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Solid State Guitar Amp Forum | DIY Guitar Amplifiers

Solid State Amplifiers => Amplifier Discussion => Topic started by: Stompin_Tom on August 25, 2006, 05:22:38 PM

Title: Cheap transformer... I think it'd be ok for a LM3886?
Post by: Stompin_Tom on August 25, 2006, 05:22:38 PM
Sorry if someone's already pointed this out, but I just saw it. The current isn't too low/voltage too high, is it?

http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=129-035
Title: Re: Cheap transformer... I think it'd be ok for a LM3886?
Post by: RDV on August 27, 2006, 10:37:55 AM
That's about half what you need to get full power out of an LM3886. It will work, but will be woefully underpowered.

Sorry.

RDV
Title: Re: Cheap transformer... I think it'd be ok for a LM3886?
Post by: turbolx5oh on August 27, 2006, 09:41:04 PM
This is more like it.. (http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=120-225)

This is the one I'm using for my LM3875 Chip Amp Guitar Amplifier. (http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=122-615)
Title: Re: Cheap transformer... I think it'd be ok for a LM3886?
Post by: Stompin_Tom on August 28, 2006, 11:05:34 AM
Ah... I see. Thanks chaps. for some reason I thought it was 25 + 25 volt secondary instead of 12.5 + 12.5. I just didn't look carefully enough. I've been searching around the internet for a deal on a transformer, but I'll probably just go with the toroidal. That can power two chips, where as the cheaper one turbolx5oh pointed out only powers one, correct?

I haven't found anywhere that can compete with part express, yet. Except maybe ebay, but you have to be lucky.
Title: Re: Cheap transformer... I think it'd be ok for a LM3886?
Post by: turbolx5oh on August 28, 2006, 11:14:44 AM
If you are going to power 2 of them I would just spend the extra $5 and get the 250VA torroid.

http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=122-625
Title: Re: Cheap transformer... I think it'd be ok for a LM3886?
Post by: Stompin_Tom on August 28, 2006, 11:28:21 AM
mmm... So that extra bit of current would make a difference? I'm no electrical engineer... I've had a hard time wrapping my brain around current vs. voltage. Theoretically, can you run too much current into a chip? I imagine so, but, again, I'm not sure how to think about current.

Maybe I'll look for an article somewhere explaining (in very basic terms) current... Thanks.
Title: Re: Cheap transformer... I think it'd be ok for a LM3886?
Post by: turbolx5oh on August 28, 2006, 11:42:14 AM
A transformer is like horsepower in a car.  You can never have too much in my opinion.  The amp will only use what it needs.
Title: Re: Cheap transformer... I think it'd be ok for a LM3886?
Post by: RDV on August 28, 2006, 02:09:27 PM
You can over-voltage but it would be hard to over-current.

I'm using a 160VA 22 + 22 volt toroid to power two and it does fine but that's about as low as you can go for two. The 220 VA would give you all the power you'd need.

I've run a single LM3886 on a 18 + 18 volt 56 VA transformer and it was loud as hell!

RDV
Title: Re: Cheap transformer... I think it'd be ok for a LM3886?
Post by: turbolx5oh on August 28, 2006, 03:27:02 PM
Quote from: RDV on August 28, 2006, 02:09:27 PM
I'm using a 160VA 22 + 22 volt toroid to power two and it does fine but that's about as low as you can go for two. The 220 VA would give you all the power you'd need.
What size fuse do you have on the mains?
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