FiveFish Audio Building Blocks

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FAB4300 – Unity BufferAmplifier Module

The FAB4300 Module is a Unity Buffer Amplifier Module, utilizing either a PDIP8 chip, or a Discrete OpAmp.

It has a single-ended input, and a single-ended output. The output of the OpAmp is connected back to it’s inverting input (IN-), while the input signal is applied to the non-inverting input (IN+).  The output of the OpAmp basically follows whatever is the input signal applied to IN+, thus  it’s named a voltage follower.

While the FAB4300 does not offer any amplification to the input signal, it serves a very important function. The input impedance of the FAB4300 Module is very high, meaning that the FAB4300 does not load down the signal source. At the same token, the output impedance of the FAB4300 Module is very low and thus it can drive loads very efficiently without any apparent loss in signal. You can say the FAB4300 acts like an impedance bridging circuit.

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FAB2306 – Balanced Line Receiver

FAB2306 is our Line-Level Balanced Receiver. The FAB2306 uses a THAT 1206-series InGenius balance line receiver chip.  The THAT 1206 uses bootstrapping to raise it’s common-mode input impedance into the meg-ohm range without the noise penalty of using high value resistors. They behave like transformers, able to maintain high CMRR over a wide range of source impedance imbalances, even when fed with an unbalanced signal. But unlike traditional transformers, they offer DC-coupling, low distortion and transparent sound.

The FAB2306 Line Input Module allows you to create gear that works with line-level balanced signals.  There is no need for 48V phantom power, or -20dB padding for this module unlike the FAB2010 Mic Input Module.



3D Rendering of FAB2306 Line Input Module.




How to: Eagle CAD to 3D Rendering Views

Category: Tips
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Today I learned how to create 3D renderings of Eagle Boards.  I’ll share with you how I got this image below.



You’e probably seen this board design, it’s from my last blog posting. It’s a split +/-15V DC/DC Converter power supply, which also accepts our FAB-1248 Plugin module (for 48V DC output).

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FAB1515 – Split Power Supply DC/DC Converter + 48V Module

The DC/DC Converter part I’m planning to use with my FAB1215 module is out of stock, and even if it comes back in stock, the supply quantity is so low… Mouser doesn’t keep a big inventory of this part because they said demand is low. Soooo, I can’t depend on this part being available for my customers, so I decided to roll my own DC/DC converter for +/-15V output.

Making the 12VDC to +15V output was easy, and initial breadboard testing showed it can deliver up to 370mA and more (up to 500mA). But making the 12V to -15V Inverter was a bit more problematic. The best I can squeeze out of it is -150mA, and only at 58% efficiency.  The good news is I think that should be enough for 1 or 2 channels for a V- rail.  The V+ rail will need to power additional LEDs and Relays so I want the V+ to have a higher current rating anyway. So I think we’re good.

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FAB6010 – Potentiometer & Switch Module

Received our FAB6010 PCB prototype. Yes, it’s green soldermask, not the purple ones you usually see in my other FAB modules prototype. But the final color will be RED to go with our FAB color scheme.



I populated one of the boards I received. Since I do not have a Reverse Log Bourns Potentiometer, I just used a Linear 10K pot for this prototype. This means, the controls are “reversed.” When the pot is turned fully clockwise, it’s the MINIMUM setting, and when it’s turned fully counter-clockwise, it’s the MAXIMUM setting.


There are (4) LED-lighted pushbuttons on the board. Resistor values of 3K3 work well with the Green and Blue LED switches, but makes the Yellow LED too bright. I’ll need to replace the resistor with 10K for the Yellow LED to make all the lamps even in brightness.

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