Over my head?
First post cheers to everyone out there!
Trying to judge if I would be crazy for trying this as my first amp build... I skimmed the directions and BOM; nothing looked impossible.
I was really thinking of building just the plain O2, but after reading agdr's suggestions on updated parts and mods for the O2, I figured I might as well just jump in the deep end here. I also have no intention of making a portable amp with batteries, and I don't know if I can stand all that wasted board space on the O2 with no batteries.
Main reasons to build the ODA
1) Power HifiMan HE-400
2) Pre-amp to powered monitors
3) The engineer in me just wants to build and test stuff
So, should I build just regular O2 or go big and try this version of the ODA? Has anyone out there done this as their first amp build?
First post cheers to everyone out there!
Trying to judge if I would be crazy for trying this as my first amp build... I skimmed the directions and BOM; nothing looked impossible.
I was really thinking of building just the plain O2, but after reading agdr's suggestions on updated parts and mods for the O2, I figured I might as well just jump in the deep end here. I also have no intention of making a portable amp with batteries, and I don't know if I can stand all that wasted board space on the O2 with no batteries.
Main reasons to build the ODA
1) Power HifiMan HE-400
2) Pre-amp to powered monitors
3) The engineer in me just wants to build and test stuff
So, should I build just regular O2 or go big and try this version of the ODA? Has anyone out there done this as their first amp build?
Welcome to the forum! 🙂
The spreadsheet below shows that your HE400s would need 4.4Vrms and 127mA to hit 120dB sound pressure level on musical peaks. The O2 actually can do both of those just fine while running on AC (but not on batteries, the output voltage level drops). Being all through-hole NwAvGuy's O2 is certainly the easiest build. Like Chiroshi says you can drop one of NwAvGuy's ODACs where the batteries would normally go to give you a full DAC+amp.
If you want to build any of my stuff you could add an O2 booster board:
http://www.diyaudio.com/forums/headphone-systems/244473-o2-headamp-output-booster-pcb.html
which goes in the top slot and plugs into the O2 PC board in place of the two NJM4556A output chips. The booster board adds a headphone relay to eliminate thumps, gives you around 50microvolts of DC output vs. 3600 or so for the stock O2, two cool green LEDs 😀 to tell you when your mosfets are on and if one power rail isn't working, power rail clamp diodes, and of course larger output buffer chips (LME49600) for up to 2x the current on musical peaks of the stock O2. The sustained average current is the same though for heat dissipation reasons.
All the DIY materials for the booster board are at the Google Drive link in the first post on that thread. I have bare PC boards, but the Gerber files are in that link so folks can fab their own too.
One thing though - the O2 Booster Board and ODA have a large number of surface mount parts that have to be soldered on. They are all the larger "1206" sized stuff. How much soldering have you done and have you surface mount soldered before? That will affect the recommendation! 🙂
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I have experience soldering but never any surface mount and haven't had the need to solder anything since college, so it has been a while. I did a good bit of digital circuit design in college but nothing as complicated as this. And for the life of me, I can't recall ever constructing a circuit that took analog inputs lol.
4x4F150 - there would be a bit of a learning curve but you should be able to get the hang of the surface mount stuff pretty fast. The four things I consider essential for surface mount soldering are: a circuit board vise like a panavise 350 to hold the board; right angle tweezers to hold the parts by the sides; a temperature controlled soldering iron with grounded tip; and an anti-static mat with wrist strap.
Once you have all that stuff it is just a matter of putting some solder on one of the two PC board pads for any two terminal device, like a resistor or capacitor. Then grab the part by the sides with the tweezers, reheat that solder on the pad, then stuff one end of the part in, while getting the other end of the part centered on the other PC board pad. 🙂 Not uncommon to have to reheat that end a few times to move the part around. Then just solder up that other end of the part. Then once that cools go back to the first end and add a little more solder. That's it!
For three terminal parts like transistors or the voltage regulator on the booster board do the same thing by soldering one leg first, getting the other two centered on their pads. Then solder up the other two, then back to the first.
For ICs it is the same thing. Anymore I put a small blog of solder on the soldering iron tip first. Then get the IC centered on all the pads while holding it from the sides with the tweezers. Take that solder blob and solder just one corner pin. then reheat that as much as necessary while moving the chip around with the tweezers to get all the pads centered. Tip: you will get the best results with all of the IC pins well centered on their pads. Make sure none are part of the way off the pad. Then solder the other diagonal corner pin to hold the chip in place. Finally either drag a ball of solder on the tip across the pins, or anymore I can pretty much solder them individually with fine gauge solder and a fine tip on the iron. Have solder wick handy! You will be highly likely to bridge two or more pins. Bridges comes right off with the wick. Be sure to look at all the pins through a magnifying glass after soldering.
For what its worth I sell the ODA and booster board with the surface mount stuff already soldered on in my vendor thread here in the vendor forum. But where is the fun in that! 🙂 I would highly recommend giving the DIY a try first if you are up for it. You might also want to check out OPC's "Wire" headphone amp board in another thread here. It is all surface mount, although the 0805 stuff which is one notch smaller. Just like NwAvGuy's dScope OPC has measured his with a similar Audio Precision tester. His "Wire" is just the amp board, with a separate power supply board and no case - you would mount the boards in your own case with the Wire. The ODA uses the Box Enclosures B4-080 case.
Once you have all that stuff it is just a matter of putting some solder on one of the two PC board pads for any two terminal device, like a resistor or capacitor. Then grab the part by the sides with the tweezers, reheat that solder on the pad, then stuff one end of the part in, while getting the other end of the part centered on the other PC board pad. 🙂 Not uncommon to have to reheat that end a few times to move the part around. Then just solder up that other end of the part. Then once that cools go back to the first end and add a little more solder. That's it!
For three terminal parts like transistors or the voltage regulator on the booster board do the same thing by soldering one leg first, getting the other two centered on their pads. Then solder up the other two, then back to the first.
For ICs it is the same thing. Anymore I put a small blog of solder on the soldering iron tip first. Then get the IC centered on all the pads while holding it from the sides with the tweezers. Take that solder blob and solder just one corner pin. then reheat that as much as necessary while moving the chip around with the tweezers to get all the pads centered. Tip: you will get the best results with all of the IC pins well centered on their pads. Make sure none are part of the way off the pad. Then solder the other diagonal corner pin to hold the chip in place. Finally either drag a ball of solder on the tip across the pins, or anymore I can pretty much solder them individually with fine gauge solder and a fine tip on the iron. Have solder wick handy! You will be highly likely to bridge two or more pins. Bridges comes right off with the wick. Be sure to look at all the pins through a magnifying glass after soldering.
For what its worth I sell the ODA and booster board with the surface mount stuff already soldered on in my vendor thread here in the vendor forum. But where is the fun in that! 🙂 I would highly recommend giving the DIY a try first if you are up for it. You might also want to check out OPC's "Wire" headphone amp board in another thread here. It is all surface mount, although the 0805 stuff which is one notch smaller. Just like NwAvGuy's dScope OPC has measured his with a similar Audio Precision tester. His "Wire" is just the amp board, with a separate power supply board and no case - you would mount the boards in your own case with the Wire. The ODA uses the Box Enclosures B4-080 case.
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Couldn't agree more... no fun at all. 🙂
OK... I'm gonna go for it. Need to gather up supplies now, but have couple questions first.
1) Is the panavise really that important? I already have a stand with alligator clips and magnifying glass. I'm guessing as the board gets built up it will get too heavy for the clips but all the surface mount stuff should be done before that point... maybe?
2) Looked up that solder you recommended on ebay and they sell different lengths (3ft, 5ft etc). How much do you think I need?
Thanks for the tips/tricks in your previous post; looking forward to this build.
4x4F150 - those "helping hands" with the aligator clips and small magnifier will do the job for the booster board, although they tip over a lot which gets annoying. Speaking of which.. you've probably seen the news that Radio Shack declared bankruptcy. Well here is one item I found at Radio Shack that is actually useful, this "helping hands on steriods" thing:
RadioShack LED Helping Hands with Magnifier - RadioShack.com
It is just the the common one (whch they also had) but the magifier is about 3 times the size and the base is heavier and more stable. I bought one months ago, but just today I was cruising their 60-80% off clearance sale at a local RS that is closing. I saw three of those on clearance sale for the 80% off. Their $40 regular price was crazy, but for $8 may be worth a look. 🙂
For the ODA though that Panavise or the equivalent is really pretty necessary. They sell a Panavise Jr that costs less and I also have. Let me give that a try tonight with the ODA board and see if it fits. I used that Jr for a long time and was impressed enough to get the 350, which just absolutely rocks. Those two jaws on the 350 can unscrew via the two big screws on each and flip around (the rubber on the jawas pulls off and flips around), making it able to hold something really tiny or something really wide. The Jr was still light enough to scoot around on the table a bit, but not the 350. It is one big boat achor.
I would say go for the 5 ft of the Cardas Quad. Make sure you buy the Quad, they also sell a tri-eutectic. Lol - back to Radio Shack - if you go there spot any left on the shelf they sold a eutectic silver solder that is pretty good, something like 36/62/2 in 0.022" and also in 0.015". The one problem with the Cardas is being a little larger at 0.032". The 0.022" & 0.015"is great for small parts. Especially great at 80% off. 😀 The silver content helps prevent chemical migration of the silver coating on silver teflon wires and silver plated contacts. I wouldn't recommend any lead-free solder though. That stuff is just trouble in my experience. Best left for production electronics.
RadioShack LED Helping Hands with Magnifier - RadioShack.com
It is just the the common one (whch they also had) but the magifier is about 3 times the size and the base is heavier and more stable. I bought one months ago, but just today I was cruising their 60-80% off clearance sale at a local RS that is closing. I saw three of those on clearance sale for the 80% off. Their $40 regular price was crazy, but for $8 may be worth a look. 🙂
For the ODA though that Panavise or the equivalent is really pretty necessary. They sell a Panavise Jr that costs less and I also have. Let me give that a try tonight with the ODA board and see if it fits. I used that Jr for a long time and was impressed enough to get the 350, which just absolutely rocks. Those two jaws on the 350 can unscrew via the two big screws on each and flip around (the rubber on the jawas pulls off and flips around), making it able to hold something really tiny or something really wide. The Jr was still light enough to scoot around on the table a bit, but not the 350. It is one big boat achor.
I would say go for the 5 ft of the Cardas Quad. Make sure you buy the Quad, they also sell a tri-eutectic. Lol - back to Radio Shack - if you go there spot any left on the shelf they sold a eutectic silver solder that is pretty good, something like 36/62/2 in 0.022" and also in 0.015". The one problem with the Cardas is being a little larger at 0.032". The 0.022" & 0.015"is great for small parts. Especially great at 80% off. 😀 The silver content helps prevent chemical migration of the silver coating on silver teflon wires and silver plated contacts. I wouldn't recommend any lead-free solder though. That stuff is just trouble in my experience. Best left for production electronics.
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agdr - I pulled the specs on the panavise jr (model 201). According to panavise's website, it only opens up to a max opening width of 73mm which would be too small. Maybe there's still some way to it to hold the board...
Panavise does have a model 396 which opens to a max width of 152mm so it would at least be able to hold the board in the 80mm dimension. This model has a smaller base than the 350 but still looks like it could get the job done and is only $63 off amazon (vs $90 for the 350 model).
Definitely going to radio shack after work tomorrow to see what I can steal at those deep discounts 😀
Panavise does have a model 396 which opens to a max width of 152mm so it would at least be able to hold the board in the 80mm dimension. This model has a smaller base than the 350 but still looks like it could get the job done and is only $63 off amazon (vs $90 for the 350 model).
Definitely going to radio shack after work tomorrow to see what I can steal at those deep discounts 😀
4x4F150 - you are right about the Jr, I had forgotten about that. Too narrow of an opening. On that Panavise 396 unfortunately for soldering purposes it is a lot better to hold the ODA board lengthwise in the 160mm direction. Much easier to get in there with tweezers and the soldering iron.
But.. here is an idea. 🙂 There is a way to do that same thing with the 350 parts:
The 350 head is the Panavise 376 for $51
PanaVise 376 Self-Centering, Extra Wide Opening Head: Bench Vises: Amazon.com: Industrial & Scientific
and the stand is the Panavise 300 for $25
PanaVise 300 Standard Base: Bench Vises: Amazon.com: Industrial & Scientific
so the would total $76 vs. the $89 for the 350, just would have to screw it down to a table or a piece of wood without that metal base. They also sell the metal base separately for $20 (Panavise 312) so you could even add that back later down the road.
But.. here is an idea. 🙂 There is a way to do that same thing with the 350 parts:
The 350 head is the Panavise 376 for $51
PanaVise 376 Self-Centering, Extra Wide Opening Head: Bench Vises: Amazon.com: Industrial & Scientific
and the stand is the Panavise 300 for $25
PanaVise 300 Standard Base: Bench Vises: Amazon.com: Industrial & Scientific
so the would total $76 vs. the $89 for the 350, just would have to screw it down to a table or a piece of wood without that metal base. They also sell the metal base separately for $20 (Panavise 312) so you could even add that back later down the road.
agdr - I like the idea on buying the vise and base to save a couple bucks. Probably the best bet for anyone who doesn't do a lot of board work.
For anyone thinking of this build - I just priced everything in the BOM and all the parts (excluding case and hardware for case was) ~ $205. I compared the prices between Mouser and Digikey and there was only 1 significant difference - mgf part# B32529C224K (line #145 in the BOM). This is really the only cheaper part on Digikey (0.23 vs 0.31). I know its only 8 cents, but you do have to buy 14 of them and there are 2 parts that are ONLY available on Digikey, so you might as well save the $$$. (Agdr will include these 2 parts with the board at cost if you want to avoid Digikey altogether). There were other parts cheaper on Digikey, but they were all only 1 cent difference.
I hope someone reads this and doesn't waist their time pricing everything on both sites like I did 🙁
For anyone thinking of this build - I just priced everything in the BOM and all the parts (excluding case and hardware for case was) ~ $205. I compared the prices between Mouser and Digikey and there was only 1 significant difference - mgf part# B32529C224K (line #145 in the BOM). This is really the only cheaper part on Digikey (0.23 vs 0.31). I know its only 8 cents, but you do have to buy 14 of them and there are 2 parts that are ONLY available on Digikey, so you might as well save the $$$. (Agdr will include these 2 parts with the board at cost if you want to avoid Digikey altogether). There were other parts cheaper on Digikey, but they were all only 1 cent difference.
I hope someone reads this and doesn't waist their time pricing everything on both sites like I did 🙁
Thanks for the update on current pricing! Yeah anyore it seems like Digikey is slightly more on most things than Mouser, except ICs and that may even be the same now. For some reason Mouser's IC prices seem to have taken a big across-the-board jump over the last few months. Digikey will likely follow if they haven't already.
I updated the O2 Booster Board BOM prices a few weeks ago (probably haven't posted that yet though). The prices on nearly everything were the same, except the ICs which had taken a dollar or two jump in every case (I have a big list of alternate IC choices at the bottom of that BOM).
I updated the O2 Booster Board BOM prices a few weeks ago (probably haven't posted that yet though). The prices on nearly everything were the same, except the ICs which had taken a dollar or two jump in every case (I have a big list of alternate IC choices at the bottom of that BOM).
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No batteries in the ODA. The power supply has a CRC filter followed by LM317/337 pre-regulators followed by LT1963A/3015 final LDO regulators. Along with further ripple reduction the main purpose of the preregulators is to drop the incoming voltage below the LT1963A's 20V maximum.
D17 is optional, but I would recommend it. It is a bi-directional transorb that solders undereneath the PB board right onto two the AC power jack contacts. The power jack contact at the end of the jack and then either of the other two. The transorb is extremely fast, picoseconds, right up there with a gas discharge tube, to nuke fast moving line transients.
I'll mail you one. 🙂 How is it going? Have you found any (other) parts missing?
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A few is missing but I have the D17... I'll gather a list and PM you or buy locally... R10 and R15 are the onl must have parts missing so far. But as I will populate all optional parts as they can be choosen by wiring I'll handle those by myself - so I'll toss in the R10/15 as well 🙂
So wiring is next for me - probably not this weekend as we will have guests 🙁 (😉).
So, for a bloke needing an input (3,5mm or RCA) and an output to Sennheiser HD650's (3,5 or bigun). What wiring is needed for a quick test?
I know the last bit on the rotary isn't working right now without R10/15...
I believe I have some low grade 1/4w I could attach for the test...
So D17 doesn't need an direction? Just solder it to the right pads?
Regards
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Turbon - R10 & R15 are left blank. Nothing missing there.🙂 Those are the 1x gain position and they are blank, just as in the O2. The pads are there in case someone wants something else for their low gain position, like 1.25x, etc.
Yep D17 is bidirectional so no polarity - either end is OK on either DC jack contact.
All the jumpers have to be installed to get sound out. Best to follow the build instructions and test the power supply output at JP18 and JP19 before jumpering those to feed power to the rest of the board. This is in the build instuctions, but one thing to watch out for on V2.0 is that JP19 jumpers sideways while JP18 jumpers up and down. You can see it from the bottom side of the board.
Yep D17 is bidirectional so no polarity - either end is OK on either DC jack contact.
All the jumpers have to be installed to get sound out. Best to follow the build instructions and test the power supply output at JP18 and JP19 before jumpering those to feed power to the rest of the board. This is in the build instuctions, but one thing to watch out for on V2.0 is that JP19 jumpers sideways while JP18 jumpers up and down. You can see it from the bottom side of the board.