GDIY passive 'Mojo' box

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Tubetec

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Nice find Permo ,

I got a score of -33db , but I just used earphones run off the H/P out of the laptop and used the two tone 90-800hz , I might repeat the test next time with better gear and see if I can determine a difference at lower distortion levels
 

Tubetec

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Enjoyed the 1945 article , thanks Ian , I'll work backwards through the other stuff I think.
 

Newmarket

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I think you are right. I am an electronic engineer by training so words like saturation have a very specific meaning for me. The explosion of project studios in the last century has meant there are lots of people using electronic gear who pick up their technical knowledge informally. There is nothing wrong with that but it does tend to lead to a distortion (sic) of well defined technical terms.
Very true. From the 'Guitar World'' some of my favourite terms are "Transparent Overdrive" and a "Warm sounding clean channel".
Understandable of course esp when amp inputs may be labelled 'Drive' and 'Clean'.
 

Tubetec

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Interesting to note from the 1945 article that 0.1% thd wasnt the limit of the human ears abillity to decern distortion ,but in fact the limit of what they could measure back then .
 

looebloke

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often wondered what the "magic box" was that Emile Ford RIP used to tote round with himself to top-flight studios (Pink floyd albums etc) .... could it have been something like this?? Wonder if his secret died with him
 

thomasdf

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I've had a pair of Western Electrics 111C transformers. When LOUD signal was going thru them, there definitely was magic happening. But it had to be pretty darn loud. So I toyed with the idea of having a gain stage in front of them and a pad after, and after a while I sold them
 

hodad

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Going back a ways to the discussion of the RND "Silk" feature--from what I gather this is basically putting a slight DC bias on the transformer primary to accentuate even harmonics. Now DC bias eliminates the "passive" part of the mojo box, but would it be possible to do a simple Silk type circuit with just a trafo, a battery or wall wart, & a few passive parts?
 

mjrippe

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Or would it be possible to achieve the same effect using a permanent magnet that you physically move relative to the core of the transformer on some kind of pivot maybe?

Cheers

Ian
Oooooooooh, fun! Have you ever seen the insides of an Allison Labs filter set? Huge magnets and inductors that move to change the cutoff frequency.

My friend found a rackmount "noise generator" that had vacuum tubes. One of the tubes had a torroidal magnet around it that created the noise.
 

ruffrecords

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Oooooooooh, fun! Have you ever seen the insides of an Allison Labs filter set? Huge magnets and inductors that move to change the cutoff frequency.
No, I was not aware of them A quick google search turned up some vague information but no good gut shots. Do you have any you could sha
 

Tubetec

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Could phantom power be used to supply DC to an otherwise passive box for the purposes of changing how the transformer/inductor cores distort?
 

gyraf

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Yes, the tuning of a filter with DC-magnetization is definitely a thing - used e.g. in the Ortofon de-esser I mention / link to on page4 (post75) of this thread

/Jakob E.
 

ruffrecords

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Could phantom power be used to supply DC to an otherwise passive box for the purposes of changing how the transformer/inductor cores distort?
I don't see why not as long as no more that a small number of mA of current is required to make an audible difference.

Cheers

Ian
 
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