EHX Electric Mistress Clone - Need Help!

[Ian2217]

Hi there everyone

I really want to try to build a clone of EHX's Electric Mistress Flanger.
I have the schematic for it but I have one problem. I don't know how to read it!
I attached it to this thread.
It's confusing to me because the empty boxes seem to represent several different components (resistors? potentiometers?)
Basically I'm trying to compile a parts list so I can order all the stuff online to build this pedal.
If any of you could help identify some of the more cryptic symbols or help me put together a parts list I'd really appreciate it.
Thanks

 

[Harald Kapp]

Welcome Ian.

As you guessed the boxes are resistors, the number indicating the value:
xxx = xxx Ohm
xxxk = xxx kOhm
xxxM = xxxMOhm

If you can't read the schematic, how are you going to build this correctly? Anyway, take the schematic to an electronics shop near you and ask the salesperson to bundle all the parts for you.

 

[Ian2217]

Welcome Ian.

As you guessed the boxes are resistors, the number indicating the value:
xxx = xxx Ohm
xxxk = xxx kOhm
xxxM = xxxMOhm

If you can't read the schematic, how are you going to build this correctly? Anyway, take the schematic to an electronics shop near you and ask the salesperson to bundle all the parts for you.

Thanks for the reply. I thought that's what it was but why have both the box and the jagged line notation for resistors in the same diagram? Also would you be able to tell me if the resistors with the 'lin' suffix are potentiometers?
I actually have some experience with breadboards so I could prototype it I think. I've done simple solder jobs before too so I think I'll be able to put it together once I've got all the parts I need and have the diagram understood correctly.

 

[Harald Kapp]

The "jagged lines" are trim-potentiometers. The jagged lines symbolize the way potentiometers used to be made: wind a wire around a toroidal core and swipe a wiper across the resulting coil to change resistance. A trim-potentioometer is put on the pCB and adjusted once during calibration - it is normally not accessible and not adjustable during operation.
A normal potentiomete, as indicated by the box symbol is menat to be adjusted during use. It is monted such that the axle reaches through the panel of the device and a knob is attached to the axle.

It is not very customary to use different symbols for potentiometers and trim-potentiometers. The author may hjave chosen to do so to better distinguish between the two.
"lin" indicates a potentiometer with a linear relationship between agle of turn and resistance.
This is opposed to "log" potentiometes where the resistance changes logarithimically with angle of turn. Log potentiometers are typically used for the volume adjustment in audio applications since the human ear responds in a roughly logarithmic way to the amplitude of sound. With a "log" potentiometer an increase in angel of turn corresponds to an equivalent increase in volume as felt by the human listener.
Note that this is for explanation only. There are no "log" potentimeters in the circuit.

I actually have some experience with breadboards so I could prototype it I think

I do not want to disencourage you, but before you start building the device, read up on issues such as:
- shielding
- ground planes and "star ground"
- ground loops
- decoupling capacitors
to ensure a stable circuit. Otherwise you run the risk of having audible hum in your signal, noise, even AM radio reception.

The very least I can recommend:
- use a fully closed metal housing
- connect ground to the housing at 1 single point
- If you can't have a ground plane, make a "star ground" at the ground pin of the 7812 regulator. feed all grounds separately to this central ground to avoid ground loops.

Here is an article on how to build prototype breadboard PCBs for analog circuits.