Tag: SMD

Hybrid mu-follower boards in SMD

I’ve been using these boards for many years now. Haven’t offered them as is required for anyone to be experienced well enough in SMD soldering to get these done effectively. I have a reflow oven so work at scale is easier this way. I’ve been doing a lot of SMD board design and building over the past few years though.

On a busy time regardless, I found the space to build these four commissioned boards for D3a drivers like the ones I used on my 300B amplifier. There seems to be a lot of interest and build work done around this design, so happy to see this happening.

Hybrid mu-follower SMD boards
Hybrid-mu follower board

3 versions of the gyrator board

Three hybrid mu-follower (aka gyrator) board generations

From left to right: 1) Standard Rev08 PCB with full flexibility of FET and TH components. 2) Rev 1.0s board with SMD except Rmu, protection drain resistor and LED as well as space for any nice big PIO capacitor. 3) the smallest version of all, all SMD except Rmu, film cap and standard TO-220 top FET and multiturn trimmer.

Very happy with the results in the board development. It does take more time and precision (you will need a microscope) to work with the MELF resistors and the SMD components in general. However, it’s worth the trouble if you’re looking to reduce the footprint.

Mini Hybrid Mu-follower board test

 I had a  go first at a mini-gyrator board using SMD. Blimey, it’s hard work to get all these crammed into such a small footprint.
I did a quick test with a D3a and worked fine at 100V/10mA (low voltage of course). It was +35dB flat up until a couple of Mhz. Even the over-current LED works!
Footprint is as small as you can get: 45mm x 25mm 🙂
More to report later!