Scratch Build Design Layout Question w/Poll

[scupbucket]

Hey Folks! I'm building an amp for my bro-in-law for Xmas. Nothing fancy... essentially a Maggie 175 clone with the proper tweaks for standalone use. I'd like to package everything within an 8x12 chassis for a compact "bookshelf" look so I need to keep the layout ultra tight while allowing for clearances and some breathing room for the tubes. Any suggestions for proper placement of the outputs using the pic for reference? I personally like the 45* diagonal look (I've used that layout on previous builds with success - similar to the Fisher 480a) but I figure I'd toss a poll up on here too... they're fun. There might be a better solution that's not shown so please feel free to add your .02. Thanks!

 

[gadget73]

power supply as far away from the audio stuff as possible and the transformer cores at 90 degrees to one another is generally the way to make it as quiet as possible.

 

[THD+N]

What gadget73 said. Aesthetics and performance are sometimes a compromise. However, in some cases, you can have both.

 

[trainbuftony]

I like #2 because it keeps the original layout of the Maggie (I may be thinking of a different magnavox)
#3 Is more symmetrical and if it were me I'd probably go that route.
Dont stress too much about magnetic noise.
Ive only ever had it be an issue one time and that was with moving coil transformers in a sensitive preamp with gobs of gain after them... Turning them 90° shut them up.
Make sure your cores run at 90° from one another and you won't have any issues with regard to magnetic coupling.

 

[kward]

#2 will produce consistently quieter results. Don’t get sucked in with aesthetics. No one wants to listen to a pretty amp if it’s noisy.

But you also have to do the grounding properly. Any of those choices could be noisy if grounding is not thought out.

 

[Mdpaudio]

Do the 45 trick but in opposite directions creating a V shape rather than parallel. That way the fields don’t interact as they are 90 degrees to each other.

 

[Lavane]

All but one I've built was like number 2. It does make more sense having the power transformer and power supply on one side, and the amplifier circuit on the other side. I did build the one SE amp like number 3 and it turned out fine though.

 

[Mdpaudio]

I do all mine like number 3 but they are dual mono with separate windings on the PT for each channel. The only common parts are chassis and PT with two power supplies, etc.. layouts are mirror image.

 

[WntrMute2]

I'd encourage you to fool around with placement by listening to the OPT while energizing the PT. I use a pair of wired earbuds into a 3.5mm jack with alligator clips soldered onto the jack's leads. I could easily listen to the induced hum from the 120VAC fed into the PT. Just don't forget to insulate the HV leads of the secondary. I've found nulls in odd placements like under the power transformers for chokes and similar.

 

[Lavane]

I'd encourage you to fool around with placement by listening to the OPT while energizing the PT. I use a pair of wired earbuds into a 3.5mm jack with alligator clips soldered onto the jack's leads. I could easily listen to the induced hum from the 120VAC fed into the PT. Just don't forget to insulate the HV leads of the secondary. I've found nulls in odd placements like under the power transformers for chokes and similar.

I moved the choke around under the chassis in the little SE amp I posted a picture of. I found a spot on the back of the chassis close to the power trany that got rid of the slight hum I had. Some of the chokes I've used are physically huge and it was harder to find the perfect position.

 

[THD+N]

I moved the choke around under the chassis in the little SE amp I posted a picture of. I found a spot on the back of the chassis close to the power trany that got rid of the slight hum I had. Some of the chokes I've used are physically huge and it was harder to find the perfect position.

I use to use "big" chokes until I started using Duncan's Power Supply software... It is so easy to use and optimize a topology. Caps are cheap(er) nowadays and chokes are inching up to quite a bit of money, so I go easy on the inductance and big on the caps or just eliminate the chokes altogether depending on the amp design/project.

 

[TriodeLuvr]

I prefer a narrower design, it lets me put more gear on the shelf.

My last amp:



Jack

 

[scupbucket]

Dang... I don't post here often but when I do, you guys are quick to offer some solid advice... I greatly appreciate it!

This is some great info here and thanks for sharing some build pics... I fell down a rabbit hole of looking at other designs and layouts (Jack, I'm loving the narrow build! Is that a steel chassis?) and keep second guessing how I want to approach this.

Don’t get sucked in with aesthetics. No one wants to listen to a pretty amp if it’s noisy.

Thank you... I needed to hear this. I get too obsessed when it comes to how the final product looks.

I'd encourage you to fool around with placement by listening to the OPT while energizing the PT. I use a pair of wired earbuds into a 3.5mm jack with alligator clips soldered onto the jack's leads. I could easily listen to the induced hum from the 120VAC fed into the PT. Just don't forget to insulate the HV leads of the secondary. I've found nulls in odd placements like under the power transformers for chokes and similar.

I'm going to try this ASAP... I wish I knew this before my last build lol (had to punch a few extra holes in the chassis to rearrange the choke and one of the OPTs).

 

[TriodeLuvr]

Jack, I'm loving the narrow build! Is that a steel chassis?

I only build on aluminum. The chassis in the picture started as a 2" X 10" extrusion several feet long. The walls are 0.125". I do all my own metal work and finishing, but I think Landfall Systems can create whatever you need.

https://www.landfallsystems.com/index.php

Jack