There is a solution for that, but you will not like it!
One of the main reasons why LME49990 has better THD performance is that it has one of the highest GBW among "audio" chips, as a result you have a lot of feedback depth around an output stage or buffer. The other way of getting this is using the output buffer that has gain itself. A current feedback amplifier with sufficient output current can be a good option. In this case you get an additional freedom in choosing the front end part.
Beside that, THD graphs in datasheets are usually made for 2k load or something like that, while LME49600 is somewhat higher impedance load. While output of an opamp remains in class A, it is usually more linear. I suspect this will be true for your design.
Good points! Through the audio band the load on the op amp part of the booster board would be just about nil. I also see those THD+N graphs are all done at 3V.
I like current feedback amps! I think that TPA6120 headamp chip that jcx likes is current feedback. I was thinking about those once for the ODA amp.
Yep, TPA6120 is a current feedback guy. It is quite likely the same die as THS6012, but with a little bit more loose spec. In fact, my current headphone amp is built using this chip.
Although it is not exactly DIY friendly. It has a thermal pad, which requires some extra skills to solder, it has very high unity gain frequency, so it is quite demanding to PCB layout etc.
I think LT1206 or LT1210 can be an interesting alternative. They both have TO- 220 variant, so it is not a problem to solder. It also makes possible to make excellent heatsinking with pretty simple means. LT1210 has heaps of output current if needed. I even had a composite amp based on one working in HF channel in my multiamp. I do not remember it clipping
Here is one of possible variants, how it may look like and plot which shows total feedback depth (in two loops together) around the output stage. I'm pretty sure being properly assembled it will have very low level of distortion.
Although it is not exactly DIY friendly. It has a thermal pad, which requires some extra skills to solder, it has very high unity gain frequency, so it is quite demanding to PCB layout etc.
I think LT1206 or LT1210 can be an interesting alternative. They both have TO- 220 variant, so it is not a problem to solder. It also makes possible to make excellent heatsinking with pretty simple means. LT1210 has heaps of output current if needed. I even had a composite amp based on one working in HF channel in my multiamp. I do not remember it clipping
Here is one of possible variants, how it may look like and plot which shows total feedback depth (in two loops together) around the output stage. I'm pretty sure being properly assembled it will have very low level of distortion.
Attachments
I was able to repair my O2 by replacing the U3 socket I'm wondering if plugging and unplugging the booster board so many times caused the socket to fail? I still have a slightly higher dc offset on the right channel of .5mv but it's sounding great so I think I may leave well enough alone. I also built a new all stock O2 so it will be interesting to compare the two.
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I was able to repair my O2 by replacing the U3 socket I'm wondering if plugging and unplugging the booster board so many times caused the socket to fail? I still have a slightly higher dc offset on the right channel of .5mv but it's sounding great so I think I may leave well enough alone. I also built a new all stock O2 so it will be interesting to compare the two
That is interesting! I would guess that the socket contacts would be an all-or-nothing thing, but at the microvolt level maybe not. Couldn't hurt to spray some non-residue contact cleaner in them (like CRC QD cleaner CRC Electronic Cleaner, 11 Oz.: Motor Oil, Transmission Fluid & Car Lubricant : Walmart.com ) and on the booster board connection pins.
Sorry about the delayed reply! The last couple of weeks have been nuts.
Those are interesting chips! The ability to drive 10,000 pF loads and at least one has a high impedance output state which might do away with the need for a headphone relay.
I've had a couple of people PM with similar listening comments. The extra "burst" current capability of the LME49600's might be making a difference. Or maybe the low DC offset, or even the higher slew rate (although by the math it shouldn't, but who knows).
I see, how about the noise spectrum though? The 2.5k resistor may have noise in a totally different frequency area than the op-amp.
Even with very low specs there can still be spikes in certain frequency areas.
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If someone does a blind listening test of this versus the normal objective2 please put it on Youtube.
Then $500 is yours directly from NwAvGuy. I don't think anyone has done it yet.
I'm thinking it would be difficult to collect $500 from a guy that hasn't been heard from in over 2 years
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I'm thinking it would be difficult to collect $500 from a guy that hasn't been heard from in over 2 years
I suspect he wrote this article in November last year.
Introducing C5D, Amp+DAC | JDS Labs Blog
I would suggest reading these articles:
Johnson?Nyquist noise - Wikipedia, the free encyclopedia
Shot noise - Wikipedia, the free encyclopedia
White noise - Wikipedia, the free encyclopedia
Flicker noise - Wikipedia, the free encyclopedia
http://www.ti.com/lit/ml/sloa082/sloa082.pdf
Should give you a bit better understanding of the situation.
In other words noise(s) have very specific spectral density.
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NwAv
Hi there! Sure, I will read all these articles. Teacher.
I'm suggesting that NwAvGuy composed the article, perhaps it was posted in Jseaber's account.
"JDS LabsMarch 1, 2012 at 7:13 PM
Great work as always, NwAvGuy. We look forward to the final design!
We'd be glad to bid on the assembly job (15k board/day capacity). You have my contact info...
--JDS"
source: NwAvGuy: ODAC Update
When I read that C5D article the writing style very much reminded me of NwAvGuy.
The author is using the exact same Prism III dScope as NwAvGuy as well.
I think it's quite shameful that he kept on pushing the "total perfect transparency" idea, let alone the "non-commercial" idea, then he went commercial.
I suppose that could explain the silence.
At the same time I don't think it's fair that others should become rich on his intellectual property and time, so I'm happy for him.
Ultimately he should step forward though and say the O2 wasn't transparent at all and that he went commercial.
Just my views.
Hi there! Sure, I will read all these articles. Teacher.
I'm suggesting that NwAvGuy composed the article, perhaps it was posted in Jseaber's account.
"JDS LabsMarch 1, 2012 at 7:13 PM
Great work as always, NwAvGuy. We look forward to the final design!
We'd be glad to bid on the assembly job (15k board/day capacity). You have my contact info...
--JDS"
source: NwAvGuy: ODAC Update
When I read that C5D article the writing style very much reminded me of NwAvGuy.
The author is using the exact same Prism III dScope as NwAvGuy as well.
I think it's quite shameful that he kept on pushing the "total perfect transparency" idea, let alone the "non-commercial" idea, then he went commercial.
I suppose that could explain the silence.
At the same time I don't think it's fair that others should become rich on his intellectual property and time, so I'm happy for him.
Ultimately he should step forward though and say the O2 wasn't transparent at all and that he went commercial.
Just my views.
Hi there! Sure, I will read all these articles. Teacher.
Well, good luck with reading then! You may need the one
I really need to learn to leave well enough alone! That last little bit of dc offset on the right channel was bugging me and I started messing around with the board again and tried installing on my new O2 and it was working fine but still had a small amount of dc .3mV on the right channel so I tried reflowing some joints and cleaning the board and nothing helped so I decided to try some new opamps figuring maybe the one on the boarded been damaged. And that's where I really killed the booster board lol now I'm getting the full + rail voltage on the output of that channel! I have a bad habit of fixing things that don't need fixing. Luckily the O2 wasn't harmed and works fine. Just thought I'd share my story with you guys I found it a bit humorous after I got done cursing myself
For which you have no factual basis. As already pointed out, no-one has met his challenge, regardless of his availability.
Throw enough sh1t and some will stick eh?
If you have double-blind evidence of the fact that the O2 is not transparent, post it on YouTube, otherwise stop trying to snow the rest of the membership in support of your biassed position.
w
If I run into the chance, I'd love to scientifically blind test the O2 and upload it to Youtube. If I do, I'll try to remember you and let you know.
What is snowing on membership, btw?
A lot of the NwAvGuy blog is very, very nice and very informative.
However, paradoxically, a lot it is disinformative and leads novices astray, into a monochromatic fantasy land, where they will never hear the true fruits this audio science has to offer.
Just an example
"The note "A" above "Middle C" on a piano strongly resembles a 440 hz sine wave. It's a relatively pure tone at a single frequency. The wood structure, nature of the strings, hammers, etc. all slightly alter that 440 hz sine wave. A Stieinway grand might have a slightly faster attack, a longer decay and a different set of distortion products than a Yamaha grand. These subtle properties are well enough understood it’s possible to simulate the sound of different pianos using software"
From http://nwavguy.blogspot.com/2011/09/music-vs-sine-waves.html
There he is implying sound is so basic and so simple as usual, like all of sounds properties are well understood and we can simulate them.
In reality, there is currently no software which authentically simulates the best pianos in the world, it's all recorded https://www.propellerheads.se/products/refills/rpi/
Simulation sounds nothing like the real thing. How about synthetically simulated human voices? They sound nowhere near human. Anyone can hear that, unless they are sonically impaired on a neurological level.
Even in 2025 we will not be able to simulate human voices, I suspect.
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I have done blind testing with several people with the O2 and other amps. Headphone amps that cost much more and are highly touted and respected in the audio community. Our testing proved that no one could pick out the O2 amp from the others reliably.
The O2 amp is very transparent to me and many others regardless of what you might think about the designers blog etc.
There is more good information and discussion in his Blog than not. Even though he ruffled many feathers he, I think, has done more to get people to examine what their experience in this hobby really is. He exposed many fallacies and influenced some manufacturers to start posting meaningful specifications that in the past were hesitant to do.
I find there are many more positive's things in his blog than negative.
All the best...
The O2 amp is very transparent to me and many others regardless of what you might think about the designers blog etc.
There is more good information and discussion in his Blog than not. Even though he ruffled many feathers he, I think, has done more to get people to examine what their experience in this hobby really is. He exposed many fallacies and influenced some manufacturers to start posting meaningful specifications that in the past were hesitant to do.
I find there are many more positive's things in his blog than negative.
All the best...
That's the second time I've seen someone say they have performed blind testing, so respect to you.
I think in most cases it is blind faith.
I have been doing this audio stuff for 40 years now and have seen lots of claims and opinions, I do this testing to prove to me if there is a difference or not before I spend my hard earmed dollars etc...
I as many want stuff to sound better than other stuff especially when we are upgrading etc...or think we are upgrading...
I have listened to several amps in the last year that I have sold due to them not eing transparent.....
A.
I as many want stuff to sound better than other stuff especially when we are upgrading etc...or think we are upgrading...
I have listened to several amps in the last year that I have sold due to them not eing transparent.....
A.