Well there's no need to quote it all..
This thread is in the vendor bazaar part of the forums. It's a discussion between the vendor, owners, interested purchasers and anyone else who is a member of DIYaudio and interested in the topic. You have stimulated a number of unanswered questions. You've dragged Richard into the fray by posting his work.
Now there are a lot of people here interested in the answers. Fobbing them off isn't the right answer, especially if you plan on remaining part of the discussion here.
This thread is in the vendor bazaar part of the forums. It's a discussion between the vendor, owners, interested purchasers and anyone else who is a member of DIYaudio and interested in the topic. You have stimulated a number of unanswered questions. You've dragged Richard into the fray by posting his work.
Now there are a lot of people here interested in the answers. Fobbing them off isn't the right answer, especially if you plan on remaining part of the discussion here.
Yes and anyone is free to buy any commercial NC-500 based amp, mod it anyway they want, and measure every possible parameter. Colin's Nord one Up buffer is an excellent design for tweakers like those who hang out on this forum. 3lviz has been contributing awesome feedback of all of his opamp rolling results. I think it's that type of feedback that will be valued most. As far as Colin's new buffer revision, I think he has a handle on it.
I only communicate with Colin on this thread and the occasional PM. I have no idea what he's up to. But as far as I know the Hypex power supplies are backordered for a while anyways. So I imagine by the time he has more up for sale, he will have the newly revised board available. You can also check out his website as he puts updates on there sometimes.
http://www.iqspeakers.co.uk/#!blog/cv0ai
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OK I have the required parts on order, should arrive today and will modify the board as per Sonic Imagery's direction. I will then evaluate the result and make sure the new mods work with the Burson and Sparkos.
My findings are similar to Bavmike in the Sonic Imagery 994 does indeed sound very good a big thanks to him for his hard work in bringing this to our attention. 3D sound stage in particular is improved. I also had some other feedback from folks who have used the Op Amp who also agree. It is rather fragile in its build great care is required when changing Op Amps.
Longer term we will produce a new board either to accommodate these changes or a new design. Appreciate everybody's input so far as with out the interest there would be no point in doing all this.
I'm trying to keep my head above water while no Hypex stock building Speakers.
My findings are similar to Bavmike in the Sonic Imagery 994 does indeed sound very good a big thanks to him for his hard work in bringing this to our attention. 3D sound stage in particular is improved. I also had some other feedback from folks who have used the Op Amp who also agree. It is rather fragile in its build great care is required when changing Op Amps.
Longer term we will produce a new board either to accommodate these changes or a new design. Appreciate everybody's input so far as with out the interest there would be no point in doing all this.
I'm trying to keep my head above water while no Hypex stock building Speakers.
Colin, Thanks for the update, keep building those speakers and we all hope Hypex gets the NC500 modules back in stock quickly. Please keep us updated with your Rev C progress, and how you have conquered the noise issue with the SI 994, and your impressions of the 994 in your system compared to the others.
So... Measurements meets Inspiration. Sought of.
Bavmike trialed it and heard great things he took the effort to try, discover. He took the flak and to defend. Nerdman obviously measured everything when he was developing and designing his Sonic Imagery 994 Op Amp and probably to a lesser extent his fix for the Hypex circuit.
All I have done is combine the two skills and mod the board to meet these specs.
The early result and I say early, the noise has gone and well... I have had a few moments of HiFi heaven in the past but this, well.
I'm playing Pawn at the Sex Shop a superb live Jazz recording (not my norm) but was introduced to the album by a customer on a demo. I have Glockenspiel dancing inch's from my face left and right. I have a richness, a separation. The biggest improvement is the depth of image, utterly amazing. So the real cleaver technical guys have measured to create a technically excellent product all we did is come along and used these elements of well measured components to create a fine sounding product. How we measure the resulting sound enjoyment I wish I knew. So I'm trying to say both parties have a role to play here. Both elements of measurements are real, the final one subjective being my perception and my customers. I only finished modding both boards at around 9.30 tonight after trying one to see if the noise went. The other good news today is Hypex shipped my last order at around 4.30 I have emailed to enquire if it really happened and if they now have further stock of modules for me to purchase, no answer yet. A pretty good day. And all I can say is I wish you left and right could learn off each other It would make for a better place. PS I have had a few celebratory beers!
Bavmike trialed it and heard great things he took the effort to try, discover. He took the flak and to defend. Nerdman obviously measured everything when he was developing and designing his Sonic Imagery 994 Op Amp and probably to a lesser extent his fix for the Hypex circuit.
All I have done is combine the two skills and mod the board to meet these specs.
The early result and I say early, the noise has gone and well... I have had a few moments of HiFi heaven in the past but this, well.
I'm playing Pawn at the Sex Shop a superb live Jazz recording (not my norm) but was introduced to the album by a customer on a demo. I have Glockenspiel dancing inch's from my face left and right. I have a richness, a separation. The biggest improvement is the depth of image, utterly amazing. So the real cleaver technical guys have measured to create a technically excellent product all we did is come along and used these elements of well measured components to create a fine sounding product. How we measure the resulting sound enjoyment I wish I knew. So I'm trying to say both parties have a role to play here. Both elements of measurements are real, the final one subjective being my perception and my customers. I only finished modding both boards at around 9.30 tonight after trying one to see if the noise went. The other good news today is Hypex shipped my last order at around 4.30 I have emailed to enquire if it really happened and if they now have further stock of modules for me to purchase, no answer yet. A pretty good day. And all I can say is I wish you left and right could learn off each other It would make for a better place. PS I have had a few celebratory beers!
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I'd like to thank Colin for making his wonderful Nord One Up amps and Mike for helping him bring them to fruition. Mike recommend Nord to me when I was curious. I'm so happy I took a chance. I have the Sparkos op amps and enjoy them immensely. I am looking forward to the new 994 op amps and input boards for a different flavor.
Keep up the great work.
Keep up the great work.
Good News Boggit!
Could you please present measurements for SNR, THD, etc. once your board revision has completed?
Measurements should help give more objectivity to the performance of your product. That plus your case work and your custom buffer board and the affordability of the product should be great help in setting you apart from the competition.
I certainly hope you end up with a noise floor very close to -130db!
Good luck and success in your endeavors
Could you please present measurements for SNR, THD, etc. once your board revision has completed?
Measurements should help give more objectivity to the performance of your product. That plus your case work and your custom buffer board and the affordability of the product should be great help in setting you apart from the competition.
I certainly hope you end up with a noise floor very close to -130db!
Good luck and success in your endeavors
Will the new boards reduce noise levels with Sparkos and Burson where people have high efficiency speakers.
Be careful, Colin. In my experience, a few beers or glasses of wine seem to do wonders when it comes to perceived sound quality
Good to hear of the progress made
Be careful, Colin. In my experience, a few beers or glasses of wine seem to do wonders when it comes to perceived sound quality
Good to hear of the progress made
Same thing happens at my place!
Makes me appreciate the awesome sound even more after a few beers!
Sounds like those celebratory beers are going down very smooth! I haven't heard Pawn at the sex shop yet. Is that the late late late night version of Jazz at the pawn shop?
Is it also available in quad DSD? 
Yeah I was thinking screw DSD, the bluray version might be the best one with this album
I was planning to wait untill i get the Nord Rev C board, but i have to say that monolithic or discrete browndogged LME49990MA will be hard to beat. SI 994 is maybe has a bit more bass, the bass is very controlled tho, but the sound stage is bigger with LME49990MA. Very nice indeed. Not at all sensitive to be overly sibilant either. I think i like it better than the Sparkos and Burson.
If the LME49990 is operating in its typical THD behavior, that should be pretty acceptable too:
LME49990 | Precision Amplifier | Operational Amplifier (Op Amp) | Description & parametrics
LT1057 was also nice but i think the LME49990 is much better match. I think the finals will be SI 994 vs LME49990.
Colin, any news of the Rev C board? I see the SI 994 is added to the Nord One UP input board op amp selection, but the picture is of Rev B board. Confusing...
If the LME49990 is operating in its typical THD behavior, that should be pretty acceptable too:
LME49990 | Precision Amplifier | Operational Amplifier (Op Amp) | Description & parametrics
LT1057 was also nice but i think the LME49990 is much better match. I think the finals will be SI 994 vs LME49990.
Colin, any news of the Rev C board? I see the SI 994 is added to the Nord One UP input board op amp selection, but the picture is of Rev B board. Confusing...
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Great. I think this is your second observation whereby good specs have aligned with good performance. Note, however, the data sheet discussion of supply bypassing which is not accommodated by Colin's board. (Note also the discussion regarding load capacitance.)
I had thought Colin felt that he could make the proposed changes within the structure of the existing board. You could too.
BTW if one did have the SI 994 one might give thought to lowering the feedback resistor values. The reason they are what they are now, besides to achieve the required gain, is because they present a load which 'fits' within the output current capabilities of the LM4562. If the SI 994 is capable of much greater output current then the feedback resistors can be lowered with a consequent improvement in noise because these resistors are the largest noise source within the circuit.
I had thought Colin felt that he could make the proposed changes within the structure of the existing board. You could too.
BTW if one did have the SI 994 one might give thought to lowering the feedback resistor values. The reason they are what they are now, besides to achieve the required gain, is because they present a load which 'fits' within the output current capabilities of the LM4562. If the SI 994 is capable of much greater output current then the feedback resistors can be lowered with a consequent improvement in noise because these resistors are the largest noise source within the circuit.
I am gonna try bypass caps on the LME49990's and maybe some other opamps i have here too. 10uF silmic 2s' which seem to be the "popular" cap for this purpose.
However, after several hours of playing music, the LME49990 were only lukewarm to my finger, so i suppose they are not suffering especially bad.
The LME49990 spec sheet says the following:
"
SUPPLY BYPASSING
To achieve a low noise and high-speed audio performance, power supply bypassing is extremely important.
Applying multiple bypass capacitors is highly recommended. From experiment results, a 10μF tantalum, 2.2μF
ceramic, and a 0.47μF ceramic work well. All bypass capacitors leads should be very short. The ground leads of
capacitors should also be separated to reduce the inductance to ground. To obtain the best result, a large
ground plane layout technique is recommended and it was applied in the LME49990 evaluation board.
"
Three caps per LME49990? No way... I am gonna try this one and depending on the results, maybe more. It already feels like fixing things that are not broken.
However, after several hours of playing music, the LME49990 were only lukewarm to my finger, so i suppose they are not suffering especially bad.
The LME49990 spec sheet says the following:
"
SUPPLY BYPASSING
To achieve a low noise and high-speed audio performance, power supply bypassing is extremely important.
Applying multiple bypass capacitors is highly recommended. From experiment results, a 10μF tantalum, 2.2μF
ceramic, and a 0.47μF ceramic work well. All bypass capacitors leads should be very short. The ground leads of
capacitors should also be separated to reduce the inductance to ground. To obtain the best result, a large
ground plane layout technique is recommended and it was applied in the LME49990 evaluation board.
"
Three caps per LME49990? No way... I am gonna try this one and depending on the results, maybe more. It already feels like fixing things that are not broken.
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I suspect all that means is that you're not driving the output current much (as expected unless you like really, really loud music).
BTW Colin, was it Hypex that told you to use a 10A fuse? A huge amount has to go wrong before a 10A fuse (230V nominal supply) will blow and save the equipment downstream of it.
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