Basic electronics questions.

[Rasped]

I don't have the greatest understanding of electronics. I know the difference between AC and DC, I know volts, watts, hz and ampere. But that's about where it ends.

I thought we could make a word list for new people(like me) to help them understand what we're talking about.
Also, electronics "rules", tips and tricks could be in this thread.

So I'll just start out with what I know, and then a few questions.

Commonly used terms
VA = Volt-ampere, A volt-ampere, in electrical terms, is the amount of apparent power in a circuit equal to the product of voltage and current. Wikipedia
Vac/VAC/vac = Volt, AC
AC = Alternating Current
Vdc/VDC/vdc = Volt, DC
DC = Direct Current
hz = The number of times AC goes from + to - and back in a second.
amp = besides ampere, the word used for amplifier.

The four cornerstones of electrics
A/amp/ampere = "the ampere is a measure of the amount of electric charge passing a point per unit time"
Volt = I can't explain this? Explanations Good explanation by tricky
Watt = volt * ampere. A measurement of the amount of energy consumed.
Ohm = resistance, how hard it is for the current to flow through.Good explanation by krilli

Relations of Volt, Ampere, Ohm and Watt - thanks to V-bro for digging this up


What is a switchmode power supply or SMPS?

A switchmode supply is small and efficient, this is due to the trick they pull by using a switching frequency which is much higher than 50hz or 60hz. At more than 20Khz the efficiency is much better, the transformer can be small and with much fewer windings to generate a lot of power. There are several ways to 'switch' and make a switchmode power supply. Depending on the purity needs, the power, size and temperature. A good example is a computer power supply...

Is it possible to take 2 transformers with an output of 12 vac and combine them to 24 vac?

To answer the questions, yes you can series connect the outputs of two transformers. You can either series the AC voltage, or first rectify them both and series connect the DC.

What are the vac recommendations for the different amps?

Here is the amplifier overview chart made by Marstedt:
http://spreadsheets.google.com/ccc?k...ZWkNDZWc&hl=en

When you divide the DC voltage with 1.41 you roughly get the max AC voltage. Do keep in mind that there are considerations with choosing the voltage like what load the amp should drive. Some amps are 'made for' 8 ohm load, but can also drive 4 ohm load when the supply voltage is chosen lower... For overall stability and low temperature operation it is always a good idea NOT to go for the max. voltage!!

The VAC recommendation for the amps ... well, it's an art, but a rough ballpark is [MAX_POWER_PER_CHANNEL * NUMBER OF CHANNELS] plus 10-20% fudge factor

Complete post by krilli


New questions/requests.

Can someone write something understandable about DC paralleling and serializing?
Can someone write something understandable about AC paralleling and serializing?

@scratchy: Maybe we should move it to the wiki, I will talk to Jan.

Please contribute, I will edit this post

[V-bro]

I think this is also handy to know how they relate to one and other:

[V-bro]

To answer the questions, yes you can series connect the outputs of two transformers. You can either series the AC voltage, or first rectify them both and series connect the DC.

Paralleling is best done at DC voltage...

A switchmode supply is small and efficient, this is due to the trick they pull by using a switching frequency which is much higher than 50hz or 60hz. At more than 20Khz the efficiency is much better, the transformer can be small and with much fewer windings to generate a lot of power. There are several ways to 'switch' and make a switchmode power supply. Depending on the purity needs, the power, size and temperature. A good example is a computer power supply...

I have designed some switchmode DC up converters to run in a car at 12V input and up convert to much higher voltages at really high power and at 94% efficiency. I have a car Truepath and a car AMP15.... There will be a car AMP7 in the future, have the parts ready on the shelve...

[V-bro]

Here is the amplifier overview chart made by Marstedt:
http://spreadsheets.google.com/ccc?k...ZWkNDZWc&hl=en

When you divide the DC voltage with 1.41 you roughly get the max AC voltage. Do keep in mind that there are considerations with choosing the voltage like what load the amp should drive. Some amps are 'made for' 8 ohm load, but can also drive 4 ohm load when the supply voltage is chosen lower... For overall stability and low temperature operation it is always a good idea NOT to go for the max. voltage!!

Read about power supply pumping, which can be an issue with single ended (bridgeable) amplifiers...

[tricky]

Volts are like the pressure the electrons are being pushed pulled with, sometimes called potential.

Sometimes I like to think of electricity as if it might be water, and the wires connecting components like tubes.

In this analogy ...

Electrical charge is e.g. water.
Amps as you say the amount of water past a point in the circuit, and like with electrical charge pretty incompressible, so we know that what goes in must come out.
Volts is the pressure of the water, how hard it is being pushed through the pipes. Note pressure like voltage is relative, you can add and subtract it, which is why you can get the concept of negative pressure perhaps it sould be called suction.
Resistance is the size of a pipe, so a very small pipe would have a high resistance, a piece of wire would be an enourmous pipe. Also if you force water through a very small pipe it pressure will drop, or in our analogy the voltage falls.
A capacitor looks like a presurised water tank, the more pressure the more water it will hold, but it will also have an ultimate maximum size, where it will fail.
Hard to explain inductance with this analogy.

[krilli]

Yep, "pressure" is good. The French also use tension to describe voltage Serves the same purpose.

Amperes = current = "stream" in Icelandic - how fast does the river stream or flow?

It's pretty helpful to think of resistance as "the inverse of conductance". So a pipe that can allow a certain flow has a certain resistance also ... This is useful when understanding why resistors placed in series increase resistance, but resistors placed in parallel with each other decrease resistance. E.g.: add more water pipes in parallel and more water can flow -- and so less resistance.

The VAC recommendation for the amps ... well, it's an art, but a rough ballpark is [MAX_POWER_PER_CHANNEL * NUMBER OF CHANNELS] plus 10-20% fudge factor

The amps that can take about 12V like the Amp6 and Amp32 series would take a minimum of around 35VA, 50VA is better, 80VA and up is very comfortable to the point of being overkill

In the amps that one is normally feeding with around 24V, the rough target is about 80 VA per channel if you plan on a 4 Ohm load, 40VA into an 8 Ohm load. So an Amp4 would be best served with 80VA (or more comfortably 100VA). An Amp11, around 150-200VA. Amp9 at full tilt into all channels at 4 Ohm could make use of a 400VA supply.

It starts to get complicated after that because of the greater flexibility of the stronger amps - different voltages and different loads - so they warrant "custom" VA calculations.

Great initiative btw!

[Rasped]

I understand the basics of parallel and serial connections of DC, how to double the voltage or double the amps of two 9V batteries is no problem for me.

But does this mean you can just feed + into - of another dc supply, and get the voltages added? no problem??

My mind breaks when I try to understand serial AC. Parallel, I might understand, if it is just like DC.

Is it because AC is Phase and 0(that's what we call it in denmark)? and that is like + and - of DC?

Keep the info coming. It is great.

[krilli]

But does this mean you can just feed + into - of another dc supply, and get the voltages added? no problem??

In theory: Yes, indeed!

Then you can run into case-specific problems. I once series-connected a couple of 16V switching supplies. They didn't like each other, so they created quite a bit of noise on the output ... But they added up to 32V total, and worked as expected with regards to power output and all that.

Then there is also the issue of grounding ... any series connected DC power supplies MUST be galvanically isolated from ground. E.g., the DC outputs must never have a direct connection to earth ground in the plug ... If there is such a connection, you create a pretty weird short circuit. Not all supplies are created equal ...

So this series-connection-of-DC-supplies is a YES in theory - you have the correct understanding - but BE CAREFUL in practice

[Scratchy]

I don't have the greatest understanding of electronics. I know the difference between AC and DC, I know volts, watts, hz and ampere. But that's about where it ends.

I thought we could make a word list for new people(like me) to help them understand what we're talking about.
Also, electronics "rules", tips and tricks could be in this thread.

So I'll just start out with what I know, and then a few questions.

Vac/VAC/vac = Volt, AC
AC = Alternating Current
Vdc/VDC/vdc = Volt, DC
DC = Direct Current
hz = The number of times AC goes from + to - and back in a second.
A/amp/ampere = "the ampere is a measure of the amount of electric charge passing a point per unit time"
amp = besides ampere, the word used for amplifier.
Volt = I can't explain this?
Watt = volt * ampere. A measurement of the amount of energy consumed.
Ohm = resistance, how hard it is for the current to flow through.

Is it possible to take 2 transformers with an output of 12 vac and combine them to 24 vac?
What is a switchmode power supply?
What are the vac recommendations for the different amps?

Please contribute, I will edit this post

I know you are going to edit the first post as new info comes in, but a thread with 67 posts is not user friendly to find information.
It would be really cool if all this type of information could be captured in the Tec Doc Wiki similar to what I have started here:
http://wiki.41hz.com/Build-Guide.ashx

What would be even better is if new builders/visitors to the site actually found this info and read/contrubuted to it.
The greatest challenge is presenting the information in an easy to find & read format.

[krilli]

I know you are going to edit the first post as new info comes in, but a thread with 67 posts is not user friendly to find information.
It would be really cool if all this type of information could be captured in the Tec Doc Wiki similar to what I have started here:
http://wiki.41hz.com/Build-Guide.ashx

What would be even better is if new builders/visitors to the site actually found this info and read/contrubuted to it.
The greatest challenge is presenting the information in an easy to find & read format.

True, this is eminently Wikiable. Where would it fit best?

Here: http://wiki.41hz.com/Build-Guide.ashx ?
Here: http://wiki.41hz.com/Basics.ashx ?

Probably the Basics page - that title most strongly indicates this type of content.