Noob Question- Toroidal 25vac (ebay)

[whitewind]

I am currently a noob at this chipamp DIY audio stuff but I really want to get into this sort of thing.

Just a couple of questions.

I am planning to purchase and build a Brian GT LM3875 Amplifier Kit (stereo) but having a hard time tracking down a toroidal Transformer. Would the following transformer be compatible w/ this kit?

http://cgi.ebay.com/ws/eBayISAPI.dll...859938899&rd=1

That 25VAC dual secondaries, 600VA runs about 40USD when auction completes.

Is this toroidal worth it?

Is the quality any good?

Are there any places to source toroidals in Canada (spec. Toronto)? ( already checked out plitron, but seems quite expensive)

Thanks for any help.

[homer09]

from what i see in the guide, it seems to be compatible. But the guide says anything over 330VAC is an over kill, this one is 600...

as for quality and such, i have no idea, also pretty new at this and would like a more knowledgable opinion on the matter since im also going to be looking for a toroidal for the same project

the same seller also offers a few different varieties, maybe someone could recommend which is best for a 4 ohm and also an 8 ohm speaker load?

[fish4u]

dunno about Canada...but try here:
Partsexpress
Apexjr

[mrskinny]

You could try Eletrosonic- www.e-sonic.com They sell Hammond toroids,and are cheaper than Plitron.There is also a discount if you order 2 or more.Unfortunately,I don't think that they stock many though. Active Components (next door) also sell the Hammonds- www.active123.com

[whitewind]

Would the :

Avel-Lindberg Inc
*
Input: 2 X 120Vac 50-60 Hz
3 3/4" Dia X 1 1/2" Tall
Output: 2 X 28.4V @ 2.67Amps over 150Va
$22.00ea


from Apex JR be compatible with this kit?
APEX JR Toroidal

Actually getting in Canada isn't that important right now, since my relatives are comming over from the US.

Thanks for your help.

[pinkmouse]

Yes.

[Arius]

It is not the Chipamp kit that dictates the transformer specs, rather it's the voltage rating of the parts that you use.

National's datasheet and/or design guides have all these info. The gist of it is like so:

1) Pick your desired output power into your desired speaker impedance (usually 8R).
2) Using the National data, figure out the max voltage and current required. E.g. for 30W into 8R, we have 22V@2.8A.
3) Transformer voltage should then be 16V (22/1.4), current should be ~ 6A (for stereo). VA rating = (16X2) X 6 = 200VA.
4) Voltage rating for all other parts should then exceed 22V, e.g. diodes, capacitors.
5) Pick a heatsink(s) suitably rated for your desired output power.

Note that using a dual 16V @ 300VA won't give you more power over a 200VA part. It will if you try to use the Chipamp to drive lower impedance loads (e.g. paralled speakers) but doing that will probably exceed the chip's capability.