[beauistheman]

hey, new to the forums and ive done some searching

i completed my first audio diy project as the typical cmoy amp, but modded it to use both battery and 24vdc. Now im interested in more. I wanna build a USB DAC and then maybe a millett starving student amp. Im starting to get right into it haha.

Question i have, what is a good project for me in terms of the DAC?? And living in AUS whats a good place to buy specifics like the PCB? Also where can i find some breif instructions on building it too. Im good with the iron, but i take a while understanding schematics properly. Im not the best with them. I read the Millett schematic and i seem to understand that one easy enough.

also im currently in japan atm (tokyo, 25min bike ride from akihabara haha) and if theres any parts i should definitely buy here such as enclosures and maybe the tubes, let me know what is best to get here, prices are awesome!

Anyway, any help will be greatly appreciated.

cheers

 

[ltmon]

In AU you can't (as far as I'm aware) locally get the PCBs for any well known DACs. The two easiest to build USB ones are the Alien and Bantam. There was a Bantam group buy thread for Australia recently, so have a search for that. Other than that postage of an Alien doesn't cost that much, it's a lightweight kit.

I built the Alien as a first project after the Starving Student, and it's pretty easy once you get the hang of surface mount soldering. The instructions are here: Alien DAC - Overview and kits can be bought from Glassjar Audio.

In Japan, I would (personally) look for Alps RK27 pots and nice looking enclosures. These are two items I find are always way overpriced in Australia, although the pots are easy enough to have delivered cheaply. Possibly a nice volume knob or two as well.

 

[beauistheman]

hey mate, thanks for the reply, cool the alien looks good to me. Ill keep looking for some cool enclosures cause they are insanely cheap. Are those Tubes mentioned in the starving student amp the only ones you can use for it? are theyre any other options? Cause ill check the price of em here

 

[ltmon]

The Starving Student hasn't been redesigned for alternative tubes as far as I know. If you can get 19J6 tubes in Japan and want to build a SS, buy them as they're a little difficult to find at the moment.

 

[beauistheman]

yeah i noticed that i couldnt buy em anywhere lol. Ill check around for them and a suitable enclosure. Also, is it better to use some sort of PCB for that amp? just for structural purposes, or its fine to stick with point to point work?

 

[-=Germania=-]

The starving student may be redesigned to work with the 6J6 family (The 6j6 is a lesser tube - but opens you up to a large variety of tubes with maybe more potential) 6J6, Tube 6J6; Röhre 6J6 (6J6)

You would need a higher current PS (1.2A) with a voltage of about 15V (popular, 12V would a little too low) as opposed to 40V+ and low current (0.35A).

You would need to change some part values and different mosfets, but hat wouldn't be too hard I imagine. It was something I was looking into - but another project has taken its place and all money must go to that.

 

[dsavitsk]

Quote:

Originally Posted by -=Germania=- /img/forum/go_quote.gif The starving student may be redesigned to work with the 6J6 family

No it can't, at least it can't as you described. The characteristic of the 19J6 that make it work here is the heater. A 6J6 with a 15V supply will have ~7V on the plate and a bias of just a few mV which would make it a distortion generator. It also won't be able to push the mosfet.

Quote:

Originally Posted by -=Germania=- /img/forum/go_quote.gif The 6j6 is a lesser tube

I have no idea what that means. It's the same tube with a different heater.

There are a bunch of tubes that one could design a starving student-esque amp around, but for now I'll leave that as an exercise for the reader

 

[beauistheman]

got where could i find some info about modding that amp to accept higher current lower voltage?

 

[dsavitsk]

Tubes are, with a few exceptions, high voltage devices. For this purpose, you are looking for a triode (or a pentode that will work well as a triode) with a highish voltage heater (12.6V or higher probably) that has relatively low current (150mA or less) and with mu in the 20 to 40 range. If you require a low voltage supply, you also want it to bias to at least -1V on the grid with 20V or less on the plate all while keeping rp lower than 10K at the highest -- lower is better.

 

[ltmon]

If you're still looking for 19J6 when you get back to Australia, PM me as I have 2 spare here in Melbourne.

If your electronics-foo is up to it though, I'd love to see a redesign with more common tubes.

 

[jar]

AMB's gamma1 is IMHO the best first DAC project. It sounds much better than the Alien. I built one of the prototypes, and AMB just released the PCBs today. Unfortunately you just missed the group buy on case panels.

 

[joneeboi]

Best first DAC? It has multiple SMD chips to solder with its different configurations making it a bit more confusing while having more components than both the Alien and Bantam combined. It may be a great DAC and engineering feat, but I wouldn't say its a great first DAC project, especially when he's saying that reading schematics are his weak point. Both the Alien and Bantam are great for straightforward DAC projects, but the Alien would be preferred because of Jeff's great kits. I know AMB has always done a stellar job of supporting the build threads by answering questions and clarifying simple things for us simpletons, but the Alien has been around longer, has more builders from whom he can ask questions, and has an already well-documented build thread that he can search through for known issues with the project. The AlienDAC is a better bet for a first-time DAC project for because of its simplicity, availability, and troubleshooting support.

 

[jar]

I suppose my opinion is based too heavily on my own prejudices. I find casework far more difficult and frustrating than soldering, so the fact that everything in the gamma1 is PCB mounted and that the custom panels are available makes it an easier build for me. Also, I feel like the Alien (haven't heard a bantam) just isn't good enough to be worth the effort.

AMB's documentation is generally the best I've seen for any project. Tangent's stuff is similar and every other project I've looked at is WAY below those two. When I looked at the Alien (admittedly, that was a year or two ago), the documentation was pretty weak.

I guess I was thinking of first DAC in the context of a little more amp building experience. If I were the OP, I'd get a bit further into amps before heading down the DAC path. I think either a Millet Hybrid (though I'm not up on the current state of PCB availability) or a Mini^3 would be a great next step after a CMOY.

 

[beauistheman]

yeah well im thinking about a millett hybrid, it seems not too costly and like a decent amp that i will actually use too. A DAC isnt the most important thing to me at the moment, but maybe ill see how i go with the millett. Im not worried with casework, the schematics are my weak point, if anything the case work is my strongest, so if there are PCBs avail for alien or even the other one that was suggested, that would make it even eaiser for me, along with decent build threads and plentiful information. Tangent has a good amount of info for building the cmoy which was very helpful to me. Anything that has info like that would be the eaisest haha but thats being very childish hey

 

[joneeboi]

It seems I spoke a little too soon, or at least spoke falsely about the gamma1's ease of build. The pitch on the gamma's PCM2707 is huge compared to the PCM2702's. I personally have unsuccessfully built three PCM2702-based DACs because I overheated the chips trying to fix the bridging. Now I think that the gamma1 would be much easier to build than I originally thought. My bad.