OUTPUT TRANSFORMER LOCATION

[ViperDoc]

On most Marshall-style chassis I've seen, the PT is on left side (from underneath), and the OT is more in the center.



I noticed the Mesa Boogie Triple crown looks like it puts the OT on the far right.



I also noticed some VOX amps do the same thing.



Aside from possible weight balance and pure discretion, is their any other reason for that? Just curious, thanks!

[pompeiisneaks]

Separation of the PT and OT can help with coupling hum, but adds the problem that long wire runs can add hum in other places. proximity with the transformers being 180 Deg offset will cancel hum and allow them to be near one another so the higher current/noise parts aren't near the sensitive preamp areas.

Good and bad with both, that can be handled.

~Phil

[xtian]

FYI, for folks who listen to their transformers during layout ("headphone trick"), the choke placement makes a difference! I just did this with my Monkeymatic Black Butte Desktop #2 build. I put the OT and PT on the desk, energized the PT and listened to the OT with headphones. Placed the iron 2-3" apart, oriented so the hum was minimal. Then placed the choke (not connected) in between PT and OT. As you move the choke around, you can HEAR that you're bending the magnetic fields!

So, always involve all three hunks of iron when you're listening for best placement.

[ViperDoc]

That's fascinating. I originally asked because I noticed my 2204 is heavy on one side, but that totally makes sense. I'll have to test your headphone trick on my next amp.

[Snicksound]

Separating transformers this way mostly helps with making the amp more balanced when carrying it. The extra separation doesn't hurt but you really don't need that much separation, and you have the complications of having high current leads close to the input.

Mesa has the advantage of big R&D budget. They can sample many iterations of the PCB and chassis until they find the quietest layout. Their customers pay big money for these amps, they use heavy transformers and they don't want to have them lean heavily on one side when carrying them to a gig.

For the home brewer though, this can be a crap shoot so it's typically easier to stick with proven layouts. Heck, a lot of builders will implement flawed designs that just happen to work (standby switches, HV fuses in the wrong place, unorthodox grounding schemes, etc) because that's how the original amp was made and we know it works. Trying to improve it can backfire.

So yeah, you can try doing this. But just know it might require some experimenting and some failed prototypes that end up in the trash.

[Phil_S]

On occasion, I've built an amp that was so unbalanced for side to side weight that I added extra weight on one side to balance out the tipping factor.

[xtian]

And I take the radical approach of moving the handle to the center of gravity!

[TUBEDUDE]

The iron should be positioned for lowest hum. If the chassis is heavy on one side from iron, I position the speaker to the other side. If that doesn't do it I place the handle at the horizontal CG.
Moving around iron for balance is shortsighted.

[Phil_S]

If the chassis is heavy on one side from iron, I position the speaker to the other side.

That doesn't work particularly well for a head!

[TUBEDUDE]

Then relocating the handle is preferable to adding weight. But unless it's a Fender 400PS, carrying it unbalanced shouldn't be too bad. Gotta suffer to play the blues

[ViperDoc]

Much appreciated, guys!