Resirrection
Hi,
There's still something fishy with the measurements of one of the resistors on it, it's off alot in value compared to the other module.
If I'm not mistaken I'd noticed that before and it could just be a selection error as part of the input RF filter and also why one amp experiences more RF than the other module, or at least did before going with fully balanced inputs.
While far less than ideal I guess ... in terms of mere operation alone you could call it non critical/ as good as before.
The problem was ironically enough solved by locating a small terminating resistor in series with the emitter leg of the pass transistor in charge of the -5V supply that had become high impedance at ~1K.
That'd let the negative supply sag creating a heavy DC imbalance on the output and the thumping experienced is the annoyance of a self resetting protection circuit doing its thing.
Haven't tried it with music yet, but voltage was restored by the removal of the .01 or 10ohm emitter reistor and shorting the pads with a length of wire wrap wire. It now enables the output stage with no more an audible click than before the incidence.
It seems like a strange and unrelated component to have failed in terms of the prior issue of a broken filter coil solder joint, along with being the same module that had the other problems.... must be the one that got dropped while trying to save the donut.
Never did get that email Lars, but if you still want the modules returned, no problem, how about I just wait until those production ones get here 🙂
Cheers,
Chris
Hi,
There's still something fishy with the measurements of one of the resistors on it, it's off alot in value compared to the other module.
If I'm not mistaken I'd noticed that before and it could just be a selection error as part of the input RF filter and also why one amp experiences more RF than the other module, or at least did before going with fully balanced inputs.
While far less than ideal I guess ... in terms of mere operation alone you could call it non critical/ as good as before.
The problem was ironically enough solved by locating a small terminating resistor in series with the emitter leg of the pass transistor in charge of the -5V supply that had become high impedance at ~1K.
That'd let the negative supply sag creating a heavy DC imbalance on the output and the thumping experienced is the annoyance of a self resetting protection circuit doing its thing.
Haven't tried it with music yet, but voltage was restored by the removal of the .01 or 10ohm emitter reistor and shorting the pads with a length of wire wrap wire. It now enables the output stage with no more an audible click than before the incidence.
It seems like a strange and unrelated component to have failed in terms of the prior issue of a broken filter coil solder joint, along with being the same module that had the other problems.... must be the one that got dropped while trying to save the donut.
Never did get that email Lars, but if you still want the modules returned, no problem, how about I just wait until those production ones get here 🙂
Cheers,
Chris
Hello,
It exploded again! No sorry for those who'd wish such a thing, I'm playing it on some sound dymanics or something, efficiency so poor I can crank them pretty good and the power is there to make the place rumble like crazy.
Also the heterodyning isn't as apparent, really on these speakers, it's the only thing you hear with the computer turned off.. aside from a bit of a mechanical hum that I'm sure it never had before, must be a high dc period on the line.
Bottom line right now is that they work, and once you get past the technical difficulties I've had, all of which I think are the attributable to their being handbuilt prototypes, I still dislike the HF coloration the FC bypass caps impart but resolution, SNR, clearity, all very good. Frequency response seems flat, gutteral bass .... handles the power very well, though idle current is high so it gets hot at low output.
Pieces say for instance instrumentals with alot of air come off fairly convincing in realism, height and depth, but I wouldnt' call the soundstage enveloping enough so as to be completely holographic, though frighteningly enough it still seems to achieve it the odd time.
In its own way it's become far less intolerant of poor recordings and low quality bitrates, just in that it's so much less lifelike and you're likely to tire listening to that after very long. Feed it something good from a soundtrack for instance and it really fires it out there.
I'd think with more natural sounding bypass caps than FC's, it could be more holographic still and in terms of how well the soundstage is able to surround you it's probably a good idea to pay attention to speaker placement to get the most of it.
Imaging may improve further by synching the modules since they're so close to one another and they're not the lowest in EMI , as well as going true full mono with some physical seperation between them.
I'd say the area it impresses most is that it has no real apparent edge on anything. The decay is mostly in time across the band, very tight, super clear, precise micro-dynamics. While I'd still say it's more analytic than before, and lost alot of that heavily smoothed fingerprint, it is able to manage it fluidly and musically, can't at all consider this cold.
Biggest downside, not the best SNR when driven single ended, balanced really makes a huge difference and I strongly recommend it if you are able, and plan on lots of ventilation as well because they cook pretty good at idle, and I imagine that will also be true of the production modules if they're tuned to spec.
Cheers,
Chris
PS: It's also very likely a more serious transformer would further open up soundstage in every aspect including holography. I'm now looking forward to seeing how post feedback filter affects it all as well too, and am able to attempt it whenever. 😉
T., looks like you were right again.
It exploded again! No sorry for those who'd wish such a thing, I'm playing it on some sound dymanics or something, efficiency so poor I can crank them pretty good and the power is there to make the place rumble like crazy.
Also the heterodyning isn't as apparent, really on these speakers, it's the only thing you hear with the computer turned off.. aside from a bit of a mechanical hum that I'm sure it never had before, must be a high dc period on the line.
Bottom line right now is that they work, and once you get past the technical difficulties I've had, all of which I think are the attributable to their being handbuilt prototypes, I still dislike the HF coloration the FC bypass caps impart but resolution, SNR, clearity, all very good. Frequency response seems flat, gutteral bass .... handles the power very well, though idle current is high so it gets hot at low output.
Pieces say for instance instrumentals with alot of air come off fairly convincing in realism, height and depth, but I wouldnt' call the soundstage enveloping enough so as to be completely holographic, though frighteningly enough it still seems to achieve it the odd time.
In its own way it's become far less intolerant of poor recordings and low quality bitrates, just in that it's so much less lifelike and you're likely to tire listening to that after very long. Feed it something good from a soundtrack for instance and it really fires it out there.
I'd think with more natural sounding bypass caps than FC's, it could be more holographic still and in terms of how well the soundstage is able to surround you it's probably a good idea to pay attention to speaker placement to get the most of it.
Imaging may improve further by synching the modules since they're so close to one another and they're not the lowest in EMI , as well as going true full mono with some physical seperation between them.
I'd say the area it impresses most is that it has no real apparent edge on anything. The decay is mostly in time across the band, very tight, super clear, precise micro-dynamics. While I'd still say it's more analytic than before, and lost alot of that heavily smoothed fingerprint, it is able to manage it fluidly and musically, can't at all consider this cold.
Biggest downside, not the best SNR when driven single ended, balanced really makes a huge difference and I strongly recommend it if you are able, and plan on lots of ventilation as well because they cook pretty good at idle, and I imagine that will also be true of the production modules if they're tuned to spec.
Cheers,
Chris
PS: It's also very likely a more serious transformer would further open up soundstage in every aspect including holography. I'm now looking forward to seeing how post feedback filter affects it all as well too, and am able to attempt it whenever. 😉
T., looks like you were right again.
Just listened to a live version of once upon a time in the west from Dire Straits; bitrate of 160kbs, and it's been a new experience in audio clarity for me personally. Kind of feels like the signal has been class A from start to finish.
Crystal clear resolution.
Should add It's been many a system version's ago that I have listened to this song 😉
Crystal clear resolution.
Should add It's been many a system version's ago that I have listened to this song 😉
classd4sure said:
So the modules are fully working to spec performance after all? Just want to make sure the exact condition of the things.
What kind of speaker is being used?
I still kind of wonder about them cooking at idle. Isn't class D supposed to be sort of "green" amp? Lars?
Keep in mind it's still a 400W @ 4 ohm amp, just because idle current is high it can still be very efficient at high power and still just using the case for cooling. Show me that in an A/B
soongsc said:
Yes, and NCD is absolutely not the one with the lowest idle current. We promote sound quality first, and that leaves us with somewhat higher idle current than most others. Mainly because of the super-controlled timing in the output stage.
If you were to use a switch-off before switch-on scheme like many do, you will get lower power consumption, but also much higher THD. This THD comes from Dead-time distortion, and can always be seen in the THD curve as a rise at 5-7 kHz, to 20-50 times higher THD than elsewhere. (Sometimes more).
In one of those Class D amps you will have an idle current of about 40 mA, while with NCD you have 80-85 mA. So in chris' case you have 80mA x 108V = 8,64 Watts + Gate Drive: 35V x 100mA = 3,5 Watts = total 12,14 Watts of dissipation per channel.
Now in the small ATI 738 box, that accounts for a heat rise to some 50 degrees.
There are ways to get the temperature down of course, you can use the 6 wire power supply, which saves you around 6 Watts totally, so you are down to maybe 43 degs instead. Or use a slightly bigger box, then you are down to 30 degs.
The amplifier will hardly get hotter in case you play at full volume for hours.
btw here is the reason why a 'warmed up' amplifier sounds better than a cold one:
A typical capacitor characteristic, at higher temperatures, the ESR goes down due to the chemical bonding in the electrolytic fluid. From 25 to 55 degrees the ESR is halved, so it's a significant change.
A typical capacitor characteristic, at higher temperatures, the ESR goes down due to the chemical bonding in the electrolytic fluid. From 25 to 55 degrees the ESR is halved, so it's a significant change.
Lars Clausen said:
Do you mean this rising? http://www.newclassd.com/images/ncd2100w8ohmcoil3.gif
BTW, if the UcD amp have THD/Freq flat plot, do you really think that this is an absolutely dead time free amp?
IVX: No this THD has to to with the high modulation index. Dead time usually shows up as a bump in the THD curve at 5-7 kHz. You can find the 5-7 kHz bump in almost any Class D amplifier datasheet, but since comparative marketing is not legal here in Denmark, i am sorry i can not show you any of them. The same also prevents me from commenting on UcD THD figures. Only i would encourage everyone to take a close look at the scale and power level of each curve, in case you want to compare. I can say for sure that we have the lowest THD level.
Lars Clausen said:
Come on, whether it is your official PR thread? 🙂 I'm sure, Hypex will be glad to our comparison even.
Actually, only high modulation index will show real contribution of the dead time distortion, and this contribution itself noway will depends from frequency. The "bump in the THD curve at 5-7 kHz", completely other story -loop_gain/freq dependance (e.g. integrator in the loop).
IVX: Thank You for this comment.
The curves are there already, no need for me to put them together anyway. 😉
Have a nice sunday ... 🙂
The curves are there already, no need for me to put them together anyway. 😉
Have a nice sunday ... 🙂
Ok, it's time for me to spend some money again... The plan is to use four NCDs; two per channel with active x-over. I'll use one 990 VA toroid per channel, but beyond that, I'm not sure.
On my ZAP 2.3SE setup, I have dual schottky bridges, with .22 uF caps over each diode, and a .1 uF cap over the output voltages, as I was advised to do in the 2.3SE vs. 700XE thread. Will those caps do a good job on your soft recovery diodes, or would it maybe be even better to keep my schottkys?
Then there's the issue of caps. I'm going to use the same rectifier for the two amps on each channel, but how about giving them separate caps? That way I could give each amp different caps with the best possible bass and mid/treble properties, and for all I know, they could benefit from simply having their own caps, given their different load.
Any tips?
On my ZAP 2.3SE setup, I have dual schottky bridges, with .22 uF caps over each diode, and a .1 uF cap over the output voltages, as I was advised to do in the 2.3SE vs. 700XE thread. Will those caps do a good job on your soft recovery diodes, or would it maybe be even better to keep my schottkys?
Then there's the issue of caps. I'm going to use the same rectifier for the two amps on each channel, but how about giving them separate caps? That way I could give each amp different caps with the best possible bass and mid/treble properties, and for all I know, they could benefit from simply having their own caps, given their different load.
Any tips?
Novec: I think that's a great idea. You can reuse your Schottkies of course. Then connect the bass caps directly to the rectifiers for high power throughput.
The treble/mid capacitors you can connect to the rectifiers via a couple of 1 Ohms 11W resistors, so you can be sure they are soundwise isolated from the bass capacitors, and also charged with a nice clean DC voltage, instead of charge spikes.
The treble/mid capacitors you can connect to the rectifiers via a couple of 1 Ohms 11W resistors, so you can be sure they are soundwise isolated from the bass capacitors, and also charged with a nice clean DC voltage, instead of charge spikes.
Yup, I was thinking about isolating the mid/treble amps too. That, or I could go for separate bridges alltogether.
Very short - which are best, my 12A schottkys or your 60A fast recovery diodes? Simply wondering, because I have to sell the ZAPs as complete amps anyways, and I just don't know whether to keep the schottkys in the ZAP and go for yours in the NCD, or just buy some simple bridges for the ZAP.
If I were to go for your power supply, would it be possible to get just the parts for it? The PCB is a bit too big for my amp, and it feels pretty stupid to desolder everything and ditch both the PCB and main caps.
Now the question is which caps to use...
Very short - which are best, my 12A schottkys or your 60A fast recovery diodes? Simply wondering, because I have to sell the ZAPs as complete amps anyways, and I just don't know whether to keep the schottkys in the ZAP and go for yours in the NCD, or just buy some simple bridges for the ZAP.
If I were to go for your power supply, would it be possible to get just the parts for it? The PCB is a bit too big for my amp, and it feels pretty stupid to desolder everything and ditch both the PCB and main caps.
Now the question is which caps to use...
The 60EPU20's are very good! And of course you can get them loose, but please don't make separate rectifiers for the same secondary winding. It will not work optimally. Better use the resistor to isolate.
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