ODA Headphone Amp

adydula · « **Reply #40 on:** 16 Jun 2014, 07:03 pm »

Just soldered in a SMD 4556 surface mount op amp to wire up the front panel RCA output jacks, They are set to unity gain buffer amp..so I can drive the AVR I have to drive a set od those great little Pioneer Speakers we all raved about the 22's...

Its working just great !!

Alex

agdr · « **Reply #41 on:** 18 Jun 2014, 10:54 pm »

I've joined the forum.

Alex let me know about this thread. He did a great job with his ODA build!

adydula · « **Reply #42 on:** 21 Jun 2014, 02:40 am »

FYI....

The electrical engineer and designer of the ODA I just built in this thread has registered as a member of audiocirle.com He is waiting for the web meister to approve him so he can post.

It will be really nice to have a really smart and intelligent engineer on board here to discuss this amp.

I think he has done a marvelous job on this amp and can answer questions about it way better than I can...in depth.

Please welcome him aboard!!

Alex

adydula · « **Reply #43 on:** 22 Jun 2014, 02:36 pm »

Hey,

After being on now for a few days here are the temps I have measured with a thermocouple:

Front Panel 3.5mm jack: 88 degrees F. Inside about 1/2 inch its 90 deg F

Front Panel RCA Jack: 86 deg F

Front Panel Screw Upper Right Corner: 85 deg F

Top middle case: 87 deg F

Side center/middle case: 85 deg F

Rear Panel Middle Regualtor screw : 89-90 deg F

Front panel 1/4" jack internal about 1" insertion to back of jack : 93 deg F

The entire rear panel is relatively uniform in temp distribution.

Then entire case is relatively uniform in temp distribution as well.

I have no ventilation holes in my build.

I think I will add the holes / slots in the back panel to see how well that goes.

My gut thinks not that much.

I also had a 1/4 headphone plugged into the 1/4 jack all the time except when I measured the internal temp there. So this precluded any air entering that opening.

All in all the case is slightly warm at a 88-89 temp etc.

All the best
Alex

jtwrace · « **Reply #44 on:** 22 Jun 2014, 02:39 pm »

All interesting info but still waiting....

adydula · « **Reply #45 on:** 22 Jun 2014, 10:34 pm »

Well it shouldn't be too much longer!!

Alex

agdr · « **Reply #46 on:** 26 Jun 2014, 02:39 am »

I'm afraid the holdup is me.

I've been pretty much nailed with the day stuff the last couple of weeks. I did get some holes drilled in the back panel today. Those are for ventilation. I have one with the existing panels but the new rear panel CAD will have holes in them. I'm hoping to get the ODA mailed off for testing in the next few days.

agdr · « **Reply #47 on:** 26 Jun 2014, 06:46 pm »

An ODA is now in the mail for dScoping.

jtwrace · « **Reply #48 on:** 26 Jun 2014, 06:59 pm »

Quote from: agdr on 26 Jun 2014, 06:46 pm

An ODA is now in the mail for dScoping.

adydula · « **Reply #49 on:** 26 Jun 2014, 08:16 pm »

There ya go Jason!!!

LOL.

It will be interesting!

I was thinking when the O2 came out and NwAvGuy presented to the audio world its measurements, many people didn't necessarily believe how well or how good this amp "did not" sound. ie totally transparent etc.

No matter how it measures compared to the O2 standard which some love and hate, compared to the O2's I have its at least as good sonically to me.

Alex

adydula · « **Reply #50 on:** 27 Jun 2014, 12:34 pm »

FYI,

If anyone is interested in a PC board etc to build one....PM AGDR directly.....I know he is working on a V2.1 board and several people are on a list for this pc board.

Alex

adydula · « **Reply #51 on:** 12 Jul 2014, 10:29 pm »

Just an update an oda has been shipped to Mike G. and we are waiting on his testing. He is a busy guy and we do appreciate his assistance in this measuring.

Also agdr has finished on a version 2.1 of the ode pc board. He has ordered some and several people have asked for one from him. He also has started a version 3.0 wish list for a possible future 3td version of the oda. Details can be found at diyaudio.com. You can submit ideas or requirements if you like.

I am still very much enjoying my ode and am thinking of building a second one and possibly selling the one I have working now.

As soon as we get results from Mike he should post here.

All the best
Alex

agdr · « **Reply #52 on:** 13 Jul 2014, 11:38 pm »

Thanks Alex!

Here are the changes in ODA V2.1 from V2.0.

https://drive.google.com/folderview?id=0B67cJELZW-i8OXpvVTh1U21RMFE&usp=sharing

None of these are likely to make any audible difference. They are just things that make the build easier and may make a tiny bit of difference with sensitive dScope / AP measurements. Also on Sept. 15th Mouser will start carrying the next generation of the type of caps used for C11 and C12. These are 25mm tall vs. 30mm at present (tallest thing on the board). They will be same height as the other two 1000uF filter caps, leaving a good 5mm of spacing to any boards inserted in the case top board slot.

The ODA is a DIY project. I'll have to check about the rules on this forum, but the boards I've sent out to fabrication will be sold at-cost. The details are in the "next board run" folder here, under 80 x 160 -> 3_19_2014 V2.0:

https://drive.google.com/folderview?id=0B67cJELZW-i8VmhVNk5PODNtZnc&usp=sharing

I'm starting to put together a V2.1 folder now with the schematics, layout, build instructions, build photos, BOM, etc. I'll also post the Gerber files (as I've done for the existing V2.0) so anyone can send their own boards out for fabrication. The minimum order from the fabrication outfits is typically 5 boards which is why I've been doing one round of at-cost board sales, to help out with the DIY effort.

The only parts on the PC board not available from Mouser are the LT LDO voltage regulators. I'm also going to have those available at-cost (from Digikey) so folks won't have to make a separate order to Digikey for just 2 parts. Plus any other parts in the ODA that Mouser is out of stock on at the moment.

mgalusha · « **Reply #53 on:** 14 Jul 2014, 10:25 pm »

Quote from: adydula on 12 Jul 2014, 10:29 pm

Just an update an oda has been shipped to Mike G. and we are waiting on his testing. He is a busy guy and we do appreciate his assistance in this measuring.

I have the amp and it survived the journey but unfortunately I didn't have what I consider proper loads for it. I build an adjustable load box but the resolution was not accurate enough to suit me, some .05% precision loads are on order and have shipped, with any luck I will have them in a few days and hopefully can get the measurements desired.

mg

adydula · « **Reply #54 on:** 15 Jul 2014, 11:46 am »

Thanks for the update Mike!!

I haven't asked this directly to AGDR, so he probably has discussed what measurements that he is looking for etch. I was re-reading the NwAvGuys O2 blog this am and in the tech section he has a list of measurements in a table/chart, then follow-on graphs of these measurements in the chart/table below and discussions on the results. Here is the table:

I am assuming these are the measurements you are trying to perform?

Alex

PS: Of course the battery life wouldn't apply!! Lol....

tubesguy2 · « **Reply #55 on:** 15 Jul 2014, 01:28 pm »

Quote from: agdr on 13 Jul 2014, 11:38 pm

The ODA is a DIY project. I'll have to check about the rules on this forum, but the boards I've sent out to fabrication will be sold at-cost. The details are in the "next board run" folder here, under 80 x 160 -> 3_19_2014 V2.0:

https://drive.google.com/folderview?id=0B67cJELZW-i8VmhVNk5PODNtZnc&usp=sharing

For those not well-versed in Google documents, how does one change/edit/add a name to the list? Thanks - Pat (tubesguy)

adydula · « **Reply #56 on:** 15 Jul 2014, 02:22 pm »

Hey Pat...

If you want a pc board I would pm agar directly here at this site.

Fyi
Alex

tubesguy2 · « **Reply #57 on:** 15 Jul 2014, 03:21 pm »

Thanks, Alex, will do. - Pat

adydula · « **Reply #58 on:** 15 Jul 2014, 04:31 pm »

Pat if you already haven't done so there is a wealth of information on the ODA and how it came to be and the development of it etc..over at diyaudio.com. I have as well as agar posted many pictures and details during the build.

Many issues were discovered. Mainly errata in the BOM and or build instructions. Nothing really major.

If your planning on building one in the future I would be glad to help in anyway we can etch..

Also AGDR is a swell person that really enjoys the DIY stuff and is a great electrical engineer that would also be glad to assist etch..

All the best
Alex

agdr · « **Reply #59 on:** 16 Jul 2014, 01:58 am »

Quote from: tubesguy2 on 15 Jul 2014, 01:28 pm

For those not well-versed in Google documents, how does one change/edit/add a name to the list? Thanks - Pat (tubesguy)

Yep, Alex is right, PM me and I'll add you and send you some info.

Alex - the main set of dScope parameters I'm interested in are the graph under "THD + N vs. Output & max power on AC" on NwAvGuy's blog here:

http://nwavguy.blogspot.com/2011/07/o2-headphone-amp.html

If Mike is able to measure some or all of those it would be fantastic!

Edit: 7/16/2014. I'm sticking with the 1K pot after all. The datasheet for the LME49990 gain chips has THD+N graphs for a 600R load with +/-5V, +/-15V, and +/-18V power rails. I've been having to scratch my head a bit extrapolating to +/-12.5V. I wish they had included a +/-12V graph! It looks like the chip has about 1V of "spacing" between where a big rise of distortion sets in and the point where the wave top actually goes flat and clips on a scope. That is the big vertical rise at about 8.5Vrms output swing on the datasheet figure 7 from the minimum THD+N of 0.000005% or so they show. I was concerned that "spacing" might be more like 3 or 4 volts, but from the graphs I'm now satisfied it is only about a volt or so.