LT44 transformer-as-inductor for a honey special fuzz phaser

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LT44 transformer-as-inductor for a honey special fuzz phaser

Postby tabbycat » 10 Jun 2015, 14:59

hey all,

am looking at building dino's vero of the honey special fuzz with the autowah phaser, and have discovered there are two types of LT44 transformer available. i wondered if anyone can advise me which would be most suited to the context they are being used for here?

dino's comments about the LT44 are here: viewtopic.php?f=19&t=16635&start=20#p208932

digi2t wrote:OK, major update....
The 42TL019 transformers just don't cut the mustard. Compared to the TDK 4 Henry inductors, their pretty much spot on for inductance. Problem is resistance. The transformers are more than double the resistance. This makes the "wah" effect very muffled, and DULL. Compared to the original unit, it sounds like an old Maytag chugging away.

So, it was back to the drawing board....

Happy discovery though. Going through my stock, and trying different inductors that I had, I came upon two LT44 transformers that I had bought a while back. Trying the different connections, I found that the outer pins on the secondary really work well. The outer pins of the secondary side, I have 1 Henry, and 60 ohms (versus 4 Henry and 220 ohms of the TDK). It now gives me pretty much the same effect as the original. I'm no expert on inductance, but it's as if the resistance of the transformer plays a bigger role than the inductance. By adjusting the 100nF cap, I could fine tune the tone of the sweep, and I've gone with a 120nF box cap. Not a big change, but my ears said "better".

and here are the descriptions of the two LT44 i'm looking at:

"LT44 - Yellow

The primary side has a nominal impedance of 20K Ohms. The secondary side is nominally 2k Ohms and has a centre tap. The D.C. resistance of the primary is approximately 480 Ohms, and that of the secondary is 107 Ohms. The theoretical voltage and turns ratio is 3.2 and something close to this is seen when testing at 1kHz with the appropriate input and output impedances connected. These have input and output impedances that are more useful for making ring modulators than the LT700s."

"LT44 / P631M Blue

This is the same as the one with the yellow tape but has the more usual blue winding tape and the untapped primary side has a higher d.c. resistance at about 1.08K. If you're looking for low internal resistances to minimise losses, you would prefer the yellow type.

These were originally used to match germanium transistor stages in radios, a role that no longer really exists but these are still useful to match crystal radio detectors to higher impedance magnetic or crystal earpieces. This allows the detector diode to work at a higher impedance section of the circuit where the higher voltages overcome the forward diode drop more easily leading to higher efficiency. The transformer also provides a d.c. path to ground when using a crystal earpiece, doing away with the need for a lossy bleed resistor across the crystal element."

the resistance seems (to my basic understanding) to be more or less the same, but as the yellow mentions being more suitable for ring mods and as this is for a tone modulator of sorts (phaser/autowah) my insticts are that the yellow may be what i need. but a nod in the right direction from a wise head would be much appreciated?

many thanks.
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