Decibel Dungeon

The power amps.

I currently use a pair of highly modified A&R (Arcam) A60 amplifiers in my active system. They were good amps in their time and with some modifications perform well even by today's standards. However, it may be difficult for others to find a pair of these amplifiers, especially if not resident in the UK. For that reason I have decided to suggest a few alternatives for the Decibel Dungeon Project which should be reasonably easy to obtain.
Two of the options I am going to suggest come from Australia. The first can be found on Rod Elliott's excellent ESP site and is listed as his Project 03A. Anyone who has regularly been to the ESP site will know that it's content is the result of many years of Rod's experience with building hi-fi. For that reason, I have no hesitation in recommending one of his amplifier designs for this project. Most importantly, Rod supplies PCB's for the amps at a very reasonable price (under AU$30) and then backs up this service with help on building the amps. The design has been around for quite a long time indicating that it must work well. It also means that there has been plenty of time to iron out any problems and to optimise the design. The design also adheres to this projects philosophy, ie it is a simple design, relatively easy to understand and can be built at reasonable cost.
My second recommendation can be seen at the Audio Kitsets site and is known as the AKSA amplifier. This amp seems to have been developed over a length of time by someone who loves the music as much as the electronics. Apart from being available in kit form, you can purchase it in various stages of completion, making it a suitable option for those with less confidence in building everything for themselves. Once again, the simple design and reasonable cost fit in well with the rest of the items in the project. You can also find details of the AKSA at ESP.
Another option is the one supplied by White Noise in Scotland. Again, I favour this source because the supplier offers plenty of knowlegeable help and also gives you the choice of how much work you want to do yourself. Choose from buying a PCB, a kit or a built module. White Noise can also offer help with finishing the amplifier like adding a power supply and 'speaker protection.
And for those of you who want to build your own amplifier but don't want to get out the soldering iron, Avondale Audio offer you the chance to do just that. Yes, it's true, no soldering, you just 'plug' everything together.
One of the obvious solutions for active speaker amplification, for reasons of economy and ease of construction, is the chip amp, or Gainclone. Find out all about them here.
Which option you go for (if any) is up to you. I would like to build all of these amps and provide full details here on Decibel Dungeon but do not have the time, energy or funds to do so at present. The reason that I have suggested these power amp options is that I am fully satisfied that anybody building one can get adequate assistance and support from the supplier.
So what exactly is involved in producing the four channels of amplification needed for this active system? Apart from the actual amplifier, you will need power supplies, and cases to put everything in. There will be extras to buy like heatsinks and loudspeaker terminals. And I also recommend adding some form of 'speaker protection. The Velleamn 'speaker protection module is widely available as a kit, while White Noise offer it ready-built.
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Power amp power supplies.

The importance of a good power supply for any piece of hi-fi should never be underestimated and power amplifiers are no exception. Both Rod Elliott and the folks at Audio Kitsets offer a lot of advice and information on power supplies to go with their amplifiers. Rod Elliott offers a design for a suitable power supply (Project 04) which you can read about HERE. You can read my thoughts on power supply components HERE. I'm not going to repeat what is covered elsewhere but will say that I strongly agree with using completely separate supplies for each channel and housing them separately from the amplifiers.
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Putting it all together.

Please read the 'Building your own electronics' section prior to building your amplifiers. As regards housing the amplifiers, take a look at the section on casework. I suggest using a standard sized hi-fi case to house a pair of single channel power amps and another to house their power supplies. There is no reason why you should not be able to produce something that looks as good as it sounds. You will need an umbilical to connect the power supplies to the amps and I have already covered what is involved in my article on the preamp wiring.
I'll leave the choice of 'speaker terminals up to you. A look through the Farnell catalogue will reveal a choice of binding posts and plug/socket combinations, none of which is prohibitively expensive so indulge yourself with whatever you like the look of. I'm sure there are those who will swear that one type sounds better than another but I have better things to do with my life than try them all.
Be guided by the supplier of your amplifier design as to the correct heatsink to use. Don't take any chances by skimping on this item. It needs to be big enough to stop your amplifier overheating or all your hard work and expense could literally go up in smoke.
I do recommend some sort of 'speaker protection and use units built from Velleman V4700 kits. These are available in the UK from Maplins (code# VE24B) for under 15UKP. One kit will protect two channels from DC and any switch-on thumps. Other 'speaker protection kits are available from suppliers like Quasar Electronics. By the time you have got this far with the Decibel Dungeon project, building these protection modules will seem a doddle. If you wish to go the complete DIY route with 'speaker protection, Rod Elliott covers the subject thoroughly on his ESP site.
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