Saturday 14 November 2020

Building the Per-Anders Sjöström QSXM2

I don't always just build my own toys. When other designers make really beautiful kit, I buy their PCBs and go to town.

Such is the case with a few of Per-Anders' designs. He and I share a common design rationalle, which can best be summed up as "components are cheap, if more of them makes it perform better, go for it!".

A perfect example is the QSXM2 phono preamp. Something like 200 resistors, 110 transistors, around 100 caps. It's really not mucking around. It's a preamp that leaves no stone unturned in the search for performance. I'm keen to see if I can improve on the basic phono pre in my NAD3240PE, and this one looks like a very good candidate. I've built some othe Per-Anders designs (mainly head-amps), and have been very impressed.

So I ordered a PCB from his website, downloaded the design doco, and started work:

I've set my work area up with a nice new A2 cutting mat, which protects it from the soldering iron and scratches. There's no need for the microscope for this guy, as it's all through-hole.

So far I've done all the resistors (I had comprehensive stocks, which will now need to be replenished), and I'm on to the caps, many of which I'll have to order in.

I'm looking forward to trying it out!


peranders said...

I notice a HP calculator in the picture. Is it a HP15C? Personally I have a HP25, HP15C and a HP42C. Cheers Per-Anders

Suzy said...

It is! I am unable to use “normal” calculators. I actually have 2 15Cs. I used to have a 15C, a 32Sii, and a 48G (which got me through uni). When my 32Sii died about ten years ago I bought a second 15C. The new one is a much newer calculator, and has a much worse keypad than the old one.

Unknown said...

Is it already running? I just finished my PA03 today, what a great amp. Also build the QRV08 headphone amp last year. Really a high-end little amp.

Suzy said...

No, it’s one I spend some time on every few weeks. Thus far I’ve done resistors, most of the capacitors, and the transistors. Each time I work on it I find more stuff that I dont have in stock, so it goes in the next order.

Neat Ripple said...

Looks interesting. Can't wait for the next update. I'm building my first phono preamp, Wyn Palmer's MC/MM with Warp filter.