Design rules

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The QRO Amplifier built by Per Hägglund, Sweden

Audiophilic statement

There are lot of guys out there who are extreme, weird or crazy, call it what you like. I have a humble attitude towards these guys. It's like a religion, you can't argue about it. Here are some examples: Put a CD in the freezer, peel of plastic covers of capacitors, strong sonic opinions about transistors, opamps, caps, resistors, different diodes in the rectifier bridges etc., etc. You won't believe what I've heard. Most of this stuff are hard to melt. I don't believe in it, most of it anyway. I have very little interest of tweaking unless there are technical reasons, like changing resistors from 5% to 1% and caps from 10% to 2.5% in a phono amp.

My opinions are to use parts which are technically correct at least. OK, I like some components more than others but it's more based on a feeling than facts. I would probably not hear the difference.

I have made the presented designs purely for my own pleasure, not to satisfy anybody else but my myself. I have the word "extreme" here and there. I have it also on my pcb's. My things become extreme only in the listeners ears (or eyes). Make up your own mind here. The strong words are more like an eye catcher when folks find me through search services.

Design statement

  1. Now, when I'm a professional I get a kick of doing timeless designs, which can last for many years without getting hard to build (obsolete parts with no replacement). This is nowadays very important for me.
  2. My second design criteria is repeatability. If 1000 people build one amp, everyone shall succeed if they do exactly as my directions. No trimming or tweaking in order to get it working. I try to avoid trimming and matching, if it's possible.
  3. My third design criteria is to use common ("normal") components, easy to get, high quality industrial parts.
  4. My fourth design criteria is to make the pcb's as universal as possible. I have made room for alternative parts (SMD and hole mounted) and also for different opamps.
  5. My fifth design criteria is to squeeze out everything of possible performance of each part. I don't like to waste performance. I don't fear complex solutions if I feel like it. For me, simplicity is not a virtue.
  6. My sixth design criteria is superior technical performance, such as frequency response, step response, clipping characteristics, temperature stability, protection circuits if necessary.
  7. The seventh design criteria is to deliver first class quality pcb's.

How do they sound?

How do my designs sound? Some people dismiss them right away due to the complexity.....and without having listened to them. Those who really sit down and listen like them. Close your eyes if you don't want to see the misery... I haven't got a single bad review yet.


Not really, because DIY, do-it-yourself means in many cases few parts, cheap low quality pcb's and not necessarily high performance.

My designs are unique because they attract a very special category of people. My stuff is not common DIY.

This is my brand and trademark. I won't make any single sided pcb's with simple solutions in order to get popular.

I have made these designs only for my own pleasure, not to please the big crowd, but since my many years on the net I'm getting more popular so it's moving in the right direction.

Finally I must add that my designs are easy to get working if you only are thorough. If you won't succeed the first time you will get good support from me (will not happen if you'll buy cheap pcb's on Ebay).

Some quotes from customers:

"I haven't bought his amps, but I've used his jsr-03 on two separate occasions, both times he was extremely helpful even above and beyond the call of duty."

"Well, I´ve tried the QRV06 sounds excellent to me. I´ve just started the QRV 08 headphone amp, will take a while though. I think he knows what his doing, P-A Sjöström."

Suzy Jackson about my QRV07 (the same as QRV09) heaphone amp:

"The beginnings of a new amp to drive my Sennheiser HD595 headphones. I was greatly impressed by the TI TPA6120 current mode feedback headphone amp chip, with incredibly low distortion levels. I began designing a board to try one out, but found almost exactly what I was designing had already been done by a Swedish designer, Per-Anders Sjostrom. So I bought a bare board off him. Here's the board mostly assembled, being test-fit in a Hammond extruded aluminium box, with Alps volume pot. I'm extremely impressed by Per-Anders work. This is a beautiful design, with great attention to detail. I couldn't have done better myself.

In use the amp is wonderful. Totally transparent, with no audible noise at all. I haven't wound it up all the way, as I value my hearing too much for that."