NCD questions

[Anzgar]

Thanks for the answer, Lars
So, i'll put 2 switchs. One for softstart and one for Vgate.

Hmm, I use a 6wire psu but a softstart from LC audio and a separate transformer

 

[novec]

Exactly the same setup as me, Anzgar. I don't know if the LC softstart is quick enough for the NCD startup delay, but maybe you do, Lars?

 

[raintalk]

I will have too disagree with you raintalk
There is always a burnin period, although there will also be some listener getting "use to" the amp.
I believe that this is much less than burnin, though.
Materials, both metals and plastics, just take time to settle.
Valves take many hours to settle, as do semi-conductor and discrete components

thanks
KL

We're allowed to disagree

I'm OK with burn in for mechanical devices, but not for semiconductor devices and components. It would suggest there's some kind of measurable wear.

For tubes - sure they wear and change their characteristics over time, but a big advantage to semiconductors is they don't.

If there is a "burn in period" then all amplifier reviews are off. How do we know they allowed for a x-hour burnin? Why wouldn't manufacturers do the burn in and then a final calibration before shipping? If it doesn't sound good or measure good when first plugged in then there's a design flaw.

 

[novec]

But you agree that capacitors, being chemical/mechanical components might need some time to settle? That's my experience, anyways.

As far as semiconductors go, there are issues like electromigration in play, but I don't have the knowledge to go into any details there. I have an easily measureable example, though; computer overclocking. It is "common knowledge" among overclockers that a CPU won't reach its full potential right out of the box. After a few days of work, its working temperature will generally have lowered a few degrees, and the maximum obtainable speed is increased. Years back, I had a Pentium III 800 that stopped at 960 MHz when I first plugged it in, but after a week of burning in it crept well over a gigahertz.

Sound quality, and how burning in affects it, is of course a lot more complex, but the example shows that things actually do happen inside semiconductors over the first few days, it's not just in your head

As far as manufacturer burn-in goes, I'd think they skip it mostly because it would cost too much both in staff, workspace and electricity to do something that the customer will enjoy doing anyways.

 

[KLe]

But you agree that capacitors, being chemical/mechanical components might need some time to settle? That's my experience, anyways.

As far as semiconductors go, there are issues like electromigration in play, but I don't have the knowledge to go into any details there. I have an easily measureable example, though; computer overclocking. It is "common knowledge" among overclockers that a CPU won't reach its full potential right out of the box. After a few days of work, its working temperature will generally have lowered a few degrees, and the maximum obtainable speed is increased. Years back, I had a Pentium III 800 that stopped at 960 MHz when I first plugged it in, but after a week of burning in it crept well over a gigahertz.

Sound quality, and how burning in affects it, is of course a lot more complex, but the example shows that things actually do happen inside semiconductors over the first few days, it's not just in your head

As far as manufacturer burn-in goes, I'd think they skip it mostly because it would cost too much both in staff, workspace and electricity to do something that the customer will enjoy doing anyways.

Hi novec
Yes, I agree.
Also, some resistors require burnin, such as the Vishay bulk metal foils.
I believe that burnin is temperature, mechanical and electrical(off course) related. Really everything is electromigration or electron movement in relation to their surroundings (ie. dielectrics, metals (crystal boundries etc)), wrsto applied DC and AC current.

Well anyway, it would usually appear that if no burnin is required then it would reflect the following
... the electronic component is not very good
... the electronic component is so good that burnin happens very rapidly and isn't noticed

thanks
KL

 

[raintalk]

?
For burnin, can somebody measure
A brand new amp?
An amp as it's in burnin? (what 10 hours?)
After it's burnt in?
Six months later?
A year later?

If burnin is needed, there should be some measurable changes.

 

[soongsc]

Just for capacitors, I have measured impedance differences between with and without burn-in. Burn in is also used as a standard procedure in military equipment to sort out out the early life failures. Normally 48 hours at a certain duty cycle is used.

 

[edge540]

I've received the hypex's softstart.
They are ok with NCD. they are fully on before the ncd is switching on.

 

[raintalk]

Just for capacitors, I have measured impedance differences between with and without burn-in. Burn in is also used as a standard procedure in military equipment to sort out out the early life failures. Normally 48 hours at a certain duty cycle is used.

So wouldn't it be best for the "Quality Policies" for the NewClassD to include an adequate burn in?

http://newclassd.com/index.php?page=12

Who'd want to get an amp module, and after burn in, not be happy with the sound. It should work as specified of the box.

Maybe I can see a burn in for component failure and solder joint failures, I still don't quite see changes in component values, (capacitors ) affecting the perceivable or measurable sound out of the amp. The % of change should be small, and the design of the amp should account for this change.

 

[edge540]

I've noticed this burning periode with my charlize too.
And i've noticed that the smoother step is relatively brief(1ou2 hours after many hours of burning).
Perhaps, its not scientific, but it's not an accoutumance with the new sound, i'm sure.
Is it due to the power supply or to the amp, i don't know?

 

[soongsc]

So wouldn't it be best for the "Quality Policies" for the NewClassD to include an adequate burn in?

http://newclassd.com/index.php?page=12

Who'd want to get an amp module, and after burn in, not be happy with the sound. It should work as specified of the box.

Maybe I can see a burn in for component failure and solder joint failures, I still don't quite see changes in component values, (capacitors ) affecting the perceivable or measurable sound out of the amp. The % of change should be small, and the design of the amp should account for this change.

I'm not aware of any commercial product that does the burn-in step, I thyink the reason is cost and probability of failure. Military equipment are quite expensive and sometimes mission critical. they don't want a piece of equipment to stay a few years on a shelf only to find it does not work when it gets to the field.

 

[novec]

I don't have all the explanations, but I hear the difference between equipment coming straight from the workbench - be it amps, speakers or cables - and when it's been playing for a few days. And since it almost always ends up getting better, I'm just happier for it. If you don't hear any difference, it just means you can start enjoying music sooner

 

[KLe]

I've received the hypex's softstart.
They are ok with NCD. they are fully on before the ncd is switching on.

Thanks edge540
for the info
Although won't really need one unless your tranny is >500VA, which will be me because I will be using a 1KVA 40-0-40 tranny

thanks
KL

 

[novec]

I'm using an LC Audio softstart now, but as it may be too small for 4 NCDs, 2600 VA and 180 000 uF, I might want to try the direct relay approach, using a beefy relay with a 220 VAC coil connected directly after the softstart resistor. Any comments on that?

Regardless, I'll do the direct relay on the gate drive, with 24 VDC relays. They'll switch on easily at the 20-21 volts output, but won't switch on until the softstart is pretty much done. Voilà, startup delay problem all gone.

 

[Lars Clausen]

Novec: You need the relay to clamp on in one go, so the coil-after-resistor method does not work good enough.

I suggest using a bigger wattage resistor on the soft start circuit you have.

I.e. 68 Ohms 25W. You can get from Farnell. Also you need the bigger PTC thermofuse. Can also get from Farnell.

Best regards

Lars C

 

[novec]

Novec: You need the relay to clamp on in one go, so the coil-after-resistor method does not work good enough.

Uhm... Que? I'm not sure what you mean, but the resistor will stay in the circuit when the relay is clamped too, so there will always be power to the coil. And once the relay is clamped, the coil will be connected directly to mains.

 

[Lars Clausen]

Right, but in practical use it tends to 'rattle' before clamping on. Severely reducing the life expectancy of the relay.

 

[novec]

Right, gotcha. Considering I only turn my amp a few times a year, life expectancy shouldn't be a problem But is there a simple solution to it?

I might end up putting the LC soft start on my sub, which only has a 500VA with 44 mF caps, and do something beefier for my main amp. I've got a couple of 470 Ohms 100 W resistors lying around, which could probably do well for limiters, parallelled. Any idea how to calculate current draw for a given VA and uF value?

(sorry for the off-topic)

 

[Lars Clausen]

Why not use the L C Audio softstart to switch the coil on your big relay (with 230V coil). Just remove the 330R resistor.

 

[novec]

Thanks, my brain doesn't always see the obvious solutions The only thing is whether the timing fits with my resistors and my power supply. Is it a pure timer, or does it measure PSU primary voltage and switch on when it's reached mains voltage?

Another thing - has anyone tried using a separate PSU for the input stage yet? If it's worth the extra components and work, I'll have to make extra space for it before I start manufacturing my case.