Lol! 😀 Well that worked out well, you can include those extra parts if you want when you order. The part numbers are in the V2.1 BOM, but I'll get them together in one document and post it out on the V2.0 Google drive section.
Rear panel CAD posted, ordered wrong LT regulators
I've just posted the updated rear panel for this project at the Google Drive link in the first post in this thread. I've added 3 vent holes at the top of the panel and updated the power jack lettering. Remember that Front Panel Express has a sale on through tomorrow, 20% off.
I haven't added a USB hole yet for an ODAC, I want to wait for some more dScope testing with the ODAC in it, but if you want a good panel for that consider the CAD that dace posted.
I discovered last night that I ordered the wrong package for all the LT regulators, the TO263 rather than the TO220! I've re-ordered and should have them by the end of the week. I'm going to send out the rest of the PMs today, but if you want a regulator it won't ship until the end of this coming week or the first of the following week when the regulators arrive.
I've just posted the updated rear panel for this project at the Google Drive link in the first post in this thread. I've added 3 vent holes at the top of the panel and updated the power jack lettering. Remember that Front Panel Express has a sale on through tomorrow, 20% off.
I haven't added a USB hole yet for an ODAC, I want to wait for some more dScope testing with the ODAC in it, but if you want a good panel for that consider the CAD that dace posted.
I discovered last night that I ordered the wrong package for all the LT regulators, the TO263 rather than the TO220! I've re-ordered and should have them by the end of the week. I'm going to send out the rest of the PMs today, but if you want a regulator it won't ship until the end of this coming week or the first of the following week when the regulators arrive.
agdr - I've (yet another weird) suggestion: a USB isolator for the ODAC. If the ODA had a board to take the USB in, and swap out the USB power for ODA-regulated power, that could help with bad USB ports (or bad USB controllers).
That said, I have no idea how perceptible the ODAC actually is to USB noise, but it could help those with exceptionally noisy systems and/or those whose USB ports can't provide the correct voltage.
I suggest this mainly because I've seen a few USB isolators being sold (iFi Audio, Schiit) and wondered if some people's complaints about the ODAC had anything to do with their USB ports.
Edit: Also, if it were cheap to implement it's both a "why not?" and yet another thing audio companies charge way too much money for that the ODA could do better.
That said, I have no idea how perceptible the ODAC actually is to USB noise, but it could help those with exceptionally noisy systems and/or those whose USB ports can't provide the correct voltage.
I suggest this mainly because I've seen a few USB isolators being sold (iFi Audio, Schiit) and wondered if some people's complaints about the ODAC had anything to do with their USB ports.
Edit: Also, if it were cheap to implement it's both a "why not?" and yet another thing audio companies charge way too much money for that the ODA could do better.
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Hi,
Tomb will be offering a USB isolator in kit form soon at Beezar.com. I was part of the trial builds and can say that it is a good product. It is supposed to be offered with or without casing. Whether it fits internally with the ODA is a different story.
Me
Tomb will be offering a USB isolator in kit form soon at Beezar.com. I was part of the trial builds and can say that it is a good product. It is supposed to be offered with or without casing. Whether it fits internally with the ODA is a different story.
Me
Sounds interesting! I'll keep an eye out for it, but with the USB connector soldered on to the PCB I realise now it'll be a messy job to try and chain the two inside the case. Nevertheless, a good cheap DIY USB isolator is definitely something I'd be up for trying.
If we could desolder the ODAC's USB, or cut it's power traces and power them with our own wires that could work. A short internal USB cable seems like a bad idea at best. Either way it's far from ideal.
Moragg & muskyhuntr - I like those ideas of the USB isolator and of trying to use Tomb's board for it!
I've had enough chats with various people about that ODAC issue now to be 100% sure a galvanic isolater is *required* with the ODAC on some installations to make things work right. Since the ODAC would be mounted to a carrier board in the ODA it would be especially slick if there were a galvanic isolater just as a basic part of the build like that.
I've seen mention of Tomb's board but haven't looked into it yet. I will. Tomb designs some excellent things. I would have no hesitation at all about making mountings available to mount his board if things would fit that way.
I know that dace had to notch out part of his ODAC carrier board to avoid the 820uF caps. That issue will go away in September when the new shorter 820uF's become available.
I do have an ODAC board here now, just haven't had a chance to mess with it yet. But I will after this round of board shipments goes out. 🙂
And something unrelated... I was staring at this circuit diagram of Dr Meier's "enhanced bass natural crossfeed filter" circuit on the old Headwize site that is back up again it seems:
An Enhanced-Bass Natural Crossfeed Filter | HeadWize
Now compare that to the bass boost part of the ODA's gain stage in the schematic here:
https://drive.google.com/folderview?id=0B67cJELZW-i8UG5yb19BTTFCSWs&usp=sharing
The bass boost circuiit is exactly the same, a common way to do it. So add two resistors and a capacitor and you have crossfeed! 😀 I'll have to ponder (and simulate) that a bit more since the bass boost parts are part of the op-amp feedback circuit on the ODA, but it may be possible to make a small circuit board that would solder onto the back of a panel-mounted switch (crossfeed on/off and/or bass boost on/off) then the twisted pair wires go to points on the ODA circuit board.
I've had enough chats with various people about that ODAC issue now to be 100% sure a galvanic isolater is *required* with the ODAC on some installations to make things work right. Since the ODAC would be mounted to a carrier board in the ODA it would be especially slick if there were a galvanic isolater just as a basic part of the build like that.
I've seen mention of Tomb's board but haven't looked into it yet. I will. Tomb designs some excellent things. I would have no hesitation at all about making mountings available to mount his board if things would fit that way.
I know that dace had to notch out part of his ODAC carrier board to avoid the 820uF caps. That issue will go away in September when the new shorter 820uF's become available.
I do have an ODAC board here now, just haven't had a chance to mess with it yet. But I will after this round of board shipments goes out. 🙂
And something unrelated... I was staring at this circuit diagram of Dr Meier's "enhanced bass natural crossfeed filter" circuit on the old Headwize site that is back up again it seems:
An Enhanced-Bass Natural Crossfeed Filter | HeadWize
Now compare that to the bass boost part of the ODA's gain stage in the schematic here:
https://drive.google.com/folderview?id=0B67cJELZW-i8UG5yb19BTTFCSWs&usp=sharing
The bass boost circuiit is exactly the same, a common way to do it. So add two resistors and a capacitor and you have crossfeed! 😀 I'll have to ponder (and simulate) that a bit more since the bass boost parts are part of the op-amp feedback circuit on the ODA, but it may be possible to make a small circuit board that would solder onto the back of a panel-mounted switch (crossfeed on/off and/or bass boost on/off) then the twisted pair wires go to points on the ODA circuit board.
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This has got me really excited for an ODA now.
Only thing is, doesn't the isolator need it's own power supply? TomB's board obviously wouldn't take into account the ODA's power, and having 2 power connectors seems silly. If he made his circuit designs available to modify to fit the ODA that'd be ideal - but I don't know if his designs are not-for-profit like yours.
I've been playing about with the bs2b plugin for f2k and can say I have mixed feelings. It was certainly less fatiguing but that's because there was a lot less to focus on - the music lost the enveloping feeling you get normally and there was significant cancellation going on, which lost quite a few parts of the music.
Headwize did have an article about frequency-dependant delay for crossfeed iirc, which may help. Anyway, since there are only capacitors (which set frequency cutoff) and resistors (which set attenuation) iirc you could use multiple on yet another select switch.
There may be a couple of ways around that. I see that commercial isolators apparently include an isolated DC to DC converter to pass the USB power along:
USB2ISO USB 2.0 Galvanic Isolator Adaptor ($59.95) : Saelig Online Store
In the ODA's case a separate small voltage regulator could be put on the carrier board to convert the ODA's +12Vdc to +5vdc. That would also provide isolation between the digital power rail and the ODA's analog power rail. In fact, I would be inclined to power it from the +14.5Vdc pre-regulator. There are holes on the ODA for all this. There is a hole after each pre-regulator for a test point that can also be used as a power take-off, and of course spare holes on the JP18 and JP19 final power supply output.
Lol - I'm big on not re-inventing the wheel - I would have no issues with just using that commercial isolator if there is a way to make it fit. Maybe pry the case open and bolt the innards down to the ODA carrier board. Like most things commercial I'll bet it would be somewhere between hard and impossible to re-create whatever is inside for anything near the price, given quantity manufacturing. Click on the "specifications" tab in that link and they say which AD chip is being used.
Interesting about the software! The few posts I've seen over at Head-Fi about crossfeed plugins all seem to be less than thrilled, plus some of the plugins are for-pay and rather pricey it seems.
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I would expect soon. I know he has been busy with a move to a new home. And IIRC he had problems with etching on the case and the sample printed circuit boards not being quite right.
Me
Me
I have no idea what an isolator requires, but TomB's designs seem DIY so I thought it wouldn't be too difficult to solder together. As the actual clever person here you know what does/doesn't work and what's worth the effort, I'm just a random ideas guy. I can't really do more than that.
I've done a bit more messing around, and in the plugin I mentioned the J.Meier preset is what sounded "best" to me over a length of time. I've become extremely adjusted to stereo listening, and the other settings narrowed the soundstage way too horribly. This on the other hand did just what I hoped from a crossfeed - it "lifted" the music off my ears, and was entirely non-fatiguing to listen too.
This is sounding uncomfortably audiophilic in it's description, so I'll just say to try it out yourself. As a "minimum" setting I find it really nice - there was barely any loss of detail and on some recordings I couldn't hear the switch, even while switching it on/off during the recording. The best analogy I can find would be overly-tight headphone bands - reducing the clamping pressure just relaxes everything slightly and makes it more comfortable.
I don't know if the delay/frequency choice are, or should be, variant by person due to factors like head size. My headphones are IE80s - IEMs, so the sound is anyway presented very close to the head, usually just inside it - which could mean I experience more dramatic results than with, say, big open-back cans like the HD650s.
They actually have software implementing the Meier crossfeed! I didn't know that was out there. I'll have to give that a try.
The simple parts addition to the ODA didn't work out. I was hoping that bridging the two gain stages at the non-inverting inputs would work but I ran through the math and no dice. It does come up with cross terms from the opposing input, but it isn't the same terms for the Meier crossfeed. Putting it in where the attenutaion resistors are might work, depending on loading by the 1K pot. I'll look into that.
Attachments
Second source at Digikey for the RCA jacks and dual 1K 9mm pot
Here is some good news on this project. I've found in-stock alternates for the two out-of-stock things on the BOM right now.
Digikey has an RCA jack that is an exact duplicate in a different manufacturer, CUI, and they are in stock. Digikey part number CP-1435-ND. Digikey has relatively cheap USPS shipping now, but if anyone overseas needs them I'm going to be ordering a bunch and could send them out at-cost.
I also discovered that Mouser does in fact have a 9mm 1K/1K dual 50mW linear pot in stock in a different manufacturer, one without a picture showing.
I've missed finding that one until now because Mouser has it incorrectly listed as a "panel mount" pot instead of the actual PC mount. I've sent them a heads-up on their listing mistake. This one has a longer 20mm shaft though (vs. 15mm) and the shaft is smooth and slotted so would require a setscrew knob. Mouser shows the original Bourns pot arriving in just two weeks, but if anyone doesn't want to wait this pot with the longer shaft is Mouser #72-P9A2RFISX1BB2102M .
I'll be posting a revised BOM tonight on the Google Drive link with these listed as alternates.
Here is some good news on this project. I've found in-stock alternates for the two out-of-stock things on the BOM right now.
Digikey has an RCA jack that is an exact duplicate in a different manufacturer, CUI, and they are in stock. Digikey part number CP-1435-ND. Digikey has relatively cheap USPS shipping now, but if anyone overseas needs them I'm going to be ordering a bunch and could send them out at-cost.
I also discovered that Mouser does in fact have a 9mm 1K/1K dual 50mW linear pot in stock in a different manufacturer, one without a picture showing.
I've missed finding that one until now because Mouser has it incorrectly listed as a "panel mount" pot instead of the actual PC mount. I've sent them a heads-up on their listing mistake. This one has a longer 20mm shaft though (vs. 15mm) and the shaft is smooth and slotted so would require a setscrew knob. Mouser shows the original Bourns pot arriving in just two weeks, but if anyone doesn't want to wait this pot with the longer shaft is Mouser #72-P9A2RFISX1BB2102M .
I'll be posting a revised BOM tonight on the Google Drive link with these listed as alternates.
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Ok I just updated my V2.0 ODA with a few things from the 2.1 version.
Changed C20 and C21 from 10uf to 22uf and added the transorb across the AC power input.
Easy to do, I needed to smell some fresh "flux" burning again! LOL.
The amp still works wonderfully and I am amazed still how well it performs with my Beyer T90's.
Absolutely amazing amp.
Alex
Changed C20 and C21 from 10uf to 22uf and added the transorb across the AC power input.
Easy to do, I needed to smell some fresh "flux" burning again! LOL.
The amp still works wonderfully and I am amazed still how well it performs with my Beyer T90's.
Absolutely amazing amp.
Alex
Yes please. Just send me what's needed for 3 boards and pm me for what I have to pay.
As I, sorry to say havn't found the time during the summer to order to get this going so I suggest that if you are thinking of creating a kit or need a 3'rd party test on the bom - gather what you think is best and send it to me at my expense. Of course I'll scream if there is something ridicolously priced😉
Regards
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Hey Turbon,
Yeah I have all the Digikey parts now, the LT regulators and the RCA jack. I'll send you a PM with an idea on the Mouser stuff.
Thanks agdr...
I might have been to optimistic about my fund level as I wrote "all 3 boards". I believe I'll start with one kit 🙂.
Regards
EU power transformer solution! And parts availability update.
I've come across a surprisingly easy and cheap solution to the AC-to-AC wall power transformers not being available in the EU anymore: 240Vac to 120Vac travel power converter transformers! I had assumed those would be expensive and bulky. Turns out not so for the 38W that the ODA's WAU16-2400 transformer requires. It is always recommended to double the rating for these conversion transformers, so minimum rating of 100W. With this solution then you would have one transformer, the WAU16-2400, plugged into another transformer, the travel 240vac to 120vac step-down converter.
This find also solves the problem about UL/CSA certification. As I've posted before I'm not willing to release a design with the AC wall power cord going directly to the box without it being UL & CSA certified. I've been through that certification fire drill in industry and it is expensive and time consuming, not something that could be justified for hobby work. But the travel converters are already certified. Problem solved!🙂
Here is one for $22 USD with a UK plug on the input side (and on a cord so it doesn't take up the whole outlet!) and a US plug on the other for the WAU16-2400 transformer. LiteFuze LC-100UK from this eBay vendor: Litefuze LC 100UK 100W Travel Voltage Converter Transformer Step Up Down UK | eBay
And here is a 200W rated unit with a EU 2 prong plug on a cord on the "input" side and a US 120Vac plug on the other for the WAU16-2400, a Simran SMF200 for $13.49 USD: http://www.amazon.com/Simran-200-Co...im_misc_3?ie=UTF8&refRID=18MN1RYKRK4Z4NBFSQ87 .
The only problem with this route is weight! The 200W unit on Amazon is 2lbs, so that might be pricier to ship, although as you can see even that is part of Amazon's Prime free ship program over a certain amount. If you have Amazon in your country maybe you can get it shipped directly to you.
And here is an update on part availability for the ODA project. Things keep bouncinng around. 🙂
* The 5.49K 1/8W through-hole resistors are now out of stock at Mouser. I have bought a bunch from another source though. If anyone needs them just let me know.
* The 1K/1K linear Bourns pots that Mouser had been showing with a shipping date of 9/8 are now showing a date of 9/24. Must have had a manufacturing delay. The Vishay alternate 1K/1K I posted about a few days ago had 38 in stock and now shows zero - someone bought them all! So until 9/24 my suggestion is back to using the 5K dual pot as a substitute.
* I've just bought the last red (1 of them) and green (2 of them) B4-080 cases in stock at Allied and Newark. If anyone wants those colors send me a PM. Apparently you can always order any of the colors directly from Box Enclosures on their website. They list the B4-080 in gold color too, which I've never seen in stock at the distributors, but I do have that same color in a B3-080 case and can say it is mightly nice! 😀
If anyone runs into any more parts-out-of-stock at Mouser please let me know.
I've come across a surprisingly easy and cheap solution to the AC-to-AC wall power transformers not being available in the EU anymore: 240Vac to 120Vac travel power converter transformers! I had assumed those would be expensive and bulky. Turns out not so for the 38W that the ODA's WAU16-2400 transformer requires. It is always recommended to double the rating for these conversion transformers, so minimum rating of 100W. With this solution then you would have one transformer, the WAU16-2400, plugged into another transformer, the travel 240vac to 120vac step-down converter.
This find also solves the problem about UL/CSA certification. As I've posted before I'm not willing to release a design with the AC wall power cord going directly to the box without it being UL & CSA certified. I've been through that certification fire drill in industry and it is expensive and time consuming, not something that could be justified for hobby work. But the travel converters are already certified. Problem solved!🙂
Here is one for $22 USD with a UK plug on the input side (and on a cord so it doesn't take up the whole outlet!) and a US plug on the other for the WAU16-2400 transformer. LiteFuze LC-100UK from this eBay vendor: Litefuze LC 100UK 100W Travel Voltage Converter Transformer Step Up Down UK | eBay
And here is a 200W rated unit with a EU 2 prong plug on a cord on the "input" side and a US 120Vac plug on the other for the WAU16-2400, a Simran SMF200 for $13.49 USD: http://www.amazon.com/Simran-200-Co...im_misc_3?ie=UTF8&refRID=18MN1RYKRK4Z4NBFSQ87 .
The only problem with this route is weight! The 200W unit on Amazon is 2lbs, so that might be pricier to ship, although as you can see even that is part of Amazon's Prime free ship program over a certain amount. If you have Amazon in your country maybe you can get it shipped directly to you.
And here is an update on part availability for the ODA project. Things keep bouncinng around. 🙂
* The 5.49K 1/8W through-hole resistors are now out of stock at Mouser. I have bought a bunch from another source though. If anyone needs them just let me know.
* The 1K/1K linear Bourns pots that Mouser had been showing with a shipping date of 9/8 are now showing a date of 9/24. Must have had a manufacturing delay. The Vishay alternate 1K/1K I posted about a few days ago had 38 in stock and now shows zero - someone bought them all! So until 9/24 my suggestion is back to using the 5K dual pot as a substitute.
* I've just bought the last red (1 of them) and green (2 of them) B4-080 cases in stock at Allied and Newark. If anyone wants those colors send me a PM. Apparently you can always order any of the colors directly from Box Enclosures on their website. They list the B4-080 in gold color too, which I've never seen in stock at the distributors, but I do have that same color in a B3-080 case and can say it is mightly nice! 😀
If anyone runs into any more parts-out-of-stock at Mouser please let me know.
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