AC-15 Lite “Bass Cut” Control?

[Jacob]

Attached is the layout for my single channel AC-15 build, inspired by Sluckey, based on Mojo's NC3015 kit, and built in a Stout Chassis.

Also attached is the Mojo Schematic, I built the "Normal" channel only

I would like to add a "Bass Cut" control to tighten things up when overdriving the amp.

Would it be possible to "Piggyback" this Bass Cut pot right off of the Volume pot, the way the Tone pot is in a 5f2a Tweed Princeton?

I understand the concept of a High/Low Pass Filters, and I've found setups like this for use in guitars, but I'm still not exactly sure how I would wire this into an Amp.
(what would be run to/from which lugs) there seems to be many variations, even with simple tone circuits.

Any advice on how I would wire this up would be greatly appreciated.

I'm also open to any other suggestions, the "piggyback" just seemed simple, if it would work.

Thanks!
Jake

[d95err]

Can you draw a schematic of the circuit please? It’s difficult to analyze circuits from just a layout.

[Jacob]

Can you draw a schematic of the circuit please? It’s difficult to analyze circuits from just a layout.

I tried attaching to the original but I think it was the wrong file type, let me try here...

[Willabe]

Change the cathode (K) bypass caps, 25uF, 50uf with a 3 position switch to a lower value. Try going from 25uF to 10uF to 4.7uF. You can go even smaller if you need to, 2.2uF, 1uF, etc.

The smaller the cap value, the more bass you will leave out.

[Jacob]

Change the cathode (K) bypass caps, 25uF, 50uf with a 3 position switch to a lower value. Try going from 25uF to 10uF to 4.7uF. You can go even smaller if you need to, 2.2uF, 1uF, etc.

The smaller the cap value, the more bass you will leave out.

I believe I've heard of this sort of thing before!

I guess this approach would in theory not alter the rest of the tone, the way adding another Pot to the circuit could?

[sluckey]

Willabe's suggestion may be all you need. But if you want an effective tone control look at the Fender Harvard. Easy to install or remove.

     https://el34world.com/charts/Schematics/files/Fender/Fender_harvard_5f10_schem_2_.pdf

[Jacob]

Willabe's suggestion may be all you need. But if you want an effective tone control look at the Fender Harvard. Easy to install or remove.

     https://el34world.com/charts/Schematics/files/Fender/Fender_harvard_5f10_schem_2_.pdf

Thanks Sluckey! Does the Harvard tone control affect the Bass rather than Treble like the Tweed Princeton’s?

I have have the Treble covered with the Top Cut control, now just looking for a way to control the Bass end.

Do you guys know of any good drawings/resources for the switchable cathode bypass cap setup?

[sluckey]

Harvard 5F10 and Princeton 5F2A tone controls are identical. Plenty of schematics for cathode cap switches all over the net. Plenty right here too. Look at some of Tubenit's drawings.

[dwinstonwood]

And then, there's always sluckey's 6-way tone switch. Here's the one I'm using in my AC15. It's very effective at reducing bass frequencies. I like it better than a tone pot.

[Jacob]

And then, there's always sluckey's 6-way tone switch. Here's the one I'm using in my AC15. It's very effective at reducing bass frequencies. I like it better than a tone pot.

That looks awesome! Are you using this as the ONLY tone control on your AC15?

Could I use a switch configuration like that for 6 different bypass caps/ to choose the amount of Bass, and keep my Top Cut control for trimming Treble?

[sluckey]

You don't need 6 choices on the cathode. 3 choices is sufficient. Use a DPDT center off switch.

But that 6 position rotary will have way more effect than the cathode cap switch. The rotary simply puts another cap in series with the coupling cap between plate and volume control. The smaller the cap, the more the bass is cut.

[Jacob]

You don't need 6 choices on the cathode. 3 choices is sufficient. Use a DPDT center off switch.

But that 6 position rotary will have way more effect than the cathode cap switch. The rotary simply puts another cap in series with the coupling cap between plate and volume control. The smaller the cap, the more the bass is cut.

Gotcha! Would you suggest I try the 6-way tone switch rather than the cathode cap switch then?

If this 6-way switch mainly affects Bass, I’ll still want to keep/use the Top Cut control as normal right?

Do you have a recommended make/model for the 6-way switch?

[dwinstonwood]

Yes, that is my only tone control. Position #1 basically bypasses the switch; the signal passes through the coupling cap in series before the switch, and straight to the volume pot. So, the value of position #1 is whatever the value of your coupling cap is. I'm using an .01uF, but it can be any value that works.
I can't comment on using this switch for cathode bypass capacitors, no experience with that. Here's the switch I'm using:
https://www.tubesandmore.com/products/switch-rotary-2-poles-6-positions-shaft
You'll want the Shorting/Make-Before-Break version.