The projects described on these pages are not commercial in any way. This means that we DO NOT sell PCB’s, kits, or anything like that. It also means that any for-profit use of the information on these pages is strictly prohibited. I.e., you can NOT sell PCB’s, kits (neither partial, nor complete) or finished units of the DIY projects on this site, without the express written consent of Gyraf Audio. These pages are information only – but the best and most complete set of information we have been able to come up with.

Please do not contact us regarding parts or info for the DIY-projects, as we don’t sell anything related to these – they’re kept strictly non-commercial.

Here’s the link to the GroupDIY forums – our meeting place and hangout for all things audio, electronic and DIY. Direct your questions there, and check there for possible solutions for errors and strangeness in your DIY-thingys:



• Never work with live voltage switched on. Switch off, discharge, work, connect measuring equipment and power up

• Always keep your mains connector in plain sight when working, so you can assure yourself that it really is disconnected

• If possible, get an extra voltmeter, and keep it connected to the charging capacitator in your tube HT supply. Never touch anything before voltage drops beneath 48V

• Always tidy up your working area before connecting your project to the mains. This gives you some time for second thoughts about what you are doing.


This pages contain information about building your own professional audio equipment.

Comments and corrections are more than welcome, but I can’t promise to reply to all mail. If you build one of the projects and describe the process on your webpage, I’ll be more than happy to add a link here, so others can benefit from your experiences.

Disclaimer: Notice that all information, schematics, layouts etc. are supplied “as is”, and that we can in no way be held responsible for its acurateness, functionality or even safety.

Gyraf Audio shall not be responsible and disclaims all liability for any loss, liability, damage (whether direct or consequential) or expense of any nature whatsoever which may be suffered as a result of or which may be attributable, directly or indirectly, to the use of or reliance upon any information, links or service provided through this website.

Also you should take extreme caution when working with mains voltages and the very high DC voltages ocurring in tube circuits. These voltages are lethal, and the smallest error will be chatastrophic. And we like you to stay alive and well, so you can help other people sharing our bizarre interest for building retro-pro-audio-equipment.

Note that the projects available here – among many other interesting things – are the target for discussions in the GroupDIY forum – dedicated to DIY pro audio:

German speaking sister board,

And a Danish forum for all things DIY:

In these places you can find answers for your DIY questions, by people that have actually tried building some of the projects. Without those guys, these pages would be a whole lot more confusing – their comments and questions has been an invaluable help..

Do-It-Yourself G9 Tube Microphone preamplifier

This is an adaptation of our popular Gyratec-IX microphone preamplifier. Featuring real-tube amplification, Phantom power, High-pass filter and Phase reverse as well as Line, Mic and Instrument inputs. The sound is second to none, but it’s a quite complicated project – not really suitable for first-time builders.

The SSL Mixbus Compressor Clone

This is a somewhat more modern design, a stereo summing compressor for tightening up and gluing together your mixes, cut right out of the heart of the recording industry’s standard mixing board; The SSL4000E. It is relatively easy-to-build (I think, judged from the success-rate I know of), and based on components that shouldn’t be that hard to get anywhere in the world. The circuit for this stereo compressor is amazingly simple for a compressor this well-sounding.

Gyraf Do-It-Yourself 1176LN rev#F

The 1176 is a well-known and classic FET compressor. No tubes, but a nice solid-state do-it-yourself project. It is an adaption of the original UREI 1176 LN to components and parts that are available (mostly) everywhere today. Adaption include changing to standard European transistor types, modernizing component values, using Lundahl transformers, and rotary switches for easier front panel layout.


The most famous of the old-school tube equalizer brigade. Brought to you in a updated design, making it possible to do your own. But be warned – it’s based on High voltages for the tubes, so it’s not a safe first-project.

DIY Tube Microphone

Microphones are not the most usual subject for home-built projects, and when I started this, it was mostly because nobody seemed to belive it could be possible. But possible it is, and with astonishing results. Try for yourself..

Gyraf Do-It-Yourself Calrec PQ1549 EQ

Build your own Calrec PQ1549 Equalizer – Yes, the one found in the Calrec UA8000 “Polar” desk. This EQ is one of my absolute favorites when it comes to equalizer designs based on standard opamps. Give it a shot, and you’ll know what I mean…

Making the PCB: Here’s how to do it

Information about how to process your own PCB’s – for e.g. the projects found on these pages.

And for those of you that are unsure and don’t want to get into “rolling your own” PCB’s already, here’s a couple of ready-made options:

Gustav has a PCB-service for all of these projects, available across the world:
Gustav’s operation named “JustThePCB”

Chef in the UK has G9-diy and GSSL pcb’s also:
AudioKitchen, Chef’s PCB operation

We would like to mention here, that we have absolutely no economic interests in any of the above pcb-operations – as stated above, we do not believe in mixing DIY with business. This is also why these independent operators are selling PCB’s at very decent prices – at least in Europe. This is NOT ment to be a for-profit operation.

Gyraf Audio’s Obscure Schematics

Check out our collection of hard-to-find schematics, Obscure equipment, or just those not-so-common technical drawings. Stuff I needed but didn’t find on the interwebs so far..