Elektra Cranker

Stompboxes circuits published in magazines, books or on DIY electronics websites.

Re: Elektra Cranker

Postby snk » 06 Dec 2018, 10:46

Hi, Manfred,
Thank you. Indeed, your circuit is much simpler :)
I did it this way, because i soldered the diodes and leds directly on the switch (not on the veroboard).
But your circuit seems simpler, and should make the layout better. I need to consider it and figure out how to make it a veroboard.
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Re: Elektra Cranker

Postby snk » 06 Dec 2018, 14:19

Manfred wrote:Hi snk, the double switching of the caps and the diode circuties is not absolutely necessary.

The good thing being that it gets rid of the need of using a 4PDT.
It's very easy for the CAP switch (few components involved), a tad bit messier for the CLIP switch (from the drawings i made, it involved either a much bigger veroboard if the diodes and leds are fitted on the veroboard, or having 12 leds & diodes soldered between the wires and the switch, right ?).


By the way, I am wondering if all the links and the routing to ground i did on the "dual circuit" veroboard is right ? I think the "core" of the circuit is fine, but i am unsure about the way i duplicated it on the veroboard :hmmm:


Last interrogation : could i get rid of the wire on A10 ("EQ lug A2 to ground"), if i solder both 1nF resistors from the second lugs of the dual pot together, (and therefore use only one single wire to ground) ?
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Re: Elektra Cranker

Postby snk » 08 Dec 2018, 12:48

Hello,
This is an updated version of the layout :
- It now uses 2PDT (instead of 4PDT), as Manfred suggested;
- It features every knobs (the circuit uses dual gang knob, but each layer is represented by a single knob).
- I changed the veroboard size a bit (i made some improvements on J & K rows, which i combined : this way, the layout is 1 row more compact, and needs 1 link less). I hope i did not make any mistake :hmmm:
- I changed the wiring a bit, in order to make the circuit a bit less "spaghetti" (the grounds of the dual gang pot are linked together, so there are less wires going from the veroboard to the knobs).

Stavro Crank v4.jpg
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Manfred (08 Dec 2018, 12:54)
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Re: Elektra Cranker

Postby Manfred » 12 Dec 2018, 23:29

I made a strip layout where the most components are on the board.
The size is 1.9 x 1.9 Inches.
I have not yet built this board, but I checked it using the trace function of the Lochmaster software.
Please recheck it.
DoubleCrankerVeroConnections.JPG

DoubleCrankerVero.jpg

DoubleCrankerVeroSolderSide.jpg

PDF files for printing the original size:
DoubleCrankerVeroParts.pdf

DoubleCrankerVeroSolderSide.pdf

Lochmaster file:
speakercrankerdouble.zip
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snk (13 Dec 2018, 00:11)
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Re: Elektra Cranker

Postby snk » 13 Dec 2018, 08:16

Wow, thank you, Manfred !
I will give it a look :D
This is what i feared : adding diodes and capacitors to the PCB make it much bigger (twice as big at least), and increase a lot the amount of traces and cuts (making me more prone to making errors, ah ah :oops: ).
I will use your layout to compare it against mine, and i might try either yours or mine this week-end if free time allows :)
Again, thank you for yor precious help.
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Re: Elektra Cranker

Postby Manfred » 13 Dec 2018, 09:03

I will give it a look :D

Thank you snk!
This is what i feared : adding diodes and capacitors to the PCB make it much bigger (twice as big at least), and increase a lot the amount of traces and cuts (making me more prone to making errors, ah ah :oops: ).

Your are right, that was clear to me.
I will use your layout to compare it against mine, and i might try either yours or mine this week-end if free time allows :)
Again, thank you for yor precious help.

Don't worry about your layout is ok to me.
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Re: Elektra Cranker

Postby snk » 14 Dec 2018, 13:02

Hello,
I have made a new prototype, using two mono prototypes i had made previously (so i am not using the last layout yet : each channel is on its own veroboard, as well as the decoupling board) : It works, I like the sound.

My only concern is that there is a quite unexpected behaviour with the tone (low pass) knob : When i turn it, there is a big volume loss (well, that was expected, as i know passive tone stacks implies a volume loss), but i also noticed that while i was increasing the action of the filter, the sound seemed slightly more distorted (while less loud). I watched at the guts of the circuit, and noticed that indeed, turning the filter knob clockwise was making the leds brighter (which means that the diode clipping is more important). I also noticed that the hicut action was not very audible.
I didn't expect that, as the filter knob is not supposed to change the distorsion action, right ? Also, the eq is after the distorsion, so i didn't expect them to be that much interactive :scratch:
Its like the TONE knob is acting like a GAIN knob :hmmm:

Is it something i overlooked, to be expected ?
Or an error on my side ?
I will investigate, and check my wirings, but i wanted to ask here if the post-clipping filter knob is actually supposed to make change in the distorsion ?
Also, is there any easy way to somewhat compensate for the volume loss of the filter (i guess the answer will be : use an active circuit like an EHX LPB :lol:, but i'm still asking)
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Re: Elektra Cranker

Postby plush » 14 Dec 2018, 13:37

snk wrote:I didn't expect that, as the filter knob is not supposed to change the distorsion action, right ? Also, the eq is after the distorsion, so i didn't expect them to be that much interactive :scratch:
Its like the TONE knob is acting like a GAIN knob :hmmm:

Is it something i overlooked, to be expected ?
Or an error on my side ?
I will investigate, and check my wirings, but i wanted to ask here if the post-clipping filter knob is actually supposed to make change in the distorsion ?
Also, is there any easy way to somewhat compensate for the volume loss of the filter (i guess the answer will be : use an active circuit like an EHX LPB :lol:, but i'm still asking)


>if the post-clipping filter knob is actually supposed to make change in the distorsion

It's normal for your implementation to affect the distortion.
To mitigate that install output gain stage between tone control and clippers, adjust it's gain to compensate tone volume loss.

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snk (14 Dec 2018, 13:56)
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Re: Elektra Cranker

Postby snk » 14 Dec 2018, 13:56

Thank you for your answer, Plush.
Would you have any output gain stage layout, suitable for this purpose to point me at ?

I guess that replacing the pot with a fixed value resistor wouldn't change anything, right ?
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Re: Elektra Cranker

Postby Manfred » 15 Dec 2018, 01:02

Hi snk,

the original transistorof the Cranker is a normal transistor,
but the MPSA13 is a Darlington transistor with more than 10 times current gain.

Maybe it makes a difference in the behaviour of the stage.

Can you measure the DC-voltages on the transistor leads?
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Re: Elektra Cranker

Postby Manfred » 16 Dec 2018, 00:21

the original transistor of the Cranker is a normal transistor,
but the MPSA13 is a Darlington transistor with more than 10 times current gain.
Maybe it makes a difference in the behaviour of the stage.


In the meantime I ran a simulation of the circuit using both type of transistor and found no major difference.
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