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Old 21st April 2004, 12:49 AM   #1
Zemo is offline Zemo  United States
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Default Want to build mono blocks, quick question.

Hey there everyone! I'm glad I found this site! Many helpful people and great information.

I'm about to begin my first Gainclone amplifier, but I want to build a monoblock design. 2 monoblocks in a single chassis, if possible (space). I do, however, have a couple questions.

- do I keep the two seperate amps (toroid, rectifier, amp) completely seperate by tying nothing to the case? Or should I tie their grounds together?

-If tied to the case, I was reading something about using a resistor or a resistor and capacitor.....can someone clear this up for me?

-As far as power considerations go, what voltage toroid should I be looking at? Each monoblock will be powering one 4ohm speaker (uniform). I read that 22V would work well, but that was in reference to a stereo amp. Should that be changed to some other value for a monoblock?

- Is it preferable to power both toroids off of one power cable going into the amp? or should I have it running off of two seperate cables?

As you can guess, my electronics knowledge isn't exactly up to snuff..

thanks!
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Old 21st April 2004, 03:34 AM   #2
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In my dual mono amps I had to tie the output grounds together (through the chassis, otherwise I had some interferences.

You might use resistor or thermistor to tie it to the chassis (10ohm or so). I'm not using any resistor.

If you are using 4ohm speakers you shouldn't go high with voltage. Probably 18-20V AC would be good choice. I attached a graph showing output power vs voltage supply for a given impedance. It seems like 28V DC (on rails) is an upper limit for 4 ohms.

I wouldn't use two separate cables, one should be fine.
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Old 21st April 2004, 04:19 AM   #3
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And while your at it, running one big toroid will be easier and cheaper, since your mounting both chips in the one case anyway.

That way, you only need to rectify one main toroid, and not two smaller ones.

Hope that makes sense.
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Old 21st April 2004, 04:20 AM   #4
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Unless your intending on running one toroid per rail of course...
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Old 21st April 2004, 04:36 AM   #5
Zemo is offline Zemo  United States
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running one toroid? doesn't that take it away from the dual monoblock setup? isn't monoblock two seperate amps being powered from two seperate powersupplys?
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Old 21st April 2004, 04:40 AM   #6
Zemo is offline Zemo  United States
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you think this'd work well for my purposes? (I'd be using two of these) http://www.partsexpress.com/pe/showd...number=122-620
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Old 21st April 2004, 04:49 AM   #7
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Quote:
Originally posted by Zemo
running one toroid? doesn't that take it away from the dual monoblock setup? isn't monoblock two seperate amps being powered from two seperate powersupplys?
He's right, you know...

To be a TRUE audiophile's monoblock, you'll need a
toroid for EACH rail, on BOTH channels. On as many
chassis as you can afford for each component. Got
to keep that all-important isolation.

But seriously...

Keep it simple, but not too simple. Since the amps
have good power supply rejection, I'd go with the
single transformer and maybe separate rectifiers
and filter caps for each channel, if you're feeling
spendy.

I tried a regulated supply for my LM3886 amp, but
the power supply then becomes more complex
than the amplifier and can't handle a large loud-
speaker's current demands very gracefully. And
I had some problems with oscillations. Again,
keep it reasonably simple and just enjoy the
music.

--Damon
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Old 21st April 2004, 04:51 AM   #8
Zemo is offline Zemo  United States
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Alright, so one toroid to two rectifiers, to two amp boards.... isn't that exactly what BrianGTs kit is?
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Old 21st April 2004, 04:52 AM   #9
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Quote:
Originally posted by Zemo
you think this'd work well for my purposes? (I'd be using two of these) http://www.partsexpress.com/pe/showd...number=122-620
It seems to be fine for your purpose.
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Old 21st April 2004, 05:14 AM   #10
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Yeah, so more or less, your really just building a stereo amp : )
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