Solid State Guitar Amp Forum | DIY Guitar Amplifiers

Solid State Amplifiers => Amplifier Discussion => Topic started by: armstrom on September 14, 2011, 04:02:28 PM

Title: Power transformer: Inside or outside chassis?
Post by: armstrom on September 14, 2011, 04:02:28 PM
I'm starting to work on a stereo guitar amp using a pair of LM3886 chips. My 2 x 25V 200VA toroid arrived the other day and it JUST fits inside the hammond chassis I plan to use. So, are there any disadvantages/issues with mounting the transformer inside the chassis? Or should I stick to mounting it to the top of the chassis like you usually see.

Thanks!
-Matt
Title: Re: Power transformer: Inside or outside chassis?
Post by: joecool85 on September 14, 2011, 04:06:56 PM
Quote from: armstrom on September 14, 2011, 04:02:28 PM
I'm starting to work on a stereo guitar amp using a pair of LM3886 chips. My 2 x 25V 200VA toroid arrived the other day and it JUST fits inside the hammond chassis I plan to use. So, are there any disadvantages/issues with mounting the transformer inside the chassis? Or should I stick to mounting it to the top of the chassis like you usually see.

Thanks!
-Matt

I always mount mine inside the chassis.  That said, in theory there could be less "noise" with the transformer on the outside of the chassis.  The key words in that last sentence were "in theory", I wouldn't bother and I would put it right inside the chassis with no worries.
Title: Re: Power transformer: Inside or outside chassis?
Post by: armstrom on September 14, 2011, 04:13:45 PM
That's what I'm leaning toward as well. There's tons of free space inside the chassis. That 200VA toroid is a heavy beast though :) Not exactly tube amp PT territory, but big by SS standards. I wanted some extra capacity since I'll be running a pair of LM3886 chips at 50W into 8ohms (well, as close to 50W as I can get, the 25V AC secondaries should get me close to the +/-35V DC I need for 50W into 8 ohms. The speakers are a pair of Weber Ceramic Sig 12B. All wrapped up in a (hopefully!) lightweight 2x12 combo with a fiberglass composite cabinet. My goal is to keep this thing as light as possible for gigging musicians. 40lbs is the target weight, but we'll see.

-Matt