6 Channel Amp Wiring Advice

[thunk303]

Hey guys.

So, at long last I have completed all the metal work and have started the final assembly of my 6 channel LM4780 amp. I am writing to bounce/check some wiring with people mainly because this is my first amp build and I really don't have a clue what I'm doing.

To start, I have 3x400VA toroidal's, each powering 2xLM4780 boards from AudioSector. This is his recommended specs so all good there.

Now for the stupid questions:

1. The 'blue & brown' wires coming into the transformers are AC so I can connect them either way to the 'red and black' from the transformers?

2. The transformers have dual 22v secondaries (green+blue/green+blue) and the boards have pads marked AC1(+,-) AC2(+,-) before the rectifiers. So as long as I connect a winding to AC1 and the other to AC2 I should be good?

3. I have a some CL60's to limit current inrush that I will wire in parallel with the transformers, I have heard of people on this forum use multiple CL60's, is there any advantage to this?

I hope this all makes sense to somebody and am excited to finally finish the project.

Cheers all.
Dean

PS. Included a pic of my workshop mono OB, made with spare/free parts just for a laugh.

[madtecchy]

Hi Thunk. I think you meant to say wire the cl60's in series with the transformer .
Regards Ian

[pinkmouse]

Nice neat build.

1) Yes, but make sure they're all the same way round. However, I'd put a fuse in line with each traffo, rather than relying on just one.

2) Yes. I assume you'll be linking the AC rails between pairs of amps?

3) You should be fine with just the one CL60 per traffo, but better practice is to disconnect the CL60 after warm up with a relay. Search on "soft start circuit" for some examples.

And finally, I hope you don't have any metal running through the middle of that transformer bracket, that would created a shorted turn which would be very bad news indeed.

[thunk303]

I meant parallel but will now be wiring them in series, cheers Tecchy.

Answers
1. They will all be wired the same way, I have a fuse & DPDT for each traffo.
2. I will be linking them between pairs using terminal blocks.
3. The 4 long bolts are clamping the traffo's in place, the center is hollow and I have rubber/alloy/rubber clamped between each one for mechanical/electrical isolation.

Questions
3. Will I be safe using only the CL60 for the moment and getting a 'soft start circuit' later on? (read 'broke')
4. Is there an electrical/audible cost to using CL60's?
5. The traffo has 2x115V primaries, I connect them is series by connecting the black from primary 1 to the red of primary 2, then soldering and heat shrinking them, was this correct?


Cheers
Dean

[thunk303]

Questions
3. Will I be safe using only the CL60 for the moment and getting a 'soft start circuit' later on? (read 'broke')
4. Is there an electrical/audible cost to using CL60's?
5. The traffo has 2x115V primaries, I connect them is series by connecting the black from primary 1 to the red of primary 2, then soldering and heat shrinking them, was this correct?


Cheers again
Dean

[frank1]

Originally Posted by thunk303

Hey guys.

So, at long last I have completed all the metal work and have started the final assembly of my 6 channel LM4780 amp.

I don't see adequate smoothing in any of the photos?

Frank

[thunk303]

Hey Frank.

Smoothing of the psu or the metalwork or??

Dean

[AndrewT]

I suggest you move to Audiosector.
Peter's implementation is quite different from the majority here, including me.

[AndrewT]

For 220/240Vac I suggest a pair of series connected CL60 for the transformer Primary.
This pair could reliably start up a 1200VA transformer, or three 400VA transformers, but will run hot some of the time.
Bypass those CL60 soon after they have achieved their soft start purpose.

I also agree that every transformer has it's own close rated fuse.

[thunk303]

G'day Andrew.
I didn't even think to post this under AudioSector, perhaps a moderator can move it? Thanks in advance.

So, Each transformer has its own fuse and switch so I can use/disable 2/4/6 channels depending on whats connected.

This also allows/requires me to use a separate CL60 for each transformer. If 2 in series is enough for all 3 400VA traffo's then would 1 each work well?

I will have to do some research on the soft start idea and implement it later, money is very tight at the moment. Do you have any suggestions on where to start looking and what to look for?

Cheers
Dean