Hi everyone,
Volker aka [silent:arts] and myself have been working on something kind of new the last month or so. It is what we have been calling a “plug-in” HiZ for Direct Inject applications. Our thought is to have a standardized footprint for a small PCB, which can contain many different HiZ circuits for different applications. The idea is to be modular much like the 2520 DOA concept. Volker has authored the footprint/layout, which is on a board measuring 28mm X 28mm. The board shall contain 6 Mill-Max pins exactly the same type as we all have been using for our DOA projects.
Our thought is that anyone designing, building, etching or whatever…a mic preamp PCB, can incorporate this footprint and use for Direct Inject. This really opens up some great possibilities. 8)
As of now, Volker has a good ole passive, transformer version which has the standard Jensen JT-DB-EPC footprint to it. For other passive options, we have the wonderful Ed Anderson hard at work designing and creating his very own DI transformer. Ed was pretty excited about the idea when I emailed him. He said he had thought about a DI transformer in the past but wanted to do something very unique. I wait with baited breath.
Next we have an IC version. This is a circuit that Volker has come up with. There are a few different versions of this out there already…but now we have one for our “plug-in” format.
And that brings us to the multiple FET versions. Volker has many already drawn up. I will let him post what he has done. We have contacted a few of the guys who have used these type circuits in their projects already. Like Peter Purpose and Fabio. Both have given their blessings to publish the circuits in our new format. An email has been sent to Dan Kennedy and we are anxiously awaiting his response to utilize his already published circuit.
The HiZ Plug-In will run on a single voltage rail. Someone building a standard API style preamp may want to run the HiZ off of the +16V rail. Someone building a Neve may want to run on +24V. A person who has the new GDIY 51x rack may want the option to run on either.
As you can see, there are loads of options and possibilities.
Here are the basic specifications for the PCB from Volker.
One of the main reasons this came together was the new VP312 board that I was working on. I wanted to utilize the 51x option like the possibility of the higher voltage rails. I sent Volker my Gerbers to see how I made the voltage switchable and so on. He replied back, “Looks good but you are missing the DI option”. I explained my thought for the VP312 PCB and how the DI would not fit for some of the various alternative uses I have planned. I told him my next project would have to be the VP312DI. I also expressed the desire to inject the HiZ signal before the input transformer not directly before the DOA. Most seem to do this and it is just great but I wanted something a little bit different. I wanted something more conventional like similar to using a standalone DI box. Volker said, “Have you thought of a FET circuit like Dan Kennedy uses? The Neve type DI could sound really cool and different in front of the API preamp”. I suppose you can figure out the rest of the evolution.
This is what I have come up with for the VP312DI. I am using an auto-switching method to de-energize a 12V relay which is triggered by opening the normalled sleeve/ground connection on a ¼” mono PCB jack. I have also made the +V for the HiZ Plug-In switchable between 16V and 24V. I thought this would provide some nice options. The relay circuit is zener shunt regulated to 12V off of the +16V rail so this way it will still function if the PCB is clipped to operate in a standard 500 series rack. The relay will be a TQ2-12V. Cheap and reliable.
Cheers all, Jeff
Volker aka [silent:arts] and myself have been working on something kind of new the last month or so. It is what we have been calling a “plug-in” HiZ for Direct Inject applications. Our thought is to have a standardized footprint for a small PCB, which can contain many different HiZ circuits for different applications. The idea is to be modular much like the 2520 DOA concept. Volker has authored the footprint/layout, which is on a board measuring 28mm X 28mm. The board shall contain 6 Mill-Max pins exactly the same type as we all have been using for our DOA projects.
Our thought is that anyone designing, building, etching or whatever…a mic preamp PCB, can incorporate this footprint and use for Direct Inject. This really opens up some great possibilities. 8)
As of now, Volker has a good ole passive, transformer version which has the standard Jensen JT-DB-EPC footprint to it. For other passive options, we have the wonderful Ed Anderson hard at work designing and creating his very own DI transformer. Ed was pretty excited about the idea when I emailed him. He said he had thought about a DI transformer in the past but wanted to do something very unique. I wait with baited breath.
Next we have an IC version. This is a circuit that Volker has come up with. There are a few different versions of this out there already…but now we have one for our “plug-in” format.
And that brings us to the multiple FET versions. Volker has many already drawn up. I will let him post what he has done. We have contacted a few of the guys who have used these type circuits in their projects already. Like Peter Purpose and Fabio. Both have given their blessings to publish the circuits in our new format. An email has been sent to Dan Kennedy and we are anxiously awaiting his response to utilize his already published circuit.
The HiZ Plug-In will run on a single voltage rail. Someone building a standard API style preamp may want to run the HiZ off of the +16V rail. Someone building a Neve may want to run on +24V. A person who has the new GDIY 51x rack may want the option to run on either.
As you can see, there are loads of options and possibilities.
Here are the basic specifications for the PCB from Volker.
One of the main reasons this came together was the new VP312 board that I was working on. I wanted to utilize the 51x option like the possibility of the higher voltage rails. I sent Volker my Gerbers to see how I made the voltage switchable and so on. He replied back, “Looks good but you are missing the DI option”. I explained my thought for the VP312 PCB and how the DI would not fit for some of the various alternative uses I have planned. I told him my next project would have to be the VP312DI. I also expressed the desire to inject the HiZ signal before the input transformer not directly before the DOA. Most seem to do this and it is just great but I wanted something a little bit different. I wanted something more conventional like similar to using a standalone DI box. Volker said, “Have you thought of a FET circuit like Dan Kennedy uses? The Neve type DI could sound really cool and different in front of the API preamp”. I suppose you can figure out the rest of the evolution.
This is what I have come up with for the VP312DI. I am using an auto-switching method to de-energize a 12V relay which is triggered by opening the normalled sleeve/ground connection on a ¼” mono PCB jack. I have also made the +V for the HiZ Plug-In switchable between 16V and 24V. I thought this would provide some nice options. The relay circuit is zener shunt regulated to 12V off of the +16V rail so this way it will still function if the PCB is clipped to operate in a standard 500 series rack. The relay will be a TQ2-12V. Cheap and reliable.
Cheers all, Jeff
![[silent:arts]](https://cdn.imagearchive.com/groupdiy/data/avatars/m/0/172.jpg?1620371656){kind=avatar}
![Electronics Soldering Iron Kit, [Upgraded] Soldering Iron 110V 90W LCD Digital Portable Soldering Kit 180-480℃(356-896℉), Welding Tool with ON/OFF Switch, Auto-sleep, Thermostatic Design](https://m.media-amazon.com/images/I/41gRDnlyfJS._SL500_.jpg)
