EHX - Tube EQ  [schematic]

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cspar
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Post by cspar »

Does anybody have the schematic or some gut shots for the ehx tube eq.

I've searched around and can't find anything more than basic descriptions that don't mean much.

I'm curious how much of the topology is SS and what the B+ voltage is.
"Just because the forgoing circuits have produced results there is no reason experimenting won't lead to added results." L. E. Darling, in his article containing the earliest published vacuum tube synthesizer circuit, Popular Science Jan 1920

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ppluis0
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Post by ppluis0 »

Hi cspar,

There is a diagram showing only the audio path, posted previously here by forum member Borislav Gajic:

Image

The frequency of parametric filter is varied controlling the brightness of leds on those four vactrols (at the same time in the same direction).

The +B supply is obtained feeding the unit with an 12Vac wall wart to an internal 12 to 220v transformer connected backwards.

I have the original EX pdf file belonging this pedal, so if forum administrator agree to be posted here I need indications of how a file can be attached to a post.

Cheers,
Jose

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cspar
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Post by cspar »

Thanks Jose.

Nice to see that it's a mostly tube path that runs on 220v. I was hoping for something along those lines.

From your description it seems the frequency pot is just a trimmer for the vactrol leds?

Do you happen to know the specs on the vactrols?

Is there already a thread on the EJX Tube EQ already? :hmmm:
"Just because the forgoing circuits have produced results there is no reason experimenting won't lead to added results." L. E. Darling, in his article containing the earliest published vacuum tube synthesizer circuit, Popular Science Jan 1920

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ppluis0
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Post by ppluis0 »

There is a thread somewhere in this forum but I can't find it.

Don't know exactly what kind of vactrols employs this unit and the frequency is controlled by an op amp that can follow an external control voltage or one potentiometer in the front panel.

If we analyze the diagram the four photocells are connected as a twin T filter so I think that must be of equal resistance variation.

Repeat: if moderator agree (and explain how to upload a file) I have an original pdf diagram of this pedal.

Cheers,
Jose

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Post by modman »

ppluis0 wrote: 03 Oct 2021, 04:03 There is a thread somewhere in this forum but I can't find it.
I cannot find it either, but don't remember seeing it...
ppluis0 wrote: 03 Oct 2021, 04:03Repeat: if moderator agree (and explain how to upload a file) I have an original pdf diagram of this pedal.
PDF's don't show up as a preview, you have to convert/export the PDF pages to JPG or some other image format for them to show up in the post.

Feel free to post the schematic -- worst thing ever happened was receiving a Cease and Desist from Diana @ EHX. Perhaps they don't care so much anymore after making a bunch of cash from cloning the Klon Centaur using the FSB schematic. :idea:
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Post by ppluis0 »

modman wrote: 03 Oct 2021, 11:55 Feel free to post the schematic
Hi modman, if EHX took advantage of our Klon research, then they have no reason to complain about publishing this diagram. 8)

There are the diagrams showing the supply and vactrol control subsections discussed previously:

Image

Image

Cheers,
Jose

P.S.: I have another 23 original files from EXH ready to disclose here at the forum :mrgreen:

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