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For Sale 1073 style preamp boards

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Potato Cakes

Well-known member
Joined
Jul 1, 2014
Messages
2,313
Location
Nashville, TN
Hello, Everyone,

I have been working on a 1073/1290 style preamp board for my own studio for a couple of years now and finally had a first batch made. However it has a couple of errors and doesn't fully function how I intended so I am having to do a Rev B. The preamp does work perfectly if two traces are cut and a resistor and cap are added. It has a fixed HPF, polarity, 48V, and impedance select all built on the board it self. It also has a -inf to +6 fader, which can be omitted if desired. Boards are 8" x 3.3" which 8 channels can fit in a 2U case with an external power supply. Large heatsinks are accommodated as this can be run on +48V/0V, which makes typical heatsinks for this circuit run very hot. I had originally designed this to be powered by a +/-24V supply and this board still can be but there are a couple more considerations that must be taken into account to do so. If using a bipolar power supply there is an on board negative voltage regulator to forward bias the circuit. Either an Ed Anderson 10468 or a Carnhill VTB9045M can be mounted directly to the board. Fiber optic push button caps used for the LED indicators for each of the switches. All of the LEDs are red. Also has an insert point to add a compressor, EQ, etc if so desired. Gain is set 0-65.

Potentiometer shown in photo is a State Electronics Series 88. Other dual gang pots can be used but will more than likely have to be wired off board.

I was going to toss out this whole lot but since I did build a couple of these boards and know that it and does work with a couple of minor alterations, I decided to offer them here as it is an easy way to build this great sounding circuit with minimal off board wiring.

$17 per board and that includes PP and shipping to lower 48. This will be only time I offer these as the Rev B boards will be for my own studio use and clients.

Thanks!

Paul

EDIT: Forward biasing has to be done off board with these Rev A PCBs. Also for clarification the on board metering circuit does not work. This is part of the "does not fully function as I intended" sentence above. The preamp does still work perfectly with the previously mentioned minor alterations. Metering is not part of the preamp audio path and is not needed for the preamp work.
 

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No one? I'll hold on to these for another month then probably toss them. I don't have a need for them but they are worth more than free.
 
Hello, Everyone,

I have been working on a 1073/1290 style preamp board for my own studio for a couple of years now and finally had a first batch made. However it has a couple of errors and doesn't fully function how I intended so I am having to do a Rev B. The preamp does work perfectly if two traces are cut and a resistor and cap are added. It has a fixed HPF, polarity, 48V, and impedance select all built on the board it self. It also has a -inf to +6 fader, which can be omitted if desired. Boards are 8" x 3.3" which 8 channels can fit in a 2U case with an external power supply. Large heatsinks are accommodated as this can be run on +48V/0V, which makes typical heatsinks for this circuit run very hot. I had originally designed this to be powered by a +/-24V supply and this board still can be but there are a couple more considerations that must be taken into account to do so. If using a bipolar power supply there is an on board negative voltage regulator to forward bias the circuit. Either an Ed Anderson 10468 or a Carnhill VTB9045M can be mounted directly to the board. Fiber optic push button caps used for the LED indicators for each of the switches. All of the LEDs are red. Also has an insert point to add a compressor, EQ, etc if so desired. Gain is set 0-65.

Potentiometer shown in photo is a State Electronics Series 88. Other dual gang pots can be used but will more than likely have to be wired off board.

I was going to toss out this whole lot but since I did build a couple of these boards and know that it and does work with a couple of minor alterations, I decided to offer them here as it is an easy way to build this great sounding circuit with minimal off board wiring.

$17 per board and that includes PP and shipping to lower 48. This will be only time I offer these as the Rev B boards will be for my own studio use and clients.

Thanks!

Paul
Who makes the heatsink on the 2N3055 transistor? Do you know the Model Number? How many Watts can it dissipate? THANKS!!!

/
 
You can use a myriad of heat sinks for the TO-3/TO-204-2. The foot print on the board is for this:

https://www.mouser.com/ProductDetail/Aavid/568303B00000G?qs=Qe1jOhZwee1DC9XmF4sw%2BA==
Its thermal resistance is 5.3C/W, which is the best performance I could find in a heat sink that would still fit in a rack for a multi channel preamp. Any heat sink that is used in any of the other wonderful Class-A Neve style preamps will also work. I chose to accommodate a large heat sink on this board to give options on how to power it. The circuit can handle up to 48V/0V or +24V/-24V. When using the single source higher option, 2N3055 runs hotter than normal with the more common size heat sinks used in this circuit configuration. When running on a bipolar power supply, it runs much cooler and the massive heat sink isn't necessary, though I still use them just so I don't ever have to think about it overheating while being used over a long period of time.

Thanks!

Paul
 
Is this board populated? If so, I'm sending more $$ for the one I got. No need to respond, I'll figure it out.
 
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