5F1 Pre-build Questions

[HBCYG5260]

Planning to build a 5F1 combo but had a few questions before pulling the trigger on everything.

First, the amp would likely be too loud for me to crank in my apartment so I'm looking at possible solutions for that. I already have an attenuator box that I built, but I'd prefer to not have to depend on it if I want to just grab and go with the amp. Would Rob Robinette's 10% power mod be a good solution here? The other issue with my attenuator box is that it's 8ohm, which leads me to my next question.

The speaker I'd like to use with the build is 8ohm and the Mojotone kit I was going to go with has a 4ohm OT. So what would be the best solution here? Would it be better to get a small parts kit and source the tubes and transformers separately? I read that for a 5F1 using an 8ohm OT doesn't require much adjustment to the circuit, except with a possible adjustment to the 22k NFB resistor. Is this accurate? Thanks in advance for any input

[sluckey]

The 5F1 has a volume control. Just turn it down.

[HBCYG5260]

The 5F1 has a volume control. Just turn it down.

I understand that. But isn't the volume on the 5F1 "tied" to the gain? Wouldn't keeping the volume low keep the tone on the cleaner side of things?

[tdvt]

^^^^ Start there, those are pretty small amps.

If you find have to have use an attenuator, easy enough to add a simple L-pad on the back side of the cabinet. Built-in, ready to roll.

Mojo has multi-tap Champ OTs, maybe they would substitute..? 


Optionally, I have used a few of these;   https://www.tubesandmore.com/products/transformer-output-5w-5k-8k-primary-options-upgrade-fender-champ   

Inexpensive, works well

[HBCYG5260]

^^^^ Start there, those are pretty small amps.

If you find have to have use an attenuator, easy enough to add a simple L-pad on the back side of the cabinet. Built-in, ready to roll.

Mojo has multi-tap Champ OTs, maybe they would substitute..? 


Optionally, I have used a few of these;   https://www.tubesandmore.com/products/transformer-output-5w-5k-8k-primary-options-upgrade-fender-champ   

Inexpensive, works well

Thanks, that OT does seem like a good option. I emailed Mojotone about substituting the OT in the kit, so if they can't then I'll just buy the cheaper one

[passaloutre]

You could go with something like Robinette’s “Micro Champ”, which uses a paralleled 12AU7 for the power tube.

[HBCYG5260]

You could go with something like Robinette’s “Micro Champ”, which uses a paralleled 12AU7 for the power tube.

I had considered one of his micro builds, but have read posts/threads online from other builders who've said those micro builds often end up being more difficult than most people anticipate. This is only my second build so I wanted to stick with something more in "kit form"

[johnnyreece]

If for some reason you *do* decide to go the "Micro Champ" route, you could use a 6SN7 instead of a 12AU7.  That way, you can use the original octal socket instead of adapting it to a 9-pin.