Neutral is what we like 😀
On a side note, check the hypex.nl front page. A softstart circuit has been announced.
Seems like I'm going to have to pay transport fees again from Hypex.
For the starting DIY, this means the circle is complete - you can buy the full monty at Hypex, less the chassis: Transformer, softstart, PS and modules.
Just wish they had more choice in the transformer department - I'd like to have 800VA - I'll have to order them at Amplimo instead.
Yves
On a side note, check the hypex.nl front page. A softstart circuit has been announced.
Seems like I'm going to have to pay transport fees again from Hypex.
For the starting DIY, this means the circle is complete - you can buy the full monty at Hypex, less the chassis: Transformer, softstart, PS and modules.
Just wish they had more choice in the transformer department - I'd like to have 800VA - I'll have to order them at Amplimo instead.
Yves
Oh what a pain, I need a ready made softstart but Hypex dont say when theirs will be available.
Any details JP or Bruno.... Please
I am happy to test a pre production version ;-)
Any details JP or Bruno.... Please
I am happy to test a pre production version ;-)
It's with typical hypex details though 😀
Switching at zero cross, nice & sweet!
I see a lot of connectors, I like the "soft button" method, makes it easier for layout.
Fingers crossed it's not too pricey...
Switching at zero cross, nice & sweet!
I see a lot of connectors, I like the "soft button" method, makes it easier for layout.
Fingers crossed it's not too pricey...
wytco0 said:
Use a thermistor. If it's good enough for Nelson Pass' amps it's good enough for mine.
As Nelson Pass points out in some long lost thread, the ~1.5 to 2 ohms it drops to helps limit the DC current flow through the primary as well, doubles as a cheap hum killer. Digikey has nice ones for cheap.
Worst case scenario the power goes out and comes right back, it trips the breaker or blows the fuse, you could even couple it to a resettable one, cheap and effective.
Regards,
Chris
Thermistors are great on Pass amps because they are class-a hence draw heavy and fairly constant current. With class-b and class-d having such large average to peak ratio you will be limiting the current too much so that peaks are compressed, unless you are running a PA rig or similar where it will be cranking out at near full power most of the time.
Several people have suggested that a thermister doesn't get hot enough at the kind of current draw you get with a Class D amp.
I have wondered if you put a low Ohm resistor next to the thermister would that act as a heater?
Automatic fuses sound nice, but I'm not sure they would blow quickly enough to save a fastblow fuse in the main cord or a breaker at the wall?
Ed
I have wondered if you put a low Ohm resistor next to the thermister would that act as a heater?
Automatic fuses sound nice, but I'm not sure they would blow quickly enough to save a fastblow fuse in the main cord or a breaker at the wall?
Ed
Hello,
Our soft start will be available in about 4-5 weeks from now.
The features are as follows;
Soft start module to keep transformer inrush currents at low levels , saving fuses and increases component lifespan. Features are:
► switches at mains zero crossing.
► supports 115/230Vac.
► Temperature protection by a PTC (not included).
► Dual LED to indicate standby/on (not included).
► Possibility to use a low voltage switch/pushbutton (not included).
It's not only a soft start module, but you can also power up your amplifier with a nice low voltage switch or pushbutton. Besides this you have the possability for a temperature protection and we support 115/230VAC mains voltage.
Regards,
Jan-Peter
Our soft start will be available in about 4-5 weeks from now.
The features are as follows;
Soft start module to keep transformer inrush currents at low levels , saving fuses and increases component lifespan. Features are:
► switches at mains zero crossing.
► supports 115/230Vac.
► Temperature protection by a PTC (not included).
► Dual LED to indicate standby/on (not included).
► Possibility to use a low voltage switch/pushbutton (not included).
It's not only a soft start module, but you can also power up your amplifier with a nice low voltage switch or pushbutton. Besides this you have the possability for a temperature protection and we support 115/230VAC mains voltage.
Regards,
Jan-Peter
Hello,
I think a 20 Ohm NTC would do the job. I figure it's AC current and on a 500VA transformer a fairly low resistance primary coil, there at 75% of it's rated 25amp continuous load its' still in the in the tens of milliohms. At idle it should do no worse than a measly 1.5 to 2 ohms which is what I'd prefer to limite the dc current anyway. No harm in trying it I suppose. I'm going to try it and I'll let you know what happened. Admittedly it is far from the ideal solution...
There won't be such a thing as a cable fuse but there will be a mains fuse, if it blows it did it's job, no big deal.
I'll start off with a 15 amp slow blow and see how it likes it.
Will switch the neutral and live lines with fairly hefty 25 amp NO poles, use two more 8 amp NC poles of the same relay to short the PSU caps across the primary coil via current limiting power resistors as a replacement to the regular bleeder circuit. HAZARD? It better be the right relay!!. They will switch out of circuit under normal operation, drawing nothing from the supply, and quickly drain the caps when turned off, as seen in EDN.
I'm going with a second auxiliary 50VA transformer for eventually powering a low noise supply for the front end of the amps, and more immediatly, a 24Vac relay coil which will close to act upon the larger PSU's mains relay.
The aux supply will be controlled by probably a 5 amp slow trip breaker at the back of the amp, meant to normally stay ON, keeping both supplies powered. You can add NO or NC contacts on it to control all you like, available with remote lines to remotely close the remaining poles, allowing me to enable the modules remotely via low voltage switch which I would wire latched so that when the power goes out it will turn off the module and stay off in case the power comes right back again. Also should the aux breaker trip, it will have the same effect.
Good plan?
Chris
I think a 20 Ohm NTC would do the job. I figure it's AC current and on a 500VA transformer a fairly low resistance primary coil, there at 75% of it's rated 25amp continuous load its' still in the in the tens of milliohms. At idle it should do no worse than a measly 1.5 to 2 ohms which is what I'd prefer to limite the dc current anyway. No harm in trying it I suppose. I'm going to try it and I'll let you know what happened. Admittedly it is far from the ideal solution...
There won't be such a thing as a cable fuse but there will be a mains fuse, if it blows it did it's job, no big deal.
I'll start off with a 15 amp slow blow and see how it likes it.
Will switch the neutral and live lines with fairly hefty 25 amp NO poles, use two more 8 amp NC poles of the same relay to short the PSU caps across the primary coil via current limiting power resistors as a replacement to the regular bleeder circuit. HAZARD? It better be the right relay!!. They will switch out of circuit under normal operation, drawing nothing from the supply, and quickly drain the caps when turned off, as seen in EDN.
I'm going with a second auxiliary 50VA transformer for eventually powering a low noise supply for the front end of the amps, and more immediatly, a 24Vac relay coil which will close to act upon the larger PSU's mains relay.
The aux supply will be controlled by probably a 5 amp slow trip breaker at the back of the amp, meant to normally stay ON, keeping both supplies powered. You can add NO or NC contacts on it to control all you like, available with remote lines to remotely close the remaining poles, allowing me to enable the modules remotely via low voltage switch which I would wire latched so that when the power goes out it will turn off the module and stay off in case the power comes right back again. Also should the aux breaker trip, it will have the same effect.
Good plan?
Chris
classd4sure said:
Hi Chris,
If you are adding already that much stuff, then why not a real softstart circuit instead of the NTC. The results with NTC would be interesting though from an academic point of view🙂. I expect problems as in idle, UcD modules draw only something like 60mA which will probably not be enough to heat up the NTC, then when you suddenly need higher power, the voltage may collapse for a short time until the NTC is heated up sufficiently. To see these effects, can you monitor the DC power supply voltage during startup, let it run idle a few seconds and then run some music, see what happens to the supply voltage (using a scope). I guess even when you play at moderate level, say 1W output power and you get sudden peaks of say several tens of watts, that the power supply voltage will partly collapse due to the NTC not being hot enough when the amps deliver 1W.
The above is what I expect, I have never tried it so I maybe wrong.
Best regards
Gertjan
Hi,
I don't even need to see it, I did expect that result with it, don't worry you haven't shocked me.
I didn't intend on the resistance normally staying so high, so far though I think all I've head is theory, has anyone tried it? I admit it's a good theory. Academics or not if it works it works. The mains vary +-10%... etc.
Will it rule the amplifier's response/dynamic range or will it simply show itself as a bit of noise in an otherwise noisy line?
The thermal time constant is 224 seconds, thinking it's an NTC it should have a run away affect to it.. it'll either stay hot or and sound fine or stay cold and kill it, but really how bad can it throttle the amp, at 20ohms (cold) on a 120V line, should be more than enough to keep the caps charged, with their time constant over the load by the time the rails start to sag....=hot thermistor, no I haven't done that math, I would but I'm honestly not in love with the idea that much.
Without that, I don't think it will have a soft start, I'm content to go and lean on the breaker for now. Most of what I mentioned isn't offered on current soft start units, some is on the Hypex one I see, nice one.
The aux xformer is staying, it's required for what I want to do later on, and for how I want my bleeders to work, soft start modules dont' do this for you. Most of the rest of it are easy options, yes each one costing more, but my point was it can be built on. Out of all that you can really only compare the thermistor I intended on using to "why not just get a soft start".
Maybe when I see what Hypex has in store I'll change my mind, but that soft start isn't out yet.
Right now I'm very much in the kicking around ideas for that aspect of it, just only with what I can get/do now.
It's simple enough to DIY other than the want for a good PCB for safety purposes..
I do like that alot of the features on it will be optional though, keep the cost low for us.
Argh, I'll just twist the wires in a knot and throw some tape on it.
Regards,
Chris
EDIT:
PS, if the soft start had the DC trap circuit + the RFI filter I'd find that very hard to resist.
I don't even need to see it, I did expect that result with it, don't worry you haven't shocked me.
I didn't intend on the resistance normally staying so high, so far though I think all I've head is theory, has anyone tried it? I admit it's a good theory. Academics or not if it works it works. The mains vary +-10%... etc.
Will it rule the amplifier's response/dynamic range or will it simply show itself as a bit of noise in an otherwise noisy line?
The thermal time constant is 224 seconds, thinking it's an NTC it should have a run away affect to it.. it'll either stay hot or and sound fine or stay cold and kill it, but really how bad can it throttle the amp, at 20ohms (cold) on a 120V line, should be more than enough to keep the caps charged, with their time constant over the load by the time the rails start to sag....=hot thermistor, no I haven't done that math, I would but I'm honestly not in love with the idea that much.
Without that, I don't think it will have a soft start, I'm content to go and lean on the breaker for now. Most of what I mentioned isn't offered on current soft start units, some is on the Hypex one I see, nice one.
The aux xformer is staying, it's required for what I want to do later on, and for how I want my bleeders to work, soft start modules dont' do this for you. Most of the rest of it are easy options, yes each one costing more, but my point was it can be built on. Out of all that you can really only compare the thermistor I intended on using to "why not just get a soft start".
Maybe when I see what Hypex has in store I'll change my mind, but that soft start isn't out yet.
Right now I'm very much in the kicking around ideas for that aspect of it, just only with what I can get/do now.
It's simple enough to DIY other than the want for a good PCB for safety purposes..
I do like that alot of the features on it will be optional though, keep the cost low for us.
Argh, I'll just twist the wires in a knot and throw some tape on it.
Regards,
Chris
EDIT:
PS, if the soft start had the DC trap circuit + the RFI filter I'd find that very hard to resist.
A question of starting
Hey guys,
How about something simple that will work? Use Chris's 20 ohm PTC but bypass it with a set of relay contacts. Have the relay driven from the rail voltage and set a resistance value in series with the coil so it don't close till say 80-90% of the rail voltage is present. This won’t require a heavy duty relay as when the contacts close most of the inrush is done. Seems this will solve the problem nicely.
Roger
Hey guys,
How about something simple that will work? Use Chris's 20 ohm PTC but bypass it with a set of relay contacts. Have the relay driven from the rail voltage and set a resistance value in series with the coil so it don't close till say 80-90% of the rail voltage is present. This won’t require a heavy duty relay as when the contacts close most of the inrush is done. Seems this will solve the problem nicely.
Roger
Hi,
Yup that's the easy way, no point to using a thermistor though, simple power resistor would do.
Ivan I did have trouble understanding that I admit it. 🙁
Regards,
Chris
Yup that's the easy way, no point to using a thermistor though, simple power resistor would do.
Ivan I did have trouble understanding that I admit it. 🙁
Regards,
Chris
I keep reading about bleeders - however, the modules, when "off", still draw a bit power from the caps.
My 22.000uF's are at very low voltage after about 2 minutes. Isn't this enough?
It's a moot point for me actually, as i'm changing to the Hypex PS, which seems to have lots of resistors parallel over the rails, must be bleeders 😀
My 22.000uF's are at very low voltage after about 2 minutes. Isn't this enough?
It's a moot point for me actually, as i'm changing to the Hypex PS, which seems to have lots of resistors parallel over the rails, must be bleeders 😀
I think the idea of using the positive temp co thermistor to heat the negative temp co one is interesting. I guess both are wired in parallel. Just how well it would turn out functionally is something to observe.
I was talking about building my amp for pure stereo with volume control and a second line in straight to the amps for surround duties before...
In another thread I found this gem:
http://digitalanaloguediy.com/attenuator.html
Or this one:
http://www.hificollective.co.uk/components/potentiometers.html
Does this look like a nice solution for volume control? Also, what type is best for CD-player (cinch)->volume->UcD400AD? 10K type?
Is the quality identical?
Thanks,
Yves
In another thread I found this gem:
http://digitalanaloguediy.com/attenuator.html
Or this one:
http://www.hificollective.co.uk/components/potentiometers.html
Does this look like a nice solution for volume control? Also, what type is best for CD-player (cinch)->volume->UcD400AD? 10K type?
Is the quality identical?
Thanks,
Yves
Yves, not sure if thats a good idea or not as I am not qualified to say, however I am thinkning of doing something similar but using my S&B TX102 transformers as a volume control and housing them in the same box as the power amps.
What I dont know is if that would cause some sort of grounding hum type issues.
So far all the above exists as several boxes of parts !
What I dont know is if that would cause some sort of grounding hum type issues.
So far all the above exists as several boxes of parts !
Also see DACT and Goldpoint. Both do the same elma switches plus resistor things.
I have an 8 way DACT remote which is getting wired up in the next few days using an IR remote control gadget from Bent audio to help change volume without moving my fat **** for the couch...
Ed
I have an 8 way DACT remote which is getting wired up in the next few days using an IR remote control gadget from Bent audio to help change volume without moving my fat **** for the couch...
Ed