5W Single Ended Dual Lite? Tweed/Vox

[BrainDeadAmps]

I purchased a lot of those 5 watt Akai m8 amps at an estate sale last year and am finally getting around to rebuilding them into guitar amps. For those unfamiliar they come with shock-mounted ef86 and 12AX7 pre-amp sockets and a el84 power tube. I have never built an amp with dual pre-amps and I am looking for some suggestions on the best way to implement it into this conversion project. I have a basic mock-up attached with tweed tone controls modified for less interaction on both channels with two 220k resisitors feeding the driver stage.

For a clean look I would like to use dual ganged pots for both the vol and tone pots,I noticed in sluckey's dual lite he used 500k pots instead of 1M, perhaps I would benefit from lowering my values to 500k also? like the 18watt trem channel.

[kagliostro]

When you finished your dual channel, as you say you have more than one to convert, if I can suggest (from our friend Dwinstonwood)

https://el34world.com/Forum/index.php?action=dlattach;topic=27512.0;attach=107694

Franco

[sluckey]

1M volume pots should work just fine.

[BrainDeadAmps]

Thanks guys, I like the idea of a simple treble cut on the ef86 side. Will report back when I get it Built.

[kagliostro]

Usually pentodes don't like to feed Tone Controls because they are a high load for them

Very difficult to see an amp with a tone control different from a rotary switch swapping different caps that follows a pentode (see Sluckey dual lite)

One of the few examples of amp that has a tone control following a pentode is the Dr Z Route 66

Franco

[sluckey]

Whoever drew that Dr Z schematic really botched the bias supply!

[kagliostro]

Seems that a cap is missing

Franco

[sluckey]

Yes. A cap and a resistor, and the filter caps are backwards. The Route 66 schematics I've seen did not use a bridge rectifier.

[BrainDeadAmps]

Usually pentodes don't like to feed Tone Controls because they are a high load for them


Franco

Still playing with ideas, what Franco said kept coming back to mind because I've read that same notion in countless old threads i've gone through regarding the use of pentodes. I'd like to avoid the monstrous 6 position rotary switch and sub a 2-way mini switch instead to select different coupling caps. I haven't stumbled upon any examples of a simplified version. I have two mock up examples, what would be the best way to implement this?

[kagliostro]

Ciao BrainDeadAmps

Looking to your initial attempt to a Tone Control for the EF86 I remembered that it can work correctly with only a bit of adjustment



The Rotary Cap Selector can be swap with a pair of capacitors and a pot

Mr. Merlin suggested this thing