dynamic headroom
Yes, but the sensible question is not one of for or against dynamic headroom but one of compromise. If you are restricted (economically, technologically or due to sheer size) regarding the powersupply and have to settle with lets say a 800VA toroid, the configuration of the sencondaries will be a compromise sacrifying DCR for higher voltages. What you gain besides power potential output from an amplifier by choosing higher voltage on the secondaries is also an increased DCR in the power supply, hence more modulation for the same load. I would choose a decent head room with the least modulation any time over more voltage "headroom" with more modulation. A big amp sounds big due to the quality of its PS rather than due to its max output in say 8 or 4 ohms. In two ohm loads or less, the restrictions of the PS kicks in if not the amplifiers current capabilities does, which is the most probable limitation in current class D amplifiers opposed to the linear amps that can burst more current for the peaks in the music.
By all means lets have unlimited power, but don´t let it restrict other more important aspects like making it affordable and have ultimate SQ. Beef up the PS instead, there is nothing that replaces ccm concerning driveability
I can of course always just drive a 300w@8 unit on a +/- 49VDC supply and beat the pants off on those overspec´ed "we just want higher power specs" designs
cheers,
Yes, but the sensible question is not one of for or against dynamic headroom but one of compromise. If you are restricted (economically, technologically or due to sheer size) regarding the powersupply and have to settle with lets say a 800VA toroid, the configuration of the sencondaries will be a compromise sacrifying DCR for higher voltages. What you gain besides power potential output from an amplifier by choosing higher voltage on the secondaries is also an increased DCR in the power supply, hence more modulation for the same load. I would choose a decent head room with the least modulation any time over more voltage "headroom" with more modulation. A big amp sounds big due to the quality of its PS rather than due to its max output in say 8 or 4 ohms. In two ohm loads or less, the restrictions of the PS kicks in if not the amplifiers current capabilities does, which is the most probable limitation in current class D amplifiers opposed to the linear amps that can burst more current for the peaks in the music.
By all means lets have unlimited power, but don´t let it restrict other more important aspects like making it affordable and have ultimate SQ. Beef up the PS instead, there is nothing that replaces ccm concerning driveability
I can of course always just drive a 300w@8 unit on a +/- 49VDC supply and beat the pants off on those overspec´ed "we just want higher power specs" designs
cheers,
Don't mix headrom with dynamic-range !!! Dynamics have also a "low volume part" to them - although this goes forgotten quite often nowadays.
In this department a lower power amp might definitely have its merits.
IMO an amp like someone mentioned that is capable of 300 Watts into 8 Ohms and which is capable of handling very low impedance loads is more than sufficient for more then 98% of all DIY applications.
Those who want bonebreaking bass don't need an amp that is capable of low THD in the midrange and high-frequncy area anyway. For them there are enough alternatives available.
Regards
Charles
In this department a lower power amp might definitely have its merits.
IMO an amp like someone mentioned that is capable of 300 Watts into 8 Ohms and which is capable of handling very low impedance loads is more than sufficient for more then 98% of all DIY applications.
Those who want bonebreaking bass don't need an amp that is capable of low THD in the midrange and high-frequncy area anyway. For them there are enough alternatives available.
Regards
Charles
I agree. I recently put together a pair of UcD180HG modules, running from +4dBu lines, into 87dB/W/m nearfield monitors. The one feature that I would have appreciated most would have been more gain control on the UcD.
I've ended up with a three position switch, 0, -12, or -24dB. The first step comes from reducing the gain on the UcD, the second from attenuation on a balanced input board. I do tend to keep my listening levels quite low, so I'm almost always running at -24 to keep the volume knob in a sensible range. I has all worked out very nicely, but it might have been even better if I could have done all the gain control on the UcD.
Jumpers would be OK, but I'd want to rig them up to a switch, so hopefully the gain change would be pop-free.
Steve.
Since...
we are talking DIY here, gain matching in the system should not be too big a deal. Unlike for those using commercial products, we can build our sources such that the gain matches well, use buffer only (no gain) preamps, etc. No need to be applying a lot of signal attenuation in a DIY set up.
That said, if it is not a compromise and easy to do. Builder setable gain on the DIY nCore module would be a nice feature, but I suspect it will perform best at a certain gain level-Bruno?
For me, amp gain of anywhere from 24 dB-27 dB will work fine.
we are talking DIY here, gain matching in the system should not be too big a deal. Unlike for those using commercial products, we can build our sources such that the gain matches well, use buffer only (no gain) preamps, etc. No need to be applying a lot of signal attenuation in a DIY set up.
That said, if it is not a compromise and easy to do. Builder setable gain on the DIY nCore module would be a nice feature, but I suspect it will perform best at a certain gain level-Bruno?
For me, amp gain of anywhere from 24 dB-27 dB will work fine.
Hello cycle,
it looks that you are wanting to power big subs by these modules. Big subs require high powered and low-ohmic amps. Dot. I think it is total overkill to use this kind of ultra-fancy full range ultra-low THD modules running at > 400kHz for a used channel bandwidth of less than 200Hz. Since there are even effect units that create (add) big artificial THD on purpose (!) for the LFE channel to make it more impressive or "tighter", I 'd strongly guess THD / IMD is not really a noticeable issue with subwoofer amps as long as it is below a few percent. The headbangers won't notice for sure - believe me!
-> A much cheaper and simpler, ~50kHz switching module with even greater efficiency hence greater power density would easily do for the subs. I even have a self-built IGBT full bridge module running at 22kHz from a 600V bus at my home system doing only the bass for 2 x Beyma 18G50 (with one of them needs reconing ;-(....
My main point here is that there seems to be a lack of high power subwoofer class D amps running at lower switching frequency saving up to 90 percent of switching losses compared to full range class D amps. Maybe thats even a market gap where I should step in ..... hmmm...
Keep those ultra-high performance amp modules for the tops!
it looks that you are wanting to power big subs by these modules. Big subs require high powered and low-ohmic amps. Dot. I think it is total overkill to use this kind of ultra-fancy full range ultra-low THD modules running at > 400kHz for a used channel bandwidth of less than 200Hz. Since there are even effect units that create (add) big artificial THD on purpose (!) for the LFE channel to make it more impressive or "tighter", I 'd strongly guess THD / IMD is not really a noticeable issue with subwoofer amps as long as it is below a few percent. The headbangers won't notice for sure - believe me!
-> A much cheaper and simpler, ~50kHz switching module with even greater efficiency hence greater power density would easily do for the subs. I even have a self-built IGBT full bridge module running at 22kHz from a 600V bus at my home system doing only the bass for 2 x Beyma 18G50 (with one of them needs reconing ;-(....
My main point here is that there seems to be a lack of high power subwoofer class D amps running at lower switching frequency saving up to 90 percent of switching losses compared to full range class D amps. Maybe thats even a market gap where I should step in ..... hmmm...
Keep those ultra-high performance amp modules for the tops!
Re Pre-orders: as soon as the design for production is verified and released.
Re Powering buffers: the loop amplifier needs supplies too and can put out a largish amount of current. A +/-15V supply must be used, regulating it down from 67V is wasteful. On the upside, I'm putting the equivalent of the HxR regulators directly on the board.
@Cyclecamper re power ratings, the distortion vs power measurements are available from the hypex web site and some are in the whitepaper linked in the first post of this thread. I think they may answer most of your questions. The thing with some class D suppliers rating 400W amps as 1000W is a known problem and not a practice we subscribe to. What they do is test the amp at 1kHz and forget that at 20Hz the current no longer averages out and the supply needs to deliver current peaks twice as high as the average. Which linear supplies do nicely. As do our SMPS's.
OK let's see what we have so far as far as I can remember (if I'm forgetting something that's been said in this thread, apologies, just mention it again).
Power: 400/4 seems OK for most with a good few wanting about twice that, a few wanting less and a lone vote from someone whose listening room adjoins a substation. We don't police where samples of our industrial modules go after they've been bought by business customers BTW, it's just that when we get DIY support calls about stray NC1200 (or bigger) modules we'll be hard of hearing on one ear and deaf on the other.
On-board DC protect. Well you can't DC protect the amp because you need to power off or disconnect the load in case of a meltdown. But I am putting in DC detection and an open-collector output to turn the supply off.
Thermal protection.
Most seem OK with discrete buffers & loop amp with local regulation (but external 15V required). If you want to change the sound I really think you'll find it much easier just to add your own circuit in front, rather than try and attack the beast directly.
Easily accessible gain setting. I think it'll still be an SMD resistor that you need to change because jumpers require that people at least agree on one or two fixed settings. What I'll do is put the resistor on the top of the board and mark it clearly.
Plate construction seems accepted provided it can also be screwed down from the top. I think I'll go for the through-the-PCB approach (with an allen key i.e. small hole).
L bracket, either optional or part of the standard delivery (it's not that expensive to add it as standard).
Output connectors, didn't get much comments on that. I would prefer not to encourage soldering to boards (other than the inevitable modding of course) so it's either the screw tags or the banana plugs.
Other connectors: one vote for right-angle (which incidentally happened to be what I had in mind), no comments otherwise. Here's the list of circuits I've got on the draft (in no particular order):
+HV
-HV
GND (return to PSU)
+15
-15
DC fault flag
VDR (optional external VDR to reduce idle losses)
GND (for cable shield)
Audio+ (Hot or signal)
Audio- (Cold or signal ground)
Enable
I've not yet found a "DIY-friendly" connector style that will do all of this so what I was thinking was to use a good quality industrial type (e.g. microfit with the necessary parallelling of pins) and put premade cables in the package as standard. The amplifier modules would come with cables that have connectors on one end only, the SMPS would be shipped with another set of cables that have connectors fitted on both ends. But the latter part hinges on some agreement on how long those cables should be.
Something else crossed my mind, the input cable (which would become a standard part of the package as well). Is everyone OK with the current Mogami cable?
Re Powering buffers: the loop amplifier needs supplies too and can put out a largish amount of current. A +/-15V supply must be used, regulating it down from 67V is wasteful. On the upside, I'm putting the equivalent of the HxR regulators directly on the board.
@Cyclecamper re power ratings, the distortion vs power measurements are available from the hypex web site and some are in the whitepaper linked in the first post of this thread. I think they may answer most of your questions. The thing with some class D suppliers rating 400W amps as 1000W is a known problem and not a practice we subscribe to. What they do is test the amp at 1kHz and forget that at 20Hz the current no longer averages out and the supply needs to deliver current peaks twice as high as the average. Which linear supplies do nicely. As do our SMPS's.
OK let's see what we have so far as far as I can remember (if I'm forgetting something that's been said in this thread, apologies, just mention it again).
Power: 400/4 seems OK for most with a good few wanting about twice that, a few wanting less and a lone vote from someone whose listening room adjoins a substation. We don't police where samples of our industrial modules go after they've been bought by business customers BTW, it's just that when we get DIY support calls about stray NC1200 (or bigger) modules we'll be hard of hearing on one ear and deaf on the other.
On-board DC protect. Well you can't DC protect the amp because you need to power off or disconnect the load in case of a meltdown. But I am putting in DC detection and an open-collector output to turn the supply off.
Thermal protection.
Most seem OK with discrete buffers & loop amp with local regulation (but external 15V required). If you want to change the sound I really think you'll find it much easier just to add your own circuit in front, rather than try and attack the beast directly.
Easily accessible gain setting. I think it'll still be an SMD resistor that you need to change because jumpers require that people at least agree on one or two fixed settings. What I'll do is put the resistor on the top of the board and mark it clearly.
Plate construction seems accepted provided it can also be screwed down from the top. I think I'll go for the through-the-PCB approach (with an allen key i.e. small hole).
L bracket, either optional or part of the standard delivery (it's not that expensive to add it as standard).
Output connectors, didn't get much comments on that. I would prefer not to encourage soldering to boards (other than the inevitable modding of course
) so it's either the screw tags or the banana plugs.Other connectors: one vote for right-angle (which incidentally happened to be what I had in mind), no comments otherwise. Here's the list of circuits I've got on the draft (in no particular order):
+HV
-HV
GND (return to PSU)
+15
-15
DC fault flag
VDR (optional external VDR to reduce idle losses)
GND (for cable shield)
Audio+ (Hot or signal)
Audio- (Cold or signal ground)
Enable
I've not yet found a "DIY-friendly" connector style that will do all of this so what I was thinking was to use a good quality industrial type (e.g. microfit with the necessary parallelling of pins) and put premade cables in the package as standard. The amplifier modules would come with cables that have connectors on one end only, the SMPS would be shipped with another set of cables that have connectors fitted on both ends. But the latter part hinges on some agreement on how long those cables should be.
Something else crossed my mind, the input cable (which would become a standard part of the package as well). Is everyone OK with the current Mogami cable?
Sounds excellent ! current Mogami cable was perfect on the UCD for me (novice).
Suggestion for things to add in the package: documentation including a few implementation examples for novices, just to reassure them and provide tips and tricks (can also be put on the web page of course or here)
Suggestion for things to add in the package: documentation including a few implementation examples for novices, just to reassure them and provide tips and tricks (can also be put on the web page of course or here)
Hi Bruno,
First of all, it´s great that you take the temperature on the DIY community before you finalize your DIY oriented module. This is how proper product development is done!
Concerning the connector types, would it be possible to provide the bare connectors with the modules as the choice of cables may be a parameter some likes to work with? (Personally I do, of course
) -It would also engage any who wants to place the modules as they please in one or more chassis...I´m all in for banana-plug connectors
best regards,
Joakim
works fine for me. I also like the screw terminals for the outputs.
screw terminal is OK for many of the other connections as well (does take up more real estate...) Microfit are nice, not especially DIY friendly, but if one is supplied, and replacements are generally available it is not any problem.
thanks!
Bruno,
When I read this my antennae went vertical:
I am VERY interested in how you would approach continuous stability, during start-up and clipping, in a high-order-loop class-A(B) amp. Any tips/hints/topologies/circuits/references you can provide now would be invaluable to me. (And I hope that a practical demonstration amp and accompanying article are in your future.)
When I read this my antennae went vertical:
For a couple months, I've been considering higher order control loops (3rd-4th order) for class-A(B) amps. Clipping and start-up stability are, of course, major design issues with such arrangements. My thinking only got me to pre-clamping (like Bob Cordell's Klever Klipper) and out-of-bounds detection to initiate a state-clearing mute (to be used at start-up as well). The concept of dynamically modifying the loop to fall back to a stable lower-order loop was new to me when I read your N-Core white paper. However, for a linear amplifier, this does not seem as easy and straightforward as
when the gain crossover frequency must be kept below some point (1-10MHz let's say).
I am VERY interested in how you would approach continuous stability, during start-up and clipping, in a high-order-loop class-A(B) amp. Any tips/hints/topologies/circuits/references you can provide now would be invaluable to me. (And I hope that a practical demonstration amp and accompanying article are in your future.)
You might see if the Ncore patent application supplies inspiration. I'd love to make and publish a demonstration design of a class AB "feedback monster" to supplement the Linear Audio article (an encore of extrema so to speak) but to keep my sanity I have decided to take a FIFO approach towards my spare time, ie. think very carefully if I want or need to do it and then stick it at the end of the line. This FIFO already contains three years' worth of Grimm Audio stuff (an MFB sub for the LS1, a compressor, an EQ, a mic pre, a discrete true 192/24 bit AD/DA) so all I can do is to schedule any class AB related activities after that. I do hope that by that time someone else will have cracked it because it's a lot easier to do than a decent class D.
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