I have a Velleman K4003 30W stereo amplifier kit that requires 2x12VAC / 2A power supply.
Can anyone tell me very simply how to power this from mains?
I mean whats the simplest way? Would this work?
http://store.qkits.com/moreinfo.cfm/PS1220
Or if I HAD to use one of those internal transformers how would it all hook up?
Say I buy a 12V 50VA chassis mounting mains transformer. I wire that up to the PCB, then I can wire up a DC input jack so it looks like:
Amp PCB > Transformer > DC input jack
What type of mains plug would I use to feed into the DC input jack because they are all transformers anyway right?
Any help is appreciated! Pictures and links would be useful
Can anyone tell me very simply how to power this from mains?
I mean whats the simplest way? Would this work?
http://store.qkits.com/moreinfo.cfm/PS1220
Or if I HAD to use one of those internal transformers how would it all hook up?
Say I buy a 12V 50VA chassis mounting mains transformer. I wire that up to the PCB, then I can wire up a DC input jack so it looks like:
Amp PCB > Transformer > DC input jack
What type of mains plug would I use to feed into the DC input jack because they are all transformers anyway right?
Any help is appreciated! Pictures and links would be useful
You need 2x 12Vac supplies. After rectification to DC this is ~16Vdc for each 'rail'. So,to run it from DC,you'll need (+16)-(0)-(-16) Vdc.
It would probably run fine at +/-12V,but with reduced power.
If you can find some 12VAC "power packs" like those,you can use two of them.
The best option might be to get a standard 2x 12Vac/2A power transformer,and put it all in a case.
It would probably run fine at +/-12V,but with reduced power.
If you can find some 12VAC "power packs" like those,you can use two of them.
The best option might be to get a standard 2x 12Vac/2A power transformer,and put it all in a case.
Yes, ok. So I have to buy a transformer but then I still don't know what type of mains cable to hook up to it.
As I said before it will look like:
Amp PCB > Transformer > DC input jack > DC output jack mains cable.
Again, what type of mains plug would I use to feed into the DC input jack because they are all transformers anyway right?
As I said before it will look like:
Amp PCB > Transformer > DC input jack > DC output jack mains cable.
Again, what type of mains plug would I use to feed into the DC input jack because they are all transformers anyway right?
myspacer00 said:
You seem to have a hazy grasp of the power side, which is dangerous. The usual system is,
230V AC mains ->Transformer ->Rectifier & Smoothing -> Amplifier
With the K4003 kit, rectifier and smoothing are on the amp PCB, so you'll be needing a dual (0-12, 0-12) secondary or centre-tap 12-0-12) secondary transformer, and taking the appropriate three wires to the amp PCB. The transformer must be fitted in a ventilated case away from fingers, with 3-core 5A mains cable, L & N to the transformer primary, cable earth wire to the case, 13A plug (with 2A fuse) on the other end. A switch can be fitted to the case along with the other audio connectors if the amp PCB is to be in the same case.
The "illustrated English manual" clearly shows how to connect either type of transformer. Read, seek live help closer to home if you don't understand it. Rapid Electronics sell a suitable transformer, the 12V+12V 50VA, and various cases you could mount everything in.
You could probably create the required split-rail DC supply with two 12VDC adaptors, but that's in lesson #2.
Mains -> DC adaptors are not transformers, though they may contain one.
I have now done my reading. I have done a lot of soldering and such but have never had to deal with anything other than basic 9v or 12v battery power.
I have bought a suitable transformer and I have fully assembled the amplifier.
I am now looking for a set of decent component speakers to go with my project.
Any advice on what type to get? I was thinking of just salvaging some from some car boot sale purchases but the quality may be a bit of a gamble. I would rather buy new.
Any advice?
Thanks.
PS: I am constructing a stereo speaker box out of probably black walnut, which will house all the gubbins. Basic idea is something around the size of a large DAB radio (probably bigger) with a simple line in for an MP3 player. All schematics have been drawn up.
If I was to house the transformer inside the speaker box how would I attain the proper ventilation?
I have bought a suitable transformer and I have fully assembled the amplifier.
I am now looking for a set of decent component speakers to go with my project.
Any advice on what type to get? I was thinking of just salvaging some from some car boot sale purchases but the quality may be a bit of a gamble. I would rather buy new.
Any advice?
Thanks.
PS: I am constructing a stereo speaker box out of probably black walnut, which will house all the gubbins. Basic idea is something around the size of a large DAB radio (probably bigger) with a simple line in for an MP3 player. All schematics have been drawn up.
If I was to house the transformer inside the speaker box how would I attain the proper ventilation?
if the speaker is sealed loading then no ventilation.myspacer00 said:
If you go for a driver that needs vented loading then you have only one vent (generally) and this does not ventilate well.
What you need is a two compartment box. One dedicated to the drivers and their loading requirements
The other dedicated to the amplifier and it's cooling requirements.
BTW,
50VA is a bit small for a 30+30W stereo amplifier.
A good value for performance spec would be VA=1.5 times total maximum output power, i.e.100VA.
AndrewT said:
The 60W includes about 35W of sales hype.
"# music power output: 2 x 30W / 4ohm"
http://www.quasarelectronics.com/vk4003.htm
Yes the manual said that 50VA was recommended. So maybe I should buy a project box from maplins to house the transformer.
As you can tell im a complete newb when it comes it audio based electronics. I am still a bit confused as to what type of component speakers would be best for this amp.
If someone could link me to 1 or 2 examples of suitable speakers that would give me something to go off.
Any help is greatly appreciated!
As you can tell im a complete newb when it comes it audio based electronics. I am still a bit confused as to what type of component speakers would be best for this amp.
If someone could link me to 1 or 2 examples of suitable speakers that would give me something to go off.
Any help is greatly appreciated!
myspacer00 said:
It's a tricky one as the amplifier will drive virtually any 4R-8R speaker system (bearing in mind it's only low wattage and modest quality, there's no point in going too upmarket), so it comes down to what you want to pay and design skills.
Years ago I took a similar amp to work along with an old cassette deck and an old pair of hi-fi speakers and ran it in the office at lunch-time, very nice too in a small room. I suggest looking round for S/H domestic speakers to suit, it's difficult to compete on price and quality building your own at the budget end.
There's a similar thread in the Chipamp forum ATM, have a look.
Ok, I have made a prototype board with all the components mounted and connected.
I just want to make sure I have connected the transformer correctly.
12v - Connected to VA on Amp
0v - Connected to GND next to VA
12v - Connected to VB on Amp
0v - Connected to GND next to VB
120v - Connected to mains live
0v - Not connected
120v - Connected to mains neutral
0v - Not connected.
Someone from Velleman on their forum said that only live and neutral wires are needed as the earth cannot be connected to a transformer. Is this correct?
I just want to make sure I have connected the transformer correctly.
12v - Connected to VA on Amp
0v - Connected to GND next to VA
12v - Connected to VB on Amp
0v - Connected to GND next to VB
120v - Connected to mains live
0v - Not connected
120v - Connected to mains neutral
0v - Not connected.
Someone from Velleman on their forum said that only live and neutral wires are needed as the earth cannot be connected to a transformer. Is this correct?
no.
you need to connect the primaries in series. then connect 120 to Live and 0 to Neutral.
The ground is for the secondary centre tap.
The other two AC connections ar for the remaining two secondaries.
But before you power this up you should build yourself a mains light bulb tester.
This is to prevent you blowing up your project and potentially taking you with it.
you need to connect the primaries in series. then connect 120 to Live and 0 to Neutral.
The ground is for the secondary centre tap.
The other two AC connections ar for the remaining two secondaries.
But before you power this up you should build yourself a mains light bulb tester.
This is to prevent you blowing up your project and potentially taking you with it.
To elaborate on AndrewT's reply, neutral (blue) to the left-hand 0V in your sketch, link the left 120V to the other 0V, line (red) to the right-hand 120V. A new transformer should come with this information.
The Vellemann forum is correct, the earth wire is not connected to the transformer primary (high-voltage) side but connected to the amplifier 0V and to any exposed metalwork on your case (shown as point 'E').
The Vellemann forum is correct, the earth wire is not connected to the transformer primary (high-voltage) side but connected to the amplifier 0V and to any exposed metalwork on your case (shown as point 'E').
An externally hosted image should be here but it was not working when we last tested it.
Well I have just re-wired it all up according to cpemma's diagram only to come back and read AndrewT's post lol.
Don't worry I won't be powering this on anytime soon. Need a 2A fuse for the mains socket anyway.
Maybe a 3rd party is needed to decide which wiring method will work and more importantly which is the safest.
Thanks for all your help guys!
Don't worry I won't be powering this on anytime soon. Need a 2A fuse for the mains socket anyway.
Maybe a 3rd party is needed to decide which wiring method will work and more importantly which is the safest.
Thanks for all your help guys!
AndrewT said:
Duh! You're right, in effect you're creating a centre-tap on the secondary. More haste, less speed. Corrected.
I thought linking at the transformer (if it's got solder tags rather than a toroid's leads) might be tidy and leave a point on the board for a wire to chassis and the mains safety earth. With a toroid it's easier to do as you say.
A quick multimeter resistance check will verify if the windings are as believed.
- If the left pair of 0V and 12V secondary terminals have a low resistance (and similar for the right pair) but the meter reads open-circuit for the middle pair (12V & 0V) wire as shown on the diagram
- Similarly on the primary side, the left pair and right pair of 0V and 120V should give a reading probably under 100 ohms, the middle pair (120V & 0V) should read open-circuit.
- Americans and others on 120V mains will of course connect the two primaries in parallel, not serial.
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