# Carrie USB-Powered Headphone Amplifier



## joneeboi

Greetings DIY subforum,

 I am interested in designing a USB-powered headphone amplifier that fits with tooleAudio's BantamDAC in a Hammond Mfg. 1455C80x case. I have had this idea in my head for maybe a year, but flying solo, I haven't been able to get very far. My interest was tickled by rds' USB Powered Pimeta thread which brought up the topic of powering an amplifier with USB power. I got the brilliant idea to design a USB-powered headphone amplifier when my Toshiba laptop's physical volume knob was snapped off and music was impossible to get from the onboard sound card. I figured I'd make an Alien DAC and throw it into a 1455C80x with a USB-powered amplifier before interest waned when I got a new laptop and I got music again. However, thinking about it again has made me really want to do this anyway. I figured I should contribute my time and energy to this board for all I've gained from it, and I want to do it for fun as well. 
	

	
	
		
		

		
			





 First things first, how viable is a USB-powered headphone amplifier? Basically, I want to recreate my own version of the dsavitsk's HPDAC but with just the amplifier section. Maybe I'd be better off including my own DAC section, but there's a perfectly good module I can point to without spending time and energy unnecessarily.

 Next, I outline my design goals in order of highest priority to lowest.

USB-powered
Fit into the Hammond 1455C80x
3-channel CMoy amplifier
Low-cost
Relatively easy to build
Items 3. through 5. aren't hard and fast rules, but I'd like to start there. I'm glad the BantamDAC came out when it did because it has a smaller footprint and costs less than the AlienDAC. I realize that I could also get something like the HeadAmp Pico, but I'm not interested in spending that kind money on my audio wares just yet. And despite being part of an audio forum, I left out "6. Great sound quality." I'm more interested in getting it to work first, and then I'll play with the idea of beefing up the amplifier. Unfortunate but that's what I have to work with at the moment.

 I realize I'm walking alongside giants in this forum, so I'm open to learning from all of you. To be honest, it's a bit intimidating even starting this thread which is partly why I didn't start one for so long. I'm completely open to doing the legwork necessary for getting this idea out the door, I just need ideas first.

 Now, let's talk specifics.

 The biggest hurdle here, I feel, is power supply. rds wanted to power his PIMETA, but there is the tricky issue of the virtual ground versus "true earth" ground. This device will be lugged around with my laptop, so the earth ground will be whatever the laptop uses.

 I was thinking of going with a 3-channel CMoy design. Most DIY SS amps I've seen run this course while using virtual ground, eg. PIMETA, PPAv2, M^3, Mini^3, so it won't be as easy as lifting the amplifier schematic from one of those designs and plugging it into a DC-DC boosting circuit. Buffers probably won't be implemented because of the already heavily loaded power supply. If there is room left over, maybe I'll consider it. Keep in mind that the BantamDAC will also be connected to the USB port, so the PCM2702 and TPS regulators will be drawing some current as well. I hope to have a circuit that circumvents the whole trouble of virtual ground vs. earth ground.

 I'm not tied to any one set of opamps at the moment. I don't have much experience outside of OPA627, OPA2134, OPA2132, OPA2227, OPA2107, AD8320, AD8310, JRC4556, AD8397 and OPA690. Think CMoy, PIMETA, A47 and Mini^3. Any suggestions? Opamp rolling sounds tempting, but I'm worried the DIP package will take too much board space. Also, sticking to a certain set of opamps will help with containing current draw, but maybe that can be decided by the builder.

 So that's about it for now. I really should be studying for finals at the moment, but that can wait just a bit. I'll be done all my semester on the 17th, but beyond then, I'll have plenty of time to work on it even into the new year as I am out on an eight month Engineering co-op work term. Any and all comments are welcome. I apologize in advance to those who are tired of seeing yet another one of joneeboi's threads with super huge first posts. 
	

	
	
		
		

		
		
	


	




 I foresee oodles and oodles more of me updating the original post.


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## joneeboi

[size=x-small]Presenting the
 [/size][size=x-small] [size=small]*B*us-*P*owered *M*ini^3

 [/size][/size]
	

	
	
		
		

		
		
	


	



 [size=x-small] 
 In theory, this circuit is supposed to be identical to the Mini^3 but is instead powered by USB alongside the BantamDAC in the Hammond 1455C801. Each USB port offers 2.25W at full power, and the circuit is powered by a 1W DC/DC converter. The 12V boosted voltage is filtered by a CLC filter and regulated by a 10V LDO regulator. The layout is a little different from the Mini^3's, but it borrows very much as many of you will notice.

 Let me continue by explaining my intentions for this new project. My Toshiba Satellite A100 notebook was my main source of music, and I used it every day at school for almost half of every day. About a year ago, the physical volume knob snapped off. To replace my newly lost music, I wanted a solution that was extra portable and convenient. To me, this meant no battery, as few wires as I could get away with, and of course, high quality audio. I started work on a new DAC+amp board, but just as I found the EAGLE library for the PCM2702, the BantamDAC was gaining momentum and became a very popular choice for USB audio. At this point, I had an epiphany: I could use the BantamDAC, which so happened to fit the Hammond, and could just design the amplifier part. Fast forward a couple more months, I asked amb if I could use his Mini^3 amplifier circuit. He agreed if I would give credit to him and if the circuit performed as well as the Mini^3 does. Though at this point I'm not sure this thing will even work, I feel it's all necessary to share in the spirit of responsible invention. If things don't work out, maybe someone will learn from my folly and finish the race for me. I have learned lots from this forum, so this is my attempt at giving back. If all goes well, people will be able to enjoy a truly portable and compact hi-fi headphone amplifer.[/size]

*Amplifier*

 The amplifier schematic is identical to the Mini^3. The layout varies slightly because of the method of signal input. With one less 3.5mm jack on the board, that space can house the L/R section to increase room for the power supply at the rear of the board. This allows for physically and electrically larger capacitors and a smoother power supply. At the top of the board we find a power plane for the negative rail, which ought to provide better cooling for the EPAD underneath the AD8397 as well as a low-impedance path for the return currents.

*Power Supply*

 The 5V 500mA power from the USB is converted to 12V. The TI DCP010512P DC/DC converter is rated for 1W, so there is an output current of 83mA. The DC/DC converter introduces noise at 800 kHz, so a CLC filter with a corner frequency of 580Hz cleans up most of the noise. That voltage is regulated to 10V with the TI TL750L10. The higher supply voltage also gives the amplifier higher voltage swing than the Mini^3.

 One tricky part of using USB power is grounding. The designer must figure out how to separate the signal ground with the USB ground if a virtual grounded amplifier is to be used. One way of solving the problem of the grounding is by using an isolated DC/DC converter. Combining the amplifier with the BantamDAC means connecting signal ground to V-, so with an isolated converter, the output can then float to whatever value relative to signal ground, that is, +/- 5V.
*
 Resources:*
 USB powered AlienDAC with CMoy
http://www.head-fi.org/forums/f6/usb...27/index2.html

 USB-powered amp/ps
http://www.head-fi.org/forums/f6/usb...amp-ps-215585/

 USB powered HIFI headphone amp/DAC
USB powered HIFI headphone amp/DAC - diyAudio


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## joneeboi

Schematic v1.23






 Layout v1.23


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## rds

Quote:


 rds wanted to power his PIMETA, but there is the tricky issue of the virtual ground versus "true earth" ground. 
 

It's not a problem actually. The dc-dc converter is isolated. 

  Quote:


 The biggest hurdle here, I feel, is power supply. 
 

Well, good news - I'm going to build the supply separately on breadboard and break into my school's lab to measure it (and maybe tweak it).

 I will post the circuit diagram and parts list as well as the measurements.
 It will be a regulated 12V galvanic isolated dc supply that can supply 150mA from usb 2.0.
 Then people can take that and use it to power whatever you want. No need to worry about virtual grounds or any related nonsense. 

 I'll have that posted in 2 weeks.

 The cost to build it will be about $16 USD.

 If there's interest and it measures well I might even fab some pcbs, but no guarantees on that. Pcbs for dc-dc converters need to be very carefully designed.

 Anyways, it'll be easy to build.

 EDIT I'll try a capacitance multiplier, as suggested by 00940, too. I might get lucky and be able to get the voltage drop low enough to put it between the dc-dc converter and 12V ldo. However, my feeling is that the capacitance multiplier won't be any use at the 800kHz point where I'm trying to get rid of the ripple.


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## joneeboi

So you're going with 12V then, eh? Which chips did you end up using? I was thinking of getting a run of boards done since I've always been curious about how that all works. Either I can get the PS and amplifier done separately for whoever wants to power whatever, or I can throw it all onto one board. Maybe I'll just stick to the one board for now. I'll keep my eyes peeled for that two week mark. Thanks for the heads up, rds.


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## rds

Quote:


 Which chips did you end up using? 
 

Parts information here

 I'm going to put a pi filter between the converter and ldo. This will use 1uF cermics to effectively filter out that high switcher frequency. Since it is so high I don't need a big inductor to do this. 
 I'll have another pi filter after the ldo. If the switching ripple is nearly gone then I'll use it with big electrolytics to filter low frequency. I'll have to see what I measure. I'll probably just optimize it for wherever there is the most ripple.
 But it's looking very good by a few ideal calculations. I see ti recommends pi filters for their switchers too, so I'm optimistic.


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## millwood

if you use a r2r opamp you can swing fairly close to the rail so that will get you 2vp on the load, conservatively estimating.

 that will produce over 100mw on a 16ohm headphone. that kind of power is typically sufficient for most listening but if you want more, you will have to swing the voltage.

 the safetiest route is a switching mode chip that produces negative supply from a positive rail - plenty of them in various datasheets if you are interested.

 alternatively, you can use one single step-up converter and stay single rail - you will have to use capacitors.

 if you don't want capacitors, you can use also fly-back based dc-dc converters. the dcv family of chips from TI would be a good starting point.


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## millwood

the last alternative would be use one boost up converter and then great virtual ground with it.

 Personally, I would use a voltage intertor to create the negative rail.


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## rds

Quote:


 Personally, I would use a voltage intertor to create the negative rail. 
 

I definitely wouldn't use such a supply for audio.


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## dsavitsk

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_[*]USB-powered[*]Fit into the Hammond 1455C80x[*]3-channel CMoy amplifier[*]Low-cost[*]Relatively easy to build[/LIST]_

 

I would go 2 channel as, frankly, the third doesn't get you much but it does draw a bunch more current.

 For an easier boost converter, take a look at TI's DCP020509 and DCP020507. A little more expensive than some other options, but they have DIP pins, and a pair can be used to make a +/- supply.


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## Mellow Mushroom

why not use battery power instead?


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## rds

Quote:


 why not use battery power instead? 
 

Because the design requirement specifies no batteries.


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## Mellow Mushroom

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_Because the design requirement specifies no batteries._

 

But but... but his laptop uses bat batteries.


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## error401

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_If there's interest and it measures well I might even fab some pcbs, but no guarantees on that. Pcbs for dc-dc converters need to be very carefully designed._

 

Don't think that'll be a big deal. All the high speed stuff is contained on the IC die, so you don't have to worry so much about it. Make sure the decoupling is good and as specified and it will work well.

  Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_EDIT I'll try a capacitance multiplier, as suggested by 00940, too. I might get lucky and be able to get the voltage drop low enough to put it between the dc-dc converter and 12V ldo. However, my feeling is that the capacitance multiplier won't be any use at the 800kHz point where I'm trying to get rid of the ripple._

 

Many LDOs are fast, but many aren't, and it's not always shown in the datasheet. Mostly ripple rejection is specified at 120Hz or 60Hz, and if there's not a graph out to at least 1MHz, you can't really speculate on performance in that region. A cap multiplier can be made very fast and very cheap. Consider the attached that I knocked together in about 5 minutes and did virtually no tuning with. The response is fairly load dependent, it gets better with bigger loads. The sim is at ~100mA; it stays under -50dB @ 800KHz to about 55mA and gets better with increasing loads. I haven't simmed the load response, but it should be fine, and most of the load is probably going to be static anyway. Probably will need an output cap. Drops about 1.5V.

 Edit: Why does head-fi take my 9kb PNG files and transcode them to smaller, much junkier looking JPGs?!


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## rds

I'm not assuming anything about the psrr of the ldo. I'd expect it to be quite poor at high freq.
 The thing is a capacitance multiple can't do anything about the esr (afaik). And if you look at the dc-dc converter datasheet you see that low esr has a far greater effect on reducing ripple than high capacitance. 
 My plan for getting rid of the ripple is a pi filter between the dc-dc and ldo, and possibly a second pi filter after the ldo. I looked at some t.i. reports and this is actually what they recommend where is is not cost or space prohibited. The reason being that even a small L will cause huge attenuation at 800kHz. 
 Also worth mentioning is the L is about $2 - so not too bad when you consider the dc-dc is $15. Oh, and the low esr ceramics are about $1 each


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## rds

I would be happy to try you multiplier out too.
 Have you tried line and load transient testing?


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## error401

Okay okay you're right, I'm a victim of playing around and overengineering instead of actually thinking about the problem 

 The pi filter has a much more linear response and it'll do better with less tuning and less parts. Watch out for a resonant peak somewhere in the audio frequency range though.

 Edit: In the spirit of overengineering, what about a gyrator instead


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## millwood

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_For an easier boost converter, take a look at TI's DCP020509 and DCP020507. A little more expensive than some other options, but they have DIP pins, and a pair can be used to make a +/- supply._

 

the dcv family is the newer replacement for the dcp.

 both are unregulated - but will good line regulation (1%).

 if you want to make them regulated, you can apply feedback on the SYNCin pin and turn them into gated regulator - as those chips turn on in 2us, it should be no problem.


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## millwood

the regulated version of the dcv family is the dcr family but it outputs just 3.3v or 5v so they are of no use here.


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## millwood

Quote:


 I haven't simmed the load response, but it should be fine, and most of the load is probably going to be static anyway. 
 

you will need a capacitor on the output to provide the needed transient current and to help the multiplier when the input voltage is low.

 the ac performance will worsen once you factor in realistic esr /esl.


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## joneeboi

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_I would go 2 channel as, frankly, the third doesn't get you much but it does draw a bunch more current._

 

You know what, I honestly didn't even consider that. I envisioned it as some sort of BantamDAC + Mini^3 with a modified power supply, but since current is a bit tight, I can stand dropping a channel.

 I'm going to need help figuring out how to do the current draw calculations. I really don't know where to start. Each chip is going to sink some sort of quiescent current as well as operating current, then there's the current going into the likely low-Z headphones. Preliminarily, let's try the AD8397 and see what kind of numbers we get.

 If things work out with rds' power supply, we'll have 12V to work with. The datasheet says max current draw at a 10V supply is 12 mA/Amp (milliamps per Ampere? What does that mean?). The PCM2702 will take at max 30 mA for the digital section and 25 mA from the analog section. That means 67 mA so far, and rds gave us 150 mA of play. That means there's a healthy 83 mA to play with, yes? Plus, one of the features of the AD8397 is that it's capable of delivering 310 mA into a 16 ohm load. Should that worry me? What am I missing from my calculations?

  Quote:


  Originally Posted by *Mellow Mushroom* /img/forum/go_quote.gif 
_why not use battery power instead?_

 

Part of it is because I don't want to have to worry about charging it all the time, and part of it is because it will be taking the signal from the BantamDAC. It would be some kind of headache trying to fit some sort of battery in there, figuring some sort of charging method, blah blah etc. I'd rather just have one wire in and one wire out, one for the DAC, and one for the headphones. It's simpler and cleaner that way, I think.


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## error401

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_If things work out with rds' power supply, we'll have 12V to work with. The datasheet says max current draw at a 10V supply is 12 mA/Amp (milliamps per Ampere? What does that mean?). The PCM2702 will take at max 30 mA for the digital section and 25 mA from the analog section. That means 67 mA so far, and rds gave us 150 mA of play. That means there's a healthy 83 mA to play with, yes? Plus, one of the features of the AD8397 is that it's capable of delivering 310 mA into a 16 ohm load. Should that worry me? What am I missing from my calculations?_

 

I'm not sure how rds is planning to get 150mA at +/- 12V out of USB. That's 150 x (30/5) = 900mA drawn from USB (max 500mA). And the converter he's planning to use is only 2W, while 0.150 x 30 = 4.5W. Realistically you'll probably get closer to 75mA at the +/-12V rails, and that's with nothing on 5V.

 You need to calculate all the currents with respect to 5V. When you boost the voltage on the output side, you also boost the current on the input side. This comes from the power formula, P=IV. If you increase V but maintain I, power increases proportionally. Since the input of the device needs to provide the same power but at a lower voltage, I increases proportionally on the input. For linear regulators you can assume that the current drawn from the unregulated rail is the same as the current drawn from the regulated side (and the power difference is burned in the regulator).

 So here's what you've got: AD8397 draws 15mA max when powered from 24V, and you've got two of them, so 30mA. Reflect that onto 5V and you get ~180mA from the USB bus. PCM2702 takes 30mA on 3.3V and 25mA on 5V (max) which you can just add, so you're up to 235mA. I wouldn't worry too much about dynamic currents, the capacitors in the supply will source/sink most of that current, and the average load current is going to be very small. I think it can be safely ignored.


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## joneeboi

Was it +/- 12V? I thought he meant 12V. Also, I only have one AD8397 since it's dual channel, yah? With one less opamp, that halves the current from 180mA to 90 mA plus the contribution from the DAC, which yields *145mA*.

 15mA * (30/5) = 90mA
 90mA + 55mA = 145mA

 I'm a little confused about that (30/5) conversion you're doing though. There aren't any units next to the 30, but I think we can safely assume you mean 30V. And if that's the case, why isn't it 24V? Is it because he's boosting it to 30 and shaving it down to 24?

 edit: Hm, it seems I just missed the fact that I had 1337 posts. Shucks.


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## error401

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_Was it +/- 12V? I thought he meant 12V. Also, I only have one AD8397 since it's dual channel, yah? With one less opamp, that halves the current from 180mA to 90 mA plus the contribution from the DAC, which yields *145mA*._

 

If it's the same USB power supply I'm thinking of, he plans +/-12V.

 The Iq is per amplifier on a dual. That's what the mA/Amp means.

  Quote:


 I'm a little confused about that (30/5) conversion you're doing though. There aren't any units next to the 30, but I think we can safely assume you mean 30V. And if that's the case, why isn't it 24V? Is it because he's boosting it to 30 and shaving it down to 24? 
 

Yea I thought that might've been missed. Your assumption is correct, basically the linear regulator that gets it down to 12V is going to draw approximately the same current as it's loaded with from the 15V supplies, so it's easier to just use the input voltage for the math. If you prefer, you could calculate the load at 24V and then factor in the efficiency of the LDO, but you'd end up at about the same result.


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## millwood

you also need to factor in a) the idle current of the dc-dc convertor (30ma for dcv010512, from a 5v source), b) its inefficiency (<85%, lower for low load situations), and total watt output (<1w for dcv010512).

 so your headroom is tightening quickly.


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## cobaltmute

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_I definitely wouldn't use such a supply for audio._

 

Any reason why you would not use something like a charge pump to create an negative rail?

 There is the switching noise, but IIRC they are much more efficient than the the boost convertors people seem to be wanting to use. As well you can get them to have high switching frequency (i.e MAX889T) to try and keep the noise out of the audio band.

 the other thing that it does is simplify the ground. USB ground will be ground all the way through the circuit as opposed to having one ground through the DAC section and then one virtual ground in the Headphone section.

 I think ultimately you could build a Mini^3 + BantamDAC USB powered in one box this way pretty easily.


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## rds

Quote:


 If it's the same USB power supply I'm thinking of, he plans +/-12V. 
 

No I don't plan +/- 12V. There's no point in trying to get that kind of voltage off a usb. The current would be useless as you pointed out.
 I'm using one output of the DCP020515DP. I want a single 12V supply.
 That means we can draw 148 mA at 15V and 89% efficiency. The ldo is rated at 150mA as well. I estimated the upper limit and 150mA for this reason. Maybe I'm pushing it. But for sure 140mA is reasonable.
 It does require the builder to think about current draw if they're getting close to the 140mA mark, but as an example you could even build a 12V PPAv2 with the buffers biased at 25mA (near the max) and you'd be OK. 
 So it will be pretty robust in terms of powering headphone amps.


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## millwood

Quote:


  Originally Posted by *cobaltmute* /img/forum/go_quote.gif 
_Any reason why you would not use something like a charge pump to create an negative rail?_

 

they have next to nothing in terms of current capability, and high output impedance, two things critical to a high quality audio amp.


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## cobaltmute

200ma is not sufficient for this?


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## rds

Quote:


 they have next to nothing in terms of current capability, and high output impedance, two things critical to a high quality audio amp. 
 

Also consider that the really crappy power only applies to one rail. So you have one rail that is pretty robust (the usb) and one that is garbage. If you use that kind of asymmetrical power for an op-amp you can bet the results will be less than awesome.


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## joneeboi

What about the TI DCV010505D (datasheet: http://focus.ti.com/lit/ds/symlink/dcv010505.pdf)? It gives a +/- 5V supply with 100 mA on each rail. That sets ground at USB ground which allows us to safely connect the DAC, amp and case together as the ground, gives us more current to work with, and is more efficient than using one rail on a dual rail chip (right?). Am I reading that right? Is it 100mA on each rail or for both? I guess another drawback is its 1W rating and low stock at Mouser and Digikey.

 I'm wondering, if we set a virtual ground at 6V, will the volume knob short against the case?


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## rds

Quote:


 200ma is not sufficient for this? 
 

At this point in time charge pumps are used almost exclusively for digital supplies where the various non linearities, noise, and v-droop are not an issue.
 If you want to use one, no one is stopping you. But consider that circuit designers won't use these in even the lowest quality of analog circuits.
 Besides that, the your bipolar supply would be totally asymmetrical.


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## rds

Quote:


 What about the TI DCV010505D 
 

It should be able to provide 100mA on each rail max. But compare the performance curves of the dcp and dcv. The output ripple for dcp at the 140mA max we'll be using is about 20mV with a 1uF cermanic. Now for the dcv using 70mA per rail there's about 35mV ripple with a 1uF cap. The Vout also drops much more steeply in the operating range we'd be using for the dcv than the dcp. So you really need regulation and the most you could regulated is +/- 3.3V. So you see that in the end you don't gain a lot of voltage.

 It's also worth mentioning that 35mV ripple on each 5 V rail is far more significant than 20mV ripple on a single 15V rail. Think of the ripple to DC ratio.

 The reason I would prefer a single supply is that most of the amps we'd be using this with take a single supply.

  Quote:


 That sets ground at USB ground which allows us to safely connect the DAC, amp and case together as the ground, 
 

I think you're getting too caught up with the idea of 'ground'. The ground out of the converter is not 'at usb ground' it is totally isolated. It is at whatever potential you connect it to, and the rails are just +/-5V of that potential.


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## error401

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_No I don't plan +/- 12V. There's no point in trying to get that kind of voltage off a usb. The current would be useless as you pointed out.
 I'm using one output of the DCP020515DP. I want a single 12V supply.
 That means we can draw 148 mA at 15V and 89% efficiency. The ldo is rated at 150mA as well. I estimated the upper limit and 150mA for this reason. Maybe I'm pushing it. But for sure 140mA is reasonable.
 It does require the builder to think about current draw if they're getting close to the 140mA mark, but as an example you could even build a 12V PPAv2 with the buffers biased at 25mA (near the max) and you'd be OK. 
 So it will be pretty robust in terms of powering headphone amps._

 

My mistake, I apologize. I'm not sure you can just ignore the second output and expect to get 2W out of one half of it.


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## joneeboi

The TI notes in the datasheet say you can hook them up in parallel to double current capability.


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## error401

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_The TI notes in the datasheet say you can hook them up in parallel to double current capability._

 

I'm not sure that will work with the dual chips. There's only one transformer in the dual chips, with a modified rectifier configuration. I think you'd end up with a shorted secondary.


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## rds

No it will not work, becuase the output ground is common.

 But it looks like you're right about about the current limit. We can only draw a max of 66mA per output on the +/-15V chip.

 It seems the only way to get a decent current and voltage is to use two DCV010515. That will give 134mA into 15V. However, it's a little cost prohibitive at $20 for the 2 chips.






 EDIT I will stubbornly go ahead with the +/-15V chip I already ordered and make a +/-12V supply that can supply 37mA per channel at usb 2.0 specs. That'll be cutting it really close for a pimeta with lmh6321. But we'll see what happens.

 The 2 chip supply mentioned above is a good alternative to my original 15V idea, and I will try that at some point.


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## joneeboi

In the spirit of redesigning my own HPDAC-type board, why not use the same DC booster the HPDAC did, the TPS61040? The parts count would be a bit higher, but it comes in 250mA and 400mA packages while showing great stock at Digikey and Mouser. It's configurable up to 28V, so we can set it just above whatever filtered and regulated voltage we wanted. I mean, all the info is on dsavitsk's site for us to use...


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## rds

The HPDAC looks like a nice project. If you want to duplicate it why not just ask dsavitsk for the pcb files?

 I'd like to try something different and my plan is still to make a usb pimeta with bantam dac. 
 I will probably end making the two chip supply at some point, and swapping out the +/- 12V, unless of course it works perfectly.
 Even still I will probably still try the 12V 130mA supply - which would be nice because it's not so application specific.


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## millwood

Quote:


 Also consider that the really crappy power only applies to one rail. 
 

you can easily create dual rails (or quad rails if you wish) from a charge pump.

 they just don't hold their rails that well under a dynamic load.


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## millwood

Quote:


 What about the TI DCV010505D (datasheet: http://focus.ti.com/lit/ds/symlink/dcv010505.pdf)? 
 

TI offers three families of those tiny dc-dc converters.

 the first one is the dcp01/02, using bipolar processes. there is the regulated version in dcr (3.3v/5v only), and then the new dcv (bicmos) for higher efficiency.

  Quote:


 is more efficient than using one rail on a dual rail chip (right?). 
 

you are right on that one.

  Quote:


 But compare the performance curves of the dcp and dcv. 
 

if you look at the ripple charts later in the datasheet, they have fairly comparable ripple performance and regulation as well.

  Quote:


 I think you'd end up with a shorted secondary. 
 

the difference between the dual and single Vout versions is just full wave rectification vs. half wave rectification.

  Quote:


 TPS61040 
 

that is non-isolated so if you mess up on the boost side of the circuitry, you could get your computer / usb ports damaged.

 ON has a few nice parts like the TPS61040 in sot23-5 packaging - it helps greatly with board real estate.


----------



## rds

Quote:


 TI offers three families of those tiny dc-dc converters.

 the first one is the dcp01/02, using bipolar processes. there is the regulated version in dcr (3.3v/5v only), and then the new dcv (bicmos) for higher efficiency. 
 

You should make sure you read things carefully before you start giving advice.
 All 3 are cmos/dmos. The dcv is rated to higher isolation voltage. The dcp02 is higher wattage and has better load regulation. The dcv is not the new dcp02. In fact, there's no reason for us to use it as we don't need huge isolation voltage.

 The better load regulation of the dcp02 is why the performance curves look better - they are better.

 I don't mean to sound like a jerk, but it is kind of annoying when people jump in and start saying this stuff in very matter of fact way when they don't have their facts straight.


----------



## error401

Quote:


  Originally Posted by *millwood* /img/forum/go_quote.gif 
_the difference between the dual and single Vout versions is just full wave rectification vs. half wave rectification._

 

Yea. And when you connect the two half-wave rectified outputs together, you short the secondary through the two diodes...

 It's unfortunate there isn't a more appropriate voltage output for them, I remember having the same problem picking one when I did it. Even a single-output at 15V, 2W would be much better than this.

  Quote:


 why not use the same DC booster the HPDAC did, the TPS61040? 
 

Virtual ground.


----------



## millwood

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_You should make sure you read things carefully before you start giving advice._

 

we all could use some of that, right?

  Quote:


 All 3 are cmos/dmos. 
 

I think TI would beg to differ. here is exactly what they said:

  Quote:


  Originally Posted by *TI AN: sbva013a.pdf* 
_The DCP01*B*, DCV01, and DCP02 are three families of miniature DC/DC converters providing an isolated unregulated voltage output. All are fabricated using a CMOS/DMOS process with the DCP01B replacing the familiar
 DCP01 family that was fabricated from a bipolar process. The DCP02 is essentially an extension of the DCP01B family providing a higher power output with a significantly improved load regulation, and the DCV01 is tested to a
 higher isolation voltage._

 

so is that enough to establish the fact that dcp01 (no *B*) is a bipolar process?

 As to dcp02/dcv01, well, here comes from their datasheet:

  Quote:


  Originally Posted by *TI datasheet for DCV* 
_The circuit design utilizes an advanced BiCMOS/DMOS process._

 

 Quote:


  Originally Posted by *TI datasheet for DCP02* 
_The circuit design uses SYNC pins together, taking care to minimize the an advanced BiCMOS/DMOS process._

 

I would take a wild guess that *Bi* in BiCMOS means *Bi*polar?

  Quote:


 But compare the performance curves of the dcp and dcv. The output ripple for dcp at the 140mA max we'll be using is about 20mV with a 1uF cermanic. Now for the dcv using 70mA per rail there's about 35mV ripple with a 1uF cap. 
 

here is a comparison of two particular chips, dcp020505 vs. dcv010505, straight out of TI's datasheets for those respective chips.

 at 50% load, for 1uf cap, dcp02 has a ripple of <25mv, and dcv01 has a ripple of ~18mv (my estimate). so ~18mv is quite comparable to <25mv, right?

 at 100% load, for 1uf cap, dcp02 has a ripple of <50mv and dcv01 has a ripple of ~50mv. so ~50mv is quite comparable to <50mv, right?

 so how do we recouncile your numbers to TI's?

  Quote:


 The dcp02 ... has better load regulation. 
 

let's talk about regulation.

 look at the 2nd attachment. from 20% load to 100% load, dcp02 has a regulation of 6% (106% to 100%), and dcv01 has a regulation of 8% (108% to 100%). better? yes. material? probably not.

 and if you look a few pages earlier, both chips are quoted to have 1% regulation (constant Io).


  Quote:


 The dcv is not the new dcp02. 
 

nobody said it is. better reading would have helped here.

  Quote:


 In fact, there's no reason for us to use it as we don't need huge isolation voltage. 
 

nor the higher wattage? nor the 2% better regulation? ... 
	

	
	
		
		

		
		
	


	




  Quote:


 I don't mean to sound like a jerk, but it is kind of annoying when people jump in and start saying this stuff in very matter of fact way when they don't have their facts straight. 
 

agreed. having your facts straight does help.


----------



## millwood

Quote:


  Originally Posted by *error401* /img/forum/go_quote.gif 
_Yea. And when you connect the two half-wave rectified outputs together, you short the secondary through the two diodes..._

 


 I have a very difficult time understanding how that could be the case.

 could you elaborate please?


----------



## joneeboi

Not to be thwarted by power supply complications, I gave it a bit more thought and I'm wondering what all your reactions are to putting two TI 5V-to-9V DC boosters DCP020509P's in series and dropping it to 15V with Fairchild's KA78R15CTU (datasheet: http://www.fairchildsemi.com/ds/KA%2FKA78R05C.pdf). It seems that if we want to use isolated boosters, you either have to pay through the nose for lots of power or use multiple chips either in series or parallel. rds is going with two DCP020515DP's in parallel because he wants to drop it to 12V with the TL750L12CLP. If I go with the DCP020509P, I get 222mA right off the bat, and putting two in series gives me a substantial 18V. I imagine the ripples will superimpose themselves over the DC signal which will double my output AC voltage, but the output capacitors and LDO can be configured so as to care of that (right?). I figured the LDO should have a higher current rating than the DC booster so as to not waste precious resources. I'll have to figure out how to filter the 800kHz switching noise, but that'll come after figuring out which devices I want to work with.

 What do you guys think?


----------



## millwood

Quote:


 but the output capacitors and LDO can be configured so as to care of that (right?). 
 

the chips oscillate at 400khz (800khz/2) and the ripples will be in that territory as well.

 most regulators and eletrolytic capacitors are useless at that kind of frequency.

 if you really want to lower ripples, try a pai-filter or something like that for high current application, or a simple crc filter if you are sure that the current drop isn't going to be significant here.

 don't take my words on that: TI has an application note on how to reduce ripple for those chips.


----------



## rds

Quote:


 so is that enough to establish the fact that dcp01 (no B) is a bipolar process? 
 

Yes, the DCP01 *was* a bipolar. It is not longer produced. All the chip types are now CMOS/DMOS. Referring to the DCP01B as DCP01 is perfectly acceptable as there is only one DCP01 now - that is the non bipolar one.

  Quote:


 the first one is the dcp01/02, using bipolar processes. 
 

So this is wrong

  Quote:


 I would take a wild guess that Bi in BiCMOS means Bipolar? 
 

Yes it refers to a bipolar bjt and cmos in one package. It does not refer to the chip being made using a bipolar process.

  Quote:


 nor the higher wattage? nor the 2% better regulation? ... 
 

Read my post - I'm referring to the DCV. The DCV is 1W. The DCP02 is 2W and better regulated.

  Quote:


 nobody said it is. better reading would have helped here. 
 

Read the last page, it is there (not from you, some else).

 You are also incorrectly referring to the ripple at 50% when I was referring to it at 70%. 

 I'm not going to bother refuting you point by point anymore. You've done a great job of making this very confusing for anyone trying get some factual information from this thread.

 I hope you can stop spamming this thread with nonsense.


----------



## rds

Quote:


 If I go with the DCP020509P, I get 222mA right off the bat, and putting two in series gives me a substantial 18V 
 

That sounds like a good idea. Just remember that the usb bus limits you to about 105mA at that voltage.

 A pi filter between the dc-dc and ldo is the best way to get rid of ripple.
 As I suggested earlier this choke with these ceramic caps on either side will make a very appropriate pi filter for this application.

 This Murata DC-DC converter is a very good isolated alternative to the ti chips. This will allow you to have 140mA at 15V using a single chip.


----------



## joneeboi

Deep breaths all around.

 Hm, I forgot about doing the power conversion. Where is that 105 coming from? I get,

 P = V1*I1max = V2*I2max
 (5V)(500mA) = (18V)*I2
 I2max = 138.9mA

 But I guess

 2W = (18V)*I2
 I2 = 111mA

 and I shouldn't try to get to that limit. I knew I was missing something with the higher voltage. I looked at that Murata unit, but it has 5 stock and a 20-week factory lead time. It has the higher power rating and a nicer end voltage and price than the two chip method. I should probably keep myself busy for the next five months then, eh? 
	

	
	
		
		

		
			





 Ending up with a 10V or 12V regulated supply wouldn't be all bad.

 I'm just going to continue thinking out loud so that people can correct me or give input where necessary.

 Current needs:
 55mA for BantamDAC
 Suppose AD8397 as opamp choice. Max current draw is 30mA.

 Max power:
 P = (5V)(500mA) = 2.5W

 Set voltage boost with (5V)(500mA) = V2*I2 to get max current output:
 V2 = 15V allows I2 = 166mA
 V2 = 12V allows I2 = 208mA

 Leftover current for PS sections:
 V2 = 15V leaves 81mA
 V2 = 12V leaves 123mA

 Keep in mind inefficiency and tolerances.

 Some candidates for DC boosting:
 15V

Cincon EC3AE03M
EC3AE03M
 Efficiency 61%, no load current draw 120mA (!!!)
Murata NDTS0515C
NDTS0515C
12V

Murata NDY0512C
NDY0512C
 Efficiency 73%, no load output current 33mA, input current full load 533mA (yikes),
Murata NDTS0512C
NDTS0512C
 Efficiency 76%, min output load current 63mA, max input current 769mA
Murata HL02R05S12YC
HL02R05S12YC
 Efficiency 69%, min load input current 70mA, max input current 580mA
Murata HL02R05S12ZC
HL02R05S12ZC
 Efficiency 69%, min load input current 70mA, max input current 580mA
Components for PI CLC filter:
C330C105K5R5TA
PLY10AN1121R8R2B

 Humbug.


----------



## millwood

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_Referring to the DCP01B as DCP01 is perfectly acceptable as there is only one DCP01 now - that is the non bipolar one._

 

I'm not going to bother refuting you point by point anymore. You've done a great job of making this very confusing for anyone trying get some factual information from this thread.

 I hope you can stop spamming this thread with nonsense.


----------



## millwood

Quote:


  Originally Posted by *rds on what BiCMOS is* /img/forum/go_quote.gif 
_Yes it refers to a bipolar bjt and cmos in one package._

 

taking a class on semiconductor processes would great benefit your knowledge and save all of us more confusion.

 "bipolar bjt"? as supposed to bipolar MOSFET, or CMOS bjt? what do you think that "b" in "bjt" stands for, rds?

 no answer is needed, 
	

	
	
		
		

		
		
	


	




.


----------



## rds

Quote:


 Where is that 105 coming from? 
 

You need to multiply by the efficiency of the dc-dc converter and the voltage it outputs (~.85, and 20 respectively):

 (5V)(500mA)*0.85 = (20V)*I2

 ~105mA

 Remember that is assuming you aren't drawing any power for the DAC.
 So (5V)(450mA)*0.85 = (20V)*I2

 ~95mA

 I really like that 15V Murata for the pimeta with lmh6321 since it draws about 60mA and the min current for the Murata is 50mA.
 Also on USB 2.0 it allows for 130mA at minimum efficiency.
 I may end up ordering one of those too


----------



## millwood

you may want to do the math backwards.

 out of your usb, you get 5v 500ma max.

 of that, the dc-dc converter takes 40ma (at 5v) per dcv010512D. so you have 5v 460ma (2.3w usable) to be converted.

 the converter efficiency is about 50 - 80% in the 30% load - 100% load range so let's assume 75% efficiency. that means you have 2.3w*75%=1.7w available on the output.

 at +/-12v output, that leaves you 1.7/24=70ma both rails.

 math for the rest is simple.

 obviously, it doesn't make sense to use such a high voltage for headphone amps but the math is similar.

 btw, ad8397 idles at 7ma/amp typical and 8.5ma/amp max. where did you get the 30ma figure?


----------



## millwood

Quote:


  Originally Posted by *millwood* /img/forum/go_quote.gif 
_btw, ad8397 idles at 7ma/amp typical and 8.5ma/amp max. where did you get the 30ma figure?_

 


 I figured that out: i was looking at the wrong page, 
	

	
	
		
		

		
		
	


	




.

 the 30ma figure is correct for +/-12v.


----------



## error401

Quote:


  Originally Posted by *millwood* /img/forum/go_quote.gif 
_I have a very difficult time understanding how that could be the case.

 could you elaborate please?_

 

Standard centre-tapped full-wave rectifier, as in the datasheet:





 Standard centre-tapped half-wave doubler, as we can assume is being used:





 Circuit above with the outputs connected together:





 Not a dead short but, uhm, I wouldn't want to wire it up and apply power...


----------



## joneeboi

Come on, guys, deep breaths all around.

 I probably won't go with 24V, but thanks for the math help, fellows. I knew I had to factor in the current draw of the booster circuit, but I was just mixed up about the pre-boosted and post-boosted currents.

 *more thinking out loud*

 The NDTS0515C outputs 50mA with no load, meaning it draws 197mA from the input at minimum.

 I1*(5V)*0.76 = (15V)*(50mA)
 I1 = 197mA
 I(leftover) = 500mA - [I1 + I(DAC)] = 500mA - 197mA - 55mA
 I(leftover) = 248mA
 (248mA)*(5V)*0.76 = (12V)*I2max
 I2max = 78mA

 At 10V, the AD8397 draws 24mA in stereo configuration. This converts to 76mA at the input, so total current draw so far is 288mA from the USB. The TL750/751 datasheet doesn't mention anything about its quiescent current, but we still have plenty of headroom, it seems. It has a maximum output current of 150mA, so we should be quite safe there. But just to make sure,

 I1*(5V)*0.76 = (15V)*(150mA)
 I1 = 592mA
 I(total) = 647mA

 General equation for future use is

 I1 = (3/0.76) * I2

 I don't think we could get that kind of current with the amplifier, but now I'm wondering what happens when headphones are plugged in and unplugged from the jacks. What kind of current spike is happening there? Maybe I'm being paranoid. I haven't really seen a discussion about it yet except for in the PPAv2 "Parts Selection" section for the output transistors. Google hasn't really turned up much info either, so I'll take the general silence to mean that I don't really have to worry about it.

 Hm, does that mean I have one possible configuration lined up? Must let information settle before continuing...


----------



## millwood

Quote:


  Originally Posted by *error401* /img/forum/go_quote.gif 
_Not a dead short but, uhm, I wouldn't want to wire it up and apply power..._

 

I thought we were talking about paralleling the chips / 2ndary windings of different chips, not paralleling 2ndary windings of the same chip.


----------



## millwood

I don't know if your interpretation of "minimum load current" is accurate. the way I read the datasheet, it is saying that converter has to have a minmum load of 50ma to work properly. that 50ma is going to be satisfied, likely, by your opamp idle current + other load, and if anything, you can parallel a resistor to generate the rest.

 if you do that, you don't need to double count the minimum load current.

 the datasheet doesn't, unfortunately, provide the idle current for the converter itself or an efficiency curve to help us estimate that.

 so if you stay with the 15v side, you have a current draw of 50ma (which will include your opamp + dummy resistor load), maybe a few ma for your linear regulator and you are looking at maybe 60ma.

 @ 15v, that's a power dissipation of 60*15=900mw.

 at this kind of load levels, your efficiency will be much lower than 77% specified in the datasheet. it is likely in the 50% - 60% range. let's take 50% for now.

 that means your usb side will have to provide 900mw/0.5=1.8w. At 5v, that means a current draw of 1.8w/5=360ma.

 maybe your dc-dc converter needs to draw another 40ma at idle so you have 100ma (500ma-360ma-40ma) to spare.

 the real numbers are likely in the ball park, I think.

  Quote:


 now I'm wondering what happens when headphones are plugged in and unplugged from the jacks. What kind of current spike is happening there? 
 

a PROPERLY designed headphone amp will always have a resistor OUTSIDE of the feedback loop exactly for such occasions - however, I have seen lately plenty examples of poorly designed headphone amps in that regard, 
	

	
	
		
		

		
		
	


	




.

 the short taken place when the phone is being plugged into the amp is likely going to last a "long" while (a few ms to a few hundred ms?), they are more like a true DC short from the amp's perspective.

 if your amp is not properly designed, the amp will try to maintain a voltage over a short. a few things may happen:

 1) the amp's protection circuitry kicks in;
 2) the amp's RE resistor, if it has one, took the bulk of the fall.
 3) the output transistors get destroyed,
 4) the rail voltage droops to a point that it saves the amp.
 ...

 I would never use a headphone amp that does NOT have an output resistor OUTSIDE of its feedback loop.


----------



## rds

Joneeboi-

 The maximum efficiency of a dc-dc converter is rated for its maximum output current. 
 Since the converter has a load independent current draw the proportion of output to input at low currents is very poor.
 The nice thing about efficiency is that it is defined as the power output over the power input. So many of these other calculations are pointless. Once you're drawing about 40% of the maximum load the efficiency doesn't change a lot. So for a 77% efficient converter it is safe to assume about 73% efficiency at 50% load.


----------



## cobaltmute

There is always this


----------



## millwood

Quote:


  Originally Posted by *cobaltmute* /img/forum/go_quote.gif 
_There is always this



_

 

the foundamental notion of this thread is that 5vpp swing out of a single 5v rail isn't enough.

 I think for a lot of occasions, you don't need more than a volt or so to get decent volume. think about it this way: the cmoy that everyone loves uses a chip that can deliver 40ma. that's about 600mv into a 16ohm headphone!

 and most people haven't complained about its lack of power or loudness.

 I pointed this earlier, in the end, you are likely getting nothing for going to a complicated solution to produce higher rail voltage than what's available straight out of a usb, at the added costs, noise, board real estate and complexity.

 often time, a simpler solution is the best / better solution.


----------



## millwood

another approach that I mentioned earlier, if you want high voltage, split rails but don't need isolation, is to get both +/- rails from one single smps.

 an example of how this can be done is in the cs5171 datasheet, figure 47 - but the basic concept applies to any other boost converter and you can use any of your favorite boost (or actually buck, if you need to step down) chips.


----------



## joneeboi

No, I haven't lost interest in this design. I have exams to attend to, so please don't take my silence as my surrender to the design obstacles.

 I'm thinking of stepping up to 12V and regulating to 10. With a generous 40mA draw for the opamp and regulator,

 40mA * 12V = 0.48W in the booster
 40ma * 12V / 5V / 60% = 160mA from the input with a paltry 60% efficiency.

 I think that leaves plenty of room. I think there's plenty of current left for a decent two-channel amplifier.


----------



## rds

Quote:


 No, I haven't lost interest in this design. I have exams to attend to, so please don't take my silence as my surrender to the design obstacles. 
 

Same story here. I've got a design using Murata components that will give lots of headroom. I will build it Sunday or early next week.
 Unfortunately I might not be able to measure it until January 5th as the prof who I was counting on to let me into the lab will be away over Christmas break. 
 Anyways I'll post details as it comes together.


----------



## rds

I just spoke to the lab tech and he'll let me in next week. So I'll be able to do measurements 
	

	
	
		
		

		
		
	


	



 Not sure that anyone's really following this or interested, but just in case there's the update.

 I think it'll be handy to have a simple booster schematic, bom, and most importantly measurements. It'll allow people to figure out whether the booster can work for what they want to do and also whether it has the quality they're looking for.


----------



## joneeboi

I've been doing some thinking, and it might be worth investigating the merit of 5V opamps. There are lots of low-voltage, battery-powered amps out in the wild, eg. cell phones, MP3 players, and a lot of them don't sound all that bad. Even a bunch of DACs are able to drive low impedance headphones, so maybe there's something to the low voltage, rail-to-rail opamps out there. I think this amp board would have enough space for 5V-regulated-to-4.75V opamp operation and a boosted opamp section with the choice belonging to the builder. Will continue to investigate low voltage opamps.


----------



## rembrant

I still think the voltage booster idea has merit. I'd rather not make too much of a compromise. 

 I have one question though. No one seems to use lithium batteries at all. You would think that with a nominal voltage of 3.6v and zero memory everyone would be all over them. I see people state that they only have a 500 recharge limit. Honestly, that is not the case. You can and should charge them anytime you are able to. No waiting for them to discharge. If you don't discharge them all the way (2.8v) which you wont most of them time. They will last many thousands of cycles. Most cellphones use lithium now. I don't see many people complaining about the batteries unless they are the kind that never charge their phone. You will ruin a lithium battery in short order by not keeping it charged.

 The charging circuit is very simple and can be built into the amp power supply for home use and there will be no worries about over charging the batteries even if it is plugged in forever. The charger is basically a voltage and current regulated power supply. It has all of five parts. 2xlm317 adjustable regs and 3 resistors.


----------



## cobaltmute

The blowing up issue has people concerned.

 Look at the troubles that some people have building their amps as it is, and then look at that in context of something that can blow up.


----------



## joneeboi

The reason I'm not going with batteries is because I won't be using my DAC/amp box without my laptop, so the only batteries I need are in my laptop. My audio source will be the BantamDAC, and that won't work without the USB. I just wanted to make a decent-quality, USB powered headphone amp that does away with the batteries and whatever minimum hassle there is associated with batteries. If I didn't mind the batteries so much, I'd go with a gamma1+Mini^3 setup like n_maher. All in all, the difference isn't all that great, but combine my desire to design and produce my very own board with my preference for a simple setup in a single Hammond 1455C80x, I will likely continue on this path. In reality, I could just as easily breadboard a preliminary amp running on regulated USB power at 4.75V to an AD8656 since it really is a much simpler solution. Beyond that, I want to see how far one can push the limits of the USB power in terms of higher-quality-than-onboard-soundcard audio since it doesn't seem to be a well-explored route. error401 and MWP are just some members that have completed the circuit, but that is a fairly small proportional of the DIY headphone amp community. Trail-blazing ftw!


----------



## cobaltmute

Running off the laptop have you thought about overall battery life? I've noticed that when running with gamma1 attached, I do see a difference in battery life on my X61.


----------



## joneeboi

No, I haven't, but I've always used my laptop by a wall outlet and plan to continue doing so. I realize that there is a potential for plugging in a wallwart for my headphone amp if I'm always by an outlet, but I've carried around a pluggable PIMETA before with my laptop and it was nothing short of annoying with a mix of troublesome. One wire from the wall which is going to be there anyway, one wire from the laptop, one wire to my ears.


----------



## rembrant

Quote:


  Originally Posted by *cobaltmute* /img/forum/go_quote.gif 
_The blowing up issue has people concerned.

 Look at the troubles that some people have building their amps as it is, and then look at that in context of something that can blow up._

 

Again, this is another misconception. The fires that you hear about stem from the manufacturer using the batteries way out of spec or very near the maximum current draw. For most of the amps here we are talking less than 1c draw on a battery that is good for 10 to 20c. Don't forget that most of them now come with PCB protection on the cell from the factory. Most people have one on their hip for 12hours a day. I would say that we are well within the safe zone. LiFe cells are also available. Those where specifically built with safety in mind. The power density isn't at the same level as with lithium polymer but it is a small price for absolute stability.

 If you are saying that people might short the battery terminals then obviously you have never shorted the terminals on a Nicd or NiMH battery either because they burn rather spectacularly as well.


----------



## rds

It's an interesting point rembrant, but seems unrelated to building a _usb powered_ amplifier


----------



## error401

Quote:


  Originally Posted by *rembrant* /img/forum/go_quote.gif 
_The charging circuit is very simple and can be built into the amp power supply for home use and there will be no worries about over charging the batteries even if it is plugged in forever. The charger is basically a voltage and current regulated power supply. It has all of five parts. 2xlm317 adjustable regs and 3 resistors._

 

I don't think I'd ever trust such a circuit to charge a Lithium-based battery. Certainly not in a DIY project I release to the wild. The fact that lithium batteries are more dangerous than other types is absolutely not a myth. They are much more sensitive to charging conditions than most other types, and even over trickle-charging them can start fires. I've considered using them in the past, and may still for my own projects, but I don't think I'd ever release that portion of anything I do in any detail. It's simply too easy to cause damage with this due to build errors, user errors, or just plain clumsy probing or whatnot. The one exception would be 'standard' sized cells that can fit in an external charger and internal battery holder. That would eliminate much of the danger, but it's also much less convenient.

 I think I have seen some reports of people using lithium chemistry batteries for portable amps, it's just not something that the mainstream designers have recommended (yet?). My guess is that this is primarily due to the fear of inexperienced DIYers causing serious harm, but the greatly increased complexity of the charging circuit can be a bit size prohibitive in a DIY context as well. As I said, I looked into this, and doing a proper LiIon charger sticking to TH parts was quite large in board area, as was keeping to large pitch SMD. A 'hacked' circuit in such a critical context is unacceptable IMO.

 But yea, totally off-topic, sorry to continue to derail the thread, but I've written the post now...


----------



## rembrant

My posts where not meant to derail the subject matter. Perhaps I should explain. It seams to me that with case real estate being diminished already by the components required to increase the voltage to the desired level as well as the DAC and the thought of only being able to use the amp while tethered to a PC, that the smaller the battery the better. With some type of internal battery in the design you would have to option of using the device as a portable amplifier as well.


----------



## joneeboi

I'm not really in the market for a portable amplifier. If I were, I'd instantly run to the Mini^3, but that's the reason I got the iPhone 2G. I could very well carry an amp around, but it's just not worth the trouble for my tastes. I'm usually stationed at a table when I study and do homework, so using it with my laptop would be more ideal than carrying the amp around. I was carrying around an iPod touch 1G and a Treo 680 in the same pocket for a month before I got the iPhone. I decided then and there that portable was meant to be portable and got an iPhone; each day's pockets were different from the last, and carrying two physically distinct devices in one pocket was tough on my sense of pragmatism. I'm not really looking for a portable amp, and if I were, I'd be using the Mini^3.

 I'm now wondering about the merit of isolating the DC/DC converter. I'm looking at this TI TPS6734 and it seems to have almost everything I'm looking for besides being isolated. From what I understand, the isolation is meant to protect the USB from ... something. Mistakes? Couldn't a fuse do the same thing? With this TPS6734 regulator, it gives me 120mA output at a pretty solid 12V which I wanted to regulate down to 10V. At 12V with a full output current of 120mA at 85% efficiency, that draws 338.8mA.

 I1 = (12V/5V)*(120mA)/85%
 I1 = 338.8mA

 That's plenty of room to play with. I know dsavitsk mentioned some reservation about inrush current in error401's USB-powered amp thread, and this one has a soft-start feature (see Figure 4). It seems almost too good to be true, so I'm wondering what I'm missing. The TPS6734 has the right input and output voltages with a respectable current capability and efficiency, it's in a smaller package at a quarter of the price, plus it's readily available. There is the bit about it not being isolated, but the HPDAC seemed to have survived well enough without the isolation. I am still planning on designing on a single supply with virtual ground, so I'm wondering what precautions I have to take if I do go this route. For prototyping, I could throw a fuse onto the board before applying power, which would at the same time give me a convenient place to check current draw on a DMM if it doesn't blow. What do you guys think?


----------



## joneeboi

Hm, I think that I would be shorting 5V to ground. *sigh* I will look into split supplies as an alternative. I can probably find other suitable isolated DC/DC converters, but I should do a little research thisaway before going ahead.


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## error401

The isolation is useful because you'll be generating a positive voltage. With a virtual ground, you have to be very careful about what you connect your amp to. Most gear attaches ground to earth at some point, so you'd be effectively connecting your virtual ground (at 1/2Vcc in relation to earth ground) to earth. Not a good situation. With the isolation, the virtual ground (if you use one), or the centre-tap on those DCP02s will float, and the next stage can pull it where it needs to be. Much safer.

 Most (I'd hazard to say all, but I'm sure some super cheap motherboards don't) USB ports will limit current. I've shorted mine many times, and the current limit on them is somewhere around 1.5A (on my board). You shouldn't need to protect the USB ports, and inrush current isn't a big deal because it will be limited by the USB port.


----------



## rds

Isolation is also used to reduce the noise transmitted from the dc-dc converter. That is one reason why the high quality converters have transformers.
 The Murata seems very good, but did cost $20 CND. I'll get the power supply built tomorrow and see how it is.


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## joneeboi

I'm wondering about the BantamDAC's output. Its ground will be sitting at USB V-, which is going to be the booster's negative rail. Will I not be shorting the 5V virtual ground to V- if I connect the separate grounds together, even if it is isolated? It can float to whatever value it needs to be, but would it still work if it floated right to the rail?


----------



## joneeboi

Though the DCP02 family of DC/DC converters doesn't have a 5V-to-12V model, there is still the readily available DCP01 that does have such a one. Again using the AD8397 operating at a regulated and filtered 10V as an example, there is only a 24 mA draw from the DCP010512B which can provide up to 83 mA. Full load through this particular booster means 234 mA to the USB.

 I1 = (83mA)*(12V/5V)/85%
 I1 = 234 mA

 It was asserted earlier that current from the USB could be safely ignored, but this calculation is presented for the sake of knowing anyway. Furthermore, this means that a third channel can be safely added into the mix again. Huzzah!


----------



## joneeboi

Here is what my free time has produced in the past month. 
	

	
	
		
		

		
			

























 I obtained permission from amb to use the Mini^3 amplification circuit. The voltage is boosted by the DCP010512 to 12V, filtered by a CLC LPF with a corner frequency of about 500 Hz and regulated by the TL750L10 to 10V. The virtual ground is up top. The isolated V- is on the bottom and separated from the case, but the USB ground is connected to the case.

 Is there anything that I should try/keep in mind/consider? For example, what the best way of presenting the circuit without all the JPG artifacts? Please poke the holes in my design now before I get it prototyped. I have to rush off now, so I'll expand on the design maybe next week.


----------



## rds

Nicely done!
 I don't have the knowledge to help with your pcb layout, but the implementation looks good.
 Maybe add some values for the power supply so we can see exactly what's going on there.


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## joneeboi

Something I noticed immediately after posting the pictures is that I can probably connect the virtual ground to the USB ground. The output voltage is isolated, so it float to whatever voltage no problem while I clamp down the virtual ground. That way the whole bottom can be routed as a ground plane and connected to the casing, much like the Mini^3. That should be okay, right?

 Also, I can probably snake my way from the USB power input at the back to the front for a board-mounted LED like the Mini^3. It's only drawing a couple mA, but I figure it'd be best to save the precious boosted power for the amplifier itself.

 There are lots of capacitors in the power supply just because there's room. I wonder about the inrush current of having all those capacitors. I might even be able to make them bigger speccing them for a lower voltage. For instance, the electrolytic C4+, C4-, C5+ and C5- only see half the regulated 10V, but I specced it for 16V in case of some sort of fault. It uses the same 470uF caps as the Mini^3. As you can see, I borrowed quite a bit from amb's design.

 For the line filter, I used the calculator from,

Chebyshev Pi LC Low Pass Filter Calculator

 Ripple occurs at 800 kHz, but the cutoff frequency of the CLC filter I've planned has a corner frequency of 580 Hz. Noise shouldn't be a problem as far as I know. Plug in 580 Hz, 1 ohm, 0.01 dB, and 3 components.

 The 10V regulator is an LDO type with a dropout of 0.6V at 150mA. The DCP01 drops to 11.5V at 100% load, so that shouldn't be a problem either.

 Thoughts? I think better when I do it out loud, so it helps when I can discuss with people. I have lots of little things to clean up, but I just wanted to get some of the technical stuff down pat now before it's too late. My biggest fear so far is about the isolated voltage somehow becoming +/- 5V relative to USB ground with the use of the TLE. That's what happens when you use an isolated DC booster, right?


----------



## Nemo de Monet

Well, nobody _else_ around here seems to like the idea of using USB voltage to power an amp, because they're all glass-half-empty naysayers 
	

	
	
		
		

		
		
	


	




, but I for one happen to think it's a spiffy idea.


  Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_Something I noticed immediately after posting the pictures is that I can probably connect the virtual ground to the USB ground. The output voltage is isolated, so it float to whatever voltage no problem while I clamp down the virtual ground. That way the whole bottom can be routed as a ground plane and connected to the casing, much like the Mini^3. That should be okay, right?_

 

If I understand the science correctly, that's a bad idea, and the two grounds should remain fully isolated to avoid ground loops and other less pleasant events.

  Quote:


 Also, I can probably snake my way from the USB power input at the back to the front for a board-mounted LED like the Mini^3. It's only drawing a couple mA, but I figure it'd be best to save the precious boosted power for the amplifier itself. 
 

I personally would put the LED on the isolated, boosted end of the DCP, as that way it tells you not that your computer is supplying voltage to the USB port, but that the power converter is working as it should, and hasn't gone into shutdown for whatever reason (overtemperature and undervoltage for sure; I'm not sure how it handles overcurrent.)

  Quote:


 There are lots of capacitors in the power supply just because there's room. I wonder about the inrush current of having all those capacitors. I might even be able to make them bigger speccing them for a lower voltage. For instance, the electrolytic C4+, C4-, C5+ and C5- only see half the regulated 10V, but I specced it for 16V in case of some sort of fault. It uses the same 470uF caps as the Mini^3. As you can see, I borrowed quite a bit from amb's design. 
 

That could be an issue; I'm not real clear how the DCP chips handle peak current draw. What are you using for C1 - 2,2uf, like in the datasheet? I wonder if adding a much larger cap in parallel with that, and moving the power switch to be in front of the DCP, would help; wouldn't the 5V reservoir cap, basically, then see at least part of the start-up current rush? 

  Quote:


 Thoughts? I think better when I do it out loud, so it helps when I can discuss with people. I have lots of little things to clean up, but I just wanted to get some of the technical stuff down pat now before it's too late. My biggest fear so far is about the isolated voltage somehow becoming +/- 5V relative to USB ground with the use of the TLE. That's what happens when you use an isolated DC booster, right? 
 

I think it's a nice idea - I came up with an identical power design a day or two ago, not having seen this thread before. Have you considered skipping the TLE entirely, and using one of the split-voltage DCP chips? The DCP0112DP, I think it is, is 5V in, fully isolated +/-12V out. It'd simplify things a tiny bit, IMO. Otherwise, you should be fine so long as the USB ground never connects to anything on the "other side" of the isolator - +V and 0V in, and +V and 0V out, but the two 0V terminals shouldn't connect, otherwise you're defeating the whole purpose of the isolator... I think.


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## DKJones96

That is a lot of capacitance to have on the power supply. You're gonna need a resistor in there or something to keep that USB port from freaking out when you plug that in. Also, it hasn't been mentioned yet, but not all computers will run this thing flawlessly. Some USB hosts won't supply more than 100ma unless the device requests it and some others will supply 500ma but if the device is connected the computer won't go into and out of suspend smoothly if you're using more than 100ma.


----------



## Punnisher

Quote:


  Originally Posted by *Nemo de Monet* /img/forum/go_quote.gif 
_Well, nobody else around here seems to like the idea of using USB voltage to power an amp, because they're all glass-half-empty naysayers 
	

	
	
		
		

		
		
	


	




, but I for one happen to think it's a spiffy idea._

 

I really don't see the problem. The 2move can be completely powered using USB, and that means the internal DAC and amp powering 250 ohm headphones. Sounds very good.


----------



## Nemo de Monet

Quote:


  Originally Posted by *DKJones96* /img/forum/go_quote.gif 
_Also, it hasn't been mentioned yet, but not all computers will run this thing flawlessly. Some USB hosts won't supply more than 100ma unless the device requests it and some others will supply 500ma but if the device is connected the computer won't go into and out of suspend smoothly if you're using more than 100ma._

 

<DonaldSutherland>
 Again with the negative waves! 
	

	
	
		
		

		
		
	


	



 </DonaldSutherland>

 Not counting the initial inrush current, which I'm unsure how to model, the high performance version of this thing will only draw _ca._ 80mA from the USB port, if that; the better-performing (on paper, anyway) extended-runtime even less - 35mA or so. Hence the oh-so-scary USB 100mA "wall" that one could theoretically come up against is largely a non-issue. You can do the math yourself - the typical current draws for the Mini^3 are here; the DC-DC converter gets 5V from USB and produces 12V, at an efficiency of 80% or slightly better...


----------



## rds

Quote:


  Originally Posted by *Nemo de Monet* /img/forum/go_quote.gif 
_
 If I understand the science correctly, that's a bad idea, and the two grounds should remain fully isolated to avoid ground loops and other less pleasant events._

 

There won't be ground loops. Isolation means exactly that - the supply is isolated.

  Quote:


  Originally Posted by *Nemo de Monet* /img/forum/go_quote.gif 
_I personally would put the LED on the isolated, boosted end of the DCP, as that way it tells you not that your computer is supplying voltage to the USB port, but that the power converter is working as it should, and hasn't gone into shutdown for whatever reason (overtemperature and undervoltage for sure; I'm not sure how it handles overcurrent.)_

 

I agree with joneeboi - don't waste that current. Keep it for headroom. 
 Do you really need a LED to tell you that the power supply is working? Personally I'd be able to tell that something is wrong when the amp is turned on and no sound is coming out 
	

	
	
		
		

		
		
	


	



 Besides that there's no reason to think the dc-dc converter will suddenly die. By this logic you'd want LEDs for every chip to indicate whether they are working or not.


----------



## Nemo de Monet

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_I agree with joneeboi - don't waste that current. Keep it for headroom. 
 Do you really need a LED to tell you that the power supply is working? Personally I'd be able to tell that something is wrong when the amp is turned on and no sound is coming out 
	

	
	
		
		

		
			



_

 

Is an extra, oh, 2mA of current really going to help any? You wouldn't be losing voltage swing, just - literally - a few mA of current, where there is, under every circumstance _I_ can think of, going to be plenty available.

 Also, isn't that _why_ we put blinkenlichten on these things in the first place - to indicate, in fact, that they're _on_? As the design stands, all the LED will tell you - because the switch is on the other side of the converter - is that the amp _is plugged into a running computer_. Even when you turn the amp off, the LED will stay lit. How useful is that?

  Quote:


 Besides that there's no reason to think the dc-dc converter will suddenly die. By this logic you'd want LEDs for every chip to indicate whether they are working or not. 
 

Um, no. See my comments above about the relative uselessness of the current LED position. Also, have you read the datasheet for the converter? It'll shutdown if it gets too hot - thermal overload protection, natch - but I'm unclear what if anything it'll do if you try to pull more current than it can provide (due, for example, to oscillating opamps, or a huge capacitor inrush current). Sag in voltage? Hold voltage _and_ current steady at the maximum limit? Shutdown? Couldn't tell you. There are also a couple fun circumstances where the chip will shutdown, just as one example, if the input voltage _at the chip_ sags too low, however momentarily.

 My feeling is that if someone puts the amp together for the first time, plugs it in, gets a lit LED, turns it on, and nothing happens, that lit LED should provide some more useful troubleshooting information than "your USB port is supplying at least _some_ voltage"; putting it on the isolated side of the converter will at least say "the power supply circuit is working as intended", or will narrow the problem down to one at the power end of things.


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## Juaquin

Not sure what all the fuss is about. Apparently people just do not want to see USB powered anything. I mean, an LED? Keep it in, cut it out, whatever. It's just a DIY project (no offense to the project).


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## DKJones96

I'd love to see more USB powered amps, I'm just not sure why you need to boost the voltage. I've heard some nice op-amps that work at under 5v. The USB dac/amp I'm working on runs on 3.3v(+-1.65v) for the amp. I've tested the amp on headphones at that voltage and it gets more than plenty loud(80ma/Amp ftw). In fact, once I found the right caps for it, aside from being loud and clean instead of distorting at high volumes you can't even tell it is there. But my goal is always transparency.


----------



## rds

Quote:


  Originally Posted by *Nemo de Monet* /img/forum/go_quote.gif 
_Is an extra, oh, 2mA of current really going to help any? You wouldn't be losing voltage swing, just - literally - a few mA of current, where there is, under every circumstance I can think of, going to be plenty available.

 Also, isn't that why we put blinkenlichten on these things in the first place - to indicate, in fact, that they're on? As the design stands, all the LED will tell you - because the switch is on the other side of the converter - is that the amp is plugged into a running computer. Even when you turn the amp off, the LED will stay lit. How useful is that?_

 

Just move the switch.


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## joneeboi

I really appreciate all the discussion that's going on. It's good.

 Allow me to give some context. I'm boosting the voltage because I'm trying to replicate the Mini^3. In some of my feeble attempts at producing a board for a CMoy, I kept coming back to what the Mini^3 had and was. I talked to amb about it, so now I'm more worried about doing the name justice. I was thinking of trying a chip that accepts 3.3V to 4.75V, but might come after this project.

 Boosting to +/- 12V doesn't give me enough current, plus the 5V-in, 12V-out chip that this paper says exists no longer is listed on the DCP02 product page. Having 2W would be a lot easier, but neither Mouser nor Digikey supply the product which seems to no longer exist. Plus, the OPA690 doesn't accept that high of a power supply voltage.

 Regarding the LED, I put it in at the end as an afterthought because, as rds mentioned, I don't really care about the light indicator, plus I could easily move the switch. If it plays music, it's good enough for me. I merely put it in as an afterthought for people who might want to build this thing as well, but personally, I wouldn't put in an LED. I was thinking of just using the planes to power it, thereby removing any need to route anything, but I didn't want to waste current from the TLE. I put it in the back just to satisfy the mere fact of having an LED, but I clearly didn't think it through. That all being said, it's just an LED. Let's worry about something more important for now.

 I'm quite tired of looking at the board editor in EAGLE, so let's discuss schematic and layout changes all at once to reduce my going back and forth to switch little bits here and there. I figured it would be good to put a capacitor between the TLE and TL750 as an input/output capacitor. They're so close I didn't think it would matter, but that seems to not really make sense. I'll throw C3 between the two and make it some ceramic/low ESR cap. I was also thinking of rotating the ground channel opamp just like how it is in the Mini^3. I don't know why I didn't start off like that. Anyway, that's something that will help with the parts placement, and it'll be more familiar and easier to build. Reducing the size of the test points will also help with the board space. Something else I was wondering about was the meaning of something in the TL750 datasheet. It says the output regulation voltage is 50mV to 100mV. Surely, that doesn't mean its output ripple is 50mV to 100mV, right?

 Another big question is about the wires. If I'm connecting both ground planes to the case, will I even need to connect the audio or power supply ground wire from the BantamDAC to the board? The ground plane will lie underneath the board, and it will connect to the case. There should be lots of current through those exposed planes, so it will save a little room and wiring if I don't have to connect that. The USB connector will sit in the back and will presumably connect to the case. Either way, it might be easier to connect the wires anyway, but I just wanted to feel out the possibility.

 Also, I was wondering what the full power supply draw will be from the AD8397. It says the supply current is maximum 12mA/Amplifier, but it also says the highest output current is 250mA at 3Vpp and Rload 12 Ohm. I was wondering what the power draw will be in total from the AD8397. Does 250mA * 12 Ohm ~= 0.75W make sense?

 Also, could anyone who understands USB weigh in here? I've read a little about it, but there's still a lot I don't get. I get that there's a handshake that occurs at the beginning, but I don't think the PCM2702 would request for full power output. It could very well demand 100mA and be done with it since it does have such a relatively low current draw at about 55mA, at least with the voltages cetoole chose. I get that it limits inrush current at plug-in and then gives the full power after enumeration, but do I have to get that enumeration to take place? How would I do that?

 In summation, my questions are:

 1) What does output regulation voltage mean?
 2) Would it be worthwhile connecting two ground wires between the boards?
 3) What is the max power/current draw of the AD8397?
 4) Do I need USB enumeration?

 More out loud thinking to come later.


----------



## joneeboi

Quote:


  Originally Posted by *DKJones96* /img/forum/go_quote.gif 
_I'd love to see more USB powered amps, I'm just not sure why you need to boost the voltage. I've heard some nice op-amps that work at under 5v. The USB dac/amp I'm working on runs on 3.3v(+-1.65v) for the amp. I've tested the amp on headphones at that voltage and it gets more than plenty loud(80ma/Amp ftw). In fact, once I found the right caps for it, aside from being loud and clean instead of distorting at high volumes you can't even tell it is there. But my goal is always transparency._

 

Just a quick mention on this. Even the iPod Wolfson DACs work on a low supply and can feed headphones directly, so maybe one can skip the amp altogether. Plus there are plenty of MP3 players that work off a mere AAA battery. Who really knows what's going on in there, but there is some merit to what you're saying though we won't get into the "audiophile" side of the discussion.


----------



## error401

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_2) Would it be worthwhile connecting two ground wires between the boards?_

 

Should work either way, though you should probably use a separate ground for each signal if possible, plus it's hard to get a really consistent connection without solder or compression.

  Quote:


 What is the max power/current draw of the AD8397? 
 

(Iq (per amplifier) * number of amplifiers) + dynamic load current

 Probably your average load current is going to be very small or you're going to be damaging your hearing. Except a couple mA at most.

  Quote:


 Do I need USB enumeration? 
 

Nope, the PCM2702 handles all of that. All you need to do is wire it up as specified and it will work. The datasheet isn't clear as to what it specifies as its power requirement, but I bet it enumerates as a 100mA device. I know the larger chips (PCM2707) allow you to choose between 100mA and 500mA.


----------



## joneeboi

I've updated post 3 with the current layout, but I'll add it here for convenience. I'm going to stick with the two ground wires for audio and bus power. Maybe I'll add another one for kicks.
















 My head is going to explode if I look at this layout editor any more. I wonder how bad it would really be if I just sent what I have right now to a board house. I haven't picked one yet, so that research will come within the next few days. Anyone have any recommendations for the layout? One of the big differences from the Mini^3 board is that there is a V- plane on top of the board. I wonder if that will cool the chips any better, but I also wonder about the instantaneous power requirements of the opamps and whether the V- plane will be good for that. There are a few extra capacitors next to the opamps, so we'll see how well that plays out.

 I also read on this thread that power will be readily available from the USB regardless of enumeration. I hope that that's true.
diyAudio Forums - USB powered HIFI headphone amp/DAC - Page 1


----------



## amb

You should carve a hole in the top plane around each of the opamps. Stray capacitance from the opamp pins to the plane is bad. On the Mini³ layout, I put the ground plane on the bottom side for this reason, and even there it has cutouts around the opamps.


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## Maxvla

Interesting project. Looking forward to seeing a working prototype with amp+DAC.


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## joneeboi

Quote:


  Originally Posted by *amb* /img/forum/go_quote.gif 
_You should carve a hole in the top plane around each of the opamps. Stray capacitance from the opamp pins to the plane is bad. On the Mini³ layout, I put the ground plane on the bottom side for this reason, and even there it has cutouts around the opamps._

 

Right, how abouts do I do that?


----------



## MisterX

Use the Polygon tool, choose layer 41 to draw a restricted area in the top layer or layer 42 for the bottom layer.


----------



## amb

I used rectangles, but the effect ought to be the same.


----------



## error401

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_I also read on this thread that power will be readily available from the USB regardless of enumeration. I hope that that's true.
diyAudio Forums - USB powered HIFI headphone amp/DAC - Page 1_

 

Yea, you can pretty much assume at least 1A will be available on a desktop machine even if you plug a 'dumb' device into the port, but it's a good idea to stick to the spec anyway. I don't think I've ever seen one that imposes any sort of limit based on the enumeration power requirement. I think it's mostly there so the computer can warn you if you're trying to draw too much power from one port. Laptops can be more finicky about power/port, but the enumeration still has nothing to do with it.

 As far as board houses, BatchPCB usually works out cheapest for very small runs (a couple boards), but their turn time is very bad. Olimex is a bit better for quality and speed, but more expensive and your board has to work well with their panel sizes, and having to fax your details the first time is pretty irritating. If you're doing any sort of production run, Imagineering or Advanced Circuits are good choices. In Canada, APCircuits in Calgary is pretty good.


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## joneeboi

Thanks a bunch, fellas. I'll have to get even more creative with the layout. That's fine. I'll probably just cut out the V- plane near the opamps entirely. And thanks, error401, for suggesting APCircuits. I moved to Calgary in January, so that ought to save me a little on shipping.


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## joneeboi

Okay, updated post 3 with new layout. How am I doing now? I added the keepout rectangles above and below the opamps, routed the power rail along the axis of the opamp underneath the board, cleaned up the naming, consolidated the test points into one area, and changed other minor things. Are there any other major areas I should address before getting the first prototype run along?


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## amb

I think you have the left and right channels reversed at the headphone jack.


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## joneeboi

u_u"







 Good catch, amb. That would have been a troubleshooting nightmare. Crisis averted. Anything else? Would there be value in connecting the heatsink underneath the EPAD to the ground plane? Would that infringe on the stray capacitance restriction?


----------



## MisterX

It's really hard to judge without a parts list but your ferrites look awful small 
 And there really is no reason have the caps jammed up against the other components like C1, C2 and C3 are.


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## amb

Don't worry about connecting the EPAD to any copper plane. It's more trouble than it's worth. Just by using the EPAD variant of the opamp (AD8397ARDZ) gives you quite a bit more heat dissipative capability than the non-EPAD (AD8397ARZ) version. With the lower supply voltages we;re talking about here, it shouldn't get appreciably hot anyway.


----------



## joneeboi

I've updated the layout on post 3. Some big changes:

 - Capacitors everywhere! Added an electrolytic before the switch and moved the tantalums next to ceramics for the ultimate in decoupling.

 - Widened power traces

 - Expanded restricted zone for power planes. I realized that with such huge planes, my board will act like a giant capacitor. The AD8397 datasheet recommends removing planes near the opamp so as to reduce stray capacitance. The Mini^3 has a sizable restrict zone, so I increased the size on this board because of the additional plane.

 - Minor labeling tweaks

 - Added second set of holes for filter inductor. There is only one inductor size that will really work from Digikey, and it's quite large compared to the one from Mouser.

 - Threw a bunch of traces underneath the board. I did this partly for shielding purposes, partly because the output ground trace was cutting off the plane. There are probably marginal benefits, if any, but it'll help theoretically.

 - Distributed the test points throughout the board. It was too difficult putting them together while optimizing everything. While that convenience is nice, I don't really care that much for it.

 - Lots of other little tweaks.

 - I reread the Mini^3 v1 and v2 threads to get some perspective. I admit I was a bit ignorant of the pain and love that went into the Mini^3, and I can understand if some of you thought I was a bit flippant in swooping in and trying to recreate the Mini^3. Not only was there the technical knowledge from the threads, but I learned lots about the feeling surrounding the project, both on the development and community sides. I'm standing on the strong and firm shoulders of giants, and I can only hope to have a project as successful as theirs. My stance has always been that I am merely making these boards for my own pleasure and if anyone wanted to get in on it, they could do so while following my reasoning in this thread. Please don't misunderstand me in this respect.

 So here we are. I'm beginning the testing stage of development, so *if anyone wants a prototype board, send me a PM*. The price per board will be quite pricey from APcircuits. If I get 6 people on board, it'll cost 134.76 CDN or 22.46 per board. For 10, it's 192.60 or 19.26 per board. More the merrier, ya? I'm going with AP because they're located in the same city as I am and I can save on shipping. I still have to test the power supply on plug board, but I think I can get the boards submitted and sent out ASAP. I've been poring over this layout for months now, and I want to keep a good pace by moving things along. There's so much I won't know until the boards are produced, so I'm praying every morning and night that everything will work out. The total cost of the project should run around the ~120 range depending on shipping and options. One must make at least two orders because of availability, so that adds to the cost. I really wish it could be only done via Digikey because shipping from them costs just the same as Mouser but can sometimes arrive the next day. That's just me.

 Again, if you're interested, please let me know. I can't wait to get this thing moving along.


----------



## joneeboi

Hey hey hey,

 I tested the circuit last night with a partially built Mini^3 and a plug board wired with the power supply, and it all checks out. Under steady state conditions, the power supply ends up being around 9.72V which splits between -4.36V and +4.36V with the isolated output rails having the virtual ground connected to USB ground. I realized that after submitting the board, I won't need the switched Alps RK097 pot after all. Since the amplifier's virtual ground is connected to the case, the switch is essentially bypassed because it is connected to USB ground. Alas, that will be something that I will revise in the final production version. In the mean time, one can use one of the smaller unswitched Alps RK097 pots, which will be a way of increasing board space. The offset in my Mini^3 resided in the 2mV range, and I discovered that my BantamDAC that worked on my laptop when it was XP didn't work when I upgraded to Vista. I installed Microsoft's hotfix, A hotfix rollup for the USB audio driver is available for Windows Vista-based and Windows Server 2008-based computers, so I hope that it will work when I test it later. Compared to my test setup, the opamps will have much more decoupling capacitance than available on the Mini^3 board, so my hope is that the power supply I dreamed up will be sufficient to warrant the Mini^3 name. With the extra space coming from the smaller pot, I think I can use a slightly better filter for the DC/DC converter. I'm quite excited to discover this. This also means I need to rework Tangent's RK097 library. =T

 What can I say? I'm ecstatic that the testing confirmed a lot of my suspicions and conclusions, and I look forward to all the magnificent work ahead of me. Further, in honour of this momentous occasion, I have decided to change the name to its final version: Carrie. Yes, I know it's very much in the way of diyparadise, but I'm going to stick by it 
	

	
	
		
		

		
		
	


	




. It's my girlfriend's name, and she's been with me through thick and thin. She's heard it all when it comes to the amp's layout, and she's supported me through its design. I'm dedicating this amp to her, so now you can all call it joneeboi's "Carrie" amp.

 That's mostly all I have to report for now. I jumped on MrMajestic2's thread, and now I have to play the waiting game. I don't want to be presumptuous and just assume that the amp will work fine, but I like what I saw last night. I better make my order to Mouser now. Two weeks in this context is a really long wait.


----------



## cobaltmute

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_So here we are. I'm beginning the testing stage of development, so *if anyone wants a prototype board, send me a PM*. The price per board will be quite pricey from APcircuits. If I get 6 people on board, it'll cost 134.76 CDN or 22.46 per board. For 10, it's 192.60 or 19.26 per board._

 

If I read right and your board is the 80x50mm for the 1455C80x boards, you may want to try Gold Phoenix for your boards. For my DAC boards (which are the same size), I got 17 of them for $89US.


----------



## joneeboi

Actually, the boards are a little smaller at about 50.5mm x 53mm. And I think I may have flubbed on the thing about the switch. I got mixed up between USB/virtual ground and V-, so scratch that whole bit. I'll keep Gold Phoenix in mind for the final board run.


----------



## joneeboi

There are still 5 boards up for grabs if anyone else is interested in prototyping Carrie.


----------



## joneeboi

Observe this plugboard prototype of a Mini^3 being powered by the USB. It isn't nearly as compact as I originally envisioned, but it works. I was listening to it all day, and I really liked it. I'll admit, my low impedance 'phones don't require much gain. At gain 5, I barely have any room on the volume knob to play with. Then again, that's with a different source. Notice how the Bantam is merely providing power and no audio. Not a complicated circuit by most accounts, but it gets the job done. It should be a week until the boards are done, but that doesn't include how long it will take to get to my place. I haven't been this anxious in a long time. 
	

	
	
		
		

		
		
	


	




 I'm imagining Nemo's circuit being more popular than mine because sources are selectable with his USB power board, but after all, I'm only making this board because I don't want to mess with too many batteries; the one in my laptop is okay. Consider it DIY laptop hi-fi.

 And um, ignore the tax form.


----------



## joneeboi

I discovered a very nice stash of parts in my parts bin, and it turns out I had enough parts to recreate another BantamDAC, meaning I won't need to buy as much from Mouser. I tested it this morning, and the BantamDAC works! Yay! I had to salvage a few parts from a previous Bantam, but I eventually managed to get it all together. I've never before been so relieved to see the words "Japan Burr-Brown PCM2702" in my ASIO4ALL. 
	

	
	
		
		

		
		
	


	




 And since my last post, I've corrected the odd plugboard wiring for the amp. Now the 470uF 'lytics stand across the rails and virtual ground, and virtual ground is connected directly to the USB. Without wiring the virtual ground to USB V-, the voltage split between +/- 4.72V anyway, but now that it's connected, it won't float away or wobble as much. I'm quite pleased by this result. And even though I don't have an oscilloscope handy to prove it, the amp is dead quiet. I plugged in my Shure E4's and turned it up full blast, and there was but the slightest hint of hiss. Plugging in my iPhone made the hiss quite audible, but I don't think it'll be the same working with the Bantam. I'd be moving from the iPhone's Wolfson system-on-chip to the less congested BantamDAC layout. In my mad dash to finish the soldering last night, I forgot to solder wires from the BantamDAC's C7, so I am currently unable to test the sound of the two boards. Nevertheless, I am very happy to report that I have a working BantamDAC and a very quiet power supply. I imagine it will only get quieter moving from plugboard to PCB.

 As of yet, I have not received the boards from Olimex/MrMajestic2, but that gives me more time to figure out what I want to order from Mouser. I've got the PIMETA v2 still to figure out, and I just received that board a few days ago. Plus, my birthday is this Saturday and I'll be heading up to Edmonton to celebrate, so there is a good chance I won't even order anything until the next week. Nevertheless, things are looking up from here. Hurray!


----------



## DKJones96

I'm glad to hear you have the same results as me with that upconverter. Nemo's USB 9 volt replacement board is extremely quiet. Those TI converters are silent and awesome.


----------



## joneeboi

They have switching noise at 800kHz, but that's impossible to hear anyway. I wonder what kind of bad effect the noise can have on the equipment. Even if it did creep into the amplifier, how would it affect the sound? I should try running the power supply unfiltered, but my feeling is that it's not needed. Perhaps filtering the noise is being more electrically responsible.


----------



## joneeboi

Here are some images taken yesterday by MrMajestic2.










 Can you feel it? Man, I'm excited. They should be arriving here in a week.


----------



## Gross

Nice.


----------



## Bonthouse

This is looking very promesing! Gonna buy me one when a DIY kit is for sale somewhere


----------



## joneeboi

I don't know about offering a kit because it's a mostly straightforward build. The best I feel like providing is a Mouser and Digikey BOM. I can even provide it in EZ Buy format although I recognize that you live across the Atlantic pond. I'll see if Jeff will be interested, although I don't know if there would be enough demand. It won't hurt too much to ask, I suppose.

 I was pleasantly surprised by the gold finish. This will be one slick-looking amp.

 edit: Okay, maybe Farnell too.

 edit2: Maybe a group buy of kits would work.


----------



## individual6891

Hmmm, what happened to this thread? Any updates? Will there be a GB?


----------



## DKJones96

We should be receiving the prototype boards soon. Not sure about after that.


----------



## joneeboi

I just sent out the proto boards today. I wouldn't say they'd be arriving "soon," but they'll get there. My projects have been slowed to a crawl because my place is being renovated, and I don't have a place to do any work as all my belongings have been thrown on top of my bed and pushed to the centre of the room. I have all the parts on me and it's a pretty quick build, but I just don't have enough time to devote to it now.

 As for GB and other options, it all depends on demand. I don't know how many people want a device I'll classify as laptop-fi, but if enough people get on board, I don't mind running a few more boards. Last resort would be to hold onto a few boards and sell it to whoever's interested. We'll see.


----------



## individual6891

Do you have anymore of the prototype boards available? and at what price?

 The GBs at diyaudio usually have quite good demands


----------



## joneeboi

I have some more proto boards if you're interested in one. Only 3 or 4 to go.


----------



## joneeboi

I was asked why I chose a single-rail DC/DC converter, and I thought it would be useful if I posted the answer.

  Quote:


 There are a few reasons why I chose the DCP010512BP. I found it to show the best balance of all the factors I was looking for:

 1)Efficiency

 It features a maximum of 89% at full load, a little lower at lesser loads, but still very good compared to the mid-70’s I found with other manufacturers.


 2)Availability


 It’s a line that’s carried both at Mouser and Digikey. Many of the other ones I was looking both at Mouser and Digikey had low availability, sometimes fewer than 20 in stock. I don’t know if this project will attract that large of an audience, but I don’t want the few builds of it to deplete the entire stock of one of the key components.


 3)Power Supply Constraints

 The OPA690 has a power supply voltage limit of 12V or +/- 5V, and the Mini^3 protos oscillated at 24V, the theoretical max voltage input for the AD8397. The DCP series only offers +/- 12 and +/- 15V split rail converters, so if I used a split anything in the DCP/DCV/DCR series, I’d just be burning away precious power to keep the AD8397 from oscillating and the OPA690 from blowing up. It’s not that the amplifier needs much power or that there isn’t that much power to spare, it would just be an inefficient design with the simple fix of going with the DCP010512BP. Furthermore, the power supply when regulating with the TL750L10CLP, another part that fits squarely in this design, splitting with the TLE2426CLP, and connecting the midpoint to the USB ground, the voltage splits anyways at a rock solid +/- 4.72V. Now, I’m not sure why the TL750L10CLP is regulating down to 9.44V because it goes beyond the datasheet’s specs (and it isn’t anywhere close to the full load of the regulator’s 150mA max), but I’m not gonna complain. Perhaps the prototypers can shed some light. With this setting, it allows the higher voltage swing the Mini^3 could have without the constraint of low charge capacity and size issues with certain batteries.

 Regarding the TL750L10CLP, there aren’t any other LDO regulators in a TO-92 package that regulate to 10V. I was a bit surprised, but you can do the search yourself on Mouser and Digikey.


 4)EAGLE

 There was already a library for the DCP0105 in EAGLE. Consider it the cherry on top. =P

 With these characteristics in mind, you could even say the design demanded the chosen chip. Nevertheless, I’m open to other considerations if it fits better. I’ve searched and searched, but I’ve come up fruitless. Any suggestions?


----------



## joneeboi

I'm happy to report that I've completed my first build of Carrie. It took me a grueling 5 hours to complete this morning (started at 6 am), and it looks nice. I've learned a few things about design and procurement just from building the thing, so I had a pretty good morning.

http://files.getdropbox.com/u/886264...e/DSC01060.JPG

http://files.getdropbox.com/u/886264...e/DSC01061.JPG

http://files.getdropbox.com/u/886264...e/DSC01062.JPG

http://files.getdropbox.com/u/886264...e/DSC01063.JPG

http://files.getdropbox.com/u/886264...e/DSC01064.JPG

http://files.getdropbox.com/u/886264...e/DSC01065.JPG

 The BantamDAC that I built from before wasn't putting out any music, so I'm not quite ready to write my final report. Right now, signal input is from my iPhone.

 Here are some things I learned when building this amplifer:

 - Buy the right parts. R5L/R are physically too large. I neglected to get the micro-sized resistors. Are there stability issues involved here?

 - Make sure the edgeside components don't bump into the enclosure. Notice the capacitors near the ground channel that come close. This is being addressed in the next board version.

 - Make sure you carefully choose the components that involve a plane. I soldered in the wrong filter capacitors (voltage rating too low), so I had to do some rework. Pulling out the caps was easy enough, but cleaning up the holes was the hard part. One of the pads fell off, and it was impossible to get the solder cleaned out of the holes. Now I only have the inductor doing the filtering, and the switching noise is still getting through. This should not be.

 - A small project like this can take a long time. Wow, I totally underestimated the time it took to build it.

 - The space allotted to the filter capacitors was not enough. I had to tombstone the capacitor first time through. Everything fits the way it is in EAGLE, so I have to do some *major* wiggling.

 - The Molex connectors are too long; without wires, it fits to the top of the case. I had to dremel off the female, cable-side connector so I can slide it into the case. Hardwiring underneath the boards may be preferable to Molices at all. I think I'll leave it in though.

 - Panel-mounting the output connector can open up some board space. I don't want to change too much, but I might have to.

 - L1G caught on the enclosure on my first fitting. This also happened with my Mini^3 builds.

 - The knob I chose is so sexy. Goodness, I like it so much better than the ones with the two rubber O-rings. The knurls make for better grip when controlling the volume anyway. It doesn't fit with the look of the Hammond, but it still looks good. 
	

	
	
		
		

		
		
	


	




 I've noticed a peculiar problem of the output signal clipping. I don't have any sine wave tones or an oscilloscope, but it doesn't sound right when I turn up the volume to a comfortable listening level. Sounds clippy. I only used a gain of 2 and the voltage at the opamp pins is still +/-4.72V. The full output voltage of the iPhone's Wolfson is AVDD/3.3 Vrms, and running off the battery, I can't see it being higher than 1.212 Vrms, or 3.17 Vpk-pk. With a gain of 2, the max signal I would see at the output is 6.34 Vpk-pk, right? I'm using JVC Marshmallows which have an impedance of 14 Ohms, and it even happened on my 32 Ohm Yuin PK3s. Is too much current being drawn from the AD8397? It should be able to output 250mA into a 12 Ohm load when the opamp pins are given 10V or +/-5V, so I can't see it drawing too much from the opamp. This didn't happen with the Mini^3 (gain 5) with modified PS. I'm thoroughly perplexed and annoyed.

 Does anyone have any insights? I have an extra DCP01 which I can parallel with the current one, so I can double the available power if it's currently insufficient. I will try disconnecting the current Bantam from the USB by taking out L3, so we'll see if it's a power draw issue. For now, enjoy the photos.


----------



## Bonthouse

This is getting so juicy it's not even funny anymore..
 Awesomely looking!


----------



## joneeboi

Thanks, Bonthouse. 
	

	
	
		
		

		
		
	


	




 I hope to have time to work on my second Carrie, so there should be more juicy photos and, I hope, a working amplifier.


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## Billyk

I am getting excited as it comes closer to a reality!
 I have hopes of building this for my son's 21st birthday, he is a musician and his laptop is never far from him. I am sure he will love it.
 Keep up the GREAT work!!


----------



## DKJones96

I'm looking forward to having mine done. It should be completed this weekend as the last of my parts are on their way. I've got plenty of pictures.

 It's my first build with the new solder.


----------



## joneeboi

If you didn't see the other thread, the problem with the amp is that I was shipped the wrong resistor for R5LR by Mouser, and I installed those wrong resistors. I received the resistors yesterday, but I won't be back in town until after the weekend. I will have time on Monday to work on it, and I'll report back. It's all so exciting.


----------



## Billyk

That's great sounds like an easy fix. 

 DKJones96, did you finish yours yet? How is it going, is it making sound yet?


----------



## DKJones96

Unfortunately my opamps haven't come in yet. When they do I plan on having mine done that night with my first impressions and construction pics.


----------



## joneeboi

I just got my resistors today. They did indeed arrive as expected, but no one was home to receive the package. I only had enough time today to get it, so expect the completed amp sometime soon. I'll be picnicing all weekend, but I should have something sometime later (learning to be more careful with my promises 
	

	
	
		
		

		
			





).


----------



## joneeboi

Okay, so honestly, I couldn't wait until this morning to switch out the resistors. I'm pleased to announce a fully working Carrie! I'll have to wait to get my BantamDAC built up though, but nevertheless, it's a nice feeling to listen to an amp that I designed (more or less 
	

	
	
		
		

		
		
	


	




) and built. Yay!

 I'm still waiting for prototyper comments, so I'm not going to finalize a design yet. I am still tweaking the power supply according to what I felt should be changed, but I'm still eager to hear what others think of the build difficulty and such. I feel I'm getting the hang of EAGLE, so it's going to be less difficult and more fun using it. And as grateful as I am to MrMajestic2 for letting me get on board (pun intended) with his order, I'm not all that pleased with the build of the PCB. I had to rework a few pads, and most of them fell off the board. Humbug. Alas, one more prototype run, and then off to production we go.

 Ah yes, the sweet sound of music. It's currently hooked up to my iPhone 2G and I'm listening through my Shure E4Gs. Success!

 edit: Of course, thanks go to AMB for allowing me to lift, at least temporarily, the schematic, layout and name of the Mini^3 for the design. We'll still have to see how it measures, but that will come with time. If not, I'll just have to remove the Mini^3 name from the board.


----------



## joneeboi

Happy Canada Day. 
	

	
	
		
		

		
		
	


	









 More to come within a few days.


----------



## joneeboi

For more gory photos, check out,

Picasa Web Albums - joneeboi - Carrie

 Enjoy.


----------



## Gross

Well, I have a successful pairing of a Bantam and a Proto Carrie. Works great, sounds great too. My voltage out of the converter is only 7.5 volts or so though, so maybe I have something a little goofy yet. Will post pics tmw.

 Edit: I measure +4.89v and -4.89v at the appropriate pins on both Opamps. I must have done something right. Although I havent even looked at the schematic for this, so I maybe that 7.5v is ok.


----------



## tomb

Looks pretty neat, guys!


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## Billyk

Looks really good. I want one!!!


----------



## joneeboi

Thanks, Tom and Billy. 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *Gross* /img/forum/go_quote.gif 
_Well, I have a successful pairing of a Bantam and a Proto Carrie. Works great, sounds great too. My voltage out of the converter is only 7.5 volts or so though, so maybe I have something a little goofy yet. Will post pics tmw.

 Edit: I measure +4.89v and -4.89v at the appropriate pins on both Opamps. I must have done something right. Although I havent even looked at the schematic for this, so I maybe that 7.5v is ok._

 

Thanks for getting yours up and running so quickly, Brian. 
	

	
	
		
		

		
		
	


	




 Which pin are you using as reference for that 7.5V reading? If you measure between TP5 (GND) and TP2 (the output voltage of the DCP), then you should get that 7.5V. If you measure between TP6 (V-) and TP2, you should get something like 12.89V. Between TP6 and TP4, you'd measure 9.78V. For the next version of the board, I'm renaming the test points from TPx to what they actually represent: V+, V-, 12V, 12F(iltered), 5V and 0V. That way we can avoid this kind of confusion. 
	

	
	
		
		

		
		
	


	




 Keep in mind that the DCP is isolated, and USB GND, aka input V-, is connected to the midpoint of the output.


----------



## Forte

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_For more gory photos, check out,

Picasa Web Albums - joneeboi - Carrie

 Enjoy. 
	

	
	
		
		

		
		
	


	


_

 

Great little design and well executed, really like it.

 When do you think you will have production boards ready? I don't really need another portable, but like this so much I may not be able to resist. I have a spare Bantam board in my parts box, I think it may have found a home.


----------



## joneeboi

I don't know when production will take place. I can't imagine how long it will take to reel in all the suggestions from the prototypers, and I don't know how strict to be on deadlines. I don't want to force anything just to rush it out the door though. Once I feel comfortable with the improvements and the state of the design, I'll get it prototyped at least once more, and then I'll put the finishing touches on it before getting it fabbed. If there's enough interest, perhaps we can do a group buy so that I won't break the bank.


----------



## Gross

lets see if this linky works Picasa Web Albums - brian - Carrie


----------



## nullstring

Are you planning on merging the two PCB's, or keeping them separate?

 If I build this, I think I might try to squeeze line-in and line-out into it. I'm not sure it's really necessary to add to the PCB though.


----------



## mugdecoffee

I was looking at the psm2707 datasheet and it has a VCOM output on pin 32 which is half of the 5V (or 4.75V regulated) which would be should be the same DC level as the left and right channels. Since the mini3 is a 3 channel design, couldn't you somehow connect the ground channel to the common/half voltage and eliminate the output caps? Basically, if you set the mini3 ground to 2.5V relative to the USB bus, I think you could eliminate the DC offset.

 Is this correct?


----------



## steven2992

Great work! Have you thought about making it one pcb? Getting rid of those wires would really clean it up. 
 If you'd join the boards i'd be very interested in a group buy.


----------



## Bonthouse

Quote:


  Originally Posted by *steven2992* /img/forum/go_quote.gif 
_If you'd join the boards i'd be very interested in a group buy._

 

x2!


----------



## nullstring

I'd be interested in a group buy either way.


----------



## joneeboi

Quote:


  Originally Posted by *nullstring* /img/forum/go_quote.gif 
_Are you planning on merging the two PCB's, or keeping them separate?_

 

 Quote:


  Originally Posted by *steven2992* /img/forum/go_quote.gif 
_Great work! Have you thought about making it one pcb? Getting rid of those wires would really clean it up. 
 If you'd join the boards i'd be very interested in a group buy._

 

I know it's nice and convenient to have one board, but you don't realize how much work goes into producing these boards. It took me 9 months to get the boards produced. I'm not overhauling the project just to get rid of the four or five wires.

  Quote:


  Originally Posted by *mugdecoffee* /img/forum/go_quote.gif 
_I was looking at the psm2707 datasheet and it has a VCOM output on pin 32 which is half of the 5V (or 4.75V regulated) which would be should be the same DC level as the left and right channels. Since the mini3 is a 3 channel design, couldn't you somehow connect the ground channel to the common/half voltage and eliminate the output caps? Basically, if you set the mini3 ground to 2.5V relative to the USB bus, I think you could eliminate the DC offset.

 Is this correct?_

 

This is correct, but maybe in a different enclosure.


----------



## mugdecoffee

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_This is correct, but maybe in a different enclosure._

 

The only connections between the bantam and the mini3 look like the left and right outputs, VBUS+ and VBUS- for the isolated DC-DC converter, and ground. It seems like making the modification would be as simple as running a wire from the bantam VCOM pin to the mini3 ground (edit: in place of the ground-ground jumper).


----------



## joneeboi

Wait, scratch that.

 If you connected VCOM to ground and USB 5V to the DCP input, you couldn't get any voltage output from the DCP because the input would only be ~2.6V. If you lifted the leads of the DCP input away from the holes and airwired the USB power, it would work. You'd also have to airwire the DCP's input capacitor. The case would have VCOM's voltage, so you'd have to make sure the USB connector isn't electrically connected to it or else you'd be shorting 2.5V to ground.


----------



## mugdecoffee

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_Wait, scratch that.

 If you connected VCOM to ground and USB 5V to the DCP input, you couldn't get any voltage output from the DCP because the input would only be ~2.6V. If you lifted the leads of the DCP input away from the holes and airwired the USB power, it would work. You'd also have to airwire the DCP's input capacitor. The case would have VCOM's voltage, so you'd have to make sure the USB connector isn't electrically connected to it or else you'd be shorting 2.5V to ground._

 

Sounds doable if you use plastic endcaps but not quite as elegant as your current setup. At the same time if you're already running wires between the two it wouldn't be much more work...

 If you do make a revised edition, it could be useful if the DCP's ground pin and its input cap weren't connected directly to the ground plane but via a short trace that you could cut. That way it would take no extra work for the configuration you have now but the VCOM buffering could be done more easily and without lifted leads or airwiring the cap.

 Another way to do it would be to require a jumper between the DCP's negative input and cap and the mini3 ground but that would require an additional step for those taking the cap approach.

 It seems like the only downside the buffered VCOM is having to solder the wire to the 2702 pin.


----------



## joneeboi

What I can do is disconnect the DCP's negative input lead from the ground plane, and that will allow the user to select where they want the ground to connect to. Also, you can solder a wire to/from the Bantam's C12 for VCOM. That also brings the design closer to the Mini^3 in that it is a DC-coupled amplifier.


----------



## DKJones96

Got mine together last night. I only briefly powered it up to check voltages and noise since I don't have the pot installed yet and used 1/4 watt resistors instead of the specified 1/8th. 

 The modular USB power supply uses the same TI chip and with a 10uF SMD cap for filtering alone and it was silent. I'll double check tonight if I hear anything before the pot goes in. C2 and C3 should be more than plenty as TI specifies 10uF being the point of diminishing returns.


----------



## DKJones96

Alright, done. Couldn't get those stupid connectors to work for me but I made do anyways.

 I've got no discernible clipping in the amp using the opamps in the BOM. It'll drive the headphones to the point that the LED begins to dim on the beats(no longer have the headphones on at this point) and it still doesn't clip. No switching noise either.

 Now, I did use 2.2 ohm at R5L and R5R but that was because it was the closest value I had on hand.


----------



## joneeboi

Thanks for the update, Kyle.

 I guess you proved that the layout isn't all that sensitive when it comes to resistor placement. 
	

	
	
		
		

		
			





 What headphones are you using? I didn't notice any dimming of the LED when playing full blast, but I can check again.

 I'm irritated by how the potentiometer has the slight bit of channel imbalance at the very lowest volumes. I will look into this a bit more, but from what I remember reading somewhere, placing a series resistor before the potentiometer should fix that. Can anyone confirm?

 I was having problems with the Molex connectors; is that what you were talking about, Kyle? I've never used them before this project, so I'm not quite sure how it all works. The connector fits right to the top of the case without wires, so that's reason enough to drop them. I don't know how often one would need to separate the boards, but if I got rid of the Molex connectors and replaced them with spots for the resistors, I think that would be a better setup. I'm going to get rid of one power supply capacitor and move the switch, so that should simplify the design a bit.

 Thanks for stopping by, everyone. I appreciate your continued participation in this project.


----------



## Billyk

This is looking really great! Please consider me for the next round of prototypes, I would love to participate.


----------



## DKJones96

Yeah, I've never used the molex connectors either, I will play with them as I need to use them for my PPA so it can be troubleshot without the need for a soldering iron just to expose the board in the case. I couldn't figure out how to get the connector into the socket after attaching a wire to it so I just soldered my audio and voltage input wires straight to the board. I'm thinking about using some good old header connectors since I never have trouble with those.

 I wouldn't worry about the dimming led I mentioned. It's worst case. I was using a pair of 16 ohm Sony cans to load test the unit and had loud songs playing at full player and amp volume. WAY past your normal listening volume and higher impedance phones won't load it up enough to cause that.

 I'll check on the low volume imbalance tonight. I've gotta find my Bantam or build a new one since I have no idea where that little thing went.

 Since you know it'd be paired with this amp, could the output caps on the Bantam be bypassed? That'd give zero caps in the audio path between the DAC and the headphones.


----------



## nullstring

I would like to point out that maybe it's best if the PCB remain separate.

 Just in case someone wants to use the PCM2707 or otherwise so that they can add SPDIF output, etc.


----------



## joneeboi

I will consider the cap-less design a bit more seriously since it not has a market/demand but it also sounds like a better idea.

 I wonder what other kind of DAC could be made on the same amount of board space as the Bantam. Is that a design challenge for another DAC module brewing? >=D


----------



## nullstring

I was thinking of a PCM270X based DAC, where X > 2 

 Something like the HagUsb or the twisted pear DAC.
 Both of them don't seem to use PCB space efficiently, so a new layout would need to be designed.

 HagUsb is mostly non-SMD... and twisted pear has excess spaces for the terminal blocks (I think that's what they are called)

 I noticed neither of them seem to use regulators.
 Were those a special requirement for the PCM2702 DAC's? or do these not include them because they are made more for SPDIF than analog.

 I also know that these DAC chips have lower quality analog output, so, I'm not sure how many people would actually want to use one.

 holy hell, there is a fawn in my front yard.


----------



## mugdecoffee

Quote:


  Originally Posted by *nullstring* /img/forum/go_quote.gif 
_I noticed neither of them seem to use regulators.
 Were those a special requirement for the PCM2702 DAC's? or do these not include them because they are made more for SPDIF than analog._

 

The 270X chips need around 5V to run. The bantam has regulators to get the cleanest power since the2702 is used for its analogue outputs though 2702 can be powered right of the usb 5v supply. The twisted pear usb receiver is uses the straight 5V from the USB probably because its being used for its spdif output where clean power isn't as critical.


----------



## error401

I finally received the rest of my parts from Mouser last week, and today I got around to building up the Carrie board. I used the posted BOM in the 2nd post and pretty much ordered what was on there. I haven't had a chance to hook it up and test it yet, but I did have a few build notes. I haven't been following the thread, so sorry if these have already been mentioned.

 - Having C1F/C3F and C1/C3 be different BOM items confused me. I installed the tant caps in the wrong spot and then had to desolder them. These should be renumbered.
 - C1F and C3F don't fit
 - The silk for C4 doesn't show the + marking, this should be moved so it's visible
 - It'd be nice to have L/R/G markings on the J1 pads; I plan on using a panel mount jack
 - This is really totally unimportant, but the silkscreens all have a slight 'staircase' effect on long straight lines, like the whole board was rotated a degree or two on a low-res display. Weird.

 Overall though it was pretty easy to put together. I'm reminded how much I hate TH, but aside from taking forever I didn't have any real issues with assembly. We'll see how it sounds tomorrow when I build up a BantamDAC to go with


----------



## joneeboi

Thanks a lot for that, Keenan. 
	

	
	
		
		

		
		
	


	




 That's extremely helpful. I have some time this weekend, so maybe I'll add those changes.

 I noticed the horrible silkscreening too. My EAGLE files have straight lines, so I don't know what Olimex was doing. I didn't realize also just how thick the lettering would be. I will try reducing the thickness and maybe get the boards fabbed at Imagineering. I'll add the labels to the output jack on the bottom of the board, and I may just get rid of the Molex connectors altogether. I mentioned in my PM that the filter caps would be too large for the allotted board position, but that was after you already ordered your parts. I'm also reconsidering the board-mounted jack. It's nice, but it takes up so much room. I don't know what exactly I could do with that space, but I could definitely tighten up the board if I did.


----------



## DKJones96

It should be noted, I mentioned earlier running the bantam without the output caps. DO NOT do this. The 2702, when active, creates a virtual ground at about 2.3v and this makes the amp run full 5v at the phones at anything past 1/4 volume.

 I only measure 11mV of dc offset at full volume otherwise.


----------



## joneeboi

Did you connect the ground of the Carrie Amp with the 2.3V and connect the DCP input V- only to USB GND?


----------



## DKJones96

Well see, when I did my initial measurements I thought it was fine because I measured no offset on the bantam(I hadn't played a song yet) but if you pause the player in the middle of a song you'll notice that it goes to 2.3 and stays there until the end of a song where it times out and the output settles back to 0 again. 

 It doesn't keep a constant output voltage and with the behavior of that chip I can't really see any other way to connect them except through the caps.


----------



## joneeboi

Sorry for the super delayed post. I have been working on the amp, but I've just been busy moving back to Edmonton. I went through the schematic with a co-worker who specializes in Anyway, I tweaked the schematic a little bit and made some design changes. Here they are in no particular order:

 - Added capacitors to match the peak output power. With a ~10V power supply with a rail-to-rail opamp into 32 Ohms, RMS power requirements demand (7.07V^2)/32 Ohms or 1.56W per channel. Of course, no one will ever be able to listen to anything that loudly with headphones, but I've changed the design to make sure the design lines up with itself. The capacitors will supply enough power for the power capabilities.

 - Removed Molex connectors.

 - Moved LED, RLED and L1L so that a separate input jack can be panel-mounted. There's enough room on top of the BantamDAC for a panel-mounted DPDT switch, so you can choose between external source and the Bantam.

 - Rearranged the entire power supply. Filtering section has changed, renamed all the capacitors, and moved things around

 - Changed the fonts so they show up more clearly when printed






 I'm getting ready to produce the boards. Any last objections?


----------



## Juaquin

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_I'm getting ready to produce the boards. Any last objections?_

 

Yes. This is too awesome. I request you reduce the awesomeness level by at least two notches.

 Definitely in for one, if there will be a run of boards.


----------



## rds

Quote:


  Originally Posted by *Juaquin* /img/forum/go_quote.gif 
_Yes. This is too awesome. I request you reduce the awesomeness level by at least two notches.

 Definitely in for one, if there will be a run of boards._

 

Agreed on both counts


----------



## mp101

brilliant.

 If you do agroup buy, I'd be intersted.


----------



## cobaltmute

Not sure how tall all you caps are (like CF1, CF2), but will you have clearance past them to get wires to IL,IR and IG?


----------



## Billyk

Most Excellent!
 Please count me in on this for whatever is needed or just to purchase a board when they are ready.


----------



## joneeboi

cobaltmute:

 All the caps are 15mm high, but wiring can be done underneath the boards. There is 2.00mm clearance underneath the boards, and you can fit up to 19AWG with the holes' inner diameter.

 I am preparing to order from 4PCB.com's $33 each deal. With that comes a few limitations, those of which will be restricted to the prototype board. I PMed those of you who are interested, but I realize that if you're willing to pay up, we can get more than 5 boards. Silly me. Anyway, the more the merrier, so let me know if you want in.


----------



## DKJones96

Looks good, just a couple of comments.

 Where is inrush current being limited at? The DCP0105?

 While 1.56w per channel is nice, the USB port can't power that. Add the extra juice from a Bantam and you are over your USB specification by about 30%. That, of course, is if you run the 2w unit instead of the 1w unit that the original build calls for and even with the 2w unit you run it over spec at anything over 1w per channel(assuming a 100% efficient amplifier). Just something to keep in mind.


----------



## cobaltmute

Ahh, hadn't though of underneath the board.

 Wouldn't this be cheaper for your boards at $10/board with 5 day turn?
http://www.pcbnet.com/a1ad22.asp


----------



## nightanole

So whats the diff between this usb mini3 and this one for $45 shipped with half the parts?

Meier-Audio

 The meier one doesnt have a 3rd ground channel, but it does have 2 opamps and swings +-5v like a 9v powered Mini3


----------



## revolink24

Read the thread title. That is a USB DAC, not a USB powered amp.


----------



## tomb

Very impressive, Joneeboi! Good luck on this round of protos!


----------



## onyu

revolink24

 that thing from meier is a amp/dac
  Code:


```
[left]A DIY PORTABLE HEADPHONE AMPLIFIER WITH USB-DAC[/left]
```

did you even take the time to read Mr. Meier his page?


----------



## nightanole

Quote:


  Originally Posted by *revolink24* /img/forum/go_quote.gif 
_Read the thread title. That is a USB DAC, not a USB powered amp._

 

Uh its a headphone amp that has a built in usb dac. If you plug it into a usb port it sucks the power from the usb port. If you plug in an external source it runs the amp off the usb or the internal 9v, and amplifies the external source.

 what i can see the diff is:

 mini3 is regulated 12v unit with a ground channel and a stereo opamp

 the Meier is an unregulated virtual ground unit that uses 2 mono opamps.


----------



## revolink24

Quote:


  Originally Posted by *onyu* /img/forum/go_quote.gif 
_revolink24

 that thing from meier is a amp/dac
  Code:



		Code:
	

[left]A DIY PORTABLE HEADPHONE AMPLIFIER WITH USB-DAC[/left]


did you even take the time to read Mr. Meier his page?_

 

 Quote:


  Originally Posted by *nightanole* /img/forum/go_quote.gif 
_Uh its a headphone amp that has a built in usb dac. If you plug it into a usb port it sucks the power from the usb port. If you plug in an external source it runs the amp off the usb or the internal 9v, and amplifies the external source.

 what i can see the diff is:

 mini3 is regulated 12v unit with a ground channel and a stereo opamp

 the Meier is an unregulated virtual ground unit that uses 2 mono opamps._

 

Indeed I did read his page.

 "Power is supplied by a 9V battery or a 9 .. 28 Volts external powersupply. The power voltage is splitted by a TLE2426 rail-splitter to create positive and negative powerlines of 4,5 .. 14 Volts. It is not allowed to connect an external supply and a battery simultaneously. The amp is protected against reversed voltages by D3. The amp is switched ON/OFF by S2.."

 The USB is for the DAC portion, not the amplification portion, AFAIK.


----------



## nightanole

Quote:


  Originally Posted by *revolink24* /img/forum/go_quote.gif 
_Indeed I did read his page.

 "Power is supplied by a 9V battery or a 9 .. 28 Volts external powersupply. The power voltage is splitted by a TLE2426 rail-splitter to create positive and negative powerlines of 4,5 .. 14 Volts. It is not allowed to connect an external supply and a battery simultaneously. The amp is protected against reversed voltages by D3. The amp is switched ON/OFF by S2.."

 The USB is for the DAC portion, not the amplification portion, AFAIK._

 

4 lines down:

 The circuitry around the LM2662 was added to create a negative 5V powerline from the positive 5V USB-powerline to power the amplification section so the amp can be used without battery or external powersupply when connected to USB.


----------



## onyu

sorry double post


----------



## revolink24

Quote:


  Originally Posted by *nightanole* /img/forum/go_quote.gif 
_4 lines down:

 The circuitry around the LM2662 was added to create a negative 5V powerline from the positive 5V USB-powerline to power the amplification section so the amp can be used without battery or external powersupply when connected to USB._

 

Alright, missed that, thanks for the info


----------



## joneeboi

Thanks, Tom. 
	

	
	
		
		

		
		
	


	




 cobaltmute:

 I'd go with Imagineering if I could sign up. 
	

	
	
		
		

		
		
	


	




 I'm from Canada.

 DKJones96:

 Right. It's more likely that the headphones require instantaneous peak power. Max capacitance can go up to 3960uF not including the local decoupling capacitors for the opamps, or 0.198J of energy, or 3.96W for a 20Hz signal per channel. To be safe, I like to use capacitors with higher voltage ratings supposing that the TLE blows up, so with 16V capacitors, max capacitance only goes up to 2160uF, or 0.108J, or 2.16W for 20Hz signal per channel. Add the 1W from the DCP, and you can get up to 5W instantaneous power.

 sources:
http://hyperphysics.phy-astr.gsu.edu...capeng.html#c1
http://chuck-wright.com/calculators/watts.html

 It should be noted that I am not entirely sure of these calculations. Since the rails are split, do I just count the two capacitor banks as though they're in parallel? IOW, does the calculation go:

 capacitance between positive rail and ground + capacitiance between ground and negative rail = total capacitance?

 It's almost like two capacitors in series, so should it be:

 1/(capacitance across positive rail) + 1/(capacitance across negative rail) = 1/(total capacitance)?

 Perhaps this is all moot because no one realistically listens to music that loudly on headphones. How about I recommend that no one listen to their music too loudly?

 Also, the inrush current is being limited by the LC filter on the BantamDAC's USB power input. It also helps to have the amp off when you plug in the USB cord.

 Everyone else:

 There are a few differences between me and Meier. One is that I'm using an existing, well-documented and popular DAC board with my amplifier board. It is a cohesive design that works hand-in-hand with the BantamDAC, and it does away with the whole battery charging/external power hoopla. Those that already have the BantamDAC can make a sweet USB headphone system for a price just a little higher than the Meier.

 Another difference is that he uses an inverting amplifier with adjustable gain, whereas I'm using the "conventional" non-inverting amplification stage with attenuated input. He lists the difference between the two on the web page.

 His power supply uses an inverting DC-DC converter to create a negative 5V rail. I'm boosting the voltage and regulating it to ~10V and splitting it. We both end up at split rails, but mine doesn't change because there isn't a mode for external power. I mean, technically you can power it externally, but let's just say we're doing a standard build of the Carrie USB headphone system. I like to think my way is clever because "virtual ground" is actually earth ground. With some of the amps in this forum, the virtual ground sits above earth ground, forcing you to isolate them from each other. They can sit at the same potential in this design. Plus, with all the huge copper planes in both the amp board and the BantamDAC plus the USB cable and all that, the ground has very low impedance. You may not hear a difference unless you have a GSM phone sitting next to it.


----------



## cobaltmute

Imagineering won't let you sign up? I'm in Toronto and I've talked to them in the past and they didn't have issue (although I didn't order)

 I've used GoldPhoenix before and had OK results. Not as nice as the Imagineering (some pinholes in the soldermask), but tolerable. Their price is excellent though - I got 17 1455C801 sized boards for $100US. Probably a good choice for a protoboard run.


----------



## joneeboi

I'll give Imagineering a call when I want to do the production run. Thanks for that tip.


----------



## Billyk

De we have a BOM yet? I want to put together a mouser order. I will be finished with the bantam for this tomorrow.


----------



## Juaquin

Yeah I'm about 70% done with my Bantam too (fingers crossed that I got the dac chip soldered ok). Definitely looking forward to this, my new macbook pro is looking for a portable friend.


----------



## DKJones96

Quote:


  Originally Posted by *Juaquin* /img/forum/go_quote.gif 
_ (fingers crossed that I got the dac chip soldered ok)._

 

I hate not knowing that until everything is done.


----------



## joneeboi

See if this BOM works.

https://ca.mouser.com/ProjectManager...sID=a5db258b5d

 You have to get the opamps and the potentiometer from AMB, and the RLED+LED combo as well as the knob are things you can tweak.


----------



## Juaquin

Quote:


  Originally Posted by *DKJones96* /img/forum/go_quote.gif 
_I hate not knowing that until everything is done._

 

No kidding. I fried the chip on my first attempt (the 5V leg had a bridge to an adjacent pin that was hidden under the chip). I just finished it and it's all good. Testing it with my SSMH right now, sounds great.

 The BOM works for me. I have the pot already, but which opamps are we using - the "high performance" selections or "extended runtime"?


----------



## joneeboi

This amp is totally all about the high performance. 
	

	
	
		
		

		
			





 No batteries to worry about here.

 I just placed the order for 25 boards from Gold Phoenix for 100 bucks. Wow, that was really easy. I like that. Now who else wants in? Price of the boards will be reduced to 4CAD + shipping. Let's call it...*8 CAD*. My PayPal is joneeboi@gmail.com if you want some. Leave a comment about how many you want.


----------



## DKJones96

I'll take one. It can compliment the finished one.


----------



## Billyk

I am in for two please! Will get a PayPal off shortly.
 Oh yeah, just finished the Bantam and listening to it now, sounds great!


----------



## joneeboi

Getting the parts to me will take 8 business days, so it may take a couple weeks for you all to get the boards. With Canada Post, it can take anywhere under 10 business days. I even expressed something once for 2-3 day shipping, and it took about a week to ship. You never really know with Canada Post.


----------



## Juaquin

I'm in for two. Paypal should show up by the time you read this.


----------



## daBigR--

I'm also interested, I'll be in for two if you can ship internationally. Would you plese let me know ehat the shipping would be to Chile? I'll PayPal as soon as you answer, of course I totally understand if you can't do it.
 Thanx,
 daBigR--


----------



## Forte

Also interested in international shipping for one board to Australia?
 Thanks


----------



## joneeboi

I will be sending the boards as letter mail since they are so small. 4 CAD should cover it for international.


----------



## onyu

If you still have some I'd want 2.

 Thank you.


----------



## nullstring

$30 is too steep for a project that I have no time for right now.

 Thanks for the offer.


----------



## joneeboi

Oh, nullstring, I changed fab houses and the price is reduced to $4 per board plus $4 shipping.

 onyu:

 PayPal me 16 CAD at joneeboi@gmail.com and I'll add you to the list.


----------



## Billyk

Sitting with my laptop typing this listening to a Bantam DAC and Mini3. Sounds very nice, the anticipation is building to be building my self a Carrie.


----------



## ranwill

If you have any left I'd like two. Let me know and I'll fire up Paypal.

 Randy


----------



## Forte

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_I will be sending the boards as letter mail since they are so small. 4 CAD should cover it for international._

 

That is great, thank you very much.
	

	
	
		
		

		
			





 Paypal sent for one board.


----------



## joneeboi

There are still some boards left, so my PayPal awaits.


----------



## Billyk

Don't want to be piggy but I would like one more. I'll wait a bit and see if anyone else wants one. If not by tomorrow...
 I have two in college and this is a great Christmas present.


----------



## joneeboi

I still have over a dozen left, so take 'em before someone else does.

 I should also mention that the $4 shipping charge covers both boards. I won't send them separately so as to reduce cost. Remember that one of the design goals was to have a low-cost amplifier. I've refunded money to everyone who gave me the extra shipping cost.


----------



## keyid

interesting. This would make a great gift and getting rid of the large power adapter for my mini3 would be great.

 Couple questions
 The mouser bom is just missing the switch/pot, opamps (AD8397/OPA690) & phone jack.

 Darn, the Bantam Dac kit seems to be backorder from glassjar.
 Anyone have an assembled Bantam Dac kit bom for mouser?


----------



## nightanole

I ordered one too, now to figure out how to fit my gamma 1 and this thing in one case. Hmm i wonder if a gamma 2 and this thing would work out, or if the dac is over kill for a usb only mp3 256k source?


----------



## Billyk

Ok you will receive a PayPal for one more shortly.
 Give me a few minutes to double check my Mouser BOM and I'll post the shared ID.

The shared BOM for the Bantam DAC ID 6fa99ab37
 Please double check I gave it a quick glance and it looks good and the part numbers are good. Also please note I got the through hole caps from Beezar and they are NOT on this BOM.


----------



## keyid

Thanks Billyk!
 Anyone tried other caps (CL/CR) on the bantam dac, not too fond of wimas. Maybe blackgates nx bypassed?


----------



## Billyk

Quote:


  Originally Posted by *keyid* /img/forum/go_quote.gif 
_interesting. This would make a great gift and getting rid of the large power adapter for my mini3 would be great.

 Couple questions
 The mouser bom is just missing the switch/pot, opamps (AD8397/OPA690) & phone jack.

 Darn, the Bantam Dac kit seems to be backorder from glassjar.
 Anyone have an assembled Bantam Dac kit bom for mouser?_

 

See above for the DAC.
 The jack, pot and op-amps are available from AMB Labs.


----------



## Billyk

Quote:


  Originally Posted by *keyid* /img/forum/go_quote.gif 
_Thanks Billyk!
 Anyone tried other caps (CL/CR) on the bantam dac, not too fond of wimas. Maybe blackgates nx bypassed?_

 

Just missed you!
 I like the Wimas, that being said I have not tried anything else. I am not a huge BG fan... I like them in the diyMod tho.


----------



## joneeboi

keyid:

 Here's my copy of the BOM:
https://ca.mouser.com/ProjectManager...sID=05a3e300f1

 As Billyk mentioned, the other parts are available from AMB Labs. You could make an order with Digikey, but they have that horrible minimum 10 part quantity for orders.

 nightanole:

 I don't know if Carrie will work with the gamma DACs as well as with the Bantam. There just isn't a way to line up the designs unless Carrie were shortened to 40mm long and thrown into the 1455C1201, and I don't know if that's something I'd want to pursue.


----------



## keyid

sent payment for 2 boards


----------



## DKJones96

You can get the opamps from Mouser if you change the dual out. The OPA690 they do actually carry. I'm just subbing the OPA2690 for the unavailable dual but you might as well get the stock ones if you need to order the jack and pot anyways.

 I'm making some other 'tweaks' to the parts list like using the 15v converter and a 12v regulator. Runs the 690 about half a volt under its absolute maximum rating but it gives an extra volt of swing.


----------



## ranwill

Payment sent for 2 boards. Thanks for making them.


----------



## tomb

Quote:


  Originally Posted by *Billyk* /img/forum/go_quote.gif 
_Just missed you!
 I like the Wimas, that being said I have not tried anything else. I am not a huge BG fan... I like them in the diyMod tho._

 

I don't like the Wima's on the Bantam, either. The Vishay-Roederstein MKS's (1.0uf 63V) are superior to anything I've tried - that includes Black Gate HiQ NX's. They have plenty of bass (at least connected to 50K inputs) and are super-quick with plenty of detail.


----------



## joneeboi

Quote:


  Originally Posted by *DKJones96* /img/forum/go_quote.gif 
_I'm making some other 'tweaks' to the parts list like using the 15v converter and a 12v regulator. Runs the 690 about half a volt under its absolute maximum rating but it gives an extra volt of swing._

 

That's a good tweak, DK. It may not even be a bad idea to incorporate that into the original design if everything works out. I think I shy-ed away from the 15V model early on because I misunderstood the power requirement calculations. The AD8397 oscillated at its max rated power supply in the Mini^3 v1, but a few extra volts of swing wouldn't be bad. It would definitely extend Carrie's audience to those with the super high impedance headphones, though the Mini^3 v2 seemed to please that crowd already. Maybe I'll give that build a shot as well.

 Also, the prototype boards are selling quite nicely. Who wants the last one?


----------



## keyid

DK what parts list are you using for 15v converter and a 12v regulator?


----------



## DKJones96

Regulator: 595-TL750L12CLP
 Converter: DCP010515BP


----------



## keyid

Thank you DK, 

 joneeboi it may help to update the first page with the v1.21. 
 Has the v1.21 been prototyped?


----------



## joneeboi

I sent v1.23 to the board house, but parts and numbers are all the same. The main differences between the two are mostly in trace routing.

 I should also note that my BOM for Carrie is for gain 2. I only have low impedance headphones, and even then, gain of 2 is a bit much for my listening levels. I will be getting HD650s soon, so that's all about to change.


----------



## cobaltmute

So I see that the "spec" BOM uses a DCP010512B to get 12V and then that is regulated down to 10V. This option provides 83mA output (limit of the DCP).

 DKJones96 has chosen DCP010515B to get 15V and regulate that down to 12V with 67mA output.

 Anybody tried DCP020509B unregulated? That DCP can put out 222mA at 9V which would seem to best simulate the original Mini^3. Idle current on the DCP is less as well.


----------



## DKJones96

You've gotta be really careful running the DCPs unregulated. With no load on my standalone USB booster using these chips it'll see over 20v completely unloaded. That's even with the 12v unit. I think the most I've seen on it was 26v. However, just adding an LED to the circuit loaded it enough to bring it down to about 19 so you might be alright against start-up surge if you do that. Also, the DCP020509B is a 2w unit, not 1w.

 The option I chose gives you less current but more voltage. People with 300-600ohm headphones will appreciate that one since a +-5v power source isn't gonna push much at all. We're talking .04w per channel at 300ohms. That's only 11.4ma per channel at full power. With a +-6v supply you get .06w per channel at 300ohms. That, however, is 14.2ma per channel. Still under the rating of the DCP. You get phones like my skull candies that are 16 ohm tho and you can easily outrun the DCP. +-6v gives you 1.1w per channel.


----------



## joneeboi

I'll have to second DK on that. If you notice in my BOM (https://ca.mouser.com/ProjectManager...sID=a5db258b5d), the filter caps are rated for 35V because of the voltage they see when the amp is switched off. error401 reported a similar experience in his USB powered CMoy thread.

 Also, the tracking information via Fedex was emailed to me this morning.

http://www.fedex.com/Tracking?action...s=425194257988

 I'll try and get the packages out to everyone as soon as the boards get in. I'll have to check if the boards were made properly, but I'll post pics in any case. They should get in sometime next week.


----------



## Juaquin

So what do you think about 30ohm cans? I'm guessing it would be best to stick with the 12/10V option with the higher current, right?


----------



## nightanole

Quote:


  Originally Posted by *DKJones96* /img/forum/go_quote.gif 
_You can get the opamps from Mouser if you change the dual out. The OPA690 they do actually carry. I'm just subbing the OPA2690 for the unavailable dual but you might as well get the stock ones if you need to order the jack and pot anyways.
_

 



 This is above my head. What is a signal, double and triple? they are all 6 pin with 1 internal channel it looks like. the only diff i can see between the 2 is ones a 5v and ones a 6v on the dual rails.


----------



## Billyk

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I don't like the Wima's on the Bantam, either. The Vishay-Roederstein MKS's (1.0uf 63V) are superior to anything I've tried - that includes Black Gate HiQ NX's. They have plenty of bass (at least connected to 50K inputs) and are super-quick with plenty of detail._

 

Thanks Tomb,
 Been listening to the Bantam for several days now and I really like the sound it makes. I have the Wimas in there hence my comment. My next several will have the VRs in them!


----------



## Nemo de Monet

Quote:


  Originally Posted by *DKJones96* /img/forum/go_quote.gif 
_You've gotta be really careful running the DCPs unregulated. With no load on my standalone USB booster using these chips it'll see over 20v completely unloaded. That's even with the 12v unit. I think the most I've seen on it was 26v. However, just adding an LED to the circuit loaded it enough to bring it down to about 19 so you might be alright against start-up surge if you do that. Also, the DCP020509B is a 2w unit, not 1w._

 

Are you sure about those measurements? I've measured as high as 30VDC with zero load, but as soon as you add _any_ load at all - a 2ma LED, say - it falls down to its specified output, at least with the single-output chips I've tried. I'm not sure what the quiescent current draw of the Mini3/Carrie is, but I strongly suspect it's enough to keep the DCP operating as expected.

 I've still got a whole bunch of those booster boards that nobody wants; I should throw another one together and make some more measurements over the weekend, to try and find the cutoff point where the DCPs start (or stop) producing high voltage.


----------



## DKJones96

I'm not sure what the current draw from the LED i used is. I'll take some measurements tonight. Where you will run into the unregulated issue with this amp is that the power switch doesn't turn off the DCP, it's always on as long as 5v is connected. So when you leave it off it can sit there and charge c2 and c3 to 30v or so until you turn the amp on where that surge will flow into the amp(if unregulated). Now, the caps might discharge fast enough that it won't matter or it's possible the rail splitter can't move enough current for it to be an issue.

 I just realized that I put a 16v electrolytic for c2 on the first build... oops! Don't leave it off I guess.


----------



## Nemo de Monet

Ah, yeah, that would be a problem.


----------



## Billyk

AMB uses 3 ferrites on the Mini-3. I did not see them on the BOM, but thought I saw them on the latest drawing of the PCB. So, are we using the ferrites? If so where can we get some? AMB does not list them separately but does include them with the PCB.


----------



## joneeboi

Very good point, Billy. I will provide them with the boards in that case. The price of the board will remain the same for the prototypes, but I will have to include them in the price of the production boards.


----------



## Billyk

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_Very good point, Billy. I will provide them with the boards in that case. The price of the board will remain the same for the prototypes, but I will have to include them in the price of the production boards._

 

You should not have to be out of pocket for this, the board price is so low that the margin won't absorb it. Can you supply a Mouser number and add them to the BOM. Or at least let me kick in a bit for them


----------



## joneeboi

The thing is that they are only available at Digikey in minimum quantities of 10. It's just not economical for everyone to make a small order at Digikey for the ferrites. There will be 25 boards, and if 75 will need to be purchased at a unit price of $0.10340 with $8 shipping and tax, it'll cost me $16.54 overall, a cost of 66 cents per board. It shouldn't be all that bad if I pay for it myself. It is my prototype after all, and you guys are all helping me out by building the test boards. Shouldn't be a problem.


----------



## keyid

maybe AMB can offer them for purchase?


----------



## Juaquin

I'd be happy to cough up another buck or two for the beads. You could offer them on the side for those who ordered on Mouser and don't want to do a separate order at Digikey, especially with the minimum units.


----------



## joneeboi

I think I will, but not for the prototypes. I suppose you could PayPal me 1 dollar, but ehh. Don't worry about it this time around, people. 
	

	
	
		
		

		
		
	


	




 I just made my Mouser order. Now to make my Digikey order and have everything arrive at the same time. Isn't this all so exciting?


----------



## Juaquin

I can't wait. I put in my order with AMB a couple days ago and Mouser today, so I'll be all set when the boards get here. The one thing I'm worried about is doing the endplates, since the only casework tool I have here is a Dremel. I'm not worried about mine but the other one will be a gift. What was that site that did custom endplates?


----------



## cobaltmute

Maybe I just missed it along the way, but what size are C9-20 (lead spacing and diameter)?


----------



## cobaltmute

Quote:


  Originally Posted by *Juaquin* /img/forum/go_quote.gif 
_ What was that site that did custom endplates?_

 

Home*- Front Panel Express, LLC > Front Panel Service for North America


----------



## joneeboi

Those are 6.3mm diameter, 2.5mm pitch capacitors.


----------



## DKJones96

If you want to order the panels but don't want to do all the measuring don't worry, I already did it.











Fileingy - Free Online File Hosting - MP3 Videos Images Documents ZIP

 On the back it says "Bantam DAC + Bus-Powered Mini3 v1.14" can't really read the last part in the images but that was the version of the first build. You'll need to change it for this one.

 The LED in the front is NOT centered over the led hole in the board. I did this because I wanted the LED centered between the edges of the headphone out and this volume knob, not the centers of the pot shaft and the headphone out. If you want the hole centered over the space on the board change the x coordinate to .9625".


----------



## joneeboi

Thanks for sharing that, David. That's going to be really helpful for me because I hate having to do those annoying mechanical calculations. 
	

	
	
		
		

		
		
	


	




 I'll be sure to add it to the site once I'm finished.

 Also, I added the OPA690ID to my Mouser BOM. Plus, the switched Alps pot will be in stock at Mouser on October 2, 2009, so maybe I can order the AD8397ARDZ from Digikey along with the output ferrites. That way we can reduce everyone's shipping costs and waiting times by ordering from just me and Mouser, and amb might appreciate us leaving his AD8397 stock alone for his Mini^3 customers.


----------



## Forte

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_so maybe I can order the AD8397ARDZ from Digikey along with the output ferrites. That way we can reduce everyone's shipping costs and waiting times by ordering from just me and Mouser_

 


 That would be very much appreciated, is there a compatible headphone jack available from Mouser or is that Digikey/amb only as well?


----------



## Billyk

Quote:


  Originally Posted by *Forte* /img/forum/go_quote.gif 
_That would be very much appreciated, is there a compatible headphone jack available from Mouser or is that Digikey/amb only as well?_

 

That would be nice to know.
 My order from AMB arrived this afternoon and it wasn't until then I noticed I forgot to order the jack! DOH!!


----------



## joneeboi

It is indeed a Digikey part, and I can sell them with the boards. The part is by CUI Inc. called the *SJ1-3533NG*. 

CONN JACK STEREO R/A 3PIN 3.5MM - SJ1-3533NG

 Wow, this Digikey order is shaping up to be bigger than I imagined.


----------



## Juaquin

Haha, might as well go all the way and offer them as a kit


----------



## mp101

Jon, dont bother witht he bead on my boards, I have pretty much 3 full Mini3 kits.


 Just need a Bantam DAC board now, going to order Mouser parts soon.

 Cheers


----------



## Billyk

I will be making a bigger digi-key order than I thought, mouser is out of 0805 Ceramic Chip Capacitors 0805 0.1uF 25volts X7R 10% and the Bantam needs six per board. Said they would have stock in a week though


----------



## tomb

Quote:


  Originally Posted by *Billyk* /img/forum/go_quote.gif 
_I will be making a bigger digi-key order than I thought, mouser is out of 0805 Ceramic Chip Capacitors 0805 0.1uF 25volts X7R 10% and the Bantam needs six per board. Said they would have stock in a week though_

 

Hmm ... several people have contacted me about this. Unfortunately, the link-specific BOM's I make have a disadvantage - they depend on a single part number to work. However, _*any*_ 0805 0.1uf X7R capacitor will work (at sufficient voltage rating and preferrably 10%).

 Use 77-VJ0805Y104KXXCBC at Mouser - they have 13,494 in stock. There are others to pick from, too.


----------



## cobaltmute

For the record, the Ferrites are available at Mouser, pn 667-EXC-ELSA35V

 If you check the very bottom of the Mini^3 parts list page, this is the part that amb spec's

  Quote:


 The L1, L2 and L3 leaded ferrite beads and the B+ and B- board-mount battery contacts are supplied with each Mini³ circuit board, so you do not have to purchase them separately. If, for any reason, you need to replace them in the future, you may contact AMB, or, you may purchase replacements elsewhere. Here are the specifics:

 * L1, L2, L3: Panasonic EXC-ELSA35 
 

The V at the end of the part number is just packaging.


----------



## joneeboi

Perfect, cobalt. That's really helpful. I still gotta make the Digikey order, so if you want a set of ferrites and/or the AD8397ARDZ and/or the ouput jack, I can still sell them to whoever needs them. Drop me a line and let me know what you need.


----------



## cobaltmute

joneeboi, I'll be ordering from both Digikey and Mouser so don't worry about me.

 I was looking at your Mouser BOM - is there are reason your C4/C7/C5+-/C8+- is a 1000pF instead of the 0.1uF that amb specs for that position?


----------



## Forte

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_I still gotta make the Digikey order, so if you want a set of ferrites and/or the AD8397ARDZ and/or the ouput jack, I can still sell them to whoever needs them. Drop me a line and let me know what you need._

 

Put me down for 3x Ferrites, AD8397ARDZ and output jack. Thanks...


----------



## joneeboi

Oh, cobalt, where would I be without you? I don't have a really good answer for you there. I must have added it in error. Stick with the 0.1uF value, everyone. I wonder what I did when I added that part. Should well enough either way though.


----------



## cobaltmute

I've been going through the BOM and got another one for you, which you may want to put into the next run of boards.

 C1 and C2, the input and output caps of the DCP. You've got them listed as 10uF tantalums. The datasheets (DCP01B p13. DCP02 pg 9) have this to say about that:

  Quote:


 For 5V to 15V input devices, a 2.2uF low-ESR ceramic capacitor ensures a good startup performance. For the remaining input voltage ranges, 0.47uF ceramic capacitors are recommended.Tantalum capacitors are not recommended, since most do not have low-ESR values and will degrade performance. If tantalum capacitors must be used, close attention must be paid to both the ESR and voltage as derated by the vendor. 
 

If you were to use a 1206 ceramic (say Mouser p/n 80-C1206C106K3P), you could still run a 10uF part, but get the lower ESR they want with no change in board space.

 And if this has been discussed somewhere, I apologize. May have missed it in reading through the thread.


----------



## Nemo de Monet

Indeed, the various datasheets on the DCP chips are pretty adamant that lower ESR is better than higher capacitance for those positions - to such an extent that I suspect it would actually be beneficial to go with dual ceramic caps in each position, to get the lowest possible ESR.

 I would suspect that the high-value tantalums in the BOM would probably work acceptably, but I also suspect that TI explicitly warn against using them for a very good reason.


----------



## joneeboi

That's fine. I appreciate the input just the same. The input tantalum capacitor has an ESR of 2.5R, but it's paralleled with the BantamDAC's C7. Depending on what you choose for either, you get a really low impedance input capacitance. The same goes for the output capacitors. From page 13,

  Quote:


 If tantalum capacitors must be used, close attention must be paid to both the ESR and voltage as derated by the vendor. 
 

The output capacitors for the DCP are paralleled for the same low ESR effect. However, I'm not sure what the ESR requirement for the output capacitors is.

 I got the Nichicon 1500uF UHN capacitor from Beezar, which has an ESR of 18mOhm. If the input capacitors don't have a sufficiently low ESR, one can mount the capacitors such that you can parallel a few until your DCP is putting out power. You can use both through-hole and surface mount caps to achieve this objective.

 Thanks for bringing that up, cobalt. Now that I think about it, I can't think why I shouldn't just do away with the tants and just get low ESR ceramics in the first place. It'll save space and do away with this whole confusion. I'll keep that in mind for the next run of boards.


----------



## joneeboi

Quote:


  Originally Posted by *cobaltmute* /img/forum/go_quote.gif 
_joneeboi, I'll be ordering from both Digikey and Mouser so don't worry about me.

 I was looking at your Mouser BOM - is there are reason your C4/C7/C5+-/C8+- is a 1000pF instead of the 0.1uF that amb specs for that position?_

 

I remember now. I chose 1.0uF over 0.1uF because it has a lower impedance. See page 9 on the datasheet:

http://www.kemet.com/kemet/web/homep...01_GoldMax.pdf


----------



## cobaltmute

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_I remember now. I chose 1.0uF over 0.1uF because it has a lower impedance. See page 9 on the datasheet:

http://www.kemet.com/kemet/web/homep...01_GoldMax.pdf_

 

But your BOM is 1000pf or 0.001uF, not 1.0uF.


----------



## joneeboi

*sigh* 
	

	
	
		
		

		
			





 Note to self and others: grab the correct local opamp decoupling caps.

 For the BantamDAC, some possible C7 candidates include the Nichicon HZ and HN series. That will keep your ESR low enough for the DCP to stay on.

 HN:
UHN0J152MPD Nichicon Aluminum Electrolytic Capacitors - Leaded

 HZ:
UHZ0J152MPM Nichicon Aluminum Electrolytic Capacitors - Leaded


----------



## joneeboi

That does it, folks. The boards have all been bought. Thanks to everyone that's participating. I'll give everyone about a month to build their boards and send in their comments, and then I'll submit the final design to Imagineering.

 For those of you tracking the boards (here), they have arrived in Calgary, AB, a city three hours from where I live. Unfortunately, Fedex will be closed tomorrow as they observe Labor Day, so I probably won't get the boards until Wednesday at the earliest.


----------



## Juaquin

Sorry if this is a dumb question but I had some trouble following the conversation - will the Carrie work with the Mouser BOM (as of a few days ago) with a stock Bantam? What parts have changed and are they critical? I'll order the new parts on my next Mouser order but that probably won't be for a couple weeks (plenty of projects for now).


----------



## Forte

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_Note to self and others: grab the correct local opamp decoupling caps._

 

Which value should we get, 1.0uf or 0.1uf?


----------



## cobaltmute

The recommeneded minimum for the AD8397 is 0.1uF. If you look at amb's schematic for the Mini^3, C4, C5+-, C7, C8+- are spec'ed to be 0.1uF

 From the datasheet:
  Quote:


 A 0.1 μF MLCC decoupling capacitor(s) should be located no more than 1/8 inch away from the power supply pin(s). A large tantalum 10 μF to 47 μF capacitor is recommended to provide good decoupling for lower frequency signals and to supply current for fast, large signal changes at the AD8397 outputs. 
 

So whatever you can fit on 0.1" lead spacing. The same cap as C1/C2 might be a good choice (Mouser p/n 80-T350E106K025AT) as they are already 10uF Tantalums. I would leave C4 and C7 as spec'ed though - most recommendations I've seen for the rail to rail caps are smaller.


----------



## nightanole

Im curious why we dont have a digi-key BOM? I did a quick check on most of the biggies and it looks like they are all there. Is digikey usa only or something? This whole thing is getting confusing on which parts to buy where and what values of cup caps
	

	
	
		
		

		
		
	


	




 Anyway Im doing something alittle different. I have a gamma 1 lite, and would like to put it in the same case as the carrie. This seems perfectly feasible to me but i wanted to double check. Basically i would have the usb plug of the carrie mounted on a pannel, the 5v would be split between the carrie and hte gamma, and the signal wires would goto the gamma. Then I could have an all AMB usb setup


----------



## Billyk

Use any vendor you want! If you want to put together a Digi-Key BOM that would be great. I order from them quite a lot.I like the low shipping cost on small orders. I ordered a couple of caps and a toslink transmitter 'cause Mouser was backorder and they charged less that $2.00 to ship! Mouser is my usual vendor, don't know why really; I know I love their project manager and some of the prices seem lower.


----------



## joneeboi

I've been juggling taking orders from everyone, making my own orders, getting the website set up on top of getting ready for fourth year engineering and my personal life. I have the BOM right here.

 I noticed another change that'll throw a wrench into some people's orders. I changed the size of the filter inductor on the board, but I neglected to match it up with the BOM. It's too small for the one spec'ed in my Mouser BOM, so I'm going to have to tombstone the one I ordered or grab a smaller value, smaller package from Digikey. I'll change the package in EAGLE for the production run to support larger packages.


----------



## daBigR--

I won't be feeding Carrie from a Bantam DAC but from the line output of a desktop mp3 player (Omnifi DMS1). Any thoughts about that? like checking for anything special or adding/changing any parts to the amp?


----------



## joneeboi

You can panel-mount an input between the output jack and the potentiometer on the front panel. That's why I moved L1L closer to the output jack from the first prototype. There's also room behind the Bantam's output coupling capacitors for a DPDT switch, so you can have switchable inputs. Try something like the EG2400-ND from Digikey. I saw one user saw away most of his Hammond just to fit a BantamDAC as well, so maybe you can do something like that.

 Also, I'm going to make my Digikey order on Tuesday by 4:30PM. Anyone who wants an AD8397, output jack, and/or output ferrites should let me know and send me money before then.


----------



## Billyk

Quote:


 I've been juggling taking orders from everyone, making my own orders, getting the website set up on top of getting ready for fourth year engineering and my personal life. I have the BOM right here. 
 

All I can say is THANKS! for all of your efforts!! It is really appreciated here.


----------



## joneeboi

Thanks, Billy. 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *nightanole* /img/forum/go_quote.gif 
_Then I could have an all AMB usb setup
	

	
	
		
		

		
		
	


	


_

 

Well, it wouldn't truly be an all-amb setup, but it'd be very close.


----------



## nightanole

I was going over the new new BOM. the 690 was missing from the digi key. IS this it?

Digi-Key - OPA690ID-ND (Manufacturer - OPA690ID)

 web says they have over 200 in stock, min quanity 1.


 My only problem now is finding a 10k pot on digi key. I cant find any let alone one with a switch. On that note, why does it need a switch again? Computer off, its off, computer on its gonna route sound to the bantam not the pc speakers.

 Are you going to be taking mouser orders


----------



## joneeboi

The OPA690 is listed at Digikey, but it's also listed as non-stock. That means it's not always guaranteed to be in stock, but you can still get it there for now.

 It's best to get the potentiometer from Mouser or amb. I'm not making any other orders from Mouser unless I absolutely have to. It usually takes two weeks to deliver to me, so it's probably best if you get it yourself.


----------



## daBigR--

I'm in for the ferrites (2 amps), how much will it be?


----------



## cobaltmute

I've made my order from Mouser and Digikey. I ended up ordering about 75% of the parts from Digikey

 the changes I've made to the BOM

 - all Panasonic FC or FM electrolytic caps
 - using a DCP020509 with a 8v reg
 - c1 and c2 are being replaced with 0805 ceramic
 - pot without switch - it will be jumpered on and power down will be removing the USB cable


----------



## nightanole

8volts and 160ma? 1.28watts, 55% eff opamp, 704mw or 352mw a channel?
 10v 83ma? 830 mwatts, 55% eff opamp, 456mw or 228mw a channel?

 Nah im not doing something right.

 the 8397 is only rated at 250ma at 10v into 12ohms
 the 8397 is only rated at 220ma at 5v into 4.3ohms

 so at 10v it can put out 2.5watt into 12ohms, 1.25watt into 24 ohms. ya figure less then a watt into 32 ohms. whats the point of a 2 watt supply at 8 volts?


----------



## cobaltmute

Max current in any config is 150ma due to the current output limit of the regulator. 

 This is HeadFi - the land of overkill. Just look at what a beta22 can do. 

 With this config I bascially have a version of the original Mini^3 that will never be starved for current.


----------



## Nemo de Monet

Quote:


  Originally Posted by *cobaltmute* /img/forum/go_quote.gif 
_Max current in any config is 150ma due to the current output limit of the regulator. 

 This is HeadFi - the land of overkill. Just look at what a beta22 can do. 

 With this config I bascially have a version of the original Mini^3 that will never be starved for current._

 

The land of overkill, indeed. 
	

	
	
		
		

		
			





 Too bad there's no option - and no real room, either - to bias the opamps into class A, eh?


----------



## cobaltmute

Skip some of c9-c20 and you could get the room. 

 But then you'd have to buffer the opamps and you'd be building a Pimeta instead of a Mini^3


----------



## joneeboi

Part of the point of the Mini^3 is that you don't need output buffers because the AD8397 puts out enough current for most low impedance headphones. What headphones are you using and what volume are you listening to your music such that you'd need that much power? Plus, there's the whole bit about class A not making much of a sound difference in opamps. You don't need much gain for low impedance headphones (I could live with unity gain on my Grados and portable buds), and the high gain you use for high-impedance headphones means you don't need much current. The lower voltage chips could be used for low impedance headphones, though my 12V setup works fine with my 32Ohm headphones for all listening volumes.


----------



## Nemo de Monet

Yeah, I was making fun of the whole "Head-Fi, land of gross overkill" thing. 
	

	
	
		
		

		
		
	


	




 Not that I have anything against USB-powered Pimetas, mind you. Or a USB-powered A47, for that matter...


----------



## cobaltmute

Oh, it is definitely not about needing that much power, it is more about the theory.

 The Mini^3 is powered by a 9V battery. This provides 7.4V or 8.6V depending on the number of cells in the battery. In the DCP01B and DCP02, the only one that offers 9V is the chip I chose. I'm choosing to regulate that down to 8V due to warnings about the fact that the DCP can overshoot badly with no load (which is not an issue in what I am doing with not having a power switch on the amp).

 So in this case, the DCP + reg is approximately the 9V battery. And I never have to worry about the current draw of any portion of the circuit.

 And what is the cost to me? About $3 more for the DCP?


----------



## joneeboi

There is a price difference of $4.85 at Mouser, a differential of $6.47 at Digikey between the DCP020509 and DCP010512. I think I'll try loading the output with a ~100k resistor to see if that will keep the output from overshooting the spec. This part of the operation is conveniently omitted from the datasheets. Maybe the DCP will benefit from a small load on the ouput. Either way, I don't think you have to worry about current draw that much. I've turned up my headphones real loud, and I never got it to clip even at dangerously loud levels. Nevertheless, it is your build, and you're free to do what you please. At the least, it'll be a good exploration into the different possible configs with the amp. Maybe someone can get the 5V-5V model and see how the amp operates at really low voltages. The AD8397 is a rail-to-rail opamp after all, and plenty of headphones work well with low-voltage, battery-operated sources like the iPod.


----------



## cobaltmute

I think the issue with the loading is that there is an assumption that you will be switching the power to the DCP, not from the DCP.

 A possible neat way to load the DCP is to use a bi-color LED and have it show one color when the power is plugged in and another when the amp is on. Not sure what all would have to be done to make that work though.


----------



## 454Casull

How about an amp that's USB-powered that also has a USB DAC? One cable in, one cable out.


----------



## DKJones96

It doesn't take much of a load to bring your voltages down to sane levels.

 This amp paired with the bantam is pretty much what you are talking about 454. If you look at the picture of mine a couple pages back you'll see it just has a USB input in the back and a headphone out on the front.


----------



## Juaquin

Quote:


  Originally Posted by *454Casull* /img/forum/go_quote.gif 
_How about an amp that's USB-powered that also has a USB DAC? One cable in, one cable out._

 

DKJones said it but I'll reiterate. If you go back and read the first few posts, you'll see that the Carrie was designed to work in conjunction with the BantamDAC as a unit. Sure, they're not consolidated into a single PCB, but it's better this way in that you can take an already made bantam and hook it up, or use another DAC, none at all, etc. The modular design gives options.


----------



## joneeboi

Oh?

http://dl.getdropbox.com/u/886264/Carrie/DSC_8344.jpg

http://dl.getdropbox.com/u/886264/Carrie/DSC_8343.jpg

http://dl.getdropbox.com/u/886264/Carrie/DSC_8345.jpg

http://dl.getdropbox.com/u/886264/Carrie/DSC_8346.jpg

 I won't send them out right away as some of them need to be stuffed with extra goodies. Nevertheless, boy, are these boards beautiful compared to the last batch. My Mouser order arrives tomorrow, so I might just get one knocked out by the weekend.


----------



## Billyk

Excellent, they look great!
 Placing my Mouser order today, should see it by Monday.


----------



## cobaltmute

Don't wait too long - some of us want to start building soon too. I should be getting both my Mouser and Digikey orders today.

 Just looking at the two boards, it looks like the jack and the pot are in the same position as the first board? I want to verify before I use DKJones96's FPE templates.


----------



## joneeboi

Don't worry. I'm only waiting for the Digikey parts to get here. I'll send them as soon as I can. 
	

	
	
		
		

		
			





 Also, the pot and output jack are indeed in the same position as the previous prototype version, so you can use DK's FPE files. For that matter, they should be identical to the Mini^3, but I can double check that tonight.


----------



## DKJones96

I checked on that as I was putting the template together, they came out to what seemed identical(the first prototype and the Mini3). If they aren't it's nothing that the 1-2mm of board play in the case doesn't make up for.


----------



## cobaltmute

I've been asked about the BOM for my build. So I've attached both the Mouser and Digikey order info. As I built these through the carts, they are not the prettiest. The Digikey one is a CSV I downloaded of my order, but Mouser doesn't do downloads of the data so it's not so easy to work with.

 Again to note, this BOM is specific to if you are running the 8v regulator. The electrolytics after the reg (for example C9-20) are only spec'ed for 10V. If you try using a 10V reg (as joneeboi does) you are in for trouble.

 You'll notice C3 and C6 are missing. I decided to omit them as they do the same function as C7 and C4.

 You likely want to correct LF1 as well as it is the wrong size (as joneeboi pointed out after I ordered).


----------



## nightanole

I hate to ask a n00b question here but this amp brings up a new problem. In my ckIII i set the gain at 4 and its got +-15v rails. This gives me about a 3rd of my volume knobs travel before it gets too loud for my m audio q40 50 ohmers. If im reading correctly, with the 10v stock bom i would get +-5v rails right? If that is the case and my swing is reduced by 6db, should i:
 leave the 10v and 4 gain?
 do 12v and 2 gain?
 do 8v and 2 gain?

 I think the goal is to get the most voltage(non attenuated signal) into the amp and then adjust the gain to be as low as possible and still fully power the cans. However the whole pick you own voltage thing is throwing me off.


----------



## cobaltmute

I've been running about gain 5 on my Pimetas into my 66Ohm Sennheisers. My BOM is gain 5, which is the default for the Mini^3. I orginally ran gain 10 (like the cmoy), but found that I was sitting too low on the volume control and getting into the area of imbalance between the two channels on the pot.

 joneeboi's BOM is unity gain. This is all he needs for his low-Ohm headphones which need more current than voltage gain. HD650 need voltage gain.

 So as you can see, there is a lot of trade-offs. If you know that you are going to stay with lower Ohm headphones, you could goto gain 2 or 3. There is nice chart on the Mini^3 parts list page showing the appropriate resistor values (and the part numbers match this board)

 Second to that is that the position on the knob is in part determined by the resistance taper (as audio pots are not linear). You can check the tapers here. If you went with the RK27 pot for your CKIII, it has the 15A taper as opposed to the switched RK097 has the 3B taper. The non-switched pot that is on my BOM has the 15A taper which seems like it will have more control in the lower ranges.


----------



## nightanole

Ok im trying to turn this into a math problem. I dont know how much power to run to my cans, im assuming a half watt into each channel of a 64 ohm can sounds good? According to ohms law that is 5.6v swing (+-2.8v). If i wanted 1 watt it would be a 8v swing (+-4v). rms that would be 8v and 11.3v. Now given these 2 voltage swings, What do i want my gain and input voltage to be? 

 To me it could be several options for the 8vrms:
 8v regulator with high gain
 10v regulator with med gain
 12 regulator with unity gain

 Or am i not thinking right? Im shooting for the highest voltage with least amount of gain, that i can get the most amount of travel out of my pot.


----------



## cobaltmute

Lets look at the 1W comment:

 Your spec for your headphone is:
 sensitivity:116dB SPL (1mW IEC318)

 116dB for 1*mW*

 Now let's look at the relative loudness chart

 So 1 milliwatt = loud rock concert.

 So your half watt (500mw) swing calculation is probably more than enough for your needs even if you are working on going deaf.

 The Bantam puts out 3.1v point to point at full scale. Probably enough to make you deaf again, but if you want to maximize that your 1/2W output, you need some gain.

 But then again, I'm work and I'd have to spend more time to ensure that what I just said was right.


----------



## nightanole

ya gotta point. I was basing off of the sony v6, 64 ohm, 106db sens half watt. Still if 1 mw makes you deaf then any amp i buy would have 100x the wattage head room. 1mw is only .30 volts. Hell at 300 ohm it would only be .77 volts. That doesnt make any sense on why anyone would need any amplification.

 I guess im still asking my question incorrectly.

 bantam puts out 3.1v. At unity gain the amp would put out 3.1v regardless of power supply voltage of 8,10, or 12v? I guess thats what my question/problem understanding boils down to.


----------



## cobaltmute

Yes, at unity gain, 3.1v in = 3.1v out. The amp then is a buffer, allow more current delivery than the source (otherwise we'd all just plug into our BantamDACs and be done with it).


----------



## nightanole

Im sure this is border line harassment at this point.


 3.1v in, unity gain, 3.1v out, regardless of power supply voltage, correct?
 1.5v in, 2x gain, 3v out, regardless of power supply voltage.

 Its not until i gain the source up past the power supply voltage, that i would have to up the power supply voltage.

 example:
 1volt in, 10x gain, 10v out. I would need to up the power supply voltage to 12v in this case.


 So i would not have to up my power supply until i needed a output voltage higher then the power supply voltage.


----------



## DKJones96

Exactly. You can gain until you start hitting the rails(clipping) and then you need more supply.

 Your clipping point depends on the chip though. Some can swing within half a volt of the rails and others can only do up to a volt from it.


----------



## cobaltmute

As DKJones96 pointed out, op-amps cannot swing totally from rail to rail. The AD8397 goes to within 0.5 volts of the rails. So on a 8V supply, the opamp can swing 7volts

 You may want to look at the output characteristics section of the datasheet. It specifically lists what swing the AD8397 can do at various rail voltages.


----------



## keyid

Im planning to make two carries one with 12v reg, 5x gain and the other default 10v reg, 2x gain for iems. Will 12v reg and 5x gain work well from the bantam 3.1v?
 Is it recommended that the amp not have a on/off switch? or led?


----------



## Juaquin

Quote:


  Originally Posted by *DKJones96* /img/forum/go_quote.gif 
_If you want to order the panels but don't want to do all the measuring don't worry, I already did it._

 

Thanks DK; I used your panels as a template (hope you don't mind 
	

	
	
		
		

		
		
	


	




). I changed the material to anodized black aluminum because I like the look, and it also allows you to do no fill on the engravings since they'll be silver on a black background (saving $5 a panel). I moved the led over it's spot on the board for ease of use and I changed the font and some of the wording to get this:









 The files are here if anyone's interested (I have no idea if they're good until I get them in, so use at your own risk!):
Back
Front

 Cost at FPE (based on the software's estimation, I haven't received a final price yet) is about $15 a panel - so $30 a set. A little expensive for some cutting but you can't put a price on a professional finish, especially if you're going to be using this a lot like I plan to.


----------



## cobaltmute

Good point about the in-fill. I'm building 2 so on 4 panels it saves about $24.

 My front panel:


----------



## DKJones96

Quote:


  Originally Posted by *keyid* /img/forum/go_quote.gif 
_Is it recommended that the amp not have a on/off switch? or led?_

 

The off/on switch is built into the pot if you get the one that the Mini3 is intended to have.

 LED, optional.

  Quote:


  Originally Posted by *cobaltmute* /img/forum/go_quote.gif 
_Good point about the in-fill. I'm building 2 so on 4 panels it saves about $24._

 

I'm starting to wish I went with the black case!


----------



## cobaltmute

Black face with the silver case looks pretty good - Just look at the Mini^3s on the front page at amb's site.

 I'm waffling between the blue and black for the panels....


----------



## Juaquin

Yeah I got the silver cases - didn't even think to get black ones at the time. Oh well, it's easy to switch out later on if I really don't like the look.

 I think the blue panels would look excellent with the silver case.


----------



## joneeboi

It's been a while since I last posted, so I'm just going to blast responses all at once here. 
	

	
	
		
		

		
		
	


	




 Thanks for sharing your panels, guys. You're right, Juaquin, that professional look is going to be worth it. Very nice indeed. For comparison, amb's panels cost $40 a set.

 I hadn't considered the alternate taper potentiometer, cobalt. I may consider following your lead there.

 nightanole:

 As cobalt already mentioned, the opamps will provide additional current sinking and sourcing. Another benefit is the isolation of the output from the input, so the input signal is unaffected for the different output load (headphones) you connect. The 12V 5X gain build you describe should work fine. My gain is set at 2, which will be appropriate for almost all my portable listening.

 Also, I have some pictures of the new assembled board.

 Old and new. The first and second prototypes juxtaposed.
http://dl.getdropbox.com/u/886264/Ca...3/DSC_8516.JPG

 This is L1F filter inductor that supposedly didn't fit. Wow, reading drawings isn't as reliable as I thought.
http://dl.getdropbox.com/u/886264/Ca...3/DSC_8521.JPG

 I was worried U2 wouldn't have enough clearance, but it seems like there's just enough space there with just enough play to save a little power supply board space.
http://dl.getdropbox.com/u/886264/Ca...3/DSC_8524.JPG

 The clearance of the capacitor bank.
http://dl.getdropbox.com/u/886264/Ca...3/DSC_8526.JPG

 There's another shot of the capacitor bank.
http://dl.getdropbox.com/u/886264/Ca...3/DSC_8527.JPG

 Filter capacitor clearance.
http://dl.getdropbox.com/u/886264/Ca...3/DSC_8528.JPG

 The filter inductor's clearance with the case.
http://dl.getdropbox.com/u/886264/Ca...3/DSC_8529.JPG

 L1G clearance. It may need moving, but since it's mounted off the board, it can just be bent a bit.
http://dl.getdropbox.com/u/886264/Ca...3/DSC_8530.JPG

 L1G again.
http://dl.getdropbox.com/u/886264/Ca...3/DSC_8531.JPG

 General shot.
http://dl.getdropbox.com/u/886264/Ca...3/DSC_8532.JPG


----------



## Juaquin

Looks awesome. Can't wait to piece it together!


----------



## Forte

Fantastic work with the clearances, looks great. 

 Never used FPE before but may be tempted to "borrow" one of the posted designs this time if the finished panels look as good as the posted images.


----------



## DKJones96

Looks good! Wouldn't L1G be less of an issue if it is soldered closer to the board?


----------



## cobaltmute

It looks like L1G could go next to L1L for the next revision...


 And it is looking very good.


----------



## joneeboi

According to the Mini^3 site, the ferrite beads are to be soldered off the board by an 1/8". I seem to have missed it by a bit, but moving the bead a bit might be beneficial. And for the production version, I was thinking of changing the soldermask to yellow (Carrie's favourite colour) with black silkscreen. Keep that in mind when making your panel and wiring choices.


----------



## cobaltmute

Gold with black infill would be a nice combo. 





 Order the black case or the silver case with plastic end panels to get black screws and you're set.


----------



## DKJones96

Yellow with a black silkscreen... Time to find a clear case and some UV LEDs!


----------



## joneeboi

Yeah, if only Hammond made a yellow case. 
	

	
	
		
		

		
		
	


	




 I'm sure one could just send it out to be anodized, but that would add a lot of expense to a relatively low-cost project.

 Now is as good a time as any to announce that I sent out the boards with their respective parts yesterday. I only have two to go (you know who you are 
	

	
	
		
		

		
		
	


	




), but for the most part, everyone's boards have left the building. I can't say for certain when they'll arrive because of the nature of the shipping method, but for now, you can wait in anticipation by the mailbox. I'm still waiting on my Bantam boards, but I'll post those pics when I've built them. Cheerio, lads.


----------



## cobaltmute

Cool. That means that I should have the board sometime next week.

 Now just waiting for my custom DAC boards to come back from GoldPhoenix...


----------



## joneeboi

Oh? Do tell. 
	

	
	
		
		

		
		
	


	




 I thought about putting together a separate board for a PCM2707 to go with Carrie, but it was taking a lot of time. I also considered throwing in the WM8740 with the DAC board, but it started getting really complicated. I'm sure it's possible, but I didn't want to spread my attention between two projects like that. Maybe I'll pick it back up when I have more time during the Christmas break.


----------



## nightanole

I dont care about the switch (the pot wont even be soldered onto the board anyway), is there a reason why i couldnt use a 50k pot instead of a 10k pot? I have no idea why some amps use 10k and some amps use 50k. I thought it had to do with the dacs output caps and the pot making a low pass filter that rolled off the highs. However amb uses both 10k and 50k pots.


----------



## cobaltmute

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_Oh? Do tell. 
	

	
	
		
		

		
			





 I thought about putting together a separate board for a PCM2707 to go with Carrie, but it was taking a lot of time. I also considered throwing in the WM8740 with the DAC board, but it started getting really complicated. I'm sure it's possible, but I didn't want to spread my attention between two projects like that. Maybe I'll pick it back up when I have more time during the Christmas break._

 

All I'm going to say until I get the boards is PCM2707->i2s->WM8524 on a board the same size as the Bantam


----------



## nullstring

Quote:


  Originally Posted by *cobaltmute* /img/forum/go_quote.gif 
_All I'm going to say until I get the boards is PCM2707->i2s->WM8524 on a board the same size as the Bantam_

 

that sounds like it should be released as a separate project...

 EDIT: wait, that'd be amazing.

 I'd be able to make my all-in-one device for my laptop.
 nice DAC w/ line out AND SPDIF out, and headphone amp
 If you make that, I'll be in your debt.


----------



## Billyk

Quote:


  Originally Posted by *cobaltmute* /img/forum/go_quote.gif 
_All I'm going to say until I get the boards is PCM2707->i2s->WM8524 on a board the same size as the Bantam_

 

Very interesting... Nice chips, just finished reading the data sheets. I can't wait to see your implementation. Well, I guess I can wait 'cause I have too!


----------



## cobaltmute

Quote:


  Originally Posted by *nullstring* /img/forum/go_quote.gif 
_that sounds like it should be released as a separate project...

 EDIT: wait, that'd be amazing.

 I'd be able to make my all-in-one device for my laptop.
 nice DAC w/ line out AND SPDIF out, and headphone amp
 If you make that, I'll be in your debt._

 

The PCM2707 doesn't do I2S and SPDIF at the same time. The pinouts on the chip are different for the two formats and it would get really messy.

 A thread will come of it once I've tested a board.


----------



## cobaltmute

Quote:


  Originally Posted by *Billyk* /img/forum/go_quote.gif 
_Very interesting... Nice chips, just finished reading the data sheets. I can't wait to see your implementation. Well, I guess I can wait 'cause I have too!_

 

I'm impatient for the boards. That's why I ordered a panel from GoldPhoenix (so I will have extras) to get them quicker.. Now the only issue is that PCM2706/07's seem to be in short supply.


----------



## nullstring

Quote:


  Originally Posted by *cobaltmute* /img/forum/go_quote.gif 
_The PCM2707 doesn't do I2S and SPDIF at the same time. The pinouts on the chip are different for the two formats and it would get really messy.

 A thread will come of it once I've tested a board._

 

huh..
 From what I understand, twisted pear does this successfully..
The USB DAC/Receiver

 It definitely allows for selectable SPDIF/I2S using a PCM2707


 EDIT: in fact, from what I understand, it would be pretty easy to modify any PCB you create to allow me to do SPDIF.
http://www.twistedpearaudio.com/docs...sb_sch_1.0.pdf

 It would require some rock solid soldering though.... so if you sneak in some through holes or whatever.. I would be appreciative.


----------



## mugdecoffee

Quote:


  Originally Posted by *nullstring* /img/forum/go_quote.gif 
_huh..
 From what I understand, twisted pear does this successfully..
The USB DAC/Receiver

 It definitely allows for selectable SPDIF/I2S using a PCM2707_

 

You can't do both at the same time. There is a jumper to select the output. It might be hard to fit the additional SPDIF output on a board that small. On the other hand, it's only two wires so maybe SPDIF test points could be added which would be airwired to the jack.


----------



## nullstring

Quote:


  Originally Posted by *mugdecoffee* /img/forum/go_quote.gif 
_You can't do both at the same time. There is a jumper to select the output. It might be hard to fit the additional SPDIF output on a board that small. On the other hand, it's only two wires so maybe SPDIF test points could be added which would be airwired to the jack._

 

two wires? 
 It is only two wires isn't it..

 I wonder what the 5 connections are for on the schematic.. hrm..
 /me reads the manual

 EDIT: lol, nevermind.
 For some reason I thought SPI was short for SPDIF.. which it's completely not.

 EDIT2: and test points are all I want. However, I no longer understand how SPDIF is connected to the chip... so..
 /me reads the chip's datasheet.


----------



## cobaltmute

Air-wiring the jack the SPDIF would have to be done. The issue is the switching of the FSEL pin to choose the type of digital output. You'll see the lack of space to put a switch and get power there to pull the pin high when you see the board.


----------



## nullstring

I suppose you will publish the layout and I can get my word in or be defeated later on anyway, huh? =)

 Just keep in mind.. that it would be very useful to have.
 I doubt I am the only person who thinks this.


----------



## nullstring

Quote:


  Originally Posted by *cobaltmute* /img/forum/go_quote.gif 
_.... and get power there to pull the pin high when you see the board._

 

what exactly do you mean by that?


----------



## cobaltmute

The FSEL pin is grounded to have the DAC output I2S. You need to pull it high (3.3v) to get the DAC to output SPDIF. That means routing a trace there with power (and there is stuff in between in my layout). Then you also need a switch, jumper or something.

 I'll keep it in mind for R2.

http://www.head-fi.org/forums/f6/grubdac-445155/


----------



## nullstring

Quote:


  Originally Posted by *cobaltmute* /img/forum/go_quote.gif 
_The FSEL pin is grounded to have the DAC output I2S. You need to pull it high (3.3v) to get the DAC to output SPDIF. That means routing a trace there with power (and there is stuff in between in my layout). Then you also need a switch, jumper or something.

 I'll keep it in mind for R2.

http://www.head-fi.org/forums/f6/grubdac-445155/_

 

I would have no problem airwiring the 3.3V.
 if you just put some test pins there for me to do it., 
 and a way for me to disconnect it from ground feasibly >_>


----------



## joneeboi

Just an update on shipping. I sent out the last two sets of boards yesterday morning, so now all anyone has to do is wait. It's great to see the release of the GrubDAC as a complementary board to the Carrie, and now the appeal for this project just doubled, I think. 
	

	
	
		
		

		
		
	


	




 In any case, let's try to keep discussions about the DAC in its thread though I recognize the overlap. You're probably better served reading about the DAC in its own thread than here anyways, but we won't report you if you mention it here. 
	

	
	
		
		

		
		
	


	




 Thanks for releasing your GrubDAC, Eric. What's the story behind the name?


----------



## cobaltmute

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_Thanks for releasing your GrubDAC, Eric. What's the story behind the name?_

 

I've designed three DACS so far that have seen at least a post on a forum. For some reason I like animals. There was the cub1 (an aborted attempt over a Headwize), and then the pup1. I needed a name of a small animal, being a small board. For some reason, grubs (insect larva) came into my mind. Hence the GrubDAC.


----------



## Billyk

Well, it is a cute 'lil bugger


----------



## cobaltmute

Got my boards today as started building. One board has a little void in the mask but nothing major. I am taking pictures along the way so I'll post them later. Nothing cricitcal to speak of so far.

 Had a big What moment as I was trying to figure out what was going on with power on the board. Interesting idea about the power planes.


----------



## cobaltmute

I've got a question about these caps.






 I think, and I may be wrong, that C9,10,11 are from one rail to ground and the C12, C13, C14 are from the other rail to ground (with ground being the trace).

 If that is the case, isn't one set of them marked backwards, being polarized electrolytics?


----------



## DKJones96

That should all be one rail to the ground plane.


----------



## cobaltmute

That what is the point of C15-C20? They are from top plane to bottom plane. There is no other traces to those caps.

 And from what I looked at last nite, C9-11 connect to one plane and C12-14 connect to the other plane.


----------



## DKJones96

Bottom plane GND, top plane V- and the traces are V+?


----------



## cobaltmute

Quote:


  Originally Posted by *DKJones96* /img/forum/go_quote.gif 
_Bottom plane GND, top plane V- and the traces are V+?_

 

Looking at the board picture, and the way the bypass caps are done, I think you are right. I knew I was not getting something right somewhere.


----------



## joneeboi

DK's got it right. Power planes are actually quite common from what I know, but they are quite annoying if you need to desolder anything connected to them. From previous versions, I had the ground plane on top, but in keeping with the Mini^3 tradition, I threw it on the bottom and everything just clicked from there. I did a lot of trace-wiggling to maximize the plane areas.


----------



## cobaltmute

It was which plane was where was confusing me.

 And what I hate soldering onto is dual ground planes - top and bottom. Both sides sink the heat and it is a total pain to ensure that you get a good joint.


----------



## Juaquin

So I got my boards today and built one. Took about an hour, no problems whatsoever. However, in the process it seems I've fried my BantamDAC somehow. The regulators are reading 3.27 and [EDIT, not 6.65] 4.65 so it's not those; I must have accidentally done something to the DAC chip. I'm going to reflow it tomorrow and pray.

 Although I haven't been able to run audio through the Carrie, the power supply section is measuring the correct voltages.


----------



## joneeboi

I guess people are beginning to receive their packages. This is excellent news. I look forward to seeing your builds and hearing all your comments. I received my Bantam boards today, so I will try and get something drummed up for the meet on Saturday. I hadn't thought of the Bantam being red. It'll be a nice complement to the yellow of the future Carrie.


----------



## Billyk

I am hoping to find mine in the mailbox today. My Mouser order arrived yesterday and the Bantam is ready to go.


----------



## cobaltmute

Quote:


  Originally Posted by *Juaquin* /img/forum/go_quote.gif 
_So I got my boards today and built one. Took about an hour, no problems whatsoever. However, in the process it seems I've fried my BantamDAC somehow. The regulators are reading 3.27 and 6.65 so it's not those; I must have accidentally done something to the DAC chip. I'm going to reflow it tomorrow and pray.

 Although I haven't been able to run audio through the Carrie, the power supply section is measuring the correct voltages._

 

6.65 on the 4.75V reg? The Bantam should only ever see 5V from the USB so something is very wrong. The TPS regs don't like more that 6V so I've heard. Max spec on them is 5.5v


----------



## DKJones96

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_I hadn't thought of the Bantam being red. It'll be a nice complement to the yellow of the future Carrie._

 

My original bantam is green with red Wimas on it and the new one I threw together for the first prototype is red with green Vishays. I like the red boards and prefer the Vishays.


----------



## Juaquin

Quote:


  Originally Posted by *cobaltmute* /img/forum/go_quote.gif 
_6.65 on the 4.75V reg? The Bantam should only ever see 5V from the USB so something is very wrong. The TPS regs don't like more that 6V so I've heard. Max spec on them is 5.5v_

 

Yeah that was a typo, it's 4.65 volts, which is within spec. Everything else is measuring fine and I reflowed the DAC so at this point I'm thinking it's a goner, which is lame since I'm dying to try out the Carrie.


----------



## DKJones96

Throw an input jack on it real quick! That's how I initially had mine set up and then I listened to the Carrie while building the Bantam.

 Can you think of any time you held the soldering iron to the dac too long? Any by too long I mean more than 5 seconds. Did you use a bottle of flux when doing the soldering? My first Bantam was what I thought a goner but when I got my new bottle of flux I squirted it along both sides of the dac and simply tapped the individual pins with my iron and it fired right up. Never underestimate the power of flux. Plus, having to boil it off the pins takes from the heat that would normally just venture into your $13 chip.


----------



## joneeboi

One of my Bantams was acting up after I washed it with alcohol. Apparently a piece of some kind of metal fell onto the PCM pins, so it was shorting line to ground. Some careful inspection can go a long way, especially taking macro shots with any of many point-and-shoot digital cameras. Luckily, all I had to do in my case was replace the regulator, which is nice because you don't have to tear your entire board apart.


----------



## Juaquin

Well the DAC was working by itself for a week until I hooked it up to the Carrie, so it wasn't the soldering job. Best I can figure is that I shorted something while testing out of the case, or like you suggested there may be some metal scraps shorting something. I'll flux and clean it with alcohol when I get home and report back. Either way, I have several more Bantam boards and sets of parts on the way so I'll get it right eventually.


----------



## cobaltmute

Getting there:













 Haven't powered them up yet. 

 Waiting on DAC and panels, and the panels won't be ordered until I get the DAC to measure the back ones to ensure the mini-USB placement is correct..


----------



## DKJones96

Looks great! Too bad they all get hidden behind panels.

 How far does the USB port stick out on the DAC you are using? I don't like how far the USB on the bantam sticks out the back of this thing without the plastic surrounds. My end panels won't be in until the 4th.


----------



## TeraHz

When are these boards going to be available for the rest of us? I missed the proto phase as I was busy with my b22 build, but I'd like to put one of these together for at work use.


----------



## cobaltmute

Okay, powered it up off the bench supply and am listening to it with another DAC.

 So far, the sound is very good. Gain 5 is however too much, going to lower it on both units I built.


----------



## cobaltmute

Quote:


  Originally Posted by *DKJones96* /img/forum/go_quote.gif 
_Looks great! Too bad they all get hidden behind panels._

 

FPE does 2mm perspex in clear

  Quote:


 How far does the USB port stick out on the DAC you are using? I don't like how far the USB on the bantam sticks out the back of this thing without the plastic surrounds. My end panels won't be in until the 4th. 
	

	
	
		
		

		
		
	


	



 

If I measure right the GrubDAC will stick out 2mm from the board so on a 2mm panel it will be flush. But I'll have to see fit once the boards arrive.


----------



## joneeboi

Quote:


  Originally Posted by *cobaltmute* /img/forum/go_quote.gif 
_So far, the sound is very good. Gain 5 is however too much, going to lower it on both units I built._

 

How are those pots in the lower volumes? I suspect with such a high gain you're using it only in the quieter regions. Does it have any noticeable imbalance?


----------



## joneeboi

Quote:


  Originally Posted by *TeraHz* /img/forum/go_quote.gif 
_When are these boards going to be available for the rest of us? I missed the proto phase as I was busy with my b22 build, but I'd like to put one of these together for at work use._

 

I still have one leftover from the proto run. PayPal me and I'll get them sent out as soon as I can.

 Also, prototypers, check if I sent you the right amount of materials.


----------



## cobaltmute

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_How are those pots in the lower volumes? I suspect with such a high gain you're using it only in the quieter regions. Does it have any noticeable imbalance?_

 

So far the channel matching seems to be better. Now I've only wired up one board but it seems to me the it is balanced until you just about can't hear it.


----------



## TeraHz

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_I still have one leftover from the proto run._

 

Oh cool. Money sent. Now to go reread the thread and get me a dac for it.


----------



## cobaltmute

Oh, I should add these as a build notes:

The DCP02 I used hangs over the back of the board slightly (maybe 0.5mm). Not sure about the DCP01B, but you may want to move in in just a touch.
I'd turn C12-14 around. Having all the caps in the bank the same way may save some build headaches down the road.
L1G for me only had to be bent in minimally to clear the case

 Other than that the build went very smoothly.


----------



## Juaquin

A small note from my build - I'm sure many people know this, but some people who aren't familiar with tantalum caps (like me) should know that the side marked with the bar and plus sign is the positive side. That should be obvious from the plus sign, but it's hard to see on some of them and is confusing because it's accompanied by the bar, which is usually an indicator of the negative side of a cap. Anyways, I had to look it up to be sure so I thought I'd note that.


----------



## Billyk

I hear you, thank goodness for datasheets. I have to look that kind of stuff up all the time!


----------



## nightanole

Well i got my carrie (anyone notice pcb's look huge on the internet? I think an oreo could give this thing a run for its money) and was going to try a smt build. Not anymore, this dual ground plane scares me. I happen to scrap or burn off any thing on the resistor bank and im screwed.

 2 things. Why is the thermal pad missing from U5? Is the U4 thermal pad even connected to the ground plane for good thermal transfer?


----------



## keyid

got my first carrie/bantam up and running, sounds quite nice. I may need to change my other carrie gain to 2 also, i think gain of 5 will be overkill.


----------



## cobaltmute

Quote:


  Originally Posted by *nightanole* /img/forum/go_quote.gif 
_Well i got my carrie (anyone notice pcb's look huge on the internet? I think an oreo could give this thing a run for its money) and was going to try a smt build. Not anymore, this dual ground plane scares me. I happen to scrap or burn off any thing on the resistor bank and im screwed.

 2 things. Why is the thermal pad missing from U5? Is the U4 thermal pad even connected to the ground plane for good thermal transfer?_

 

The OPA690 doesn't have a thermal pad so it doesn't need the pad on the board. And depending upon which AD8397 you ordered, it may not have the pad either (the one on my BOM doesn't have the pad).

 Doesn't look like the pad is connected, at least looking at my picture of the board.


----------



## nightanole

Well i have electrical potting at work thats the consistency of water and thermally like aluminum. Ill just put a drop on/under each one.


 Hmm if anyone else would like this treatment, im willing to do it for free. I could even put a drop under the 1 watt dcp and regulator. You would just need to pay for shipping to and fro. On the other hand thats like paying 4 bucks for 4 drops of potting.


----------



## joneeboi

Quote:


  Originally Posted by *amb* /img/forum/go_quote.gif 
_Don't worry about connecting the EPAD to any copper plane. It's more trouble than it's worth. Just by using the EPAD variant of the opamp (AD8397ARDZ) gives you quite a bit more heat dissipative capability than the non-EPAD (AD8397ARZ) version. With the lower supply voltages we;re talking about here, it shouldn't get appreciably hot anyway._

 

I removed the thermal pad under U5 because it was unnecessary. I could add it back in for the "just like a Mini^3" effect, but it's just plainly not necessary. Maybe I should have consulted with you guys, but if you want it, I'll put it back.


----------



## nightanole

No harm no fowl. looks like there is no point:

 You could get a set without the Epads (guess you would have to really look at the models spec sheet to make sure) so in that case the thermal pad is worthless.

 Without thermal pad the AD8397 can only dissipate 750mw if its not he epad "D" series.
 Without thermal pad the 690id can only dissipate 750mw too.
 the 690id doesnt come in a Epad version 

 It looks like just getting the "d" series ad 8397 (AD8397ARDZ not the AD8397ARZ listed in the 8v BOM) contains enough extra "stuff in the package ^TM" to help out with the power dissipation without even being connected to the boards thermal pad.


 The reason for my questions were this. 1 the mini 3 had a pad and the carrie didnt. This is explained away since i cant even find a 690id with a epad. 2 the amps epad isnt connected to ground. In all my companies designs that use a epad type, they have epad connected to ground so it can use the entire boards ground plane for a radiator.


----------



## joneeboi

I could still connect it, but part of the worry is the parasitic capacitance. That's why there's the rectangle cut in both the planes surrounding the opamp. It's mentioned in the datasheet. I'm just not sure what will happen if I do connect them, but I guess they have that EPAD there for a reason. It should be able to support a plane-connected EPAD landing pad, right?

 ...right?

 I don't have the cash to do another prototype run unless it's group-bought. I think I'll just leave it there until then.


----------



## keyid

amp is working find but on my OR im getting 80mv spike when I turn off the amp. Anyone else see a spike?

 Just added Cerafines and bypass with sonicgen II's sounds alot better, then cerafines or Vishay-Roederstein


----------



## nightanole

Well i got everything ordered. I felt dirty ordering the capacitor bank of PW series caps with .23 resistance, at least the ripple of 430 will help me sleep at night.

 I looked for like 2 hours and couldnt find a better cap, everything needed a 8mm can.

 The only thing i found that might work was using 2 1800uf nichicon UHZ caps 16v. then it would be .0065 resistance and 4140.

 They are 10x25mm so you would have to lay them on their sides, but it would double the current compaired to the stock bom.http://mouser.com/ProductDetail/Nich...OEjiXz5OfVE%3d


----------



## Billyk

I received my boards yesterday, they look great, nice job!
 I have everything for a stock build with the hi perf op-amps and a stock Bantam with the wima caps. I hope to get it done tomorrow. Depends on my work sched but I think it should be doable. 
 I think my next build will be with the extended runtime op-amps and the Vishay-Roederstein caps in the Bantam. I would love to tkae a shot at the Grubdac cobaltmute has been working on.


----------



## keyid

is it possible for the carrie have a 1x gain and be stable? The 2x gain in the carrie seem to have the same volume travel as my 5x gain mini3.


----------



## nightanole

"do not use other values than listed to maintain low output DC offset and ultrasonic stability. "


 So unity gain sounds bad. Still regardless of what amp, gain is gain, 2x on a 4kw amp is the same as 2x gain on a 1 watt amp.


----------



## DKJones96

Isn't the original BOM for unity gain?

 I was going to build a 3x this time around to match my power supply to the Bantam's output.


----------



## nightanole

The original does have unity gain, but its not amb approved and might cause high feq oscillation. What i do with gainy amps like the starving student is make the stock volume control into a shunt pot. All you need is 2 jumpers and 2 10k resitors and you can reduce the 2x gain down to unity, and improve your sound at the same time. Its the same method introduced in the new zero dac.

Shunt Pot Volume Control - World-Designs-Forum


----------



## Billyk

Is it my poor old eyes or is it hard to spot pin 1 one U4? I am going to guess it goes to R5L. Can someone clue me in?


----------



## keyid

yea the U4 dot is top left, next to R5L. I think there should be a ":" where the dot should go. Becareful of adding to much heatsink compound as it bleeds and may cause a short.


----------



## keyid

can someone convert the .fpd panels into printable template like pdf file?


----------



## Billyk

Got it thanks. It all became clear under the magnifying glass!


----------



## keyid

the bantam smd parts is where I had to take my magnifying glasses out. Almost lost couple parts between the tweezers and eventually used a toothpick with flux on the tip. Also blunt end of the toothpick works great to hold down the smd part while soldering, as most of the smd part itself has some solder already on its ends and needs a quick holding solder.


----------



## Billyk

I'm 55 and the eyesight just isn't there anymore. I usually wear two pair of reading glasses one real strong and my regular strength. Looks pretty silly but works good. Can't tell you how many of those teeny things I sent flying across the room when I squeezed em with the tweezers, hazard of the job I guess. I use toothpick all the time, they make a good precision flux applicator.


----------



## keyid

Toothpicks work great for flux application but takes time to apply to each part esp for smd. I tried to order a flux pen for this but they wont ship using regular mail so I made my own. It works much better then the pen imo. I went to pearl (arts store) and got some bottles with interchangeable metal tips from fine to large. Added some alcohol in a separate tray with some flux chunks and mixed until I could stuff them into the bottle. The alcohol evaporates and im left with flux applicator that dispenses solid flux like tube paste from a fine tip, which i prefer to liquid.


----------



## Billyk

Oh, and another one lives. Just finished the Carrie amp part of the build. It is a stock build right off the BOM with a gain of 2. Don't have the Bantam with me to connect up but am using a 5vdc wall wart and connecting to the output of another DAC. Sounds excellent right now.
 The build went very smoothly. The only issues I had were the pin1 of U4, for my poor eyes the double dots were hard to see, the (+) sign was worn off a bit for CF1. It took me about 2 hours, taking my time and double checking everything. For me this is ready for prime time. I will report back tomorrow when the Bantam is connected. I hope my case arrives today too.


----------



## keyid

congrats! its going sound nice with the bantam. However, the output caps will be a major factor in sound. Like the alien dac, it responds very well to different caps. Im thinking about getting some boutique caps, as my current arsenal of caps used in my carrie doesn't match my alien dac/mini3 combo. Which as blackgates bypass with vitamin q's.


----------



## Billyk

I hear you about the caps, the best caps are no-caps! That is one of the things I like about the choice of using AMB & morsels Mini^3, it's a DC coupled amp, no caps in the signal path so the only caps are the two in the Bantam. I have the Wimas but am going to switch to the Vishays at Tomb's recommendation as the best caps for the Bantam.
 I am protoing a DC coupled version of Nelson Pass's B1, that should sound swell, I like the B1 and taking the caps out of the signal path should make a difference.


----------



## DKJones96

I'm very happy with the Vishay film caps Beezar has for the Bantam. I like them more than the WIMAs.


----------



## keyid

I found the Vishay to be alittle thin especially in the highs but its fast and neutral. With the mini3, I felt the Vishays didnt have enough beef/meat(?) in the sound. For example, the cymbals were too quick and didn't sound imo to a cymbal. It didnt reverberate/bounce back or linger properly. Playing around with bypass caps, I did find sonicaps II to work well as it made the sound sweeter/warmer but also kept the speed of Vishay. -just IMO


----------



## Billyk

I guess my question would be what can you fit in the Carrie? I personally like Mundorf but how are you going to get them in there!?!


----------



## cobaltmute

Quote:


  Originally Posted by *Billyk* /img/forum/go_quote.gif 
_I guess my question would be what can you fit in the Carrie? I personally like Mundorf but how are you going to get them in there!?!_

 

Hammond 1455c1201 the answer? 40mm more length


----------



## keyid

yea the size limits does pose a problem. Was also considering of cutting slots in the casing to expose the caps, this also limits the caps 1.70x.33"
 maybe ill just build that grub dac w/out any output caps as it may end up costing the same as boutique caps


----------



## nightanole

Quote:


  Originally Posted by *nightanole* /img/forum/go_quote.gif 
_Well i got everything ordered. I felt dirty ordering the capacitor bank of PW series caps with .23 resistance, at least the ripple of 430 will help me sleep at night.

 I looked for like 2 hours and couldnt find a better cap, everything needed a 8mm can.

 The only thing i found that might work was using 2 1800uf nichicon UHZ caps 16v. then it would be .0065 resistance and 4140.

 They are 10x25mm so you would have to lay them on their sides, but it would double the current compaired to the stock bom.
UHZ1C182MPM Nichicon Aluminum Electrolytic Capacitors - Leaded_

 

Im weak. I added the caps to my backordered set of opamps that are due in october.

 I should go from a stock 

 From the looks of the board, I just need to add a cap to the c9-12 bank and one to the c15-20 bank.

 the Stock BOM bank is 19.17mohm , 5160ma ripple, 2160uf
 My bank should be 3.25mohm, 8280ma ripple, 3600uf. 

 I think i might of even bested the 10v panasonic fm bank.

 10.83mohm , 5460ma ripple, 2640uf


----------



## joneeboi

Interesting implementation, nightanole. Maybe I'll give it a whirl for the production version if it fits okay on the board.


----------



## cobaltmute

Quote:


  Originally Posted by *nightanole* /img/forum/go_quote.gif 
_the Stock BOM bank is 19.17mohm , 5160ma ripple, 2160uf
 My bank should be 3.25mohm, 8280ma ripple, 3600uf. 

 I think i might of even bested the 10v panasonic fm bank.

 10.83mohm , 5460ma ripple, 2640uf_

 

Total Capacitance of the bank is not that high.

 In the Carrie, we've go 6xcap from V+ to Vgnd and 6xcap from Vgnd to V+

 This puts the two banks in series with each other. For my 220uF FM caps that makes a bank of 1320uF and 1320uF in series. Or 660uF in effective total for the whole bank (if I did the math right).


----------



## nightanole

Isnt it 6 caps from +5v to neutral ground and 6 caps from v ground to -5v. 12 caps in parallel across 10v rails? Wouldnt that be considered parrellel if it werent for a neutral ground center tap? Or should i not compare this to a transformer center tap?


----------



## joneeboi

I think the opamp sees both banks in parallel. Both maths are right, you just need to state how you're comparing the rail banks. If you're talking series from V+ to V-, you take half the capacitance. If you are talking about the banks in parallel, you add them. But if we're speaking relative the opamp, it sees a parallel connection of banks from which it can draw energy. Again, someone correct me if I'm wrong.


----------



## cobaltmute

The opamps have no sense of ground. They pull from V+ and V- and the bank is in series between the two rails with 6 caps each.

 "Capacitors on the Output of a Virtual Ground Driver" on Tangent's Virtual ground page explains more, especially the last paragraph of that section.


----------



## joneeboi

Riiight. Hadn't thought of that. For that matter, maybe I should throw some of those caps across the rails. There's already CF2 across the rails, but more capacitance would be helpful for the instantaneous currents to the opamps. Hm...


----------



## nightanole

Well lets do a single bank of 6 for giggles.

 Stock pw's:
 38.3mohm 2580ma 1080uf


 panasonic FM:

 21.6mohm 2730ma 1320uf

 single UHZ:

 6.50mohm 4140ma 1800uf


----------



## cobaltmute

Before you get too capacitance happy, start thinking about in-rush current. I just measured my Carrie at pulling 1A at startup. Windows 7 shuts the USB port down...


----------



## nightanole

hmm well you do have the 2 watt converter version. The 1 watt peaks at 500ma. I ordered both the stock caps and the 2 that i found.

 At some point someone is gonna say bypass the usb converter and use a 12v tread


----------



## DKJones96

Wait, 1A? The regulator shouldn't be able to flow that at all since it's rated at 150ma. Fortunately, there is 2.5 watts available through the USB and we are only using 1w of it with the DCP, even running double capacity it should still be OK. Close, but nothing obscene like 1A.

 Maximum startup current from this amp plus whatever capacitors used in your dac charging are causing issue?


----------



## cobaltmute

Quote:


  Originally Posted by *nightanole* /img/forum/go_quote.gif 
_hmm well you do have the 2 watt converter version. The 1 watt peaks at 500ma. I ordered both the stock caps and the 2 that i found._

 

Good point at the 2W convertor. Though it in theory should output 0.222A. Apparently in that first split second it takes everything a second to really settle down. If I had used the switched pot, I could plug in the USB and then turn on the rest of the amp.

 Try to figure out how to current limit the startup as once it is active, the Carrie is pulling 70mA in my configuration.


----------



## cobaltmute

Quote:


  Originally Posted by *DKJones96* /img/forum/go_quote.gif 
_Wait, 1A? The regulator shouldn't be able to flow that at all since it's rated at 150ma. Fortunately, there is 2.5 watts available through the USB and we are only using 1w of it with the DCP, even running double capacity it should still be OK. Close, but nothing obscene like 1A.

 Maximum startup current from this amp plus whatever capacitors used in your dac charging are causing issue?_

 

Yup, 1A measured by, 

 - disconnecting the Carrie from the DAC
 - attaching the bench supply to the Carrie (5V, 4A)
 - placing my Fluke in between to measure current and turning on peak hold.
 - turning on the power to the bench supply (only way I can switch it as my Carrie is unswitched)

 I don't get how it is pulling that much.


----------



## nightanole

Ya know i went over the cap bank again. In the mini 3 the cap bank is across the rails, with just a 100uf at the rail splitter. This amp is just the opposite. 

 Im wondering if i should just shove ambs 100uf caps in c9,c18 and pop my big 2 caps across the rails.


----------



## DKJones96

What regulator are you using?


----------



## joneeboi

Do you get that 1A inrush current if you use a switch? Where are you connecting your Fluke? You mentioned 0.222A, so I'm guessing you saw 1A at the DCP output. The differences are the DCP02 and the non-switched pot, so there is already two methods of inrush current limiting that will remain in the final version.

 I'm not an expert in bench supplies, so I'm just curious: is some of that inrush current because of your power supply turning on? Does it make a difference if you apply power while it's still on versus switching it on? Also, isn't the power present in the USB port before you plug in the cable? If so, there could be a difference between your bench test and the actual plugging in of the cable in the computer.

 That 70mA figure you're getting, is that quiescent current? Could you clarify what you mean there?

 It seems I didn't think deeply enough into the capacitor banks, so that's something I'm gonna have to revisit.

 Finally, thanks for the comments and for pushing the limits of the design. This is all useful stuff for the final version. I think I'll plugboard the power supply to see what works best.


----------



## cobaltmute

Quote:


  Originally Posted by *DKJones96* /img/forum/go_quote.gif 
_What regulator are you using?_

 

TL750L08CLP


----------



## cobaltmute

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_Do you get that 1A inrush current if you use a switch? Where are you connecting your Fluke? You mentioned 0.222A, so I'm guessing you saw 1A at the DCP output. The differences are the DCP02 and the non-switched pot, so there is already two methods of inrush current limiting that will remain in the final version._

 

No way to put in the switch now. The 1A was going into the DCP02. By datasheet it only says it can output 0.222A

  Quote:


 I'm not an expert in bench supplies, so I'm just curious: is some of that inrush current because of your power supply turning on? Does it make a difference if you apply power while it's still on versus switching it on? Also, isn't the power present in the USB port before you plug in the cable? If so, there could be a difference between your bench test and the actual plugging in of the cable in the computer. 
 

When I had the Carrie powered through the DAC, Windows would shut the port down the minute that I plugged the DAC in. Now that being said, there was still power to the DAC as the power LED was on, but it would not show up in device management.

 Tried taking the power off the Carrie and putting it back on while the bench supply was on. Much more reasonable now, but still 542mA. Combine that with the startup of the DAC and it is still drawing too much.

  Quote:


 That 70mA figure you're getting, is that quiescent current? Could you clarify what you mean there? 
 

Yes. I am measuring this by powering the Carrie from the bench supply and measuring current with my Fluke (an old 8024B).

  Quote:


 Finally, thanks for the comments and for pushing the limits of the design. This is all useful stuff for the final version. I think I'll plugboard the power supply to see what works best. 
 

No worries, this is what prototyping is for.


----------



## nightanole

I convinced myself that cobalt mute is correct on the power supply with the caps in series. As it stands we are charging 2 banks of 6 caps to 5v, not 12 caps to 10v. Due to this we are also loosing half our reserve power. So we have caps that are way over rated in voltage that are also half the capacity of the original mini 3. the mini3 has 2 470uf caps in parallel across the rails. If cobalt is correct with his calc, even hsi 220uf bank is only charging to 600uf or so.


Capacitors in Series


----------



## cobaltmute

The overvoltage on the caps is a good thing.

 Think about it this way - if the TLE2426 blows (which has happened), the caps see the full rail to rail voltage. That's why in my case I did 10V caps for the 9V DCP02. If you have the DCP010512 that joneeboi specs, I'd make sure that you'd have at least 16V caps.


----------



## DKJones96

Out of curiosity, what are the ferrite beads for?


----------



## cobaltmute

Quote:


  Originally Posted by *DKJones96* /img/forum/go_quote.gif 
_Out of curiosity, what are the ferrite beads for?_

 

This discussion degenerates, but here is quickest reference I know about.


----------



## joneeboi

Wow, and to think that he posted in this thread...Yikes.

 In a word, stability.


----------



## DKJones96

Got a part number for them? I somehow neglected to order them... lol


----------



## cobaltmute

Ferrite Beads


----------



## Billyk

My Carrie lives, just need to do the end panels. I am listening to it as I type. I am using ASIO4all, Carrie with all stock parts from the BOM and Wimas in the Bantam, Sennheiser HD-515. I like the sound, plenty of authority on the bass, even mids and nice if not sparkley highs, I am not a fan of hot highs anyway. I'll let it run in for a few days and report back on the sound.
 Being concerned after reading the posts about draw, I went and plugged it into 5 PCs and two laptops. I did not have an issue with the USB ports shutting down. The PCs were Dell Optiplex and the laptops Dell Latitude. I left it powered on let it discharge for a few minutes between attempts. I do not have a setup to allow me to capture the current draw.


----------



## daBigR--

The Carrie PCBs have just arrived, but my Mouser order hasn't  I just hope it arrives later today or tomorrow so I'll be able to work on the assembly during the weekend. I'll let you know when they're up and running.


----------



## daBigR--

joneeboi, I think the channels may be reversed on the phone jack. AFAIK on a stereo TRS connector the tip should be the left channel, the ring should be the right channel and the sleeve should be ground. Of course I may be wrong but maybe others can check too.


----------



## cobaltmute

I saw that yesterday but did not have a chane to really look at it. You can always wire the input in reverse to make up for it.


----------



## Billyk

Testing on my laptop puts the channels in the correct configuration. I did not notice this before as I always set L & R through ASIO4all out of habit. But I checked using default drivers and the windows setup and configure options and it checked out. Hmmm...


----------



## joneeboi

Quote:


  Originally Posted by *amb* /img/forum/go_quote.gif 
_I think you have the left and right channels reversed at the headphone jack._

 

This was addressed before. See the SJ1-3533NG's datasheet.


----------



## daBigR--

of course you're right, must remember to check the datasheet before opening my mouth. sorry.


----------



## joneeboi

I talked to my power electronics prof this morning, and to solve the overvoltage and inrush current problems, he suggested looking into putting a resistor, thermistor or varistor somewhere before the VREG somehow. To keep the voltage down, the DCP just needs to be loaded some so that it never drops below 10% load (see the datasheet's page 5 and 6 for the Vout vs. LOAD for some context). I hope there is a solution that will only require one part, yet there will inevitably be some inefficiency involved with trying to tame the DCP.

 I just got my HD650s, and I found my gain of 2 was fine for it. I don't know how well the sound mates with it, but fiddling with that will have to wait for now. Either way, can anyone echo my experience? I think using the lower voltage DCP will actually be better because I don't need that much voltage gain, but I think builders will eventually choose their own voltages and gains anyway.

 I hope your builds are coming along okay. Can't wait to see the pictures and faceplates.


----------



## Juaquin

I'm still messing with the Bantam part, but I did get the Front Panels in today. They look great. The only thing is that the edges (corners) protrude a bit too much outwards and require a little bit of hammering to get them into the plastic gaskets of the case. I also had to dremel the volume pot hole a bit to get a good fit. Otherwise everything is good. Once I get the Bantam in condition this will be one awesome little device.


----------



## cobaltmute

I'm away for the weekend but I've been thinking about the issue. There is a lot of capacitance on the board. CF1/2 and C9-12 make 14 220uF caps. There is also two more cap positions that I didn't install. I'm considering halving the c9-12 bank and seeing what happens. I may lose some capacitance but I think it is still more than the original if I remember correctly. 

 What is good about all this is that now someone has tried it and itt can be documented for the future.


----------



## joneeboi

I could probably do away with half the capacitors so I can end up with more supply capacitance and make room for other things. I checked it out in EAGLE, and there is room for the two giant Nichicon UZ caps and then some. I've been thinking of shrinking CF1 and CF2 anyways because, in all honesty, there's nothing good about having such a low corner frequency on the filter. >1kHz corner for a 800kHz signal? Part of the reason TI used such a high switching frequency for the DCP is so that we can save board space with smaller filtering components. I should take them up on that offer and make room for things that might benefit from it. The TLE2426 needs a few uF on its output to stay stable, but nothing near what I'm putting on it now. That's also my bad. We'll reallocate resources and make the power supply a bit more foolproof.

 Extra work (do not attempt unless you know what you are doing):
 Add a 1/2W ~500R resistor (or 1/4W 1.5K if you don't have something similar) from line to ground just at the output of the DCP, and shut off the amp. Power things up (USB plugged in, amp off), and see what kind of voltage the DCP spits out. Then, read the inrush current when you turn on the amp, which will be very helpful in determining the best way to stabilize the chip. See what your results are, and report back here.


----------



## nightanole

Personally I think you only need 1 UZ cap, that right there is much lower in esr and 2x higher in capacitance then the original mini 3. Plus Mr. regulator is only rated at 150ma.

 Ps would this whole power thing go away if we just make it so it doesnt turn off? Its a non bias'd opamp, how much power are we really wasting just leaving it on? The gamma 1/2 sucks 100-200ma all the time and no one cared about a of switch. 100ma at 5v is isnt much, even a normal usb keyboard draws 40ma.


----------



## joneeboi

Part of the reason to have more capacitance is to supply instantaneous energy to the opamps for those unpredictable spikes in music that may draw more power than the DCP can supply. Now, I'm not sure what the "current" agreement is between the opamps and the battery in the Mini^3, but I'm more or less just trying to align what the headphones need with what this power supply is able to give. I'm not sure where the line is between necessity and excess, so further comments/calculations are appreciated.

 Regarding the switch, I think it ultimately helps with inrush current as evidenced by cobaltmute's experience. With that relatively large capacitor bank and the high power capability of the DCP02, he experienced a huge amount of inrush current that spooked his Windows 7. I agree that we're not wasting that much power, but I think there are other factors that come into play. I like how my prof described amplifier design. He said, "It's a _multi-dimensional_ optimization problem," and then he showed us the amplifier design octagon. You have to balance between

 - Linearity
 - Gain
 - Supply voltage
 - Voltage swing
 - Speed
 - Input/output impedance
 - Power dissipation
 - Noise

 and make sure you choose your priorities. What we're dealing with now is power dissipation and a little bit of voltage swing and supply voltage. While I myself don't really care to shut off my amp to save power, I do think that USB power is one of the biggest hurdles in this type of amplifier. Part of the reason why people stay away from USB is because of its noisy and limited nature, so harnessing it the best we can will do well not only for builders/owners/listeners of the Carrie amp but also for future amp designers (as cobalt mentioned). Therefore, while the DCP01 and switch both provide current-limiting, it would still be nice to accommodate the folks who want to use the switchless, better tapered Alps pot.

 Now that I think about it some more, the DCP size is probably the biggest issue. I've plugged the same Carrie into my Windows 7 laptop with the switch closed, and the OS has never complained about power.


----------



## joneeboi

Here's a little tip for dealing with the quieter levels with the stock pot: turn down the level on your computer and turn up the pot. This moves the pot out of its less useful region of travel, and there isn't any real "decrease" in sound quality.

 *continues to groove to John Mayer in LA on his HD650s*


----------



## nightanole

I might get in trouble for this, but i have an extra volume control w switch for $4 shipped. Im not making any money on it and i got it directly from AMB.


 In other news i was thinking about power and gain. It seems most people are using a gain of 2 and i assume headphones under 100ohm. Now Mr. bantam puts out 1vrms (2.95pp)

 Now take my 64 ohm headphones with a gain of 2. thats 63mwatts(126mw for 32ohms) per channel, at full volume, with a voltage swing of 6 volts. 
 Now the stock PS can support 5 watts total.
 Now the calculated output of the 10v version was "RMS power requirements demand (7.07V^2)/32 Ohms or 1.56W per channel." Shouldnt it be .39watts? isnt the rms conversion "(rms sqrt2) x 2" that would mean 7.07rms x 1.414 = 10vp x2=20v swing? Shouldnt it be 10vpp x .707=7.07v /2= 3.535vrms?


----------



## nightanole

Guess what fits in an over sized gamma 2 box?




][/url]


----------



## Billyk

That's pretty cool!


----------



## joneeboi

Quote:


  Originally Posted by *nightanole* /img/forum/go_quote.gif 
_ Now Mr. bantam puts out 1vrms (2.95pp)_

 

1Vrms is 2.83Vpp.

  Quote:


  Originally Posted by *nightanole* /img/forum/go_quote.gif 
_ Now the stock PS can support 5 watts total._

 

I did that calculation all wrong. The opamps won't receive as much capacitance as I originally thought, so the power is a lot lower than that. Remember to differentiate between RMS and instantaneous power here as well. The USB can only provide 2.5W.

  Quote:


  Originally Posted by *nightanole* /img/forum/go_quote.gif 
_Shouldnt it be 10vpp x .707=7.07v /2= 3.535vrms?_

 

10Vpp/sqrt(2) = 7.07Vrms

 Prms = (Vrms^2)/R = (7.07Vrms^2)/R

 Double it for stereo. For 32Ohms, rms power is 3.125W. For 300Ohms, rms power is 0.333W. For 64 Ohms, rms power is 1.56W.

 Realistically, even though the AD8397 is an R2R opamp, it doesn't reach exactly to the rails, so the power and voltage numbers will be slightly lower. In any case, use with low impedance headphones at super loud volumes requires two extra DCP010512B which have to be stacked. I think the synchronization is alright up to eight parallel connections, but I'd have to double check that. At reasonable listening levels, 1W should be fine, but again, I'll have to check that later.


----------



## nightanole

Vp/sqrt(2) = Vrms

 Not Vpp/sqrt(2)=Vrms

 Think of it as ac power. You have 10vacpp. You run it thru a full bridge rectifier. You now have 5vdc peak. You then convert the 5vcd to rms by dividing by the square root of 2. You now have 3.535v of pure dc power.


----------



## joneeboi

Right, Vp. I messed up.

 At 10V, the 8397 has a minimum voltage swing of 9.35Vpp with a 25Ohm load. That's a drop of 0.65V, and my power supply sits at +/- 4.73V or 9.46Vpp. With about a 0.65V distance from the rails, I get 8.81Vpp, 4.405Vp, 3.11Vrms.

 P = (3.11Vrms^2)/25 (just to be consistent since the datasheet uses 25 Ohms)
 P = 0.387W, 0.774W stereo.

 Did I get that right? Maybe we're in the clear after all...


----------



## DKJones96

If you are trying to get really specific you have to take a lot of variables into account. Such as your real bottleneck, the rail splitter. According to the datasheet the absolute maximum from that splitter at 10 volts is 100ma. That's 1 watt from the power supply no matter what you do. Now, that 100ma is split between 70ma v- and 30ma v+ so to stay with an even split between the rails and virtual ground you can only use 60ma assuming that it's an even split between the two until you hit the 30ma limit and it just starts swinging the virtual ground towards v-.

 Personally, I'd rather stick with the capacitor setup as it is as it should help promote a more stable virtual ground than just letting it float while the rails get full capacitance. Not an issue if the unit isn't loaded but once it gets under heavy load you can start to have issues.

 Soooo, stable power from the supply is only .6w total.


----------



## nightanole

Looks right to me and my fellow Jr. CET. Another thing you can check out is how many amps the stock battery of a mini3 can put out. I know non rechargables cant put out much at all, not sure about nickel metal ones. All i know is the stock mini3 has a 1 amp reg and this one has a 150ma reg.


----------



## cobaltmute

I'm not going to get into the math, 'cause I don't know it.

 About the caps, if we look at the Mini^3, amb has 2x470uF rail to rail and 1x100uf from each rail to the virtual ground. I think this is a good standard to look at given how thorough amb is with his designs.

 If you were to use 10mm caps (5mm lead spacing), you could use 2x 470uF 16V Panasonic FC for the rail to rail. In this size, I've also seen a 820uF 16V Nichicon polymer for those that want to go over the top. 
	

	
	
		
		

		
			





 This would also take up half the space of your current bank with more "available" capacitance. The rail to ground caps are an easy fit as well. That also gives you more room to play with for layout.


----------



## cobaltmute

Quote:


  Originally Posted by *DKJones96* /img/forum/go_quote.gif 
_If you are trying to get really specific you have to take a lot of variables into account. Such as your real bottleneck, the rail splitter. According to the datasheet the absolute maximum from that splitter at 10 volts is 100ma. That's 1 watt from the power supply no matter what you do. Now, that 100ma is split between 70ma v- and 30ma v+ so to stay with an even split between the rails and virtual ground you can only use 60ma assuming that it's an even split between the two until you hit the 30ma limit and it just starts swinging the virtual ground towards v-.
_

 

Remember that the only thing the rail splitter sink/sources is the currents from the source device + it sets the ground reference voltage for the ground opamp. The actual ground op-amp current is all sourced from the rails, not the TLE2426.


----------



## DKJones96

So the 2426 is just replacing 2 resistors because it doesn't actually flow anything? Now this raises another question, if the opamps run totally independent of virtual ground except for the ground amp reference, why even bother with a virtual ground? Can't you just make the reference at the ground amp and do away with it?

 I've been messing with class A too much, this stuff is starting to confuse me.

 On a side note, Mouser is 2 weeks backordered on the 2426 in the bom.


----------



## cobaltmute

Right from the Mini^3 page (bolding mine]:

  Quote:


 3-channel active ground topology

 * Similar in concept to the celebrated M³ and the reference class β22 (3-channel version), the Mini³ is also a 3-channel active ground design.
 * In addition to the left and right channels, the "ground" wire of the headphone is actively driven by a third channel. The ground channel amplifier sources or sinks the return current from the transducers, which would otherwise have been dumped into signal ground or power supply ground. *This shifts responsibility for the high current reactive load of the headphones from signal ground to the power supply rails*, thus removing the primary source of signal ground contamination.The headphone transducers "see" active amplifiers on both sides, rather than an amplifier on one side and a capacitor bank of the power supply ground on the other. This results in lower output impedance, greater linearity and reduced stereo crosstalk. 
 

So yes, it replaces two resistors, but it does it very well. 
	

	
	
		
		

		
		
	


	




 It also takes up about the same amount of space, is not prone to the offset of the resistor divider and all that other stuff that Tangent says in his tutorial.


----------



## cobaltmute

Quote:


  Originally Posted by *DKJones96* /img/forum/go_quote.gif 
_So the 2426 is just replacing 2 resistors because it doesn't actually flow anything? Now this raises another question, if the opamps run totally independent of virtual ground except for the ground amp reference, why even bother with a virtual ground? Can't you just make the reference at the ground amp and do away with it?_

 

But how do you make that reference? By grounding the input of the opamp. And what do you ground that to unless you use a virtual ground or a DCP010505DB which provides two rails and a ground.

 And it does flow something - the current required for the ground of the source signal.


----------



## DKJones96

I get the gist of it but how does the ground amp handle the incoming signal? Is it just canceling it out or does it absorb the signal? If the input to ground does low the ground amp just pushes high right? If that's the case, how do we end up with a DC offset? Wouldn't the ground amp see that and correct it?

 Looks like my push-pull tube hybrid Nikko gets an active ground this week so I can fully understand this.


----------



## cobaltmute

After removing C12-17 and replacing them with a single 330uF across the rails, I now have a GrubDAC powering the Carrie.





 Still have to change it to get the gain down to 2. Not in the mood to do that right now as I was having a horrible soldering day and killed a bunch of pads trying to redo the capacitor bank. That's also why V+ is going under the board.


----------



## cobaltmute

Something is on the edge. Unplug from the USB, wait and plug in again, Windows kills the port. Disable and Enable the USB controller in device manager and stays up fine.

 Troubleshooting is going to be for tomorrow Sleep is calling me...


----------



## cobaltmute

I've got a question from what I can see looking at the board (and I'm too tired to go looking for it through the thread).

 - 0V input from the USB side looks to attached to the ground plane.
 - The output from the TLE2426 is also attached to the ground plane.

 Doesn't this defeat the isolation in the DCP? Shouldn't the USB ground and the board ground be separate?


----------



## joneeboi

The ground can only connect the way it is _because_ of the isolation in the DCP. What I've done is boosted the voltage, regulated it, and split it with the centre connected to ground. In non-isolated DC/DC converters, output ground is connected to input ground, and if we were to power a virtual ground amp with that kind of power, the virtual ground would sit several volts above earth ground. As it stands now, V- is sitting below earth ground, V+ above and virtual ground connected to earth ground, mimicking a true split rail power supply. This way, we can connect the enclosure to the USB ground/earth ground, the Carrie ground and the BantamDAC ground together for a really low impedance reference voltage. My laptop power supply connects its output V- to earth ground, so everything is being referenced relative the earth. I hope this is clear.


----------



## cobaltmute

Quote:


  Originally Posted by *cobaltmute* /img/forum/go_quote.gif 
_Something is on the edge. Unplug from the USB, wait and plug in again, Windows kills the port. Disable and Enable the USB controller in device manager and stays up fine.

 Troubleshooting is going to be for tomorrow Sleep is calling me..._

 

Had a thought overnite and plugged the Carrie into a another laptop (Dell with Win7). No problems at all. Unplugged, waited and plugged in again - no issues.

 Apparently my Thinkpad X61 is touchy on the USB ports.


----------



## cobaltmute

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_The ground can only connect the way it is because of the isolation in the DCP. What I've done is boosted the voltage, regulated it, and split it with the centre connected to ground. In non-isolated DC/DC converters, output ground is connected to input ground, and if we were to power a virtual ground amp with that kind of power, the virtual ground would sit several volts above earth ground. As it stands now, V- is sitting below earth ground, V+ above and virtual ground connected to earth ground, mimicking a true split rail power supply. This way, we can connect the enclosure to the USB ground/earth ground, the Carrie ground and the BantamDAC ground together for a really low impedance reference voltage. My laptop power supply connects its output V- to earth ground, so everything is being referenced relative the earth. I hope this is clear._

 

Even with the picture, it took me a few moments to grasp what you did here.

 In this case, does the TLE2426 really sink anything at all? Since ground is USB ground, the TLE2426 basically just pulls the rails of the DCP to center around real ground.


----------



## cobaltmute

I'm going to recant that last post.

 I metered that Carrie alone at pulling 70mA of idle current

 Let's do some math on that
 DCP020509 = 23mA
 AD8397 = 9mA/amp = 18mA
 OPA690 = 6mA
 TLE2426 = 150 microA
 TL750L08CLP = 1mA

 Total should ~= 51ma (23ma for the DCP + 25mA*1.15 for efficiency loss in the DCP for the on board components).

 Where is that other 20mA going?

 Now let's look at this picture:





 What happens when you remove the AGND from the 0V pin of the DCP?

 We still get a dual rail supply for the components after the TLE2426, but it isn't burning current trying to get the rails to center around the 0V point on the input.

 In fact, replace the DCP with a 9V and it will be the same as the Mini^3.


----------



## joneeboi

That's a good point. I'm thinking about the load capacitance on the TLE. The PIMETA v2 gets away with very little capacitance on the output, and the Mini^3 puts two 100uF capacitors on it. We could probably put very little across it in this case, providing more room to the rail-to-rail capacitors.


----------



## cobaltmute

I should note that based on what I just said above, on my second board I'm going to decouple the 0V on the DCP from the rest of the board. I expect that it will drop the current draw of the board significantly.

 EDIT: On second thought, I may not do this See my comment in post 470


----------



## DKJones96

At 70ma of idle current the DCP020509 is only running at 32% load and is somewhere around 75% efficient giving you a total of 54.25ma. Still missing about 15 tho...

 How are you going to decouple the 0v?

 Has anyone gotten the Bantam/Carrie pair cased successfully? I don't know what the heck is going on with mine but on the table it's fine, I can pick it up, wiggle the two boards around, hit it to the table(frustration) and it stays playing fine. Once I stick it in the case moving or even touching the usb causes a pop sound from the earphones and music stops and windows doesn't see the bantam anymore. I've even held the bantam and moved the usb cable around with no issues.

 Damn thing just went to static when I was trying to change the volume.


----------



## nightanole

Im still building, i was planning on doing the dual 100uf fm caps on the vground and then my huge caps across the rails, like the mini3 does, should i also isolate the dcp zero volt pin?


----------



## cobaltmute

Quote:


  Originally Posted by *DKJones96* /img/forum/go_quote.gif 
_At 70ma of idle current the DCP020509 is only running at 32% load and is somewhere around 75% efficient giving you a total of 54.25ma. Still missing about 15 tho...

 How are you going to decouple the 0v?_

 

There are four traces around the ring that connect it to the ground plane. Either a knife or possibly a Dremel. I suspect the knife as the Dremel will not be fine enough.

*Big Warning* I just realized that the USB jack on the Bantam is grounded as well as the case will be from the Carrie. This mod may not work at all as the case might/will tie the two together anyways.

  Quote:


 Has anyone gotten the Bantam/Carrie pair cased successfully? I don't know what the heck is going on with mine but on the table it's fine, I can pick it up, wiggle the two boards around, hit it to the table(frustration) and it stays playing fine. Once I stick it in the case moving or even touching the usb causes a pop sound from the earphones and music stops and windows doesn't see the bantam anymore. I've even held the bantam and moved the usb cable around with no issues. 
 

Are you casing it with panels or just sliding it in? Sounds like you might be shorting something through the case.


----------



## cobaltmute

Quote:


  Originally Posted by *nightanole* /img/forum/go_quote.gif 
_Im still building, i was planning on doing the dual 100uf fm caps on the vground and then my huge caps across the rails, like the mini3 does, should i also isolate the dcp zero volt pin?_

 

Do not isolate the 0V pin at this time. If you note in post 470, I realized that once Carrie gets into the case, it likely won't make a difference.


----------



## Billyk

Quote:


 Has anyone gotten the Bantam/Carrie pair cased successfully? I don't know what the heck is going on with mine but on the table it's fine, I can pick it up, wiggle the two boards around, hit it to the table(frustration) and it stays playing fine. Once I stick it in the case moving or even touching the usb causes a pop sound from the earphones and music stops and windows doesn't see the bantam anymore. I've even held the bantam and moved the usb cable around with no issues. 
 

My 1st one is all cased up and running great. I do only have plastic end caps though. I am using it at the office between my PC and a chip amp been listening to it for several days now. Works flawlessly and sound very very good.
 I am waiting on a grubdac board for build #2.


----------



## DKJones96

Don't do it cobaltmute! The DCP is essentially a high speed step-up transformer with a built in rectifier. If you cut the traces to the output gnd it won't work at all. These units are designed to have complete isolation so the output hv has no path back to output gnd through input gnd.

 And I'm not using the end plates, they come in tomorrow. It's just in the case. I'll eventually get it figured out.


----------



## joneeboi

C8 underneath the Bantam can short to the case. It's happened to me before.

 I'll have to mull over the grounding circuit before I can give you a definite answer, cobalt.


----------



## DKJones96

Strangely enough, if I use a piece of paper underneath the boards it does this, but if I stick a piece of tape underneath it doesn't... tape it is I guess.


----------



## Billyk

I find that the plastic from those disposable containers from the market cut up and work well as an insulator. I have used it in my cmoys and anything in these little Hammonds.


----------



## keyid

Quote:


  Originally Posted by *DKJones96* /img/forum/go_quote.gif 
_Has anyone gotten the Bantam/Carrie pair cased successfully? I don't know what the heck is going on with mine but on the table it's fine, I can pick it up, wiggle the two boards around, hit it to the table(frustration) and it stays playing fine. Once I stick it in the case moving or even touching the usb causes a pop sound from the earphones and music stops and windows doesn't see the bantam anymore. I've even held the bantam and moved the usb cable around with no issues.

 Damn thing just went to static when I was trying to change the volume. 
	

	
	
		
		

		
		
	


	


_

 

My bantam/carrie is working great except for the 80mv spike when turning off the amp/computer. Ill be completing the grubdac by end of the week. I got the boards and 2707 just waiting for mouser.


----------



## cobaltmute

Quote:


  Originally Posted by *keyid* /img/forum/go_quote.gif 
_My bantam/carrie is working great except for the 80mv spike when turning off the amp/computer. Ill be completing the grubdac by end of the week. I got the boards and 2707 just waiting for mouser._

 

Cool that you got the boards. I was thinking people might start getting them tomorrow.

 There is no clearance issues with the Grub in the case. I slipped my combo into the case last nite and specifically looked at that.


----------



## Billyk

Quote:


  Originally Posted by *keyid* /img/forum/go_quote.gif 
_My bantam/carrie is working great except for the 80mv spike when turning off the amp/computer. Ill be completing the grubdac by end of the week. I got the boards and 2707 just waiting for mouser._

 

How do you set yourself up to see that? I want to check mine.


----------



## stwspoon

Quote:


  Originally Posted by *cobaltmute* /img/forum/go_quote.gif 
_I'm going to recant that last post.

 I metered that Carrie alone at pulling 70mA of idle current

 Let's do some math on that
 DCP020509 = 23mA
 AD8397 = 9mA/amp = 18mA
 OPA690 = 6mA
 TLE2426 = 150 microA
 TL750L08CLP = 1mA

 Total should ~= 51ma (23ma for the DCP + 25mA*1.15 for efficiency loss in the DCP for the on board components).

 Where is that other 20mA going?_

 

I'm not sure you accounted for the DCP input output voltage difference and efficiency at light loading.

 DCP power out = 25 ma * 9 v = 0.225W (~ 12% load for a 2W DCP)
 Efficiency at 12 % load via data sheet fig 5 is ~ 65% for DCP0212
 DCP power in = 0.225 W / 65% = 0.346 W
 DCP current in = 0.346 W/5V = 69.2 ma

 To check this, power down the DCP (ground the sync pin) to see what else is drawing current.


----------



## cobaltmute

And that is why I make sure my calculations are public, because I know I don't always get it right.


----------



## keyid

Quote:


  Originally Posted by *Billyk* /img/forum/go_quote.gif 
_ I want to check mine._

 

checked dc offset by connecting OG (output ground) to OR or OL with a meter and turning off the amp or unplugging the usb.


----------



## Billyk

Quote:


  Originally Posted by *keyid* /img/forum/go_quote.gif 
_checked dc offset by connecting OG (output ground) to OR or OL with a meter and turning off the amp or unplugging the usb._

 

Thanks, I knew that... Once you told me!


----------



## keyid

symptoms of a old timer 
	

	
	
		
		

		
		
	


	



 pls let me know if this is the case of your carrie


----------



## joneeboi

Quote:


  Originally Posted by *cobaltmute* /img/forum/go_quote.gif 
_*Big Warning* I just realized that the USB jack on the Bantam is grounded as well as the case will be from the Carrie. This mod may not work at all as the case might/will tie the two together anyways._

 

There's also the issue of connecting signal ground because it is still connected to USB ground. But like, stwspoon mentioned, all the currents are accounted for anyway. 
	

	
	
		
		

		
		
	


	




 I'll get a chance to make some measurements soon, so I'll report my results back when I get that chance. I've been super busy with school and extra curriculars, but I'm keeping up with the thread and all the issues you guys bring up. I really want to scope the rails. I'll try and formalize my test method and results for the thread when I get that chance.

 DK, did you check if C8 was the one shorting to the case? If it isn't that one, it could be L3.


----------



## cobaltmute

I did a test last nite with my second Carrie board. Using a USB pigtail I bought to make a cable DAC, I powered the Carrie directly off the USB (without the DAC being in line). The Carrie powered up fine, with no shutdown of the USB port.

 My Carrie + Grub when first plugged in to the computer (a Thinkpad X61), has Windows 7 shut down the port. If I disable/enable the port in Windows, the pair will run fine. Plugging the same combo into a Dell laptop works fine. It should be noted that on my Thinkpad, power is always delivered to the port and only the data interaction with the DAC is shutdown. After re-enabling the port, if I look through device manager, the PCM2707 is reporting its power requirements as 20mA.

 This leads me to believe the issue is not the actual power draw of the combo, but the way that the GrubDAC is reporting its power needs to the PC. stwspoon deserves credit for bringing this up in the GrubDAC thread. Depending upon the hardware/driver, some machines may decide to "shut" the port down.

 The workaround at this point is to lift PSEL (pin 16) on the PCM2707 and air-wire it to power (3.3V). Pins 2/3 (Vccp and HOST) are likely a good choice as they are both tied to Vdd and gives you two pins to work with for easier soldering. This has the GrubDAC report to the host that it is bus powered and will be using 500mA.

 With PCM2706/07s in short supply, I'm stuck waiting on testing this. My current Grub board has been mutilated a bit with some bad soldering so I don't dare take it apart from the Carrie to work on it.

 EDIT: I should add that I'm going to try another workaround as well. I'm going to place a thermistor between the Grub and the Carrie and see if using it as a Inrush current limiter will work.

 EDIT: *Revised info here http://www.head-fi.org/forums/f6/car...ml#post6075302*


----------



## nightanole

Does the input/output/volume control need to be isolated from chassis? Im using an all metal case and panel mount jacks.


----------



## joneeboi

Only the output ground needs to be isolated. Input ground, volume pot, USB ground can all be safely connected to the case. Then again, I'm not sure what exactly is going on with your gamma-2+Carrie build, so you have to the ultimate judge of that.


----------



## joneeboi

Quote:


  Originally Posted by *cobaltmute* /img/forum/go_quote.gif 
_My Carrie + Grub when first plugged in to the computer (a Thinkpad X61), has Windows 7 shut down the port._

 

My Toshiba on Vista and 7 don't work with the Bantam. It was great on XP, but it isn't working for me with the new ones. It works for others on 7, but my computer seems really temperamental. I've gone through every "solution" on Google, so if anyone can offer me another idea, I'm game.


----------



## Billyk

Quote:


  Originally Posted by *keyid* /img/forum/go_quote.gif 
_symptoms of a old timer 
	

	
	
		
		

		
		
	


	



 pls let me know if this is the case of your carrie_

 

Very interesting... FWIW
 Carrie offset when I turned off using the power switch on the pot was about -25 on average. Unplugging USB seemed to result in just a tad less.
 Mini^3 with the inputs shorted or not averaged about -110


----------



## cobaltmute

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_My Toshiba on Vista and 7 don't work with the Bantam. It was great on XP, but it isn't working for me with the new ones. It works for others on 7, but my computer seems really temperamental. I've gone through every "solution" on Google, so if anyone can offer me another idea, I'm game._

 

So it doesn't recognize it or it shuts down the port? What do you see in Device Manager under USB controllers when your plug in?


----------



## nightanole

Im just gonna throw this out there. The gamma 1 has beads on both the 5v+ and the ground of the usb port to isolate them from chassis. This would be REAL easy to impliment in the carrie. Im goning to be tapping power/ground after the beads on my gamma 2 so i should be good. If all goes well i shouldnt need to implement a 5v external power supply. So far i havent heard anyone complaining about noise from using just usb.


----------



## cobaltmute

On the Carrie, biggest source of noise will be from the DCP, not the USB power. And post the DCP there is the low-pass filter created be C1F, L1F, C2F. 

 The ferrites in the Gamma1 do the same thing (and the always need to be followed by a cap to make it work).


----------



## daBigR--

Hi, I received the mouser parts late last week and assembled both Carrie boards during the weekend. So far I've only connected one of them to a DMS1, and I was getting a loud hum that I later found was caused by an interconnect I left pugged to the mp3 player output with the other end unconnected, duh! So getting rid of the cable got rid of the noise, but I still have a high frequency hiss, barely noticeable at normal listening levels but stil present, I'll do some testing while setting up the 2nd amp to try and solve that noise issue. Regardless of that, the amp sounds really good, I've been doing my listening on HD-595s mostly to classical music and some jazz. The most noticeable thing is the imaging, IMO better than the PIMETA and I think even better than my Ear+ HD, every intrument is placed on a very defined place in space. It also has a lot of detail and a very likeable bass, quite to my taste, very controlled and good transient response too. As for the USB problems, not an issue for me since I'm powering directly from the mp3 player's regulated power source, not from it's USB out ports, but I'll try and measure inrush current at switch on/off to compare with your figures. I don't know if any part of my post will be of any help during this prototype stage as I'm not a very experienced DIYer, please let me know how I can help further.


----------



## joneeboi

Quote:


  Originally Posted by *cobaltmute* /img/forum/go_quote.gif 
_So it doesn't recognize it or it shuts down the port? What do you see in Device Manager under USB controllers when your plug in?_

 

Sorry for the lack of clarity. It turns on, plays music, shows up in Device Manager and everything, but every once in a while (I can't seem to pinpoint when), the sound just turns to static for a few minutes and then goes back to normal. I think it might have something to do with ReadyBoost, but I still have to test that. It seems when I get really active on the computer, it goes to static. Using the computer solely for music reduces(/eliminates?) the frequency of these occurrences. Everything seems to work fine but the PCM.

 Thanks for sharing your measurements, BillyK. That's really interesting stuff.

 nightanole, are you suggesting having two filters in series? If it's already on the gamma, then why do you need one for Carrie? This filter also exists on the Bantam.


----------



## joneeboi

Quote:


  Originally Posted by *daBigR--* /img/forum/go_quote.gif 
_Hi, I received the mouser parts late last week and assembled both Carrie boards during the weekend. So far I've only connected one of them to a DMS1, and I was getting a loud hum that I later found was caused by an interconnect I left pugged to the mp3 player output with the other end unconnected, duh! So getting rid of the cable got rid of the noise, but I still have a high frequency hiss, barely noticeable at normal listening levels but stil present, I'll do some testing while setting up the 2nd amp to try and solve that noise issue._

 

What kind of gain do you have on your amp? Sometimes too high of a gain can amplify noise. Gain two is sufficient for me.


----------



## daBigR--

I used the BOM you posted on Mouser, only changed the 100pF ceramics for .1 uF ones, all the rest is by your specs so it is a gain 2 amp and that's more than plenty for the 50 ohm HD595s. As I said the noise is barely noticeable if at all at normal listening volume, but you can definitelly hear it if you mute the sound and turn the volume pot almost all the way up. I'm thinking some of the air wiring I did inside the mp3 player's case may be picking some noise, that's why I'll do more testing while connecting the second board listening before casing it and maybe trying different placements inside the case.


----------



## stwspoon

Another quick test is to ground the sync pin on the DCP (pin 14 to pin 2) and run the Carrie off of a 9V battery to see if the DCP is causing the noise.


----------



## cobaltmute

My Carrie + Grub is dead silent max volume no music.


----------



## stwspoon

Warning: Do not connect PSEL to +5V! VBUS and HOST are the only pins on the PCM270x that can go to 5V. You will eventually kill the chip. Check the data sheet. This include D+, which can only be pulled up to 3.3V and only when VBUS is at high.

  Quote:


  Originally Posted by *cobaltmute* /img/forum/go_quote.gif 
_I did a test last nite with my second Carrie board. Using a USB pigtail I bought to make a cable DAC, I powered the Carrie directly off the USB (without the DAC being in line). The Carrie powered up fine, with no shutdown of the USB port.

 My Carrie + Grub when first plugged in to the computer (a Thinkpad X61), has Windows 7 shut down the port. If I disable/enable the port in Windows, the pair will run fine. Plugging the same combo into a Dell laptop works fine. It should be noted that on my Thinkpad, power is always delivered to the port and only the data interaction with the DAC is shutdown. After re-enabling the port, if I look through device manager, the PCM2707 is reporting its power requirements as 20mA.

 This leads me to believe the issue is not the actual power draw of the combo, but the way that the GrubDAC is reporting its power needs to the PC. stwspoon deserves credit for bringing this up in the GrubDAC thread. Depending upon the hardware/driver, some machines may decide to "shut" the port down.

 The workaround at this point is to lift PSEL (pin 16) on the PCM2707 and air-wire it to power (either 5V or 3.3V). Pins 2/3 (Vccp and HOST) are likely a good choice as they are both tied to Vdd and gives you two pins to work with for easier soldering. This has the GrubDAC report to the host that it is bus powered and will be using 500mA.

 With PCM2706/07s in short supply, I'm stuck waiting on testing this. My current Grub board has been mutilated a bit with some bad soldering so I don't dare take it apart from the Carrie to work on it.

 EDIT: I should add that I'm going to try another workaround as well. I'm going to place a thermistor between the Grub and the Carrie and see if using it as a Inrush current limiter will work._


----------



## cobaltmute

Vccp and HOST are provided 3.3V in my setup, so they are still good to connect to.

 My mistake about 5V tolerance of the PSEL pin.


----------



## keyid

The carrie sounds really great with the grub dac, you guys need to try this grub dac. Havent heard the mini3 sound this good.


----------



## daBigR--

I rerouted some of the cabling connecting the power supply and in/out signal for the Carrie and now as cobaltmute said the amp is dead quiet, thanks for the ideas.

 As for the problem some of you are having regarding the OS disabling the USB port when you plugin/switch on the amp. I found some documentation (click the USB 2.0 Specification link, and then open usb_20.pdf inside the zip) you may be aware of but I just wanted to point out that on section 7.2.1.4 and 7.2.4.1 there are some indications regarding high power and inrush current issues.

 Following that lead I found this application report for TPS2150/51 current limiting switches. Given my basic electronics knowledge I think I understand what they're discussing but can't really follow all the details. Anyway I think it may be applicable to the Bantam/Grub/Carrie setup and some of you may be able to investigate further.


----------



## nightanole

Well i got my ubber HZ caps in. Im not sure where to put them. They both fit in the cap bank if placed on their sides. However i wanted to turn this back into a mini 3. The mini 3 has no capacitance before the regulator, the carrie has all of its rail-rail capacitance before the regulator, so any rush current needs to go thru the regulator first. 

 I think what i will do is run 1 HZ across the rails, and install the 2 mini3 pan fm 100uf stock caps in the stock locations from ground to rail. I may just run the HZ in the C6 place since cobalt is running fine without neither c6 nor c3.

 Im slightly curious what CF1 and CF2 actually do since they are before the regulator, on either side of a coil, and pretty big in capacitance. They cant be for filtering nor stability.


----------



## cobaltmute

Quote:


  Originally Posted by *nightanole* /img/forum/go_quote.gif 
_Im slightly curious what CF1 and CF2 actually do since they are before the regulator, on either side of a coil, and pretty big in capacitance. They cant be for filtering nor stability._

 

Pi-filter or LC filter (post filter for the DCP noise). Low pass filter with a 653Hz corner.


----------



## nightanole

][/url]


----------



## cobaltmute

Compared to the 10V caps on my board, all those caps look huge


----------



## nightanole

ya the stock bom 220uf caps dont fit a standard case without a lot of shoe horning. Im gonna have to lay them on their side.


----------



## joneeboi

Yes, CF1 and CF2 are for filtering, hence the "F."

 Thanks for the picture, nightanole. That's really helpful for figuring out the perspective and relative sizes. I'll have a bit of time this weekend, so I think I'll overhaul the power supply altogether. It's not just a layout thing; I have to rethink the whole integration of Carrie with both the Bantam and Grub. I'll make my order for the Grub parts soon enough (it's so inexpensive!), so that'll help with the whole design.

 For those wondering about a timeline for the next Carrie revision, I can't make any promises. I am gonna try and sneak into a lab this week to take some measurements, but I haven't really had a chance to work on it in a long time. I apologize for the really slow development, but I...have a lot on my plate. This is definitely the toughest semester I'm going to take in my life, so I'm still trying to stay afloat let alone exceed expectations. I haven't lost interest in this project, I'm just trying to balance my life. I'll give it some much-needed attention this weekend.


----------



## cobaltmute

Carrie + GrubDAC #2 built with full capacitor working and no USB port shutdown 
	

	
	
		
		

		
		
	


	




 There is a revised workaround to the shutdown of the port issue. Pin 16, PSEL needs to be pulled high to tell the USB controller that it is bus-powered. It do this you need to get power to that pin. Well, it just so happens that ping 15, DT is pulled high through a 1.5K resistor. DT is normally used on a PCM2706 for communications with an EEPROM. What you can do is lift PSEL and bridge it to DT. Way easier that trying to have to solder a wire to PSEL. Just make sure that when bridging it that you have accidentally connect the pad under PSEL. As noted this will be changed in the next revision of the Grub.


 Edit: Maybe I spoke too soon. Now it won't plug in without shutdown 
	

	
	
		
		

		
		
	


	




 Trying to figure out what happened there.


----------



## cobaltmute

I hate this kind of issue.

 I have three mini-USB cables on my desk.

 Cable 1: from a WD Passport harddrive
 Cable 2: from an old iRiver player
 Cable 3: some generic.

 Cable 1 and 3 shutdown the port every single insertion. Cable 2, the iRiver one, works every single time. The only difference I can see is that the iRiver one has ferrites at both ends.

 ARGH!!!!

 As a further note, this Carrie is setup with close to the BOM I posted earlier. C12-17 were removed and replaced with 2x680µF Panasonic FM caps from rail to rail. So same capacitance, just better utilized.


----------



## ShinyFalcon

An iRiver cable I have wasn't able to completely power up my laptop hard drive unless I shake it a bit to get the spinning started. I'm thinking something is restricting current or voltage, maybe the ferrite, but it's strange...


----------



## nightanole

Has anyone tryed the standard 3 wire cables that come with portable usb hard drives? Ya know 2 A ends and 1 mini end, for the units that require more then 100-500ma inrush current to get the drives spinning. In other news i got my cheap stepped ebay special so i should have my carrie/gamma2 combo working this week. 

 I still dont get my voltages but i checked with 2 multi meters. unpluged my usb power is 5.1v, plug in the gamma2 and it drops to like 4.5. 4.75tp and 3.3tp on the gamma show 4.3 and 3. But its working.... And ive tested it with 2 multi meters that cost over $200 each... but dont regulators put out nothing if they dont have the min .2v in over regulation voltage???


----------



## cobaltmute

The regulators drop-out ie. they don't regulate any more but they still pass current. It's always are very real issue for the 4.75 reg as USB power can drop that low per spec. The fact that your USB drops to 4.5v means that your port is not USB compliant as USB power is supposed to be 4.75-5.25. It is also ever weird that the 3.3 reg drops to 3V. It still has plenty of room before it should be in dropout.


----------



## cobaltmute

Quote:


  Originally Posted by *ShinyFalcon* /img/forum/go_quote.gif 
_An iRiver cable I have wasn't able to completely power up my laptop hard drive unless I shake it a bit to get the spinning started. I'm thinking something is restricting current or voltage, maybe the ferrite, but it's strange..._

 

I tried putting a inrush limiter on as a test and it was too big and didn't let the DCP start.

 It is likely something to do with the chipset in my Thinkpad. I was reading some info on USB power switches and some do all more current to be drawn for a short period before they tell the host something is wrong. I need to see how much of an issue it is for people before I really starting looking at possible items to help fix the issue on the Grub.


----------



## joneeboi

Here's v1.25. Changes include:

 - Two enormous capacitors. Yep, they fit. I had to create a custom package for these, and they are meant to lay flat on the board. Maybe I can put some fine artwork under them. Think we should keep both?

 - Drastically reduced size of other capacitors. I/O caps for the DCP, filter caps and TLE caps are all smaller. You may not notice as much with the TLE ones, but I had to create a custom package to reduce them from 7mm diameter to 6.3mm which is the spec'd size in the datasheet.

 - Added a resistor to prevent DCP overvoltage, ROV. If you set its value to draw about 30% load from the DCP, you won't get an overvoltage when the switch is open. Is this a meaningful use of space? The caps are the only ones that see this overvoltage, so cutting into the power reserve of the chip would limit the amount that can be used by the amplifier section. What do you think?

 - Relocated the signal input holes. The (mislabeled) ground input has been relocated underneath C12. I liked how the first prototype fit together with the Bantam when the ground were connected right next to each other. cobalt and I are trying to find a place to put a second set of holes for an even tighter fit between the Carrie and Grub.







 Note: This version is neither the next prototype nor the production. It is merely a progress report.


----------



## cobaltmute

How about some pads under C11 and C12 for upright caps? Run the V+ trace up the center and you could put maybe 4x 8mm or 10mm caps. It would be a nice option for those that don't want to lay their caps down.

 For placing a load on the DCP, instead of ROV, why not put an LED then ROV (with ROV as a surface mount underneath the DCP). That gives a power to the board indicator. 

 As for integration with Grub, I'm about to start my 4 layout of the next version.


----------



## cobaltmute

And for the over-voltage, why not put the power inputs right next to IL/IR, and "flip-flop" the DCP with the other power elements so that you can switch the input voltage, not the output voltage of the DAC. Then you don't have to worry about the over-voltage issue at all.


----------



## nullstring

Quote:


  Originally Posted by *cobaltmute* /img/forum/go_quote.gif 
_As for integration with Grub, I'm about to start my 4 layout of the next version. 
	

	
	
		
		

		
		
	


	


_

 

*cough* SPDIF *cough* =)
 though, I suppose I seem to be the only one who wants it =(


----------



## cobaltmute

Quote:


  Originally Posted by *nullstring* /img/forum/go_quote.gif 
_*cough* SPDIF *cough* =)
 though, I suppose I seem to be the only one who wants it =(_

 

Dude, I haven't forgotten. The next version of the board will deal with some layout issues and the PSEL pin. This is sort of a "correction" release. After that will come your SPDIF. I'm working on that as well right now as well in the schematic portion.


----------



## nullstring

sorry. just giving a friendly reminder.


----------



## nightanole

Uh your putting 2 HZ 1800uf caps, in parallel? And no stability caps for the ground channel? That doesnt sound right.

 "Capacitors C5+ and C5- provide filtering and decoupling, reducing noise and enhancing rail-splitter stability. "

 Yours doesnt have this with this version. I would stick to the orginal mini3 as much as possible other then the power supply. Thanks to the 1 watt limit of the DCP theres no point in putting in ambs stock 1amp 12v regulator, so i think the one you picked is fine (really isnt it double what the dcp can put out?) But 3600uf of reserve power compared to the stock 940uf, and then no stability control for the ground channel doesnt sound good. 

 With just 1 HZ 1800uf you have double the reserve of the mini3, and more then triple the instantaneous current. Id use the other space for rail to ground caps.


----------



## joneeboi

C9 and C10 go from rail to ground. I probably should have added a schematic. There's room for 180uF each, basically the taller, higher voltage versions of what the Mini^3 specs.

 I'm thinking of switching the stock DC/DC converter to the 9V version as in cobalt's implementation. With the 2W power capability, that takes the load off the capacitors to supply the power though I'll be sure to add enough capacitance to keep it running. The E-Pad version of the AD8397 can put out 2W at room temperatures, so maybe a smaller amount of capacitance is all we need. Maybe I should try connecting the EPAD to the ground too in the name of protecting the circuitry from the power supply. I'll add the pads for other capacitors while I'm at it. I think a lot of the hair splitting will go away with choosing the higher power DCP020509.


----------



## cobaltmute

C3 and C6 are also rail to ground, aren't they? They aren't even on the Mini^3 schematic (which is why I skipped them).


----------



## nightanole

Uh at 8v the theo max of a perfect circuit of 32 ohms ohms is 250mw into each channel. So your 1 watt DCP is double what you need without the bank.

 Now lets say you have normal cans, say 80 ohms, thats only 100mw into each channel, and in that case your dcp is 4x over rated.

 Now this is the hottest digital signal, sent thru a dac and then gained to match 8vpp and the volume completely cranked.

 That dcp has all the power it needs, and the bank is fast enough to supply any rush current the opamps need. If your bebopin along and then that 10db hot cannon burst comes on, its still only gonna suck half the power of the dcp, not including the cap bank, if the volume was completely cranked beforehand.


 Im not sure why everyone is hell bent on a 2 watt source when the mini3 doesnt even have a half watt source with its 9v (unless you find one of the few rechargeables that can put out over 300ma without drooping 2v). The only reason the mini3 has a 1 amp 12v regulator (ps thats 560mw into grados) is so it can dissipate the heat from the morons that hook a 30vdc unregulated wallwart into it.



 Ps i know the opamp cant put out rail to rail, i rounded for quick numbers since we are working in magnitudes almost.


----------



## cobaltmute

The DCP0105xx is available in 5, 7, 12, 15v models
 The DCP0205xx is available in 5, 7, 9, 15v models.

 You notice if you want a 9v output, you have to go to the 2W DCP.

 What's so good about the 9v DCP? You can use 10V caps. When you want to only put a couple of caps on the board, this is a very good thing. If you compare 6.3mmx11.5mmx2.5mmLS Panasonic FMs, at 10V you get 220uF and at 16V you get 120uF. So if you're running 10V you can use 1 cap, and at 16V you need 2 for the same capacitance.

 So it is not just about output power, but overall board design.


----------



## cobaltmute

But on the other side of that comment, I think it is the combination of the 2W 9V DCP and the 8V reg that may be causing my issue since no one else is having and issue with USB port shutdown. The minimum input power on the TL750L08CLP is 9v so it is running very near its limits.


----------



## nightanole

I was talking about voltages after the regulator, aka 8v 10v 12v, not the dcp voltage.

 PS: can both opamps and the v divider work at 15v, or was 12v the limit of the 690? That might be nice for some 250ohm cans, and at that voltage and ohm rating you wouldnt need much capacitance.


 Update: woohoo i found an old cellphone charger that has a 1amp 5v powersupply wall wart, that you can take apart, and its got a regulator in it. Its only a 1 diode rectifier though...


----------



## joneeboi

I've read that one need only 10mW into your headphones for more than enough loudness. I don't listen to my music very loud, but I'm trying to keep the design consistent with itself. If the Carrie is putting out its maximum power, I want the opamps and/or headphones to be the ones that blow up, not the power supply.

 cobalt, weren't you saying that only your Dell was acting up when you plugged in the Carrie/Grub and that your other laptop worked fine? Have you tried it on desktops?

 edit: Hm, does that make sense? Should I protect the circuitry from itself? Should I underspec the power supply instead to protect the opamps and load?


----------



## cobaltmute

Other way around. Thinkpad dies, but the Dell runs fine. Haven't tried it on desktops yet.

 I'll try it on some and see what I can determine. I can take it work, but the problem is that we are a consistent HP shop there (very uniform hardware).

 keyid reported his Grub working, not sure if it was with a Carrie or not.


----------



## cobaltmute

Ok:

 Dell laptop, docking station and USB card in docking station - all good
 Old P4 - good
 Thinkpad X60 (with XP) - reports power surge on the port, but enables.

 As I've got a X61 (with Win7) - I suspect it is the same hardware as the X60. But Win7 shuts the port down, while XP might keep it up.

 Hmm.... wonder if there is a registry setting anywhere to fix this.

 And I have verified in device manager that the PCM2707 is reporting full power use (500mA). On the one that I haven't lifted and powered PSEL, it is reporting only 20mA of power required.


----------



## cobaltmute

Has anyone else actually checked the initial draw of their Carrie?

 Skipping the Bench supply I did this:

 Using USB pigtail (destined for a cable dac), I connected Gnd to the Carrie with a test lead. I placed my meter on current measuring setting between the USB V+ and the Carrie V+. Set my meter for peak hold to show peak draw and plugged in the USB cable. I repeatedly got a 750ma draw shown as peak.

 I'd be curious what this test would show for those running the DCP01.


----------



## nightanole

Quote:


  Originally Posted by *cobaltmute* /img/forum/go_quote.gif 
_Ok:



 And I have verified in device manager that the PCM2707 is reporting full power use (500mA). On the one that I haven't lifted and powered PSEL, it is reporting only 20mA of power required._

 

How do i do this? I tryed looking into device manager and all i could find was that the device was in D0 which means its on and not asleep.

 "joneeboi"

 I cant speak for headphone amps. But most huge amps that have linear power supplies, match the supply to the amp or less. They dont make the power supply 2x-8x more powerful then what the amp can draw at full tilt, its a waste of money and real estate. a 2000watt peak amp might only have a 1000watt ps because they know that its not gona run out of reserve any time soon because even the most dynamic booms are only 10db hot and last for less then a sec. So if your listening at 10mw and that 10db canon hits your going up to 100mw, but the supply might only be 50mw, and wont heat up or run out of gas before the music tones down and it recharges.
 you want the amps to be overkill compared to the speaker. Its not uncommon to have 1000watt subs playing with 2000watt amps, because its the distortion of the amp that going to blow the sub, not the wattage. 

 The worst thing you could do is have a 1000 watt supply, a 500 watt amp, and a 1000watt sub. The supply is more then enough to blow the amp, instead of folding over and reducing voltage. The sub has more then enough load to over power the amp, causing the amp to distort, and odds are killing both the amp and the sub. The best combo would be a 500watt supply, a 1000watt amp, and a 500watt sub. Then the supply will give out before the amp starts to distort or over power the sub.


----------



## cobaltmute

To find out what the device is reporting for power requirments you need to check the USB root hub it is plugged into. There is a tab for power and it says it there


----------



## nightanole

gamma 1 shows up as a 20ma device


----------



## cobaltmute

Gamma1 reports as self powered so it will ony report the usage of the pcm2707.


----------



## nightanole

Hey boss those 220uf 35v caps dont fit in my alternate case i picked. Can i use lower capacitance or lower voltage since im not using a switch, or do i have to lay them on their sides?


----------



## joneeboi

You can use lower voltage caps if you're not using the switched pot. Capacitance and instantaneous power is what we're discussing here, so I can't really give a firm answer. I guess the best starting point is 940uF as in the Mini^3.

 I think I'll remove the second giant cap and put pads for upright rail-to-rail capacitors. Like nightanole discovered, the best performance is with that 10mm x 25mm giant cap, but maybe people will prefer paralleling caps.

 Hm, maybe I should just stick with the 1W 12V. I really don't get why people need such high gain. My 650s play fine on my Carrie. 
	

	
	
		
		

		
			





 If I move the switch to the input of the DCP, then we wouldn't have this overvoltage problem. With the lower voltage, we can fit more capacitance into the same space. I think the filter caps may need to be higher spec'd anyways since they're placed before the regulator. I'm gonna switch the BOM filter caps to be 0.1uF 50V ceramics. As I mentioned before, there's no need to have such a low corner frequency for this filter. The DCP oscillates at a really high frequency, so raising the corner frequency will greatly reduce the space taken up by the filter. That means people will be able to use 16V caps with higher capacitance density.

 Hm, off to the bat cave --err, workshop for me.


----------



## nightanole

The grub with a gain of 2 would make it put out 11v, however the bantam would only make it swing 6v.


----------



## nightanole

Well i got mine semi working. Dont have the volume pot nor output connected, but it does suck 100ma from my power supply. I made it using the 12v regulator.


----------



## cobaltmute

Quote:


  Originally Posted by *nightanole* /img/forum/go_quote.gif 
_Has anyone tryed the standard 3 wire cables that come with portable usb hard drives?_

 

Just tried on that came with a 2.5" SATA drive enclosure. Powered up my combo with no issues.


----------



## nightanole

Ya know id be willing to spend an extra couple of bucks on the board if it meant thicker sturdier traces. I hope everyone likes there gain, cuz i havent been able to remove 1 part without losing part of a pad, and thats with some pretty pricey rework equipment. The stuff is just too thin, its like working with a radioshack protoboard. If i have to adjust the gain im just going to dyke off the resistors, its not worth the risk. Ive allready lost connection to the center plain moving the 220uf caps, lucky its real easy to rewire those points.


----------



## cobaltmute

I'd have to say the same thing. I don't know if is that GoldPhoenix is getting cheap material, but I reworked both my Carrie boards and lost one side of a through-hold pad a couple of times (and the second board I was being careful about this). I ended up mounting some of my resistors on the bottom of the board to make it work.

 Decent craftmanship on the board, but cheap PCB stock? It is like the copper is not sticking to the laminate well.


----------



## Juaquin

So I got a few minutes in lab today to hook up my Carrie with a stock build to a scope. I supplied 5V from a lab supply (not USB) so I don't know how indicative this is of an actual usage scenario, but I measured the ripple out of the DCP to be roughly 40mV. Of course, this was with the amp unloaded (I forgot my cheap "test" earbuds). I'll see if I can get some more time next week to take better measurements.

 Also, this is obvious, but there is a lot of capacitance on this board. Don't forget that when you're hooking up test leads and prodding around on the board, unless you want to make the people next to you jump.


----------



## joneeboi

For the next board run, I'll be going with Imagineering Inc. Think amb, tooleAudio...

 These next two weeks are lock down for me on account of the midterms and labs crunch, so I'll be in a bit of time crunch. I settled on a pretty solid revision, but I want to sit on it for a little bit to squeeze out the weaknesses in the power supply.

 Juaquin, was that ripple on the rail or right out of the DCP? That seems frighteningly high after the filter.

 edit: [redacted]


----------



## mugdecoffee

Quote:


  Originally Posted by *nightanole* /img/forum/go_quote.gif 
_Ya know id be willing to spend an extra couple of bucks on the board if it meant thicker sturdier traces. I hope everyone likes there gain, cuz i havent been able to remove 1 part without losing part of a pad, and thats with some pretty pricey rework equipment. The stuff is just too thin, its like working with a radioshack protoboard. If i have to adjust the gain im just going to dyke off the resistors, its not worth the risk. Ive allready lost connection to the center plain moving the 220uf caps, lucky its real easy to rewire those points._

 

If you really want to turn down the gain, you could parallel a second resistor on top of the first which wouldn't require any pad lifting. Also it would be pretty easy to remove the top resistor afterward too if you wanted to change it again. The only downside is that you can only decrease resistance but by choosing the right resistor to parallel it shouldn't matter.


----------



## cobaltmute

If you look at amb's Mini^3 parts list, he changes r1, r3, and r4 to reduce the gain. this is apparently for stability.


----------



## Juaquin

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_Juaquin, was that ripple on the rail or right out of the DCP? That seems frighteningly high after the filter._

 

Pre-filter, right off the DCP pins. And like I said, the amp was unloaded. Next lab I'm going to load it and try testing the ripple on the +/- split supplies, since that's the important part.


----------



## cobaltmute

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_edit: The quote I got from Imagineering was $375 for 50 boards. That works out to $7.50 per board, plus a bit for shipping. I didn't want to do this at first, but I'll set up another prototyping stage for the new power supply. I guess the limit is 50 boards, so I'll try get that ordered up at the end of the month or beginning of the next month. I shudder at the thought of an even larger prototyping group, so bear with me as I try and move this along._

 

It'll be worth it. I just burned another pad trying to turn around a LED I put in backwards.

 Speaking of LED, my two units are done.









 The pictures make the lettering look bigger than it is. I made it a little too small, but it still looks good.


----------



## stwspoon

Verrrry Niiiice
	

	
	
		
		

		
		
	


	




 The Mini B USB connector is much better than the the full size B. Good call.

 Did you work out the USB plugin issues you were having a while back?


----------



## cobaltmute

Quote:


  Originally Posted by *stwspoon* /img/forum/go_quote.gif 
_Did you work out the USB plugin issues you were having a while back?_

 

It appears to be a touchy power management chip on my Thinkpad. I tried the setup on several machines with no issues (with PSEL at bus-powered). On a X60 with XP, Windows says there is a power surge but enables. My X61 with Win 7 (so basically the same underlying hardware) barfs. So it s a driver/hardware issue for me. However using a USB cable from an old iRiver works.


----------



## cobaltmute

For those of you that ordered FPE panels without infill, but still want white, a ghetto way to get infill it is to use a white crayon. Rub the crayon across the lettering and it will fill the letters in. Use a circular motion to ensure you get crayon in all the cracks then use your thumb to rub away the excess.


----------



## joneeboi

I haven't been getting my email notifications from head-fi lately, but those are some sweet panels on your Carrie, cobalt. Very professional. I like them.


----------



## nightanole

Well i got mine up and running without a case. Im taping the vbus from the gamma1. I cant tap it after the power switcher because it goes down to 3v for some reason (i thought it was rated for over 1.5amp). Between the gamma 2 and the carrie they suck 350ma from the usb port.


----------



## cobaltmute

Quote:


  Originally Posted by *nightanole* /img/forum/go_quote.gif 
_Well i got mine up and running without a case. Im taping the vbus from the gamma1. I cant tap it after the power switcher because it goes down to 3v for some reason (i thought it was rated for over 1.5amp). Between the gamma 2 and the carrie they suck 350ma from the usb port._

 

R16D of the gamma1 is a current limiter resistor for the power switch (pg 17 of the datasheet for the TPS2115APW). It limits to .333A right now. You may want to drop that to 1K for your build.


----------



## nightanole

Hmmm... All i have left are 620 and 1.2k. That would give me 806ma and 416ma.


----------



## nightanole

Ok 2 things:

 1. cobalt is a god among men. I replaced the 1.5k with a 680 ohm and i can now use the gamma1's on board power switcher so i can use either usb power or external power.

 2. We could implement TPS2115APW into the carrie and a current limiter. In my experiments the TPS2115APW limits the inrush current to what ever you set it to. Im my case with the 1.5k it limited it to 330ma, with the 680ohm it limited it to 850ma. What we could do it impliment it with a 1k resistor to limit the inrush current to no more then 500ma. the on on switch would be connected to D1, and 5vin. flip the switch and d1 goes high and the switch kicks and sends 500ma 5v into the dcp and the caps charge more slowly.

 PS: if the dcp only gets like 4v it sucks the line dry and pulls 500ma solid till the voltage kicks to 5v then it drops back down to normal levels. Also my carrie gamma2 lite combo sucks only 250ma at idle so im happy (the 350ma number from before was the dcp trying to kick on but couldnt).


----------



## nightanole

Pics are up at the builds image thread...


----------



## cobaltmute

Quote:


  Originally Posted by *nightanole* /img/forum/go_quote.gif 
_Ok 2 things:

 1. cobalt is a god among men. I replaced the 1.5k with a 680 ohm and i can now use the gamma1's on board power switcher so i can use either usb power or external power._

 

Definitely not a god among men. 
	

	
	
		
		

		
			





 Just a very fast learner/reader.


----------



## AKfour seven

I stand here today humbled by the task before dofus kamas, grateful for the trust you have bestowed, mindful of the sacrifices borne by our cheap dofus kamas. I thank President dofus power leveling for his service to buy dofus kamas, as well as the generosity and cooperation he has shown throughout this transition.


----------



## cobaltmute

Oh, random note that I just remembered - it might be an idea to but a cathode or anode mark for the LED on the board (easier build)


----------



## joneeboi

Hey sports fans,

 So I have a little bit of bad news. This is a general announcement that goes out to everyone following the project, prototypers and general followers alike.

 I had my laptop stolen from my locker this morning, and all my work was based out of that laptop. I've submitted a police report already, but there isn't any guarantee of me getting it back. There are no security cameras around my locker to report anything between the three hours I left it in there, so all I can do is hope and pray that the person would return my laptop. Until then, I have to postpone this project indefinitely. I know it's been on my backburner all month, but I really wanted to get it going around this time. However, I have bigger concerns at the moment.

 I apologize to everyone who was hoping to get their hands on the Carrie amp. This sort of thing could have been avoided if I had backed up my data, but it's a lesson I learned too late. Luckily, I protected my laptop with a password, so there's nothing anyone can do with it unless they reinstalled an OS or were particularly clever, which I'm hoping is not the case. I already blocked my Visa, and I'm working on changing all my passwords and debit card as well (as I saved all my passwords in both Firefox and Chrome). If anything turns up, I will let you know.

 If anything is to be learned from this incident, it's that safe and definitely better than sorry, and with all the strides that are being made towards cloud syncing and those already made with regards to safeguarding data, one would be wise to ensure that important documents could be accessed through two or three independent portals instead of just the one. I should know better what with my two accounts at Dropbox - Home - Secure backup, sync and sharing made easy., but I will definitely be more careful in the future. Take the moment to sign up with them or any of the other cloud services freely available these days, and maybe others will benefit from my experience.


----------



## cobaltmute

That blows huge freaking chunks.

 Get on changing your passwords and notifying people asap - just cause you have a password doesn't mean you can't get through it. I won't post the tool here, but it's pretty easy to get admin access to a WinXP box (haven't tried Vista or 7 yet).

 I know it is early to ask, but do you plan to rebuild? Worst case, I could knock something out similar to the last prototype if needed.


----------



## joneeboi

I have Windows 7 installed on that laptop, but I got all my important passwords changed already anyway. I think I have my bases covered, but if anyone else has suggestions, I'll gladly take them.


----------



## Juaquin

Big fan of Dropbox myself. Besides just backing up, it's great for syncing between my laptop desktop (and the multiple OS's on my laptop). Sorry to hear about your laptop.

 This is kind of off-topic but while we're there, Backblaze offers unlimited offsite backup for $5/month/computer. I don't have enough valuable data to worry about it, but it's a great option for those that do.

 Also, take a look at LaptopLock (free). If you report the laptop stolen to the website, the next time your computer logs in (is connected to the internet) it will give you its IP address, and you have the option to delete or encrypt your data. It's not a guarantee, but it's something for the cops to go off of if they're willing to look into it.


----------



## Juaquin

Also, does your laptop have remote desktop enabled? If so, and if you're really lucky and the thief is on the school network, you may be able to remote desktop into it if you know the hostname you set up for your computer. Depends on how the school sets up the network, but it couldn't hurt to try.


----------



## nightanole

"Hold on to limited edition carrie for dear life as resale value sky rockets"

 PS: Sounds great, but my gamma2 needed about 24 hours of play to get the bass back to where i like it.


----------



## stwspoon

That really sucks. If you have remote desktop and a builtin camera, you could take a photo of the perp! 
 I take it you didn't get my email with my proposed Carrie changes. Is it OK if I go ahead and layout my version? I can use your images on this thread as a guide.


----------



## Billyk

Oh man, words cannot describe...
 I am a firm believer in karma, you will survive and succeed being such an outrageously righteously great type person, the thief on the other hand shall suffer the appropriately bad fortune they deservedly deserve!


----------



## nightanole

Should we monitor ebay for new carrie boards? Thats how my school got most of their stuff back.


----------



## stwspoon

Don't forget to check Craigslist. Toshiba Satellite A100, right?


----------



## pistolsnipe

3 for 3 on the dacs

 and of course, i screwing forgot to order volume pots.....


----------



## cobaltmute

I've quite liked the RK09712200MC as a pot. No switch, but 15A taper and seems better channel matched than the ones with a switch that I've gotten. Even with the Carrie at gain 2, the combo with the Grub leaves me with the volume down low for comfortable listening.


----------



## pistolsnipe

i like the satisfying switch feeling on the switched pot, but i might order one of those for a cmoy i have. thanks for the heads up

 i cant quite tell, and mine isnt up and running yet, but is the carrie led come from 5v? in that case if i wanted matching brightness and 2 leds, carrie rled resistor value = grub L2 + r8 values correct?


----------



## cobaltmute

IIRC, the Carrie LED is from the V- to gnd so if you're doing joneeboi's stock bom with the 10v reg, that would be correct.


----------



## amc

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_Hey sports fans,

 ...all I can do is hope and pray that the person would return my laptop. Until then, I have to postpone this project indefinitely..._

 

Man. All your lost work and a great project for the DIY community on Head-Fi. Don't think me self centered but I am now kicking myself for waiting on the next round of boards... Sorry to see the Carrie meet an untimely end under such circumstances, and sorry you could not see this through to completion. I feel your pain.


----------



## pistolsnipe

got the pots in, these things are officially badass. sound great, and cheaper than a mini3. hopefully we can get some more boards to spread this awesome project.


----------



## nullstring

so, I'm confused. Is development on this really going to stop?

 The layout and schematic are public for version 1.23..

 It's not at all possible to recover using these as a basis, and continue development?
 if joneeboi isn't willing to do that, I hope that he'll give permission to anyone who does.

 I was really looking forward to this amp, and I wish I would've gotten one of the testing boards =(


----------



## Juaquin

Well I guess it depends on what files are available. If he still has the schematic and board files it would be very easy for someone to pick up development (assuming he doesn't mind). If not, someone would have to redo it from scratch. 

 Or if the gerber files are available it would be very easy to order a few of the prototype boards. In fact, maybe he still has them in an email he sent, or maybe the board house still has them? Joneeboi, if you're around, do you mind checking to see if they're possibly in your sent email (assuming online email) or if the board house has them?


----------



## cobaltmute

The last contact I had from joneeboi implied that he wanted to continue to project. this was based on my offer to put something together.

 Give him time.


----------



## Juaquin

Good to hear! I was under the impression he was really busy, and combined with the loss of most of the materials he had stopped development.


----------



## nullstring

well, he's been working on the project for quite a while, so of course he wouldn't stop.

 IDK, I guess the fact that this thread had slowed down combined with the other comments made me think twice about that.


 I hope to see development get back on track sometime soon. I really want to build this thing =).


----------



## cobaltmute

My understanding is that he is in University. Replacing a laptop is not the easiest thing to do when your budget is tight and who knows what other resources he has to work on.

 The project won't die. I know I can redo his board. However, out of respect, I'm not going there until he says that he is finished.


----------



## joneeboi

Hey fellows,

 I apologize for the lack of updates. I will be continuing this project, but the timing of my loss-of-computer did me in. I am simply too busy with schoolwork to restart this project now, but I promise to get it done during Christmas break. I won't bother looking at old files because I have to completely rework the power supply anyway. I have it all in my head, and it's a pretty simple design to restart. In a way, it's actually good that I lost everything because I can redesign things that I would have been too stubborn to change. It'll be a lot of work, but I'll have way more time come the 15th (my last exam). Sorry for keeping you all in the dark. Yes, I will be pushing this project forward when I am free.

 Jon


----------



## cobaltmute

Good to hear.


----------



## Juaquin

Don't worry about it, we're just glad to hear it's continuing. I still have to build my second prototype anyways.


----------



## joneeboi

It's weird because I never got any of the email alerts I used to get for subscribing to this thread. It just slipped my mind because I never got those emails. Anyway, here I go again back into the darkness.


----------



## joneeboi

Hey all,

 During a Windows Vista-to-7 upgrade, I found a backup of my old laptop hidden away in one our backup drives. That means that we at least have a version of Carrie that doesn't require me to make all the libraries again. I'm currently out of town, so I'll try to push out a presentable version in January. I don't want to drag it out like before, but I do have to re-think the power switching. Shouldn't be too much work, but I do need to give it my attention. I offer my apologies for taking so long with all of this. I can't wait to have a workable version either.


----------



## Billyk

That's good news!
 Glad things are working out. I enjoy my Carrie very much!
 Happy New Year.


----------



## joneeboi

Yes, I finally came up with a v1.24 today. I know it's been a while, but I need to hammer out a bunch of things before I can devote a meaningful amount of time to this amp. I feel good about the preliminary layout I came up with, but it's going to take some time to put out something I feel confident in. It is under the knife right now, however. I do have to get to bed though, and I'll get your inputs when I get something together that I like.


----------



## joneeboi

Taking full advantage of my insomnia last night, this is what I came up with. I'm actually quite pleased with it, so I may push this right out for prototyping. What do you guys think?


----------



## cobaltmute

Very nice. I think the redesign of the power section is good.


----------



## joneeboi

Anyone down for another prototype run? I hope to have this run to make sure everything is okay before I release the group buy version. I'm making a very small run for this stage because I want it to be quick. Takers?


----------



## Billyk

Tentatively, I have most of the parts, but budget is slim....


----------



## joneeboi

Same here. I was going to go with the yellow soldermask and black silkscreen, but the price just shot through the roof. If you are interested, please let me know.


----------



## Juaquin

I'm interested in a board (never built my second early prototype so I still have components) - put me down for one. Don't need anything fancy for silkscreen and mask - as long as it's got good copper traces I'm happy. I'm hiding it in a case with custom-machined panels anyways.


----------



## keyid

I would get a board for the yellow traces.... I have two built and want to make one nearly caseless.


----------



## joneeboi

I'll get the boards ordered in the morning to expedite this whole process. I'm just going to order 5 because this doesn't need to be a big thing. I'm really antsy to just release this project. I think it's actually fine the way it is, but one can never be too sure just before the release of their first major project. =P


----------



## Juaquin

Is the BOM identical? If so I'll get it together as soon as I get the board so you can release it.


----------



## joneeboi

The BOM will be more or less the same, but it's not the official one. I want to work on it and crank a better one than for the last runs. Give me until after the weekend, and the BOM will be solid. The only difference really is the capacitor bank. Let me double check the size. Should be 8mmx15mm. 470uF 16V works from Nichicon's PW series.


----------



## Billyk

I'll go for one, thanks.


----------



## joneeboi

The boards have been ordered. They'll ship out on the 22nd, and I'll get them out to the prototypers as quickly as I can. I'll get the BOM ready after this weekend, and for all the other readers, prepare for a new wave of portable audio.


----------



## joneeboi

BOM is posted on the Carrie support site. Also, the Carrie support site is somewhat up. Let's pull a Google and call it a BETA product. The BOM can be downloaded there.

The Carrie USB Headphone System - Jonathan P. Le


----------



## Juaquin

Good to hear, I'm finishing up my Mouser order for the parts that have changed along with some parts for the GrubDAC.

 Here's a suggestion - would it be possible to put 2-3 vias that are not connected to anything? If the Grub/BantamDAC did the same, you could use paperclips soldered there to provide a bit of a physical connection between the two.


----------



## cobaltmute

On the next version of the grubDAC, there OG pads are in roughly the same place as the Bantam's, so they'll match up with the OG on the Carrie board.

 If there was a via near L1F, you might be able to do something with the mounting hole near there on both the grubDAC and Bantam, but it might be tight against the slot in the case. There was possibly going to be a pad near there on the grub, but I had to take it out during layout changes.


----------



## joneeboi

What I found was that when you pressed the Bantam and Carrie boards real tight, get a good length lead through the OG holes, and solder it, you get a surprisingly tight fit between both boards. That was back when I only had one hole back there. I'm sure with the two pairs of holes, the wiggle gets even smaller when you solder it with the correct sleight of hand.


----------



## Juaquin

Sounds good to me. Now to see if Mouser will beat the boards!


----------



## joneeboi

The boards have arrived (after a little of a timing kerfuffle). I will try to send them out as soon as I can. I'll also upload a picture of the boards when I get a moment with the nice camera. I seem to have forgotten to include some layers in my Gerber output, so there are no component labels. My apologies, prototypers. Nevertheless, the boards look as fine as they can be. It should be a fairly easy build. I was thinking of getting one thrown together last night when I should have been studying, but I decided against it. Anyway, just a late update for the watchers.


----------



## Juaquin

Very excited. I'm sure we'll figure out what goes where - I still have one of the first prototype boards to cheat off of, if I must


----------



## joneeboi

It should be fairly straightforward, but I'll repost layout v1.25. I suspect I didn't really need to run so many prototypes, but being a design newb, I was being a bit paranoid. I built my first one with the 2W 9V converter and 8V regulator, and it seems to be working fine. I only have a Bantam to pair it with though since my PCM2707s haven't arrived yet. I posted pictures of the bare and built boards on the Carrie site, so feel free to check it out. I went with the cool-looking Vishay RN50s because Mouser was out of stock of the regular Xicon resistors in the 470R denomination. Also, the prototyper boards are out via letter mail, so they should arrive in a week and a half-ish. I'm feeling really good about this thing, so get ready for the group buy to come out.


----------



## amc

Watching and waiting. 
	

	
	
		
		

		
		
	


	




 I will take 3 boards once your ready for a group buy...


----------



## Fishline

I'm interested in building one, too. I've gotten the gamma1/2 boards, but have not source the non-AMB parts yet. When the GB for this is ready, I may actually try this before attempting the gamma1/2.


----------



## joneeboi

Well, that's certainly encouraging to know that people are interested. Out of curiosity, who else wants one of the production boards? Having this information is helpful because I currently am down on funds and can't actually pay for the boards until everyone's expressed interest and sent me money. I may possibly be able to borrow money, but I don't know how much to get unless I know how much interest there is. Keep in mind that I want to get the boards with yellow soldermask (Carrie's favourite colour) and black silkscreen, so that adds a premium to the boards; I could get white silkscreen, but that may melt everyone's eyes. 
	

	
	
		
		

		
		
	


	




 I'll get the group buy set up at a future time as the next two weeks in school will be killer for me, but I will hang on to this information until then.

 So, who's in?


----------



## nemmo

I'm in.


----------



## theSeekerr

I'm in, maybe two boards depending what the price comes to.


----------



## nemmo

Yeah, is there any indication for the price.


----------



## Postal_Blue

I'm in.


----------



## sandbasser

I would like 2 of the prod boards.


----------



## Fishline

I'm in for 1, possibly 2.


----------



## pistolsnipe

i would be in for around six, depending on the price


----------



## aphexii

I may be in for 1 or 2 depending on price as well


----------



## joneeboi

It's a vicious circle of uncertainty. To get a quote, I need numbers. To get numbers, I need a quote. The more, the merrier, so tell your friends.


----------



## liwei

I'm interested in a board.


----------



## Billyk

Definitely, you'll want these. I love mine (Original proto) and use it daily. I have another on it's way to a friend in my music downloading group. I would like at least three more to help amortize the price of the second proto. 
 Can't wait to hook up the new one with a grub DAC!


----------



## keyid

w/ grub dac try this player called cPlay. cMP² | Main / HomePage
 Its sounds alot better than foobar w/ aiso. It uses asio but its non fatiguing and also not user friendly but it sounds good. Only loads cue files w/ flac or wav.


----------



## Pentops

I'll take 2 boards.


----------



## Andrew_H

I`ll take two if you can ship to UK.


----------



## jnear

I'll take 1.


----------



## limpidglitch

Ah hell, I'll take one. Got to start this DIY stuff somewhere.
 I presume being over here on the other side of the Atlantic poses no problems?


----------



## joneeboi

Yeah, I have no problems shipping overseas. I haven't had any problems with it so far (except for writing the wrong address), so it's fine. Customs is relatively easy to fill out with Canada Post. Please keep in mind that I'm only taking this information as a survey. I will make a more official group buy thread when I have more time to work on this, and I will PM each of you as a reminder. I appreciate the interest.


----------



## pistolsnipe

how much is the price difference in yellow vs standard? are you putting this in a clear case?


----------



## limpidglitch

Just thinking.
 If there are enough people interested in a full kit, would you be willing to organize it?
 I know you said you are a bit short on cash, but maybe if money were offered up front?
 It would make things super easy, especially for a rookie like myself 
	

	
	
		
		

		
			





 Then again, I guess I should learn how to get a BOM from Mouser some day.

 So only if you're really really OK with it, OK?


----------



## varione

count me in


----------



## nightanole

Hey quick question that i have not tested. Could you use this as a preamp and not need a input cap into a dc strait amp? Im not sure since this have a dc off set of 10-20mv. If this went into a amp with a gain of 20, that would turn into a dc off set of .2v -.4v correct?


----------



## joneeboi

I haven't seen DC offset on this amp higher than 4mV, but if you're plugging it into an amp with gain 20, the offset will go up to 80mV which is unacceptably high if you're plugging it directly into speakers or headphones.

 I can organize kits provided that money is sent ahead of time. That willsave on shipping for everyone, but folks would have to be a bit more understanding with the slowness. If possible, I'd like to restrict that option to overseas customers because I know that overseas shipping is always tough.


----------



## willco007

I'm interested in a board or two as well.


----------



## rds

I'm in for a couple


----------



## joneeboi

Unit price is 10 USD per board. I'll require about 5 USD per shipment, and if you're interested in a kit, that'll run at least an extra 5 for shipping; kit price is TBD.


----------



## theSeekerr

I can confirm that I'd buy 2 boards at $25USD shipped. Looking forwards to this project, one can never have too many headphone amps.


----------



## rds

EDIT I think I'll just go for one then.

 Joneeboi - have you looked into shipping with small package air mail? The requirement is that the package must be no thicker than 2cm, but the rates are very good. Should be perfect for shipping PCBs.


----------



## Andrew_H

Does the board price include the ferrite beads ?


----------



## joneeboi

The board price does not include the ferrite beads. They are available at both Mouser and Digikey, so it's not as necessary for me to ship them. Where are you ordering from?

 The shipping cost is meant to cover the price of shipping from Imagineering, a plastic bubble wrap envelope, and the fee for shipping service. I don't actually remember the name of the servce by which I'll ship it, but it's how I shipped the various prototype boards. It's probably small package air.


----------



## Andrew_H

I`m in the UK.
 I only asked about the ferrite beads because AMB ships his Mini³ with them.
 Coincidentally, it might be worthwhile contacting him regarding shipping costs overseas.
 I`ve had a few things from him (including boards) and he was able to ship them very
 cheaply, albeit via the slowest form of airmail.
 BTW, great work so far.


----------



## Fishline

Just to be absolutely sure: that's DAC and amp on a single pcb, not like the two boards put together shown in the pics on the support site, right?


----------



## cobaltmute

Quote:


  Originally Posted by *Fishline* /img/forum/go_quote.gif 
_Just to be absolutely sure: that's DAC and amp on a single pcb, not like the two boards put together shown in the pics on the support site, right?_

 

It would be just the amp.

 The DAC (either grubDAC or BantamDAC) are available from Beezar


----------



## limpidglitch

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_I can organize kits provided that money is sent ahead of time. That willsave on shipping for everyone, but folks would have to be a bit more understanding with the slowness. If possible, I'd like to restrict that option to overseas customers because I know that overseas shipping is always tough._

 

Slowness schmoness, the world's not about to end, is it?

 Just found out that I probably should take two, as I'm likely to screw it up at least once. 
 And if I don't it will be a very nice present. As I see it this is precisely the sort of Head-Fi gizmo the average person could appreciate, simply because of it's plug-and-play-ability.


----------



## joneeboi

See post 649.


----------



## Anonanimal

As I don't see the official thread yet I'll post here!

 Count me in for two.


----------



## joneeboi

My apologies, everyone. I'll transport all your information to the official thread once it's approved. I'll PM everyone to confirm numbers.


----------



## joneeboi

Alrighty, folks, the official group buy thread is now open.

http://www.head-fi.org/forums/f51/ca...up-buy-470305/

 Please note that I will be collecting funds beforehand so that I can put the order through with Imagineering. Also, I won't be personally making any money off this group buy. Any additional pennies will be donated to an established charity (which I still have to choose).


----------



## Juaquin

Thanks for all the hard work, joneeboi. I'm checking the mailbox every day for my prototype. Also, you might want to add a ballpark price to the group buy thread so people know (of course, this depends on final numbers, etc, but it looks like a good many are interested).


----------



## joneeboi

Your suggestion has been implemented, Juaquin. Thanks for the tip. 
	

	
	
		
		

		
		
	


	




 edit: I sincerely apologize to everyone for the confusion. I polled the group buy thing about 3 times, and everyone's posting and PM-ing me. I probably should have waited a bit. Anyway, you all should have PMs in your inbox, so please update me as soon as possible.


----------



## Lil' Knight

Is there any chance you can offer the kit for the amp and grubdac together? If yes, I'm in for 1 kit.


----------



## joneeboi

Quote:


  Originally Posted by *Lil' Knight* /img/forum/go_quote.gif 
_Is there any chance you can offer the kit for the amp and grubdac together? If yes, I'm in for 1 kit._

 

I'm not currently offering any kits for the Carrie Amp, and I don't offer kits for the grubDAC either.


----------



## joneeboi

I put together a possible final draft. There won't be many more electrical changes, if any, but it'll be mostly aesthetic at this point. I added another filter inductor between the DCP and the negative rail because it was getting massive ripple. It's meant to deal with the switching noise of the DC-DC converter, so it should mostly be dealt with after this inductor addition. Here's what the rails looked like AC-coupled on the 'scope.

 Positive Rail:





 Negative Rail:





 I sent the files to get a quote for 50 boards. I'll let you know how that goes.


----------



## Juaquin

So I got around to building my v1.25 Carrie tonight - don't get too excited though, my GrubDAC isn't done yet so I have yet to test it, other than verifying that the boost converter is working correctly. Here are some pictures though: MobileMe Gallery


----------



## Billyk

Looks good! My order to Mouser goes out Friday (payday).


----------



## Johnthurston

Is the BOM found at http://www.ualberta.ca/~jple/carrie/bom.html up to date for the group-buy which closed on Feb 18, 2010?
 It is listed as v1.25 on the web page (but 1.03 inside the excel document) and in my quick perusal is missing L2F (which I'm assuming is just like L1F)


----------



## joneeboi

I've updated the BOM and layout images. L1F and L2F are indeed identical, and I lined up the version numbers.


----------



## varione

Did anything else change from the BoM besides the missing L2F?

 I guess I should have waited to order...stuff just came in today for bantam and the carrie. I just copied the BoM exactly and only ordered one of the inductors. Are you able to add-on to backordered parts at mouser or will I just have to place a new order?


----------



## Postal_Blue

I know your crazy busy atm jon but the link is dead for me.

 I too am in the "oops I forgot l2f" camp. I will be placing an order with mouser in the next day or two for another build and will be tacking on the inductor. If anyone finds themself in this situation, let me know, no need to eat shipping on a .17 part.


----------



## Fishline

Even though this is a DAC question, I think there must be other newbies like myself who are interested in this: Can some kind soul give a summary of differences between the Bantam and the Grub, especially with respect to Carrie? I'm trying to decide which one to go with.


----------



## ShinyFalcon

There are less parts on a Grub, and can be more appealing to a beginner. Otherwise, the only difference is between Texas Instrument and Wolfson, and whether one prefers simplicity (Grub), or slightly more discrete and customizable (Bantam). I don't know which of the two draws less current, but if the problems with the Carrie overloading the computer's USB port is fixed then there shouldn't be too much of a difference between the two.


----------



## cobaltmute

Quote:


  Originally Posted by *Fishline* /img/forum/go_quote.gif 
_Even though this is a DAC question, I think there must be other newbies like myself who are interested in this: Can some kind soul give a summary of differences between the Bantam and the Grub, especially with respect to Carrie? I'm trying to decide which one to go with._

 

The main difference between the Bantam and the Grub is the signal chain on the board. In the Bantam, USB and DAC functionality are handled by one chip, the PCM2702. In the grub, this is handled by two chips, the PCM2706/7 and the WM8524. 

 The PCM2702, outputs mid-rail DC (at 2.5V), requiring the use of blocking caps to ensure that the DC doesn't not get into later components. The WM8524 is a ground referenced DAC chip. It uses a charge pump internally to create a negative rail and then references it output to ground, requiring no output caps. 

 Output caps "color" the sound, which is why many people chose different caps for different reasons. I'll make no claim as to which sounds better, they just sound different. Considering both can be built for a low cost, it is up to you to decide which you like more.

 From a practical build perspective, the Bantam uses a standard large USB B connector, while the grubDAC uses a mini-USB. The grub has a header spot allowing for easier pulling of the 5V and the GND to carry onto the Carrie PCB.

 Also from a practical build perspective, the grub is currently out of stock at Beezar. We've run out of proto's and are about to order the production boards.


----------



## Fishline

Thanks a lot, Cobaltmute and ShinyFalcon, for the very useful info! I will try to catch the grub production board bandwagon then. Should I keep my eyes on the grub thread in the diy forum, or will there be a GB thread, or something else?


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## cobaltmute

It will be announced in the grub thread when the boards are in stock at Beezar. Very shortly some pictures of the final board will be posted in the grub thread.


----------



## keyid

i tried both with the carrie; get the grub!


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## joneeboi

Quote:


  Originally Posted by *varione* /img/forum/go_quote.gif 
_Did anything else change from the BoM besides the missing L2F?

 I guess I should have waited to order...stuff just came in today for bantam and the carrie. I just copied the BoM exactly and only ordered one of the inductors. Are you able to add-on to backordered parts at mouser or will I just have to place a new order?_

 

 Quote:


  Originally Posted by *Postal_Blue* /img/forum/go_quote.gif 
_I know your crazy busy atm jon but the link is dead for me.

 I too am in the "oops I forgot l2f" camp. I will be placing an order with mouser in the next day or two for another build and will be tacking on the inductor. If anyone finds themself in this situation, let me know, no need to eat shipping on a .17 part._

 

If you forgot a part, send me the money for the part and I can order it and ship it with your PCB.

 The link was dead because I was fixing it. The BOM should be fully operational now. I still have to add the international part numbers, but I have to juggle all this money coming in now. 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *ShinyFalcon* /img/forum/go_quote.gif 
_I don't know which of the two draws less current, but if the problems with the Carrie overloading the computer's USB port is fixed then there shouldn't be too much of a difference between the two._

 

I didn't see this problem until I hooked the Carrie USB Headphone System into a friend's Macbook. I can't guarantee this, but I believe using a 1W DC-DC converter *may* fix the problem. IIRC, the one I used had a 2W converter. There's plenty of capacitance to make up for huge instantaneous current draws, so a 2W may not be necessary. Turning off the amp before plugging it in *may* also fix the issue, but I don't know until I can test it on his computer. All the PCs I've plugged it into haven't complained so far. The max current draw from the PCM2702 is 225mW and that of the PCM2707 is 242mW, so going with a 1W DC-DC converter should keep you safe. And even if you used the 2W chip, you should still be within USB 2.0's limits. Anyone else care to chime in?


----------



## Juaquin

Well I have a current-gen 13" MBP so as soon as I finish my Grub this weekend I'll let you know. I also have access to dozens of computers (Mac, PC, laptops, desktops) where I work so I'll test that out next week.


----------



## cobaltmute

If you recall I have an issue with a 2W DCP Carrie, grub, Windows 7 and Thinkpad X61. The port will end up disabled by Win 7, but if you re-enable it works. When I put a meter in between with peak hold, the combo pulled IIRC 800mA to start. I have one USB cable (from an iRiver) that it works with. This cable has a ferrite on it. If I use I dual power USB (two USB A to one mini-USB), I'm fine as well. On a similar hardware X60 with XP, it shows an error that the amp pulled to much power, but leaves it enabled.

 I think the issue is around timing. The voltage regulator is in drop-out while the DCP is starting up. This allows more current through than some USB power management switches tolerate. It is then up to the OS to decide what to do.


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## joneeboi

New board pictures are up.


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## Swimfar

Do you have any dimensions for the face plates? If not I think I can come up with an approximate layout using data sheets for the pot, output jack, and usb jack. I have access to some tools right now that I may not have in a few weeks so I want to make up a few face plates while I have the chance.


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## pistolsnipe

i believe that the front plates are the same as the mini 3, there are dimensions on amb's site


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## cobaltmute

DKJones96 had posted some FPE files before, but they are not on the hosting site anymore.

 These are the files I did my panels with the grubDAC proto boards. At least on the ones I ran, they were up a fraction high, so if I were to run the boards again, I would move the holes down a smidgen.

 Give me a couple of days and I'll post updated files that have the USB connector in the right spot for the production grubDAC boards.


----------



## joneeboi

Quote:


  Originally Posted by *Swimfar* /img/forum/go_quote.gif 
_Do you have any dimensions for the face plates? If not I think I can come up with an approximate layout using data sheets for the pot, output jack, and usb jack. I have access to some tools right now that I may not have in a few weeks so I want to make up a few face plates while I have the chance._

 

 Quote:


  Originally Posted by *pistolsnipe* /img/forum/go_quote.gif 
_i believe that the front plates are the same as the mini 3, there are dimensions on amb's site_

 

Pretty much copy the Mini^3's faceplate minus the input jack and you should be good. Consider that I used to call this project the Bus-Powered Mini^3. I tried as much as possible to mimic the position of the pot and output jack.


----------



## joneeboi

I updated the website with Mouser BOMs for the Carrie, bantamDAC and grubDAC. Some parts are out of stock, so you're going to have to find replacements on your own. That should be a fairly simple task using Mouser's system. Find another component with the same value and package*, and you're pretty much good to go.

 *For resistors and inductors, you're choosing between either "through hole - axial" and the various packages for SMT, 1206 and 0805 usually.
 For capacitors, you're looking between "through hole - radial" and the the various packages for SMT, 1206 and 0805.
 For ICs, you're choosing between SOIC8, TO92, SOT23 and QFP32. If you can't find replacements, you're likely best off getting the part from Digikey or amb's audio shop.

The Carrie USB Headphone System - Jonathan P. Le


----------



## cobaltmute

I figured I state this publicly so someone didn't have any issues in the last half hour:

 The Mouser BOM linked to for the grubDAC is the prototype version, not the final production version. As tomb has done a wonderful job with the click-through web and excel formats, I would stick with listing those.


----------



## joneeboi

Woopsies. I'll get that fixed right away.

 edit: It is now fixed. C3-7,12,13 was out of stock, so I picked a replacement that should last a while. The original part will be in stock in November or so.


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## Juaquin

I finally managed to get the time to throw together my Grub/Carrie combo and I have a problem - when I plug it in to my MacBook Pro, it's recognized as a USB audio device, but when I turn on the Carrie, it disappears. I'm guessing this is due to the Carrie trying to draw too much current, which causes the MacBook to freak out and kill the connection. I'm using the Grub Proto and Carrie 1.25, if that helps.

 Would removing some of the capacitor bank help to limit the inrush?


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## cobaltmute

Can you reset the port in OSX? In Win 7, I had to do a disable and re-enable.

 This sounds like the same problems that I had with my Thinkpad and Windows 7.


----------



## Juaquin

Not that I know of. So far I've been able to trick it by turning it on, leaving it until the caps have charged, and then quickly unplugging it and plugging it back in. That way it re-recognizes the device, and there isn't a huge current draw because the caps are still charged. [EDIT] Scratch that, it only worked once

 I'm considering removing some of the caps. Might sacrifice a little performance but it would be worth not having to fiddle with it.


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## cobaltmute

Removing caps didn't work for me but mine was setup to power up fully on plug in. The two thongs that worked were two different USB cables. One had a ferrite on it and the other was a USB cable with dual connectors on it from a portable hard drive enclosure. 

 I think I know of a way to solve this but it might mean a little PCB.


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## cobaltmute

Juaquin, which DCP and what voltage reg are on your Carrie?


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## Juaquin

I'll check the exact models in the morning but I know it's a 12V DCP regulated to 10V by regulator (and then split to +/-5V).

 I was considering the dual USB cable, which would be ok if not a little hacked together.


----------



## joneeboi

Bah, more problems with Macbooks. I thought the 1W chip would make a difference, but it seems it may not. The dual USB port option may be the easiest solution at this point. Does the PCM2707 identify itself as a 500mA device, cobalt? I think my PCM2702 does, but I'd have to double check that.


----------



## cobaltmute

The proto's identify as a 100ma and the production ones as 500ma. I hacked a proto to show 500ma and it made no difference for me.

 The issue, I think is that there are current switches on the USB ports. These can report to other components if the draw is above 500ma. I think the results are OS and hardware dependent as on the same hardware but XP versus Win7 got different results.

 What I might suggest as a workaround is a little board with a TPS2115 on it between the DAC and the Carrie. You can tell the TPS2115 to current limit the output to whatever you want, and that could possibly stop the overdraw on startup. Set the limit to something like 400ma and hopefully all should be good.

 It might be good to get a meter on the power lines into the Carrie and see how much current it pulls at start up.


----------



## Juaquin

Yeah, I'm at home for break with practically zero tools right now. When I get back next week I'll hook up the DMM and see what's going on as far as current. I'll also try a dual USB cable. Definitely interested in trying out the TPS2115 solution. If that works maybe it can be implemented in a future Carrie revision (even if it's optional).

 Also, how do you hack one of the protos to report 500ma? If I hook up the TPS2115 for 400ma I still need to report more than the proto 100ma.


----------



## cobaltmute

The hacking of the PCM2707 involves lifting pin 16 - PSEL up from the board and then you tie it high by bridging it to pin 15 ensuring that it doesn't get soldered down to the PCB pad for pin 16.

 Note that this is only a logical change. Many devices pull more than 100ma with out even reporting usage to the host (i.e USB fans etc), so the actual current limit imposed is by actual draw and not by the reported value. 

 I'm fairly certain that the TPS2115 should works based on nightanole's experience back here where the chip was causing him issues in trying to power the Carrie from a gamma1. The issue is a what level to limit the current draw so that the DCP starts up properly. 

 I'll admit that the next week is jammed up for me so I won't be able to consider doing anything for at least that long. It should be fairly easy to make the board however and it could be a simple little board that could be inserted inline on the power to the Carrie.


----------



## Juaquin

Sounds like a plan. Once I get my rotary encoder project (for my LCDuino setup) done I'll take a look at this TPS2115. Is there a simpler chip for this that anyone knows of? This one allows switching two power inputs and limiting both, but we really only need to limit one source, no switching. Can't hurt to go overkill but seems like a waste of such a complex chip.


----------



## cobaltmute

I did some very brief looking on the TI website. There are other chips but the devil may be in the details. The I looked over which looked to be perfect for the job specifically mentioned that it may not handle very short term demands well - which is what we want here. Based on nightanole's experience, we have a good chance the TPS2115 will work. I suspect that there may be other that will work as well.


----------



## Juaquin

Got it. A couple of those will be on my next Mouser order.


----------



## Juaquin

I got the chance to do some testing and I've found a problem. I disconnected the ground between the Carrie and Grub and put the DMM between them to measure current and got 0.04A (40mA), which seemed unreasonably low, and certainly shouldn't be enough to trip the USB port. So I went around measuring voltages, and between Gnd and the DCP output I measured ~1.2V, which is way less than the 12.6V the DCP010512BP is supposed to produce. I guess I damaged the chip at some point. Something else to add to my Mouser order.


----------



## joneeboi

Here is a possible quick fix for people using Macbooks and other incompatible computers:

For only $1.31 each when QTY 50+ purchased - USB A Male to USB A Male and USB Mini-B 5pin Male cable - 2.5ft | USB 2.0 Cables - A Male to A Male


----------



## Postal_Blue

My carrie is up and running along side a Grub. Everything works perfectly when uncase however as soon as i get _both_ boards into the case it stops working. either board in the case alone works find. I put teflon under the boards to insure i an not sorting any leads to the case I am 100% confident that is not the issue. It seems if i hold the carrie board up (not allowing the ground plane to touch the case it will work..... very strange


----------



## joneeboi

So the Carrie works fine alone in the case but not with the grub in as well? That's very odd. Care to share some pictures of the connections? What stops working? Does it stop playing music, does the USB connection get killed, etc.? Is the grub's ground connected to the case too?


----------



## cobaltmute

On the production board, the mini-usb of the grub is connected to USB ground, so if it is touching the case, that could be a ground issue. Other than than, there should be nothing on the grub that would touch the case/ground of the Carrie.


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## joneeboi

That's odd. Why would there be a ground issue? I want everything to connect to USB ground. The ground plane on the Carrie is meant to connect to USB ground. It works fine on my Carrie+Bantam box.


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## Postal_Blue

On one computer it would kill the usb when i get the carrie in the case... On my home computer it will still play music but i get a lot of popping. This goes away if the carrie is pushed up as high as it can go in the slot not allowing the ground plan to make contact with the case. This is with a proto version of the Grub. In fact I am suing it right now with two pieces of Teflon which effectively lifts the Carrie so the only ground connection it has is from the Grub USB ground to the OG on the carrie.

 Side note it sounds very very good when it is working.


----------



## cobaltmute

If you're talking a proto grub board, there should be nothing that would be exposed that would be touching the case. That being said, the way they were routed, there could be some of the ground plane exposed along the edges.

 Is there something along the back edge of the Carrie that could be touching the grub when the two boards are pushed together in the case?


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## joneeboi

Not really. On the production version, the capacitors are several mm away from the back edge of the PCB. There's nothing that really sticks out. The closest thing would be L1F, but even that one's relatively far away from the edge.

 Hm, that's very interesting. Can you measure the voltage between the Carrie ground plane and USB ground? It sounds like the ground plane isn't being connected to USB ground properly.


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## Postal_Blue

Apparently my grub board had a little ground plane leakage around the perimeter. I taped the edges of the grub and it is happy as pie now in the case


----------



## Postal_Blue

I have a newer grub board I think i will swap it in when i get some more 2707's. This old one may find its way into my CKK3 case


----------



## Lil' Knight

Just got my Carrie board. Looks really nice. Still waiting for the Grub pcb from Beezar. Anyone knows where to find the PCM2707PJT now? I know Mouser and Digikey both run out stock.


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## Juaquin

I hear Beezar will be getting them for the GrubCable kits before Mouser or Digikey's estimated time, but I don't know if they'll be sold individually.


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## joneeboi

It appears I may have overlooked some of the grounding discussion, so I feel I should clear it up a bit. The USB ground sits at a different potential from the ground planes because of the filtering on the DAC's USB input, both for the bantam and grub. It should be okay for the ground plane on both the Carrie and the DAC to touch the case so long as the USB input connector doesn't. This means that when drilling your back panel for the Hammond, make extra room for the USB connector. It shouldn't touch the panel at all, or there will be grounding problems. On the bantam schematic, the L4 inductor is effectively shorted anyway, so it shouldn't be much of a problem there, but with the grub, it can cause problems.

 I still don't see why it would be a problem with having the grub's ground plane touching the case. It's directly connected with the Carrie's, so nothing new is happening with the grub's plane shorting to the enclosure. Any ideas?

 Glad to hear your rig is up and running, Postal.


----------



## tomb

I'll let cobaltmute speak for the grub, but the Bantam's USB connector is fully connected to the Bantam's ground plane. I'm not sure how that fits in with the discussion, but touching the USB connector or groundplane on the Bantam should be one and the same.


----------



## cobaltmute

On the protoboard, the USB connector is not connector to ground on the grub. The ground plane is attached to cable ground through a ferrite.

 On the grub production board, the USB connector is tied to the cable ground which is then passed through a ferrite and onto the ground plane. Due to the ferrite, there could be a small potential difference between the connector and the ground plane.

 The ground at the input of the DCP comes from USB ground. The output of the DCP is rail split and the 0V of the rail split is tied to the same ground as the input to the DCP. It is this ground is exposed to the case, and being tied to USB ground should be the same ground as the plane on the grubDAC (which is also the grub's output ground).

 My head hurts trying to figure out what went wrong...


----------



## joneeboi

Mine did at first too. =T

 All the grounds on the PCB should relate to the filtered, post ferrite ground, meaning that it isn't exactly 0V, and Postal's grub PCB should be able to touch the case no problem. I suspect there is more to it than that. I wonder if his USB connection is shorting to the enclosure. That would kind of explain why the signal would cut out when the Carrie's ground plane hit the case too.


----------



## particleman14

hey guys so I'm just finishing putting together my 1st carrie and grub boards. however when I turn on the amp.. the front led light intermittently blinks and i get no sound from the amp.. the grubdac works fine it's just the carrie led keeps oscillating when i turn it on.. any ideas? I'm sure its something simple as always.. here are a couple pics. carrie - Imgur


----------



## pistolsnipe

not sure if it matters but on my build i tied the output ground to the input ground, as opposed to you using the usb cable ground?


----------



## particleman14

can you post a pic of how you wired yours up?> still not sure where my ground should go..


----------



## pistolsnipe

hey, sorry to give you bad information, but i was wrong on all accounts, the proto board layout is different, and that threw me. yours looks good.

 what hapened to your c4?


----------



## particleman14

i burned off the bottom pad so i had to solder using the top pad.. only way it would connect.


----------



## particleman14

so ya guys both of my carries are exhibiting a similar problem. both of the grubs power up and are giving good 5 volts to the carrie boards. However, i am now getting no led indication for either. when i switch the amp on i can hear in my headphones some static, but still no go on led lights and sound. could the problem potentially be my Rled choking the power too much? anyways i'll keep plugging away..wat values for the rled is everyone else using i have 1.5 and 1.8kohms..


----------



## joneeboi

Quote:


  Originally Posted by *particleman14* /img/forum/go_quote.gif 
_hey guys so I'm just finishing putting together my 1st carrie and grub boards. however when I turn on the amp.. the front led light intermittently blinks and i get no sound from the amp.. the grubdac works fine it's just the carrie led keeps oscillating when i turn it on.. any ideas? I'm sure its something simple as always.. here are a couple pics. carrie - Imgur_

 

Hm, that's peculiar. Can you give us your voltages? V+, V- around the opamps, output of the DCP, voltage after the filter. Also, can you check the DC offset on your AD8397?

  Quote:


  Originally Posted by *pistolsnipe* /img/forum/go_quote.gif 
_not sure if it matters but on my build i tied the output ground to the input ground, as opposed to you using the usb cable ground?_

 

That's fine. That's actually preferred.


----------



## particleman14

at dcp pins i get 5 volts in.. 1 volt out. my ad8397 gets + and - .99 volts 
 dc offset seems to be huge.. .975 volts.. what would cause this?


----------



## joneeboi

That might be caused by the impedance of the filter network. From the previous prototype, the L2F component is the new addition, so maybe it's having interactions with the other filter elements that the DCP doesn't like. u_u""

 A simple and ugly fix is to try to short that L2F and see what that does. That effectively takes it back to the previous prototype schematic, and you're gonna get slightly imbalanced rails with huge ripple on the negative rail. Nevertheless, see if that works. That's what changed and that's what worked. It sounds like the DCP is trying to ramp up in the output voltage, but it's dropping again. I wonder why that's happening on both your DCPs.


----------



## particleman14

ok so i shorted l2f and am now getting 40mv offset at my outputs. However still no led or sound.. has anyone else put together their carrie with the grubdac production board?


----------



## joneeboi

That's odd. Everything looks fine in the pictures. Postal_Blue got his Carrie working, so that makes me wonder. You can probably remove the short on L2F too. Try grabbing the input voltage to the DCP from your C1, C5 or C15. The DCP can be a bit of a tricky device. It draws large instantaneous current from the power supply, so the capacitor on the DAC needs to be able to supply it. I had a bit of tunnel vision in this respect because I'm using the bantamDAC which has a huge cap for the PSU, so it's great for the DCP. Nevertheless, it be fine for the grub as well because you're paralleling three low-impedance caps with a good chunk of capacitance. Try changing the input voltage wire to the positive leg of one of those capacitors and see how that works.


----------



## particleman14

bingo. I pulled the voltage from my C5 cap and now it sings.. good call on the dcp. this is my first time messing with one of those.. now both of my carries are working..
	

	
	
		
		

		
		
	


	



 im ordering faceplates right now, will post up some pics when i get them in the mail in a couple weeks.


----------



## pistolsnipe

hey joneeboi, what are your thoughts on a 5->12 vs 5->15 volt dcp? is there a performance/stability tradeoff? i noticed that particle man has a 15 volt dcp... where as in my prototype build i had a 12 volt. could that be why he was having issues?


 also in your mouser bom link you have a 5->9 v dcp


----------



## particleman14

ya I was wondering the same thing if the 12v vs 15v dcps made any difference? i actually ordered both but they are supposed to match with the U2( either 10v or 12v) and mouser only had the 12v so i went with the 15v dcp.. I guess we'll wait to see other builds to see if its really an issue.


----------



## Anonanimal

I've got my first Carrie board fully populated (15V DCP), but I'm waiting on some stuff to be able to build up my BantamDAC(s). It might be a while, but I'll let you know what I see when I get to that point. Happy to see you got yours working!


----------



## particleman14

also guys i just spent a bit of time creating front and back panels for the carrie amp. I used the mini3 panel dimensions to make the front panels (I did a trial fit from my own mini3 panel to the carrie amps to make sure they all lined up and they do!)
 and i carefully measured the rear usb jack dimensions to create the rear panel.
 If enough people are interested maybe we could do a group buy to bring down the costs. or if you just want the specs pm me and I'll try to send them to you. 
 so far my costs are 18$ front and 16$ rear panel per.

 here are some preliminary pics carrie - Imgur
 (sry about bad cropping, had to download a crappy dxf to jpeg converter )


----------



## joneeboi

He resolved the issue. His DCP0105 didn't have enough instantaneous input current, so grabbing the power from one of the grub's electrolytic capacitors solved it.

 Working with

1W DCP chip with maximum 85% efficiency;
whatever efficiency you have with the TL750L regulator series;
AD8397 current draw of slightly over 24mA at just over 10V;
max power supply input of 12V on the OPA690 (my 15-12 prototype put out 12.6V after the regulator) and its current draw;
the current needed by the TLE2426 to keep the rails centred around ground;
and some Macbooks' and PCs' inability to supply sufficient power, let alone any 2W chips;
I felt more comfortable having the 12-10 combo as the standard config. 

 Also, if you want to do a group buy, you have to run it past the powers that be. So they make sure you're not making any money off the process and that you don't scam anyone and what not.


----------



## particleman14

ya if there are enough people ill do a thread in the group buy. just doing a little interest check to see if its even feasible..


----------



## Anonanimal

With respect to the front panels, I'll probably be designing my own, but thank you very much for the group buy offer.

 Also- great work on the board layout joneeboi. Very easy to build, and looks great when it's populated.


----------



## cobaltmute

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_He resolved the issue. His DCP0105 didn't have enough instantaneous input current, so grabbing the power from one of the grub's electrolytic capacitors solved it._

 

If you're going to grab off an electrolytic, the only one you can use is C5. I would advise that you used the Digkey part suggested for that (PS-C 560uF) as that is about the largest that will fit the 6.3mm diameter layout. To simplify wiring, you could omit the LED on the grub and use the LED point as for the wire connection. That should be close enough to the cap.


----------



## tcpoint

If you get a group buy on the panels, I'll take two sets.


----------



## jezz

If the group buy gets started, I'd be up for a couple sets as well. Every time I DIY my own panels, I end up spending more time with the panels than with the amp itself and usually regret not going to FPE from the start.


----------



## sandbasser

count me in for two sets of panels.


----------



## TeraHz

Just got my boards today. They look awesome.

 Looks like DCP010512BP is On Order from Mouser and also missing from Digikey. There are 33 DCP021212P's from mouser which are 2W (0.167 mA). Can they be used? 270-470-RC's are gone as well for a couple of months.


----------



## joneeboi

The DCP021212BP can't be used because it takes a 12V input. It has to be a DCP0105B or DCP0205B device for a 5V input.


----------



## TeraHz

Oh, my bad. I didn't even realize these have different Vin. 
 In that case I'll order from digikey. They should have it in a couple of weeks.


----------



## joneeboi

I seem to be short all my rail capacitors and a potentiometer. u_u"" Anyone have spares?


----------



## theSeekerr

Are there any regs compatible with the TL750L series? Neither Farnell nor RS Components have the 10 or 12V version in the right package - the SOIC version is easy to get, but the TO-92 version is unobtanium - out of stock at Farnell and non-existent at RS. And there's no way I'm paying $30 shipping from Mouser on a 60 cent part.


----------



## Pentops

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_He resolved the issue. His DCP0105 didn't have enough instantaneous input current, so grabbing the power from one of the grub's electrolytic capacitors solved it._

 

A better solution would be to add a decoupling cap at the input pins as recommended in the DCP data sheet. In fact, this is the only way I could get my DCP to start up when running off a bench supply. A 2.2 uF ceramic chip soldered between pins 1 & 2 worked like a charm.


----------



## JohN-

GUYS PLS HELP. THE BOTTOM OF THE U5 N U4 AM I SUPPOSE TO SOLDER AS WELL? OR ONLY APPLY THERMAL PASTE? I FORGET TO SOLDER/APPLY THERMAL PASTE AND I HAVE ALREADY SOLDERED ONE OF THEM


----------



## cobaltmute

Quoting amb on the Mini3 site:
  Quote:


 Optionally, apply a very small dab of heatsink thermal compound below the opamp (this is recommended especially for the AD8397ARDZ opamp). 
 

Not required, but advised. 

 I built my Carrie using the versions without the pads. Works fine.


----------



## joneeboi

Quote:


  Originally Posted by *Pentops* /img/forum/go_quote.gif 
_A better solution would be to add a decoupling cap at the input pins as recommended in the DCP data sheet. In fact, this is the only way I could get my DCP to start up when running off a bench supply. A 2.2 uF ceramic chip soldered between pins 1 & 2 worked like a charm._

 

How does it work with your DAC? You're probably right that I should have added a small ceramic in front of the DCP, but the datasheet cited the need for a low ESR for the chosen input caps. From the datasheet for the BOM's little 0.1uF ceramics, it says that DF (dissipation factor) = ESR*(2*pi*f*C), or ESR = DF*Xc (Xc being the impedance of the capacitor). Choosing 

 f = 100kHz
 C = 0.1uF and 
 DF = 2.5

 the ESR of the ceramics works out to ~40 Ohms when the DCP datasheet calls for an input cap with >20 mOhms; the effect of lowering resistance when paralleling multiple caps is greatly reduced when one has an ESR multiple orders of magnitude larger than the other. This is my fault, but I should have emphasized that the DAC caps should be as low impedance as possible. The 1500uF 6.3V Nichicon HZ cap I'm using from Beezar has an impedance of 12 mOhms, and the prototypes and current amp work fine with the setup. I probably should have added it anyway, but I cheated a bit because the amp should always be integrated with the DAC. It's a little bit easier to squeeze all the components onto the board without the ceramic, and there wasn't a problem during the prototyping (as far as I'm aware of) when the DAC/amp setup didn't work because of the missing local cap. I think, in general, it's good practice to have the local decoupling cap regardless because ESR isn't the whole story here, but I ventured not having the ceramic with little effect until now.

 Again, try with your DAC and let me know if that isn't working. I will change that in the next revision anyways. Thanks for chiming in.


----------



## rds

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_How does it work with your DAC? You're probably right that I should have added a small ceramic in front of the DCP, but the datasheet cited the need for a low ESR for the chosen input caps. From the datasheet for the BOM's little 0.1uF ceramics, it says that DF (dissipation factor) = ESR*(2*pi*f*C), or ESR = DF*Xc (Xc being the impedance of the capacitor). Choosing 

 f = 100kHz
 C = 0.1uF and 
 DF = 2.5

 the ESR of the ceramics works out to ~40 Ohms..._

 

You're saying a 0.1uF ceramic cap has an ESR of approximately 40 ohms?! Something must be wrong in your calculation. Here's a general guide on decoupling with ceramics Notice figure 4 in particular.


----------



## joneeboi

I thought it was weird too, but I can't seem to see it...
	

	
	
		
		

		
			





 Good to know that at least _someone_ around here knows what they're doing.


----------



## rds

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_I thought it was weird too, but I can't seem to see it...:frown: Good to know that at least someone around here knows what they're doing. _

 

No not at all, but that number does seem much too high.
 Btw, great work on the PCBs - I'm looking forward to building a Carrie amp


----------



## Pentops

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_How does it work with your DAC? You're probably right that I should have added a small ceramic in front of the DCP, but the datasheet cited the need for a low ESR for the chosen input caps._

 

It works great with my BatamDAC. I only ran into a problem because I was testing out the power supply before putting down the op amps (or hooking up the DAC) and discovered that the DCP was very reluctant to start up.

 Thanks for all the effort you've put into this design! I'm very happy with the finished result.


----------



## Anonanimal

Here's my first pass at a front panel. Trying to keep with the yellow theme, this will have a yellow LED as well. What do you guys think?


----------



## Juaquin

I like the design but personally I like a black background - I already have my panels though.


----------



## Anonanimal

Quote:


  Originally Posted by *Juaquin* /img/forum/go_quote.gif 
_I like the design but personally I like a black background - I already have my panels though._

 

Yeah this is actually the first time I've ordered enclosures that weren't black. Taking some getting used to.


----------



## pistolsnipe

Quote:


  Originally Posted by *Anonanimal* /img/forum/go_quote.gif 
_Yeah this is actually the first time I've ordered enclosures that weren't black. Taking some getting used to. _

 

i really like those panels, but the top carrie label just seems out of place somehow, too big and stretched out or something, maybe try smaller and centered? maybe say "carrie-grub" at the top? i don't know, it is definitely my favorite design that i have seen for the carrie panels though


----------



## joneeboi

Maybe I'll try to make my own FPE panels. It's good experience for everyone, I think.

 Thanks for your words on the design. I'm quite happy with it as well. I built up my production version last night alongside a bantamDAC, and both worked right off the bat. Hallelujah! That's never happened before. I'm quite stoked. They unfortunately don't have any panels, but I should be able to get a set done soonish. It looks so slick. I have some pictures that I have to post soon. I'm starting a new job soon, so I have a full-time job schedule now, no more school hours. Plenty of free time for a second design and group buy.


----------



## Anonanimal

Thanks for the input. I did stretch the "Carrie" out on the top, so you're right on that count 
	

	
	
		
		

		
		
	


	




. I'll mess around with that some more. My two are actually going to have BantamDACs so I'd have to figure out how to fit all of that instead of just adding Grub. I was thinking of having the Mini^3 + BantamDAC callout on the back, where there is more room.


----------



## Lil' Knight

Just finished populating the board. Not sure if it works because I'm still waiting for the Bantam kit from GJA.


----------



## SilverCans

Guys, when I connect my grub/carrie I get USB device malfunctioned. When I snip the 5v wire from the grub to the carrie (ie killing power to the carrie) the dac is recognized just fine. I also tested the dac and it works (hooked it up to my stereo input). What is going on?

 I'm using a laptop. Wired OG pins on the carrie to the OG of the grub. OL-> IL, OR->IR, 5v straight to SW (which I believe is pin1 of DCP010512BP)

 C1+/-, C2-C7 are 330uF
 C1F C2F are 220uF

 Not enough power from USB connector? I dont have any leds hooked up, figured that save power. 

 BTW when I connect a headphone to the jack I can hear hiss (an slight hum, so I know the amp is getting power to some degree)


----------



## Juaquin

What's happening (from what I've gathered) is that the inrush current of the bank of capacitors causes some computers to freak out and kill the data connection, although it still seems to leave the 5V connected. I'm having the same problem with my MacBook. There have been suggestions of using a current-limiting circuit to prevent this but I haven't gotten around to trying it yet.


----------



## joneeboi

Are you using the switched pot? Try connecting the DAC first and then flipping on the amp. Alternatively, you can try a dual-USB cable from somewhere like Monoprice.

For only $1.31 each when QTY 50+ purchased - USB A Male to USB A Male and USB Mini-B 5pin Male cable - 2.5ft | USB 2.0 Cables - A Male to A Male


----------



## SilverCans

I did try powering the dac first then switched the amp (switch is not part of the pot), tried my desktop HP at work no go, get the same error on my laptop USB Device Malfunctioned ... 

 I also tried a powered usb hub, same prob.

 Any ideas?


----------



## Juaquin

That dual USB cable or a current limiting circuit are pretty much the only options if nothing else works. You could try removing some of the rail capacitors, but that will affect the performance of the amp.


----------



## joneeboi

Hm, you'd think that it'd work at least with the powered hub. Are you using the 1W or 2W DCP? The powered hub probably gives each port 2.5W, but I think the whole package probably takes 3W or 4W since the grub pulls 500mA. It comes down to the computer and OS combo, I think. My bantam worked great on my Toshiba with XP, but then it freaked out on both Vista and 7. However, my current HP with 7 works great with it, so it must be how the OS interacts with the laptop and its BIOS (or _something_ *shrug*) that determines how your USB headphone audio system works. Give that dual USB cable a shot. It might be your best chance without having to replace your computer.


----------



## cobaltmute

Quote: 





joneeboi said:


> ... since the grub pulls 500mA.


 

 Huh?  The grubDAC should be pulling no more that 50ma constant.  Startup will be more as the capacitors charge, but two of those are behind a regulator that current limits at 200ma.
   
  If you recall, I found my Carrie alone pulling ~800ma on startup.


----------



## Anonanimal

I'm starting to wonder if it has something to do with the power profiles on everybody's respective computers.  I know my Win7 installation had all sorts of power control enabled when I first booted up.
   
  Has anyone who is experiencing these issues tried turning off all of the power-save features in their OS?  I know it's kind of a long-shot but probably worth digging through.


----------



## cobaltmute

I've said this before, but I believe it is both hardware and software.  Similar hardware under different OS creates different results for me.  XP states the device has malfunctioned, but keeps working.  Win 7 disables the port, but keeps it powered.  A trip into device manager to disable and re-enable to port and all is good.
   
  What I suspect the underlying hardware issue to be is that there is a current limiting switch powering the USB ports.  That switch can indicate to the OS that the attached device is drawing too much power.  I've read about a few of those switches that allow for a turn on tolerance.  So you have a power management device that current limits that may or may not be telling an OS that it has limited the power and then the OS may or may not do something about it.  Great way for indeterminate results


----------



## rds

I would blame the hardware, because you are drawing way more current than the maximum rated current for USB.  Some computers might be more lenient in letting you get away with that, but it doesn't make sense to count on that.  NTC thermistors, resettable fuses, and inductors might be some options.  Otherwise active current limiting circuitry might be required.


----------



## Juaquin

I can confirm that the dual USB cable works on my MacBook Pro 13" w/ Snow Leopard. I still have an error with the Carrie I need to track down, but turning it on did not cause the Grub to be dropped like with the single cable.


----------



## Anonanimal

Quote: 





cobaltmute said:


> I've said this before, but I believe it is both hardware and software.  Similar hardware under different OS creates different results for me.  XP states the device has malfunctioned, but keeps working.  Win 7 disables the port, but keeps it powered.  A trip into device manager to disable and re-enable to port and all is good.
> 
> What I suspect the underlying hardware issue to be is that there is a current limiting switch powering the USB ports.  That switch can indicate to the OS that the attached device is drawing too much power.  I've read about a few of those switches that allow for a turn on tolerance.  So you have a power management device that current limits that may or may not be telling an OS that it has limited the power and then the OS may or may not do something about it.  Great way for indeterminate results


 

 That unfortunately is probably right about the turn-on tolerances.  Too bad it's not something that's easy to find out from a motherboard manufacturer. 
   
  So far as I know the USB 3 spec increased the max current slightly, so we may find that these get easier to use on that bus.


----------



## rds

I feel that putting this: http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=317-1145-ND NTC thermistor in series between the batam/grub and carrie would solve the over-current issue.  But I'm not well experienced using thermistors and I haven't really looked into the specifics of the dc-dc converter.


----------



## cobaltmute

I've tried this thermistor with no startup.
   
http://search.digikey.com/scripts/DkSearch/dksus.dll?lang=en&site=CA&WT.z_homepage_link=hp_go_button&KeyWords=MF72-060D5&x=0&y=0
   
  The issue I think is that the Carrie only draws the high amount of current for a very short time during start up.  After the initial start, the current draw is well within spec.


----------



## joneeboi

Quote: 





cobaltmute said:


> Huh?  The grubDAC should be pulling no more that 50ma constant.  Startup will be more as the capacitors charge, but two of those are behind a regulator that current limits at 200ma.
> 
> If you recall, I found my Carrie alone pulling ~800ma on startup.


 
   
  Quote: 





cobaltmute said:


> The proto's identify as a 100ma and the production ones as 500ma. I hacked a proto to show 500ma and it made no difference for me.
> 
> The issue, I think is that there are current switches on the USB ports. These can report to other components if the draw is above 500ma. I think the results are OS and hardware dependent as on the same hardware but XP versus Win7 got different results.
> 
> ...


 

 I thought we determined that the 800mA startup was because you were using an external PSU and that switching on the PSU instead of flicking on the Carrie made the inrush reading that high.
   
  If the dual-USB cable works for everyone, we can use that as a backup solution. I don't like it as much since most laptops only have three USB ports (mine has four, plus my Carrie works on just one 
	

	
	
		
		

		
			





), but we'll refer to that as *one* method to get the DAC/amp to work. It can be the workaround for this revision. Still, it's better that we find a solution that works for single USB cables. Unfortunately, I've moved away from home and have none of my DIY gear with me. If someone is willing to spearhead a solution like the current-limiting switch, I can play around with the layout to make it fit. I'll continue to look into circuits and solutions to this problem as much as I can.


----------



## rds

Quote: 





cobaltmute said:


> I've tried this thermistor with no startup.
> 
> http://search.digikey.com/scripts/DkSearch/dksus.dll?lang=en&site=CA&WT.z_homepage_link=hp_go_button&KeyWords=MF72-060D5&x=0&y=0
> 
> The issue I think is that the Carrie only draws the high amount of current for a very short time during start up.  After the initial start, the current draw is well within spec.


 

 Hmm yeah, DC-DC converters can be tricky. It might not like having 2 ohms at the input. Another option is to put a thermistor at either the output or input of the voltage regulator.  In that case you'd probably want this one: http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=317-1154-ND  I'll give it a try myself when I have time to build one of these.


----------



## cobaltmute

Quote: 





joneeboi said:


> I thought we determined that the 800mA startup was because you were using an external PSU and that switching on the PSU instead of flicking on the Carrie made the inrush reading that high.


 
   
  It has been awhile, but if I recall correctly, I got the same readings no matter how I powered up the Carrie (from PSU or computer).  However, I do not have a power switch on mine - I just plug them in.  Those readings were Carrie alone - no DAC attached.  Someone else needs to verify those kind of readings on their boards as I have the 2W DCP so mine could be an outlier.  I was using a Fluke with peak-hold to determine the peak current draw.


----------



## joneeboi

That, I remember. You had the DCP02, but even still, a friend tried my DCP01-fitted USB music box on his Macbook and it shut down the device, even when shutting off the amp when plugging in and switching on the amp afterward. We may be able to limit inrush current by limiting output current of the DCP. That's another option.
   
  What do you guys think of the TPS2041B? Seems pretty good from a quick glance.


----------



## Juaquin

Looks good to me. Definitely worth trying. I agree that the Dual USB cable is really only a backup method - the whole idea of the Carrie system was absolute simplicity and integration in mobile audio. The dual cable dampens that as it's not quite ubiquitous and of course requires two ports. My MacBook only has two ports 
   
  I'll add one to my next Mouser order but that'll probably be a while.


----------



## rds

Quote: 





joneeboi said:


> That, I remember. You had the DCP02, but even still, a friend tried my DCP01-fitted USB music box on his Macbook and it shut down the device, even when shutting off the amp when plugging in and switching on the amp afterward. We may be able to limit inrush current by limiting output current of the DCP. That's another option.
> 
> What do you guys think of the TPS2041B? Seems pretty good from a quick glance.


 

 From what I'm seeing that switch current limits at 1A so I'm not clear how that would help.


----------



## cobaltmute

Right from the features section on the first page:
   
  Quote: 





> · Accurate Current Limit (0.75 A min, 1.25 A max)


 
 Although 0.75A is too high. You want to keep it closer to .5A to ensure stability


----------



## rds

Quote: 





cobaltmute said:


> Right from the features section on the first page:
> 
> Quote:
> 
> ...


 
   
  Yes, I saw that too.  From my reading those are the min and max values, with the typically value being 1A.  In other words it's not saying you can adjust it; it's giving the range of possible values.  Are you reading something about it being adjustable?


----------



## cobaltmute

No you are correct. Teaches me to read the datasheet while I am out.


----------



## Anonanimal

Does anyone by chance have either a front panel express file or dimensions for the back panel of a Carrie with a BantamDAC?  I've been waiting quite a while for my kits from Glass Jar and I'd really like to get a head start on the panel order, but I'm not sure of the size/location of the USB cutout.


----------



## particleman14

-


----------



## Juaquin

Quote: 





anonanimal said:


> Does anyone by chance have either a front panel express file or dimensions for the back panel of a Carrie with a BantamDAC?  I've been waiting quite a while for my kits from Glass Jar and I'd really like to get a head start on the panel order, but I'm not sure of the size/location of the USB cutout.


 

 Someone posted them really early in the thread, after the first or second prototype (before the Grub was available). I know that doesn't make them much easier to find but they are here somewhere.


----------



## cobaltmute

The post was by DKJones96 and his files have disappeared off the hosting site.
   
  However I never get rid of anything:
   
http://dl.dropbox.com/u/630887/carrieFPE.zip


----------



## Anonanimal

Thanks guys, sorry for not digging harder in the thread...


----------



## particleman14

just got my panels in the mail.. here are a couple pics of my completed carrie!


----------



## Anonanimal

Looking good!  How do they sound?


----------



## particleman14

sounds great so far.  I am going to do a little a/bing of the gamma-2/grubdac  as I now have 2 mini3 that are identical to try and get a good comparison.  so far really enjoying it.


----------



## Anonanimal

Just fired up my first Carrie System!  15V DCP and a BantamDAC.
   
  Have my beater SR60s plugged in right now and it sounds absolutely fantastic!
   
  Currently pulling power directly from C7 on the BantamDAC board and not having any surge current issues with the amp turn-on.
   
  Thanks for the opportunity to work on this excellent project!
   
  Edit: here are some pictures!
   
  Full Circuit Top View

   
  Bottom View.  I used hot glue to hold the boards together and it worked quite well!


----------



## varione

got mine put together tonight, sounds great!
   
  thanks much for the project!
   
  pulling power directly from c7 on the bantam just like anonanimal
   
  going to just to the  front panels another day....my first time actually and too cheap to buy some


----------



## joneeboi

Great looking work, folks. It's really great to see you come back with pictures of finished builds. It really warms my heart.
   
  Good call on the hot glue, Anonanimal.


----------



## Anonanimal

Custom panels ordered!  I'll update with some more pictures when I get them in a couple of weeks.
   
  Thanks again for all of the work you've put into this project.  This really has turned out to be one impressive little device!


----------



## Nebby

Let us know if they work well  I'm tempted to order a set myself...
  
  Quote: 





anonanimal said:


> Custom panels ordered!  I'll update with some more pictures when I get them in a couple of weeks.
> 
> Thanks again for all of the work you've put into this project.  This really has turned out to be one impressive little device!


----------



## Anonanimal

Quote: 





nebby said:


> Let us know if they work well  I'm tempted to order a set myself...


 

 No problem!  Here's a quick screen cap of the design I ended up using:


----------



## Anonanimal

Just wanted to post an update-
   
  Got my second Carrie (of 2) up and running over the weekend.  I used the same components as the first one- 15V DCP, Gain5, BantamDAC.  Pulling power directly from the Bantam's C7.
   
  These little guys do sound surprisingly good and I just want to say thanks again for such a great project!


----------



## Ikarios

anonanimal, do you have pictures of your amps? I want to take a look at your front panel design, as well as how the Carrie/Bantam set looks (size, etc). Thanks!


----------



## Anonanimal

Quote: 





ikarios said:


> anonanimal, do you have pictures of your amps? I want to take a look at your front panel design, as well as how the Carrie/Bantam set looks (size, etc). Thanks!


 
   
  My front panel design itself is posted in a pic just above, and there are also some pictures of the finished boards themselves higher up on this page.  I don't yet have them cased up.
   
  I should be getting my panels in today and finishing them both up.  When that happens I'll definitely post up a few pictures!  
	

	
	
		
		

		
		
	


	



   
  Edit:  Here they are!


----------



## 3000

@Anonanimal, those look sweet!


----------



## viralbug

Looks great Anonanimal!


----------



## mattcalf

Looks great anonanimal, and great listening choice! 
   
  Particleman14, how'd the comparisons go?
   
  Cheers.


----------



## SilverCans

Guys I noticed that many have solved the power-up issue when using the Bantam via tapping into C7, has a similar solution been found for those using the Grub dac?


----------



## particleman14

tap the power from C5 .. this worked on both of my carrie/grub setups.  ..
   
  mattcalf, I haven't run some good a/b comparisons just yet between the y2 and grubdac.  been a little busy with school (just graduated!)  however my initial impressions are that, surprisingly, the grubdac is not very far away from the y2.  In terms of transparency and overall clarity the y2 wins, but the grub has a kind of mellow and pleasant sound to it; I guess you could say 'warmer".   this is a comparison using 2 mini3 x5 gain.  will post more in depth comparison now that I have a lot more free time on my hands, for the moment.


----------



## Fishline

Looks like the parts for the grubDAC (which I plan to use with the Carrie) are all in stock at mouser now, but some of the parts for the Carrie are out of stock 8-(.  Can someone kindly suggest suitable replacement for the following?
   
80-C062C105K5R (Kemet Multilayer Ceramic Capacitors (MLCC) - Leaded 50volts 1uF 10% X7R 10%)
270-470-RC (Xicon Metal Film Resistors - Through Hole 470ohms 1% 50PPM)
270-100K-RC (Xicon Metal Film Resistors - Through Hole 100Kohms 1% 50PPM)

450-6003 (knob -- I think I can find replacement for this one myself)


----------



## joneeboi

At the bottom of the Mouser product page, there's a "Show Similar" button. I can click it for you, but do you wanna give it a shot? You're almost there.


----------



## Teal

Are there any more boards available (kit preferred)? I'd like to build one sometime in the near future (unless a new version is being worked on).
   
  I'm currently using a Bantam Dac /w a Mini^3 on my netbook and it's a pain having a two piece set of which one needs charging.
   
  Also, how do the two fit inside the case? That looks like the standard case that houses the Mini^3.
  
  Would it better to build the grubDAC? Does it fit in the case and is the quality any better (with the Carrie) than the Bantam DAC?


----------



## Juaquin

The Grub and Bantam are the same size and both will work (the Carrie was designed to fit with the Bantam, and then the Grub was designed to fit with the Carrie). As far as quality, I've listened to both and they're both great. By looking purely at the specifications, the Grub might have an edge (no output capacitors, etc) but I think you'll be happy either way. I'd make the decision based on whether you need the USB B or Mini connector (Grub is Mini, Bantam is B).
   
  Both the Carrie and one of the DACs (Grub or Bantam) will fit into the specified case. I'm not sure if it's the same size as the Mini3 case but I do know that the Carrie is essentially a Mini3 that's been made smaller with a boost converter, so it wouldn't surprise me that the DAC and Carrie fit into the same case as the Mini3.
   
  There are no kits as far as I know; Joneeboi may or may not have extra PCBs - I'll let him respond to that.


----------



## Anonanimal

It's the identical Hammond case that the Mini^3 uses, and they fit almost perfectly.  This is what they were designed to do.  You can find pictures of my builds on the previous page in this thread I believe.
   
  I used the BantamDAC for my two Carries and I do not have a single complaint on the sound quality.  I used the red Wima caps on the outputs.


----------



## VncentValntine

I'd also be interested in a PCB if there are any extras...


----------



## Ikarios

For those of you looking for PCBs:
  be patient 
	

	
	
		
		

		
			




  http://www.head-fi.org/forum/thread/470305/carrie-amp-pcb-group-buy


----------



## VncentValntine

so tapping power from C5 on the Grub works on macbook pros too?


----------



## Juaquin

I've had problems with my 13" MBP no matter where I tap power from, but that was with the latest prototype version (not the current semi-production version). I'll have to build up the latest board sometime and see if that improves.


----------



## VncentValntine

If I were to say I wanted to pair the Carrie with a Gamma1 would I run into the same problem?


----------



## ShinyFalcon

There are more components on the y1 (four) to power compared to the GrubDAC (two). Unless you take off the y1's TOSLINK and CS8416, then you'll probably get about equal power consumption.


----------



## Juaquin

The Grub only draws ~50ma. At least for me, it seems to be that the Carrie is drawing over 450ma (at least at startup), which the MBP detects as a fault and shuts down power to that port. If yours acts the same as mine, there is no DAC that will solve this problem. You'll either need a dual-USB cable or some sort of limiting circuit.


----------



## VncentValntine

from amb's website 
   
  Quote: 





> U1D (TPS2115A) is a power multiplexer chip that allows selection and transition between two input power sources. The external 5V power from the DC input jack (J1D) and the VBUS 5V power from the USB board (through the docking pin socket J4D pin 1) are connected to the INPUT1 and INPUT2 pins of the TPS2115A, respectively. This chip is configured such that normally the power comes from VBUS, but if external power is plugged in, then it will switch to external power. The output goes to the USB board (via J4D pin 2) as well as to two local voltage regulators U5D and U6D, which regulates down to 3.3V and 4.5V (or 4.75V if the TPS793475 is used) for the digital and analog power, respectively. The analog power for the CS8416 and WM8501 chips are further filtered by separate ferrite beads and decoupling capacitors.
> 
> The 3-pin jumper block JP2D is normally unused. However, if the builder wants to omit the power mux chip U1D and hardwire the board to either external or USB power, then a jumper can be used to select the power source.* The power mux chip provides the benefit of controlled-slew voltage ramp-up*, therefore it is not recommended that you omit it unless you have a very good reason to do so.


 
   
  and from Texas Instruments
   
http://focus.ti.com/lit/ds/symlink/tps2115a.pdf
   
  Quote: 





> The TPS211xA family includes extensive protection circuitry, including user-programmable current limiting, thermal protection, inrush current control


 
   
   
  Is none of this related to what the problem is?
  The TPS211xA family includes extensive protection
  circuitry, including user-programmable current limiting, thermal protection, inrush curr
  The TPS211xA family includes extensive protection
  circuitry, including user-programmable current limiting, thermal protection, inrush current control


----------



## cobaltmute

Search the thread - someone has already built a gamma1/Carrie combo.  There was a part change they had to make on the gamma1 or the Carrie will not start.


----------



## VncentValntine

Quote: 





cobaltmute said:


> Search the thread - someone has already built a gamma1/Carrie combo.  There was a part change they had to make on the gamma1 or the Carrie will not start.


 

 thanks, yeah I found that post.  I guess what I was trying to find out was, if the power from the gamma1 was regulated, would it have a surge like the carrie would.  But since now i know the carrie is hooked straight up to the USB's power, that seemed to be what was causing problems.  Having the Carrie feed from Gamma1's modified regulated voltage and current, I'm hoping I can avoid this.  Thanks everyone =)


----------



## joneeboi

Hey all,
   
  Check out this thread. 
	

	
	
		
		

		
			




   
  http://www.head-fi.org/forum/thread/503428/carrie-amp-group-buy-2


----------



## joneeboi

I'm surprised at the low interest in the Carrie for this second group buy considering the number of PMs, emails and posts asking for it. Ah well. Less work for me.


----------



## joneeboi

This is a reminder that the group buy is closing in a little over a week. If you're holding out for some reason, stop and sign up before it's too late.


----------



## joneeboi

I should also note that my final version of the Carrie + bantam box works completely fine on my MacBook Pro 13" (mid-2010) and Carrie's MacBook. I suspect it still won't work on some MBs, but just an FYI.


----------



## joneeboi

One more day for the group buy sign-up. Come one, come all.


----------



## TBomb06

Will 20mm tall caps fit in the spec'd Hammond case? The C-C1+/-,C2-C7 caps are backordered at Mouser and a comparable part at Digi-key is only available in 20mm height. I apologize if this question has been asked and answered before...I did a quick search but found nothing. Thanks!


----------



## jamesbobo007

If I remember right there is only 16mm in the 1455C801, but I guess it depends on what enclosure your using


----------



## joneeboi

Just because the part at Mouser is backordered doesn't mean there aren't other suitable caps at Mouser. For future reference, the product pages at Mouser also have a "Find Similar" button on the bottom left. The dimensions required are 8mm diameter x 15mm height at 16V. Typical capacitance values are 330uF, 470uF and sometimes 680uF, but 470uF should be fine. Any more might have too much inrush current with this design.


----------



## Soymilk

for the schematic in the third post, is it a 12v output from the power part at the top right? from what i read of the thread that's what was the target right, 12v supply -> +/- 6v supply with the virtual ground?
   
  also, is the bank of capacitors necessary between v+/gnd and gnd/v-? on tangent's site's page on virtual ground circuits he only has the capacitor between v+/v- for the one using a tle.


----------



## joneeboi

There is a TLE. 
	

	
	
		
		

		
		
	


	



   
  The output of the DCP010512B is 12V, but it's regulated down to 10 V with the TL750L10 and split to +/- 5V with the TLE2426.


----------



## Soymilk

whoops i left that out of my original question / wording was pretty bad. i meant that bank of capacitors after the tle going from v+ to the tle virtual ground and from there to v-; on tangent's site the virtual ground circuit using a tle does not have those capacitors, it only has a capacitor from v+ to v-. that's where my confusion/curiosity is coming from


----------



## TBomb06

Quote: 





joneeboi said:


> Just because the part at Mouser is backordered doesn't mean there aren't other suitable caps at Mouser. For future reference, the product pages at Mouser also have a "Find Similar" button on the bottom left. The dimensions required are 8mm diameter x 15mm height at 16V. Typical capacitance values are 330uF, 470uF and sometimes 680uF, but 470uF should be fine. Any more might have too much inrush current with this design.


 


  Thanks for the reply. After asking that question, I actually re-visited the BOM on your web site and found that the 470uF would be a suitable replacement, and probably a good compromise with regards to the inrush current. I took the time to read through a lot of this thread and realized the values for those caps don't have to be 680uF.
   
  I'm about to start on my Grub, then I'll be waiting patiently (and excitedly) for the Carrie boards to arrive 
	

	
	
		
		

		
		
	


	




 Thanks for putting together the latest group buy!


----------



## Soymilk

can someone shed some light on what C9-20 are for? i thought the capacitance was only needed from v+ to v- 
	

	
	
		
		

		
		
	


	



   
  also, i'm thinking about making one of these but to be used without a dac, so i was thinking of switching R1L/R/G with a dc filtering cap and maybe adding a bass boost. bass boost being a pot parallel with a cap, placed in series between R4L/R and the output (i think that's where it goes); this wont increase my current draw by too much will it?


----------



## cobaltmute

For the cap question, maybe you should check what I believe to be the latest schematic here You can have capacitance from rail to rail and rail to ground.


----------



## Soymilk

i can see that there are caps both rail to rail and rail to ground, i was wondering if the rail to ground ones were necessary / what they're for though, i thought you only needed caps from rail to rail when using a tle.
   
  thanks for the link though, the bom will come in handy when i finally get around to starting my build


----------



## cobaltmute

A question to answer your question:  how much current can the TLE sink?


----------



## Soymilk

according to the datasheet, 20mA. isn't the purpose of the active ground to sink current though?


----------



## Soymilk

hmm so i saw a piece i'd overlooked before on tangent's page on virtual grounds that explains the caps are for sourcing/sinking current. for the purpose it's being used, it shouldn't be sourcing any current, only sinking right? and doesn't the active ground take care of that?
   
  also, how can i calculate how much current is being sinked? it would change based on the impedance of the headphones being driven right? i built my brother a cmoy like a month ago and i didn't put any caps from rail to ground. he's only driving a hd555 so it's fine for now, but i want to figure out where he should start worrying if he was to upgrade.


----------



## joneeboi

Amps like the MINT, Mini^3, M^3, PIMETA v1, META42, PPA v2 and v1 have large series capacitances on the output of the TLE2426; PIMETA v2 uses smaller values. From Tangent's article on virtual grounds,
   
  Quote: 





> Output caps can be a good thing if the rail splitter has a fairly low output current limit. That’s the situation in the MINT amp, for example. The TLE2426 has an output current limit of between 20 to 40 mA, depending on operating conditions. When it goes into current limiting, its output goes to the negative rail, which would make for a massive shift in the virtual ground point, so we cannot allow this to happen. A heavy headphone load could indeed exceed 20 mA, so putting caps on the ouptut of the TLE2426 saves the design.


 
   
  Checking the TLE2426 datasheet, Figure 17 on page 17 shows how the load capacitance affects the TLE2426's stability. Not much is needed, but the size of the caps is mostly due to balancing the rails as in Tangent's article.


----------



## Lil' Knight

Just populated the Grub. I'm still unsure how to pull the power from C5 to the amp.  Where should I wire the + leg from the C5 to? 5v or SW?


----------



## jamesbobo007

I've finished my grub and starting on the amp now. So I a not sure I understand your question, but my plan is to hook the 5V pad on the amp to the 5V pad, right next to J1, on the Grub.
  You would use the SW pad for an off board power switch.


----------



## Lil' Knight

What I meant is mentioned here 
http://www.head-fi.org/forum/thread/387745/carrie-usb-powered-headphone-amplifier/720#post_6588267
  If I wire the C5's + leg to the amp's 5v pad, where would the C5's - leg go to?


----------



## particleman14

I ran into this problem when mating my grubdac to the carrie board.  I had to grab the + leg from C5 and wire it up to the 5V pad on the carrie board.  Mine would not startup when I hooked the 5V pad from the grub to the 5V on the carrie.  
  Just route a single wire from C5+ leg to your 5V pad on the carrie.  the C5 leg doesn't go anywhere just wire the C5+ pad to the 5V pad on the carrie board and it should be good...


----------



## Lil' Knight

Thanks. Back to solving the problem with my Grub...


----------



## Billyk

Well another one lives. Just completed the build from the recent group buy. Sounds swell, thanks to joneeboi for all the work.
  Little story to go with this one.
  I wired it up to a grub DAC prototype version and it did not fire up. I was getting just shy of 1volt at the output of the converter, ahh I thought need to try the C5 thing. Sure enough, that did it, sweet music came pouring out. I was very happy. I had to take it apart because now my power lead was short and would not reach the C5 position. I used solder braid and cleaned the holes on both the ground and power on the carrie and the ground on the grub, made the new connections... Nothing, the grub fired up but the carrie stayed dark. Drat, I started to take measurements, the grub had 5.25 at the USB V+ and Gnd, it had 5.25 at C5 and USB Gnd, and the same at the carrie V+ in and Gnd, Hmmm... turn on the carrie and the voltage everywhere but the USB V+ went to 2.75v. I was truly mystified and upset. To make a long story short I checked everything several times and then while checking continuity, I discovered that the ground pads on the grub were separate! I must have used a it too much heat cleaning the holes. The ground was contiguous everywhere but to the ground pad I used to connect the two boards. I soldered a bit of left over resistor lead between the two ground pads on the grub, and viola! It was working.


----------



## joneeboi

Sounds great, Billy! Thanks for sharing your experience. I'll have to consider that in future designs. Enjoy the Carrie amp!


----------



## FLACm0nkEy

Interesting project.  This is just what I and another member on the forum were looking for.
  A couple questions (pardon if they have been asked):
  1.  What purpose does the switch in the pot serve in this circuit?  In regular mini^3 it is obviously used to turn it off and conserve battery, however, as this amp is bus powered, there is really no point in turning it off as the DAC will still be on.
  2.  Will there be another batch of boards soon?  If not, would you share the schematic&board files with us?


----------



## joneeboi

Wow, it's been a while since I read this thread. Sorry to take so long to respond, FLACm0nkEy.
   
  1) After all this time, I wonder myself why I used the switched pot. I was trying to limit inrush current, but I don't think I needed it after all. There's a better version of the pot with logarithmic tracking and no switch, which would have saved board space and better performance. It was mostly a convenient solution. I was wrong.
   
  2) I won't give it all away, but someone else may be starting up a group buy. Would if I could. I plan to start another one in 2012, but I'm too busy lately.


----------



## tcpoint

I just finished my Carrie (hooked up to a GrubDAC).  First listen was quite impressive.  I had to get the 5V from C5 on the GrubDAC.
   
  Thanks to joneeboi and colbatmute for their efforts.


----------



## mik000000

Quote: 





joneeboi said:


> 2) I won't give it all away, but someone else may be starting up a group buy. Would if I could. I plan to start another one in 2012, but I'm too busy lately.


 


  any progress on this? i would be interested in a couple if you do.


----------



## Borax

I would also love to get one or two when there is a new group buy (or when somebody has on left?)


----------



## Billyk

If there were enough interest, say 50+ boards, and Joneeboi still has the files around, I think a group but would be cool. I wouldn't mind putting in the time and effort. Plus could use a few bords myself!


----------



## KimLaroux

So what is the status with this project?
   
  I've read the first 30 pages of this thread, which got as far as the first batch of prototypes. Was there ever another batch? Maybe a final official version?
   
  The schematic and board from the second post seems to be the same as the prototype, so I'm guessing no revision was published after the prototypes.
   
  I've been thinking about making something similar for the past months. I searched if such a thing already existed and found this thread. This is exactly what I had in mind. I'd be interested in 2 boards if another batch is planned. Though at this point I think we'd have to verify if the parts are still available...


----------



## Billyk

It is about as final as it will get is my assumption; Joneeboi would be the one to answer that. The last revision works well. The Grub DAC that is in it and the Mini^3 it is based on are still available so I don't think there is an issue with parts. Sooo... all we we would need is enough interest and most importantly Joneeboi would have to allow us to produce the boards. I have made a half a dozen or so and love them and the folks I made them for as gifts treasure them and use them all the time. I would be in for 6-8 boards if this were to happen.
  Billy


----------



## Borax

I finally got parts from another user.
  Now I ran into some difficulties:
  I soldered the Carrie (15V DCP), checked everything and applied 5V to it.
  Output of the DCP is only about 2,5Vpp
  so I unsoldered L1F to check if the output of the DCP would change... it did, Output showed 26Vpp!
   
  I ordered a new DCP, assuming it is broken.
   
  /edit: yep, works like a charm now


----------



## KimLaroux

Well well, look what showed up on my doorstep today:
   

   
  TO-220 package for size reference, because I am blown away by how tiny these are. I expected them to be small, but not THAT small. I'm really impressed.
   
  I hacked SMD circuits before, but never built a whole one. So to avoid destroying the priceless Carrie PCB, I will start with the GrubDAC. Only when I am satisfied with my skills will I assemble the Carrie.
   
  Thanks, Tom!


----------



## Avro_Arrow

Good luck with your builds!


----------



## Lil' Knight

Hmmm.. from my past experience, the Carrie a a much easier to build than the GrubDac. Those smd opamps are very easy to work with, comparing with the PCM and WM on the Grub.


----------



## tomb

Quote: 





lil' knight said:


> Hmmm.. from my past experience, the Carrie a a much easier to build than the GrubDac. Those smd opamps are very easy to work with, comparing with the PCM and WM on the Grub.


 
  I agree completely in principle.  Trouble is, who knows if there will ever be another Carrie board?  Whereas, I can send him a dozen new GrubDAC PCB's if he messes up.


----------



## Lil' Knight

:bigsmile_face:


----------



## Billyk

I would still be up for another round of carrie boards....


----------



## tomb

Quote: 





billyk said:


> I would still be up for another round of carrie boards....


 
  I would suggest you volunteer.
   
  Contact Joneeboi and see if he'll supply you with the Gerbers.  Send them to Imagineering for a quote, divide by the number of boards to determine the per-board-price, add-in your packaging costs (you'll need to buy a bunch of padded envelopes), shipping costs (you'll need to estimate or set a single standard price) and Paypal fees, setup up a database/spreadsheet to save the names, addresses and whether they've paid, decide on the time period then contact Jude for permission, and announce that the Group Buy is open.
   
  Good luck.


----------



## Billyk

Thanks TomB!
  I did just that, let's see what happens.
  Billy


----------



## andart

Hi all.
  Sorry fo my google translate.
   
  I have grubDAC. It works perfectly. 
   
  I need Carry USB Hedamp. Where i can order kit ?
   
  Thx.


----------



## tomb

Quote: 





andart said:


> Hi all.
> Sorry fo my google translate.
> 
> I have grubDAC. It works perfectly.
> ...


 
  I'm sorry, but Joneeboi was the designer and source of PCB's for the Carrie.  He's the only one that has access to the Gerber files needed to produce the PCB (as far as I know).  If Billyk has not had any results (see the posts above), then you may just be out of luck.


----------



## Billyk

Having no other way to reach him other than a PM here on head-fi, I have been unable to contact him. I have not given up hope just yet though! So stay tuned and I will continue to try to contact him. He still would need to grant permission and share the gerbers...


----------



## tomb

Quote: 





billyk said:


> Having no other way to reach him other than a PM here on head-fi, I have been unable to contact him. I have not given up hope just yet though! So stay tuned and I will continue to try to contact him. He still would need to grant permission and share the gerbers...


 
  YGPM - additional contact info for joneeboi ...


----------



## onyu

Another Carrie more or less lives...
  
 After a few years I've finally decided to finish my Carrie.
 But I have a problem with it: One channel of it is completely dead. 
  
 I have no idea what could be wrong with it.
  
 The dac is fine, both channels play fine.


----------



## tomb

Never mind - yeah, it should've worked that way.


----------



## tomb

OK, I'm confused about where that grey wire is going ... but you appear to have the earliest version of the Carrie, not the latest.  So, I'll shut up and see if someone else can figure it out.


----------



## onyu

Thank you for looking tomb.
  
 After looking close to it I found 2 not so good looking solder joints.
  
 One bad joint on the left blue resistor and on the 3rd yellow cap. 
  
 Did them again and now it is playing well. 
  
 Nice little amp.


----------



## tomb

onyu said:


> Thank you for looking tomb.
> 
> After looking close to it I found 2 not so good looking solder joints.
> 
> ...


 

 Well, glad you got it figured out!  Yeah, once I realized it was the early version - I have no documentation on that one, so I shut up.  It's good that you didn't give up.


----------



## TBomb06

Well, after 3.5 years, my Carrie + Grub DAC combo seems to have given up the ghost  I was noticing some distortion as volume increased, and the power LED for the Carrie amp would come on when I turned it on but fade off within a few seconds, so I opened it up to take a look. I noticed that if I touched certain areas on the bottom of the PCB (where the through-hole leads were soldered), particularly around the potentiometer and DC/DC converter, I could get the distortion to stop and the sound quality to improve, and the LED would light back up. I figured that the DC/DC converter was shot, so I ordered a new one and changed it out. It didn't help, and the new converter is getting really hot for some reason. I've checked to make sure I'm getting 5V DC incoming power (I am), and I checked to make sure I have the proper DC/DC converter (15V) with the corresponding voltage regulator (12V), which is right. I'm all out of ideas here. I hate to think about tossing it since it was a great little combo, and I'm not sure there's anything on the market to fill that niche without spending a lot of money. Anyone have any ideas as to what might have happened?


----------



## KimLaroux

TBomb06, the first thing that comes to mind is a cold solder joint. I'd try reflowing stuff around the sensitive area, going as far as reflowing the whole board.
  
  
 Today I finally got around to beginning this project. I had never soldered SMDs before so I started with assembling the DAC. That way if I broke or lost something I would order it with the parts for the amp.
  
 Turns out it was a lot easier than I feared. With the fine tip of my iron I was able to solder the ICs pin by pin, which was a nice surprise. I expected the board to take a few days to assemble but I did it in a few hours. Quite a fun project, so far.
  
 I haven't powered it yet since I washed it with flux cleaner. I'll wait for tomorrow to make sure everything is dry. Fingers crossed.
  
 Crappy cellphone pictures:
  
 
  
 Now, reading the BOM I see we are given the choice between a 12v rail and a 10v one. I figure the advantage of the 10 V is more current, but I can't really see the advantage of more voltage. On what factors should I make my decision?


----------



## TBomb06

kimlaroux said:


> TBomb06, the first thing that comes to mind is a cold solder joint. I'd try reflowing stuff around the sensitive area, going as far as reflowing the whole board.


 
  
 Yeah, I reflowed everything around there, but not the whole board yet. I might give that a shot and see what happens.


----------



## KimLaroux

Hi guys.
  
 So I spent the day going trough the BOM, trying to find everything I need from a single supplier.
  
 The BOM lists a part # for the output jack for Digikey only : http://www.digikey.com/product-detail/en/SJ1-3533NG/CP1-3533NG-ND/738701
  
 Searching on Mouser, I found a part that I believe would fit on the board nicely. The measurements are not perfect, but it's close enough that it would fit with some hacking, at the worst. Can anyone give me a second opinion on this, in case I am missing something? Here's the part I found : http://ca.mouser.com/ProductDetail/Kycon/STX-3150-3C/?qs=sGAEpiMZZMv0W4pxf2HiV3p8sCuGBLyboz2QM3ee%2fdo%3d


----------



## KimLaroux

Well, I went ahead and ordered everything from Mouser, including the jack I found. For anyone interested, here's my BOM : http://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=02dba010a7
  
 It includes the 12V converter and 10V regulator, along with resistors for gains of 2 and 3. I also selected a non-switching volume pot to have more control. It's not exactly the same parts as in the official BOM as some parts were out of life and some back order. I found replacements.
  
 The official BOM lists no part # for U4 at mouser, but it is included in my BOM. They started stocking this chip recently. With this, I was able to avoid placing a second order at Digikey and order everything from Mouser.
  
 Getting excited to get this little guy running.


----------



## DingoSmuggler

kimlaroux said:


> Now, reading the BOM I see we are given the choice between a 12v rail and a 10v one. I figure the advantage of the 10 V is more current, but I can't really see the advantage of more voltage. On what factors should I make my decision?


 
 12V will give more volt swing at the cost of slightly higher power use. I'd say it's only about 3dB headroom either way.
 So, for headphones under 100 ohm go 10V, headphones over 100 ohm go 12V if you think you would like to, or need to, maximize headroom.
  
 As for the jacks, the mouser one does look close enough to me too. With round holes and flat pins, that 0.15mm difference front-to-back should be fine. Flat pins won't bent side to side, but the hole spacing is spot on in that direction.


----------



## KimLaroux

I received my Mouser order and the first thing I checked was if the jack fitted. It fits in perfectly without bending anything. In fact the holes are so large in the PCB the jack fit loosely in with place to move around.
  
 So with that and the fact Mouser started stocking U4, it's now possible to order the whole BOM from Mouser.


----------



## KimLaroux

Still untested, as my computer can't host the GrubDAC. Is it safe, for testing purposes, to power it from the 5 V rail of an ATX PSU, and sending it audio signal from my desktop DAC?


----------



## Robin W.

Have you guys been able to contact joneeboi yet?
 I saw him a few weeks ago and I'd be happy to pass along a message or point him to this thread.  
 He's been very busy with life but mentioned that he'd like to get back into this if/when time permits.


----------



## tomb

kimlaroux said:


> Still untested, as my computer can't host the GrubDAC. Is it safe, for testing purposes, to power it from the 5 V rail of an ATX PSU, and sending it audio signal from my desktop DAC?


 

 Very nice work, Kim!  It's great to see that PCB being put to use!
  
 I wish the news was better on the GrubDAC.  I'm afraid you are unique in that regard - haven't had any other reports of incompatibility.  I forget the specific issue - do you think one of our new DoodleBugs could correct the problem?


----------



## KimLaroux

tomb said:


> Very nice work, Kim!  It's great to see that PCB being put to use!
> 
> I wish the news was better on the GrubDAC.  I'm afraid you are unique in that regard - haven't had any other reports of incompatibility.  I forget the specific issue - do you think one of our new DoodleBugs could correct the problem?


 
  
 Thank you for the kind words and for giving me the opportunity to tackle this project. 
  
 I can't tell if the DoodleBug would help, as the problem seems to be with my computer. Fooling around with other USB devices, I was able to reproduce the problem, though not permanently as with the GrubDAC. 
  
 I have noticed an improvement when using a short usb cable, containing a ferrite, soldered directly to the board. My goal is to assemble the unit and encase it, then try a very short, high quality USB cable containing at least one ferrite bead. I got my fingers crossed on that one.


----------



## Avro_Arrow

kimlaroux said:


> I can't tell if the DoodleBug would help,


 
  
 Can you measure the voltage at the DAC when plugged into the laptop?
 I might be able to loan you my Doodlebug to test with...


----------



## KimLaroux

avro_arrow said:


> Can you measure the voltage at the DAC when plugged into the laptop?
> I might be able to loan you my Doodlebug to test with...


 
  
 Can you be more specific? Where/what do you want me to measure?


----------



## Avro_Arrow

kimlaroux said:


> Can you be more specific? Where/what do you want me to measure?


 

 On the GrubDAC, measure between the 0V and 5V where the USB Cable would be soldered.
 If the voltage comes out less than 4.75, the malfunction could be voltage related.


----------



## KimLaroux

avro_arrow said:


> On the GrubDAC, measure between the 0V and 5V where the USB Cable would be soldered.
> If the voltage comes out less than 4.75, the malfunction could be voltage related.


 
  
 I get 5.03 V at this point. The 3.3 V rail shows acceptable voltages too. I'm pretty confident the problem is with my laptop having lame USB ports, as the DAC works fine on my friend's Alienware.
  
 I finally got around to test the Carrie itself and of course it doesn't work. I only get 2 V between V+ and V-. 
  
 The DCP gets 5V fine, but measuring on the output pins yields nothing. Of course being a switching supply, I really have no clue how to debug it. Any idea where I should start?
  
 edit:

 Silly me tested the wrong pins, confused as to how to count them with the lack of some pins on the IC. I measure 2.12 V directly on the output of the DCP. It's 1.96 V between V+ and V-.


----------



## Avro_Arrow

The DCP is a pretty simple device.
 It takes your 5 volt input and should give you + and - 12 volts out.
 The important pins are all on the outside edge on the carrie.
  
 Pin 1 and 2 are the USB power with 1 being +5 volts and 2 being USB ground.
  
 Pins 5, 6 and 7 are the output voltages and are isolated from the input side.
 Pin 5 is the amplifier ground, pin 6 is +12 volts and pin 7 is -12 volts.
  
 When testing voltages, remember to reference to the correct ground.
  
 If you are not getting the correct output voltages, check for shorts
 in the voltage rails.


----------



## Avro_Arrow

I was just looking over the schematics and BOM for the Carrie.
 It has some odd component choices.
  
 The BOM specifies a dual rail version of the DCP01 even
 though it only uses one of the output voltages.
 A single rail DCP01 would have seemed to be a better choice...
  
 If using a dual rail DCP01, it would seem to me to be a better
 design to get rid of the TLE and extra op amp for the rail splitter
 and just have a proper dual rail supply.
  
 This is not aimed at anyone, I'm just rambling...
  
 Edit: Oh, and lastly, it uses an 8 volt regulator giving +- 4 volt rails.
 The op amps like 5 volt rails...
 Why not a 10 volt reg or at least a 9 volt reg?


----------



## KimLaroux

avro_arrow said:


> I was just looking over the schematics and BOM for the Carrie.
> It has some odd component choices.
> 
> The BOM specifies a dual rail version of the DCP01 even
> ...


 
  
 Avro, what BOM are you looking at? Are you sure it's version 2.01?
  
 I got the DCP010512BP, which is a single rail converter. The dual rail has model number DCP010512DBP. (it's in the datasheet)
  
 I also got a TL750L10 that gives me a +-5 V supply for the op-amps.


----------



## Avro_Arrow

I was looking at the BOM here, mouser BOM
  
  
 Your right...DBP is the dual rail version, BP is the single rail.
  
 Disregard any reference to pin 7.
  
 You should be getting 12 volts between pins 5 and 6.
  
 Your component choices are correct.


----------



## Avro_Arrow

I just check the BOMs.

  
 The Mouser BOM and the .xls BOM are different.
  
 Don't mind me...


----------



## joneeboi

Not your fault, Avro. That one's on me.


----------



## patchoncas

First time on Head-fi, because I can't seem to find this information anywhere.
  
 Does anyone know where can I get one (possibly more) Carrie v2 boards? I have a AMB Mini3, and this Carrie amp interests me greatly!
 I read through the whole thread, so my hopes are low (really low), but if someone has one and whishes to be charitable, I'm sure we can get along 
  
 Thanks anyway!


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## Avro_Arrow

patchoncas said:


> First time on Head-fi, because I can't seem to find this information anywhere.
> 
> 
> Does anyone know where can I get one (possibly more) Carrie v2 boards? I have a AMB Mini3, and this Carrie amp interests me greatly!
> ...


 

 If you have some patients, there should be a new version coming out.
 Like many of use who like to design things, Joneeboi's free time is in
 short supply.


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## joneeboi

Hey folks,
  
 As Avro mentioned, I am indeed kinda busy. Marriage and work and vacation taking up my time in the last few months, but as the dust has started to settle, I want to move forward with the design. First step is actually getting the PCBs, but I want to double check that my design makes sense. I let my obsessive side take over previously, and now I need to just get it moving. I'm almost never on head-fi to browse, but I do get email notifications on PMs. Trying to at least stumble toward the finish line, but this water break has lasted long enough.


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## KimLaroux

So... after a long break, I finally got around to debugging my Carrie.
  
 I took the TL750L10 off the pcb to test it on a bread board. With an input voltage of 14.7 V and an output current of 30 mA, the output voltage reads 13 V. Does this mean the regulator is dead?
  
 I've never experienced such a behavior from an LDO.
  
 Either way if current is flowing trough it, I don't see why my Carrie is not operational. I'll try resoldering the LDO in and do more tests on the circuit. I wish I had spares to compare... This IC is one of the few I didn't get a spare of. Silly me.


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## KimLaroux

The LDO back in, I get 1.87 V on its input and 1.84 V on its output. I'm guessing there's a short somewhere but being mostly a trough-hole board I have no idea where to look. Not to mention the LDO doesn't get hot... Maybe it detects a short and shuts down, but then why is the input 1.87V?!?


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## joneeboi

What's the DCP's output reading?


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## KimLaroux

joneeboi said:


> What's the DCP's output reading?


 
  
 2V, like the input of the LDO. I tried removing the LDO and the DCP did output enough voltage, around 14V if I remember right. It just falls for 2V when I put the LDO in.


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## KimLaroux

I got a new desktop computer running Windows 7 so I'm giving this another try...

If I plug my GrubDAC alone in the USB port, without the carrie, it's recognized and I guess works fine. (I don't have plugs connected to its audio output so I cant test it)

I think the problem is with the Carrie. Here's why I think so:

I added a power switch between the carrie and the dac. When I plug the DAC in with the switch open, the DAC is recognized:

 1460.483019] usb 6-2: new full-speed USB device number 52 using uhci_hcd
[ 1460.669007] usb 6-2: New USB device found, idVendor=08bb, idProduct=2707
[ 1460.669011] usb 6-2: New USB device strings: Mfr=1, Product=2, SerialNumber=0
[ 1460.669014] usb 6-2: Product: USB Audio DAC 
[ 1460.669017] usb 6-2: Manufacturer: Burr-Brown from TI 
[ 1460.701071] input: Burr-Brown from TI USB Audio DAC as /devices/pci0000:00/0000:00:1d.0/usb6/6-2/6-2:1.2/input/input19
[ 1460.701346] hid-generic 0003:08BB:2707.0009: input,hidraw5: USB HID v1.00 Device [Burr-Brown from TI USB Audio DAC ] on usb-0000:00:1d.0-2/input2

But the moment I close the switch to power the carrie...

[ 1528.953037] hub 6-0:1.0: port 2 disabled by hub (EMI?), re-enabling...
[ 1528.953045] usb 6-2: USB disconnect, device number 52
[ 1531.042021] hub 6-0:1.0: connect-debounce failed, port 2 disabled
[ 1533.246020] hub 6-0:1.0: connect-debounce failed, port 2 disabled

I'm thinking my Carrie+GrubDAC combo is pulling too much power off the usb port. I tried bypassing the switch using my DMM and it tells me the carrie is pulling 40 mA. I'm having a hard time believing this, after reading the math behind this whole project. How much current should I expect my carrie to draw?


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## Avro_Arrow

It might not be the idle current that is the problem, it's probably the start up surge.
 Try powering the grub and th Carrie off different ports.


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## KimLaroux

And with the huge capacitor banks on the carrie, it's to be expected. I'll try powering the carrie straight off an ATX PSU. This should answer the question.


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## KimLaroux

Meh. Very meh.
  
 I thought for a moment the problem could be the capacitor bank being too big, but even directly powered from an ATX PSU all I get out of the DCP - and the LDO - is 2.7 V.
  
 I removed the LDO and the DCP outputs 24V. I'm hoping it's just the LDO that is blown, so I'll order a couple of spare ones and see.
  
 But this time I'm soldering socket pins into the LDO PCB holes. I'm done with desoldering and resoldering this part.


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## KimLaroux

Anyone has got one or two TL750L10CLPR to spare? I don't feel like paying 20$ of shipping for a 0.82$ part. =/


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## KimLaroux

Ok I give up. Plan B: Is it safe to replace the 750L10 with a 78L10? The later has a current capability of 100 mA compared to 150 mA for the 750L10. I searched the thread but can't find a consensus on how much current the Carrie draws.


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## Avro_Arrow

Give it a try and I'll cross my fingers for you.


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## KimLaroux

avro_arrow said:


> Give it a try and I'll cross my fingers for you.


 
  
 Lol. If you see a big mushroom cloud East of your place, and that I never report back, you'll know the experiment will have failed. 
  
 No but seriously. If I don't get more data on the specifications of the Carrie I won't fool around and order the 750L10. It's just twice the price.


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## Avro_Arrow

kimlaroux said:


> Lol. If you see a big mushroom cloud East of your place, and that I never report back, you'll know the experiment will have failed.
> 
> 
> 
> No but seriously. If I don't get more data on the specifications of the Carrie I won't fool around and order the 750L10. It's just twice the price.


 

 Other than having to charge up that big a55 cap bank, it's just a three channel CMoy.
 I think the 100mA should at least get it running. Just add up the quiescent current
 for the three channels and add in how much current you think you may draw under load.


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## KimLaroux

avro_arrow said:


> Other than having to charge up that big a55 cap bank, it's just a three channel CMoy.
> I think the 100mA should at least get it running. Just add up the quiescent current
> for the three channels and add in how much current you think you may draw under load.


 
  
 Ok noob questions: How do I calculate the quiescent currents and the current of the load?
  
 I'm guessing if I can find the output RMS voltage at normal volume, and the impedance of the headphone, I can calculate the load current. But how do I find the RMS output voltage?
  
 I'm clueless how to find the quiescent current of the Carrie.


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## Avro_Arrow

You can use the sensitivity rating on your headphones to guess-timate the voltage required to drive them to a reasonable
 level and use their impedance to figure out the rough current.
 You can get the quiescent current for the op amps from the data sheets.


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## KimLaroux

avro_arrow said:


> You can use the sensitivity rating on your headphones to guess-timate the voltage required to drive them to a reasonable
> level and use their impedance to figure out the rough current.
> You can get the quiescent current for the op amps from the data sheets.


 
  
 OK I'll go digging trough some data sheets tomorrow.
  
 If there's no way to have more than a guess-timate on how much current my headphones draw, I'll just take my amp meter out and test them. That should work, right?


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## MisterX

Comparing this---->
 Quote:


>


 
 To this--------->
  
  
  
  
  
  
  
 And the datasheet for the Tantalum Capacitors installed in the C1 positions
  
 (http://www.mouser.com/ds/2/212/F3100_TaDipRad-507115.pdf)
  
 Screen cap---------->
  

  
  
 I'm wondering if they are still installed backwards.
  
 The idle current for a Mini3 should be 24mA.


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## KimLaroux

Holy smokes! I never realized those capacitors had a polarity! Nice find! I'll switch them the right side tomorrow. Thanks a lot! 

Hopefully my ldo is not fried and will still work after that...


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## MisterX

I'd be more worried about the capacitors then the regulators but they're over-spec'd enough that they should be OK.
 (it's not uncommon for damaged tantalum capacitors to explode when they fail)


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## KimLaroux

Alright so I reversed the caps, but I still only get 1.9 V out of the LDO. What's more, I only get 1.9 V at the input of the LDO. I'm guessing it's shorted and pulls the DCP into over current protection. Pulling the LDO out and the DCP outputs 24 V.
  
 Interesting to note is the polarity of those capacitor is not marked on my PCB. The print is simply not there.


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## MisterX

A vacant U2.... sounds like a good time for a sanity check.
 Measure the resistance between the output pad (the pad closest to the front of the PCB) of U2 and ground.
 What's the reading?
 (should be in the high K ohm range and will wiggle around as the caps do their thing)


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## KimLaroux

misterx said:


> A vacant U2.... sounds like a good time for a sanity check.
> Measure the resistance between the output pad (the pad closest to the front of the PCB) of U2 and ground.
> What's the reading?
> (should be in the high K ohm range and will wiggle around as the caps do their thing)


 
  
 Moves around 2 K ohms. 
  
 I measured just about everything I could think of but didn't find any short.


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## joneeboi

Any chance for high res shots of the bottom side of the board? All that resoldering can't be good for those traces. From your previous posts, sounds like the TL750 and DCP are both working fine independently of each other.
  
 When I put in a tantalum caps backwards, it went up in flames; it went up because I was surprised and threw it in the air. I wonder if yours are shot and need replacing.


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## KimLaroux

joneeboi said:


> Any chance for high res shots of the bottom side of the board? All that resoldering can't be good for those traces. From your previous posts, sounds like the TL750 and DCP are both working fine independently of each other.
> 
> When I put in a tantalum caps backwards, it went up in flames; it went up because I was surprised and threw it in the air. I wonder if yours are shot and need replacing.


 
  
 Nothing happened to my caps when I first powered the amplifier up. I doubt 1.9 V is enough to kill them... but anyways. You think I should try to power the board without the caps in, see what happens?
  
 I'll take my scanner out and scan the bottom of the board. Pictures later today.


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## joneeboi

I was thinking more of the reverse polarity damaging the caps, but taking them out wouldn't be a bad idea to experiment.


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## KimLaroux

So my scanner proved to be unable to take pictures of PCBs, so I went on and bought a DSLR. Here's what I could do with it. You can download the originals and zoom in all you want.


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