By a plus and a minus do I get a GND?


I’m new in this electronic environment, I decided to buy a pre-mounted amplifier board.

It would be easy, after all it must be just connect boards to boards, I thought… But now I’m facing a problem.

In the attached file, we have on the first picture what I have from the connection document. On the second picture is what I have done.

So, since today I dont have a 0-200, 0-200 transformer, I decided to use the one I have which is 23-0-23.

So, when I power up, I started to hear a buzzzzzz, and then i saw some smoke coming out from the power board.

Now, do you think I really can connect the -29 and the +29 in order to get the “0” or GND?

thanks in advance.

Best regards


Nope, you get a short. You need to use a transformer that has a -200 0 200v output.

Thank you for your answer.

Yes, I thought on that, but the amplifier board need a DC power. So, I need to pass thought the power board.

Neither of the diagrams can possible be right.

The primary must match the ac supply voltage, which is likely to be either 120Vac or 230Vac.
200V is too far from 230 to be safe. 23V is utterly wrong (is that a misprint for 230V perhaps?)

If you use a transformer which is not designed for mains on the primary you risk starting a fire or
blowing fuses and possibly very high voltages on the secondary.

You must only use a mains rated transformer for powering things from the mains.

You must earth the secondary circuit at some point. Never use a 2 pin connection to the mains,
always have earth and use it.

You must check the primary winding(s) are connected correctly (some have two windings so can be
used in series for 230V and in parallel for 120V, and the phasing must be correct)

You must connect the secondaries correctly - with no power connection you can investigate the windings using
the resistance range of a multimeter. This will show how the windings are arranged, but not their relative phases.

Perhaps post photos of the particular transformer and its label.

Oh and in answer to the subject line, no you create a short-circuit, you get sparks and blown

I decided to buy a pre-mounted amplifier board.

Can you give us links to what you have?

Do you have a multimeter?

Figure 3 on [u]this page[/u] shows a basic bipolar power supply. It’s shown with a center-tapped transformer but a transformer with two identical secondaries can also be used by wiring the secondaries in series and grounding the center connection. If you have two secondary coils they need to wired with the correct phase (so you get 46V from two 23V secondaries).

You’ll need capacitors in order to get DC. It’s possible that there are filter capacitors on the amplifier board but they are usually part of the power supply.

The peak of an AC voltage is 1.4 x the RMS voltage, minus about a 1.4V drop across the bridge rectifier. The capacitor will charge-up to the peak. So, you’ll get about 26.6 VDC from 20VAC. And, a transformer will put-out more than it’s rated voltage with no-load (or with a light load) so it’s a good idea to measure the voltage before connecting an amplifier.

100 / 200 VAC is common in Japan.
Edit: Sounds like you need a 15_0_-15VDC split supply like used in analog circuits.
So, you have a vacuum tube (valve) amplifier that needs + and - 200VDC and +12VDC. I think you have connected the power supply (rectifier) incorrectly but hard to tell from pictures. Post links and datasheets to all components.


Thank you so much for trying to help me in this odd thing.

To let you know what I have, or what I did.I send you the picture of my attempt, and also the connection layout of the amplifier. (the odd thing)

But as I understood from your replies, this connection scheme is wrong.

First I thought the power board could deal with this + and - connected together.

I want to order a transformer but now I’m not sure what kind of secondary widing I need to have.

I also include a picture of the transformer that they indicate for this amplifier. ( I think it is also odd)

Best regards


Ops, sorry I forgot to include the link to the amplifier:


You might have said its a valve amp! Note the voltages are lethal and you need to take great care (if not
confident, stick to low-voltage stuff).

You need that 200V output transformer, its as simple as that. The transformer they suggest has
standard dual-voltage primary and dual 50mA 200V secondaries and dual 6.3V 800mA secondaries too.

You need that transformer and the kit's PSU, or alternatively some DC supplies as described.

Ops, sorry I forgot to include the link to the amplifier:

Actually, it is

Just remove the "?" and all the nonsense following. :grinning:


It took me awhile to figure out removing the "?" and all the crap after it to remove all the unnecessary text.


Thank you Paul__B for the hint.

Regarding my issue, I continue not understanding why they mention to connect the + and the - to the ground on the amplifiier board.

Maybe I did some wrong connection… maybe.

I include some pictures with the connections.

in b1 picture are the two inputs (0-200v DC at 0.05 A )

In the b2 picture the two outputs with the “+” and the “-”.

If I will use one of the “+” and one of the “-”, how can I create a GND by the remaing ones… the other “+” and the “-”?

in the picture b3 and b4 is the connections i did.

I have use a 23-0-23 transformer because it is the only I have. And before order the final transformer I give a try.
But probably this transformer is completely wrong in this set. Rigth?

MarkT, you scared me a bit, actually I’m not confident… I’m thinking to ask for help, to someone more experienced and closer, physically. Let us see.
Thank you for all your inputs.

Best regards

I continue not understanding why they mention to connect the + and the - to the ground on the amplifiier board.

You can do this only if you have two independent power sources. So that is two winding on the same transformer with a full wave rectifier and capacitor on each.
Then you connect these two supplies exactly like this diagram with batteries in place of the two voltage supplies.

Which is what they mean by connecting + to - to get a ground.

If you have a split winding then the center tap becomes the ground and the two ends have a diode on them, each diode points in a different direction. This, along with a capacitor on the end of each diode to ground then gives you two half wave rectified rails one + and the other - with respect to the center tap.

Or you could use a center tap winding like this:-
split 1.png

Not at all sure what your pictures are supposed to show, they are just photographs of some circuit board or other. No actual relevant information here.

The original diagram you posted made no sense at all.

split 1.png