Side Project: Stereo Accurate Inverse RIAA from HIFISonix - Build

19.04.17 03:11 PM By skrodahl

Here's the finished Inverse RIAA. I haven't done extensive testing yet, but it works as promised AND it measures exactly the same on both channels. I'm really happy with the result.

Get the gerbers for this project here:

Accurate Inverse RIAA completed

If it's going to be called accurate, you'd better get two identical channels. Here's how the invRIAA fares:

invRIAA Frequency Response - Both Channels

In order to construct this board, I built the vacuum pickup tool:

Vacuum pickup tool pump
Fish tank pump and tubing
Syrringe for vacuum pickup tool
A 3 mm hole in the syringe works really well
Sealing the vacuum pickup tool
Some silicone sealant to make the pickup tool airtight

The lead free paste was applied using a stencil, which is extremely convenient. To do the actual soldering, I used this reflow heater bought cheap on eBay (Nope, I don't have space for a reflow oven...). The only negative with this heater is that the LCD back light is more on the front, so you need to tilt it to see what it says.

SMD reflow heat gun bought on eBay
SMD reflow heat gun bought on eBay

You really don't want to go with a normal heat gun for this. They push about 600 liters of air per minute, which will blow away all the components. This one does about 30 liters/minute, and it's adjustable both on the tool itself and by replacing the nozzles.

I even bought an Atmega based transistor tester as a kit, and it contained three SMD components. Here's how that turned out:

Close-up of SMD components on the transistor tester kit
Full view of the transistor tester