Joe,
I was not aware what software / hardware you were using.
I think that this does not really have enough resolution to measure a VHQ DAC
like Sabre. What are the base line / loop through performance specs?
cheers
Terry
The Oppo I have here that has OPA-860 fitted, I am about to remove and do one of my full Level 3 upgrades - in fact really busy right now. But I have a test CD with some 1KHz, 10KHz & 20KHz sine waves, which gave the following results:
0dBFS - 1KHz 0.071%
0dBFS - 10KHz 0.137%
0dBFS - 20KHz 0.000% - sampling rate not high enough
-20dBFS - 1KHz 0.096%
It is largely even order distortion. Please keep in mind that this would be lower distortion than OPA-660 which has no internal feedback around the buffer and the OPA-860 that has a current feedback opamp as buffer. Then lower THD is not necessarily better. But it is the only option if the requirements that were set out was meant (current production, SOIC etc). There is, as the schematic shows, no overall feedback other than around the internal buffer.
I hope you build it as it works very nicely indeed.
Cheers, Joe
.
Thanks, for taking the time to provide those measurements, Joe.
Yes, I think I will experiment with the OPA-860 in voltage amplification mode.
I did put on a standard (not upgraded) stereo output (opamp based I/V etc) Oppo 105 and no doubt the THD is a lot lower, but I can see significant odd order distortion products and peaks at 5th and 10th. You can also wee some 7th (arguably the one to keep an eye at), but and less but some 9th. The sound is nowhere near the same. The best sounding scheme is when you have a naturally cascading distortion, where 2nd dominate 3rd, and 3rd dominate 4th, and 4th dominate 5th etc, a kind of waterfall, and even if THD overall is much higher, it will still sound better and cleaner. That 'waterfall' characteristic was mentioned as favourable way back by Jean Hiraga. Here we have an example that looks nothing like that, but you wouldn't expect that. Feedback may well lower THD but do little for higher up odd order products and just usually make those worse. Much of this has of course been observed before.
Cheers, Joe
.
Joe,
What's your assessment of the ultimate usability of the OPA-860's built in current-feedback buffer stage. Do you find it subjectively transparent, or rather, does it audibly detract from the OTA section's quality? In other words, in your opinion, would it be worthwhile for me to to bypass it, and add an external buffer stage?
What's your assessment of the ultimate usability of the OPA-860's built in current-feedback buffer stage. Do you find it subjectively transparent, or rather, does it audibly detract from the OTA section's quality? In other words, in your opinion, would it be worthwhile for me to to bypass it, and add an external buffer stage?
The internal buffer is quite OK, but if you know a good zero feedback buffer I would be inclined to look at OPA-861 OTA only, into the buffer of your choice, whether discrete or based.
The use of the OPA-860 in my example, was to demonstrate how Oppo could, in the most simpledt way with types of components they were already using, could majorly improve the stereo outputs of the Oppo from scratch and get away from the typical opamp circuits and yet still use an available SOIC device.
But for DIY purposes, we are not that way limited. You might want to hunt down some obsolete OPA-660 as they have a proper straight buffer - as John Curl said, the replacement OPA-860 is inferior.
But OPA-861 plus your own separate buffer? That's the other option.
Cheers, Joe
PS: Keep in mind that OPA860-861 works only with 5V and a separate buffer may need a lot more, so PS is more of a problem... makes OPA-660 also look pretty good for only single supply voltage.
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Thanks Joe,
That's around what I would expect from an open loop connected OTA gain
stage such as the OPA860/880 / AD844 type opamps.
If you use them as I-V for a DAC like PCM1704 where the OP Z is much higher
and the current swing is lower, they will get much lower distortion and then
stacking will improve this further - as George has found with stacked 844 IV.
The worse 10kHz distortion is indication of internal chip capacitances - they
also degrade the sound somewhat. Another form of distortion in these open
loop circuits is thermal distortion. This is difficult to measure with sine wave
measurements but when you reduce it the sound also improves - sometimes
quite a bit.
The worse distortion at -20dBFs is indicating quite high noise which is actually
rising above the distortion.
Yes it's a good solution for quick and easy I-V.
I don't really have a way to measure my I-V, however in the development I
did a lot of spice modelling to find best operating points.
A major focus was to be able to deal with HF content of DS DAC's like 9018.
So important criteria were:
a/ no feedbacky open loop (discrete) design,
b/ very low high frequency distortion
c/ Low thermally induced distortions.
d/ Transformer interface to following equipment.
Ref to pics below of the initial ltspice simulated results without transformer.
20kHz / 200kHz / 2MHz (yes that's 2MHz)
These FFT's show very low THD, even at 2MHz it is very low. The design
is such that thermal distortions are cancelled to a large degree.
In real life these types of numbers would not be achievable but allowing for a
factor of 10 x or so and as you can see the design is very good.
You have to be careful as it looks like you might be measuring distortion of the
test set itself. A decent Sabre 9018->opamp I-V can easily measure lower
than your test sets baseline.
Attachments
Ken,
Can't say too much at this stage but it presents a <1ohm impedance to DAC,
has no coupling caps, has high current OP buffer direct coupled to a
mammoth nickel core transformer. The transformer can drive any load /
unbal / bal with full galvanic isolation.
The design has a unique feature that self cancels distortion without any use
of feedback / feed fwd / EC etc - as such it also cancels thermal modulation
based distortions. However even without the cancellation part it still has very
low distortion for open loop (around 0.003 or so).
It will also preserve the full DR >130dB of ES9018.
Z
Just real quick here; we talked about Darbee a week ago or so: Oppo BDP-103D 3D Blu-ray Player | Sound & Vision
I have owned the BDP-105 for a year but still dis-satisfied with the sound. The cymbals and high freq sounds are very harsh. The other day I used a Peachtree Decco65 driving by coaxial from the 105 and the sound was much improved as the harshness was gone and cymbals resonance was distinct and delicate. Switching to analog output from the 105
have the same harshness as before. It seems that the Peachtree DAC output was smoother. Does anyone experience this problem. Does anyone know if the 105 upsamples 44.1 to a higher rate 88.2/96/192 or have a mode to set. The DAC datasheet indicated upsampling but does gives detail.
have the same harshness as before. It seems that the Peachtree DAC output was smoother. Does anyone experience this problem. Does anyone know if the 105 upsamples 44.1 to a higher rate 88.2/96/192 or have a mode to set. The DAC datasheet indicated upsampling but does gives detail.
That`s why one (quite many at least...) will want (should) modify this player... I just wonder if this player it may be the most modified consumer device... Its hardware is very capable, but the design are in the modders favour...
Can I ask a question please: I have been using the HDMI output of my 105 because for some formats the coax output is not enabled (copyright stuff and such).
This works, but I was just reading another thread where someone had done jitter measurements on an AV receiver. His findings were that the jitter on the HDMI audio was almost ten times the jitter on the coax (S/PDIF) output!
Has anybody here done similar measurements on the 105?
Jan
This works, but I was just reading another thread where someone had done jitter measurements on an AV receiver. His findings were that the jitter on the HDMI audio was almost ten times the jitter on the coax (S/PDIF) output!
Has anybody here done similar measurements on the 105?
Jan
Hi CorisThat`s why one (quite many at least...) will want (should) modify this player... I just wonder if this player it may be the most modified consumer device... Its hardware is very capable, but the design are in the modders favour...
I scan through the tread but as it is very long, haven't find the answer. There are suggestion to remove the DC output cap but what is the different in sound quality? There are also discussion to replace the opamp but I wouldn't want to do such modes. It seems better to get external DAC but that defeats the purpose of going with 105 in the first place
Hi ltlee
Well, there are many suggestions about what one can do with a Oppo 105 player...
I will take this opportunity here (your questions) to precise/clarify something about these mods.
To be very honest, if you have a standard player (Oppo 105 in this case), and you will remove the DC isolation caps, you will not hear any or a big difference. The same it may happen if you only replace the original opamps with something else. Or in this last case the perceptual improvement it will quite small.
The mods in this player, and mods in general are to be seen as a kind of complex task. One may proceed to a complexity of small mods to get the improvement one it expect.
This Oppo player as it is it have quite much potential to be a top high end device. For commercial or other reasons it is not so as it can be.
One may not only do a simple mod on it, and then expect spectacular improvements. You may change the caps on outputs, but what about a noisy SMPS, or an not enough filtered analogue PSU, which it rest in place? What about consumer quality components as the oscillators are in this model, and so on?
There is another aspect here. One may proceed to some or all the necessary mods on a device. This task is quite expensive, and consume lot of time, and much work. Is this worth?
With that money one use and the costs of the time involved in such modification task, it can one very well buy a higher class product, and could be happy so...
I`m not intend to analyse (psychoanalyse) what it may be the reasons some prefer to invest time an money to have a top quality device. But is just like this. Some are doing so...
The main point here is that one may understand that the mods are connected in between one with another, and the whole complex of the work it may bring improvements, but not only part of these.
If one may start to mod a device, I can suggest here some points.
First is to take a look at the power system. There are two ways to appreciate how and what it may be wrong or well in a designed power system. One may measure a lot, and conclude quite precise what is to be modded. Or one may have enough experience to appreciate just at once what it have to be done.
With an improved power system one may see or hear some small improvements...
Then can one remove (f. ex. ) the caps on outputs, and appreciate quite objective how much improvement it come out.
But before trying to remove the caps, one may take a closer look at the clock system in the device, and its PSUs. Here is enough to replace the original oscillators with some better devices to get quite much improvement.
Then it may be taken a look at the audio system (caps, opamps, and so on).
I can say that I personally did not done my mods in this sequence. But after lot of work, I concluded that this is the right way to be done.
So, you can very well let in place the caps, and try to improve the power system of the player. But be prepared that such enterprise is not easy, need lot of time and work. And most important, skills, knowledge and enough experience. Or (another alternative) think and appreciate if is not easier to buy a higher class device... At least the price it may be quite similar...
If you are interested most in audio stage of the player, and if you may appreciate that buying a better device it may be a better solution for you, then I will suggest to wait a little bit more to come out the Oppo`s headphone amplifier. This device it is a USB DAC too. It is expected that Oppo have improved some parts of their design, so I think this product it may be a good one (for only audio use).
Of course you can (very easy) remove the caps and hear/appreciate yourself what is the result. This appreciation is very individual, is enough subjective and in the same time is not easy to be described by words. So, do it yourself it is also the main line of this forum...
Well, there are many suggestions about what one can do with a Oppo 105 player...
I will take this opportunity here (your questions) to precise/clarify something about these mods.
To be very honest, if you have a standard player (Oppo 105 in this case), and you will remove the DC isolation caps, you will not hear any or a big difference. The same it may happen if you only replace the original opamps with something else. Or in this last case the perceptual improvement it will quite small.
The mods in this player, and mods in general are to be seen as a kind of complex task. One may proceed to a complexity of small mods to get the improvement one it expect.
This Oppo player as it is it have quite much potential to be a top high end device. For commercial or other reasons it is not so as it can be.
One may not only do a simple mod on it, and then expect spectacular improvements. You may change the caps on outputs, but what about a noisy SMPS, or an not enough filtered analogue PSU, which it rest in place? What about consumer quality components as the oscillators are in this model, and so on?
There is another aspect here. One may proceed to some or all the necessary mods on a device. This task is quite expensive, and consume lot of time, and much work. Is this worth?
With that money one use and the costs of the time involved in such modification task, it can one very well buy a higher class product, and could be happy so...
I`m not intend to analyse (psychoanalyse) what it may be the reasons some prefer to invest time an money to have a top quality device. But is just like this. Some are doing so...
The main point here is that one may understand that the mods are connected in between one with another, and the whole complex of the work it may bring improvements, but not only part of these.
If one may start to mod a device, I can suggest here some points.
First is to take a look at the power system. There are two ways to appreciate how and what it may be wrong or well in a designed power system. One may measure a lot, and conclude quite precise what is to be modded. Or one may have enough experience to appreciate just at once what it have to be done.
With an improved power system one may see or hear some small improvements...
Then can one remove (f. ex. ) the caps on outputs, and appreciate quite objective how much improvement it come out.
But before trying to remove the caps, one may take a closer look at the clock system in the device, and its PSUs. Here is enough to replace the original oscillators with some better devices to get quite much improvement.
Then it may be taken a look at the audio system (caps, opamps, and so on).
I can say that I personally did not done my mods in this sequence. But after lot of work, I concluded that this is the right way to be done.
So, you can very well let in place the caps, and try to improve the power system of the player. But be prepared that such enterprise is not easy, need lot of time and work. And most important, skills, knowledge and enough experience. Or (another alternative) think and appreciate if is not easier to buy a higher class device... At least the price it may be quite similar...
If you are interested most in audio stage of the player, and if you may appreciate that buying a better device it may be a better solution for you, then I will suggest to wait a little bit more to come out the Oppo`s headphone amplifier. This device it is a USB DAC too. It is expected that Oppo have improved some parts of their design, so I think this product it may be a good one (for only audio use).
Of course you can (very easy) remove the caps and hear/appreciate yourself what is the result. This appreciation is very individual, is enough subjective and in the same time is not easy to be described by words. So, do it yourself it is also the main line of this forum...
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What do you guys think about HDMI; like version 1.4a, 1.4b, 1.4c, and 2.0 or lower? ...1.3a, 1.3b, 1.3c, etc.
Can it me modified to look and sound better?
And why do we have to always buy another player for the latest support version?
Can they just not make this goddamn HDMI thing upgradeable through firmware updates?
I've been thru them all; 1.0, 1.1, 1.2, 1.3, 1.4, and each time I had to buy another player, another SSP (pre/pro), and another goddamn TV!
Now comes HDMI v.2.0 (Ultra HDTV)! ...And everything has to be repurchased all over again!
Was HDMI invented by the audio/video manufacturers to make more money, and irritate the entire planet with their handshake issues?
Hey, the Oppo 105 has two HDMI outputs and two HDMI inputs.
Can it me modified to look and sound better?
And why do we have to always buy another player for the latest support version?
Can they just not make this goddamn HDMI thing upgradeable through firmware updates?
I've been thru them all; 1.0, 1.1, 1.2, 1.3, 1.4, and each time I had to buy another player, another SSP (pre/pro), and another goddamn TV!
Now comes HDMI v.2.0 (Ultra HDTV)! ...And everything has to be repurchased all over again!
Was HDMI invented by the audio/video manufacturers to make more money, and irritate the entire planet with their handshake issues?
Hey, the Oppo 105 has two HDMI outputs and two HDMI inputs.
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First of all, you need to tell us a little more about your system, what type of music you want to play, and what your skill level is. Maybe you will end up buying the Peachtree unit.
In terms of testing, I would suggest that you use an SACD, or some other high-resolution modern high quality recording. If possible you should also listen to the unit using 300 ohm headphones such as Sennheiser HD 650 (This will sound very nice).
One possibility is that you have not set the unit up properly. There is more information about this on the owners forum. There are many ways to go wrong. When playing the SACD, be sure that DSD is indicated, and that no processing is active. Unhook unnecessary USB or HDMI cables.
Another avenue is to ensure that clean power is being provided to your system, and that you are using adequate power line filtering, both for your player and your amplifier or preamp.
Have you listened to other stand alone SACD players such as Marantz? What is your budget?Are you using the unit single channel or multichannel, and what formats do you need to play?
The unit will sound best from the balanced outputs, and playing very high quality high-resolution material.
In terms of modifications, most of the people on this forum are interested in modifying their player to make it sound better. This can be done at various levels of intensity. At the simplest levels you could do the following:
Bypass the output coupling capacitors, and install SMD 10 µF ceramic capacitors onto the DAC power pins. Unhook the multichannel board if you're not using it.
Then, you could choose from: add shielding, vibration damping, vibration isolators, replacing diodes, power supply bypassing. Transformer coupling can also reduce high-frequency noise transmission.
This should take you pretty far, but remember that the unit is inherently on the neutral and revealing side of the equation.
More elaborate modifications could include new IV converter, doubling up the DAC lines, improved power supplies, improved clocks etc.
Welcome to the forum,
Eric
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