Interest check: portable DAC + headphone amp
May 23, 2002 at 10:13 PM Thread Starter Post #1 of 33

aos

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Well, since a few people were interested in getting a portable DAC, I investigated the price point by looking at volume discounts for parts etc. While I did find a way to cut some of the costs drastically, unfortunately many critical parts are just plain expensive and price breaks don't apply until you buy 1000+ (such as the DAC chip - $18 US is what Analog asks and you have to live with it).

If I decide to go ahead I assume the price would be between $200 and $250 US, depending on actual prices for the parts and PCB. I was never under any illusions that I could sell more than, say, 10, and I'd be surprised if even that much are sold, but I thought I might as well ask... The price is mostly cost of parts and that's very unfortunate.

Of course, this would be contingent on sending one of those to a few regulars here or to one of the meets for evaluation and receiving favorable reviews. The unit contains DAC and headphone amp which is basically the same topology as META42 (not surprising, we all used the same ideas). Sound quality would have to be right for the price; if we decide it isn't, it doesn't make any sense to make them.

This is just interest check of course, no any kind of obligations for either you or me...
 
May 23, 2002 at 10:36 PM Post #3 of 33

aos

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No, the unit has optical in only, not the coax. So you can use Sony CDPs. I had one prototype with both optical and coax but that was a pain to use.
 
May 23, 2002 at 11:41 PM Post #6 of 33

aos

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Just to clarify, headphone amp and line out are one the same here. It is not the case of extra headphone amp tacked on the DAC but more of a volume control added to the line out. It is not your typical line out or headphone out though - we know that most portable equipment has clean but very low power line outs and mostly inadequate headphone outs. Not so here, line out is powerful enough to drive headphones or cables (previous prototypes used ADSL driver chip capable of driving 5km of cable
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) yet it's sound quality is not compromised by sacrificing power for battery life and battery voltage. You need to buffer almost all DAC chips anyway so why not make that buffering section powerful?

Simply said, you're getting headphone amp as bonus, for the price of extra jack, pot and few resistors/caps so there is very little price hit for that ($10 or so). Extra bonus is that there are no wires or cables anywhere between DAC and headphone plug.
 
May 24, 2002 at 3:04 AM Post #8 of 33

coolvij

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I think it's a great idea......
 
May 24, 2002 at 3:36 AM Post #9 of 33

daycart1

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I'm interested, but that is about my price limit. I wouldn't like someone's labor to be undervalued (I'm serious).
 
May 24, 2002 at 7:49 AM Post #10 of 33

zbuddah

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I'm in atleast by the end of the summer, once I pay off some stuff and save a little.

and yes once the favorable reviews/comparisions hit the board and a little more info.
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May 24, 2002 at 6:02 PM Post #11 of 33

Audio-Me

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I'm interested, but which good pcdps have linear antiskip with digital out? (anyone want to sell a japanese model pana570?) I'll have a custom META42 soon, and I'd be glad to review the PDAC in comparison with a decked out meta42 for you.
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This is all in the future of course. (in 6-12months)
 
May 24, 2002 at 6:20 PM Post #12 of 33

kelly

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I'm definitely interested assuming this isn't a crippled version of the prototype. I'm willing to pay a little extra if need be to use quality parts. In fact, it would be nice if you offered some options in the way of headphone jacks and the like. (ie, I'm a fan of the Neutrik jacks that most people couldn't justify the expense of.) I'd also like to see it in a metal enclosure which might add another $20 to the cost.
 
May 24, 2002 at 7:11 PM Post #13 of 33

aos

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Yeah, the price sucks, I know. Compared to Art DI/O, parts cost more than that thing retails for! Unfortunately, AD8610 and AD1866 are not 30-cents parts. That's why I was very reluctant to even consider just *investigating* the possiblity of making/selling the PDAC. Hopefully that difference in price of parts should be audible and justifiable, that's what will be determined with reviews. I know they satisfied my requirements, which was my design goal, but I don't have any commercial amps to stack it against.

Parts to be used are the same that I used myself - the ones I care about are the best or among the best you can get (polymer capacitors, AD8610, EL2001, BUF634), while the others are standard or high(er) quality parts (Vishay-Dale resistors, Panasonic FC capacitors etc.).

As for case, pots and jacks, I'm mostly constrained since the board was designed to use board-mount parts, and to fit a particular enclosure. I have seen some very nice anodized cases from Hammond for just a couple of bucks more, and it would be nice if they'd fit. I can also get Neutrik locking jacks, and they don't cost that much - only $6 canadian or so in a retail store - but they are very large - 1/4" plus the flanges or whatever you call it - and very long, and do not fit well in small case. I don't know if Neutrik makes 1/8" jacks, I'd be interested to see/get them if they do. I'm using Panasonic pots from Digikey since they're small, PCB mount, and fit well, and the choice for small pots is almost non-existent. Jacks I used are nothing special, from Digikey, although the output one is gold plated.

As for PCDPs that can be used, well, I'm a terrible salesman since I am always honest about what's bad about my stuff. There are problems with Sony PCDPs when G protection is on. Older models cannot turn it off by a button as it is automatic - it turns off when AC powered and then the sound is fine. It is also possible to trick them by plugging external battery in the AC jack but not using the two-part jack that comes with it, as that's what trigger G-prot. - this was discussed in portable forums several times. So if you do that, or use model with the switch and turn it off, the sound is fine. I personally was never able to hear differences between different digital sources, regardless of source or cables, and I certainly couldn't find any difference from using PCDP as a transport as opposed to a stand-alone CDP. Also, receiver chip is brand new design with 3x less jitter than older stuff you're likely to run into, making source even more irrelevant. It works from SB Audigy, from different DVD and CD players - even in 24/96 mode. As to the G prot problem, whether problem is in the receiver chip I use, or in my design, or actually in Sony's signal with G-prot on - and all three things are possible although the third was most likely from my limited investigation - the thing is that you can't use PDAC in such mode, there will be too much popping in the right channel. You could hook up line out and use headphone amp only of course.
 
May 24, 2002 at 7:37 PM Post #14 of 33

kelly

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AOS

The jacks isn't a dealbreaker but I had to make a push for them. How big is the PDAC? The absolute ideal for me would be something that is roughly the same dimensions as the Cosmic. Actually I'd be quite happy just buying a Cosmic... if it included a DAC.
smily_headphones1.gif
 
May 24, 2002 at 9:29 PM Post #15 of 33

aos

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PCB was designed around Hammond 1598ASGY.

Dimensions of that case in imperial are 6.1 x 3.6 x 1.4

I think jacks are more of liability in mechanical sense, i.e. frequent and forceful use would probably break the cheap ones. How these ones fare if abused I don't know...
 

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