EQD - Disaster Transport JR  [traced]

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

batteryacidtea
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Post by batteryacidtea »

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

bugg
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marshmellow
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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:.

jrfox92
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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.

marshmellow
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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.

phatt
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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.

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snk
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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 ?

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snk
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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 ?)

audioguy
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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?

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Post by Optical »

For wet only, disconnect R9

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