# Linear Power Supply for Amp Camp Boards (Question)

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#### Jennifer G

I just ordered the Amp Camp PCB's and going to be building it pretty soon -- just so I can compare it to my LM3886, and perhaps even use it in a bi-amp situation (speaker rewire).

I've decided I'd like to use a linear power supply and build it into a single case, sharing the same dual secondary Antek toroidal transformer. I'll probably build two separate dc supply boards, one for each secondary and amp board. (They would be unregulated if this is okay.. I believe the laptop supply bricks are regulated aren't they?)

My question is, would a 15V 200VA antek toroidal be good for this scenario? (has 2 secondary outputs). 15V x 1.4 = 21V and it could peak a bit higher. The 18V transformer would be 18V x 1.4 = 25.2V and even more with a peak. So isn't the 18V too large of a transformer for this project and the 15V would be the way to go?

Each channel would have 100VA (since it is a 200VA with dual secondaries). This isn't overkill is it? Should I use a 100VA for 50VA per channel instead? The higher the VA the better the regulation though I hear. So I dunno!

Any advice would be greatly appreciated.

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#### AndrewT

look at the AC current rating.
That is the maximum continuous current that the transformer can supply to a resistor load.
200VA 15-0-15Vac has an AC current rating of 6.67Aac

The maximum DC current from a transformer feeding a capacitor input filter is ~50% of the AC current rating i.e. ~3.4Aac
Using a 200VA 15-0-15Vac transformer at a total bias of 3.4Adc will run hot.

#### sippy

Hi Jennifer G,
I built ACA for my god-daughter and used a 18v / 300va trafo followed by simple 10,000uf - 0.47 5w - 10,000uf + 10,000 C-R-C filter.

Trafo runs warm, but then the whole amp runs warm.... tis the nature of the 'beast'.

#### propitious

Paid Member
Jennifer: See my reply on your other thread. Personally, I would use an Antek, 18V 200VA transformer because it only costs a little more than a 100VA, but a 100VA would supply enough to work, since you only have about 1 A Iq per channel. Your rails would probably be somewhere between 22 and 23 VDC under load, and should sound very good.

#### Jennifer G

I got two recommendations for 18v+18v @ 300VA, and one for 18v+18v @ 200VA. I'd prefer the 200VA if it would work as well as the 300VA because it costs less and is smaller. But I won't sacrifice sound for \$\$ or space

I need to decide so I can go ahead and order Just got the amp camp pcb's today -- excited

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#### Jennifer G

Hi Jennifer G,
I built ACA for my god-daughter and used a 18v / 300va trafo followed by simple 10,000uf - 0.47 5w - 10,000uf + 10,000 C-R-C filter.

Trafo runs warm, but then the whole amp runs warm.... tis the nature of the 'beast'.

By any chance would you have a schematic for the dc supply board you used for your ACA's? I can do a perf board / point-to-point hybrid.. like solid core copper wire as the traces of the board

#### wdecho

No need to purchase a PS board unless you like the convenience. I do not use a board at all. Hot glue caps to something standing up and wire everything up. Just be careful inside a "Hot" amp testing. You could always cover them with plastic to be safe. There is not much involved with building a PS for FW amps.

As far as a schematic, just standard Papa schematic.

#### Jennifer G

No need to purchase a PS board unless you like the convenience. I do not use a board at all. Hot glue caps to something standing up and wire everything up. Just be careful inside a "Hot" amp testing. You could always cover them with plastic to be safe. There is not much involved with building a PS for FW amps.

As far as a schematic, just standard Papa schematic.

Thanks. Could I use the schematic for the CRC power supply in the Nelson Pass F1 manual? I don't know what "standard Papa schematic" would be. Like from which amp manual? Does he use the same CRC network and CL160's etc in every amp?

#### sippy

Thanks. Could I use the schematic for the CRC power supply in the Nelson Pass F1 manual? I don't know what "standard Papa schematic" would be. Like from which amp manual? Does he use the same CRC network and CL160's etc in every amp?

Yes, that is what I described in my previous post - though minus the cl-60 as I forgot to order some.
I'll use the same supply when I do my ACA (maybe a few more uf's though), but bigger for Zen v4 and F5 - got to get building model gliders out the way first though

#### Jennifer G

So basically just use exactly the same power supply in the F1 for the ACA right? It's an 18V + 18V transformer and only provides positive voltage to the amp boards (like the ACA wants)

Use all the same values in the CRC network?

#### propitious

Paid Member
You could use the same PS circuit that Michael used for his Circlotron. The V1 would go to one channel and V2 to the other. That is like the PS design that I used on my ACA, except I used chokes (CLC) instead of the CRC, but that is not necessary for you. You can vary the amount of caps you want to use, but the 47K that Michael uses will sound great on a ACA. BTW, the pair of 100VA Anteks that I use on my ACA do not even get warm. The diode bridge does get warm though.

#### Jennifer G

You could use the same PS circuit that Michael used for his Circlotron. The V1 would go to one channel and V2 to the other. That is like the PS design that I used on my ACA, except I used chokes (CLC) instead of the CRC, but that is not necessary for you. You can vary the amount of caps you want to use, but the 47K that Michael uses will sound great on a ACA. BTW, the pair of 100VA Anteks that I use on my ACA do not even get warm. The diode bridge does get warm though.

When you use a single Antek (100va in this case) for each channel, you wire the secondaries together in parallel? (since the amp board doesn't need both pos and negative voltages)

#### propitious

Paid Member
Yes, but using one 200VA for both channels will work about as well...whatever you have room for and budget for.

#### AndrewT

the output from the rectifier is not positive,
The output from the rectifier is two wires. One is positive with respect to the other. And that is the same as saying that one is negative with respect to the other.
(since the amp board doesn't need both pos and negative voltages)
NO !!!!
You feed both wires to the circuit, because the circuit NEEDS both wires.
Remember I said use a twisted pair TWO WIRE connection between modules.

#### Bare

It's Also possible to use a Pair of Laptop power supply bricks.
Just as in the DIY 'store' ACA Kit offering
Typically these run about 10\$ each and are a simple solution.
Certainly work well by all reports.
How well ? is for one to decide at.. any... later date.

#### Jennifer G

the output from the rectifier is not positive,
The output from the rectifier is two wires. One is positive with respect to the other. And that is the same as saying that one is negative with respect to the other.
NO !!!!
You feed both wires to the circuit, because the circuit NEEDS both wires.
Remember I said use a twisted pair TWO WIRE connection between modules.

I know you feed both wires.. to make a circuit. I am saying the ACA does not make use of negative voltage like my LM3886 does for example. In the ACA amp board schematic it shoes +19V there is no -19V is what I'm saying. There is ground and positive voltage (+19v)

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#### Jennifer G

It's Also possible to use a Pair of Laptop power supply bricks.
Just as in the DIY 'store' ACA Kit offering
Typically these run about 10\$ each and are a simple solution.
Certainly work well by all reports.
How well ? is for one to decide at.. any... later date.

switching power supplies are noisy!

#### AndrewT

I know you feed both wires.. to make a circuit. I am saying the ACA does not make use of negative voltage like my LM3886 does for example. In the ACA amp board schematic it shoes +19V there is no -19V is what I'm saying. There is ground and positive voltage (+19v)
the power ground is actually the -ve voltage of the supply.

What you meant to say is that the amplifier uses a single polarity supply and not a dual polarity supply.

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