Archive for May, 2012

If I made a mini version of the Solar Lifeforce without the CV mode and buffer on a toggle (the circuit would be buffered but the pedal true bypass) is that something you guys would want? When I say mini I mean really tiny – Hammond 1590A tiny like the Morse Device, Bomb Idea and 072 buffer. I think the description ‘volume and treble killer’ is more accurate than LDR volume pedal, but it can also act as a sort of foot operated tremolo. Price point would be around £40, and it would have a sticker decal (see below), not sprayed.

Here’s a link to the big old version in action, functionality, other than perviously mentioned, would be the same.

So, please vote so I can get an idea of how popular this idea would be if I were to make a small batch!

*Update 18/06/2012 – As the results of the above poll show there is no great interest in this pedal, so it is looking unlikely I’ll be putting it together as a batch.

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Here’s a couple of pics of the new style Morse Device. I have 2 of these ready to be shipped out, looking for £25 delivered in the UK, outside the UK please email me.

So, here is a simplified schematic for the Solar Lifeforce. Basically I have removed the expression/CV out stuff, removed the toggle for the buffer so the buffer is always on, and made it as simple as possible. It could maybe do with some small value caps between both R5 and ground and R9 and ground, but they aren’t essential. The LDR is a pretty unreliable thing for any consistent readings so maybe buy a bunch and try them out until you find one that suits you, I have tried the circuit with ones of varying specs and they all have behaved OK. The best I found was on doctor tweeks website which can be found here. It has a dark resistance of 20M which is plenty, 10 lux (‘room’ light) resistance is between 50k-100k and it has a rise time of 20ms and a decay time of 30ms.

Before I go into the circuit I will warn you – LDR’s aren’t perfect for cutting volume alone as they roll off treble, so your tone will be altered. This isn’t a problem so much when you are playing in really well-lit conditions but it does become noticeable when you are in stage type conditions. Of course this may be what you want, but if you are after a ‘transparent’ volume cut a LDR is not the way to go.

Anyway, here’s the circuit. I havent included the LED/switch wiring etc in this one, and I haven’t put in reverse polarity protection. It is up to you if you think it is needed. If you think it is you could just use a diode such as a 1N4001 in series with the 9v rail.

R1 is a pull down resistor to help prevent popping when the circuit is bypassed/engaged. R2, R3 and C1 form the network which establishes the reference voltage for the op-amp. The first side of the op-amp acts as a buffer, and the second side acts as a gain allowing you to increase the volume to compensate for poor lighting conditions. VR1 controls the range of the LDR between being covered and uncovered and R5 sets the minimum for this. R9 and R10 set the gain of the b side of the op-amp, which is around 5  (G = 1 + (R10/R9) = 5.545), which is then attenuated by VR2 just before the output. C4 stops any DC leaking from the circuit into your amp. You could use a lot of different op-amps for this circuit. I used a TL072 because I like them, have a few kicking around and is a dual op-amp so takes up less room than two signals. They are also pretty cheap and quiet so are good for this kind of work. On the Barefoot which was really the predecessor to the Solar Lifeforce I used DPDT toggle switch to change between if the signal kills when the LDR is covered or is restored there, you could probably mod this circuit to include it. You could also use a DPDT toggle to cut the buffer out of the circuit if you wanted too easily enough. I wired the original so the buffer was independent of the pedals bypass, so the signal hit the buffer, then the bypass, then the rest of the circuit, but you could wire it after the bypass so that you have a switchable buffer aswell. Just to clarify on this diagram the buffer is always in the circuit.

Here’s the part list:

R1         1M
R2         10k
R3         10k
R4         1M
R5         10k
R6         LDR
R7         10k
R8         1M
R9         2.2k
R10        10k

C1         10uF
C2         100nF
C3         10uF
C4         10uF
J1         Input
J2         Output
U1         TL072
VR1        500k Lin
VR2        10k Log

I found the best way of mounting those odd shaped LDR’s that are specified as 5mm diameter but aren’t actually round is to use a 5mm bezel mount. And be sure no light can get to it from inside the enclosure from the LED!

Update 12/07/12:

The circuit above is a little crude in places, it is a barebones version of the hand drawn circuit I drew when experimenting with it. Perhaps a nicer version would be to have a gain control directly controlling the gain of the b side of the op amp (ala the MXR Distortion+) and a separate volume control as the gain pot is wired in this circuit in this circuit. That way you are not boosting the signal only to attenuate it.  The volume control is then completely optional as in many ways the gain will act as a kind of volume control anyway. Here is my revised circuit with the aforementioned mod, a few additional caps and a resistor to help cut out the really high frequencies before the buffer. Probably still a fair bit of room for improvement, but here we go! I haven’t built this version yet, but it should be OK.

Update 11/12/12:

I’ve modded this circuit again (haven’t tested it but thought I would post anyway, so beware!) to have some basic filtering on the power supply, set the output impedance at 1k and also adjusted the values of a few components to make them a bit more sensible. If you build this and can verify it works well please let me know!

Solar Lifeforce Revised Schematic

 

Stickers!

Posted: May 29, 2012 in FX, Morse Device
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The first batch of Morse Device stickers arrived yesterday!

Here’s a dead simple one, the circuit for the Morse Device. This uses just 4 components: an input jack, and output jack, a momentary DPDT footswitch and a latching DPDT footswitch. The latching footswitch could be a SPDT but as I have a fair few DPDT around I tend to use that.

What is going on here is pretty easy to explain. Basically the two footswitches control if the signal is connected to ground or not. If it is the signal is muted, else it reaches the output jack unaffected. The latching switch determines which throw on the momentary switch the signal connects to, which in effect reverses the NO/NC action of the momentary switch.

I have 2 Morse Device killswitches in the pipeline ready end of the week, bare aluminium enclosure with ‘army man’ sticker decals.

These are available delivered within the UK for £25 each.

Email me at ben@0xdfx.com to order one.

072 Buffer Circuit

Posted: May 10, 2012 in 072, Build Your Own, FX
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So, here’s the circuit I used to create the 072 with. It is pretty much as basic as you can get, especially as it is always on but it is very effective at its job.

D1 is for reverse polarity protection incase people use a positive center adaptor instead of negative center (or vice versa depending how you wire it). R1, R2 and C2 form the voltage divider which provides the reference voltage for the opamp. R1 and R2 don’t have to be 47k, they can be anything (I would stick between 10k and 100k though to ensure the divider is reasonably stable) as long as the values are equal. C1 helps prevent any noise while  C3 prevents and DC from the circuit leaking into the amp and R3 limits the current so the LED doesn’t burn out. You could get away with something like a 680r resistor for R3, but the I like the 2.2k because I have a load of them, and they are commonly used for this purpose! I would hook up pin 7 (the output for the second side of the opamp) of the TL072 to ground as it isn’t going to be used.

And that is really all there is too it. Fits nicely in the 1590A enclosures, providing your layout fits. On the only 072 I have built I had quite a big vero layout and it still fit, but I redesigned it after to be that bit smaller to allow slightly more room in the enclosure for everything else.

Parts:

R1    47k

R2    47k

R3    2.2k

R4    1M

C1    100nF

C2    10uF

C3    10uF

D1    1N4001

D2    3mm LED

U1    TL072

And the all important circuit:

You can pretty much drop this into other builds, and if they require an opamp you will probably have a reference voltage you can tap into to get your Vr, which cuts out the whole voltage divider section. There are many, many mods you can do to this circuit, but this is meant as a simple low noise, low part count buffer in a small package.

Revision 04/02/2013: I have updated the circuit and added a vero:

Revised Circuit Vero