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Old 17th May 2004, 04:02 PM   #1
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Default Power requirements for 7 channel gainclone amp?

So I ordered the gainclone amps from Brian a couple of a couple of months ago.

Rite now I have completed one 2 channel amp and would like to move onto the next project. I have six of the amps built and I just need the caps for the 7th one.

Anyways here is what I would like to have.

1)Use a single outlet, meaning that I only have a single power cord going into the amp.

2)I would like to leave open the option of bridging up the front channels someday.



My questions though are
-Can I use a single power supply to power all seven channels? This would be using the parts from brians powersupply design.
-What sort of torroid should I use, do I even need to go to dual torroids and split it up so one powers the fronts and center and the other powers the rear and the surrounds. Will this effect the single outlet?
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Old 17th May 2004, 08:49 PM   #2
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AJ,

I'm not sure what everyone else thinks, but I have used 2 x 300 VA toroids in my 6 channel amp that uses Brian's boards,

One transformer powers all the left front & back and centre channels, the other powers the right front and back and the remaining channel.

I still need one more premium kit to complete it, so it's running on four channels only at the moment.. and works fine.

For seven channels I expect that the rectifier board could be starting to overload if you only used one. It might be best to use at least two.

Finally, you can wire two transformers to one INLET (not outlet), but it's probably best to fuse them individually.

My amp is use for Hi-Fi more often than for HT, so I decided that I would design the front left & right to be as good as possible, and the rest of the channels took a back seat. So for Hi-Fi use, the left and right have their own 300VA transformer.....

SteveM
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Old 17th May 2004, 10:03 PM   #3
KT is offline KT  United States
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I'm not any sort of authority on these things, but it seems to me that for strictly HT use, the center channel should be of the highest quality, followed by the front L/R channels, and lastly the rear L/R channels (for 5.1), if one had to ration one's resources.

I'm going to be building a five channel unit myself, and I was thinking of using either a high VA rated TX for the center AND front L/R channels (or more ambitiously, a separate high VA rated TX for the center, and a separate high VA TX for the front L/R), followed by a lower VA rated TX for the rear L/R.

I experimented a little while ago with the front side of my HT setup and found that the speakers that sounded most musical to me were fine for the L/R channels, but weren't quite intelligible enough for the center vocal channel. The balance was much better when I replaced the center with a thinner, but clearer sounding speaker.

Because of this I plan on using the LM3875 on the center channel, and the LM1875 on the other channels, with matching speakers.

I'm sure this can also be dealt with through the processor EQ, but I'm planning to take the signal directly out of the DVD player's analog outs.

Just a thought.
KT
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Old 17th May 2004, 11:44 PM   #4
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I'm also looking into a 5.1 channel amp for home theatre. I've currently got a 300va Toroid, will it work fine to just leave my current 2 channels for fl/fr and then add a center channel, then have the rears off another 300? Or should I have the fronts off there own 300va then center and rears on other 300?? Would it make any difference under movie load conditions? or only under high loads?
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Old 17th May 2004, 11:55 PM   #5
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Thought I'd comment on this one.

Where I was working over the summer break, the company that I was working for built a 8 channel gainclone (actually, it was a similar variant). They simply used a custom wound 1000VA toriod that went through one rectifier circuit.

Worked flawlessly. The only main problem was the large amount of heat produced, as it was designed to run at a rather high idle current (can't remember what that value was exactly).

Hopes this helps.
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Old 18th May 2004, 03:47 AM   #6
MWP is offline MWP  Australia
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I built a 8 channel bridged gainclone.
I used 2 * 500VA torodials in parallel.

Not enough to power the full 8 chans at full output power though.
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Old 19th May 2004, 12:00 AM   #7
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Quote:
Originally posted by MWP
I built a 8 channel bridged gainclone.
I used 2 * 500VA torodials in parallel.

Not enough to power the full 8 chans at full output power though.
So two 625's should work then. What components would you have to change around though?
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Old 19th May 2004, 12:16 AM   #8
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Quote:
Originally posted by MWP
I built a 8 channel bridged gainclone.
I used 2 * 500VA torodials in parallel.

Not enough to power the full 8 chans at full output power though.

Quote:
Originally posted by AJ Bertelson
So two 625's should work then. What components would you have to change around though?
AJ, please note that MWP's 8 channel amp was bridged and would therefore need approx. 4 times the power capability to run at full power.

I would expect 2 500VA toriodals to be fine for a non-bridged amp. The only other small problem you may have is that Brian's rectifier PCB is designed to power 2 channels only. So you'll need to work how to connect 4 power output to 7 channels (assuming you use two rectifiers)....

SteveM
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Old 19th May 2004, 01:33 AM   #9
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Quote:
Originally posted by BlackDog
So you'll need to work how to connect 4 power output to 7 channels (assuming you use two rectifiers)....
Pardon my ignorance with this but why if I was running 4 channels off of a single rectifier bridge why could I just run a single wire off the bridge then solder 4 wires onto that single wire?

please don't laugh as I am quite new to this
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Old 19th May 2004, 01:58 AM   #10
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If you are refering to powering all 4 channels off the one bridge setup, then this would overload the bridge, because it was designed with powering 2 gc channels in mind. (Please correct me if I'm wrong)
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