Looking at building this amp, starting building the BOM on digikey (I am in Canada).
But already I am at $300 CAD, which isn't even all the parts, nor an enclosure, nor the PCB. So would it be possible to get the hard to find/obsoleted parts from you @agdr now while I save up for the rest?
Also does anyone have a PCB they could sell me? Min order is 5 which comes out to over $60 CAD shipped.
Gonna finish going through this BOM on both digikey and mouser and find all the obsoleted parts so I can at least get those now.
Part of me wonders if I should just build an O2...
But already I am at $300 CAD, which isn't even all the parts, nor an enclosure, nor the PCB. So would it be possible to get the hard to find/obsoleted parts from you @agdr now while I save up for the rest?
Also does anyone have a PCB they could sell me? Min order is 5 which comes out to over $60 CAD shipped.
Gonna finish going through this BOM on both digikey and mouser and find all the obsoleted parts so I can at least get those now.
Part of me wonders if I should just build an O2...
Hi! Thanks for your interest in the project. I've just replied to your email with some information. 🙂
I do have boards and any discontinued/out of stock/Digikey parts (so everything else can be ordered at Mouser) at-cost for anyone registered on the forum here. The board comes as a "kit" of sorts that contains the 12 1R 1/8W output resistors, all the stainless mounting hardware for the heatsinks, temporary heat sinks for the rear voltage regulators (until you get a rear panel), the two special screws that mount the RCA jacks to the panel, and rubber feet for the case.
It is true, all together the ODA costs a bit. Last I priced it the parts on the board are around $200 USD from Mouser. The case is around $25 from newark/arrow, the power transformer around $20, then the panel drilling and engraving at Front Panel Express is a chunk. They charge around $45 each to drill and engrave the back and front panels. Building it up a little bit at a time to spread the cost out is a good idea!
NwAvGuy's O2 is a good headamp, especially for a first project! It is all through-hole parts to solder, whereas the ODA has a lot of 1206 sized surface mount. The ODA amp here probably has 4x or 5x the number of parts to solder that the O2 does. Another one to take a look at is my "inverting version of the O2" here in this forum. That one is about 95% through hole parts. If you build an O2, yet another project to consider is my "O2 booster board" in this forum, that plugs into the O2 in place of the 2 output chips and fits in the top case slot.
Many other excellent headamp projects on the forum here, like opc's Wire headamp. So there you go, all sorts of good DIY projects to consider! 🙂
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Updated ODA BOM!
A big thanks to BunBun for his interest in building the ODA from all Digikey parts. That got me to finally go through the Digikey listing in detail - and update the entire BOM - something I've been meaning to do for awhile. Nothing needs to change if you already have an ODA. Nothing in the new BOM gives any more performance.
Up until now all the ODA builds that I've been aware of have been from Mouser parts. I had some Digikey parts listed as alternates in case Mouser was out of stock. Digikey didn't stock some key parts when I first wrote the BOM, but now that has changed. Especially with the addition of their Stackpole 1/8W, 1%, metal film, 50PPM/C through-hole resistor line which is equivalent to the Mouser Xicon 270- line. On the other side Mouser has started stocking some parts that used to be Digikey-only, such as the CUI RCA jacks and now 3.5mm output jack.
I've expanded the Digikey columns to include the Digikey price, for comparison to Mouser. Also included are the manufacturer and manufacturer part number in case the Digikey part is a different brand (but same specifications) as the Mouser part due to Digikey not carrying some product line or vise versa.
In addition to the attachment here I've also posted the new BOM out on the project Google Drive link . The link is always the best place to look for the most current project files.
I've taken the opportunity to update all the Mouser prices and the notes column. In several instances the Mouser price on larger items has dropped. Their prices on the small stuff though, like individual common diodes, has gone up a bit.
Lots of changes. Here are some of the larger ones:
In the “jacks, switches..” first section:
• The output 3.5mm jack is now the plastic-nose jack I used in the inverting O2. That means the front panel hole around that jack no longer has to be large to keep it from touching the case. Those plastic nose jacks are new at both Digikey and Mouser. Digikey had them first, now Mouser does after adding CUI’s products. I have the input and output on different ground stars. The input 3.5mm jack's metal nose single-point grounds the case to the input section ground star.
• I’ve moved the plastic nut for the ¼” jack from hardware to the jacks section, under the jack. Seemed to make more sense given they both have to come from a vendor that stocks Neutrik (Digikey doesn’t).
• Same with the plastic cap for the C&K push button switch (input select). That is now under the switch in the top section rather than in the hardware section.
• I had forgotten that Mouser now carries the “better” PC mount RCA jack from CUI that has red on the top. The part is no longer Digikey-only and no need to get it from me anymore. A person posted about that months ago.
• I also forgot about the relay situation. Digikey does not stock the “234” Omron series, what I used from Mouser, but they do stock the “274” series. Very hard to find out what the difference is! I had to write Omron. The 234 has 1-amp PdAu contacts, while the 274 is all Au (gold) with 2-amp contacts. Either would be just fine for the ODA.
• I’ve changed the power switch from the Mountain Switch (discontinued by Mouser) to an identical one by C&K. The M.S. was $3.65, the C&K is $7.65! Same switch type.
• Lots of updates to the notes column.
In the "IC, transistor" section:
• A note about the LME49990 being discontinued. Newark still has them in stock and I have them.
• I’ve changed the LT3015IT to the $1 less LT3015ET. I can't find a difference between the chips in the current data sheet. I think at one time they had the IT had a wider temperature range.
• Lots of updates to the notes column.
In the "diode, LED" section:
• I found a Digikey equivalent for the 2.4V zener at Mouser.
• Minor changes, mostly adding in all the Digikey parts and prices.
In the "chassis.." section:
• I moved out those jack nuts and switch caps.
• I’ve left off the blank PC board as a line item. The PC board probably doesn’t belong in the BOM.
In the "resistors, pots" section:
• Several brand changes to lower prices. Both Digikey and Mouser started stocking Panasonic 1206 0.1% SMD after I did the original BOM, which were cheaper but the same otherwise. Now lately both have started stocking Susumu and Yageo, which are ever cheaper in some cases. All are 0.1%, 1/4W 1206, 25PPM/C or less.
• I have been able to bump up the wattage from 1/8W to 1/4W on a few of the Mouser SMD resistors (lower Johnson noise) since they now stock some alternatives to KOA Spear. The KOA 1206 were mostly all 1/8W. Now I’m finding Yageo and Susumu 1/4W for some of the harder to find values.
• I've split the "SMD - thin film" and "SMD - thick film" into different headings. Before they were mixed, which was confusing.
In the "capacitors" section
• Many changes! Lots of updates to the digikey parts.
• The 1000uF 50V (Nichicon) main caps I had specified at Mouser are out of stock until July. The alternate 100uF 50V (UCC) I had specified at Digikey is in stock. Mouser now carrries that one too. It is exactly equivalent, low ESR, so I just switched them both over to the UCC cap.
• The brand changed on the 10uF clipping detect cap and a few other caps to parts stocked at both Digikey and Mouser.
A big thanks to BunBun for his interest in building the ODA from all Digikey parts. That got me to finally go through the Digikey listing in detail - and update the entire BOM - something I've been meaning to do for awhile. Nothing needs to change if you already have an ODA. Nothing in the new BOM gives any more performance.
Up until now all the ODA builds that I've been aware of have been from Mouser parts. I had some Digikey parts listed as alternates in case Mouser was out of stock. Digikey didn't stock some key parts when I first wrote the BOM, but now that has changed. Especially with the addition of their Stackpole 1/8W, 1%, metal film, 50PPM/C through-hole resistor line which is equivalent to the Mouser Xicon 270- line. On the other side Mouser has started stocking some parts that used to be Digikey-only, such as the CUI RCA jacks and now 3.5mm output jack.
I've expanded the Digikey columns to include the Digikey price, for comparison to Mouser. Also included are the manufacturer and manufacturer part number in case the Digikey part is a different brand (but same specifications) as the Mouser part due to Digikey not carrying some product line or vise versa.
In addition to the attachment here I've also posted the new BOM out on the project Google Drive link . The link is always the best place to look for the most current project files.
I've taken the opportunity to update all the Mouser prices and the notes column. In several instances the Mouser price on larger items has dropped. Their prices on the small stuff though, like individual common diodes, has gone up a bit.
Lots of changes. Here are some of the larger ones:
In the “jacks, switches..” first section:
• The output 3.5mm jack is now the plastic-nose jack I used in the inverting O2. That means the front panel hole around that jack no longer has to be large to keep it from touching the case. Those plastic nose jacks are new at both Digikey and Mouser. Digikey had them first, now Mouser does after adding CUI’s products. I have the input and output on different ground stars. The input 3.5mm jack's metal nose single-point grounds the case to the input section ground star.
• I’ve moved the plastic nut for the ¼” jack from hardware to the jacks section, under the jack. Seemed to make more sense given they both have to come from a vendor that stocks Neutrik (Digikey doesn’t).
• Same with the plastic cap for the C&K push button switch (input select). That is now under the switch in the top section rather than in the hardware section.
• I had forgotten that Mouser now carries the “better” PC mount RCA jack from CUI that has red on the top. The part is no longer Digikey-only and no need to get it from me anymore. A person posted about that months ago.
• I also forgot about the relay situation. Digikey does not stock the “234” Omron series, what I used from Mouser, but they do stock the “274” series. Very hard to find out what the difference is! I had to write Omron. The 234 has 1-amp PdAu contacts, while the 274 is all Au (gold) with 2-amp contacts. Either would be just fine for the ODA.
• I’ve changed the power switch from the Mountain Switch (discontinued by Mouser) to an identical one by C&K. The M.S. was $3.65, the C&K is $7.65! Same switch type.
• Lots of updates to the notes column.
In the "IC, transistor" section:
• A note about the LME49990 being discontinued. Newark still has them in stock and I have them.
• I’ve changed the LT3015IT to the $1 less LT3015ET. I can't find a difference between the chips in the current data sheet. I think at one time they had the IT had a wider temperature range.
• Lots of updates to the notes column.
In the "diode, LED" section:
• I found a Digikey equivalent for the 2.4V zener at Mouser.
• Minor changes, mostly adding in all the Digikey parts and prices.
In the "chassis.." section:
• I moved out those jack nuts and switch caps.
• I’ve left off the blank PC board as a line item. The PC board probably doesn’t belong in the BOM.
In the "resistors, pots" section:
• Several brand changes to lower prices. Both Digikey and Mouser started stocking Panasonic 1206 0.1% SMD after I did the original BOM, which were cheaper but the same otherwise. Now lately both have started stocking Susumu and Yageo, which are ever cheaper in some cases. All are 0.1%, 1/4W 1206, 25PPM/C or less.
• I have been able to bump up the wattage from 1/8W to 1/4W on a few of the Mouser SMD resistors (lower Johnson noise) since they now stock some alternatives to KOA Spear. The KOA 1206 were mostly all 1/8W. Now I’m finding Yageo and Susumu 1/4W for some of the harder to find values.
• I've split the "SMD - thin film" and "SMD - thick film" into different headings. Before they were mixed, which was confusing.
In the "capacitors" section
• Many changes! Lots of updates to the digikey parts.
• The 1000uF 50V (Nichicon) main caps I had specified at Mouser are out of stock until July. The alternate 100uF 50V (UCC) I had specified at Digikey is in stock. Mouser now carrries that one too. It is exactly equivalent, low ESR, so I just switched them both over to the UCC cap.
• The brand changed on the 10uF clipping detect cap and a few other caps to parts stocked at both Digikey and Mouser.
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Hello.
I am looking to build this amp. I live in Croatia, so I have get 230VAC with 16VAC/2A on secondary winding of transformer.
I was also thinking of making custom wooden case, and maybe putting transformer into the same custom wooden case.
I have already built O2+ODAC(with the old DVD case I reused and did not like the looks) in wooden case. But I have AC/AC adapter separately.
-Do really need the metal case/RF shield?
-I was thinking about this transformer http://hr.mouser.com/ProductDetail/...=sGAEpiMZZMvwUzoUXIIvyYLyls7gHR394CZ6sozGWtg=
This way I can get a nicer looking case for less money.
The only things hard to get are few items that are not stocked on mouser and PCB.
I am looking to build this amp. I live in Croatia, so I have get 230VAC with 16VAC/2A on secondary winding of transformer.
I was also thinking of making custom wooden case, and maybe putting transformer into the same custom wooden case.
I have already built O2+ODAC(with the old DVD case I reused and did not like the looks) in wooden case. But I have AC/AC adapter separately.
-Do really need the metal case/RF shield?
-I was thinking about this transformer http://hr.mouser.com/ProductDetail/...=sGAEpiMZZMvwUzoUXIIvyYLyls7gHR394CZ6sozGWtg=
This way I can get a nicer looking case for less money.
The only things hard to get are few items that are not stocked on mouser and PCB.
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bozoc - that is some very nice looking woodwork! 🙂 I like how it is finished. Ideally it is good to have the metal shielding, in case there is a strong radio station, fluorescent lights, etc. in the area. But one solution there is spray the inside of the wood with a conductive paint. For shielding purposes the thin paint thickness is all you need. In fact, Hammond does that with the shielded plastic boxes that I use for another project here, their 1598REBK. The insides are sprayed with copper-colored conductive paint.
The ODA PC board does have holes in the corners for mounting, so you are not forced to use the metal box with the board slots.
I would recommend putting the transformer in a separate box if you can, and locate it a distance away, just to eliminate any possibility of hum. That is what louiebh (in the UK) did with his, here on post 829:
http://www.diyaudio.com/forums/head...ersion-o2-desktop-amp-oda-17.html#post4400957
We just boxed a toroid up in a separate metal box. Or if everything is in a single box just make sure the transformer and all the line-side AC wiring are a good distance away from the ODA PC board to avoid any 50Hz hum pickup.
Unfortunately all the transformers that Mouser stock are 60Hz, to the best of my knowledge, and you probably have 50Hz power line frequency. The datasheet on the Triad part you linked doesn't say, but I would be about 99.9% certain it would be 60Hz. 60Hz transformers can overheat on 50Hz, but the other way around is OK, 50Hz xformers work just fine on 60Hz. In the case of louiebh he bought a transformer from Farnell there in the UK (all of Farnell's transformers are 50Hz) and shipped it to me.
I do have the bare PC boards for the ODA! 4 layer and gold (ENIG) finished. I'll send you a PM. It is about 2/3 surface mount parts, but they are the larger 1206 size. I also can supply any of the parts that Mouser is out of stock on, or no longer stock, same price as Mouser lists.
The ODA is fun DIY build! 🙂 I have tips on surface mount soldering in the build instructions (all the project materials are at the Google Drive link in the first post in this thread) if you haven't surface mount soldered before.
The ODA PC board does have holes in the corners for mounting, so you are not forced to use the metal box with the board slots.
I would recommend putting the transformer in a separate box if you can, and locate it a distance away, just to eliminate any possibility of hum. That is what louiebh (in the UK) did with his, here on post 829:
http://www.diyaudio.com/forums/head...ersion-o2-desktop-amp-oda-17.html#post4400957
We just boxed a toroid up in a separate metal box. Or if everything is in a single box just make sure the transformer and all the line-side AC wiring are a good distance away from the ODA PC board to avoid any 50Hz hum pickup.
Unfortunately all the transformers that Mouser stock are 60Hz, to the best of my knowledge, and you probably have 50Hz power line frequency. The datasheet on the Triad part you linked doesn't say, but I would be about 99.9% certain it would be 60Hz. 60Hz transformers can overheat on 50Hz, but the other way around is OK, 50Hz xformers work just fine on 60Hz. In the case of louiebh he bought a transformer from Farnell there in the UK (all of Farnell's transformers are 50Hz) and shipped it to me.
I do have the bare PC boards for the ODA! 4 layer and gold (ENIG) finished. I'll send you a PM. It is about 2/3 surface mount parts, but they are the larger 1206 size. I also can supply any of the parts that Mouser is out of stock on, or no longer stock, same price as Mouser lists.
The ODA is fun DIY build! 🙂 I have tips on surface mount soldering in the build instructions (all the project materials are at the Google Drive link in the first post in this thread) if you haven't surface mount soldered before.
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Thank you very much agdr. Very useful information.
Yes, in Croatia as in most of the Europe frequency is 50Hz. Good that you pointed to me that 60Hz transformers do not work well on 50Hz.
Will keep my eye on adequate transformer to buy.
And I will make two cases again as I did with O2, one for the amp and other for the transformer.
I can also make an aluminum shield inside the case of the amp+DAC and the transformer(I will ground the transformer case then).
I have never done any SMD soldering, so this will be an adventure for me 🙂.
Yes, in Croatia as in most of the Europe frequency is 50Hz. Good that you pointed to me that 60Hz transformers do not work well on 50Hz.
Will keep my eye on adequate transformer to buy.
And I will make two cases again as I did with O2, one for the amp and other for the transformer.
I can also make an aluminum shield inside the case of the amp+DAC and the transformer(I will ground the transformer case then).
I have never done any SMD soldering, so this will be an adventure for me 🙂.
PM just sent, sorry for the delay! I've been away from the computer most of the day. 🙂
I've realized today that the front and rear panels do pretty much need to be metal. The rear panel acts as the heat sink for the two voltage regulators. The front panel has several PC-mount parts with short shafts, sized for the 2mm thick metal panel. Two push button switches and a small 5 position rotary switch for the gain selection. So to use wood, may be best with metal front and back but the sides as wood. But then there could be some alignment chalenges between the board mounting and panel holes. With the metal case everything automatically lines up.
I've done a scan on the BOM and the few things Mouser doesn't stock anymore or are out of stock I have here, details in the PM. 🙂
I've found that for SMD soldering the two things that are really essential is a good pair of right angle tweezers and a vice to hold the board, to act like a 3rd hand. I have some suggestions for those in the build instructions. Then it is just a matter of putting a little solder on one of the resistor or capacitor pads, stick one end of the part in while heating that solder and line up the other end, solder the other end, then go back and re-solder that first end. You will be pretty good at SMD soldering by the time you are done with the ODA board! 😀
I've realized today that the front and rear panels do pretty much need to be metal. The rear panel acts as the heat sink for the two voltage regulators. The front panel has several PC-mount parts with short shafts, sized for the 2mm thick metal panel. Two push button switches and a small 5 position rotary switch for the gain selection. So to use wood, may be best with metal front and back but the sides as wood. But then there could be some alignment chalenges between the board mounting and panel holes. With the metal case everything automatically lines up.
I've done a scan on the BOM and the few things Mouser doesn't stock anymore or are out of stock I have here, details in the PM. 🙂
I've found that for SMD soldering the two things that are really essential is a good pair of right angle tweezers and a vice to hold the board, to act like a 3rd hand. I have some suggestions for those in the build instructions. Then it is just a matter of putting a little solder on one of the resistor or capacitor pads, stick one end of the part in while heating that solder and line up the other end, solder the other end, then go back and re-solder that first end. You will be pretty good at SMD soldering by the time you are done with the ODA board! 😀
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I appreciate your trouble to look into these.
I was planing to make two cases, one of aluminum and other from wood, the aluminium ones holds the components and I can make a cut out for the heat sinks on the back. All that I can easily work around.
I was wondering would this transformer work with ODA
http://www.produktinfo.conrad.com/d...873-da-01-de-RINGKERNTRAFO_50VA_230V_2X9V.pdf ?
It has 2x9v with each delivering 2.7A, I can connect them in series and get 18V.
From my understanding regular ODA build can work with anything from 16 to 20V, 40VA,if that is right?
I am sorry to hear about PCs, ODA is a great project with amazing features!
From what I see The Wire measures excellent, but I am very interested in how it compares to O2 and ODA(that has more features than Wire), is it really transparent and that powerful?
Božo.
I was planing to make two cases, one of aluminum and other from wood, the aluminium ones holds the components and I can make a cut out for the heat sinks on the back. All that I can easily work around.
I was wondering would this transformer work with ODA
http://www.produktinfo.conrad.com/d...873-da-01-de-RINGKERNTRAFO_50VA_230V_2X9V.pdf ?
It has 2x9v with each delivering 2.7A, I can connect them in series and get 18V.
From my understanding regular ODA build can work with anything from 16 to 20V, 40VA,if that is right?
I am sorry to hear about PCs, ODA is a great project with amazing features!
From what I see The Wire measures excellent, but I am very interested in how it compares to O2 and ODA(that has more features than Wire), is it really transparent and that powerful?
Božo.
Thanks for your interest in the ODA! I really should have checked on the boards first. 🙂 That transformer would have worked well, 18Vac total is just about perfect for the ODA.
A big benefit of the Wire is OPC has access to an AP tester and performed some THD+N measurements on it. Good question on actual A/B versus the O2 though! In all the posts in the Wire thread I can't really remember anyone posting Wire vs. O2 (or ODA) listening impressions. If someone out there has a link to a post like that, please post.
Hey appologies if you tried to PM and it bounced, I'm taking a little break from audio for the rest of the year due to some issues on my end. I've turned off PMs so someone doesn't leave one and not get a reply for a long time. 🙂
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Found some boards
bozoc - I managed to locate the ODA boards. 🙂 I was looking in the wrong box. All I had been able to find was the previous V2.0, but I found where I put the latest V2.1 boards. I'll turn the PMs on again for a few days. If you want one let me know, same deal at-cost for folks on the forum. If you want to run with the Wire instead no problem, that is a fine amp too. 🙂
But you really would be best off with metal end panels if you do build an ODA up, or ideally the entire metal case so that the jacks and switches align properly with the panel holes. I had forgotten how close the tolerances are where the parts go through the panel holes, plus several of those are not really panel-mountable. With the specified metal case all just lines up perfectly mechanically. So like you said, maybe box the transformer up in the all-wood box. I'm glad you asked the question about alternate cases, I'm going to add it to the ODA faq I have.
bozoc - I managed to locate the ODA boards. 🙂 I was looking in the wrong box. All I had been able to find was the previous V2.0, but I found where I put the latest V2.1 boards. I'll turn the PMs on again for a few days. If you want one let me know, same deal at-cost for folks on the forum. If you want to run with the Wire instead no problem, that is a fine amp too. 🙂
But you really would be best off with metal end panels if you do build an ODA up, or ideally the entire metal case so that the jacks and switches align properly with the panel holes. I had forgotten how close the tolerances are where the parts go through the panel holes, plus several of those are not really panel-mountable. With the specified metal case all just lines up perfectly mechanically. So like you said, maybe box the transformer up in the all-wood box. I'm glad you asked the question about alternate cases, I'm going to add it to the ODA faq I have.
A question has just came up about the power transformer here in the US, since Triad stopped making (and Mouser stopped stocking) AC-AC wall transformers. Luckily Jameco (Jameco Electronics - Electronic Components Distributor) still has a full line of AC-AC wall transformers. They also have some of the ODA parts, although I don't have a column for those on the BOM. They have the 10R trimmer resistors currently out of stock at Mouser (Digikey also has them). Newark has the discontinued LME49990 chips and I have them too.
For the "standard" +/-12.5Vdc power rails in the O2 the best Jameco transformer is their #2179622, 18Vac 2A:
AFU180200: Jameco Reliapro : 18VAC 2A AC-to-AC Wall Adapter Power Supply : Power Supplies & Wall Adapters
For the "standard" +/-12.5Vdc power rails in the O2 the best Jameco transformer is their #2179622, 18Vac 2A:
AFU180200: Jameco Reliapro : 18VAC 2A AC-to-AC Wall Adapter Power Supply : Power Supplies & Wall Adapters
Finally collected all the parts for the ODA amplifier.
I had to re-order transformer they sent different model. As I started working my soldering iron broke. . . Bummer.
I bought new soldering station https://www.reichelt.com/Soldering-...GROUPID=4543&artnr=STATION+LF-3200&SEARCH=%2A
My worktable is ready to start working on ODA again when the sodlering station comes.
I am so excited!
I had to re-order transformer they sent different model. As I started working my soldering iron broke. . . Bummer.
I bought new soldering station https://www.reichelt.com/Soldering-...GROUPID=4543&artnr=STATION+LF-3200&SEARCH=%2A
An externally hosted image should be here but it was not working when we last tested it.
My worktable is ready to start working on ODA again when the sodlering station comes.
I am so excited!
An XYtronic station is what I use too! I have the older LF1680 (80W)
Xytronic LF-1680 80W Soldering Iron & Thermal Tweezer Combo
There are definitely times I wish it had a bit more wattage like your LF3200, when soldering to chip heat sinks or large PC planes! The tips on the XYtronics last nearly forever. Before the 1680 I had a really old analog XYtronic I used for years and years.
Please let me know if I can answer any ODA build questions that may come up!
ODA board is waiting 🙂
I have looked at the panels and I haven't seen any holes for output damping resistor switch.
Also the DC offset should be near 0V, my multi meter definitely does not go to micro Volts. My meter does not go that low.
Nice workstation setup there! 🙂
The output damping factor switch is an optional panel-mount rotary switch. All the yellow background parts in the BOM are optional, including the Zobel network parts. I'm not aware of anyone who has needed to use the Zobel on the ODA. I just put the places on the board to cover all bases. I was thinking about AMB's b22 at the time which requires an added Zobel in some cases to prevent oscillation.
That panel mount output damping switch would wire into the holes for R88 and R89. I *think* I've put instructions for that in the build instructions, but if not just let me know and I'll send you the details if you want to try it. R88 and R89 are just places for output series resistors that are normally jumpered across. Just wanting to cover all bases again. 🙂
The damping switch wouldn't fit in the B4 case though, the board would have to be put in a larger case to use it. I'm not aware of anyone who has built the ODA who has added that switch yet.
On the DC output offset adjust, in the build instructions there is a procedure for pre-setting the two trimmer resistors by using an ohmmeter to center them before installing. That should get you very close and will probably read zero volts DC out from the amp on your meter. The amount of fine tunning of the two DC offset trimmers from that initial set point is always very small, if even any at all..
The output damping factor switch is an optional panel-mount rotary switch. All the yellow background parts in the BOM are optional, including the Zobel network parts. I'm not aware of anyone who has needed to use the Zobel on the ODA. I just put the places on the board to cover all bases. I was thinking about AMB's b22 at the time which requires an added Zobel in some cases to prevent oscillation.
That panel mount output damping switch would wire into the holes for R88 and R89. I *think* I've put instructions for that in the build instructions, but if not just let me know and I'll send you the details if you want to try it. R88 and R89 are just places for output series resistors that are normally jumpered across. Just wanting to cover all bases again. 🙂
The damping switch wouldn't fit in the B4 case though, the board would have to be put in a larger case to use it. I'm not aware of anyone who has built the ODA who has added that switch yet.
On the DC output offset adjust, in the build instructions there is a procedure for pre-setting the two trimmer resistors by using an ohmmeter to center them before installing. That should get you very close and will probably read zero volts DC out from the amp on your meter. The amount of fine tunning of the two DC offset trimmers from that initial set point is always very small, if even any at all..
Thank you for the detailed info 🙂!
It seems that I will be the first person to make ODA with output resistors because I bought 6 position rotary switch and few resistor combinations(1R,10R,30R,80R,120R). I have read about your output impedance paragraph in build instructions and it seems like a very useful option to have in headphone amp.
As for the case, I will be making my own case anyways so I have a lot of freedom as where to place output resistance rotary switch.
It seems that I will be the first person to make ODA with output resistors because I bought 6 position rotary switch and few resistor combinations(1R,10R,30R,80R,120R). I have read about your output impedance paragraph in build instructions and it seems like a very useful option to have in headphone amp.
As for the case, I will be making my own case anyways so I have a lot of freedom as where to place output resistance rotary switch.
I had forgotten that you are using a bigger case! By all means, go ahead an add that damping factor switch. 🙂 This Teac headphone amp (HA-501B) has a front-panel damping factor rotary switch and is the one I had in mind at the time when I added that optional feature:
https://www.amazon.com/Teac-HA-501-B-Monaural-Headphone-Amplifier/dp/B00AE991VG
https://www.amazon.com/Teac-HA-501-B-Monaural-Headphone-Amplifier/dp/B00AE991VG
I have finally gotten my new soldering station. Excited working with new station and working on ODA itself.
I was wondering about flux removal. Would ODA handle ultrasonic bath(worried for IC11 and thermal grease).
Is ultrasonic bath option with ODA at all?
I was wondering about flux removal. Would ODA handle ultrasonic bath(worried for IC11 and thermal grease).
Is ultrasonic bath option with ODA at all?
You are off to a good start!
Interesting question. I've never used ultrasound for rosin removal before, I typically use 99% isopropyl:
https://www.amazon.com/Swan-Isopropyl-Alcohol-99-Pint/dp/B001B5JT8C?th=1
My only concern was with the PC board itself (potentially becoming de-laminated) since it is 4 layer. So I just sent the question into the company that fabricated the PC board. Here is their reply:
"I have checked it with our assembly house, yes, we do use ultrasound for rosin core flux removal. "
So there you go! This same company also does PCB assembly using their own boards. In fact I had them assemble some tiny boards for me recently. I think you would be OK with IC11 regardless. I'll bet the ultrasound would only get the heat sink grease a certain distance in from the edges, the middle would still likely have grease. Even if it did remove all the grease, for this particular situation you would still get enough thermal transfer to the heat sink just with the pressure from the bolt and nut.
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