Hi guys,
Since I have ordered prototype PCB’s and finalized the artwork, I figured I would share what I have been working on as of late.
This is the Rev B version of the VP312DI that I started a few months ago. I think I first mentioned it on the HiZ Plug-In thread that [silent:arts] and I have been working on. That thread is here, BTW.
My original Rev A design was HiZ Direct Inject into the input transformer only. I wanted to be definitely different than a 512c or BAE’s version, which are HiZ into the DOA.
My brother Mike happens to be a bass player. Not an average player but a phenomenal player. He is also a tone freak. He has been on the “perfect tone” search for all of our lives. In his distaste for any bass amp he has tried, I told him to pick up a couple hundred watt power amp and take my TAB V71 home for a few days. He was amazed by what a great, pure sound this gave him. I proceeded to whip up a quick Bo Hansen DI, built on one of my old, stripped “build it like a 312” VP25 boards. After using this DI for a few minutes, he said he had no use for the TAB V71 and asked how much I needed for the 312 Frankenstein DI. This was done around the time I received my VP312DI Rev A proto boards.
So, next he took my VP312DI Rev A board home along with a few DOA’s. For HiZ Plug-Ins he had a Jensen passive, Pikatron passive, IC active (OPA2604) and Peter Purpose’ FET version. After a week or so of playing with both preamps and many combo’s of DOA’s and HiZ Plug-In’s…Mike told me that he wanted all the options in one preamp. He thought it would be a total mistake to not have Bo’s circuit as an option. So, the Rev B version was born.
Mike currently has multiple basses and used them all in these tests. His current favorite is a Spector that was originally custom made for Tom Hamilton. He also used his pair of Stambaugh Twins along with about 6 others. Yes, he has a problem.
OK, enough yakking. Here’s the run down.
-Basically, it’s the same mic pre circuit as the VP312. I have added a post DOA Elna coupling cap along with a Wima bypass. This can all be user bypassed with a .1" shunt-jumper on the PCB (for standard 312 circuit). I have found significant DC offset from the DOA depending upon which brand of DOA is being used, especially in Bo Mode. The Mute switch is not very quiet this way and we don't want to harm the 2503. This was very apparent when using as a bass amp front end.
-1/4" HiZ jack is auto-switching with a DPDT relay when a plug is inserted. For this I am using a little vertical relay PCB that can be soldered or with a .1” socket.
-Default DI mode is myself and Volker’s Plug-In HiZ PCB. This signal takes the same path as a microphone, thru the input transformer. This means the normal mic input pad will also be available for use while in HiZ Plug-In mode. It will be -15db on this one in lieu of the standard –20db. Volker and I have decided to not alter any of the HiZ circuits from Dan, Peter, Fabio and so on. Some have more gain than others so the pad may be needed on some occasions. The operating voltage for the HiZ Plug-In is switchable between 16V and 24V. A 51x rack will be required for 24V operation.
-I am using 3 NKK G-Series Ultra Miniature Toggles to not only select Bo Mode but also select a few options that go with Bo Mode. This took me a little time to find the right toggles and engineer all of this to fit/work properly. I was highly inspired by Peter Lazaro’s brilliant use of the mini toggles as he did for his EQN project. So, thanks Peter!
-The top of the 3 ultra mini toggles is "Post 2622". Flipping this switch activates the 2nd plug-in relay. Activating this relay is only possible if a 1/4" plug is inserted. HiZ signal is then routed thru Bo Hansen's popular DI circuit. This is Post 2622 or directly into the DOA. Relay control signal is taken from the DI jacks ring when a 1/4" plug normals the ground signal from sleeve to ring.
-The middle ultra mini is Bo's -10db DI pad that is only active if the top switch is in Post 2622 mode.
-The bottom ultra mini is only active if the above 2 have been switched to the right. It was found by accident like a lot of cool things. It creates a Low Pass Filter that mimics the "perfect Jaco Pastorius tone", according to my brother Mike. He loves it so I figure other bass players will find it useful as well. Plus, it's pretty unique on a pre like this.
Sorry for the long drawn out explanation. I get carried away.
Here are some pics and stuff.
Faceplate artwork pdf
Gerber file screenshot of all 3 boards
Close up of DI board with Bo’s circuit
Mechanical details on how the 3 boards connect pdf
Plug-In Relay PCB front and back
Final (hopefully!) proto boards are due in here June 7th.
Regards, Jeff
Since I have ordered prototype PCB’s and finalized the artwork, I figured I would share what I have been working on as of late.
This is the Rev B version of the VP312DI that I started a few months ago. I think I first mentioned it on the HiZ Plug-In thread that [silent:arts] and I have been working on. That thread is here, BTW.
My original Rev A design was HiZ Direct Inject into the input transformer only. I wanted to be definitely different than a 512c or BAE’s version, which are HiZ into the DOA.
My brother Mike happens to be a bass player. Not an average player but a phenomenal player. He is also a tone freak. He has been on the “perfect tone” search for all of our lives. In his distaste for any bass amp he has tried, I told him to pick up a couple hundred watt power amp and take my TAB V71 home for a few days. He was amazed by what a great, pure sound this gave him. I proceeded to whip up a quick Bo Hansen DI, built on one of my old, stripped “build it like a 312” VP25 boards. After using this DI for a few minutes, he said he had no use for the TAB V71 and asked how much I needed for the 312 Frankenstein DI. This was done around the time I received my VP312DI Rev A proto boards.
So, next he took my VP312DI Rev A board home along with a few DOA’s. For HiZ Plug-Ins he had a Jensen passive, Pikatron passive, IC active (OPA2604) and Peter Purpose’ FET version. After a week or so of playing with both preamps and many combo’s of DOA’s and HiZ Plug-In’s…Mike told me that he wanted all the options in one preamp. He thought it would be a total mistake to not have Bo’s circuit as an option. So, the Rev B version was born.
Mike currently has multiple basses and used them all in these tests. His current favorite is a Spector that was originally custom made for Tom Hamilton. He also used his pair of Stambaugh Twins along with about 6 others. Yes, he has a problem.
OK, enough yakking. Here’s the run down.
-Basically, it’s the same mic pre circuit as the VP312. I have added a post DOA Elna coupling cap along with a Wima bypass. This can all be user bypassed with a .1" shunt-jumper on the PCB (for standard 312 circuit). I have found significant DC offset from the DOA depending upon which brand of DOA is being used, especially in Bo Mode. The Mute switch is not very quiet this way and we don't want to harm the 2503. This was very apparent when using as a bass amp front end.
-1/4" HiZ jack is auto-switching with a DPDT relay when a plug is inserted. For this I am using a little vertical relay PCB that can be soldered or with a .1” socket.
-Default DI mode is myself and Volker’s Plug-In HiZ PCB. This signal takes the same path as a microphone, thru the input transformer. This means the normal mic input pad will also be available for use while in HiZ Plug-In mode. It will be -15db on this one in lieu of the standard –20db. Volker and I have decided to not alter any of the HiZ circuits from Dan, Peter, Fabio and so on. Some have more gain than others so the pad may be needed on some occasions. The operating voltage for the HiZ Plug-In is switchable between 16V and 24V. A 51x rack will be required for 24V operation.
-I am using 3 NKK G-Series Ultra Miniature Toggles to not only select Bo Mode but also select a few options that go with Bo Mode. This took me a little time to find the right toggles and engineer all of this to fit/work properly. I was highly inspired by Peter Lazaro’s brilliant use of the mini toggles as he did for his EQN project. So, thanks Peter!
-The top of the 3 ultra mini toggles is "Post 2622". Flipping this switch activates the 2nd plug-in relay. Activating this relay is only possible if a 1/4" plug is inserted. HiZ signal is then routed thru Bo Hansen's popular DI circuit. This is Post 2622 or directly into the DOA. Relay control signal is taken from the DI jacks ring when a 1/4" plug normals the ground signal from sleeve to ring.
-The middle ultra mini is Bo's -10db DI pad that is only active if the top switch is in Post 2622 mode.
-The bottom ultra mini is only active if the above 2 have been switched to the right. It was found by accident like a lot of cool things. It creates a Low Pass Filter that mimics the "perfect Jaco Pastorius tone", according to my brother Mike. He loves it so I figure other bass players will find it useful as well. Plus, it's pretty unique on a pre like this.
Sorry for the long drawn out explanation. I get carried away.
Here are some pics and stuff.
Faceplate artwork pdf
Gerber file screenshot of all 3 boards
Close up of DI board with Bo’s circuit
Mechanical details on how the 3 boards connect pdf
Plug-In Relay PCB front and back
Final (hopefully!) proto boards are due in here June 7th.
Regards, Jeff