EQD - Disaster Transport JR

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EQD - Disaster Transport JR

Postby skywise » 26 Nov 2012, 17:34

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
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batteryacidtea (29 Nov 2012, 22:39)
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Re: EQD - Disaster Transport JR

Postby batteryacidtea » 29 Nov 2012, 22:40

Nice! How do you like it? I'm really interested in understanding how does the tone control works here!
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Re: EQD - Disaster Transport JR

Postby bugg » 15 Dec 2017, 21:27

Schematic.png

PCBs available here: http://www.pedalpcb.com/product/cataclysm/
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dv8r601 (16 Dec 2017, 02:09)
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Re: EQD - Disaster Transport JR

Postby marshmellow » 16 Dec 2017, 01:50

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:.
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Re: EQD - Disaster Transport JR

Postby jrfox92 » 16 Dec 2017, 09:59

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.
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Re: EQD - Disaster Transport JR

Postby marshmellow » 16 Dec 2017, 14:20

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.

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heaterman (16 Jan 2018, 17:49)
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Re: EQD - Disaster Transport JR

Postby phatt » 16 Dec 2017, 14:38

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.
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