JO-PA-CA P.I.B. (passive inductance box)

[cspar]

After getting a old PA sniffing unit that is similar to a transistor radio circuit I ordered a couple of small signal transformers intending to build a few circuits that I've been looking into.

Here's the first one albeit a bit more complex than I what I was going to build at first. My intention was originally was just a pickup simulator.

Right after the transformer order I got an Newcomb E-17 amp that I'm looking to mod, that thread is here.
viewtopic.php?f=2&t=31320

So, I figured that instead of just making a pickup simulator I might as well make a utility box that's more versatile to help with the amp modding as well as builds in general.

I can up with something that's a combination of Craig Anderton's Impedance Tester, a slightly modded version of Jack Orman's pickup simulator and a slightly modded version of Phil Abbot's speaker to line resistive load cobbled together in one circuit.

All 3 of these folks are supportive of diy stuff so I hope I'm not ruffling feathers posting the circuits combined as a multifunction diy testing unit.

I just finished the schematic and haven't started on the build yet. Here's the EagleCad schematic if someone wants to do any edits.

JO-PA-CA PIB.sch

EagleCad Schematic

(177.87 KiB) Downloaded 46 times

If I mount the transformer 90 degrees from the jack and not crammed together in the enclosure would there be any problems with getting accurate impedance readings due to it's field?

I have long switchcraft jacks from a studio buss that I'm going to use and thick U piece of aluminum trim that's 2x2 and as long as I want it. The necessary and welcome extra space was part of the inspiration for the combination.

All the test pins are going to be bannana plug jacks.

So, I'm curious if anybody has any ideas how to improve it or add it to make it more versatile. And of course I wouldn't mind if other eyes looked it over for errors.

I wanted to add an isolation path to the box but the only 1:1 transformer that I have is a TY-141p and I haven't been satisfied with any of my passive tests with it so far. Does anybody have experience with this transformer besides using it for a Hudson Broadcast?

Part of my reasoning for a tranformer isolation path is brainstorming around adding a varitone option to the pickup simulator and having that transformer be mutli use at the same time.

Thanks in advance for any advise.

[cspar]

I guess I should explain the circuit a bit...

1st off.. No stereo cords here. It is designed for for only using mono cords going into the input jack. I'll get to that latter.

The JO path is a take on Jack Orman's guitar simulator with switchable tone caps and pot values allow for a wider variety of setup flavors.

My additions are pretty basic and I have been done before by others.

On his site he explains the circuit in more detail.

The PA path is Phatt's speaker to line resistive load circuit with capacitor options added.

This path needs to be mono and thus having the input ring be ground because the sleeve is lifted from the 3pdt when this path is chosen.

To make this work the input sleeve has to be shielded from the enclosure.

This post of his is where I got the circuit, the whole thread is a good read.
viewtopic.php?p=259117#p259117

The CA path is a simple impedance testing circuit from a Craig Anderton article over at Harmony Central.

He did a wonderful job at explaining it over on that site.

The JO-PA-CA P.I.B. is really just these 3 circuits together with a slight bit more flexibility.
My theory is if I'm gonna make a diy bench tool, I might as well make it full feature.

JO-PA-CA kind of rhymes with Chewbacca but I not sure if any of the guys in the name would identify as a wook.

I hope this explanation helps.