I can't imagine that anyone has an induced noise issue with speaker cables in a home stereo environment. Multiple conductors will enhance high-frequency conductivity due to reduced/distributed skin-effect. Star-quad is used for microphone level signals that are around 80-90dB lower level than speaker power.
Hi ti33er, I only turn off my nc400 monoblocks when changing something in my setup or going on vacation. My sons ucd400 amp was not turned off for 2 whole years. And now only turned off when on vacation. Neiter the ucd400 or nc400 cabinettes get more than lukewarm (aluminium cabs).
Regards
Kjartan
There is a reason Bruno recommended the output leads be twisted and routed to avoid forming a loop antenna - the feedback loop takes induced noise almost directly into the inputs. But I agree star-quad on the speaker leads is total overkill - all I was recommending was that if you run 4 leads instead of 2, the best configuration is a star-quad.
I have a question concerning the measurement and adjustment of the DC offset of the XLR input on my NCores:
nAmpon is disconnected, XLR input is not terminated (floating freely) as stated and no load at the speaker terminals. If i measure the DC offset between Pin 2 and 1 (XLR connector + and GND) and look at the same time at the scope display, i see a hum signal (50 Hz) on that input, which diminishes a lot if i connect something to it (just an adapter), shielding the input somehow this way.
The measured DC offset starts at around 200 mV (cold), continues down to 0 and finally stabilizes after some time at around 40 mV (warm). The hum signal ist still present. The offset seems to be a bit drifting during the startup phase.
Should that final offset been adjusted down to zero using R95 ? Has someone checked with a scope, what the signal is at his input during that measurement ?
nAmpon is disconnected, XLR input is not terminated (floating freely) as stated and no load at the speaker terminals. If i measure the DC offset between Pin 2 and 1 (XLR connector + and GND) and look at the same time at the scope display, i see a hum signal (50 Hz) on that input, which diminishes a lot if i connect something to it (just an adapter), shielding the input somehow this way.
The measured DC offset starts at around 200 mV (cold), continues down to 0 and finally stabilizes after some time at around 40 mV (warm). The hum signal ist still present. The offset seems to be a bit drifting during the startup phase.
Should that final offset been adjusted down to zero using R95 ? Has someone checked with a scope, what the signal is at his input during that measurement ?
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nAmpOn has to be pulled low to activate the amp(s), if high the amp - not the PSU - is in standby mode. That will keep the PSU alive and dissipating heat. The PSU can be switched off by another input: J5.1
We are working on a 12V trigger using opto couple and 10A Triac PCB's should go into production later this week which will turn the whole amp off inc PSU's.
Regarding the warmness to touch of most NC400/500 amps, they tend to use the case ie the PSU and Amp modules Hypex incorporated heat sinks are bolted directly to the case due to there low heat output. Most A/B amps have large dedicated heat sinks to dissipate the heat directly out of the case rather than through the case which is what you are feeling. At idle a single NC500 channel uses 18W now if you enclosed a light bulb in the same case it would become warm to the touch. A A/B amp will be pushing out more heat. A possible answer.
Regarding the warmness to touch of most NC400/500 amps, they tend to use the case ie the PSU and Amp modules Hypex incorporated heat sinks are bolted directly to the case due to there low heat output. Most A/B amps have large dedicated heat sinks to dissipate the heat directly out of the case rather than through the case which is what you are feeling. At idle a single NC500 channel uses 18W now if you enclosed a light bulb in the same case it would become warm to the touch. A A/B amp will be pushing out more heat. A possible answer.
Hi Burkm Your temp reading seems OK and normal. We have started fitting full grilled top lids recently. This is more a precaution and to aid long term reliability. Our amps can run all day and night in a 21 degree room with the top vents completely shut off though its not something I would recommend for the amp long term.
The DC offset will stabilise after around 10 mins we see typical values of 2-6mV.
Happy to take some measurements of specific components to help put your mind at rest!
The DC offset will stabilise after around 10 mins we see typical values of 2-6mV.
Happy to take some measurements of specific components to help put your mind at rest!
Just finalized the mono Ncore NC400.
The DC balance offset of the input has been extremly sensitive even to the slightest movement of hands. I arrived at an adjustable minimum (R95) of about 5.6 mV after one hour run time. The results have been verified in parallel with my scope. The resulting output offset adjusted to about 16 mV and has been spot on without touching the R135 for further adjustments.
Just wonder, why no cermet multiturn pots are been used at those positions... may be to expensive ?
I will leave the amp ideling over night connected to a 4 ohm load.
The DC balance offset of the input has been extremly sensitive even to the slightest movement of hands. I arrived at an adjustable minimum (R95) of about 5.6 mV after one hour run time. The results have been verified in parallel with my scope. The resulting output offset adjusted to about 16 mV and has been spot on without touching the R135 for further adjustments.
Just wonder, why no cermet multiturn pots are been used at those positions... may be to expensive ?
I will leave the amp ideling over night connected to a 4 ohm load.
The mono NCore NC400 (case closed) stabilized (no signal but no standby) at about 30 - 32°C case temperature (Ghentaudio Mono MX case). It feeels barely "warm" to the touch.
The residual (448 kHz carrier freq) arrived at 0,760 Vpp. DC offset at the output is about 8 mV at the moment. During the warmup phase a lot of DC drift on both, input and output, is visible. It starts at > 200 mV for the input and gradually approaches the lower limit.
The residual (448 kHz carrier freq) arrived at 0,760 Vpp. DC offset at the output is about 8 mV at the moment. During the warmup phase a lot of DC drift on both, input and output, is visible. It starts at > 200 mV for the input and gradually approaches the lower limit.
Would be great, if this was available as an external module too, because i can't add anything into that stereo version. Depending on the size of that board it might fit inside the mono case though.
The more "universal" option would be an external unit hooked up in between the mains cord... No fiddeling around then, just Plug&Play...
Any pricing already established ?
The more "universal" option would be an external unit hooked up in between the mains cord... No fiddeling around then, just Plug&Play...
Any pricing already established ?
Stereo Amp
I started finalizing the stereo amp.
Due to the extreme sensitivity of the DC input adjustment pot ist is almost impossible to insert the adjustment tool (even very gently) without changing the value. It jumps of the scale almost immediatelly. No wonder that several users got relatively "high" offset values there, because setting its value "close to zero" as advised is almost impossible. And to maintain this during daily use is at least "questionable"...
The slightest movement or even vibration will change the adjustment. Putting your finger on top of the pot: change. Insert der adjustement tool: change. Moving the adjustment tool "slightly" without even twisting: change.
Can't believe that.
Note: I realised this already while adjusting the mono amp.
Will see what the second channel does.
I started finalizing the stereo amp.
Due to the extreme sensitivity of the DC input adjustment pot ist is almost impossible to insert the adjustment tool (even very gently) without changing the value. It jumps of the scale almost immediatelly. No wonder that several users got relatively "high" offset values there, because setting its value "close to zero" as advised is almost impossible. And to maintain this during daily use is at least "questionable"...
The slightest movement or even vibration will change the adjustment. Putting your finger on top of the pot: change. Insert der adjustement tool: change. Moving the adjustment tool "slightly" without even twisting: change.
Can't believe that.
Note: I realised this already while adjusting the mono amp.
Will see what the second channel does.
Wouldn't it make more sense to trigger the SMPS standby instead of using a triac "circuit breaker" approach?
I would say a multiturn pot is overkill for something that gets adjusted once, isn't very critical and won't affect sound quality.
Don't know really.
In my opinion it is quite critical because its a DC coupled design, which amplifies any DC imbalance at the input into a larger deviation at the output. If this can be offset then by such little effort...
If this goes off already doing some hefty "breathing" close to the adjustment pot i would judge differently. One can't barely touch it without changing its settings already.
Never have seen such a sensitive adjustment in my professional life yet.
In my opinion it is quite critical because its a DC coupled design, which amplifies any DC imbalance at the input into a larger deviation at the output. If this can be offset then by such little effort...
If this goes off already doing some hefty "breathing"
close to the adjustment pot i would judge differently. One can't barely touch it without changing its settings already. Never have seen such a sensitive adjustment in my professional life yet.
This would only hold true for someone, who was going to built one anew or modifying an existing one.
But fiddeling around wih a "finished" product is - in my opinion - something else.
If you don't want to open up that case it is a lot easier to add something more universal from the outside... and because many others, which don't own or have built a NCore amp, are looking for such a device. Thus it would create more sales if made for everyone...
Don't know really.
In my opinion it is quite critical because its a DC coupled design, which amplifies any DC imbalance at the input into a larger deviation at the output. If this can be offset then by such little effort...
As the DC offset varies with temperature and other factors anyway, getting it "exactly right" is not in any way essential. If you want to get rid of the DC offset completely, you need a DC servo circuit.
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If you are looking for an external, non-ncore-specific unit, there are of course lots of designs and products out there already - no need to come up with a completely new one.
Besides, fiddling with a supposedly "finished" product is what DIY is all about...
I was suprised somewhat how much DC drift occured during warmup. Starting at something > 200mV, going down into negative terretory and ending at about +100mV. Expected a more stable configuration. Same holds for the adjustment pot(s).
It is not so much about getting it "exactly" right, but about ease of adjustment and holding its value afterwards. If the units as delivered by the manufacturer are (sometimes ?) off already and might change by minimal movements... Ouch
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