The Fix Is In

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  • Guest
on: July 12, 2018, 10:21:07 AM
 I found a eerily similar box design for what I had planned to make originally a Fix circuit. Leeds & Northrup produced this decade box with four controls. Yes, I do hesitate to open it up and take out the precious parts that will no longer be used, but if I don't, then they go that way of being useless.

  So be prepared to witness the wedding of a Fix to it's distant cousin '4745'. Speak now or forever hold yer' piece.


  • Guest
Reply #1 on: July 13, 2018, 01:58:23 PM
I have to add something here. The level of quality in this decade box is an eye opener. I have seen it before, but it has never stopped me from taking a moment to look around at the thought, design, and attention payed to what is still a humble piece of test equipment. Parts are thick and able to take a shock from dropping maybe even worse. The tolerances and feel of the dials is like few made at any price these days. As do my work inside of this unit, I try more than ever to have at least a decent amount of pride and craft to equal, if I can, the original effort produced. Photos to follow (sorry, it is now too late for inside photos of the original device).


  • Guest
Reply #2 on: July 16, 2018, 10:00:11 AM
 This is the first step in re-purposing the original circuit. I am hoping that this is to be the most difficult step, since alignment of all four pots at the same time with the centers of each original knob was challenging. The rotation of each pot is acceptable. I drilled the holes for the shaft slightly over sized, so that when the epoxy was poured for each pot (not shown in this photo), there would be a little give here and there. It was a good idea, as I don't have much more than a drill press and a good eye to work with.
 Next step will be the mounting of the solder lugs to accept the capacitors and resistors.
« Last Edit: July 16, 2018, 10:01:57 AM by 4krow »


  • Guest
Reply #3 on: July 17, 2018, 08:09:06 AM
 Mounting the solder lugs was a challenge for big shaky hands. I got through it, but made a mess with epoxy that I had to clean up. I also used small screws that became the biggest challenge. So, I still have some solder gaps to fill, but the square grounding wire is in place. I know that the old guys had jigs for all of this bending, and I wish that I had the same! Every little thing shows here.
 Next I will solder in the caps and resistors.


  • Guest
Reply #4 on: July 18, 2018, 12:58:42 PM
  Rather than include yet another photo, I will conclude this thread with my observations. As expected, I like having this unit available. I may even try it with headphones, just to hear a bit better the influence of the circuit. In my shop system, it was pretty easy to hear the difference that the BSC controls had over the bass. Simply put, bass notes were rounded out better than without the circuit. The treble side did not have the effect that I was hoping for. It is unfortunate that my hearing has taken a tumble so as not to be able to notice subtle differences anymore, but that is the way it is. Again, I might be able to tell with headphones on.
 The next step was to insert this unit into my main system since that is where I intend to use it. Fortunately, there is just enough room right behind the amp so that the unit fits neatly, out of sight, and can use the short interconnect cables recommended. I used 1/2 meter interconnects at the input of the Fix unit, and less than 1/2 meter interconnects from it's output to the amp's input. Yes, it makes quite a difference using too long a cable as I first tried out. So, the settings that worked best in my system were to have the treble setting at the 4db position, the 5k was the chosen position, and then for the bass, the 4db BSC position, and a 6"-12" baffle size. What I was actually hoping for is a bit more bass, which worked out nicely, and a 'Reduction in the Midrange'. Might sound backwards to some, but that is exactly the problem that I have with these drivers. They exhibit a bit more shout than I care for. After a good breaking in, that seems to have been reduced, but with the addition of the Fix circuit, it is the right level now for my ears.... In the future, I will complete my other project that marries a Quickie pre-amp with a Fix circuit in one chassis, and I bet it works out even better (Remember, I call it the Q-Fix)
 First time that I ever saw this sort of circuit used, it was in the Yamaha line of 'Natural Sound' integrated amps, where instead of a typical loudness control that boosted bass and treble, the midrange was cut to produce much the same effect. Pretty smart I think.

Offline 2wo

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Reply #5 on: July 18, 2018, 05:51:19 PM
I love what you do with those old boxes. Giving classic parts a new life, is really cool...John

John S.


  • Guest
Reply #6 on: July 18, 2018, 07:00:11 PM

  Thanks so much. As can probably be expected, choosing a box for most any project can be a challenge. Better too big than too small, that is for sure, but there are size considerations making the right choice more than a coincidence. The question becomes just how good is the condition of the box. 'Mint' isn't the only over used word in ads. So are 'small scratches', 'will be carefully packed', and on it goes. Besides that, there is one thing that I find a bit difficult. Even though the original unit may be out of date or even in disrepair, it can be a piece of near museum quality. I don't like taking something apart without at least admiration and respect for 'where' it came from in history, or even the life of the individual who used it.