film-o-sound 185 thing

[maxkracht]

Just started laying out this amp around a 185 faceplate. It's going to be roughly 5e3ish, with a 5879 v1, 6SL7 v2 and ss rectifier. I went against my layout instincts and kept the input closer to the center so I didn't need to push the faceplate all the way to one side, then smooshed the tubes closer to the input. This left me with a less than ideal OT placement, trying to stay far enough away from the preamp tubes but not too far away from the output tubes. The OT wires are coming into the chassis a bit closer to a terminal strip than I intended. Curious if anyone has opinions on whether it is better to run the primary or secondary wires closer to the preamp stuff. The 3 lugs it will be closest to are going to be preamp supply. If I were to do this over, would it be better to move the OT all the way over to the preamp side, or to crowd the tubes a bit? Thanks!

[maxkracht]

Am I right to assume OT secondary wires closer to the input have potential for coupling audio, but OT primary wires potentially couple 120hz hum and audio? Should I be more concerned about high voltage or high current audio signals? Should I be more concerned about magnetic coupling from the transformer and place V1 closer to the null point?



Guessing none of this is critical in this instance, but I’m curious how best to break rules when breaking rules. I'm usually working off of an existing amp's tube/transformer placement when laying out a point to point thing.

[maxkracht]

Needs some fine tuning, but it sounds good so far. I was expecting something over 400v from this 320vct Princeton transformer from Mojotone, but it ended up around 370. Not mad about it, but had to ditch the sag resistor.

IMG_1847 2.jpg

Edit: see if you can spot the dumb mistake at v1

[maxkracht]

Think i'm about done. I was asked to err on the side of louder and cleaner, which isn't usually my goal with this kinda amp, but I think it turned out pretty well. Turning on the front switch turns off global and local NFB so you can still get more raw 5e3 sounds. Second stage is unbypassed to keep things tame. I'm using some reflective 3m tape for the jewel. Happy to hear suggestions.

[xtian]

Nice looking build!

[maxkracht]

Thanks xtian! I'm sure this exact thing has been done a million times, but here's a schematic and voltages if anyone is interested.