin is unused. i'm going to see if I can do it anyway. because it seems that I still have all the required pads available except for Lout on 19 and I can jerry rig that I think. (you didn't answer that) will that cause any sort of phase in-discrepancy if one is a slightly long??r wire or a different type of wire. perhaps I'll do it with Rout 23 as well 
 

Suffice to say that's the programmed output schematic directly from Eagle, the software platform of choice around here for doing board design/layout. It's not as pretty as some other forms of schematic editors, but it does a great job in the context of documenting the board layout.

 IMHO, you should probably not worry about individual pins. If you're determined to try it again with what you've got - and there's nothing wrong with that - clean everything as best you can and start fresh.

 Good luck.


----------



## qusp

well I'm pretty sure I have it sorted out; will post pics soon. after I give it a bit of a clean. I was able to get the VOUTL sorted by scraping the coating back over the trace and basically drawing a little stream of solder out to join it, so no wires will be needed by the looks of it at this stage. everything else that was needed was still intact enough for me to straighten it out enough to get contact. I just moved the whole thing over to the right a touch so as to have fresh contact on both sides. and went back to what I know. which is basically the same technique that I use to conect the pins on LODs when i'm trouble shooting one wire out of the lot or a pin has broke and cant be bother desoldering and starting again. and thats to kind of stretch the solder from one point to another and glue it in shape; except without the glue ;p you know what I mean anyway.. I actually think i've got better contact this time than the first time;l its certainly aligned more accurately;P what was that silver lining hayduke. unfortunately my workshop is downstairs so I hesitated to come up here to print more things out after already running the toner really low with other stuff for another project yesterday. anyway at this stage it looks as if all is well. so the only thing I had on me that had any labeling other than part numbers was that schematic. anyway i'll do some more tonight and finish tomorrow.

 thanks guys

 didn't mean to be accusatory that wasn't my intention. but I still think itwould be easily greyed out or something. being a graphic designer by trade the idea of one peice of information being self contained when it can be is appealing.

 anyway speak soon


----------



## tomb

FYI, I added a gallery section on the BantamDAC website (some other stuff, too). Keep the pics coming!


----------



## qusp

here's the pic after I fixed it up. i'n nearly finished the whole thing minus case work now except for one cap for C17 the terminal on it got stuck in the little hole when trying to move it into a better position. how the hell do i get one resister??

 and let me know if you think the dac looks ok. looks ok to me and AFAIK all pins are connected and not shorting


----------



## bperboy

Looks to me like a few pads have been ripped off... hard to tell from the pic though.


----------



## qusp

here's the pic after I fixed it up. i'n nearly finished the whole thing minus case work now except for one cap for C17 the terminal on it got stuck in the little hole when trying to move it into a better position. how the hell do i get one resister??

 and let me know if you think the dac looks ok. looks ok to me and AFAIK all pins are connected and not shorting[/QUOTE]

 that qwas the wrong pic I put up before. here in the real one although i've progressed well beyond that now with mine. the pads were all fuctional except for the 3 missing ones and 19 but as you can see i'v egot around thet, at the top left pin that looks a little strange needed a good switf blow and it was gone 
	

	
	
		
		

		
		
	


	




 tell m what you think


----------



## tomb

To tell the truth, that looks pretty amazing. It also looks like there are several bridges, but I'll take your word for it that you have no shorts. So, it must be flux or too many reflections.

 Good luck on hooking it up. Make sure you have those output caps soldered in and you let it stay connected to the USB jack for a minute or two before you try to connect it to an amp. That way, you'll be assured that the coupling caps are charged and are protecting the DAC chip.


----------



## qusp

any ideas on how I get another cap for C17 any of you guys have a spare one. Ceramic 0.1uf 25V X7R 10% that you could pop in an envelope to australia?? or will any brand with a matching value do?? because there's no way that will reach the minimum order anywhere OS.

 was really happy with the resurrection I managed to pul off. (*well we'll see if it works before I claim full success) I actually think the connections are in better shape this time around than the first pre holocaust build. I havent actually got the DMM out to check all the shorts but have used another better lit pic in higher res and there doesn't seem to be any bridges. there are a couple of slightly suspect areas that should easily be sorted out with a dry tip. I'm a little hesitant to use the meter on a number of pins like that especially with your warning and how i'm pushing the envelope as it is. there is more solder than I would normally use, but with the lack of solder left on the pads and the bride of frankenstine job needed; I thought it better to have a little more for strength. there is quite a bit of flux in that pic and a couple of false reflections mainly flux, because I used a liberal amount of cardas flux rosin (not the pen recommended) to try and rescue this thing. the pen is good but I like the rosin better.. still looks fine in high rez, but i'll wait till ive given it the final scrubbing before I go over the pins again with the dry iron

 BTW which pins did you think looked suspect? i'll give them another look. I realize the top left corner looks sus, but that was actually a loose piece of solder debris that was easily removed with a good blow, pins 3 and 4 were a bit close so I have since given it a going over with the dreaded wick just a dab this time and then the dry iron. but if you see any other areas of interest could you please let me know. I think i'm fine and I guess I should really bite the bullet and use the meter, but I just dont want to push my luck


----------



## JamesL

Put together a in-line dac the other day.







 



 I chose a smaller enclosure than the one sold at beezar, but I had to make some modications to the board and enclosure. 
 The hole kept the usb cable pretty tight, so I only put strain relief on the rca-ends. 
 I also have two more lying around somewhere too, but I can't seem to find one of'em.

 The soldering job for three of these went by much faster than my previous/first smd job and also turned out a lot cleaner, which I'm pretty happy about =)


----------



## JamesL

good job on the rework qusp!
 It must've been a pain desoldering the chip.

 A good way to test for connections and/or shorts is to follow the traces, and measure the nearest pad/via instead.


----------



## qusp

actually desoldering wasnt too hard, I used the method of waving the heatgun at the reverse side until the solder melted and then giving it a good rap. worked well except there was 2 pads that weren't quite melted properly, thats the reason for some of the damage. great metheod though, if you haven't got anything else on the board. but next time (fingers crossed there isnt a next time) I'll use more heat. anyway all ius well except for a missing cap. so I cant boot it up until I get one of them. i'll finish the case work and have it ready though.


----------



## qusp

hi guys well i've almost finished the bantam. the board is all done bar the outputs and led. no casework is done. the thing is while realigning C17 to make the layout look better the endcap came off it totally destroying it and I dont have any spares. BUT I pushed ahead and after dedusing rightly or not that C17 had very little to do with the operation of the dac but instead was part of the regulator for the led (which I haven't installed because I havent done the casework yet. anyway I decided to do something brazen on this info and plug it into the usb on my mac and I got this






 i'm able to select it in the controle panel for audio, it comes up nicely in the system profiler as Burr Brown PCM2702 so my question is since it seems to be working fine, in fact its still mounted right now wih no issues. can I finish the case work and install the oitputs and use it until I can find somewhere to get a .50c part shipped to me maybe with something else. or is C17 vital to the whole operation of the dac and the problem will arrise when I try and get some output. fromn the schematic it seems to really only govern power to the led so it doesnt just chew all the power on usb. am I correct in this or am I totally showing my noobness and should disconnect it straight away and not power it up again till I can find somewhere to get the cap from.

 cheers

 thanks in advance


----------



## elliot42

Oh wow, congratulations Jeremy. I have more hope for mine now seeing as how much heat your dac must have been seeing during soldering / desoldering 
	

	
	
		
		

		
		
	


	




 Lookin' good.


----------



## tomb

Once again, gusp - the Bantam schematic is your friend.
	

	
	
		
		

		
		
	


	




 Yes, it may appear that C17 has something to do with the LED, but no - C17 is a decoupling capacitor on the input to the 4.75V regulator, just as C14 is the decoupling capacitor on the input to the 3.3V regulator. I'd say at this point, try it without it - but get one when you can and install it. The 4.75V provides the voltage for the signal output. Without the decoupling cap on the input, the regulator may not be as stable as it should and so the sound of the DAC may not be as good as it should.

 That's great news that you have good results so far!


----------



## qusp

once again; I read the scematic I just dont know what it means 
	

	
	
		
		

		
		
	


	




 to me it looked like the cap regulated voltage to the led. anyway i'm assuming that I need to solder a short peice of wire accross the gap where the cap was to complete the circuit. just for the meantime. otherwise bty the sound of it there might not be any power for output. or will it still get power, just not accurately metered power??


----------



## kuroguy

Quote:


  Originally Posted by *qusp* /img/forum/go_quote.gif 
_once again; I read the scematic I just dont know what it means 
	

	
	
		
		

		
			





 to me it looked like the cap regulated voltage to the led. anyway i'm assuming that I need to solder a short peice of wire accross the gap where the cap was to complete the circuit. just for the meantime. otherwise bty the sound of it there might not be any power for output. or will it still get power, just not accurately metered power??_

 

I predict a meltdown of epic proportion. I've not looked at the schematic recently, but a decoupling capacitor typically sits between V+ and greound. soldering a wire in place of it would amount to a short to ground. I suggest you step away from the soldering iron and reread the schematic.


----------



## qusp

Quote:


  Originally Posted by *kuroguy* /img/forum/go_quote.gif 
_I predict a meltdown of epic proportion. I've not looked at the schematic recently, but a decoupling capacitor typically sits between V+ and greound. soldering a wire in place of it would amount to a short to ground. I suggest you step away from the soldering iron and reread the schematic._

 

ok then I wont do it. I would never do a solder bridge unless recommended; thus the question. the only work i've been doing with capacitors involves them being in the signal path and so nowhere near ground. I completed this build (almost) without having much of a clue how to read a schematic; and I have stated this over and over; yet people keep on telling me to go back and read the schematic. so am I to understand that a capacitor to ground allows a specific value current through by governing flow to ground rather than a resistor to ground would govern the rate of flow/amperage


----------



## JamesL

A capacitor to ground is like filling up a big tank with the faucet filling it up at one side, and a hose on the other side feeding a steady stream of water


 It acts as a power reservoir, and will pass on all the AC signal to ground(aka.. filter out any AC ripple). 
 Similarly, a coupling cap passes all the AC signals to the proceeding stage(typically the amp or headphone), and blocks the DC voltages.


----------



## kuroguy

a capacitor looks like an open circuit to DC and a short to AC.

 No offense, but if you just want to stuff circuit boards (and there is nothing wrong with that), I suggest you stick to the instructions and do not deviate one iota. If however, you want to learn a bit about electronics, I suggest a book on basic electronics. 

 You may enjoy just stuffing boards, but I suspect that you will get bored in short time and decide you want to experiment or build something thaqt hasn't been designed into a kit. Good luck whatever you decide.


----------



## Hayduke

Qusp,

 Tom already explained a little about what C17 is doing, but maybe I can make it easier to understand. I think I'm somewhere in between you two in electronics knowledge. IC2 (and IC1) are voltage regulators. They are basically "feeding" the DAC chip the voltages it wants. Since it wants 2 different voltages, there are 2 of them, each providing a different voltage. They chose to put the LED there just because it was an easy place that provides a current whenever the device is "on". The LED, and its resistor, are unrelated to C17.

 I'll reuse the sink full of water analogy to try and explain what C17 is doing. Lets imagine you have something that needs a precise and constant flow of water. Sure I could just turn on the faucet and connect the hose, but what happens when someone flushes the toilet or turns on another faucet? Ever been in the shower when someone uses water elsewhere in the house and the temperature changes? The capacitor is like the filled sink of water. Instead of connecting the hose directly to the faucet, we connect it to the drain of the sink. If there is a temporary decrease in water flow (or electrical current) from the faucet, the hose won't really notice because it will just drain a little more of the sink. As long as the demand on the hose doesn't outpace the supply from the faucet for too long (and completely drain the sink), everything is fine. Basically, we decide the size of the capacitor (the sink) based on how long we think the demand might exceed the supply. Hopefully that makes sense. I realize there is more to it then that, but it's a good way to start thinking about it 
	

	
	
		
		

		
		
	


	




 Like Tom said, the DAC may work without the cap, but it may not be stable. Unfortunately I don't know enough to be certain whether or not you will damage anything by running it without the cap. Tom doesn't seem to think so, so I would probably try it


----------



## qusp

thanks you guys 
	

	
	
		
		

		
		
	


	




,

 that clears things up nicely. you see the thing is, I do understand what a capacitor is and how it works as an entity and through using them in other projects in the audio signal path I have a basic knowledge of how they affect the the signal and their benefits and disadvantages. I also gathered that they would do something similar in the realm of power supply; but I guess I still haven't got my head around signal flow and its relation to ground properly yet. I know that all signals ultimately flow towards ground, but the idea that adding an element in the path to ground to effect something further along the line i'm still a little hazy on how that works. I know that IS how it works but I dont automatically think that way; to me its a little bit of a paradigm shift; but i'm getting there.

 in regards to just stuffing boards; nah thats not going to be me; I cant do something without trying to make it my own in some way, so yeah i've got some study to do. thats what this project was all about. I dont need a portable dac; I dont even have a laptop and the DAC in my RME Fireface pro audio interface would crap on the bantam. It was more about getting my head around how this whole little world of electrons really works; not on a quantum level of course 
	

	
	
		
		

		
		
	


	




, thats very interesting, but is too much of a head**** for me to ,launch into any type of study of it. no it was about learning how the things that connect to the cables I build work. I'm considering taking on a short course part time , only think i'm concerned about is I dont have much in the way of calculous and maths B. I always did well at maths, but its been so long and I have been more of a creative type with technical leanings for ages. digital imaging and chefing has been my thing, so somewhere bang in the middle of left and right hemispheres

 do you guys know of any really good subscription websites for electronics courses?? or CDROM courses?? i'll probably go along to the local tech, but would be good to have some more prior knowledge.

 sorry for the OT


----------



## Hayduke

Quote:


  Originally Posted by *qusp* /img/forum/go_quote.gif 
_do you guys know of any really good subscription websites for electronics courses?? or CDROM courses?? i'll probably go along to the local tech, but would be good to have some more prior knowledge.

 sorry for the OT_

 

Ya we should be talking about the Bantam DAC, but real quick I'll point you to a resource that might help.
http://www.head-fi.org/forums/f6/abs...ng-diy-384627/
 Don't take the thread title as any sort of insult 
	

	
	
		
		

		
		
	


	



 It just has a lot of links to the same online resources that would have posted here, and it mentions several good books.

 My Bantam DAC project still isn't going to well. I had sound, although with a loud hum. I reflowed a bunch of the joints, and seemed to help some. At that point I had the board connected to the cables, but sort of dangling outside the case. My USB cable and output cable are routed through a hole. In hindsight, making more of a slot near the case's seam would have been better, but too late now. 
	

	
	
		
		

		
		
	


	




 I tested like that and everything was OK. I put it _back_ into the case (the one form bazaar) and now I have no sound. 
	

	
	
		
		

		
		
	


	




 Actually I still have the hum, I have no music, although Foobar thinks it's playing music.

 I'm a little discouraged with this project now. It seemed like it would be perfect for what I wanted, a good sounding inexpensive USB DAC. I was researching other DIY DACs yesterday, but this one still seems to be ideal for my needs. I have no used for any inputs other then USB. I've ripped all my CDs into FLACs, and the convenience of having easy access to my entire collection trumps any disadvantages. So my sources are a PC or an iPod. I'm pretty happy with the line out signal of the iPods, but they can't hold the entire music collection.

 I had planned to build 2 of these anyway (one for work and one for home), so I supposed I could just order the parts for another, but I'm frustrated that I can't get this one working.


----------



## tomb

Sounds like the wiring is the issue. It's a fairly common problem and not limited to DACs.
	

	
	
		
		

		
		
	


	




 Check to see that you have good solder connections and that they're not strained into shorting or similar when you pack them in the case. At the very least, remove it from the case until you can figure out how to get it working again. That will tell you what to look for when you try to put it back in the case.


----------



## fordgtlover

I have finished the first of three I have to build. The casework and fitting the board into the tiny little cable DAC case is a pain, but I digress.

 Whiel this one works, the output of this DAC seems very low. I need to turn my amp up waaay past what I normally would, just to get decent (not loud) volume. Is this normal or might something be wrong. The sound is clear, but very low.

 Any thoughts?


----------



## royewest

Quote:


  Originally Posted by *fordgtlover* /img/forum/go_quote.gif 
_...the output of this DAC seems very low. I need to turn my amp up waaay past what I normally would, just to get decent (not loud) volume. Is this normal or might something be wrong. The sound is clear, but very low..._

 

Sorry if this is bad new, but this is not my experience for either of the two Bantam's I've built. The volume is slightly lower, but within the same quarter-turn of my amp's pot as other USB DACs...


----------



## bperboy

Quote:


  Originally Posted by *fordgtlover* /img/forum/go_quote.gif 
_I have finished the first of three I have to build. The casework and fitting the board into the tiny little cable DAC case is a pain, but I digress.

 Whiel this one works, the output of this DAC seems very low. I need to turn my amp up waaay past what I normally would, just to get decent (not loud) volume. Is this normal or might something be wrong. The sound is clear, but very low.

 Any thoughts?_

 

Maybe double check that all of the computer's volume settings are maxed?


----------



## tomb

Either that, or fordgtlover mistakenly put a 3.3V TPS chip in for IC2. That would make output voltage and therefore, volume, much lower than normal.


----------



## fordgtlover

Quote:


  Originally Posted by *royewest* /img/forum/go_quote.gif 
_Sorry if this is bad new, but this is not my experience for either of the two Bantam's I've built. The volume is slightly lower, but within the same quarter-turn of my amp's pot as other USB DACs..._

 

Cheers. I only have the through hole components to go on the second one. I'll finish it and see how it compares.

 My primary DAC has an op amp output stage, so presumably has a much high output signal than the Bantam.

  Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_Maybe double check that all of the computer's volume settings are maxed?_

 

I'm outputting through ASIO and Foobar. I've double checked that all of the PC volumes are maxed.


----------



## fordgtlover

I just finished the second one and it's the same. So, I've either made the same mistake on both, the same fault is occurring on both, or they are both working as expected.


  Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_Maybe double check that all of the computer's volume settings are maxed?_

 

Update: It seems that it's worth checking the volume three times. 
	

	
	
		
		

		
		
	


	




 The volume level I had been confirming was for my USB to SPDIF converter rather than the Bantam DAC... too many devices.

 Two more bantam DACs live. I have one more to go.

 Oh, and once again, that small case is quite the hassle. I sure hope the recipient of this build appreciates it.

 Thanks for another great project Tomb.


----------



## tomb

You're welcome. Glad to hear it was just a software adjustment. Those are the easiest to fix (well, mostly).

 The small case is as it's intended: _small_. Since the small size of the Bantam is a major feature, we felt obligated to find the smallest case possible for the board. There's not another one made that can be as small unless it's Royewest's Duplo block. I may start carrying those at Beezar as an alternative to the "official" one.


----------



## fordgtlover

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_You're welcome. Glad to hear it was just a software adjustment. Those are the easiest to fix (well, mostly).

 The small case is as it's intended: small. Since the small size of the Bantam is a major feature, we felt obligated to find the smallest case possible for the board. There's not another one made that can be as small unless it's Royewest's Duplo block. I may start carrying those at Beezar as an alternative to the "official" one.
	

	
	
		
		

		
			



_

 

Hi Tomb, this is a great project and the size of the cable DAC is pretty small, which in itself is only a minor hassle. I've just been a little frustrated today because I've had to disassemble this a few times because I was unable to solder the cable shield properly.

 On the other hand, I have had two successes with the SSOP 28 DAC. I wasn't overly confident with soldering it. But I am thrilled that I'm two for two at the moment.

 Once again, great project and support. It doesn't dissappoint.


----------



## JamesL

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_There's not another one made that can be as small unless it's Royewest's Duplo block._

 

If you don't mind making a few modifications, the hammond 1551h makes for a even tighter fit and is about 1/3 the price. 
	

	
	
		
		

		
		
	


	



 Though I gotta admit.. those duplo blocks were pretty amazing.


----------



## royewest

The only real hitch to the Duplo block is it isn't hollow inside and the hard plastic is tricky to work with (well for me -- I suspect others are more adept at this kind of thing). I Dremeled and x-acto-carved with various tools on each and I will confess it wasn't easy. It carves ok if you have a sharp tool and you can cut it with the dremel saw, but it tends to melt.

 On the other hand, they're cheap and come in colors and they're compatible with a large cast of characters!


----------



## fordgtlover

I've posted this elsewhere on head-fi, but I'll post here for people looking specifically at the Bantam. Here are a pair in basic black boxes. No fancy 'royewest' creativity here


----------



## fordgtlover

I'm not sure if this tip has already been suggested, but I'll throw it out there anyway.

 The cable I used on the cable DAC was a really tight fit in the grommet I had. I rubbed a VERY small amount of talcum powder onto the first 4 or so inches of the cable and the result was a cable that could be moved in and out without busting any one of my sphincters.

 When I say I rubbed a VERY small amount, I mean I dusted my hands with talcum powder, then wiped my hands together once or twice to dust off the excess, and then wiped the cable with one hand. It doesn't require much at all. More powder would work, but the clean up will be messy.

 I hope this helps someone.


----------



## tomb

Quote:


  Originally Posted by *fordgtlover* /img/forum/go_quote.gif 
_I'm not sure if this tip has already been suggested, but I'll throw it out there anyway.

 The cable I used on the cable DAC was a really tight fit in the grommet I had. I rubbed a VERY small amount of talcum powder onto the first 4 or so inches of the cable and the result was a cable that could be moved in and out without busting any one of my sphincters.

 When I say I rubbed a VERY small amount, I mean I dusted my hands with talcum powder, then wiped my hands together once or twice to dust off the excess, and then wiped the cable with one hand. It doesn't require much at all. More powder would work, but the clean up will be messy.

 I hope this helps someone._

 

Great tip! Nice BantamDAC's, too - is that an LED lighting effect or Ford GT blue on those cases?


----------



## royewest

Very clean, fordgtlover.

 What 3.5mm jack is that?


----------



## ruZZ.il

looks like this, but I think I got similar ones elsewhere. Also, when I ordered from markertek, I got gray ones! I think it may have been my mistake though.. Anyway, clean work indeed! 
	

	
	
		
		

		
		
	


	




 I'm still marveled at the (how)little bantam..


----------



## fordgtlover

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Great tip! Nice BantamDAC's, too - is that an LED lighting effect or Ford GT blue on those cases?
	

	
	
		
		

		
		
	


	


_

 

The powder works well, and if you choose wisely you could have your cable smelling of Old Spice or something similarly attractive 
	

	
	
		
		

		
		
	


	




.

 I'd love to say it was an intentional artistic lighting effect, but in reality it's just my inability to operate the digital camera properly. It's simply an incorrect colour balance setting.

 The boxes are your basic black with the blue LED.


  Quote:


  Originally Posted by *royewest* /img/forum/go_quote.gif 
_Very clean, fordgtlover.

 What 3.5mm jack is that?_

 

It this one from Mouser. I had a few left in my spares bin. I think they look pretty good, and have been recommended a few times on this board.

  Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_looks like this, but I think I got similar ones elsewhere. Also, when I ordered from markertek, I got gray ones! I think it may have been my mistake though.. Anyway, clean work indeed! 
	

	
	
		
		

		
		
	


	




 I'm still marveled at the (how)little bantam.._

 

Thanks, and yes it is pretty small.


----------



## ruZZ.il

Ah yeah, thats the one from mouser! 
	

	
	
		
		

		
		
	


	




 I like those jacks...

 x2 on the good tip, ay.


----------



## linuxworks

also posted elsewhere but what the heck..
















 that's the bantam dac in its small 'cable dac' case, but with the cables removed and 2 rca's installed in the only places in THAT case that will take rcas 
	

	
	
		
		

		
		
	


	




 this gave me an idea. maybe I could make my PPA amp fit this in a cool way.

 yup, it worked. transferred the jack spacing over to my PPA and made a rear panel for this very purpose. the rca's hold the small dac up and its actually stronger than you'd think (you find this out when you try to pull them apart) 
	

	
	
		
		

		
		
	


	




 (can you say 'no analog cable'? sure, I knew you could.)


----------



## rds

The Nichicon HN 1500uF 6.3 V seems like a very nice replacement for the currently recommended Panasonic FM. It has lower ESR and ripple current than the equivalent Panasonic FM and is the same size as the 1000uF FM.


----------



## Hayduke

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_The Nichicon HN 1500uF 6.3 V seems like a very nice replacement for the currently recommended Panasonic FM. It has lower ESR and ripple current than the equivalent Panasonic FM and is the same size as the 1000uF FM._

 

Now I'm confused. I thought you wanted a higher number for the ripple current spec of a capacitor.


----------



## fordgtlover

I finished the board work on my 3rd Bantam this evening. It lives.


----------



## tomb

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_Now I'm confused. I thought you wanted a higher number for the ripple current spec of a capacitor. 
	

	
	
		
		

		
		
	


	


_

 

No, actually, it's better on both counts. It's just might have been interpreted like that because of the way rds typed it.

 Nichicon HN - 1500uf 6.3V, 10 x 12.5mm
 Impedance - 0.018, Ripple - 1760

 Panasonic FM - 1000uf 6.3V, 10 x 25mm
 Impedance - 0.038, Ripple - 1290

 The HN type caps appear to be another one of Mouser's uncataloged treasures - similar to the KOA/Kiwame resistors. I'll give one a try and report back when I can. Thanks, rds!


----------



## pinkfloyd4ever

oh snap, looks like they have a few of the Nichicon HZ series too, which is supposed to be even lower impedance


----------



## Nicolas2305

Hey there, I just populated my first Board and... it doesn't work. My computer don't seem to see the DAC at all. LED is lit but nothing happen in my computer. I was looking for a step by step check like with the Mini³ but there isn't any on the Bantam website. 

 Tomorow I'll go through the schematic to check everything. I was just wondering, on all those SMD parts, I haven't found any markings so I assumed there wasn't any polarity for those, was I wrong?

 Thanks

 EDIT: I also want to know if there's a way to check/troubleshoot the DAC chip?


----------



## Hayduke

Quote:


  Originally Posted by *Nicolas2305* /img/forum/go_quote.gif 
_Hey there, I just populated my first Board and... it doesn't work. My computer don't seem to see the DAC at all. LED is lit but nothing happen in my computer. I was looking for a step by step check like with the Mini³ but there isn't any on the Bantam website. 

 Tomorow I'll go through the schematic to check everything. I was just wondering, on all those SMD parts, I haven't found any markings so I assumed there wasn't any polarity for those, was I wrong?

 Thanks

 EDIT: I also want to know if there's a way to check/troubleshoot the DAC chip?_

 

The inductors, resistors and capacitors do not have polarity. Obviously the chip and the transistors do. The through hole caps do have polarity, but I suspect you were aware of that since you were thinking about it for the smd parts.

 Double check your soldering on the IC. Maybe even reflow all the joints once more just to make sure.

 I am also looking for some troubleshooting info. I posted on the DIYforums, but so far, have not gotten any response


----------



## markieta

NVM...


----------



## tomb

There are really only a few things you can check. I hate to say it, but it's a pretty small board to troubleshoot and not a lot is possible. We've had one builder completely remove a DAC chip, re-solder it, and have it work, but I would never have thought that could work. 
	

	
	
		
		

		
		
	


	




 There are three primary voltages you can check, but the rest is more or less checking for continuity between the traces on the board and the pins of the DAC chip:

 1. Voltage across C11 - this checks for the IC1 regulator, which should be 3.3VDC.
 2. Voltage across C13 - this checks for the IC2 regulator, which should be 4.75VDC.
 3. Voltage from CR to OG and from CL to OG - this must be checked at the first lead of CR or CL closest to the DAC chip, with OG. It's difficult to measure unless you turn the board over. This measures the proper offset voltage of the DAC audio output. It should be splitting the 4.75VDC from IC2 into a plus and minus ~2.38VDC. Of course, if you measure after the capacitors, the DC will be blocked and you shouldn't get a reading.

 Just an FYI, but it's _very_ easy to short out the DAC chip at the audio outputs. If it's exposed to almost anything without the coupling caps in the circuit - CL and CR - it's most likely fried.

 I've copied this answer onto DIYForums.org as well.
	

	
	
		
		

		
		
	


	





 EDIT: The LED is across the unregulated 5V of the USB bus. So, it really doesn't indicate anything except that the USB is plugged in.


----------



## Hayduke

Thanks Tom

 I wasn't complaining or anything 
	

	
	
		
		

		
		
	


	




 I know we're all busy and someone would respond at some point. I got lots of other projects to keep me busy lol

 So I'm sure my connections are good, so I likely have a bad IC? bummer.
 I probly shorted something trying to troubleshoot the hum.

 I read how qusp got his off. It sounds like a sound technique, but I would expect all the other parts to fall off with it 

 Now I have to decide if the rework time is worth it or if I should start over. I'm thinking I would basically have to disassemble the board in the same order I built it to avoid losing anything. hmmmm. Maybe I'll pull off the TH parts then remove the IC. Any of the other SMDs that come off, I'll just reorder with a new IC.


----------



## tomb

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_Thanks Tom

 I wasn't complaining or anything 
	

	
	
		
		

		
		
	


	




 I know we're all busy and someone would respond at some point. I got lots of other projects to keep me busy lol

 So I'm sure my connections are good, so I likely have a bad IC? bummer.
 I probly shorted something trying to troubleshoot the hum.

 I read how qusp got his off. It sounds like a sound technique, but I would expect all the other parts to fall off with it 

 Now I have to decide if the rework time is worth it or if I should start over. I'm thinking I would basically have to disassemble the board in the same order I built it to avoid losing anything. hmmmm. Maybe I'll pull off the TH parts then remove the IC. Any of the other SMDs that come off, I'll just reorder with a new IC._

 

Well, before you go to that length - have you checked the other things I mentioned?

 BTW, the first thing I should've said to check is whether you remembered to *put C16 on the R8 pads*. That can change everything if you haven't.

 More than one builder has reported bad operation or a PC that wouldn't recognize the board when only the TPS chips had bad solder joints. Again, checking the voltage across the C11 and C13 capacitors will tell you whether they're operating OK.

 Checking the output voltage is a little more difficult, but that can pinpoint whether you've got an issue with the DAC. In almost every case I've seen, if the DAC chip is fried then the analog output voltage will be messed up on one channel or the other - or both.


----------



## Hayduke

No, I didn't check those values yet. I did check them once before. At least I think it was those values. I know I checked some voltages when I first built it, but I can't recall where I found the info. I only posted that question in hopes there were other test points to look at. When I checked them the first time everything was good, so if they aren't good now, I probably fried something.

 I'll check those points tonight.

 Will this tell me if the DAC is bad? Or does this only check the regulators?

 The PC is still recognizing the DAC as "USB Speakers". I just get no sound.

 The parts for this are fairly inexpensive, so I might just order more parts this week. There are some other parts I need too. Maybe I'll see how well I can remove the parts with my heat gun first.


----------



## linuxworks

I may have a sick sense of humor, but part of the fun is to build it and see 'did it work?'.

 if so, then rejoice. if not, look for obvious physical things wrong, look under different light, move the object around under the light and deflux and look again if you have to.

 for me, it was all about physical inspection. so far, 2 of them have worked (out of 2).

 if things didn't work after reflowing, I'd probably junk it and start with a fresh new board and start again. its almost an all or nothing affair.


----------



## tomb

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_No, I didn't check those values yet. I did check them once before. At least I think it was those values. I know I checked some voltages when I first built it, but I can't recall where I found the info. I only posted that question in hopes there were other test points to look at. When I checked them the first time everything was good, so if they aren't good now, I probably fried something.

 I'll check those points tonight.

 Will this tell me if the DAC is bad? Or does this only check the regulators?

 The PC is still recognizing the DAC as "USB Speakers". I just get no sound.

 The parts for this are fairly inexpensive, so I might just order more parts this week. There are some other parts I need too. Maybe I'll see how well I can remove the parts with my heat gun first._

 

Go back on two of my posts and you'll see that the output voltage checks for the DAC chip. If you don't get good output voltage ahead of the coupling capacitors (2.85VDC on the right and left channel), and the regulators check out, the chip is fried. Unfortunately, the PC can recognize the DAC even if the PCM chip outputs are fried.

 In the end, I agree with what linuxworks says - it's almost an all or nothing affair, but I didn't want to sound discouraging. It happens to all of us - I have two Alien DACs with fried chips and I still don't know why, exactly.

 Be very careful with whatever measurements you make of the PCM chip if it's plugged in (I wouldn't do it except at those points I mentioned). A slip of the probe across two of the pins may be all it takes to fry it. That's why when making reference to checking the PCM chip for continuity with the board traces: you must do it with the power off (not plugged into USB).

 I would also never mess with powering one up without the coupling capacitors in place, and don't connect it to an audio device without ensuring that it's been on long enough to charge those same coupling capacitors. In normal usage, you almost needn't concern yourself with this - it's done automatically. So, it's not like a Bantam is constantly in peril of the very next short. It's just that while building one up, if you try to test it, you can easily fry it before you ever get any use out of it - if proper precautions aren't made.


----------



## Hayduke

I'm not really too worried about it given the low cost. Trying to make this one work is more of a "can I do it" sort of thing. I may have done it when measuring with my DMM, but I thought it worked since then.

 My brother borrowed my meter and broke the points off my probes. They still work, but they are kind of stubby now. He also lost the alligator clips and bent the wires on the "grabber" probes. Needless to say, I don't loan him tools anymore 
	

	
	
		
		

		
		
	


	




 Anyway, thanks for all the help and for make the BantamDAC and Beezer available for all of us


----------



## Zigis

Hi,
 can anyone in US, who are going to order parts in Digikey in near future, buy extra BantamDAC BOM x 2 and send me to Europe, Latvia? 

 I ordered 2 boards and low ESR caps, and then found, that both places where I buy parts (Swedish Elfa and German Distrelec) have not ferrites and regulator chips, other parts probably I can find, however prices here is much higher.

 I can pay with Paypal.

 Thanks,
 Zigis.


----------



## Nicolas2305

I might have to order in the next month but I'm not sure when. I'll pm you when I'll be ready to arrange things and see if you still need the parts.


----------



## Hayduke

It looks like IC2 is dead 
	

	
	
		
		

		
		
	


	




 I don't get any DC voltage from OG to the out put cap input pins either, but I suspect this is because either the IC is fried, or it isn't operating because it's missing one of the voltages it needs.

 I wish I knew if the IC was fried.

 I'm planning to build a couple more of these DACs so I guess I'll order an extra TPS793475 and see if I can get this one working. If that doesn't fix it, the IC must be bad too.

 I have another question about this DAC. I'd like to incorporate it into an amp. Can you think of anything I should know before trying this?

 Basically, I want a USB plug on the back of the amp as one of the inputs, or perhaps the only input. One of my co-workers wants a MHSS with a built-in DAC. I planned to use one of these at work to feed a MHSS also, so I proposed putting both into the same case. Any problems with wiring the outputs of the BantamDAC directly to the inputs of a MHSS?


----------



## tomb

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_It looks like IC2 is dead 
	

	
	
		
		

		
		
	


	




 I don't get any DC voltage from OG to the out put cap input pins either, but I suspect this is because either the IC is fried, or it isn't operating because it's missing one of the voltages it needs.

 I wish I knew if the IC was fried._

 

Sorry to say you do. If you can't measure 4.75V across the C13 capacitor, IC2 is either dead or not soldered correctly. You are correct that it's pointless to check the analog output voltage on the DAC in that case, since it gets the voltage for the outputs from IC2.
  Quote:


 I'm planning to build a couple more of these DACs so I guess I'll order an extra TPS793475 and see if I can get this one working. If that doesn't fix it, the IC must be bad too.

 I have another question about this DAC. I'd like to incorporate it into an amp. Can you think of anything I should know before trying this?

 Basically, I want a USB plug on the back of the amp as one of the inputs, or perhaps the only input. One of my co-workers wants a MHSS with a built-in DAC. I planned to use one of these at work to feed a MHSS also, so I proposed putting both into the same case. Any problems with wiring the outputs of the BantamDAC directly to the inputs of a MHSS? 
 

You might want to wait for the Millett MAX V1.2. It incorporates the BantamDAC mounted right on the board with a relay - similar to the headphone protective relay it already has - to switch conveniently between RCA inputs and the Bantam. Plus, it will have the improved power supply of the MiniMAX.

 The SSMH is a great little amp, but the MAX is really a step above. That's not a slight on the SSMH, just that the two amps compete in different niches.

 If you do hook one up to an SSMH, I'd put 100ohm resistors in the OR and OL connections from the Bantam to the amp input. There's a lot of voltage bouncing around on the SSMH until those heaters come up on the 19J6's. The two AlienDACs I fried were in testing while connected to an SSMH PCB. It so happens that I didn't have the coupling caps attached well enough (multiple VitQ's) and so the DAC chips were not protected as they should've been. Still ... never happened on a MAX - it has a more "refined" startup characteristic. The MAX is definitely more expensive, though, so there are tradeoffs with both amps.


----------



## bperboy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_You might want to wait for the Millett MAX V1.2. It incorporates the BantamDAC mounted right on the board with a relay - similar to the headphone protective relay it already has - to switch conveniently between RCA inputs and the Bantam. Plus, it will have the improved power supply of the MiniMAX._

 

Argh!! Tom, you're killin me! But at the same time, it's oh so wonderful!


----------



## tomb

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_Argh!! Tom, you're killin me! But at the same time, it's oh so wonderful! 
	

	
	
		
		

		
		
	


	


_

 

Yes - keep it under your hat, though. We don't want everyone finding out.
	

	
	
		
		

		
		
	


	




 There's more news coming about the Bantam, but I can't tell yet.


----------



## bperboy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yes - keep it under your hat, though. We don't want everyone finding out.
	

	
	
		
		

		
		
	


	




 There's more news coming about the Bantam, but I can't tell yet.
	

	
	
		
		

		
		
	


	


_

 

Oh dear oh dear.. i'm gonna end up with five amps and three different sources 
	

	
	
		
		

		
		
	


	













 Time to update my signature!


----------



## Hayduke

Do you have an ETA on the 1.2 boards? The site says a few weeks, but I don't know when that was put up.

 Now that you're incorporating the DAC into it, that sounds like the new Max might be exactly what I'm looking for to use at work!

 Part of me doesn't want to wait for it, but the reality is, I won't be ready to start working on it for at least a month, so it's fine.


----------



## patton713MW

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_There's more news coming about the Bantam, but I can't tell yet.
	

	
	
		
		

		
		
	


	


_

 

Ok, so what you're telling me is that if I only want to make one, and I haven't ordered the parts yet, I should wait for the news?


----------



## tomb

Quote:


  Originally Posted by *patton713MW* /img/forum/go_quote.gif 
_Ok, so what you're telling me is that if I only want to make one, and I haven't ordered the parts yet, I should wait for the news?_

 

The news does NOT involve changes - YGPM.


----------



## Zigis

Thanks Nicolas2305, it should be nice, I am waiting.
 Zigis.


----------



## Nemo de Monet

For what it's worth, since someone was asking about alternative film capacitors a page or two ago, size limitations mean that I've had to swap out the enormous Soviet 4uf MBGO-1 capacitors I _was_ using in order to fit a BantamDAC in the same case as my newly-completed "SOHA I". _(Hey, it only too me two years to finish; better late than never.)_ Anyway, the MBGOs were the best-sounding of the capacitors I'd tried (various Wimas, the blue BD(?) box caps everyone uses, some EROs, Soviet KBGs, numerous others) on the Bantam, but just too huge.

 Anyway, I picked up some 4,7uf Axon radial polypropylene caps a while ago, and while they're still huge (the two capacitors, together, are about as big as the rest of the BantamDAC), they're a bit more usable, at least where I need them to fit. Best of all, they sound - to me - indistinguishable from the MBGO PIOs, and are about $0.25 cheaper. 
	

	
	
		
		

		
		
	


	




 And, yes, I know 4uf, or 4.7uf, is _gross overkill_, but I find I can generally hear a discernible difference, at least at the bass end of things, between 1uf and 2uf coupling capacitors... and for most film caps, the cost difference between 2uf and 4uf is a couple of cents, so... 
	

	
	
		
		

		
		
	


	




_(Bonus nerd aside: the "Axon" logo looks for all the world like "AEON"; when the caps showed up in the mail yesterday, my partner asked what they were, and I said "flux capacitors". I got punched a couple seconds later, but it was worth it...)_


----------



## Hayduke

Well I got my BantamDAC working last night. I guess the hum with my first one may have been a bad joint or part or something. This new one is dead quiet and sounds great!

 I built 2 this time. The second one just needs the TH parts soldered. I'm planning to incorporate it into a Millet Hybrid Starving Student. Anything special I should do when building it inside the amp?

 I'm thinking I will use 2 DPDT switches. One will allow switching of the input between the DAC and a 3.5mm (or maybe RCAs). The other will route the DAC's output to those same connectors. I'm going to sit down and draw out the circuit this weekend, but in my head I think it works


----------



## tomb

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_Well I got my BantamDAC working last night. I guess the hum with my first one may have been a bad joint or part or something. This new one is dead quiet and sounds great!

 I built 2 this time. The second one just needs the TH parts soldered. I'm planning to incorporate it into a Millet Hybrid Starving Student. Anything special I should do when building it inside the amp?

 I'm thinking I will use 2 DPDT switches. One will allow switching of the input between the DAC and a 3.5mm (or maybe RCAs). The other will route the DAC's output to those same connectors. I'm going to sit down and draw out the circuit this weekend, but in my head I think it works 
	

	
	
		
		

		
		
	


	


_

 

I burned out 2 Alien DACs connecting them to the Starving Student. Just be aware to have your Bantam plugged in to the USB plenty of time before you power on the SSMH. There's a lot of voltage hopping around on that thing in startup. Plus, the 48V is enough to cause small arcing in the switches and connections, I think. At least one time, I heard a very loud pop when connecting the Alien. Needless to say, it was fried.

 The idea is to make certain those coupling caps are charged. Any arcing or back-emf is going to fry the DAC chip if there's any chance those coupling caps are not charged.

 An alternate method would be to connect a couple of 100ohm resistors between the output of the Bantam and the input to the SSMH.

 You may not have any trouble at all - I may have been doing some stupid stuff by connecting/disconnecting while testing the SSMH PCB prototype. Just in case, though ...


----------



## Hayduke

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I burned out 2 Alien DACs connecting them to the Starving Student. Just be aware to have your Bantam plugged in to the USB plenty of time before you power on the SSMH. There's a lot of voltage hopping around on that thing in startup. Plus, the 48V is enough to cause small arcing in the switches and connections, I think. At least one time, I heard a very loud pop when connecting the Alien. Needless to say, it was fried.

 The idea is to make certain those coupling caps are charged. Any arcing or back-emf is going to fry the DAC chip if there's any chance those coupling caps are not charged.

 An alternate method would be to connect a couple of 100ohm resistors between the output of the Bantam and the input to the SSMH.

 You may not have any trouble at all - I may have been doing some stupid stuff by connecting/disconnecting while testing the SSMH PCB prototype. Just in case, though ..._

 

Thanks Tom

 Sorry to ask again. I couldn't find where I had asked about this before, but I just found it on the previous page of this thread 
	

	
	
		
		

		
		
	


	




 I understand what you're explaining. If the coupling caps are charged, they will protect the DAC a bit. What affect will the resistors have on the sound though? Will they just attenuate it a bit? The MHSS has enough gain I think, so this probly isn't a big deal.

 And I am planning to build a MAX once the new boards are available. It sounds like it will have everything I'm looking for 
	

	
	
		
		

		
		
	


	




 I'm gonna build a SOHA II also though, so I'll probably be putting a BantamDAC in there too. I'll make the build modular though as I am curious about the y1. I'll build one of those too eventually, but I'd rather have a couple more amps first. The Bantam sounds so good, I don't have a pressing need to make another DAC 
	

	
	
		
		

		
		
	


	




 One last question on the Bantam...
 Would there be any benefit to changing the output caps? ie larger electrolytics bypasses with some films. I think I read that you did some testing and thought the Wimas were the best, but since they are in the signal path, I'm wondering if the standard cap arguments could be made.

 Thanks again for this project. I'm so happy to be able to listen to my entire music collection instead of using the iPods


----------



## Zigis

Hi Tom,
 I just measure DC on my SS amp's input. Wen I turn on amp, DC slowly go from 0 to -13 mV in one channel and 0 - 0.7 mV in other, wen volume pot is on max, wen pot is in half way - 2 mV in one channel and 0 in second.
 More interesting thing - wen I switch of amp, there is up to -370 mV in both channels 3-5 sec. and then slowly go down!
 All DC voltages are negative.
 Do you think 100 ohm before 50 K pot may help in this situation? Anyway amp's pot in real life newer stay on max.
 Zigis.


----------



## tomb

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_<snip> ... but I'd rather have a couple more amps first. The Bantam sounds so good, I don't have a pressing need to make another DAC 
	

	
	
		
		

		
		
	


	


_

 

Glad to hear it! 
	

	
	
		
		

		
		
	


	







  Quote:


 One last question on the Bantam...
 Would there be any benefit to changing the output caps? ie larger electrolytics bypasses with some films. I think I read that you did some testing and thought the Wimas were the best, but since they are in the signal path, I'm wondering if the standard cap arguments could be made.

 Thanks again for this project. I'm so happy to be able to listen to my entire music collection instead of using the iPods 
	

	
	
		
		

		
		
	


	



 

The best I've heard so far is the Vishay-Roederstein MKT 1.0uf 63V. These look exactly like and are the same size as the Wima's, except that they are apple-green in color instead of red. A bit darker and not as forward in the midrange as the Wima's, but fantastic detail (they are super-fast) and very deep bass.

 I'll never build another Bantam with Black Gates again - the Roederstein's are that good. Keep in mind that's an opinion, but I've built at least a half-dozen Alien's with Black Gates and one with 0.66uf in Vitamin Q's - plus a Bantam with Black Gates. The VitQ's seem to lose nothing in bass even at 0.66uf, but the Bantam with the Roedersteins blow it away. The Black Gates are not even in the same league as the VitQ's and Roederstein's.

 So, no - I don't think there's anything to gain by using electrolytics - bypassed or not.


----------



## tomb

Quote:


  Originally Posted by *Zigis* /img/forum/go_quote.gif 
_Hi Tom,
 I just measure DC on my SS amp's input. Wen I turn on amp, DC slowly go from 0 to -13 mV in one channel and 0 - 0.7 mV in other, wen volume pot is on max, wen pot is in half way - 2 mV in one channel and 0 in second.
 More interesting thing - wen I switch of amp, there is up to -370 mV in both channels 3-5 sec. and then slowly go down!
 All DC voltages are negative.
 Do you think 100 ohm before 50 K pot may help in this situation? Anyway amp's pot in real life newer stay on max.
 Zigis._

 

Hmm ... well this sounds like proof that there's back-emf on the input jacks of the SSMH.
	

	
	
		
		

		
		
	


	




 I suspected as much, but had never actually measured it.

 Either situation would be enough to fry an Alien or BantamDAC, if the coupling caps did not have enough time to charge. Based on my experience at burning out Aliens and your measurements, I think the 100ohm inline resistors are probably prudent when connecting an Alien or Bantam to the SSMH.


----------



## Hayduke

At the risk of...




 hehe

 What's the difference between putting the DAC inside the amp housing and connecting it with a phono or RCA connector? Does the tiny amount of capacitance in those connections protect the DAC?

 I'm not trying to disagree or argue, I just want to understand. I trust you and appreciate the help 
	

	
	
		
		

		
		
	


	




 Isn't the pot at the input on the MHSS sorta like the resistor at the DAC like you're proposing?


----------



## tomb

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_At the risk of...





 hehe

 What's the difference between putting the DAC inside the amp housing and connecting it with a phono or RCA connector? Does the tiny amount of capacitance in those connections protect the DAC?

 I'm not trying to disagree or argue, I just want to understand. I trust you and appreciate the help 
	

	
	
		
		

		
		
	


	




 Isn't the pot at the input on the MHSS sorta like the resistor at the DAC like you're proposing?_

 

I'm not sure I understand to what you're referring. Yes, it wouldn't make any difference. However, if you're referring to our V1.2 MAX with the onboard Bantam - I've never blown a DAC with a MAX - just the SSMH. It may be a combination of the higher voltage involved (48V), the switching power supply, the high bias and the tube heaters in the amp circuit - but that's just a guess.

 As for the second part, it may very well be the ground that develops a fault (voltage) while the switching power supply adjusts to the load of the heaters. So, it may have nothing to do with the input signal leads and pot, per se.

 EDIT: Admittedly, I'm only offering conjecture based on observation. I don't know what causes it, but apparently, it's measureable. Even so, I've said several times - it could very well be my own stupidity that blew a couple of DACs. It's not necessarily that the SSMH has an issue, but that a direct-to-coupling-capacitor DAC may have some vulnerabilities with certain hookups.


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The VitQ's seem to lose nothing in bass even at 0.66uf, but the Bantam with the Roedersteins blow it away. The Black Gates are not even in the same league as the VitQ's and Roederstein's._

 

reaaaallyyy, damn... just what I need, an excuse for another project, Tom 
	

	
	
		
		

		
		
	


	







 Just to make sure, you're saying the Roedersteins blow away even the VitQs? And Wimas are close to the Roedersteins but a little different?


----------



## tomb

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_reaaaallyyy, damn... just what I need, an excuse for another project, Tom 
	

	
	
		
		

		
		
	


	







 Just to make sure, you're saving the Roedersteins blow away even the VitQs? And Wimas are close to the Roedersteins but a little different?_

 

Yes, the Roedersteins blow away the VitQ's. The VitQ's may have a smoother midrange, but the Roedersteins are just soooo faaasst. The Wima's come close, but to be perfectly honest, they drop off in the bass after running them in for about a week. They sound a bit thick and very bassy at first, then they open up, but the bass goes away.

 The BantamDAC-Roedersteins have been running as my primary source since a few days aftter we started selling the BantamDAC. I'm so impressed with them I plan on trying a pair of the upgraded MKP versions as output bypasses on the MiniMAX. 'Course, that doesn't mean they'll work doing that - bypassing is different and always a little unpredictable.

 However, I see no reason to put anything else in a BantamDAC except those things. I'm going to start selling them at beezar, but only because our international folks have trouble with Mouser's exorbitant international shipping fees. There's no reason not to order a dozen or so from Mouser for those of us who are stateside:

75-MKT1817510064

 (Mouser's pic is bad on that page - these things are apple-green in color.)


----------



## ShinyFalcon

Would it hurt if I extended the four wires of the pigtail cable a tad bit by soldering four pieces of 1-2" of copper wire (perhaps some Canare star quad) to the four cables and soldering the coppers to its respective spot on the PCB? I'm looking for a bit of freedom when I start casing my cable DAC, since I'm not used to working with cramped cases.


----------



## tomb

Quote:


  Originally Posted by *ShinyFalcon* /img/forum/go_quote.gif 
_Would it hurt if I extended the four wires of the pigtail cable a tad bit by soldering four pieces of 1-2" of copper wire (perhaps some Canare star quad) to the four cables and soldering the coppers to its respective spot on the PCB? I'm looking for a bit of freedom when I start casing my cable DAC, since I'm not used to working with cramped cases._

 

You might want to use channels at the bottom-half of the case lip, instead of drilling holes through the center of the sides. Then you could just lay the whole assembly in place and screw the lid on. The cable entries may look a little asymmetric with the case, but the whole thing is so small, I doubt it would matter.

 The other thing is that you need 5 wires soldered onto the USB pads, not four - one is the shielding. Canare has that, I believe, but the the Canare would not be following the USB cabling standard. You might lose data integrity, depending on how far you carry the leads. I've used leaded, off-board USB jacks before, but there are more wires and some of the wires are larger to compensate for the lack of a USB-standard cable configuration.


----------



## Hayduke

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I'm not sure I understand to what you're referring. Yes, it wouldn't make any difference. However, if you're referring to our V1.2 MAX with the onboard Bantam - I've never blown a DAC with a MAX - just the SSMH. It may be a combination of the higher voltage involved (48V), the switching power supply, the high bias and the tube heaters in the amp circuit - but that's just a guess.

 As for the second part, it may very well be the ground that develops a fault (voltage) while the switching power supply adjusts to the load of the heaters. So, it may have nothing to do with the input signal leads and pot, per se.

 EDIT: Admittedly, I'm only offering conjecture based on observation. I don't know what causes it, but apparently, it's measureable. Even so, I've said several times - it could very well be my own stupidity that blew a couple of DACs. It's not necessarily that the SSMH has an issue, but that a direct-to-coupling-capacitor DAC may have some vulnerabilities with certain hookups._

 

Sorry, I guess I wasn't clear. I'll try again.

 I was asking about incorporating a BantamDAC inside a MHSS. You suggested some resistors between the DAC's output and the amp's input. My question was regarding these resistors.

 How is wiring the output of the DAC directly to the amp's input different from using an interconnect? My BantamDAC is a cable version, so I have a 3.5/mini phono plug going into my MHSS amp. So from the BantamDAC's PCB to the MHSS pot is some SPC wire -> male 3.5 -> female 3.5 -> more SPC wire -> pot. So essentially you're saying to replace the 2 connectors with a resistor. I'm just not understanding why I would need it if I don't need it now.

 Again, I'm not disagreeing. It sounds like the MHSS has a good chance to fry a DAC, and now you have me concerned about using the DAC externally too. As a result, I've developed a routine of powering up the DAC and the amp before connecting them to each other.


----------



## tomb

Just an FYI, but I've started carrying the 1.0uf 63V Roederstein MKT's. Our international folks pay a huge penalty ordering from Mouser and this may help. Also, the Nichicon UHN 1500uf 6.3V capacitor will be available as an alternative for C7. I haven't tried one yet, but the ESR and ripple ratings are better than the Panasonic FM (it's the same size). Either one at C7 is fine, of course. The Panasonic FM is well proven, while the Nichicon UHN may have great potential. When one of you builds one with the UHN, please let us know how well it worked (or if you noticed at all).


----------



## Juaquin

I've just ordered all the parts and went with the Nichicon; assuming that I don't fry anything (which is a distinct, perhaps likely, possibility), I'll let you know how it sound. Then again I've never heard the Bantam with the Panasonic so I'm afraid it won't be a very comparative analysis.


----------



## Juaquin

So I just finished it today - wasn't too bad except the DAC itself, that took a while. I plugged it into my computer, there was no LED light and both TPS got really hot, and heard something like a little sizzling noise. USB device not recognized. I'm guessing there's something wrong with the USB power input circuit. Any ideas? I would measure voltages over those caps but I don't want to plug it in and risk more damage. 

 I'm going to order more TPS chips in anticipation of those being fried, but does anyone have any ideas as to what needs to be fixed? Also, do you think the DAC is now fried?


----------



## tomb

Quote:


  Originally Posted by *Juaquin* /img/forum/go_quote.gif 
_So I just finished it today - wasn't too bad except the DAC itself, that took a while. I plugged it into my computer, there was no LED light and both TPS got really hot, and heard something like a little sizzling noise. USB device not recognized. I'm guessing there's something wrong with the USB power input circuit. Any ideas? I would measure voltages over those caps but I don't want to plug it in and risk more damage. 

 I'm going to order more TPS chips in anticipation of those being fried, but does anyone have any ideas as to what needs to be fixed? Also, do you think the DAC is now fried?_

 

Can you get us a pic? Maybe someone can spot something. As significant as your symptoms sound, it must be a part in the wrong place/installed incorrectly.


----------



## Juaquin

Sure, but be warned that it's my first SMD work. Not all the resistors/caps are straight and solder blob sizes are all different, but it looks to me like everything has a strong electrical connection without any shorts (I tested continuity on everything I could). And I haven't cleaned the flux or electrical tape.

http://www.brettinman.com/bantam/1.JPG

http://www.brettinman.com/bantam/2.JPG

http://www.brettinman.com/bantam/3.JPG


----------



## tomb

Quote:


  Originally Posted by *Juaquin* /img/forum/go_quote.gif 
_Sure, but be warned that it's my first SMD work. Not all the resistors/caps are straight and solder blob sizes are all different, but it looks to me like everything has a strong electrical connection without any shorts (I tested continuity on everything I could). And I haven't cleaned the flux or electrical tape.

http://www.brettinman.com/bantam/1.JPG

http://www.brettinman.com/bantam/2.JPG

http://www.brettinman.com/bantam/3.JPG_

 

Well, shoot! I'm stumped right now. I don't see anything out of place - electrolytics appear to be oriented correctly, the USB wiring appears correct (my first suspicion once I realized you were making a CableDAC), and I don't see any part out of position. You've got quite a few cold solder joints, but they don't look bad enough to cause the symptoms you cited.

 Based on that, my suspicion would be the TPS chips, too. Is there a chance you got one swapped for the other - IOW, is the 4.75V chip in the position that's used for the 3.3V chip and vice-versa?


----------



## Juaquin

Nope, I checked like 5 times before soldering them (and a couple times after, just because). 

 Is it possible a fried DAC would in turn do this to the TPS chips? I had to rework the DAC a number of times and it's entirely possible it took some damage.

 Also, isn't the LED tied straight to the USB 5V line (with resistor)? If I plugged into USB why wouldn't the LED come on, even if the rest of the circuit is fried?


----------



## Juaquin

So I plugged it back in and got some nice tiny sparks on one of the pins. Here's a modified picture with the general area (I was a little busy lunging to pull out the cable when I saw sparks to notice the exact pin). 

http://www.brettinman.com/bantam/4.jpg

 However, it looks like the pin that's tied directly to the USB +5V according to the layout. So I've now confirmed that, at the very least, the DAC and TPS chips are all dead. Think there's any damage to any of the other components?


----------



## tomb

Quote:


  Originally Posted by *Juaquin* /img/forum/go_quote.gif 
_So I plugged it back in and got some nice tiny sparks on one of the pins. Here's a modified picture with the general area (I was a little busy lunging to pull out the cable when I saw sparks to notice the exact pin). 

http://www.brettinman.com/bantam/4.jpg

 However, it looks like the pin that's tied directly to the USB +5V according to the layout. So I've now confirmed that, at the very least, the DAC and TPS chips are all dead. Think there's any damage to any of the other components?_

 

Yep - I think you've interpreted it correctly. That's the pin that takes 5V from the USB.

 I doubt seriously that any other part is messed up. In fact, one or both of the TPS chips may still be good. I can't speak for the DAC, though. Sounds like there must be a bridge under those DAC pins somewhere.

 EDIT: So sorry you're having such trouble.


----------



## Juaquin

Haha no problem, I knew this wouldn't be a cakewalk - like I said, it's my first time working with SMD and it looks like I got unlucky with that DAC chip. This is good experience though, I'm an electrical engineering major and they sure don't have any classes on soldering (especially SMD work), which I always found weird.

 Ordering a new DAC and a couple TPS, just in case. Thanks for the help.


----------



## Juaquin

Oh, is it advisable to just drop in the new DAC without changing out the TPS, or could that cause more frying? I guess I may as well replace the TPS at the beginning anyways.


----------



## Pars

Quote:


  Originally Posted by *Juaquin* /img/forum/go_quote.gif 
_Oh, is it advisable to just drop in the new DAC without changing out the TPS, or could that cause more frying? I guess I may as well replace the TPS at the beginning anyways._

 

Heat typically means either a part is oscillating or its trying to drive a dead short. I would guess the latter in your case. I would try removing the DAC chip and then ohming out the power circuits (TPS) referencing the schematic. If I didn't see anything shorted (particularly the reg outputs, i might plug it in and check the voltages. If those check out, then I would just replace the DAC chip.


----------



## Hayduke

Quote:


  Originally Posted by *Juaquin* /img/forum/go_quote.gif 
_Oh, is it advisable to just drop in the new DAC without changing out the TPS, or could that cause more frying? I guess I may as well replace the TPS at the beginning anyways._

 

I would replace the 2 TPS as well, but they might still be OK. If you ordered them with a new DAC though, why not?

 A little advice on replacing the DAC. I was able to get mine off fine with a heat gun, but make sure you remove the TH parts first. I cooked the MKP caps pretty good, so I decided to replace all 4 TH caps and the crystal just in case 
	

	
	
		
		

		
			





 I haven't actually got that Bantam working yet. I just ordered the replacement parts this week. I already have 1 working cable DAC. This 1 and another are for building into amps.


----------



## joneeboi

The PCM2702 datasheet says that it complies with USB 1.0 specs. Does that mean that it connects as a 1.0 device or just that it meets 1.0 standards? Will the USB host be acting as a 1.0 host or a 2.0 device? Are the 2.25W from USB (minus whatever the DAC and REGs are drawing) still available when the DAC is plugged in?


----------



## Juaquin

That means that it is a 1.0 device. It will work in USB2.0 hubs or hosts because 2.0 is backwards compatible with 1.0. The specs of the device will not effect the amount of power outputed to other devices (except minus the power drawn by the device).


----------



## joneeboi

Thanks, Juaquin. That's very helpful.


----------



## Juaquin

No problem. That said, I would make sure the DAC is plugged directly into a computers motherboard USB ports (the ones on the back of the computer). These have the highest power output (especially over hubs) because they draw from a huge power supply.


----------



## joneeboi

Really? They don't all draw from the same power supply? If I have USB ports both on the front and on the back, then the front ones will have less power capability than the rear ones?


----------



## Nemo de Monet

I think he meant more in the sense of "better into the motherboard, than an unpowered hub". A single USB port - on the PC itself - can only provide 500ma, and while you _can_ daisy-chain hubs off of it (a four-port hub plugged into another four-port hub, giving you seven open ports), unless one (or all) of those hubs are self-powered (i.e. have their own power supply) you're splitting that 500ma between all the ports, and devices connected to them.

 I have my BantamDAC plugged into a USB port on the back of my PC, and have no problems whatsoever. I used to have an Alien DAC plugged into a powered external hub, and would get weird noises when using any of several USB-powered hard drives on the same hub...


----------



## tomb

Quote:


  Originally Posted by *Nemo de Monet* /img/forum/go_quote.gif 
_I think he meant more in the sense of "better into the motherboard, than an unpowered hub". A single USB port - on the PC itself - can only provide 500ma, and while you can daisy-chain hubs off of it (a four-port hub plugged into another four-port hub, giving you seven open ports), unless one (or all) of those hubs are self-powered (i.e. have their own power supply) you're splitting that 500ma between all the ports, and devices connected to them.

 I have my BantamDAC plugged into a USB port on the back of my PC, and have no problems whatsoever. I used to have an Alien DAC plugged into a powered external hub, and would get weird noises when using any of several USB-powered hard drives on the same hub..._

 

I've experienced harshness and noise when plugging into a powered hub as well. It's best to use a linear-regulated power supply (no USB hub comes with one of those), just like we do all of our headphone amps. A TREAD set for 5V would take care of it.

 That said, there's no reason you can't parallel several BantamDACs on the same PC and or an unpowered hub. It will take a lot of them to exceed the power supply available from the PC.
	

	
	
		
		

		
		
	


	




 You'd need software that can recognize the different "USB Speakers (#)" separately though, for them to independently play different music - assuming that's possible (I haven't tried it).


----------



## Nemo de Monet

IMO, the problem is more to do with crappy, cost-cutting hub design than what's powering them. (Dear Belkin: Power-supply decoupling capacitors. Learn what they are, use them, love them.) I know it's fun to blame SMPSes at every opportunity, but I don't really think they have much to do with the problem. (After all, a computer PSU is a SMPS, and one quite cheaply and badly designed, at that.)

 I've actually toyed with the idea of creating a DIY USB powered-hub project, so the world would have at least one hub that's designed well... but that's kind of off-topic, here.


----------



## Hayduke

Quote:


  Originally Posted by *Nemo de Monet* /img/forum/go_quote.gif 
_IMO, the problem is more to do with crappy, cost-cutting hub design than what's powering them. (Dear Belkin: Power-supply decoupling capacitors. Learn what they are, use them, love them.) I know it's fun to blame SMPSes at every opportunity, but I don't really think they have much to do with the problem. (After all, a computer PSU is a SMPS, and one quite cheaply and badly designed, at that.)

 I've actually toyed with the idea of creating a DIY USB powered-hub project, so the world would have at least one hub that's designed well... but that's kind of off-topic, here. 
	

	
	
		
		

		
		
	


	


_

 

Perhaps we need another thread, but I was having the same thought. With the proliferation of USB devices, I find that I run out of ports on the PC often. I have a hub too, but even though it's powered it still doesn't do some things well, such as charging iPods.

 I was thinking about opening it up and seeing how it's wired. It has a wall wart and a power connector. I might be able to just use a different power supply.


----------



## Nemo de Monet

Usually the power supply isn't the problem; it's the design of the entire hub. Some hubs, even powered, won't provide more than 100ma per port; others won't provide more than 500ma split between all ports, even with external power.

 There are a couple of attractive-looking hub controllers out there in reasonably-large packages (32-64 pin SMD devices with 0.8mm lead spacing) that are probably within the abilities of the truly dedicated DIYer.

 See Fig. 13, page 15 of the Texas Instruments TUSB2046B datasheet for a "reference design" of a decently-done powered hub. The voltage-protection chips needed (SN75240) are 8-pin devices available as DIP or TSSOP packages; the power switch recommended (TPS2044B) is a 16-pin SOIC package. If someone put together a DIY hub based around this design, I think anyone who can assemble a BantamDAC would be able to manage it, as well. The TUSB2046B is ~$3 at Mouser; the SN75240s around $1 apiece; the TPS2044B is around $2.25, and a 3.3v regulator is, what, a buck? Ten to twelve bucks in ICs, another ten bucks in discrete resistors and capacitors, and maybe fifteen bucks for everything else, like connectors, a crystal, and so on. I don't know how many people would be willing to spend $50 or more to make their own USB hub, but I'm pretty confident it _could_ be done. The downside is that with this kind of thing, troubleshooting has to be fairly nonexistent: it works, or it doesn't; and if it doesn't, there's not much you can do, really.

 The TPS2044B doesn't have some of the "nice to have" features some of the other, newer, hub controllers do, but it's cheap, and has 0.8mm lead spacing...

 We probably _should_ go start another thread.


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## tomb

Not a problem. I've suspected the cr*ppy power supplies, but maybe you are right - it's the cr*ppy board design used to create the hub.


----------



## Logistic

Just got the parts for my Bantam Dac today. Thanks Tom for the quick shipping and great packaging.

 I put together the dac, but windows says the device malfunctions and cannot be recognized. I checked the TPS regulators and it is 2.2V across C11 instead of 3.3. Also, it is 1.5 instead of 2.4V across CR and CL. What could be wrong? Could it be a bad 3.3 regulator? I didn't heat it up too much. Also, is the 3.3 regulator on a 3.3 rail? I measured 5V across C14.

 Thanks

 Edit: Yes it lives!!!!! I'll leave this up in case anyone else has the same problem, but I found that the ground leg of the regulator wasn't soldered correctly, a few seconds with the soldering iron and now everything works great!


----------



## tomb

Quote:


  Originally Posted by *Logistic* /img/forum/go_quote.gif 
_Just got the parts for my Bantam Dac today. Thanks Tom for the quick shipping and great packaging.

 I put together the dac, but windows says the device malfunctions and cannot be recognized. I checked the TPS regulators and it is 2.2V across C11 instead of 3.3. Also, it is 1.5 instead of 2.4V across CR and CL. What could be wrong? Could it be a bad 3.3 regulator? I didn't heat it up too much. Also, is the 3.3 regulator on a 3.3 rail? I measured 5V across C14.

 Thanks

 Edit: Yes it lives!!!!! I'll leave this up in case anyone else has the same problem, but I found that the ground leg of the regulator wasn't soldered correctly, a few seconds with the soldering iron and now everything works great!_

 

That's great news! Yes, there is very little trouble-shooting with a Bantam. Either the parts are incorrect or the soldering - one or the other.


----------



## joneeboi

I'm wondering about the inrush current of the BantamDAC. I read in a TI white paper that the input decoupling capacitor should be no larger than 10uF unless there is current limiting. The BOM shows a 22uF cap at C8. Is that just part of a low pass filter or are the inductors after C8 limiting the current?


----------



## tomb

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_I'm wondering about the inrush current of the BantamDAC. I read in a TI white paper that the input decoupling capacitor should be no larger than 10uF unless there is current limiting. The BOM shows a 22uF cap at C8. Is that just part of a low pass filter or are the inductors after C8 limiting the current?_

 

Do you have a reference? I just got through searching the TI site and can't find anything pertaining to what you state. The datasheet for the PCM2702 doesn't mention anything, either.

 FWIW, there are two ferrites between the C8 and the C7 cap. Their resistance value is 600R, so yes, there is current limiting. However, both are applied to the USB power bus, not the dac "input". Also, the TI datasheet indicates that for the VBUS pin (what the USB bus is connected to), "this pin NEVER consumes USB bus power." Further on, they state it even more explicitly - "VBUS (pin 8) never consumes USB bus power, it is used only for detecting the connection of the USB bus." That would imply - I guess - that current is not drawn through this connection on the PCM chip, anyway.

 This is all in the power circuit, so there is no audio signal pass filter in play.


----------



## cetoole

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Do you have a reference? I just got through searching the TI site and can't find anything pertaining to what you state. The datasheet for the PCM2702 doesn't mention anything, either.

 FWIW, there are two ferrites between the C8 and the C7 cap. Their resistance value is 600R, so yes, there is current limiting. However, both are applied to the USB power bus, not the dac "input". Also, the TI datasheet indicates that for the VBUS pin (what the USB bus is connected to), "this pin NEVER consumes USB bus power." Further on, they state it even more explicitly - "VBUS (pin 8) never consumes USB bus power, it is used only for detecting the connection of the USB bus." That would imply - I guess - that current is not drawn through this connection on the PCM chip, anyway.

 This is all in the power circuit, so there is no audio signal pass filter in play._

 

Actually, quick correction. The ferrites, by nature, have very low resistance, being basically a straight wire encased in ferrite. The 600ohm figure is at something like 100khz, though I dont have time to look up the spec right now.


----------



## joneeboi

Sorry for the vague description, Tom. I was reading SLYT118, and what I'm talking about is right on the first page. The input cap on the BantamDAC is 22uF, and the 600 ohm ferrite resistance is at 100MHz (top right corner). I couldn't find any references on Google on USB ripple. And even though VBUS doesn't consume any power, C8 is still storing and supplying charge for the power chips. Then again, not everyone always conforms to the USB-IF's standards, and even still, BantamDACs are plugging in perfectly fine with all kinds of USB ports all over the world. amb's sigma power supplies have a low-pass filter which he describes as providing a soft-start characteristic, but I don't know if that applies to what's going on with C8, L3/L4 and C7 since the L's have a max 0.9 ohm DC resistance (according to the Mouser product page).

 Is there an inherent USB ripple characteristic or will it be mainly implementation-specific (eg. laptop, desktop computer, etc.)? I'm not sure how most computers are made up, but I do know that computer PSUs are switchers that have 12V and 5V outputs. Does the 5V go into the motherboard and then into the USB port or does it just go straight to the USB port? Rather, is there switching noise from the PSU, or would that be filtered on most motherboards? I'm just full of questions.


----------



## tomb

Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_Actually, quick correction. The ferrites, by nature, have very low resistance, being basically a straight wire encased in ferrite. The 600ohm figure is at something like 100khz, though I dont have time to look up the spec right now._

 

Oops! Thanks for that correction!
	

	
	
		
		

		
			





  Quote:


  Originally Posted by *joneeboi* 
_<snip>Is there an inherent USB ripple characteristic or will it be mainly implementation-specific (eg. laptop, desktop computer, etc.)? I'm not sure how most computers are made up, but I do know that computer PSUs are switchers that have 12V and 5V outputs. Does the 5V go into the motherboard and then into the USB port or does it just go straight to the USB port? Rather, is there switching noise from the PSU, or would that be filtered on most motherboards? I'm just full of questions._

 

Whatever's going on, it was more or less decided early on with the Alien DAC that a regulated 5V supply (or battery) had little effect on improving the sound quality of the AlienDAC. Most likely this conclusion was drawn from Amb's tests, although it appears that there's a marginal improvement in the graphs of the ones with separate power supplies:
_"The noise floor does not appear to change significantly whether the Alien DAC power comes from the USB or from a 9V battery (both regulated via the onboard REG101UA chip)."_
 (Ti Kan's Alien DAC)

 There's no room for that on the Bantam, anyway.


----------



## tomb

Just curious - many of you have purchased the Nichicon UHN 1500uf 6.3V electrolytic to use as C7. Have any of you completed a Bantam yet with one of those caps - how did it work? Anyone who's done both - and compared Panasonic FM 1000uf vs. Nichicon UHN 1500uf?

 I'm sure the differences are subtle, at best, but still - it would be nice to confirm how the UHN works. (Obviously, I haven't tried one yet.)


----------



## linuxworks

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_Is there an inherent USB ripple characteristic or will it be mainly implementation-specific (eg. laptop, desktop computer, etc.)? I'm not sure how most computers are made up, but I do know that computer PSUs are switchers that have 12V and 5V outputs. Does the 5V go into the motherboard and then into the USB port or does it just go straight to the USB port? Rather, is there switching noise from the PSU, or would that be filtered on most motherboards? I'm just full of questions._

 

all USB sources I've seen come from the motherboard and never directly from the +5 on the molex connectors on the PSU.

 that said, I'm not sure that mobos filter their +5v 'for export' (devices attached). any device attached should kind of assume the worst if its going to live in any 'mish mash random' computer config that one can find in the wild 
	

	
	
		
		

		
		
	


	




 I have a pc in front of me that has a major grounding problem on the front panel usb ports but is fine on the rear (mobo mounted) ports. same pc, same computer, same everything but the front panel ports are wire-connected via some offboards and the rear panel ports are off the IO shield in the usual rear panel area, direct pcb mounted.

 (I noticed this when I was using a 'grounded' 3 prong wallwart and taking its +12 and -12 and putting them in series and forgetting (doh!) about the centertap and that IT WAS GROUNDED to the green ac ground wire! I was trying to get +24v with no CT for my PPA amp and yet when I used a bantam dac plugged into the 'wrong' usb port and that PS, I would get hum and then even eventual USB port disconnection! it wasn't until I found this unknown centertap and removed it that things finally worked well on BOTH front and rear usb ports!)

 moral: assume the worst from a USB port on any kind of pc. then take whatever precautions you think you need, on your own 'end' of things. volts in a PC are evil volts, so to speak


----------



## ludoo

I can attest to the fact that different computers have different characteristics: my home PC USB bus is dead quiet, my office laptop is unusable (with an Alien). I have a Bantam to build in the next few days (btw thanks Tomb, fast shipping and great prices), and if it's as noisy as the Alien I will either have to try external power or resort to a DAP with diymod or similar.


----------



## Logistic

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Just curious - many of you have purchased the Nichicon UHN 1500uf 6.3V electrolytic to use as C7. Have any of you completed a Bantam yet with one of those caps - how did it work? Anyone who's done both - and compared Panasonic FM 1000uf vs. Nichicon UHN 1500uf?

 I'm sure the differences are subtle, at best, but still - it would be nice to confirm how the UHN works. (Obviously, I haven't tried one yet.)_

 

I have built one Bantam with the UHN and as far as I can tell, it works great. I can't comment on the Panasonic, but with the UHN windows detects it quickly and the music sounds great.


----------



## tomb

Quote:


  Originally Posted by *Logistic* /img/forum/go_quote.gif 
_I have built one Bantam with the UHN and as far as I can tell, it works great. I can't comment on the Panasonic, but with the UHN windows detects it quickly and the music sounds great._

 

Thanks! That answers my question!


----------



## Hayduke

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Just curious - many of you have purchased the Nichicon UHN 1500uf 6.3V electrolytic to use as C7. Have any of you completed a Bantam yet with one of those caps - how did it work? Anyone who's done both - and compared Panasonic FM 1000uf vs. Nichicon UHN 1500uf?

 I'm sure the differences are subtle, at best, but still - it would be nice to confirm how the UHN works. (Obviously, I haven't tried one yet.)_

 

The Bantam I'm using now uses the Pannies, but I have parts for 2 more and plan to use the UHN caps this time. I'll have to devise a way to test them with all other components being equal since I plan to build the next bantam into my SOHA II. Oh wait, I'll have a mini input on that amp, so I can just plug in the other Banatm. I should be able to provide some info for you next week Tom.


----------



## ludoo

I just finished my BantamDAC, a pity I slipped (twice) with the manual drill when drilling the LED hole, just before closing it. Did I say I hate casework? I also had a broken LED and some missing contacts on the DAC chip, and it took me some time and some head scratching before fixing both.

 I used the suggested output caps, and on first listen I have to say they sound brighter and with less body than the Blackgates I have in my Alien. I will wait a bit before forming a definitive impression, as they might change with burnin.

 Thanks Colin and Tomb for a really great and cheap project, and the wonderful documentation.


----------



## linuxworks

here's a hint, maybe: to try to recover that panel from the scratch why not try to give it a 'brushed' look? I might try sandpapering the whole surface where you made the slip and while it may change the look a bit (lol) at least it will hide the scratch.

 last idea, have an engraver make a 'name badge' kind of thing that you can just use to cover that top plate.

 next time, cover the surface with sticky shelf paper or masking tape or something and drill over top THAT, as a protector


----------



## ludoo

Quote:


  Originally Posted by *linuxworks* /img/forum/go_quote.gif 
_here's a hint, maybe: to try to recover that panel from the scratch why not try to give it a 'brushed' look? I might try sandpapering the whole surface where you made the slip and while it may change the look a bit (lol) at least it will hide the scratch._

 

Yes, it's what I plan on doing after I have switched the Vishay caps for a pair of Blackgate NX.

  Quote:


 next time, cover the surface with sticky shelf paper or masking tape or something and drill over top THAT, as a protector 
	

	
	
		
		

		
			




 

I usually do that, but here it was the very last thing and I was impatient to close it and give a listen, and overconfident as everything else worked.


----------



## tomb

Quote:


  Originally Posted by *ludoo* /img/forum/go_quote.gif 
_Yes, it's what I plan on doing after I have switched the Vishay caps for a pair of Blackgate NX.</snip>_

 

If I may be so bold to suggest ... you may be experiencing the classic higher-volume-switcharoo. There's no question the Black Gates have a higher output. You barely have to turn the volume knob with the BG's compared to the Vishay-Roedersteins. It's a trick, though - because the BG's are much noisier and higher in distortion by comparison. Yes, the Roedersteins may seem subdued, but crank that volume up and you'll be surprised. Bass is still there, impact is back, and the Roedersteins are very, very fast. You'll hear detail in the highs you've never heard with the BG's.

 Just MHO, of course, but I've listened to BG's on Aliens for quite awhile. Plus, my BantamCableDAC has BG's, too - but I'm going to switch them for the Roedersteins.


----------



## rds

I find the better the dac the more I end up cranking up the volume. I think it is related to the psychological effect of having less noise, distortion, etc in the signal. That is to say that the more noisy and distorted something is the louder it seems... at least to me.


----------



## ludoo

Tomb, thanks for the detailed comparison.

 What I found in the few hours since I've built it is that the Vishays have a brighter, more forward sound and less soundstage. The Blackgates seem to render the sound in layers, and have richer tones.

 I put on a pair of BG on the Bantam, and the sound got closer to that of my Alien but it still seems brighter with a more compressed soundstage, though less than with the Vishays. I will listen more carefully in the next few days, as it will be my office DAC for a while.

 And I still would like to try a pair of Obbligatos in a Bantam or Alien, as I love them in my SS.


----------



## ludoo

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_I find the better the dac the more I end up cranking up the volume. I think it is related to the psychological effect of having less noise, distortion, etc in the signal. That is to say that the more noisy and distorted something is the louder it seems... at least to me._

 

I observed the same thing when I got my first set of Stax last year: I used to listen to them at a higher volume than any other cans I had at the time.


----------



## tomb

Quote:


  Originally Posted by *ludoo* /img/forum/go_quote.gif 
_Tomb, thanks for the detailed comparison.

 What I found in the few hours since I've built it is that the Vishays have a brighter, more forward sound and less soundstage. The Blackgates seem to render the sound in layers, and have richer tones.

 I put on a pair of BG on the Bantam, and the sound got closer to that of my Alien but it still seems brighter with a more compressed soundstage, though less than with the Vishays. I will listen more carefully in the next few days, as it will be my office DAC for a while.

 And I still would like to try a pair of Obbligatos in a Bantam or Alien, as I love them in my SS._

 

Well, I have to defer to your own preferences and setup. Sometimes I forget that not everyone's the same. Everything I use for amplification are Millett MAXes/MiniMAXes - soundstage, layers, and richness is not an issue. So, I typically crave detail to bring out even more subtleties. So, whatever works for you, by all means.
	

	
	
		
		

		
		
	


	




 I was just hoping that you don't dismiss the Roederstein's quickly. There are many of us who agree that a good film cap will still beat BG's every time. Strangely, both the Wima's and the Roedersteins took a week to break-in. That sounds ridiculous, I know, but I swear it's true - or at least 4-5 hours every night for a week.
	

	
	
		
		

		
		
	


	




 I also prefer the Vishay-Roedersteins in the Bantam to an Alien that I have rigged up with VitaminQ's. The VitQ Alien is mighty, mighty nice - mids are luscious and musical, but the Roederstein definitely has more sparkle and even a tad more bass.


----------



## ludoo

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I was just hoping that you don't dismiss the Roederstein's quickly. There are many of us who agree that a good film cap will still beat BG's every time. Strangely, both the Wima's and the Roedersteins took a week to break-in. That sounds ridiculous, I know, but I swear it's true - or at least 4-5 hours every night for a week.
	

	
	
		
		

		
		
	


	


_

 

No, I won't dismiss them. I bought a small bag of them and will use them in other projects. I suspected these had not even started to break in, but I have tons of stuff to build/fix lined up waiting for some time, and the Bantam has to be ready for Monday at the office. 
	

	
	
		
		

		
		
	


	




 BTW, how are you liking Colin's HP-3 (or are they YH-3)? I know, a bit OT but I'm really curious.


----------



## tomb

Quote:


  Originally Posted by *ludoo* /img/forum/go_quote.gif 
_No, I won't dismiss them. I bought a small bag of them and will use them in other projects. I suspected these had not even started to break in, but I have tons of stuff to build/fix lined up waiting for some time, and the Bantam has to be ready for Monday at the office. 
	

	
	
		
		

		
		
	


	




 BTW, how are you liking Colin's HP-3 (or are they YH-3)? I know, a bit OT but I'm really curious._

 

From mid-to-highs, they're quite simply the finest pair of headphones I've ever heard in my life - but I don't want to overstate things.
	

	
	
		
		

		
		
	


	




 I still think my Head-Fi Grado HF-1's are the finest overall that I've heard with my MAXes - highs are closer than you'd think, mids have that Grado color, but the HF-1's have a real bass kick that's totally missing from Colin's YH-3's.

 I bought some Swisspers and some round makeup pads - I'm hoping to do some work on these new T50RP's as we speak. These Swisspers are cool. Maybe I'm barking up the wrong tree, but they're circular cotton pads about the size of a silver dollar and about 5/16th's of an inch thick - but they're the consistency of latex foam, not like felt. At the risk of going way OT, what do you think?


----------



## ludoo

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_From mid-to-highs, they're quite simply the finest pair of headphones I've ever heard in my life - but I don't want to overstate things.
	

	
	
		
		

		
		
	


	




 I still think my Head-Fi Grado HF-1's are the finest overall that I've heard with my MAXes - highs are closer than you'd think, mids have that Grado color, but the HF-1's have a real bass kick that's totally missing from Colin's YH-3's._

 

Wow! I'm glad you like them, I really do. And I've been lusting after HF-1s for quite some time, but it will be a while before I can afford a pair.

  Quote:


 I bought some Swisspers and some round makeup pads - I'm hoping to do some work on these new T50RP's as we speak. These Swisspers are cool. Maybe I'm barking up the wrong tree, but they're circular cotton pads about the size of a silver dollar and about 5/16th's of an inch thick - but they're the consistency of latex foam, not like felt. At the risk of going way OT, what do you think? 
 

Uhm, I've never had great results with cotton but who knows, maybe these will work. Felt usually has a higher density, and I also suspect wool fibers are better for damping bass, but the Swisspers might work too maybe just in a different way. I think you also need a "standard ortho damping package", I will try to mail you one as soon as I get the new cashmere felt, hopefully next week. And let us know when you try the Swisspers in the other thread.


----------



## ludoo

A quick update on my Bantam: I just connected it to the office laptop/SS, and despite its plastic case it has much less interference noises than my Alien. There's still some noises from the LCD monitor/surrounding cellphones and stuff, but it's low volume with very sensitive phones and not audible with the hard to drive orthos.

 Edit: it still sounds brighter than the Alien, but not worse just a different sound signature.

 Colin and Thomas, thanks again!


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## Hayduke

I doubt Tom has been holding his breath or anything, but my SOHA build got delayed due to a missing trim pot 
	

	
	
		
		

		
		
	


	




 As a result, I don't have the new Bantam tested yet. I should have the part sometime this week (I ordered it Friday night when I realized it was missing), so I'll try to provide some feedback on the difference between the Panasonic FM and the Nichicon UHN next week.


----------



## cetoole

Quote:


  Originally Posted by *ludoo* /img/forum/go_quote.gif 
_A quick update on my Bantam: I just connected it to the office laptop/SS, and despite its plastic case it has much less interference noises than my Alien. There's still some noises from the LCD monitor/surrounding cellphones and stuff, but it's low volume with very sensitive phones and not audible with the hard to drive orthos.

 Edit: it still sounds brighter than the Alien, but not worse just a different sound signature.

 Colin and Thomas, thanks again!_

 

Cheers Ludo! Glad it is working nicely for you.


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## ludoo

I spoke too soon: my bantam is dead. I was listening to music and suddenly I got silence, and Linux could not see it. I tried rebooting, changing USB port, nothing. The LED lights up, but the operating system does not detect it.

 This is getting annoying (and expensive): after a burnt Alien, now the Bantam. I will bring it home tonight and try to reflow the solder joints on the damn PCM chip. Then if that fails, I'll start thinking about a used non-DIY DAC for the office, as I'd like to listen to some music without having my DACs breaking each time.


----------



## tomb

Quote:


  Originally Posted by *ludoo* /img/forum/go_quote.gif 
_I spoke too soon: my bantam is dead. I was listening to music and suddenly I got silence, and Linux could not see it. I tried rebooting, changing USB port, nothing. The LED lights up, but the operating system does not detect it.

 This is getting annoying (and expensive): after a burnt Alien, now the Bantam. I will bring it home tonight and try to reflow the solder joints on the damn PCM chip. Then if that fails, I'll start thinking about a used non-DIY DAC for the office, as I'd like to listen to some music without having my DACs breaking each time._

 

Were you using it with the Starving Student? I hate to say it, but the Starving Student may be bad for DACs. As mentioned, it blew two of my Aliens, too. However, I've never had one issue with any other amp. Perhaps if we get the stuttering situation solved, it may be different.

 One important precaution: be sure you have the DAC plugged into the USB for several minutes before you plug it into the Starving Student or before you start up the Starving Student.

 I doubt that it would work one minute and then not the next - if it was a soldering issue, but I'm just guessing. Regardless, sorry to hear about your misfortune.
	

	
	
		
		

		
		
	


	




 EDIT: One other precaution would be to place some 100 ohm resistors between the output of the DAC and the input of the amp. I'm going to take some extensive measurements on the SSMH PCB when we get them built. The resistors may become a minimum requirement for the SSMH and a DAC.


----------



## ludoo

Thanks for the suggestions Tomb. Well, the DAC and amp had been playing for about 10 minutes when it stopped working. I paused the music, and when I hit play again, no DAC... With my Alien the DAC was still recognized, only one channel was completely dead. This time the DAC is not even seen on the USB bus...


----------



## tomb

Quote:


  Originally Posted by *ludoo* /img/forum/go_quote.gif 
_Thanks for the suggestions Tomb. Well, the DAC and amp had been playing for about 10 minutes when it stopped working. I paused the music, and when I hit play again, no DAC... With my Alien the DAC was still recognized, only one channel was completely dead. This time the DAC is not even seen on the USB bus..._

 

That does sound unusual. I don't know of any reason the DAC should get fried if it was up and running for that long. Maybe you're right - it was a solder connection that let loose.

 P.S. I put a link for the DXF file in the Starving thread for you.


----------



## Hayduke

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_One important precaution: be sure you have the DAC plugged into the USB for several minutes before you plug it into the Starving Student or before you start up the Starving Student._

 

I've been using my Bantam with my MHSS everyday for several weeks now. Sounds great btw 
	

	
	
		
		

		
			





 I don't wait several minutes after plugging the DAC into the PC's USB though. I give it about 1 minute or so, but I also don't attach the DAC to the amp while the amp is powering up. Basically, I plug the DAC into the PC. Then I turn on the amp. When the tubes have been glowing nicely for 30 seconds to a minute, I plug in the DAC then the headphones.

 Right now, I am transporting the MHSS and Bantam back and forth to work each day, so this is the routine I follow twice a day at least. Sometimes I'm paranoid and unplug the DAC if I turn the amp off 
	

	
	
		
		

		
		
	


	




 I agree though that Ludo's sequence of events doesn't make sense to me either. 
	

	
	
		
		

		
		
	


	




 Hope you get it solved Ludo.


----------



## ludoo

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_I agree though that Ludo's sequence of events doesn't make sense to me either. 
	

	
	
		
		

		
		
	


	




 Hope you get it solved Ludo._

 

Heh, it does not make sense to me either. I reflowed the PCM contacts last night, and still no go. Then instead of going to bed I started poking around with the multimeter, and had all kinds of strange voltages in the regulators. Can't remember what now, and it does not matter anyway as I must have slipped with the probe and one of them managed to produce some nice smoke. 
	

	
	
		
		

		
		
	


	




 I will stick to amps from now on, I guess. Lucky I managed to snatch an iPod mini for very cheap off ebay some time ago, so I will diymod it tonight and have a decent source for the office. And get new regulators next time I order something from Mouser. Did I say I hate digital SMD stuff?


----------



## Hayduke

Quote:


  Originally Posted by *ludoo* /img/forum/go_quote.gif 
_Heh, it does not make sense to me either. I reflowed the PCM contacts last night, and still no go. Then instead of going to bed I started poking around with the multimeter, and had all kinds of strange voltages in the regulators. Can't remember what now, and it does not matter anyway as I must have slipped with the probe and one of them managed to produce some nice smoke. 
	

	
	
		
		

		
		
	


	




 I will stick to amps from now on, I guess. Lucky I managed to snatch an iPod mini for very cheap off ebay some time ago, so I will diymod it tonight and have a decent source for the office. And get new regulators next time I order something from Mouser. Did I say I hate digital SMD stuff?_

 

If it's any consolation, my first Bantam didn't go well either, and I have a hug amount of SMD experience. Granted, when working in a production environment, we used solder paste 
	

	
	
		
		

		
		
	


	




 I was able to remove the DAC chip with my heat gun. I have replacement parts on hand (I cooked the Wima caps, so I'm replacing all the TH components), just haven't finished rebuilding that first DAC yet. I'll let you know if it works when I put the new parts in. I have no reason to think it won't. The PCBs are pretty well made, so they haven't suffered any damage from the rework.


----------



## tomb

OK guys and gals, it pains me to mention this (mostly because there are a couple of hundred new boards in stock) but -

 There is a defect in the PCB design. From all indications, it has no effect on the performance of the BantamDAC whatsoever. This is evidenced by more than a couple of hundred successful Bantams in circulation, including my own. So, I have no clue if this will make any difference. My guess is that it won't. However, the fix is so easy it almost makes no sense to _not_ do it:




 [size=xx-small](click for a very large pic)[/size]

 Pin 18 (AGNDR), the Right Analog Ground, was supposed to be Grounded (naturally). My guess is that this pin is finding plenty of return Ground path through the RCA connections and the Left Ground, since they are both combined eventually when the DAC is connected. Nevertheless, all that needs to be done is to scrape a bit of the green mask from the trace just above C3's right pad, and bridge the two with solder.

 In response to this error, I've completed all of the heretofore empty pages on the Bantam web site - SMD Soldering, Checks and Setup, Tweaks, etc., and added a "STEP 8a" explaining this fix in the normal step-by-step instructions. I'm also going to be carrying several new capacitor selections for the Bantam on beezar.com sometime this weekend.

 Sorry for this and I apologize because the error will be with us for awhile. I had ordered new boards that will enter the market soon and will still need this correction. However, I'd like to continue to keep the price at $2 each. Not trashing all of the new boards because of this trivial defect will let us preserve that price.


----------



## ruZZ.il

No worries. Seems like an easy fix (if you could call it that, since it isn't really broken).


----------



## lcpi

I just built one of these dacs, and have been pretty satisfied considering the ease of construction and price. I would guess that AGNDR is connecting to ground somewhere within the pcm2702. Just goes to show the over engineering in modern ic design.

 I am coming from a M-Audio Revolution 7.1, and in comparison I find the BantamDAC to have very light bass. I used the recommended Vishay-Roederstein caps, and am wondering if changing the caps to some of the higher capacitance electrolytics would make the bass punchier. Can someone comment on how much of an effect this would make?

 I am using the BantamDAC to drive Sony MDR-V6's directly without an amp, but I don't think that is the problem, as I have never known these headphones to need an amp.

 Any suggestions would be appreciated.


----------



## Logistic

When I ordered my case for my first Bantam, I ordered the wrong case, and it was too small for the Bantam. I decided to build a second bantam and mount some of the components off the board to fit. I used the 8x20 UHZ cap because it has better specs than the UHN and it fits. It is also significantly cheaper than the 10x12.5 version. I can confirm that it works just fine.

 Here is the result (Sorry for the bad pic quality):


----------



## ShinyFalcon

It was mentioned before that DACs are not meant to drive headphones and earphones directly. You will need an amp for any DAC. The BantamDAC is driving a low impedance, which is your headphones, while it expects a really high impedance (47k ohms) like those found on an amp's input, which would explain your lack of bass. Try it with a cheap CMOY or maybe your stereo receiver, and see how much nicer it would sound with a proper rig. If I listen to my γ1 DAC directly with my headphones, I get clipping, tons of sibilance, and very light bass.


----------



## linuxworks

some shots of my patched board:











 wasn't hard to do the patch.


----------



## tomb

Great pics, linuxworks!

 I just posted even more information to the BantamDAC website - over an hour's worth of Video Construction Tutorials:
BantamDAC Videos

 Not as good quality as Tangent's and I don't have a decent macro lens on my camcorder. Also, my head and hands block some of the shots.
	

	
	
		
		

		
		
	


	




 This was a first crack at this, though, but I promise to do better in the future!
	

	
	
		
		

		
		
	


	







 EDIT: I could be mistaken at this, but I believe this makes the BantamDAC the most thoroughly documented SMD DIY-project in existence!


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## ruZZ.il

Tom, I think you're competing against yourself here 
	

	
	
		
		

		
		
	


	




 I'm not sure there are any(/many) more over-all as detailed projects in the whole audio DIY scene. There's no wonder in how the amps/dacs that you work on have become such a success. Largely due to the devices themselves, but you've played a huge role to take that a (few!) step(s) further, which doesn't end at the web page. If I may though, I think the only thing lacking is a circuit description of sorts, but you're still the thrown holder in this domain 
	

	
	
		
		

		
		
	


	




 kudos on all the work! I'm really glad I had the opportunity to give something back for this.


----------



## ruZZ.il

Quote:


  Originally Posted by *linuxworks* /img/forum/go_quote.gif 
_some shots of my patched board:
 ...._

 


 Again, I just have to praise your photography! 
	

	
	
		
		

		
		
	


	




 I havent gotten around to trying out that light waving trick yet.. still will try. I need a new lens


----------



## linuxworks

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_Again, I just have to praise your photography! 
	

	
	
		
		

		
		
	


	




 I havent gotten around to trying out that light waving trick yet.. still will try. I need a new lens 
	

	
	
		
		

		
		
	


	


_

 

cheers 
	

	
	
		
		

		
		
	


	




 my usual procedure:

 1) import the raw image and don't do any sharpening until toward the end. leave most things at conservative levels (contrast, saturation, etc).

 2) keep image at full size (don't rescale!) until the very last step

 3) denoise once, maybe twice. I use neatimage as my de-noiser.

 4) use levels tool to fix whitebalance

 5) use 'shadow/highlight' to 'compress' the image and lower the bright spots (shiny areas) as well as bring out detail in dark areas

 6) increase saturation and contrast and maybe 1 light pass of sharpening (unsharp mask or 'smart sharpen
	

	
	
		
		

		
		
	


	




 7) finally, do a resize (I often resize to 1100px which is the max flicker will let me upload without *it* doing another resize/rescale on me)

 8) after the resize, it may need 1 more light pass of unsharp mask

 HTH


----------



## Zigis

Today I finished my first BantamDac, thanks Nicolas2305 for great helping with parts!
 This is my first real SMD work. 

 First time I finishing soldering, turn it on - nothing happens, chip was hot. I disconnect dac, and see - however I check DAC orientation few times, finally I solder it upside :{
 Then I desolder chip, turn on and check voltages - 4.7V was OK, 3.3v reg was fried. I replace reg, check again both voltages and solder new DAC chip.
 Wen I connect DAC again, nothing visible happens on monitor, wen I turn on Foobar, music come from DAC !

 I listen to music while searching info, how to put audio more dirrect from Foobar to DAC, I reed about this long time ago, can't find at the moment, any links?

 After about hour of listening, I start to find in contr.panel/sistem/device manager/sound, video and games controler. I find USB speaker, Onkio, TI PCM72702. While I reed this, music stop to sound.

 I try to restart DAC, restart PC several times - nothing! Every time I connect DAC, XP say - unknown USB device and no sounds. Wen I turn headamp volume to max, there is hiss. 
 What's wrong with dac? Enyone have this problem before?

 From Build in sound card music come.


----------



## linuxworks

its probably windows 
	

	
	
		
		

		
			





 disable any onboard sound or pci sound cards. disable in bios if you can. else go to control panel and disable at device manager.

 then reboot. windows likes that 
	

	
	
		
		

		
		
	


	




 reboot with NO sound card connected.

 then run control panel again. NOW plug in your usb sound card (bantam) and see some 'activity' on that panel. 

 now go to control panel for sound (speaker icon) and force this 'usb speakers' to be the default device. hit apply and save. reboot again (for good measure).

 with the usb sound device connected, do you see it as the default device, now?


----------



## Hayduke

Quote:


  Originally Posted by *Zigis* /img/forum/go_quote.gif 
_Today I finished my first BantamDac, thanks Nicolas2305 for great helping with parts!
 This is my first real SMD work. 

 First time I finishing soldering, turn it on - nothing happens, chip was hot. I disconnect dac, and see - however I check DAC orientation few times, finally I solder it upside :{
 Then I desolder chip, turn on and check voltages - 4.7V was OK, 3.3v reg was fried. I replace reg, check again both voltages and solder new DAC chip.
 Wen I connect DAC again, nothing visible happens on monitor, wen I turn on Foobar, music come from DAC !

 I listen to music while searching info, how to put audio more dirrect from Foobar to DAC, I reed about this long time ago, can't find at the moment, any links?

 After about hour of listening, I start to find in contr.panel/sistem/device manager/sound, video and games controler. I find USB speaker, Onkio, TI PCM72702. While I reed this, music stop to sound.

 I try to restart DAC, restart PC several times - nothing! Every time I connect DAC, XP say - unknown USB device and no sounds. Wen I turn headamp volume to max, there is hiss. 
 What's wrong with dac? Enyone have this problem before?

 From Build in sound card music come._

 

Linuxworks suggested the same first step I would try. I'm not sure why it would work then die. It could be a lot of things I suppose.

 I'm posting to address your first question about how to configure Windows. Here is a link that is pretty good. It's for a 24 bit DAC, so you should ignore that part and set Foobar to 16 bit.
Computer Audio Playback - Setup Guide - Benchmark

 I hope you figure out what happened to your DAC.


----------



## Zigis

Linuxworks, I try what you say ( I think I do it right? Device Manager/Sound video and audio controllers/C-Media AC97 Audio Device/C-Media WDM audio device/Properties/Do not use audio features on this device)
 After restarting and connecting DAC the same "unknown device" under small USB icon on taskbar. In device manager nothing new.
 I am afraid something with DAC happen. I solder chip with lot of solder and then use solder removing braid. Is it possible to remove too much solder with braid, loose contacts? I hope no.
 I try DAC on another PC without result.

 Hayduke, thanks for link, this is very usable too, however I am thinking about some program or plug in, allow to streaming dirrect from foobar to USB, bypassing Windows mixer and other parts.


----------



## linuxworks

cmedia ac97?? no, that's something else. your 'other' sound card.

 maybe disable that (red circle with line thru it) then reboot and see if THEN your 'usb speakers' sound device shows up.


----------



## Zigis

Yes, I now, this is motherboard build in soundcard, I disable it.
 Anyway, windows can't recognize device (PCM2702), "USB speaker" not show up.


----------



## linuxworks

one more question: is this connected DIRECTLY to your computer or via a usb hub?

 sometimes, hubs interfere (really).


----------



## Zigis

No hub. 
 This is relatively old PC with 2 x 2.0USB ports on back side.
 On other port is external HD. Wen I connect dac, HD start autoplay, I try connect dac with HD disconnected , not help.


----------



## tomb

I'm sitting in the DC airport "thumbing" this in on my BBerry, so if some of this has been suggested, I apologize for not seeing it.
	

	
	
		
		

		
		
	


	




 Go look at the Setup and troubleshooting page on the BantamDAC website. It details where you can measure the voltages on the Bantam board to confirm proper operation of the TPS regs.

 Other than that, I hate to say we don't recommend the "flood and suck" method for a reason - but it's not because you can suck too much solder up, it's because you expose the DAC chip to too much heat while doing it.

 If those voltages check out and it appears that the soldering is OK on the PCM chip, that would be my guess for the PC being unable to recognize the DAC: a fried chip.

 I hope that's not the case, though!!


----------



## linuxworks

do you see ANY activity when you are at the hardware control panel display? if you can show the usb 'tree' (leave the audio usb device disconnected) and then re-connect the dac, do you see ANY update or screen flurry? sometimes its fast but usually the screen updates to show that it 'saw' a new usb device.

 have you tried other usb ports (front and rear, etc)? I assume that you can put a drive or some other device into your usb port and that works - and that's the port you are using to test the dac with?


----------



## Zigis

Both voltages are correct, how do you think, chip may be half fried? In the beginning DAC worked about hour, and then simply stop.


----------



## Zigis

Linuxworks,
 I just try what you say, wen I connect dac, in DSB tree is new line - unknown device.
 Wen I dicsconnect dac, "unknown device" disappears.

 I have only 2 usb ports on PC back side, I try both. External HD work good in both ports.


----------



## linuxworks

if it says unknown device, could it be possible that windows just can't find usb-audio drivers for it?

 what happens if you DELETE that device (remove it from the tree), then reboot and let it discover it again?


----------



## linuxworks

Quote:


  Originally Posted by *Zigis* /img/forum/go_quote.gif 
_Both voltages are correct, how do you think, chip may be half fried? In the beginning DAC worked about hour, and then simply stop._

 

I'm now thinking its not windows anymore.

 if it worked before, then probably nothing is fried (my guess) and you have an open or short somewhere. maybe try reflowing some of the solder joints?


----------



## cobaltmute

Zigis, make sure your R3 is soldered properly. Windows will recognize a PCM chip but not interface with it properly if the pull-up resistor is not attached properly.


----------



## Hayduke

I'm in agreement with Linuxworks. Try reflowing the DAC pins again. Take heed of Tom's warning about getting it too hot though. Apply the iron for the shortest amount of time you can get away with and still reflow the solder. If you used the method of removing solder with a wick, it is very possible you made a joint that wasn't very solid. After an hour, perhaps the device got heated up and the metals expanded at different rates causing the fragile joint to break. I can't recall if you said how you're using hte DAC? Is this a cable DAC, seperate enclosure, or built into an amp? If it is built into an AMP, it would likely have gotten warm after an hour.

 Since it ran for an hour, it seems unlikely that the DAC chip is fried, although they are fragile. Luckily they are fairly inexpensive 
	

	
	
		
		

		
		
	


	




 Keep us posted on what you figure out.


----------



## Zigis

I delete unknown device, reconnect, and USB speakers is back!
 windows say device work properly, however music not come out, only small hiss, both voltages is still ok.

 I think there is something invisible damaged on board, while soldering, resoldering

 I check and resolder r3 too.


----------



## tomb

Quote:


  Originally Posted by *Zigis* /img/forum/go_quote.gif 
_I delete unknown device, reconnect, and USB speakers is back!
 windows say device work properly, however music not come out, only small hiss, both voltages is still ok.

 I think there is something invisible damaged on board, while soldering, resoldering

 I check and resolder r3 too._

 

There is one other thing you can check - but it takes a little bit of skill with the probes. See if you measure the lead pads for CL and CR referenced to ground. This should tell you the DC offset voltage coming from the analog outputs of the DAC. They should register something like + and - 2.25VDC (approx. positive and negative 1/2 of the 4.75 TPS regulator). If this is messed up, then the analog outputs may be fried. This can happen if CL and CR were not fully charged and you connected to an amp with some back-offset on the RCA jacks (like the SSMH on startup).

 Or - try reflowing some joints or seeing if those analog pads are actually connected. It could be several things.


----------



## Zigis

Today I resolder all chip legs and everything is perfect, except one thing - no sound in output
	

	
	
		
		

		
			





 Every time I connect DAC, USB speakers is there (before resoldering there was problem, sometimes turn on, sometimes no), both voltages are perfect, on output both channels measure 2.16V before caps.
 I even try to touch with multimeter "generator out" probe to output cap - there is sound, DAC is connected to amp.

 I don't now, what else there may be - windows recognize PCM, both voltages are correct, on output is half voltage - probably output stage is not burned, connection to amp is good.

 I have board and all parts, except 3.3v reg for second DAC, I think I make another try next week.
 No idea what else can I do with this one.


----------



## tomb

Quote:


  Originally Posted by *Zigis* /img/forum/go_quote.gif 
_Today I resolder all chip legs and everything is perfect, except one thing - no sound in output
	

	
	
		
		

		
		
	


	




 Every time I connect DAC, USB speakers is there (before resoldering there was problem, sometimes turn on, sometimes no), both voltages are perfect, on output both channels measure 2.16V before caps.
 I even try to touch with multimeter "generator out" probe to output cap - there is sound, DAC is connected to amp.

 I don't now, what else there may be - windows recognize PCM, both voltages are correct, on output is half voltage - probably output stage is not burned, connection to amp is good.

 I have board and all parts, except 3.3v reg for second DAC, I think I make another try next week.
 No idea what else can I do with this one._

 

Have you tried Foobar? Some media players such as that one allow you to independently select the output device (USB Speakers). There are some instances where the internal sound card will refuse to let go as the default sound output device for the PC. The only way you can overcome this is to use a media player that lets you select the output device manually.

 It's a reasonable guess, I think. If the computer recognizes the device as "USB speakers" and you've measured the correct offset voltage on the output (you are), then it should work.

 Is it possible you have some sort of wiring error with the output jacks? That's the only other thing I can think of.


----------



## Nemo de Monet

Might want to double-check the volume settings via the control panel, as well; make sure the sliders are set at reasonable levels, and that nothing's muted which shouldn't be.

 Been there, done that.


----------



## Zigis

Tom, you are genius! Thats it! I switch Foobar output to USB speakers and it work!

 However things like You Tube not work and I don't now how to switch it. I use Firefox.

 Interesting, in the same beginning, wen DAC work about hour, I try it with Foobar, You tube, other video clips in news portal, everything works.

 I listening now Andre Previn/Joe Pass/Ray Brown on Foobar/BantamDAC/MHSS/HD508, it's fantastic !
 Thank you all for great helping.
 Any ideas how to get dac soun from you tube and others? I am too lazy to switch outputs every time.


----------



## Zigis

Thanks, Nemo de Monet, i check it several times, even now (my You tube problem) everything is on max, nothing muted.

 By the way, anyone now about plugin used to bypass mixer and other windows parts, direct steaming from Foobar to USB. I read about this in different forums, folks use it as audiophile standard thing, can't find now.


----------



## Nemo de Monet

Quote:


  Originally Posted by *Zigis* /img/forum/go_quote.gif 
_By the way, anyone now about plugin used to bypass mixer and other windows parts, direct steaming from Foobar to USB. I read about this in different forums, folks use it as audiophile standard thing, can't find now._

 

I belive you're thinking of ASIO, usually implemented with one of the ASIO4ALL drivers.


----------



## cegras

Quote:


  Originally Posted by *Zigis* /img/forum/go_quote.gif 
_Tom, you are genius! Thats it! I switch Foobar output to USB speakers and it work!

 However things like You Tube not work and I don't now how to switch it. I use Firefox.

 Interesting, in the same beginning, wen DAC work about hour, I try it with Foobar, You tube, other video clips in news portal, everything works.

 I listening now Andre Previn/Joe Pass/Ray Brown on Foobar/BantamDAC/MHSS/HD508, it's fantastic !
 Thank you all for great helping.
 Any ideas how to get dac soun from you tube and others? I am too lazy to switch outputs every time._

 

Control panel -> Sound


----------



## Hayduke

Quote:


  Originally Posted by *Zigis* /img/forum/go_quote.gif 
_Any ideas how to get dac soun from you tube and others? I am too lazy to switch outputs every time._

 

If you keep unplugging the DAC from the PC, you will constantly have to make changes. Since most PCs nowdays have a built in sound card, that one likes to make itself the default. If you plan to only use your Bantam, then see if you can disable the onboard one in the BIOS (not device manager or anywhere in Windows). If you disable it at the BIOS, Windows doesn't even think it exists and should default to the BantamDAC. If you can't kill it in the BIOS, you can try leaving the BantamDAC connected to USB all the time and change your default device.

 In XP, go to Control Panel->Sounds and Sudio Devices->Audio Tab. Here, select USB Speakers in the top drop down. Then, on the bottom, check the box for "Use only default devices". This should make anything in Firefox (anything in Windows actually), use the BantamDAC.


----------



## Zigis

Thanks! I made all in control panel and now all work perfect.

 I install ASIO4ALL, reed all Manual, understand close to nothing. First I install in standard configuration and can't find ASIO control panel anywhere. Then I uninstall and install again with off-line sittings. Wen I play Foobar, PCM2702 become "unavailable", all volumes on mixer board still work.
 Anyone can tell step by step How to configure Asio for dirrect output. I am not interested in sound recording, DJ stuff and other, only best possible output sound quality from Foobar and others.
 Thanks.


----------



## linuxworks

when you play, the asio settings are 'locked'.

 what you want to do is stop all audio programs, then launch the offline settings control panel for asio, then select the various entries you want to ENABLE and also be sure to make the right check box in the 'resample to 48k' area (you don't want to resample).

 THEN if you run foobar it should show as active in the offline control asio panel.


----------



## Zigis

I have ASI4ALL v2.9, it look little different, there are no Legend, and speaker icon(disabled in your pic).
 I made all settings, close Off-Line Settings, run Foobar, open again Off-line vhile listening, near PCM2702 is red cross, windows volume still work.

 Is this right?


----------



## Hayduke

From reading the ASIO4ALL website, it looks like you need a special driver perhaps?

 I haven't used it before so I'm unsure. It sounds like Linuxworks is using it with his BantamDAC, so maybe he knows. Is the driver that WinXP installs for the BantamDAC a WDM driver?

 I'm gonna mess with this a bit. If I figure out anything that might help, I'll post again.


----------



## linuxworks

the special driver IS the asio4all pkg.

 what I understand is that you are still talking low-level usb-audio (async) but instead of going thru kmixer you bypass it with help of that asio thing.

 its not really a driver, per se. the driver is built into windows (and freebsd and linux and mac-os) since usb-audio is bog standard 
	

	
	
		
		

		
		
	


	




 asio4all simply bypasses one part of windows.


----------



## Hayduke

grrr had a nice post written up and deleted the tab 
	

	
	
		
		

		
			





 Anyway, I can finally compare the Panny FMs and Nichicon UHNs.
 I have my original cable Bantam with the FMs and a new Bantam with the UHNs.
 Here are pics showing both of them in Foobar and Device Manager.

Attachment 15061
Attachment 15062

 Here is a pic of how they are connected to the amp.

Attachment 15063

 I thought I would just be able to plug in and unplug the cable DAC and switch the output in Foobar, but I think Windows gets confused when I switch. I actually have to disconnect them from the PC's USB. Windows resets the volume for the device to 50% each time. Not quite an ideal A/B test, but it's workable.

 Initial thoughts were that the UHNs have more bass and lacked some top end "sparkle". After switching back and forth for several tracks (Peter Gabriel, Norah Jones, U2, of course, some Pink Floyd, and now REM), I still think the UHNs have more bass, but the treble is pretty similar. The difference isn't dramatic. I think I hear it, but I'll have to listen more. I also want to let the UHNs get some burn in time. The cable DAC has many many hours on it now.

 The new Bantam is getting put inside the case with my SOHA II. The cable DAC will be living at work with the MHSS.

 I promised to let Tom know when I tried them, but it took a lot longer then I thought 
	

	
	
		
		

		
		
	


	




 Of course I look at beezar.com and realize the "new" caps are the UHZs 
	

	
	
		
		

		
		
	


	



 oh well, I'm still gonna report back what I can tell between the Panasonic FM and Nichicon UHNs 
	

	
	
		
		

		
		
	


	




 So I see the difference between the UHZs and the UHNs. So is ripple the most important spec for the power cap? The KW and KZ lines are supposed to be intended for audio use, but the KW has much lower ripple then the UHN or UHZ. I'm thinking I'll order a couple of each next time I place a Mouser order (I've went 3 weeks now. A new record! lol).

 For the KWs, I'll have to get 200uf though. Too bad the KZ only go to 1000uf


----------



## tomb

Thanks for that post, Hayduke!

 We'll probably need Colin to really explain it, but as I understand it, ESR is at least as important as ripple, especially in this application. I think when using capacitors right at the filtering of an AC supply, ripple means everything. However, once in the circuit path where de-coupling is at least as important, then ESR plus ripple rules. Of course, ESR stands for Effective Series Resistance, so it's an indication of "purity" in the capacitor's performance. At least, that's how I understand it.
	

	
	
		
		

		
		
	


	




 Yes, another user pointed out the UHZ's. Sure enough, their rating is superior to _all_ of the caps we've discussed. However, keep in mind that for the UHZ, the performance difference is not that big, but the price difference is. So, it's up to the individual whether the juice of that difference is worth the squeeze.

 One thing I've noted with a new Vista-based PC that I built recently: the irritations you note of switching from one to the other DAC are gone. One can connect multiple BantamDACs and simply select in the software among "Burr-Brown USB Speakers (#)", where "#" is a number that signifies the different DACs. No volume reset occurs.


----------



## Hayduke

Ya, I noticed a bit of a price difference 
	

	
	
		
		

		
		
	


	




 I'm still gonna add a couple into my next order. I want to try the KWs and KZs too. The ripple and ESR #s aren't as good, but Nichicon says they are better for audio. It's an inexpensive experiment. Since I don't have any space concerns with the one built inside the SOHA case, I'll use 2 of the KZs in parallel (They only go up to 1000uf). I used some FWs and KWs in my SOHA where I could get values and package sizes that worked.

 Now I have to get that 3rd Bantam working. The voltages are correct on the regulators, so I hear I may have burned another DAC chip. It takes a little time, but I know I can fix it. I think it's still faster then repopulating all the other SMD parts on a new board 
	

	
	
		
		

		
		
	


	




 The 3rd one will be going into a 2nd MHSS. Someone on that thread gave up on DIY, and sold the parts he had. So I have most of the parts for another one. I'm trying to decide if I should wait for the PCB or do another PTP. I think I'm waiting to be inspired by finding an interesting case to put it in. Per your advice earlier, I'll put some resistors in between them to help protect the DAC.


----------



## joneeboi

Has anyone run into issues with Windows Vista? My BantamDAC worked on my laptop when it ran XP and now it won't run when it has Vista. There are two posts in this thread so far containing the word "vista," three if you count this one. Suggestions?


----------



## Hayduke

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_Has anyone run into issues with Windows Vista? My BantamDAC worked on my laptop when it ran XP and now it won't run when it has Vista. There are two posts in this thread so far containing the word "vista," three if you count this one. Suggestions?_

 

On XP mine shows up as "USB Speakers". On Vista, it shows up as Burr-Brown something or other (Vista box is at work). Never had any issues with Vista myself. Does it still work on the XP machine?


----------



## tomb

The latest Vista builds should have no issue whatsoever. I run the BantamDAC regularly on an OEM-Vista version PC that I built. I've also run it on two different laptops running Vista without any issues at all. For me, Vista says "Burr-Brown Japan PCM2702".

 All that said, my understanding is that early Vista versions had a lot of trouble with USB. Apparently, the USB is handled completely different on Vista vs. XP and earlier MS operating systems. There is a patch out there from Microsoft that fixes this. Sorry, but I don't have a direct link or I'd give it to you.


----------



## mattcalf

Got a friends bantam that I pressured him into buying with me working the other day.

 (A belated) Thanks to all involved!


----------



## joneeboi

I found the link to the hotfix in the Alien DAC thread. I don't have the DAC on me now, but the hotfix seems to have installed properly. I'll report back on how it works.


----------



## joneeboi

It turns out that my BantamDAC no longer works. I have no idea where to go from here because it used to work perfectly fine but now it does not. I stored it in a plastic box for a few months, so maybe the...static(?) got to it. I don't know what to say or do. I'm making a Digikey order next week, so perhaps I will just build another one or two.


----------



## tomb

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_It turns out that my BantamDAC no longer works. I have no idea where to go from here because it used to work perfectly fine but now it does not. I stored it in a plastic box for a few months, so maybe the...static(?) got to it. I don't know what to say or do. I'm making a Digikey order next week, so perhaps I will just build another one or two.




_

 

Sorry to hear it. Try the "Checks and Setup" webpage I made for the BantamDAC website about a month ago. It may help you pin down the problem.

 EDIT: If all of that works, there's one more that you can try: measure the DC volts at the first pad of each output coupling capacitor with ground - should be ~2.2V - 2.4 each. If the PCM chip is fried, one or both of those channels will not read full voltage.


----------



## Hayduke

joneboi

 Use Tom's checks from the website. If the regulators look good, just order an extra DAC chip and replace it. Those 3 parts (regs and IC) are the ones that can fry easily. I've been able to salvage Bantams now with different combos of bad parts.

 The easiest method of removing the DAC for me was to use a heat gun. Remove the TH parts first though or you will melt them 
	

	
	
		
		

		
		
	


	




 The DAC comes off pretty easy. Just heat it and remove with some tweezers.


----------



## joneeboi

I guess I have nothing to lose. I'll make the order anyway, and maybe I'll just throw in another chip. Thanks for the suggestions, fellas.


----------



## Jrossel

I have made a kit to help DIYers build the Bantam DAC. As an option I have soldered DAC chips onto the boards as well. The rest of the surface mount work is less daunting. glassjaraudio.com to order.


----------



## zkool448

Jeff, you're the best. I suck at SMD's exactly the reason why I procrastinate to DIY one


----------



## tomb

Quote:


  Originally Posted by *Jrossel* /img/forum/go_quote.gif 
_I have made a kit to help DIYers build the Bantam DAC. As an option I have soldered DAC chips onto the boards as well. The rest of the surface mount work is less daunting. glassjaraudio.com to order._

 

YAYYY! I didn't want to let the cat out of the bag, but I knew Jeff had been working on this for awhile. Like me, I think he's a one-man-band. It takes awhile of fast pedaling to get this stuff done.
	

	
	
		
		

		
		
	


	




 Thanks, Jeff!!


----------



## adamus

Jeff, if you were a fit bird with lots of money, good tats, a nice car, big house and a great personality i would marry you.


----------



## Marva

Hi, I put together a Bantam but it didnt work, quite obvious, because I had put in a pcm2902 instead of a 2702. I didnt realize it was 2902 until it was too late.
	

	
	
		
		

		
			





 Anyway, I measured about 1.1V over C11 and C13, does that mean the voltage regs are fried? Could anything else have got fried? the clock?

 I've got the 2902 out and the tracks look ok, I guess it should work if I put a 2702 in, right?


----------



## tomb

Quote:


  Originally Posted by *Marva* /img/forum/go_quote.gif 
_Hi, I put together a Bantam but it didnt work, quite obvious, because I had put in a pcm2902 instead of a 2702. I didnt realize it was 2902 until it was too late.
	

	
	
		
		

		
		
	


	




 Anyway, I measured about 1.1V over C11 and C13, does that mean the voltage regs are fried? Could anything else have got fried? the clock?

 I've got the 2902 out and the tracks look ok, I guess it should work if I put a 2702 in, right?_

 

Yep - you need to put in the PCM2702. Unfortunately, it may have fried the regs, too. There's no pin standard for PCM chips like there is for opamps. Using a different PCM chip might've put the regs into a direct short.

 Sorry about that.


----------



## Marva

Thanks for the quick reply
	

	
	
		
		

		
		
	


	




 Should the regs be giving 3.3V across C11 and 4.75V across C13 even without the pcm chip? Just so I can check if I need to order those now.


----------



## tomb

Quote:


  Originally Posted by *Marva* /img/forum/go_quote.gif 
_Thanks for the quick reply
	

	
	
		
		

		
		
	


	




 Should the regs be giving 3.3V across C11 and 4.75V across C13 even without the pcm chip? Just so I can check if I need to order those now._

 

Don't know for sure - it would definitely be useful to remove the PCM chip _now_ and then check the voltages.


----------



## Marva

Well, the regs seem fine, 3.3V and 4.75V without the PCM, so I'll just order a pcm2702 or two.
 A pain they dont sell those chips in Norway(Elfa) though. I'll probably order from Hohodiy.


----------



## TheEKey

Hey guys~!

 I am stuck with getting the V across C13 only 0.7x V.

 From the voltage above, any chance we can know what's wrong with what part?
 1) I thought it's IC2 and I changed a new one. No luck. Same voltage.
 2) Could it be other parts besides the Dac chip itself?
 3) IC1 works fine.
 4) Win XP regonized the chip and no complain while playing. Just no sound out.
 5) LED lights up normal.

 Please help.

 Matt


----------



## tomb

Quote:


  Originally Posted by *TheEKey* /img/forum/go_quote.gif 
_Hey guys~!

 I am stuck with getting the V across C13 only 0.7x V.

 From the voltage above, any chance we can know what's wrong with what part?_

 

Yes - something's wrong with the IC2 circuit. Quote:


 1) I thought it's IC2 and I changed a new one. No luck. Same voltage.
 2) Could it be other parts besides the Dac chip itself? 
 

Yes - it's not the PCM chip. If you only get 0.7V across C13, then there's something wrong with IC2 or the circuitry around it. Quote:


 3) IC1 works fine.
 4) Win XP regonized the chip and no complain while playing. Just no sound out.
 5) LED lights up normal. 
 

All of these are really no indication of anything about IC2. IC2 has nothing to do with IC1. The DAC will definitely not play music, because IC2 supplies the voltage needed to generate an output music signal. The LED is connected directly to the USB 5V buss (through a resistor). Quote:


 
 Please help. 
 

Got any pics of the IC2 area?

 Just a wild thought, but did you get the C16 issue correct? C16 goes on the R8 pad and R7, R8 are not populated if you use a TPS chip for IC2. This is mentioned numerous times on the BantamDAC website and on Beezar. It's also clearly shown in the step-by-step construction instructions on the BantamDAC website in this diagram:





 We've fixed that issue with some silkscreen additions in the new PCB shown here (upper left corner of the Bantam in the photo):


----------



## TheEKey

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yes - something's wrong with the IC2 circuit.Yes - it's not the PCM chip......_

 

I appreciate your sonic speed reply, always.

 Thank god if that's indeed not related to the dac chip because I have just replaced it....

 Please see the pictures. If there's anything not clear and should be seen better, please let me know.
 I've been struggling on my-first-SMD project. So I left a lot of marks on the PCB.

 Anyway, things to mention:

 1) Dac chip legs 13 and 14 are ok, I guess. It's been re-routed to connect to ground. Any potential cross with some other parts? How can I make sure?
 2) I used to get 4.x V from C13. After I replaced the fried Dac, it turns to 0.7x.
 3) Don't worry about the broken red wire of the USB because I accidentally ripped it off when I tried to take these photo. I'm sure they worked before.
 4) Is there anything related to the C12? I have taken it out and put it back bacause of replacement of the Dac.
 5) LED was taken out. It was there when I tested it.



 Thanks,

 Matt


----------



## tomb

Quote:


  Originally Posted by *TheEKey* /img/forum/go_quote.gif 
_I appreciate your sonic speed reply, always.

 Thank god if that's indeed not related to the dac chip because I have just replaced it....

 Please see the pictures. If there's anything not clear and should be seen better, please let me know.
 I've been struggling on my-first-SMD project. So I left a lot of marks on the PCB.

 Anyway, things to mention:

 1) Dac chip legs 13 and 14 are ok, I guess. It's been re-routed to connect to ground. Any potential cross with some other parts? How can I make sure?_

 

DAC legs 13&14 and 15&16 are all tied to ground, so it doesn't matter if those legs are soldered together.

 The standard way to check the DAC connections is through a continuity check with the pads on the board. Using your DMM set to measure resistance, take one probe and place it on a DAC pin where it exits the plastic. Then follow the trace that pin is connected to somewhere else on the PCB and place the other probe at the first pad available that's connected to that trace. You should read zero resistance. Check this to a trace connected to an adjacent pin to verify that the pin your probe is on is not shorted to the adjacent pin - you should read a very high resistance (open circuit). Naturally, do all of this with the power disconnected from the DAC.
  Quote:


 2) I used to get 4.x V from C13. After I replaced the fried Dac, it turns to 0.7x. 
 

That's not good. Now it's making me think it may be the DAC. I suppose if we've got a short working it might draw down the voltage on the IC2 chip. About ~4.75VDC is what you should measure across C13 in normal circumstances. Anything from about 4.5VDC to 4.8VDC is probably OK. 0.7VDC is not. Quote:


 3) Don't worry about the broken red wire of the USB because I accidentally ripped it off when I tried to take these photo. I'm sure they worked before. 
 

Sure you don't have the USB wiring messed up? Those are not standard colors for a USB cable - at all. Quote:


 4) Is there anything related to the C12? I have taken it out and put it back bacause of replacement of the Dac. 
 

Yes, C12 is a very important capacitor. It reinforces the stability of the common voltage reference between the Left and Right signal voltage. Quote:


 5) LED was taken out. It was there when I tested it. 
 

As mentioned previously, this is connected directly to the USB buss voltage. So, it's only an indication that USB is connected, nothing more. Quote:


 

 Thanks,

 Matt 
 

We may need to get cetoole to look at this, but for now I'd concentrate on measuring the pins on the right side (analog side) of the DAC. See if there's short somewhere that's pulling that voltage down from IC2.


----------



## TheEKey

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_DAC legs 13&14 and 15&16 are all tied to ground, so it doesn't matter if those legs are soldered together.

 The standard way to check the DAC..... See if there's short somewhere that's pulling that voltage down from IC2._

 


 1) I have checked all legs. They connect to the pad and closest corresponding parts ok ( 0 resistance check ).

 2) But I have not checked short across legs.... it could be. Since it's way too small, I need to get a better magnifiying glass.....

 3) Please let me know if any specific measurements across any of the parts are necessary to help figure this out.

 4) I will check the USB connection again.

 5) How do I know if C12 works?

 I have just replaced the Dac chip, please this is not the problem. Finger crossed..... 
	

	
	
		
		

		
		
	


	




 Matt


----------



## Hayduke

Quote:


  Originally Posted by *TheEKey* /img/forum/go_quote.gif 
_1) I have checked all legs. They connect to the pad and closest corresponding parts ok ( 0 resistance check ).

 2) But I have not checked short across legs.... it could be. Since it's way too small, I need to get a better magnifiying glass.....

 3) Please let me know if any specific measurements across any of the parts are necessary to help figure this out.

 4) I will check the USB connection again.

 5) How do I know if C12 works?

 I have just replaced the Dac chip, please this is not the problem. Finger crossed..... 
	

	
	
		
		

		
		
	


	




 Matt_

 

SMD inspection is tough. I have a decent magnifier, but I still had trouble seeing those legs as well as I wanted. I did figure out a great solution though! I used my camera to take some close up/macro shots of the solder joints. Then I could view them on my monitor. This may not be an option for you depending on if you have the equipment.

 I used a Nikon D80 and the 18-55VR kit lens. I was also using Nikon's software that lets you connect the camera to the PC via USB and see the pics live on the screen. Sorry, I can't recall the name of it. I installed Windows 7 and haven't had a need to reinstall it yet 
	

	
	
		
		

		
		
	


	




 It worked great for inspecting my solder joints though!


----------



## tomb

Quote:


  Originally Posted by *TheEKey* /img/forum/go_quote.gif 
_1) I have checked all legs. They connect to the pad and closest corresponding parts ok ( 0 resistance check )._

 

That's good. Quote:


 
 2) But I have not checked short across legs.... it could be. Since it's way too small, I need to get a better magnifiying glass..... 
 

This should not require any additional equipment beyond what you used to check #1. Compare resistance to adjacent traces that are connected to adjacent pins. if you get zero resistance for any of those, then you have a problem. Just focus on the right side of the PCM chip - the left side is working OK if the IC1 voltage is right and the PC recognizes the USB connection. Quote:


 
 3) Please let me know if any specific measurements across any of the parts are necessary to help figure this out. 
 

See the above, but you've already done the essential measurements. I hate to say it, but if you don't get the proper voltage at IC2 and we are confident that IC2 is OK, then the issue is with the DAC. Hayduke is correct - there's not much to do beyond that except to keep checking for shorted pins. I sort of doubt the IC2 chip - your soldering work looks OK in that area. That again would imply the PCM chip, but that USB wiring has me worried, too. Quote:


 
 4) I will check the USB connection again. 
 

Good idea. Removing suspicions elsewhere is useful in narrowing down the problem. Quote:


 
 5) How do I know if C12 works? 
 

An easy way to check a capacitor is to make a resistance reading between the two leads. If the resistance gradually reduces as you are holding the probes to the leads, that's an indication that the capacitor is charging up from the small amount of voltage the DMM uses to check resistance. If your soldered connections are OK to the capacitor, I doubt that there's any issue with the cap. You pretty much have to blow one to completely ruin a cap. I don't know what the gel cap like C12 does when blown, but other electrolytics will pop their tops and start oozing liquid - it's pretty easy to tell.
	

	
	
		
		

		
		
	


	




 Quote:


 
 I have just replaced the Dac chip, please this is not the problem. Finger crossed..... 
	

	
	
		
		

		
		
	


	




 Matt 
 

Yes, I hope you are right.


----------



## TheEKey

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_SMD inspection is tough. I have a decent magnifier, but I still had trouble seeing those legs as well as ...... inspecting my solder joints though!_

 

Thanks for the tip, Hayduke.

 You reminded me of my stolen Canon Rebel :...(

 I am actually trying to use this method too. The only difference is that I'm using point-and-shoot camera, which sucks at macro mode under medium to low light.....

 Anyhow, let me use a torch to boost the light


----------



## TheEKey

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_That's good.This should not require any additional equipment beyond what you used to check #1. Compare ..... I hope you are right.
	

	
	
		
		

		
		
	


	


_

 

I actually fried my first Dac chip during the 0-resistance-test between neighboring legs...... There was smoke (little bit) came out when I crossed two of them which I don't recall.

 Anyhow, I'll try on the right side first, wish me luck...

 Matt


----------



## tomb

Quote:


  Originally Posted by *TheEKey* /img/forum/go_quote.gif 
_I actually fried my first Dac chip during the 0-resistance-test between neighboring legs...... There was smoke (little bit) came out when I crossed two of them which I don't recall.

 Anyhow, I'll try on the right side first, wish me luck...

 Matt_

 

*Hey! Don't do this with it plugged in!!!*

 The only time you should be making a measurement with the DAC plugged in is for voltage.


----------



## TheEKey

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_*Hey! Don't do this with it plugged in!!!*

 The only time you should be making a measurement with the DAC plugged in is for voltage.
	

	
	
		
		

		
		
	


	


_

 

I won't, don't worry. 
	

	
	
		
		

		
		
	


	




 I love my life~!

 Let me check to see if there should be any short circuit first.

 Matt


----------



## TheEKey

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_*Hey! Don't do this with it plugged in!!!*

 The only time you should be making a measurement with the DAC plugged in is for voltage.
	

	
	
		
		

		
		
	


	


_

 







 I haven't found any short circuit between any of the legs.....

 Any clue?

 Matt


----------



## tomb

Quote:


  Originally Posted by *TheEKey* /img/forum/go_quote.gif 
_





 I haven't found any short circuit between any of the legs.....

 Any clue?

 Matt_

 

If that's the case, then I'd guess I'd try replacing the TPS chip, first (even though you already did that). Any chance that one got mixed up with the TPS79333? If you have one of those in there the readings might actually make a bit more sense.

 It could still be an internal problem with the DAC I suppose, but in lieu of a specific measurement, we should go with what we know: the voltage is not sufficient from the IC2 area. Sorry I can't be more helpful, but SMD troubleshooting is not the easiest thing ...


----------



## Hayduke

Tom, I know you've cooked a couple Bantams. I think at least one was with a MHSS. Have you ever had one lose one channel?

 The one I've been using at work with my MHSS is missing a channel today 
	

	
	
		
		

		
		
	


	



 It was fine yesterday. I did my normal process of turning the amp off at the end of the day and then unplugging the DAC before powering the amp up in the morning. It's worked great for months.

 I'll take it home today, but I'm not sure I'll have time to troubleshoot it tonight. If I only lost one channel, is that the DAC chip?

 If I have to swap the DAC chip again, I'm gonna have to figure out some way to protect it. These things seems a little delicate.


----------



## tomb

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_Tom, I know you've cooked a couple Bantams. I think at least one was with a MHSS. Have you ever had one lose one channel?

 The one I've been using at work with my MHSS is missing a channel today 
	

	
	
		
		

		
		
	


	



 It was fine yesterday. I did my normal process of turning the amp off at the end of the day and then unplugging the DAC before powering the amp up in the morning. It's worked great for months.

 I'll take it home today, but I'm not sure I'll have time to troubleshoot it tonight. If I only lost one channel, is that the DAC chip?

 If I have to swap the DAC chip again, I'm gonna have to figure out some way to protect it. These things seems a little delicate._

 

The Bantam I most recently fried with one of the production SSMH's only lost the left channel. That's the extent of the damage, but it might as well be "fried."

 Again, what we've found is that the issue is intermittent and probably caused by the power supply's ground floating. This can cause a momentary offset in the ground between the Bantam's ground (PCB through the PC's USB) and the grounded case of the SSMH.

 My thoughts now are that to use a Bantam or Alien with an SSMH that you must ensure that the grounds are always in contact, but who knows if that will cure it? I once thought having the output coupling caps fully charged on the Bantam should be enough, but if the offset voltage is through the ground, then the caps will offer no protection.

 It's a sad fact that the SSMH works this way, but it does. No other amp that I'm aware of has caused any issues with the Bantam or Alien. I use them constantly on MAXes, MiniMAXes, PIMETA's, etc. But I've fried both types of DACs using the SSMH.


----------



## Hayduke

Thanks Tom.

 I'll see if I can figure out how to resolve the grounding issue.

 So you think it's the DAC chip that's messed up, right?
 If so, I'll order another and swap it out.

 You've reassured me that the BantamDAC I'm putting inside my SOHA II case will not die.


----------



## tomb

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_Thanks Tom.

 I'll see if I can figure out how to resolve the grounding issue.

 So you think it's the DAC chip that's messed up, right?
 If so, I'll order another and swap it out.

 You've reassured me that the BantamDAC I'm putting inside my SOHA II case will not die._

 

1. Yes, I think the PCM chip is messed up.

 2. Let me reiterate: there has never been an issue with a BantamDAC using any other amp.

 BTW, this is what will be shipping very soon:


----------



## Forte

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_BTW, this is what will be shipping very soon:



_

 

Any changes to the board apart from the new colour?


----------



## tomb

Quote:


  Originally Posted by *Forte* /img/forum/go_quote.gif 
_Any changes to the board apart from the new colour?_

 

Yes.
 The silkscreen has been improved:
C16 has been labeled in the primary TPS position, and
A "+" has been indicated on the proper pad for the LED.
Also, this is subtle, but the grounded pins at 13, 14, 15 and 16 at the bottom of the PCM chip have been re-designed with a form of "thermal reliefs", so they should be slightly easier to solder than on V1.0.

 Unfortunately, we ran these boards before Joneeboi discovered the ground error around C3. So, the right-hand pad on C3 should still be solder-connected to the adjacent ground pad area - as shown here:





 EDIT: Dang, dang - it's C3 ... C3 ... C3!! You'd think I could get that right.


----------



## Hayduke

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_1. Yes, I think the PCM chip is messed up.

 2. Let me reiterate: there has never been an issue with a BantamDAC using any other amp._

 

#2 makes me very happy 
	

	
	
		
		

		
		
	


	




 I really like the sound of these little DACs. I built one inside my SOHA II case, so it's nice to know that it is unlikely the amp will harm it.

 Thanks again for helping us DIYers Tom


----------



## Forte

Having trouble with my Bantam build.

 On initial plug-in no LED or music, LED was in backwards and one leg of the IC2 wasn't soldered properly which were both easy to fix. Worked fine for a few hours but after changing Bantam to another amp (built as a cableDAC) it suddenly developed a loud static type noise with the music only very faint in the background. Switched back to the first amp and now no music or static at all?

 Will make a few checks with my DMM when I get a chance later, guessing the IC2 may still be the problem or the soldering of the RCA's.

 It still shows in windows as working, does this mean the DAC chip should be okay?


----------



## tomb

Quote:


  Originally Posted by *Forte* /img/forum/go_quote.gif 
_Having trouble with my Bantam build.

 On initial plug-in no LED or music, LED was in backwards and one leg of the IC2 wasn't soldered properly which were both easy to fix. Worked fine for a few hours but after changing Bantam to another amp (built as a cableDAC) it suddenly developed a loud static type noise with the music only very faint in the background. Switched back to the first amp and now no music or static at all?

 Will make a few checks with my DMM when I get a chance later, guessing the IC2 may still be the problem or the soldering of the RCA's.

 It still shows in windows as working, does this mean the DAC chip should be okay?_

 

Check your Ground connections - both on the USB Cable connections to the pads and to the output connections at OL and OR. Lack of a proper ground connection at the signal outputs can cause a bunch of horrible noise, even though the music might be playing in the background. It's possible the connections loosened up after plugging/unplugging a few times.


----------



## Forte

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Check your Ground connections - both on the USB Cable connections to the pads and to the output connections at OL and OR. Lack of a proper ground connection at the signal outputs can cause a bunch of horrible noise, even though the music might be playing in the background. It's possible the connections loosened up after plugging/unplugging a few times._

 

Thanks, Those checked out okay, the voltage reading at C13 doesn't again! This time I will remove IC2 completely and resolder all pins as there may be more than one bad solder joint, otherwise I have got a spare if it is bad.


----------



## tomb

Quote:


  Originally Posted by *Forte* /img/forum/go_quote.gif 
_Thanks, Those checked out okay, the voltage reading at C13 doesn't again! This time I will remove IC2 completely and resolder all pins as there may be more than one bad solder joint, otherwise I have got a spare if it is bad._

 

Well, at least your measuring is finding stuff. That's a good sign.


----------



## Forte

Fixed, Working fine now. Dodgy soldering on IC2 again, this time I removed it completely from the board(and R8 to make room) and resoldered it from scratch. Don't know why but found the two regulators harder to solder than the DAC.


----------



## kuroguy

You might want to add a couple of really tight zip ties around the input wire and the output wire to prevent pulling the wires out of the case.


----------



## tomb

Quote:


  Originally Posted by *Forte* /img/forum/go_quote.gif 
_





 Fixed, Working fine now. Dodgy soldering on IC2 again, this time I removed it completely from the board(and R8 to make room) and resoldered it from scratch. Don't know why but found the two regulators harder to solder than the DAC.












_

 

Very nice!!


----------



## Forte

Quote:


  Originally Posted by *kuroguy* /img/forum/go_quote.gif 
_You might want to add a couple of really tight zip ties around the input wire and the output wire to prevent pulling the wires out of the case._

 

No need, the grommets hold the wires very tightly.


----------



## individual6891

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_BTW, this is what will be shipping very soon:



_

 

Just wondering if the Bantam will ever be modified to run the PCM270*4* chip? Seems like TI are going to discontinue the PCM2702 soon as they're not recommending it (USB Audio - USB DACs - PCM2702 - TI.com)


----------



## tomb

Quote:


  Originally Posted by *individual6891* /img/forum/go_quote.gif 
_Just wondering if the Bantam will ever be modified to run the PCM270*4* chip? Seems like TI are going to discontinue the PCM2702 soon as they're not recommending it (USB Audio - USB DACs - PCM2702 - TI.com)_

 

We've planned for that eventuality, but there are still _several hundred_ at both DigiKey and Mouser:

 DigiKey - 693
 Mouser - 570
 Newark - 37
 Farnell - 46
 Avnet - 25
 WPI - 285

 I just confirmed the DigiKey, Mouser, and Newark stock directly on their site as well. There are plenty of PCM chips left for us for quite awhile.


----------



## bmwpowere36m3

I'm going thru the BOM, for C8 is lists a _Ceramic 22uf 6.3V X5R 10%_.... but the Digi-Key P/N is for a *10uf 10V X7R 10%*. Is this okay, or should I look for a 22uf one?


----------



## tomb

Quote:


  Originally Posted by *bmwpowere36m3* /img/forum/go_quote.gif 
_I'm going thru the BOM, for C8 is lists a Ceramic 22uf 6.3V X5R 10%.... but the Digi-Key P/N is for a *10uf 10V X7R 10%*. Is this okay, or should I look for a 22uf one?_

 

It's OK. The 22uf for C8 is marginally better, but the 10uf at DigiKey will work, too. DigiKey doesn't have the 22uf in that size and type.


----------



## TheEKey

Hi Guys,

 After a long time struggle on my first bantam dac, I decided to give it up....

 But I assembled 2 later and they are all working.

 Question in short, elna silmic II is signed, right?
 For using as CL and CR, how should I put it? Negative sign to output audio? Please advise.

 Matt


----------



## tomb

Quote:


  Originally Posted by *TheEKey* /img/forum/go_quote.gif 
_Hi Guys,

 After a long time struggle on my first bantam dac, I decided to give it up....

 But I assembled 2 later and they are all working.

 Question in short, elna silmic II is signed, right?
 For using as CL and CR, how should I put it? Negative sign to output audio? Please advise.

 Matt_

 

Actually, if you follow convention - Positive should go toward the DAC, Negative to OL and OR. This is because the caps are grounded through R5 and R6 at OL and OR and Ground is Negative on the PCB.


----------



## Gross

*sigh* today I revisited a Bantam that I could not get up and running a few months ago. Reflowed everything, and it all looks great. 4.77v and 3.29v respectivly. I didn't really want to remove the 2702, especially since I just replaced all the through hole stuff. Oh well. Thanks for listening.


----------



## joneeboi

Been there, man. Actually, I'm there right now. 
	

	
	
		
		

		
		
	


	




 I've removed a 2702 before, and it tore off a lot of the traces. I just want to build a whole bunch of them just for the experience. I've got two ready to be built right now, so we'll see what steadiness my hands will have. =T


----------



## Gross

Yeah, luckily I have the parts for 2 more, I will need one ready to pair with your proto Carrie next weekend


----------



## rds

Christmas eve 2008, I'm frantically putting together my last gift - a bantam cable DAC for my brother.

 I carefully put in each component doubling checking everything as I go along. Then I painstakingly fit the pcb into the little cable DAC case. Plug it in ...and... nothing! I Take it out check every part. Look for solder bridges. Everything looks fine 
	

	
	
		
		

		
		
	


	




 About it to be picked up for a Christmas eve party I toss the DAC in a box and never looked at it again. Until today.

 I happened across a note on the Bantam DAC site that says pin 4 needs to be connected (a pcb error). Well I found that box, checked my DAC and sure enough pin 4 has the pcb error.
 Well looks like it'll be Christmas in July 
	

	
	
		
		

		
		
	


	




 Fyi, I did have other gifts for my brother so I wasn't empty handed. But I did promise I would get that DAC built one day.


----------



## Forte

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_
 I happened across a note on the Bantam DAC site that says pin 4 needs to be connected (a pcb error). Well I found that box, checked my DAC and sure enough pin 4 has the pcb error.
 Well looks like it'll be Christmas in July 
	

	
	
		
		

		
		
	


	


_

 

This may not be the cause of your Bantam not working, according to tomb's post here http://www.head-fi.org/forums/5447695-post410.html this should not stop it from working. When I built my cableDAC I realised I had not done this step on my first Bantam but it had still been working fine for 3 months without this connection, went back and fixed it though, easy enough to do.

 Worth going over it again though with a fresh mind, you my find a simple mistake you missed the first time round.


----------



## TheEKey

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Actually, if you follow convention - Positive should go toward the DAC, Negative to OL and OR. This is because the caps are grounded through R5 and R6 at OL and OR and Ground is Negative on the PCB._

 


 It works (produces sound) in both way.
 Was not sure but now got it, Thanks Tomb.

 Matt


----------



## TheEKey

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_Been there, man. Actually, I'm there right now. 
	

	
	
		
		

		
			





 I've removed a 2702 before, and it tore off a lot of the traces. I just want to build a whole bunch of them just for the experience. I've got two ready to be built right now, so we'll see what steadiness my hands will have. =T_

 

 Quote:


  Originally Posted by *gross* /img/forum/go_quote.gif 
_Yeah, luckily I have the parts for 2 more, I will need one ready to pair with your proto Carrie next weekend_

 

Been there x 2 , guys.... 

 Check my attachment. Obviously one of them is not working and that is my first built.

 My experience on the first one was that I got the voltages across C11 and C13 right. Somehow the DAC chip was fired (probably during checking). I replaced the chip and still not working.....
 Did you use braid? My best guess was that the juice (leftover?) flowing out during desoldering with braid could cause blockages on some other soldering points (not mentioned the heat we applied during desoldering on this small board could actually "break" some other previously weakly soldered joints..)
 That's how I left so much mess on the first board and I gave it up......
 (Just like first love usually ends not so good.... 
	

	
	
		
		

		
		
	


	




 Hopefully yours is not as poorly done as mine. So there's still a hope.
 But I gave this board up and decided to start brand new. So I got other 2 working boards. I felt the work was much smoother than that on the first board. 
 I hope that will be how you feel on working on the latter, too.

 Cheer~!

 Matt


----------



## Gross

Just threw a new one together in record time. Worked perfectly first time. Thought I would remove the 2702 on my bad one, and I ruined one of the traces (pin 8, vBUS)to the point where I don't think I can use the board over again. Looks like I will only build 4 out of the 5 that I planned on.


----------



## joneeboi

Hey all,

 I got my BantamDAC finally up and running today. Huzzah!

 I do have an issue though, and I have to wonder if I'm the first one to have this issue. The PCM connects fine on my Vista, but every few minutes, a certain music-producer turns to static. It happened in my iTunes, my foobar, a song in imeem. Even as I type this post, it refuses to quit. If I pause or close the application, the static goes away. If I pause foobar long enough, I can start it playing again as if there were nothing wrong.

 That all tells me that it's an issue on the software side, but I don't know why it's happening. I disabled my laptop speakers, and it still happened. I haven't been able to find a page with settings that will keep my ASIO from messing up. I've been messing around with it for the past few hours, and no dice so far. I installed the Vista hotfix, but I don't really know what effect its had. Has anyone else had issues like this?


----------



## Gross

Actually, I was having the same issue this weekend, but I have not really used the computer much since I reloaded it, so I didn't know what to blame. I jumped around between 1 Bantam and 2 AlienDACs and eventually they all did the same thing. Sometimes the song would turn to loud hiss, sometimes there was just a really noisy background. I would unplug the DAC and plug it back in, and it would work fine. It seemed to ussually kick in around 10-15 minutes.

 I recently reloaded the Machine with Vista 64-bit, my only computer running 64-bit so far. I thought that may be related. I have used other Bantams on my Vista 32-Bit machines without any of those issues.


----------



## tomb

I know this is blasphemy, but I don't use ASIO4All. There are many instances where it just doesn't work.


----------



## joneeboi

So how do you have your foobar configured?


----------



## tomb

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_So how do you have your foobar configured?_

 

It's not really "configured." I simply accept the defaults and then select the output device desired. I guess that means it goes through the OS, but so be it. The worst I've ever had happen is that music will skip for an instant if the processor/hard drive is taxed, which doesn't happen too often on most PC's these days - maybe when I call up a large AutoCAD file or access a website with lots of pics. Even then, the drop out is only a split second and recovery is instantaneous with no ill effects.

 Like I said, I know that's "blasphemy," but I've never had an issue doing this. I've got work laptops, an office PC and a couple of home PC's - each of which may run Foobar under different conditions and different operating systems. I use portable USB drives to contain all my music and simply connect one to whichever computer I happen to be using at the time. Foobar is installed in the "portable mode," so it resides on the USB drive. For instance, on my office PC, they don't even give me the capability to load a driver such as ASIO4All, yet the USB drive and a BantamDAC are instantly recognized.

 Anyway, it greatly simplifies things and sounds great to me.
	

	
	
		
		

		
		
	


	




 P.S. I have tried the ASIO4All driver several times in the past - I can't tell the difference with it anyway.


----------



## joneeboi

Okay, so I tried getting rid of ASIO4ALL, foobar, and I replaced usbaudio.sys in the System32 folder with one from an XP machine. None of those things are fixing my noise issue. The Bantam shows up fine in my Control Panel -> Sounds, but this weird noise only comes around when I'm listening to music or playing a video. I'll just be listening to music, and then nothing but static comes through from a certain program, be it foobar, VLC or a video in Firefox. I can see that my situation is fairly unique because there's nothing in this thread or Google that mirrors my experience. I listened to the thing all day on an XP machine, and it didn't make a fuss. There were two hotfixes for the USB audio in Vista Service Pack 1, but I know this doesn't require a new one because people are currently using Bantams on Vistas. I don't get it. Think Service Pack 2 will fix it? It's only just a few days out the door.


----------



## tomb

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_Okay, so I tried getting rid of ASIO4ALL, foobar, and I replaced usbaudio.sys in the System32 folder with one from an XP machine. None of those things are fixing my noise issue. The Bantam shows up fine in my Control Panel -> Sounds, but this weird noise only comes around when I'm listening to music or playing a video. I'll just be listening to music, and then nothing but static comes through from a certain program, be it foobar, VLC or a video in Firefox. I can see that my situation is fairly unique because there's nothing in this thread or Google that mirrors my experience. I listened to the thing all day on an XP machine, and it didn't make a fuss. There were two hotfixes for the USB audio in Vista Service Pack 1, but I know this doesn't require a new one because people are currently using Bantams on Vistas. I don't get it. Think Service Pack 2 will fix it? It's only just a few days out the door._

 

There are some versions of Vista that won't even read a BantamDAC. That's why the hot fix was needed. If you've been able to operate it on an XP machine without any issues, then it has to be the copy of Vista.

 As an aside, though - it's interesting that the ASIO4All made no difference with your problem on the Vista machine. It sort of contradicts what ASIO4All is supposed to do, but as stated before - that's been my experience. Most likely, someone needs to code a special version for Vista but I bet that'll be a long time coming.


----------



## joneeboi

It seems multiple sources are telling me it's just my copy of Vista. I just updated to SP2, but it's still happening. I reinstalled foobar and ASIO4ALL, and it's still happening. I've found a few other threads where people describe a metallic distortion noise; one referred to it as the sound of a thousand demons screaming. Most threads involve either installing hotfixes and drivers or getting replacements. I have searched high and low. Do I have to flip my OS just to get my DAC to work? Bah!


----------



## Gross

I am running Vista Ultimate x64 and I just applied SP2 and I still have the problem. random bursts of static and then about 6 songs in it is pure static. The sound seems to jump from left to right sometimes too. These same DACs are fine on my Vista x32 boxes.


----------



## tomb

Maybe it's just Vista 64, then? I have a Vista Business (32bit) PC and a Vista Business (32bit) laptop that have no issues.

 Windows Vista Business is listed as compatible in Texas Instruments' "Updated Operating Environments for PCM270X, PCM290X Applications". This document is dated 19 Oct 2007, but I'm wondering if the implication is that Windows Vista in other forms is _not_ compatible. Seems Vista Home would've been listed if it was - it was available at the same time that Vista Business was, if not before. Note that XP is listed as Business/Home whereas Vista is not.


----------



## Forte

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Maybe it's just Vista 64, then?_

 


 I'm running Vista Home Premium 64-bit and both my Bantams work perfectly.
 (Before and after installing SP2)


----------



## Gross

Quote:


  Originally Posted by *Forte* /img/forum/go_quote.gif 
_I'm running Vista Home Premium 64-bit and both my Bantams work perfectly.
 (Before and after installing SP2)_

 

So the only difference 'tween you and I is Home Premium 64 vs Ultimate Edition 64. Strange. And just to make sure, I used my Bantam/Carrie on my Vista Buisness 32-bit last night for hours with no problems.


----------



## joneeboi

I have an AMD Athlon X2 Dual-Core QL-60 processor on Vista Home Premium. Think the dual processor on Vista could mess it up?


----------



## Forte

Quote:


  Originally Posted by *Gross* /img/forum/go_quote.gif 
_So the only difference 'tween you and I is Home Premium 64 vs Ultimate Edition 64. Strange. And just to make sure, I used my Bantam/Carrie on my Vista Buisness 32-bit last night for hours with no problems._

 

One other difference I can think of "Carrie", and since this is *joneeboi*'s proto/project it is one thing you both have in common. 

 I had a static noise with my second build that was caused by a bad solder joint on IC2, is it possible that by taking power from the Bantam board to power Carrie that there is not enough left for the DAC to function correctly?


----------



## joneeboi

No, it's not. There are 2.5W available from USB (more if you stray from spec), and the PCM uses less than a quarter watt at max. The chip in Carrie only delivers up to 1W (Carrie should draw less than half that), so there's no way there's a lack of power. Besides, both Gross and I have successfully hooked up the combos for several hours to different computers with different OSs without any problems.


----------



## lynxkcg

I just got my kit in today from glassjaraudio, and I'm having trouble telling which tps chip is which. One has PHUI with dots above and below the P. The other says PHJI with dots above and below the H and I and a single dot above the J. The PHJI had what I think is a 4 marked on it's little section of reel, but the PHUI just had a smudge. 
 Thanks for the help, I don't wanna fry this one like I did my alien.


----------



## tomb

Quote:


  Originally Posted by *lynxkcg* /img/forum/go_quote.gif 
_I just got my kit in today from glassjaraudio, and I'm having trouble telling which tps chip is which. One has PHUI with dots above and below the P. The other says PHJI with dots above and below the H and I and a single dot above the J. The PHJI had what I think is a 4 marked on it's little section of reel, but the PHUI just had a smudge. 
 Thanks for the help, I don't wanna fry this one like I did my alien._

 

You need to contact Jeff Rossell on this. Package labeling often differs according to the production batch. There's also nothing in the TI datasheet that indicates a labeling standard. So, it all depends on his own batches that he's ordered, I'm afraid. Hopefully, he'll package them separately in the future. Unless I'm missing something obvious, this may continue to be an issue. (My eyes aren't good enough to read the labeling anyway - I'd be up the creek if I got them mixed in the same bag.
	

	
	
		
		

		
			





 )

 I have no doubt that Jeff will clear things up for you, though.


----------



## Gross

Quote:


  Originally Posted by *Forte* /img/forum/go_quote.gif 
_One other difference I can think of "Carrie", and since this is *joneeboi*'s proto/project it is one thing you both have in common. 

 I had a static noise with my second build that was caused by a bad solder joint on IC2, is it possible that by taking power from the Bantam board to power Carrie that there is not enough left for the DAC to function correctly?_

 

No, I also have the same problem with my 2 AlienDACs. They all work fine on other machines. I had just reloaded this PC and noticed the problem while building my Bantam and Carrie.


----------



## tomb

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_No, it's not. There are 2.5W available from USB (more if you stray from spec), and the PCM uses less than a quarter watt at max. The chip in Carrie only delivers up to 1W (Carrie should draw less than half that), so there's no way there's a lack of power. Besides, both Gross and I have successfully hooked up the combos for several hours to different computers with different OSs without any problems._

 

I'd have to agree. The fact that TI pointedly lists only "Vista-Business" while listing several versions of XP, etc., seems indicative. IOW, other versions of Vista may or may not work and are at the user's risk.
	

	
	
		
		

		
		
	


	




 I thought perhaps this might be one of the reasons for the PCM2702 becoming a NRND, but no - the OS compatibility sheet is valid for PCM270X and PCM290X, which includes all the potential future replacements for PCM2702 as well.

 Hopefully, some enterprising Head-Fier will test the Bantam or Alien on Windows 7 and let us know how that does.


----------



## onyu

Hi, I have the same static noise problem, but I don't even have Vista on my PC. I have Windows XP sp3. I run foobar and asio4all, too.


----------



## mugdecoffee

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Hopefully, some enterprising Head-Fier will test the Bantam or Alien on Windows 7 and let us know how that does.
	

	
	
		
		

		
		
	


	


_

 

Works without a hitch! I'm running Windows 7 32bit. Got ASIO working in foobar too without any problems.


----------



## Hayduke

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I'd have to agree. The fact that TI pointedly lists only "Vista-Business" while listing several versions of XP, etc., seems indicative. IOW, other versions of Vista may or may not work and are at the user's risk.
	

	
	
		
		

		
		
	


	




 I thought perhaps this might be one of the reasons for the PCM2702 becoming a NRND, but no - the OS compatibility sheet is valid for PCM270X and PCM290X, which includes all the potential future replacements for PCM2702 as well.

 Hopefully, some enterprising Head-Fier will test the Bantam or Alien on Windows 7 and let us know how that does.
	

	
	
		
		

		
		
	


	


_

 


 Systems that I can confirm Bantams work well on:
 XP SP2
 Vista Business 32 bit
 Vista Business 32 bit SP1
 Windows 7 32 bit
 Windows 7 64 bit


----------



## tomb

Excellent! I've updated the BantamDAC website to include Windows 7 32 and 64 bit. Thanks, guys!

 I noticed that I had stuck with the TI recommendations on the Bantam site and only had Vista Business listed for Vista. Seems weird, but maybe that's one of the reasons Vista had so many complaints.


----------



## joneeboi

Mystery solved, eh? Good stuff. I should be able to get access to Windows 7 through school, so that shouldn't be too much of a problem come September. Thanks for helping out, everyone.


----------



## mugdecoffee

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_Mystery solved, eh? Good stuff. I should be able to get access to Windows 7 through school, so that shouldn't be too much of a problem come September. Thanks for helping out, everyone._

 

Unless you've only got dialup and need your school for faster internet, Windows 7 is a free public download.


----------



## onyu

Good news, got the noise problem solved. Bantam straight in usb from laptop gives a noise after a few minutes, Bantam in usbhub plays perfect. On another laptop it works perfect.


----------



## tomb

Quote:


  Originally Posted by *onyu* /img/forum/go_quote.gif 
_Good news, got the noise problem solved. Bantam straight in usb from laptop gives a noise after a few minutes, Bantam in usbhub plays perfect. On another laptop it works perfect._

 

That's great! So maybe your one laptop has an issue with the connector, perhaps?


----------



## joneeboi

Yeah, you can probably tell I'm out of the loop. 
	

	
	
		
		

		
			





 I get some free software from Microsoft through the Electrical Engineering department at the U of A because we're part of the MSDN Academic Alliance. I was thinking of getting the full version once I got back to school, but I realized that it doesn't even come out until October.

 But alas, I installed the release candidate of Windows 7 32-bit. You're all probably annoyed of me bothering all the time, but the PCM still isn't working for me. u_u"" Hayduke, did you have to do anything more than plug and play?


----------



## tomb

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_Yeah, you can probably tell I'm out of the loop. 
	

	
	
		
		

		
		
	


	




 I get some free software from Microsoft through the Electrical Engineering department at the U of A because we're part of the MSDN Academic Alliance. I was thinking of getting the full version once I got back to school, but I realized that it doesn't even come out until October.

 But alas, I installed the release candidate of Windows 7 32-bit. You're all probably annoyed of me bothering all the time, but the PCM still isn't working for me. u_u"" Hayduke, did you have to do anything more than plug and play?_

 

OK, this is getting a bit annoying with your PC.
	

	
	
		
		

		
		
	


	







 I'm wondering if it's something in the hardware/motherboard at this point?


----------



## lynxkcg

I got mine up and running great. Had a little trouble with a flipped LED, then I assumed the whole board didn't work. Swapped in a new light, and realized it all worked. Flux pens are worth their weight in platinum. Listening to the improvement it's made is making my wallet nervous in fear of what's next.


----------



## tomb

Quote:


  Originally Posted by *lynxkcg* /img/forum/go_quote.gif 
_I got mine up and running great. Had a little trouble with a flipped LED, then I assumed the whole board didn't work. Swapped in a new light, and realized it all worked. Flux pens are worth their weight in platinum. Listening to the improvement it's made is making my wallet nervous in fear of what's next._

 

Glad to hear it! Yes, a flux pen works wonders with SMD soldering.


----------



## joneeboi

Okay, so I think this one solves the problem.

USB port may stop working after you remove or insert a USB device

 I disabled "USB Selective Suspend" in my power management options, but checking the registry showed that it didn't...register(?). I manually disabled "Selective Suspend" in the registry and restarted the computer. It messed up once after listening for close to an hour, but I haven't been able to replicate the problem in the following half hour. The problem was that the music cut out, not that static was produced. I will do some more stress testing later on, but so far so good. Gross, is the PCM messing up on your laptop?


----------



## Gross

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_Okay, so I think this one solves the problem.

USB port may stop working after you remove or insert a USB device

 I disabled "USB Selective Suspend" in my power management options, but checking the registry showed that it didn't...register(?). I manually disabled "Selective Suspend" in the registry and restarted the computer. It messed up once after listening for close to an hour, but I haven't been able to replicate the problem in the following half hour. The problem was that the music cut out, not that static was produced. I will do some more stress testing later on, but so far so good. Gross, is the PCM messing up on your laptop?_

 

Laptop works great, actually, I used my Carrie for about 5 hours off of my laptop in the work van today. Very happy with it. 

 My issue is with one of my PCs at home. Like you, I also uppped it to Windows 7, 64 bit, and regrettably I still have the issue. I did a clean install, so I would have to say it is a hardware type thing. I checked in the bios for any sort of USB settings (legacy, power, etc) and at this point have not been able to resolve it. When using it the left and right tend to jump around and then eventually I just get static. I tried multiple ports on the machine hoping maybe it was just 1 usb host controller, but no such luck. 

 I would be curious if I used a different USB controller card (PCI or whatever) but I don't have one sitting around to try. I havn't spent a whole lot of time working on it since now I have just been bringing my laptop to my other PC when I want music. I know, I know. Sad and lazy


----------



## Hayduke

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_I installed the release candidate of Windows 7 32-bit. You're all probably annoyed of me bothering all the time, but the PCM still isn't working for me. u_u"" Hayduke, did you have to do anything more than plug and play?_

 

I didn't do anything other then plug it in on either box. The 64 bit build 7100 (RC1) is at work. Here at home, I have a 32 bit build 7077 and the Bantams work fine. I only have one working right now and I'm listening to it on my 32 bit Windows 7 right now (The Cranberries are pretty great hehe).

 I never had any problems with the 64 bit Windows 7 either, but I haven't been using a Bantam there since my MHSS killed one a few weeks ago 
	

	
	
		
		

		
		
	


	




 I'm planning to rebuild it, but I've been way to busy lately.


----------



## joneeboi

Quote:


  Originally Posted by *Gross* /img/forum/go_quote.gif 
_Laptop works great, actually, I used my Carrie for about 5 hours off of my laptop in the work van today. Very happy with it. 

 My issue is with one of my PCs at home. Like you, I also uppped it to Windows 7, 64 bit, and regrettably I still have the issue. I did a clean install, so I would have to say it is a hardware type thing. I checked in the bios for any sort of USB settings (legacy, power, etc) and at this point have not been able to resolve it. When using it the left and right tend to jump around and then eventually I just get static. I tried multiple ports on the machine hoping maybe it was just 1 usb host controller, but no such luck. 

 I would be curious if I used a different USB controller card (PCI or whatever) but I don't have one sitting around to try. I havn't spent a whole lot of time working on it since now I have just been bringing my laptop to my other PC when I want music. I know, I know. Sad and lazy 
	

	
	
		
		

		
		
	


	


_

 

I know, I'm really enjoying it on my XP desktop at work. 
	

	
	
		
		

		
		
	


	




 Alas, I've changed the USBAUDIO.sys driver from the 2009 edition to the XP usbaudio.sys as described here.

replacing sys file in vista! - Nightmare! - Icrontic Forums

 Switching USB ports doesn't help. All USB Root Hubs have the most recent drivers. It messes up when my computer is plugged in and when it runs on batteries. I even changed the usbaudio registry "Start" entry from 3 to 2, meaning it will always be on, even if no USB speaker is plugged in.

  Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_I didn't do anything other then plug it in on either box. The 64 bit build 7100 (RC1) is at work. Here at home, I have a 32 bit build 7077 and the Bantams work fine. I only have one working right now and I'm listening to it on my 32 bit Windows 7 right now (The Cranberries are pretty great hehe).

 I never had any problems with the 64 bit Windows 7 either, but I haven't been using a Bantam there since my MHSS killed one a few weeks ago 
	

	
	
		
		

		
		
	


	




 I'm planning to rebuild it, but I've been way to busy lately._

 

I checked voltages on all the chips while the static went nuts, and everything checked out. None of the chips were overheating, so it doesn't seem to be a hardware issue on the DAC/amp side. Installing Vista SP2 didn't work, and using Windows 7, either by upgrading (me) or by clean installing (Gross), didn't work. It doesn't work on my laptop 32-bit, and it doesn't on Gross' desktop 64-bit. It works on Hayduke's Windows 7s, both in 32- and 64-bit. 

 Here are some links that I've read in the past week:

Why aren't my USB speakers working correctly?
Laptop USB ports stopped working - CNET Windows XP Forums
USB port may stop working after you remove or insert a USB device
Some USB audio devices and some USB audio TV tuners do not work correctly together with a Windows Vista-based computer
USB devices may not work after your Toshiba notebook computer returns from standby in Windows XP
http://www.henleydesigns.co.uk/asset...elpNotesv2.doc
A hotfix rollup for the USB audio driver is available for Windows Vista-based and Windows Server 2008-based computers
An Audio Streaming Input and Output (ASIO) driver may not work correctly on a Windows Vista-based computer
The audio from a USB speaker is distorted after you connect an additional USB device to a Windows Vista-based computer
Cumulative update rollup for Windows Vista

 I will try reinstalling my USB controllers, though I imagine them to be working just fine. Such is life when troubleshooting...


----------



## Hayduke

I can't recall which USB device it was (It wasn't my Bantam), but I recall having a problematic device and I had to uninstall all the USB devices in device manager and then reboot and let Windows rebuild them all. Of course, this was back when my home machine was XP, but it did solve the issue.

 Sorry I can't be of much more help, but I've had zero problems with my Bantams on Windows 7.


----------



## joneeboi

Actually, the route I took was to downgrade from 7 to XP. It's taken 8 days, but I finally did it. I've never done anything so grueling in a while. First, I couldn't boot from the XP CD because my hardware required an XP SP2 build. Then I didn't have any CDs to burn, so I tried booting via USB. That didn't work out for some reason. Then my SATA HDD was set in the wrong mode in the BIOS, so that took me a while to figure out. And _then_ my Windows XP product key didn't work. After waiting a long time on the phone and getting shuffled around from line to line, I got a new product key and now I'm setting up my new computer. Hurrah.

 Yes, I'm probably the worst case scenario when it comes to the PCM2702. 
	

	
	
		
		

		
		
	


	




 I'm getting there, little by little. At least I have a little more control over my more reliable OS now.


----------



## TheEKey

Hello Guys,

 It happened that IC2 of my Bantam DAC was fried sometime ago.

 Call it DAC 1, using Elna RFS Silmic II as output caps.

 There's DAC 2, Wima as output caps.

 First I found that there were serious distortion from the music that I play from my PC. So I disconnected it and reconnected it again. It gave much noise to the loudest volume (so even I turned down the winamp vol to 0, noise was not affected at all). So I disconnect it and reconnect it again. It went totally off (reading only 0.7V instead of 4.7V on IC2). 

 IC2 on DAC1 fried.

 But I applied the same sequence to DAC2. No problem so far.

 I'm not sure what happened. I suspect that it's how I connect/disconnect the DAC to the amp and computer. Does it make any sense?

 Connecting: I usually turn on and warm up the AMP, Millett Hybrid MAXed. Meanwhile, connect the DAC to the computer. After about ten minutes, connect the input of amp to the output of DAC. Then, I plug in the headphone and start enjoy music.

 Disconnecting: Stop music -> Turn vol of amp to 0 -> unplug the headphone -> power off the amp -> disconnect it from the DAC and unplug the DAC.

 Any of these sequence can potentially cause the IC2 to be fired? Please advise.


 Best regards,

 Matt


----------



## tomb

Quote:


  Originally Posted by *TheEKey* /img/forum/go_quote.gif 
_Hello Guys,

 It happened that IC2 of my Bantam DAC was fried sometime ago.

 Call it DAC 1, using Elna RFS Silmic II as output caps.

 There's DAC 2, Wima as output caps.

 First I found that there were serious distortion from the music that I play from my PC. So I disconnected it and reconnected it again. It gave much noise to the loudest volume (so even I turned down the winamp vol to 0, noise was not affected at all). So I disconnect it and reconnect it again. It went totally off (reading only 0.7V instead of 4.7V on IC2). 

 IC2 on DAC1 fried.

 But I applied the same sequence to DAC2. No problem so far.

 I'm not sure what happened. I suspect that it's how I connect/disconnect the DAC to the amp and computer. Does it make any sense?

 Connecting: I usually turn on and warm up the AMP, Millett Hybrid MAXed. Meanwhile, connect the DAC to the computer. After about ten minutes, connect the input of amp to the output of DAC. Then, I plug in the headphone and start enjoy music.

 Disconnecting: Stop music -> Turn vol of amp to 0 -> unplug the headphone -> power off the amp -> disconnect it from the DAC and unplug the DAC.

 Any of these sequence can potentially cause the IC2 to be fired? Please advise.


 Best regards,

 Matt_

 

No.

 The only known instance of frying Alien DACs and BantamDACs is with the Starving Student. That amp has a peculiar power arrangement and the MOSFETs are biased through the tube heaters to ground. The best we've been able to determine lately is that a capacitive charge may develop on the RCA jacks that fries the DAC. Even then, it's the DAC that's fried - because it has no inherent protection on the analog outputs. On any other amp, however, the output capacitors are sufficient for protection.

 I have connected/disconnected Alien and BantamDACs in almost every way imagineable - everything from prototype boards, MAXes, MOSFET MAXes, and MiniMAXes - prototypes and production models, using PC's, Laptops, Netbooks, USB hubs, USB cable repeaters, etc., etc. and in all environments - home, work, and headphone meets. Never once have I had an incident with any MAX/MiniMAX/MOSFET-MAX.

 The fact that you're saying IC2 was fried leads me to suspect it was probably hanging by a thread at the start. I am not aware of any connection/disconnection scenario even with the Starving Student that would fry IC2. While any device such as IC2 is susceptible to ESD, it shouldn't be once attached to the board and properly grounded. It also has output current limiting as a safety feature.

 IMHO, your connections/disconnections had nothing to do with it.


----------



## joneeboi

Since this is a thread for commenting on the board's layout, I think the VREG caps should be rearranged such that ground and line aren't so close. By now, a good few hundred Bantams have been built without a problem, but I see this as a potential hazard. I think we're mostly fine with the TPS chips limiting output current, but they can generate quite a bit of thermal energy when shorted. It's fairly easy to bridge these pads, so I think it would be safer to flip the caps a bit. This observation applies to C14, C15 and IC2's TPS C16. Again, the world will spin even if these caps stay put, but that's my comment on the layout.


----------



## tomb

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_Since this is a thread for commenting on the board's layout, <snip>_

 

Actually, this is the *BantamDAC* thread. It's just that "Comments for my PCM2702 Layout" was back in August of 2006 and Colin can't edit that title anymore because it's so old.


----------



## Rooford

Hi,

 I've built two BantamDACs and have to say I'm really pleased with them. To my ears it takes 10 hours or so for the output capacitors to really break in.

 I thought I'd add a couple of notes for anybody using Ubuntu/Amarok/Alsa drivers as I don't think it's been covered in this thread.

 First off open a terminal and check the DAC is listed as a usb device:
 $lsusb

 You should see the DAC listed along with other USB devices.

 Then check the sound card is available using the asound utility:
asoundconf list
 Names of available sound cards:
 Intel
 PCM2702

 I then set the DAC to be the default:
asoundconf set-default-card PCM2702

 This will create a file in your home directory:
.asoundrc

 You can then using Amarok as your media player, index and play your music collection. Use Google to find help on setting up Amarok to play mp3s.

 This works fine however, I noticed that the alsa driver uses dmix to upsample the output to 48KHz. 

 Use the following command while playing an mp3 file to check. Note: The PCM2702 sound card is listed as card1 for me.

cat /proc/asound/card1/stream0

 access: MMAP_INTERLEAVED
 format: S16_LE
 subformat: STD
 channels: 2
 rate: 48000 (48000/1)
 period_size: 1024
 buffer_size: 16384

 You can see a list of supported sample rates for the device using:

cat /proc/asound/card1/pcm0p/sub0/hw_params


 While upsampling is OK if you'd prefer the alsa driver to leave the sample rate alone you can tweak your ~/.asoundrc file to setup an alsa plugin. You'll need to know how alsa identifies the DAC, use aplay:

aplay -l

 As mentioned before my DAC shows up as card 1 device 0. Infact the DAC should only have one device.

 Then edit your ~/.asoundrc file:
pcm.myCard {
 type hw
 card 1
 device 0
 }
 ctl.myCard {
 type hw
 card 1
 device 0
 }
 pcm_slave.s44100 {
 pcm myCard
 rate 44100
 }
 pcm.rate_convert {
 type rate
 slave s44100
 }


 It's a bit esoteric but you're creating an alsa software slave plugin for your hardware card. Save the file then restart your alsa service:
sudo /etc/init.d/alsa-utils restart

 Then restart Amarok (make sure it doesn't just hide in the system tray).

 In Amarok settings->Engine->Output Plugin
 Change to alsa rather than default

 Click apply, some options should appear for Mono / Stereo playback.

 Change the Stereo option to:
 plug:rate_convert

 Note: I found in the alsa notes that the alsa driver will by default try and use the same sample rate if the card supports it so you could also change the stereo option to:
 plug:myCard

 Then check the sample rate is now 44.1KHz using 
cat /proc/asound/card1/stream0


 Hopefully that helps!

 BTW, the DAC works fine on Mac OSX, you can change the default sample rate using the Audio Midi Tool in /Applications/Utilities
 Click the Audio Tab and choose Burr-Brown Japan PCM2702 to set the default output device. You can also tweak the sample rate there although it defaults to 44.1KHz


----------



## cobaltmute

Search denied me and I didn't see this on this on the BantamDAC website, but what is the diameter of the mounting holes?


----------



## tomb

Quote:


  Originally Posted by *cobaltmute* /img/forum/go_quote.gif 
_Search denied me and I didn't see this on this on the BantamDAC website, but what is the diameter of the mounting holes?_

 

I apologize for that oversight. They're 1/8" diameter - 0.125". 4-40 screws are appropriate.


----------



## pistolsnipe

i was wondering if there was an easy way to get an indicator of signal lock. the y1 has a feature for usb where the led changes color based on whether there is an audio signal or not, is it possible that the 2702 has a pinout for that?


----------



## MoxMonkey

so i finished my first bantam and it's having a few issues

 vista64 doesn't recognize it when plugged in and both of the regulators read 3.0 v

 i've checked all of the connections on the dac chip and reflowed them but still nothing, at this point is it likely the dac chip is dead or one of the regulators?


----------



## tomb

Quote:


  Originally Posted by *MoxMonkey* /img/forum/go_quote.gif 
_so i finished my first bantam and it's having a few issues

 vista64 doesn't recognize it when plugged in and both of the regulators read 3.0 v

 i've checked all of the connections on the dac chip and reflowed them but still nothing, at this point is it likely the dac chip is dead or one of the regulators?_

 

I'm afraid you won't like the answer: the PCM2702 is only compatible with VISTA _Business_. Other flavors of VISTA won't work.
	

	
	
		
		

		
		
	


	




 From TI: http://focus.ti.com/lit/er/slaa374/slaa374.pdf


----------



## MoxMonkey

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I'm afraid you won't like the answer: the PCM2702 is only compatible with VISTA Business. Other flavors of VISTA won't work.
	

	
	
		
		

		
		
	


	




 From TI: http://focus.ti.com/lit/er/slaa374/slaa374.pdf_

 

a bit of a bummer but at least it may still work


----------



## tomb

Quote:


  Originally Posted by *MoxMonkey* /img/forum/go_quote.gif 
_a bit of a bummer but at least it may still work 
	

	
	
		
		

		
		
	


	


_

 

Oops! I didn't notice before that you said _both_ regulators measured 3.0VDC. There's a problem with one of them if that's the case. IC2 should register ~4.75VDC


----------



## Forte

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I'm afraid you won't like the answer: the PCM2702 is only compatible with VISTA Business. Other flavors of VISTA won't work.
	

	
	
		
		

		
		
	


	


_

 

Other flavours of Vista can work, using Vista Home Premium 64bit and Bantam just fine.


----------



## Billyk

I am happy to report my Bantam works flawlessly on Vista Ultimate 64 and 32 bit editions. My laptop is 32 and desktop is 64 They are both up to date with all patches and service packs.


----------



## tomb

This is great news, guys! Joneeboi's been having fits with his over in the Carrie thread - finally loaded a different operating system and then everything worked. I'm curious as to whether this is a recent patch/service pack from MS for these different versions of Vista - because we went through a bunch of different scenarios in Joneeboi's thread and the OS was the culprit.


----------



## rds

More good news:
 I just plugged my Bantam into my Vista Home Premium 32 bit (I think this is the most common edition for notebooks) notebook and it works fine.

 EDIT I guess the next question is will the pcm2702 work with Windows 7? Afaik if it works in Vista then it should work in Windows 7.


----------



## JamesL

Yes. I've been using it on windows 7 x86 and x64 for quite a while now.


----------



## Forte

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I'm curious as to whether this is a recent patch/service pack from MS for these different versions of Vista_

 


 No, have been using my Bantam with Vista64 since early this year.


----------



## MoxMonkey

so it's definitely not the OS as it shows up as unknown device on an XP machine as well

 both regulators read 3.03 and 3.09 (depending on usb port, the higher being right off the motherboard rather than through front jacks)

 any suggestions on where to start looking for a solution?


----------



## tomb

Quote:


  Originally Posted by *MoxMonkey* /img/forum/go_quote.gif 
_so it's definitely not the OS as it shows up as unknown device on an XP machine as well

 both regulators read 3.03 and 3.09 (depending on usb port, the higher being right off the motherboard rather than through front jacks)

 any suggestions on where to start looking for a solution?_

 

You didn't use the same TPS chip in both places, did you? One's a 3.3V regulator, but the other one's a 4.75V regulator - TPS79333 (IC1) and TPS793475 (IC2), respectively.


----------



## Forte

Start reading here if you haven't already BantamDAC Checks and Setup.

 You should be getting 3.3vdc for IC1 and 4.75vdc for IC2 so it looks like you have a problem with IC2 and maybe IC1 as well. 

 Try to resolder the regs to make sure you have a good joint, FWIW I actually found these regs harder to solder than the DAC.


----------



## Juaquin

I can confirm that the BantamDAC works on:
 Mac OSX Leopard
 Mac OSX Snow Leopard
 Vista 64-bit Business
 Windows 7 32-bit RC

 I actually HAVE to use the Bantam on my MacBook Pro when running Windows 7 because Apple hasn't fixed their audio drivers to work with 7 yet.


----------



## MoxMonkey

so got around to actually trying to get it to work today

 reflowed the regs, still both read 3.0 replaced them with another pair i had making sure to check part numbers that mouser sent me and still the same

 at this point i'm at a loss as my pc will just list "Unknown device" but still light the LED


----------



## tomb

Quote:


  Originally Posted by *MoxMonkey* /img/forum/go_quote.gif 
_so got around to actually trying to get it to work today

 reflowed the regs, still both read 3.0 replaced them with another pair i had making sure to check part numbers that mouser sent me and still the same

 at this point i'm at a loss as my pc will just list "Unknown device" but still light the LED_

 

Maybe post a pic or two and let us take a look?

 Meanwhile, just to make sure: 
 1. You're measuring the voltage at IC1 by measuring the ends of C11 (should be 3.3V)?
 2. You're measuring the voltage at IC2 by measuring the ends of C13 (should be 4.75V)?
 3. Did you install C16 at the R8 position and left the R7 and C16 positions un-populated? (The red BantamDAC PCB says C16 at two positions - it should go at the R8/C16 position.)
 4. Does the LED light? (Never mind - you said it did.) If so, what's the voltage across R9? Or, the voltage from the bottom end of R9 to Ground?


----------



## MoxMonkey

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Maybe post a pic or two and let us take a look?

 Meanwhile, just to make sure: 
 1. You're measuring the voltage at IC1 by measuring the ends of C11 (should be 3.3V)?
 2. You're measuring the voltage at IC2 by measuring the ends of C13 (should be 4.75V)?
 3. Did you install C16 at the R8 position and left the R7 and C16 positions un-populated? (The red BantamDAC PCB says C16 at two positions - it should go at the R8/C16 position.)
 4. Does the LED light? (Never mind - you said it did.) If so, what's the voltage across R9? Or, the voltage from the bottom end of R9 to Ground?_

 


 Turns out I had forgotten C16 but that's now in place in R8. Doesn't change the reg voltage, both still measure 3.0v, the LED reads 2.65v


----------



## tomb

Quote:


  Originally Posted by *MoxMonkey* /img/forum/go_quote.gif 
_Turns out I had forgotten C16 but that's now in place in R8. Doesn't change the reg voltage, both still measure 3.0v, the LED reads 2.65v_

 

So, is the voltage across R9 about 2.35V?

 If you get that voltage across R9, then you have 5V from your USB. If so, it sounds like IC2 is a TPS9333, not a TPS93475.

 How about the pics?


----------



## MoxMonkey

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_So, is the voltage across R9 about 2.35V?

 If you get that voltage across R9, then you have 5V from your USB. If so, it sounds like IC2 is a TPS9333, not a TPS93475.

 How about the pics?_

 

Sorry for the delay, had a busy couple days and had to find a camera that would take decent closeup shots.

ImageShack -

 For measuring R9, where should it be measured from? If I measure right across R9 I get 0.36 (which may be off as my meter is running on low battery)


----------



## tomb

Quote:


  Originally Posted by *MoxMonkey* /img/forum/go_quote.gif 
_Sorry for the delay, had a busy couple days and had to find a camera that would take decent closeup shots.

ImageShack -

 For measuring R9, where should it be measured from? If I measure right across R9 I get 0.36 (which may be off as my meter is running on low battery)_

 

Assuming your meter is OK, that measurement across R9 explains a lot. The voltage leg for R9 and the LED are taken directly from the USB power connection - no regulator involved. This means you're only getting about 3V (2.65 + 0.36) from your USB power connection. You should have 5V.

 EDIT: Looking at your pics, you've wired the USB cable incorrectly. Refer to this page on the BantamDAC website for proper color coding the wires to the proper holes:
http://www.diyforums.org/BantamDAC/B...ACcabledac.php
 You have the green and red wires reversed.


----------



## MoxMonkey

awww, i had looked at that page when wiring it up yet somehow mixed them up.

 i'll swap it tomorrow after work and let you know


----------



## MoxMonkey

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Assuming your meter is OK, that measurement across R9 explains a lot. The voltage leg for R9 and the LED are taken directly from the USB power connection - no regulator involved. This means you're only getting about 3V (2.65 + 0.36) from your USB power connection. You should have 5V.

 EDIT: Looking at your pics, you've wired the USB cable incorrectly. Refer to this page on the BantamDAC website for proper color coding the wires to the proper holes:
BantamCableDAC
 You have the green and red wires reversed.
	

	
	
		
		

		
		
	


	


_

 

finally got around to fixing the USB cable and that did it.


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## tomb

Quote:


  Originally Posted by *MoxMonkey* /img/forum/go_quote.gif 
_finally got around to fixing the USB cable and that did it. 
	

	
	
		
		

		
		
	


	


_

 

That's great news! Glad to hear you got it working!


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## Forte

Have a problem with my latest Bantam DAC build. 

 Plugged in the USB cable to check voltages were okay before wiring it up to my Carrie amp but the LED did not light up and there was a small wisp of smoke from underneath the board near the USB terminal. No voltage present anywhere on the board and after unplugging the board and inspecting it there are scorch marks at each end of L3. Have unsoldered L3 and the pad nearest to C8 has come loose from the board.

 All parts seem to be in the correct place and orientation, any ideas what may be wrong?


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## tomb

Quote:


  Originally Posted by *Forte* /img/forum/go_quote.gif 
_Have a problem with my latest Bantam DAC build. 

 Plugged in the USB cable to check voltages were okay before wiring it up to my Carrie amp but the LED did not light up and there was a small wisp of smoke from underneath the board near the USB terminal. No voltage present anywhere on the board and after unplugging the board and inspecting it there are scorch marks at each end of L3. Have unsoldered L3 and the pad nearest to C8 has come loose from the board.

 All parts seem to be in the correct place and orientation, any ideas what may be wrong?_

 

I hate to say it, but it sounds like something came into contact with L3 and shorted it. Is it possible a stray wire/frayed wire, or the case came into contact with L3? Usually, C8 is the part that sticks out the most on the bottom of the board, but L3 has a connection directly with the charged positive of C7 that's right at the edge of the board.


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## Forte

It wasn't cased up, just held in my helping hands so I could check voltages so no direct short to L3, have had a look over the board with a jewelers magnifier and have found a solder bridge from one leg of IC1 to C15 near the C7 cap, could this have caused the problem?

 What apart from L3 could have been damaged from this, anything else?


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## tomb

Quote:


  Originally Posted by *Forte* /img/forum/go_quote.gif 
_It wasn't cased up, just held in my helping hands so I could check voltages so no direct short to L3, have had a look over the board with a jewelers magnifier and have found a solder bridge from one leg of IC1 to C15 near the C7 cap, could this have caused the problem?

 What apart from L3 could have been damaged from this, anything else?_

 

Just guessing here, but I doubt that would've caused it. Maybe you should check for a bridge around the left USB connector tab and L3 - or perhaps the tab is not totally secure and could've flexed into L3? Is it possible one of the helping hands' alligator clips could've touched this area?

 As for how much is damaged, that's pretty hard to predict. I'd begin by replacing L3 and seeing if that fixes it - assuming you continue to check for solder bridges and contact points. If that doesn't fix it, then check the voltages for IC1 and IC2 next, and proceed from there.


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## Forte

There may have been a bridge between L3 and the USB connector, can't be sure now as I have removed L3, L4, C8 and the USB connector from the board. That area of the board is so tightly packed it was hard to see so I decided to clear it and redo all those parts again.

 Replacement parts on the way.


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## Juaquin

So I've finally gotten some time to work on my non-functioning Bantam. When I plug it in, it is unrecognized by the computer and IC2 (4.75V) heats up immediately. I haven't had a chance to check the voltage coming out of it since I disconnected it so quickly to prevent damage. Any idea what's causing this? I'll get some pics up tomorrow but was hoping someone had run into this before.


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## tomb

Quote:


  Originally Posted by *Juaquin* /img/forum/go_quote.gif 
_So I've finally gotten some time to work on my non-functioning Bantam. When I plug it in, it is unrecognized by the computer and IC2 (4.75V) heats up immediately. I haven't had a chance to check the voltage coming out of it since I disconnected it so quickly to prevent damage. Any idea what's causing this? I'll get some pics up tomorrow but was hoping someone had run into this before._

 

Nope - haven't heard of it, as far as I can remember. However, it sounds like a part is out of place or something is bridged. Hopefully, someone can spot the trouble from your forthcoming pics.


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## Juaquin

Well I figured it out. If you take a high-powered flashlight (CREE-LED or similar) and shine it through the PCB, you can see the legs on the PCM2702 and easily see tiny bridges. I found one between two pins around pin 18 or so that I hadn't on visual inspection. I believe it was shorting the 4.75V to GND, hence the heating and non-functioning. 

 I've repaired the bridge and no longer have heating, but the voltage across C13 (i think it's C13, it's the 4.75V cap) is 5V, so I think I've blown the TPS reg. I'm wondering if exposing all the 4.75V pins to 5V may have fried the DAC; if so, I'd rather start from scratch with a new DAC than replace the TPS and still not have it work.


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## cobaltmute

The 4.75 pin are designed for 5V and have an absolute max tolerance of 6.5V per the datasheet.


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## Billyk

Quote:


 Well I figured it out. If you take a high-powered flashlight (CREE-LED or similar) and shine it through the PCB, you can see the legs on the PCM2702 and easily see tiny bridges. 
 

That is by far the best method when it works! Saved me twice so far.
 Anyway good luck I hope it works when you replace the reg.


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## Juaquin

Quote:


  Originally Posted by *cobaltmute* /img/forum/go_quote.gif 
_The 4.75 pin are designed for 5V and have an absolute max tolerance of 6.5V per the datasheet._

 

Awesome; I was looking through the datasheet but must have missed it. Here's hoping replacing the reg works!


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## tomb

Quote:


  Originally Posted by *Juaquin* /img/forum/go_quote.gif 
_Awesome; I was looking through the datasheet but must have missed it. Here's hoping replacing the reg works!_

 

If I'm reading the datasheet correctly on the reg, the min and max on the TPS793475 output is 4.655VDC and 4.845VDC, respectively, when fed with a voltage between 5.25V to 5.5V. I'd say it's blown. After all, you had it connected to a dead short with that bridge. Not many IC's/transistors can survive that for long. Sorry.


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## cobaltmute

My comment was for the PCM2702, and was in response to this:

  Quote:


  Originally Posted by *Juaquin* /img/forum/go_quote.gif 
_I'm wondering if exposing all the 4.75V pins to 5V may have fried the DAC; if so, I'd rather start from scratch with a new DAC than replace the TPS and still not have it work._


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## tomb

Quote:


  Originally Posted by *cobaltmute* /img/forum/go_quote.gif 
_My comment was for the PCM2702, and was in response to this:_

 

Ah - I can read data sheets but not posts.
	

	
	
		
		

		
		
	


	




 Still, the TPS definitely sounds blown.

 EDIT: Of course, you are correct about the PCM chip. After all, there were configuration options with the Alien DAC that used no regulation at all - just straight from the USB power.


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## Juaquin

Yeah, I'm only wondering about the health of the PCM - I know the reg is blown to bits. Poor thing was trying to make ground equal 4.75V, and it lost 
	

	
	
		
		

		
		
	


	




 However, in theory, even if the TPS is blown and supplying 5V, shouldn't the PCM still work (considering the comment about the Alien running without regulation)? Or is there something that actually requires 4.75V and is not 5V-tolerant?


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## tomb

Quote:


  Originally Posted by *Juaquin* /img/forum/go_quote.gif 
_Yeah, I'm only wondering about the health of the PCM - I know the reg is blown to bits. Poor thing was trying to make ground equal 4.75V, and it lost 
	

	
	
		
		

		
		
	


	




 However, in theory, even if the TPS is blown and supplying 5V, shouldn't the PCM still work (considering the comment about the Alien running without regulation)? Or is there something that actually requires 4.75V and is not 5V-tolerant?_

 

Yes (it should've worked), assuming you cleared those bridges and there wasn't any damage.


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## Juaquin

Hmm. May just need to start over then, probably fried the DAC. Thanks for the help guys!


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## Dan55

Hi all,

 Yet another troubleshooting post. My computer is not recognizing the dac, so I guess there is a problem with IC1 or the chip (or both). 

 I'm reading 2.10V across C11 and IC1 looks like it could use some more solder, but I have a pretty cumbersome iron and wanted to consult the experts before I start soldering again 
	

	
	
		
		

		
		
	


	




. Is there a particular pin I should be focusing on? Thanks!

 edit: Unfortunately, I don't have a camera with me right now.


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## tomb

Quote:


  Originally Posted by *Dan55* /img/forum/go_quote.gif 
_Hi all,

 Yet another troubleshooting post. My computer is not recognizing the dac, so I guess there is a problem with IC1 or the chip (or both). 

 I'm reading 2.10V across C11 and IC1 looks like it could use some more solder, but I have a pretty cumbersome iron and wanted to consult the experts before I start soldering again 
	

	
	
		
		

		
		
	


	




. Is there a particular pin I should be focusing on? Thanks!

 edit: Unfortunately, I don't have a camera with me right now._

 

Sounds like you know where to look.
	

	
	
		
		

		
		
	


	




 IC1 should be producing 3.3V across C11. I can't tell you what pin to focus on, but a pic or two may help if you don't solve it.


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## Dan55

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Sounds like you know where to look.
	

	
	
		
		

		
			





 IC1 should be producing 3.3V across C11. I can't tell you what pin to focus on, but a pic or two may help if you don't solve it._

 

Thanks. I think I'm gonna wait for a new iron, as getting in between IC1 and C7 is currently pretty problematic.


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## Dan55

Yep - IC1 needed a bit more solder. The dac is now working but producing a fairly audible buzzing. Could this be attributable to interference? I haven't yet cased it.

 Also, for anyone starting out, I found upgrading from the Weller SP23 to the WCL100 to be a great help

 (Thanks to tomb for your assistance and the website; I've been enjoying my MM amp for quite a while now.)


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## tomb

Quote:


  Originally Posted by *Dan55* /img/forum/go_quote.gif 
_Yep - IC1 needed a bit more solder. The dac is now working but producing a fairly audible buzzing. Could this be attributable to interference? I haven't yet cased it.

 Also, for anyone starting out, I found upgrading from the Weller SP23 to the WCL100 to be a great help

 (Thanks to tomb for your assistance and the website; I've been enjoying my MM amp for quite a while now.)_

 

You are welcom for the assistance and thanks for the kind comments.
	

	
	
		
		

		
		
	


	




 I don't mean to be critical, but perhaps if your soldering was a bit dodgy on the IC1 reg, maybe you should check IC2, the PCM chip and all the other joints. The only thing I can think of is an intermittent connection or short that's causing the buzzing.

 One trick many people use is to hold the board up to a very bright light or directly next to a light bulb. The fiberglass PCB is translucent enough that you can see through the solder joints for any bridges or un-soldered joints.


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## Billyk

Quote:


 One trick many people use is to hold the board up to a very bright light or directly next to a light bulb. The fiberglass PCB is translucent enough that you can see through the solder joints for any bridges or un-soldered joints. 
 

I highly recommend this! With my poor eyesight it is the most effective method of finding poor and/or bridged joints.


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## Juaquin

A high-power LED flashlight is perfect for this. Just don't blind yourself


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## Dan55

Thanks, guys. I tried using the way-too-bright LED I have on my Millett Max, but it required some awkward contortions. I'll have to retrieve my LED flashlight next time I'm upstate...


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## joneeboi

For those of you with great memory, it seems the issues I had with my Bantam were confined to that one computer. It must have handled USB power differently than everyone else's. That was a Toshiba L300D, but now I have an HP dm3-1020CA which I just used to listen to the Bantam for some 3 hours without the horrible screeching. At ease, gentlemen.


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## the_equalizer

Well, just wanted to say thanks for a great DAC. I bought the Glass Jar Audio kit a couple of weeks ago to go along with my wonderful Millett MiniMax.

 Got the kit yesterday and built it today. All in all, I was expecting to suffer with the SMD work (I confess that I ordered the PCM chip pre-soldered), but much to my surprise that took only a couple of hours; with the bulk of my suffering being the casework, just as usual.

 Anyway, thanks again for this killer DAC! 
	

	
	
		
		

		
		
	


	













 cheers!


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## ShinyFalcon

If I use a different Q1, do I size C9/C10 by the crystal's load capacitance value?

 I'm looking at 559-FOXS120-LF for a substitute Q1, and this one does not have a load capacitance value. Do I simply omit C9/C10 if I use this crystal?

 559-FOX120-20-LF has a 10pF load capacitance value, and is a bit tall, but I'm assuming it will work as well.


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## cobaltmute

520-HCU1200-20X looks to be an alternate to the out of stock crystal.

 559-FOXS120-LF has a load capacitance of 10pF (read the datasheet). You would need to change C9/C10.


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## rbarth

I was moving along pretty well putting together my first Bantam DAC and now find myself tripped up just before the end. My USB connections are straight to the board and the cable looks really nice coming out one side of the case. But, I’m not sure about the RCA 3.5mm connections. I would like both RCA cables to come of the other end of the case and terminate in male connections that I can plug directly into my MiniMAX. On the quality cables I bought for this, there is a solid silver wire in the center and many strands of thin copper wire wrapped around a sheath that surrounds the center wire. I’m assuming this is what I should use to make the ground connection. HOWEVER, when I collect all of these copper strands and twist them together into a straight piece, the result is too fat to fit into the ground connection on the DAC board. So, first of all, am I right about these copper strands being the ground? If so, how can I deal with the fact that when twisted they don’t go through the hole? Am I using the wrong cable? Can I solder a wire to this twisted strand and connect that to the ground? I would really like to avoid mounting female connectors on the side of the case and then plugging male connectors into that from the outside. Thanks in advance for any help with this.


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## tomb

Quote:


  Originally Posted by *rbarth* /img/forum/go_quote.gif 
_I was moving along pretty well putting together my first Bantam DAC and now find myself tripped up just before the end. My USB connections are straight to the board and the cable looks really nice coming out one side of the case. But, I’m not sure about the RCA 3.5mm connections. I would like both RCA cables to come of the other end of the case and terminate in male connections that I can plug directly into my MiniMAX. On the quality cables I bought for this, there is a solid silver wire in the center and many strands of thin copper wire wrapped around a sheath that surrounds the center wire. I’m assuming this is what I should use to make the ground connection. HOWEVER, when I collect all of these copper strands and twist them together into a straight piece, the result is too fat to fit into the ground connection on the DAC board. So, first of all, am I right about these copper strands being the ground? If so, how can I deal with the fact that when twisted they don’t go through the hole? Am I using the wrong cable? Can I solder a wire to this twisted strand and connect that to the ground? I would really like to avoid mounting female connectors on the side of the case and then plugging male connectors into that from the outside. Thanks in advance for any help with this._

 

Yep - that's what I was going to suggest: solder a jumper (flex wire, not a resistor lead).

 Just an FYI, but the PCB was designed for standard 22ga multi-strand flexible. All I ever use is 22ga multi-strand Teflon-insulated SPC (from John's Wire Shop on ebay).


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## rbarth

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yep - that's what I was going to suggest: solder a jumper (flex wire, not a resistor lead).

 Just an FYI, but the PCB was designed for standard 22ga multi-strand flexible. All I ever use is 22ga multi-strand Teflon-insulated SPC (from John's Wire Shop on ebay)._

 

Thanks Tom. Took your recommendation about wire when I was putting the MiniMAX together and stocked up on that from John's Wire Shop. So, time now to finish up!


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