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Old 17th April 2006, 12:13 PM   #1
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Default newbie toroidal question (LM3886)

Hey all, I'm trying to make a guitar power amp using 1xLM3886.
I did some research on forum and I read the LM3886 specs. I found out that I should use 25V sec. toroidals for 50W/8ohm. Still I couldn't find any info about VA ratings. It's said that 160VA-330VA is o.k. but there is a considerable price difference between these ratings.
Which VA rating is good for a mono 50W/8ohm amp.

PS: BTW are these good products : http://www.hrdiemen.com/products/ind...ewSection&id=3

a 2x24V 250VA is approximatly 50€ = 60$ - is this price ok?

Thanks very much
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Old 17th April 2006, 12:34 PM   #2
RDV is offline RDV  United States
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Much has been said here about huge transformers but I've gotten good results with as little as 56VA. I'm running one now on 96VA and it kicks butt.

This is for sure, that 160VA is plenty for one LM3886. I use a 160VA torroid for my stereo amp and it's plenty.

RDV
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Old 17th April 2006, 12:59 PM   #3
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thanks RDV

http://www.hrdiemen.com/products/ind...roduct&id=3692
this one (160VA 2x24V) is 45$ in my country.

are these prices ok?
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Old 17th April 2006, 01:25 PM   #4
RDV is offline RDV  United States
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That seems alright to me though I have no idea what Turkey is like. I paid at least that much here.

If you get that one you can add another channel later if you want also.

Good luck and have fun.

RDV
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Old 17th April 2006, 01:57 PM   #5
AndrewT is offline AndrewT  Scotland
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Hi,
I agree with Rdv.
160VA will run upto 100W of ClassAB.
So you can have 50W+50W into 8ohm (stereo) or 100w into 4ohm(mono) from this transformer.

24Vac will give a maximum open circuit voltage of about 39Vdc allowing either 40V or 50V capacitors to be used. I suggest +-6m8F for the 8ohm speaker or +-12mF for 4ohm speaker.
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regards Andrew T.
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Old 17th April 2006, 03:46 PM   #6
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whats the VA rating for only one 50W/8ohm channel?
80VA right?

thank you for help
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Old 17th April 2006, 03:50 PM   #7
RDV is offline RDV  United States
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Quote:
Originally posted by cb951303
whats the VA rating for only one 50W/8ohm channel?
80VA right?

thank you for help
In my opinion you could.

RDV
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Old 17th April 2006, 04:57 PM   #8
dfdye is offline dfdye  United States
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Quote:
Originally posted by cb951303
whats the VA rating for only one 50W/8ohm channel?
80VA right?

thank you for help
That's what I am using and it is working well for me so far.
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Old 17th April 2006, 05:08 PM   #9
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I'll buy a 80 or 100VA 2x24V toroidal
every one thanks for your helps
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Old 30th April 2006, 05:08 AM   #10
! is offline !  United States
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Quote:
Originally posted by RDV
Much has been said here about huge transformers but I've gotten good results with as little as 56VA. I'm running one now on 96VA and it kicks butt.

This is for sure, that 160VA is plenty for one LM3886. I use a 160VA torroid for my stereo amp and it's plenty.

RDV

I have a 280VA running two LM3886 behind a regulated supply (so even further losses) @ 35V and that is plenty too. IMO, a budget-conscious builder could use 50VA for a low-volume amp or 100VA (these per-channel) for two channel use.

Now I have this urge to hook up a measily 2A 24V CT tranny I have lying around, It'll probably make me feel like I wasted money on the 280VA torriod for normal listening levels, but then again, who builds for normal listening levels?
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