1590A · 1 knob
DAM Meathead with switchable capsVerified
Based on the D*A*M Meathead· 7 other boards clone it
From the post
This was a request from one of our members. I wondered what the best method would be to do this, maybe using a 3 position 4 pole rotary switch, but I think this method by far gives you the most versatility.
With both 3 position switches in the centre off position, the Meathead stock values (10n & 22n) will be in circuit. When selections are made, the selected cap value is summed with the stock value to give a wide variety of stock up to Meathead Dark tones. You will have 10n, 22n or 43n for the input switch, and 22n, 69n or 122n for the output switch. Swap the caps to suit your own tastes if you like things a bit more or a bit less dark. It may be worth building the board and then breadboarding the cap selection part to make it ideal for you.
With the board only being 10 columns wide this is totally do-able in a 1590A. Let's see who's brave enough! :o)
After a conversation below it and doing a few calculations, it seems that the change of output cap for the Meathead Dark was irrelevant as the frequency cut by the standard 22n output cap was already lower than the lowest frequency on the guitar. With that in mind, this version may be more useful offering a post gain bass cut. In the centre position with just the 220p in circuit it will be a very lo-fi effect because much of the mids and all the bass will be cut. In the 22n position you will get a full bass output, and in the 1n position there will be some bass cut which may be useful for cleaning things up a bit.
Schematic
This is a board layout, a drawing of where each part goes, and the post may link the schematic it was drawn from. Open the layout at Tagboard Effects. No KiCad fragment has been drawn for this circuit yet.
Parts list 13 rows
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Check before you build · 5 values the reader of this layout was not sure of
- All 6 board resistors: values illegible in the thumbnail
- Both board electrolytics (top right, bottom left): values illegible
- The two small caps on the board: read as 10n and 22n only from the note 'Meathead stock values (10n & 22n)' and the 10n / 22n labels at the switch commons, not from the parts themselves
- Transistor labels 2N3904 (left) and BC182L (right) are blurred; best reading
- Pot name is not printed; it is wired to Output
| Ref | Value | Normalized | Type | Notes |
|---|---|---|---|---|
| Resistors 1 | ||||
| ×6 | ? | ? | value unreadable in thumbnail; read from the layout by eye | |
| Capacitors 7 | ||||
| ×2 | ? | ? | electrolytic; value unreadable in thumbnail; read from the layout by eye | |
| ×1 | 10n | 10n | stock input cap, per the note; read from the layout by eye | |
| ×1 | 22n | 22n | stock output cap, per the note; read from the layout by eye | |
| ×1 | 12n | 12n | on the input cap switch; read from the layout by eye | |
| ×1 | 33n | 33n | on the input cap switch; read from the layout by eye | |
| ×1 | 47n | 47n | on the output cap switch; read from the layout by eye | |
| ×1 | 100n | 100n | on the output cap switch; read from the layout by eye | |
| Transistors 2 | ||||
| ×1 | 2N3904 | 2N3904 | left transistor; read from the layout by eye | |
| ×1 | BC182L | BC182L | right transistor; read from the layout by eye | |
| Potentiometers 1 | ||||
| Volume | B500K | B500k | Potentiometer | printed '500K LIN'; knob name not printed; read from the layout by eye |
| Switches 2 | ||||
| Input caps | DPDT on/off/on | DPDT ON/OFF/ON | toggle; read from the layout by eye | |
| Output caps | DPDT on/off/on | DPDT ON/OFF/ON | toggle; read from the layout by eye | |
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