Earthquaker Devices - Disaster Transport JR  [traced]

General documentation, gut shot, schematic links, ongoing circuit tracing, deep thoughts ... all about boutique stompboxes.
Post Reply
User avatar
skywise
Breadboard Brother
Information
Posts: 79
Joined: 23 Dec 2011, 05:09
Has thanked: 48 times
Been thanked: 21 times

Post by skywise »

http://www.earthquakerdevices.com/devic ... portjr.htm

Nice build quality inside. Nothing new to see here but a picture is nice anyway.
EQD_DTJR_01.jpg

User avatar
batteryacidtea
Breadboard Brother
Information
Posts: 104
Joined: 18 Feb 2009, 03:42
Has thanked: 57 times
Been thanked: 17 times

Post by batteryacidtea »

Nice! How do you like it? I'm really interested in understanding how does the tone control works here!

User avatar
bugg
Breadboard Brother
Information
Posts: 133
Joined: 11 Feb 2013, 03:10
my favorite amplifier: Fender Twin
Has thanked: 46 times
Been thanked: 289 times

Post by bugg »


User avatar
marshmellow
Cap Cooler
Information
Posts: 469
Joined: 16 Aug 2007, 07:31
Location: Germany
Has thanked: 18 times
Been thanked: 125 times

Post by marshmellow »

Ever since the Rebote every PT2399 Delay has to suffer from this nonsensical input stage design. Everybody just copies it again and again without wasting a single thought :lol:.

User avatar
jrfox92
Breadboard Brother
Information
Posts: 70
Joined: 11 Jun 2014, 04:46
Completed builds: Death by Audio Fuzz War
Electro-Harmonix Big Muff Pi V5
Skreddy Lunar Module
Colorsound Overdriver
Electro-Harmonix Big Muff Pi Multi-Diode and Feedback Mod
Electro-Harmonix Holy Grail Room Reverb and Reverb Length Mod
Boss DS-1 Synth Circuit Bend
Location: Akron, Ohio
Has thanked: 3 times
Been thanked: 54 times

Post by jrfox92 »

marshmellow wrote:Ever since the Rebote every PT2399 Delay has to suffer from this nonsensical input stage design. Everybody just copies it again and again without wasting a single thought :lol:.
:| :scratch: :hmmm:
What's nonsensical about it?
Do you just have a problem with input buffers?
The only difference between the Rebote and the data sheet (from what I remember) is a Jfet boost at the input.

User avatar
marshmellow
Cap Cooler
Information
Posts: 469
Joined: 16 Aug 2007, 07:31
Location: Germany
Has thanked: 18 times
Been thanked: 125 times

Post by marshmellow »

That's not a buffer, that's a noise generator with a NF in excess of 20dB. For a unity gain stage that is just ridiculous (and copied blindly by Mad Professor, Wampler, several Madbean designs, many DIY variations, ...). An inverting stage as a high-impedance input is simply wrong. You either have low impedance, or high noise, choose your poison. The way to go is to use a non-inverting buffer and don't care about the polarity inversion. Which is a bit schizophrenic in the first place considering that 99% of other effects don't care a single bit about this issue. Or you put a JFET/BJT buffer in front of it and decrease the resistors to 10k.

Or you build something that was properly designed from the beginning, like the PT80, the original PT2399 design, or Dirk's contest entry.

User avatar
phatt
Transistor Tuner
Information
Posts: 1174
Joined: 04 Aug 2010, 05:17
Location: Morayfield SE Qld AU
Has thanked: 3 times
Been thanked: 316 times

Post by phatt »

marshmellow wrote:That's not a buffer, that's a noise generator with a NF in excess of 20dB. For a unity gain stage that is just ridiculous (and copied blindly by Mad Professor, Wampler, several Madbean designs, many DIY variations, ...). An inverting stage as a high-impedance input is simply wrong. You either have low impedance, or high noise, choose your poison. The way to go is to use a non-inverting buffer and don't care about the polarity inversion. Which is a bit schizophrenic in the first place considering that 99% of other effects don't care a single bit about this issue. Or you put a JFET/BJT buffer in front of it and decrease the resistors to 10k.

Or you build something that was properly designed from the beginning, like the PT80, the original PT2399 design, or Dirk's contest entry.
:applause: :applause: :applause: :thumbsup :thumbsup :thumbsup
Take Marshamellow's advice,, print that out in RED Bold and refer to it everytime you build a pedal.
You don't need noise gates and other crap if you build them properly,,, jezz the front end of a TS9 with BJT would out perform in a noise shoot out.
Noise is the hidden enemy in pedal design and easy to get caught as it's not obvious to the novice.
Phil.

User avatar
snk
Resistor Ronker
Information
Posts: 280
Joined: 14 May 2013, 20:48
Has thanked: 97 times
Been thanked: 14 times

Post by snk »

Hello
I built and EQD Disaster Transport JR and i like it.
I also started studying other PT2399 designs, and found the Hamlet Delay, where (among other things) it is suggested to put a green LED from PT2399 pin7 to ground in order to avoid clipping the PT2399 input.
Did anyone try it on the Disaster Transport JR ? Would it work the same way ?

User avatar
snk
Resistor Ronker
Information
Posts: 280
Joined: 14 May 2013, 20:48
Has thanked: 97 times
Been thanked: 14 times

Post by snk »

Also, what do the antiparallel diodes to ground do, in the EQD - Disaster Transport JR ?
(Maybe it is a crude limiter for the feedback ?)

User avatar
audioguy
Resistor Ronker
Information
Posts: 262
Joined: 27 Nov 2007, 14:47
Has thanked: 22 times
Been thanked: 7 times

Post by audioguy »

What might turn out to be a silly question-
How difficult would it be to add a toggle switch to kill the primary signal, allowing only the delayed signal to pass through?

User avatar
Optical
Breadboard Brother
Information
Posts: 125
Joined: 28 Jul 2016, 22:44
Location: Auckland
Has thanked: 16 times
Been thanked: 17 times

Post by Optical »

For wet only, disconnect R9

User avatar
bc108
Breadboard Brother
Information
Posts: 78
Joined: 04 May 2017, 15:39
my favorite amplifier: BE100
Has thanked: 34 times
Been thanked: 4 times

Post by bc108 »

I'm thinking in build this one into a small veroboard, and add before some Echoplex Preamp.
Is this one more "lo-fi" compared to Deep Blue, or Wampler Faux?

Post Reply