GDIY passive 'Mojo' box

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cpsmusic

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This sounds like a great project so please keep going with it! I'm more from the music/audio production side of things so I can't help much with the design. But I'd definitely agree with some of the ideas posted above, especially the pre/de-emphasis idea so that harmonics could be generated in specific frequency areas. That's done a lot these days in mixing, especially for things like adding high end to bass, low end to snares, etc.

Cheers,

Chris
 

Potato Cakes

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At some point if I get back to tinkering with this concept I might do something like a transformer to diodes/zeners to transformer. Possibly using a power transformer reverse wired that would go 9V to 120V to get the voltage higher to be able to drive or saturate some sort of rudimentary semiconductor array and then another transformer that would get the signal back to line level.

To me, "Mojo" is either accentuating the low mids or creating subtle distortion. Doing this passively really limits circuit options that would produce any sort of useful result.

Thanks!

Paul
 

SWAN808

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How about a group DIY Colour module? Then it doesnt need to be passive - and can be proto on the colour breadboards...I have tried most of their modules and IMO the best are the CTX and LTL Transformer ones which use a discrete op amp into a transformer. I've experimented with most of the small transformers and although a noob, I would say the Edcore used by LTL and the Cinemag used by DIY are the best. They are both about £20.

OEP I've tried a load and wasn't that impressed, but I may have been loading them wrong...they had a lot of ringing to deal with also, an no specific sound to speak of if even degrading it a tad...the Triad ones are, well...

If you line up two of these CTX or LTL tx modules you start to get into the territory of the Kzrog plugin, but it's a subtle effect. Plugins always exaggerate the real world, because subtle in the analogue world sounds great, in the plugin world its meh no one would buy it. A little extra punch, plus the discrete op amps can over drive and you clip the signal a fraction gaining some level.
 
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ruffrecords

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OEP I've tried a load and wasn't that impressed, but I may have been loading them wrong...they had a lot of ringing to deal with also, an no specific sound to speak of if even degrading it a tad...the Triad ones are, well...
Loading a transformer does not alter its characteristics. The main factors are core size, core material, primary voltage and frequency.

Cheers

Ian
 

Richard James

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How about a group DIY Colour module? Then it doesnt need to be passive - and can be proto on the colour breadboards...I have tried most of their modules and IMO the best are the CTX and LTL Transformer ones which use a discrete op amp into a transformer. I've experimented with most of the small transformers and although a noob, I would say the Edcore used by LTL and the Cinemag used by DIY are the best. They are both about £20.

OEP I've tried a load and wasn't that impressed, but I may have been loading them wrong...they had a lot of ringing to deal with also, an no specific sound to speak of if even degrading it a tad...the Triad ones are, well...

If you line up two of these CTX or LTL tx modules you start to get into the territory of the Kzrog plugin, but it's a subtle effect. Plugins always exaggerate the real world, because subtle in the analogue world sounds great, in the plugin world its meh no one would buy it. A little extra punch, plus the discrete op amps can over drive and you clip the signal a fraction gaining some level.
Love this idea and I agree with the CTX/LTL tx comments. I just got some Colour breadboards. I have no clue where to start though, so if this picks up I’ll be following.
 

Potato Cakes

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Love this idea and I agree with the CTX/LTL tx comments. I just got some Colour breadboards. I have no clue where to start though, so if this picks up I’ll be following.
Then that should probably be it's own post. The premise for this discussion is to do it passively, which I think is a fun challenge. The color modules are great but if you're going that route then all you really need is a connector to interface with each individual module that adapts to your design needs.

Thanks!

Paul
 

fragletrollet

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Well the G-21 Infundibilum from Gyraf (fitting name! :geek:) might be somewhat in this direction, no? Would be really cool with something along those lines... not that I've ever tried one :D
 

fragletrollet

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Well the G-21 Infundibilum from Gyraf (fitting name! :geek:) might be somewhat in this direction, no? Would be really cool with something along those lines... not that I've ever tried one :D

On the software side, be sure to check out Kush Audio/UBK's Pusher plugin. Exploring transformer saturation, you can fade between different core materials that are stressed at different levels, plus a really cool limiter and something of a mid/treble compressor. Oh, and his UBK-1 is my favorite software comp, awesome stuff (y)
 

gyraf

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:) Very funny, but also very far from the actual working principle of the G21 (other than perhaps for the overall-clipper part).

Infundibulating relates more to magnetic amplifiers in that we selectively collapse the core magnetic field by loading it with a DC-component (derived from signal itself :) ) - sorta an extended but passive version of the principle in Ortofon STL631 - http://www.etec.dk/foto/ortofon/STL631_01-Schematic-StereoValveTrebbleLimiter.jpg

principle description here : https://www.jailhouse.dk/dia/ortophon.pdf

/Jakob E.
 
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PermO

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:) Very funny, but also very far from the actual working principle of the G21 (other than perhaps for the overall-clipper part).

Infundibulating relates more to magnetic amplifiers in that we selectively collapse the core magnetic field by loading it with a DC-component (derived from signal itself :) ) - sorta an extended but passive version of the principle in Ortofon STL631 - http://www.etec.dk/foto/ortofon/STL631_01-Schematic-StereoValveTrebbleLimiter.jpg

principle description here : https://www.jailhouse.dk/dia/ortophon.pdf

/Jakob E.

Ah wow ! ... thanks for this !

Now I finally know the wiring scheme of the pair of JS ST3450 I'vo got here,... they come from an old STL631 that was converted to run as a radio limmiter for FM radio, then it retired, got mangled by someone, got mangled by another person, ended up in a pile of junk of some other guy's attic... where I pulled it out as it had some transformers on it.

I have some more parts of this device, the power transformer, the frame, ST3452 and ST3451.

I was planning on using the input transformers for my stereo 864 build, I've used them in a transformerbox and they sound great, love the sweet top end of these. I notice in the 631 schematic the CT is at the input side, in the 864 schematic it is at the output side. They sound the same in both directions to me, so I guess I will be fine reversing them.

I have watched that youtube clip before, nice guy, nice concept.... but that audio, either processed or not, sorry but that just sounds so bad to my ears, the only thing I hear is nasty squarewave distortion.
I've tried some of this stuff and all I got was nastyness.

I think creating a passive device that sounds good really is a fine art, before you know it you will end up with nasty distortion and it will suck the life out of the dynamics and details. Not an easy thing to do, and that's probably why there are not so many out there.
 

sonnyjwong

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Oct 11, 2020
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Transformer box is new to the in this analog equipment (I've been mix mastering ITB for year).
After I know about transformer box and buy it from 51xaudio, i knew it that i very need it to make "analog mojo" my digital wolrd mix mastering. and I read about mojo maestro by ethan winer.

so after I buy from 51xaudio i search in aliexpress that I found something interesting and I tried it.
its say that lundahl 1527 klon an jensen klon. I give a shot. its below $100 usd with tax and ship in my country (Indonesia)

(all transformer i buy are 1+1:1+1)

Lundahl1527 klon

Jensen klon

I tried to add mojo maestro after transformer box, as ethan told me in messenger.
but i have question.

output from transformer box are balance, but input / output mojo box are unbalanced.
how to deal with it ? (I'm sorry I'n not elektrikal nerd).

does anyone ever try to put transformer box before mojo? and does anyone ever try china transformer?
 

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andow

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I built a passive clipper based on the Mojo Maestro. Very simple but a lot of fun to play around with...😃

I added switchable input transformer, three different diode configurations and variable low pass filter.
 

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guze

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Mar 10, 2009
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Very very nice and all passive, can you share in a easy way to understand?
 

skipwave

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Los Angeles
How about a group DIY Colour module? Then it doesnt need to be passive - and can be proto on the colour breadboards...I have tried most of their modules and IMO the best are the CTX and LTL Transformer ones which use a discrete op amp into a transformer. I've experimented with most of the small transformers and although a noob, I would say the Edcore used by LTL and the Cinemag used by DIY are the best. They are both about £20.

OEP I've tried a load and wasn't that impressed, but I may have been loading them wrong...they had a lot of ringing to deal with also, an no specific sound to speak of if even degrading it a tad...the Triad ones are, well...

If you line up two of these CTX or LTL tx modules you start to get into the territory of the Kzrog plugin, but it's a subtle effect. Plugins always exaggerate the real world, because subtle in the analogue world sounds great, in the plugin world its meh no one would buy it. A little extra punch, plus the discrete op amps can over drive and you clip the signal a fraction gaining some level.

The lower turns ratio OEP works good in G-1176, but the ringing when used as an input to Neve circuit was well documented by the great Joe Malone.

 

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