EarthQuaker Devices - Bellows  [traced]

General documentation, gut shot, schematic links, ongoing circuit tracing, deep thoughts ... all about boutique stompboxes.

EarthQuaker Devices - Bellows

Postby ThiagoFaraday » 29 Dec 2016, 06:11

Someone has already picked up one of these or has some information. I liked the fuzz mix of this pedal, but I do not find any information about this circuit online. Just a picture of him that does not say much. :hmmm:
You do not have the required permissions to view the files attached to this post.

For this message the author ThiagoFaraday has received thanks:
modman (01 Feb 2017, 21:35)
User avatar
ThiagoFaraday
 
Posts: 40
Joined: 18 Nov 2016, 12:34
Location: Brazil
Has thanked: 54 times
Have thanks: 22 times

Re: EarthQuaker Devices (EQD)- Bellows

Postby andregarcia57 » 04 Jan 2017, 02:43

great sound....

For this message the author andregarcia57 has received thanks:
ThiagoFaraday (04 Jan 2017, 04:48)
andregarcia57
Resistor Ronker
 
Posts: 442
Joined: 16 Nov 2008, 16:42
Has thanked: 0 time
Have thanks: 82 times

Re: EarthQuaker Devices (EQD)- Bellows  [traced]

Postby jrfox92 » 28 Jan 2017, 07:42

EQD Bellows.png

EQD Bellow schem.png
You do not have the required permissions to view the files attached to this post.

For this message the author jrfox92 has received thanks: 2
modman (01 Feb 2017, 21:35), ThiagoFaraday (10 Feb 2017, 02:19)
jrfox92
Breadboard Brother
 
Posts: 58
Joined: 11 Jun 2014, 05:46
Location: Akron, Ohio
Has thanked: 4 times
Have thanks: 38 times

Re: EarthQuaker Devices (EQD)- Bellows

Postby roseblood11 » 28 Jan 2017, 10:12

How does Q1 work here? Looks strange...

For this message the author roseblood11 has received thanks:
modman (01 Feb 2017, 21:39)
roseblood11
Opamp Operator
 
Posts: 1685
Joined: 23 Aug 2008, 15:21
Has thanked: 315 times
Have thanks: 298 times

Re: EarthQuaker Devices (EQD)- Bellows

Postby Silver Blues » 29 Jan 2017, 00:36

roseblood11 wrote:How does Q1 work here? Looks strange...


That's exactly what I said in the thread on Tagboard about this :lol: I'd love an explanation for this as well.
User avatar
Silver Blues
Breadboard Brother
 
Posts: 69
Joined: 23 Apr 2013, 20:25
Location: Atlantic Canada
Has thanked: 12 times
Have thanks: 21 times

Re: EarthQuaker Devices (EQD)- Bellows

Postby jrfox92 » 29 Jan 2017, 06:31

This is kind of a wild guess since I haven't really studied fets, but it looks like it might be acting like a noise gate? :scratch:
I'm basing that guess off of this article which states:
If you leave the Gate (G) of a JFET open, the Drain (D) and Source (S) will pass signal through, as the switch is connected. If you pull the Gate to a voltage less than the Source, the JFET will no longer pass audio signal.

The drain's connected to signal input while the gate is connected to the output of the BJT. So, if the signal isn't loud enough, then no sound should pass? :hmmm:
I haven't built the circuit, so I don't know how it acts, but, like I said, that's my guess.

For this message the author jrfox92 has received thanks:
modman (01 Feb 2017, 21:37)
jrfox92
Breadboard Brother
 
Posts: 58
Joined: 11 Jun 2014, 05:46
Location: Akron, Ohio
Has thanked: 4 times
Have thanks: 38 times

Re: EarthQuaker Devices (EQD)- Bellows

Postby Groovenut » 30 Jan 2017, 16:22

I believe Q1 is functioning as a clipper, swithing on/off, clipping the negative half of the wave form in response to the signal it's recieving at it's gate from the output of the Darlington collector. The fet source is biased roughly 300mV lower than the gate, which is biased by the voltage at the Darlington collector.

My 2 cents worth....

For this message the author Groovenut has received thanks:
modman (01 Feb 2017, 21:39)
User avatar
Groovenut
Resistor Ronker
 
Posts: 288
Joined: 07 Jan 2011, 17:31
Has thanked: 57 times
Have thanks: 108 times

Re: EarthQuaker Devices (EQD)- Bellows

Postby Manfred » 30 Jan 2017, 21:14

I made a simuation of this circuit.
I made a short between drain and source and nothing happens the output shows the same signal as before with different input levels.
Now I am confused of that, who could try it with the real circuit?
Manfred
Resistor Ronker
 
Posts: 422
Joined: 05 Apr 2009, 00:42
Has thanked: 724 times
Have thanks: 314 times

Re: EarthQuaker Devices (EQD)- Bellows

Postby Groovenut » 31 Jan 2017, 02:02

Manfred wrote:I made a simuation of this circuit.
I made a short between drain and source and nothing happens the output shows the same signal as before with different input levels.
Now I am confused of that, who could try it with the real circuit?

Keep in mind that you will have a very high resistance between the gate and the source (roughly 1M depending on the fet and the gate leakage), this is what biases the Darlington. IMO
User avatar
Groovenut
Resistor Ronker
 
Posts: 288
Joined: 07 Jan 2011, 17:31
Has thanked: 57 times
Have thanks: 108 times

Re: EarthQuaker Devices (EQD)- Bellows

Postby Manfred » 31 Jan 2017, 09:13

The JFET acts like a diode.
The gate-source voltage is allways positive and therefore the channel resitance is very low.
That explains why the short between gate and source has not affects nothing.
I removed the JFET in the simulation circuit, connected the base and the 10kOhms resistor,
added a small-signal-diode between base and collector, and the circuit works in the same manner.
What a supprise. :o

For this message the author Manfred has received thanks:
modman (01 Feb 2017, 21:39)
Manfred
Resistor Ronker
 
Posts: 422
Joined: 05 Apr 2009, 00:42
Has thanked: 724 times
Have thanks: 314 times

Re: EarthQuaker Devices (EQD)- Bellows

Postby Silver Blues » 01 Feb 2017, 03:55

Oh so it's kind of like a Bazz Fuss type thing but with a JFET? Interesting...
User avatar
Silver Blues
Breadboard Brother
 
Posts: 69
Joined: 23 Apr 2013, 20:25
Location: Atlantic Canada
Has thanked: 12 times
Have thanks: 21 times


Return to Boutique Stompboxes dissected...

Who is online

Users browsing this forum: agung, andlord, Cannibal, Class 3 Rock Device, dv8r601, efe, grojon, Jan1966, moko15, storyboardist and 22 guests