my first diy 5f1 champ head

[Ruub]

Hi I’m Ruben from the Netherlands and I just finished my first diy tube amp today 

What do you guys think?

I’ve added a pwr plug socket and rotary ohm selector so I can use my 2x12 celestion blue cabinet at 16ohm.
With hindsight I could have changed the layout of the turretboard so wires could be shorter, but I wanted to be able to reuse all the parts in the regular champ chassis in case my own layout would be a disaster.

There is some hum, but not very disturbing and quickly overpowered as soon as you start playing guitar.

I will install a plexiglass bottom plate with rubber feet next week as soon as it arrives.

Greets, Ruben

[davidwpack]

Very nice!

[labb]

I would think that if you would add an artificial center tap ground for the heater wiring the hum would go away...Nice job.

[PRR]

Welcome Ruben!

Very nice job.

Labb-- he's got a 3rd green-ish wire, probably the 6V CT, going toward what may be main ground. That's usually as good as a 2-resistor "CT".

[Willabe]

Labb-- he's got a 3rd green-ish wire, probably the 6V CT, going toward what may be main ground. That's usually as good as a 2-resistor "CT".

Yes, you can just see the white stripe on that 3rd green wire where it comes out of the PT.

Nice work Ruben.   

Only 1 thing, you have the 9 pin preamp where the 8 pin power tube should be. But if it's working, great.   

[labb]

Good. I didn't see the ground.

[Ruub]

The main ground is just out of view at the top of the turretboard where the black ground wire is going. There is a green with white striped wire connected there too.

I swapped the place of the 6v6 with the preamp tube for cosmetic reasons and it would give more distance from the PT and OT.

[Willabe]

I swapped the place of the 6v6 with the preamp tube for cosmetic reasons and it would give more distance from the PT and OT.

The weakest signal in the amp is at the 1st preamp tube, it's the most vulnerable to stray signals and stray magnetic fields being injected into the tubes grids. Most amps keep that 1st preamp tube as far away as possible from the PT, acv wiring and power tubes because of this.

And because you flip/flopped the preamp tube with the power tube, you had to lengthen the 1st and 2nd stage grid wires, which acts like an antenna, the longer it is the more it can/will pick up. You can use shielded wire there to protect it from doing this. And the power tube is right next to the input jacks, shielded wire can't fix that.

After the ac signal goes through a coupling cap, it is now a grid wire. Rule of thumb is, plate wires long, grid wires short. Your grid wire runs are pretty long.

Your OT is fully shielded and you have a lay down PT. So the PT and OT cores are at 90 degrees from each other. You could have put the OT in the middle of the chassis, next to the PT. It should have been fine there. Then you could have had the preamp tube at the far end of the chassis.   

The preamp tube is very close to the ac power switch, that can introduce 50/60 htz buzz into the preamp's grids.

And you left the turret board components the same, so the preamp circuit components are next to the power tube and the power tube circuit components are next to the preamp tube. Because of this you had to use longer wire runs for everything and go back and forth across the chassis with all the wires.

All these things are opposite of standard lay out and lead dress practices to keep an amp quite and keep it from having oscillation problems.     

You got lucky.