Noisy Cricket lo-fi mini combo

[jugglindan]

Spent a while tonight playing around with Inkscape, slowly getting more productive with it as I learn more features. Made a 1:1 scale mock of the control panel that is going to go on the top of the speaker enclosure (for the wood texture I just took a photo of the speaker and loaded it into Inkscape):


Once I have the layout looking good, I create a drilling template in another layer. This template gives me the location and size of the hole to cut in the speaker enclosure, the size of the MDF sheet that I am using to make the control panel (no metal sheets on hand), and the drilling template for the MDF:


This is the same method I have been using for pedal templates lately. Mock layout leading to the drilling template and the decals.

[Simon Barden]

Two gains? Confusing without more explanation. If you can, I'd move the power switch to the other end so that the gains canthen line up with each of the jack inputs (if that's how it works).

[jugglindan]

Yeah, I can move everything around.

I could also leave power where it is and move the guitar input to the other end.

The 2 gains come from the two circuits I am building in. The Noisy cricket is the group of 5 controls on the right + the guitar input. The piezo preamp circuit is the preamp input and preamp gain. When the preamp jack is connected it runs the preamp into the main amp.

I can also rename the preamp level to something else, like "level". Maybe also draw boxes around the two control groups to make things a bit more clear.

[Simon Barden]

I'd certainty label the piezo input with a Piezo tag. And boxes around things always helps IMO.

[jugglindan]

Revised
Since it's MDF, I have mocked up 3 colour options based on paints I have around. I can't print white decals so can't go too dark. Leaning towards the brown myself.

[JohnH]

Yeah, I'd vote for brown too. New layout looks good

[Simon Barden]

Whilst the piezo control may strictly be preamp gain, as it feed straight into the power amp then in reality it is affecting the channel volume. So maybe change that control to just say 'Volume'? It's what you'd get on a non-master volume amp. And it stops anyone thinking that the 'volume' knob on the other channel affects the piezo channel volume.

[Simon Barden]

I like the yellow myself. Too many acoustic amps have awful brown fascias.

[jugglindan]

I like the yellow myself. Too many acoustic amps have awful brown fascias.

It's funny. Since posting I was thinking gold actually, which is sort of in between the yellow and brown. And since I am out of waterslide decal sheets, I am thinking of doing the control panel with decoupage followed by satin poly.

And yes, I have found it a bit frustrating getting the names for the controls right. As you identify, the preamp has a volume or level control. Gain is the wrong term, since the op amp is set with a fixed gain of 3.2. This is well within the range of the TL071 so there should be no clipping at all. The pot is a standard output volume control.

For the noisy cricket circuit, the gain pot is true gain, controlling the amount of op amp gain while the volume is again a standard volume on the output.

Now I am wondering if I need the preamp volume at all. Since it is feeding direct into the power amp, I should have enough control over the levels through adjusting the power amp gain and volume. If the piezo input is a bit high, reducing the power amp gain should compensate just fine. Unless it is too high with the power amp gain all the way down, in which case the output is high enough that it could simply plug straight into the guitar input.

I will experiment with this. If I do end up omitting the preamp volume I will need yet more shuffling of the control panel.

Part of me is thinking that I am completely overthinking a $20 DIY amp, but the other part of me is thinking that the detailed planning, design, and tinkering is the best part of this hobby. No prizes for guessing which part is winning!

[Simon Barden]

You want/need to get it right! So that when you put it all together you can rest at night and not worry about what you should have done differently.