Scratch Build – In Progress Pi-Amp Bi-Amp (Update - Completed!)

I started building amplifiers several years ago and PC's several years prior to that. My interest has been combining the amplifier and PC into one chassis to create the Pi-Amp (PC Integrated Amplifier).

This job will chronicle building the bi-amp version.

Bi-amping is the process of splitting a line level audio signal into a bass and treble component, using an active crossover, and amplifying the resulting line level signals (four signals in the case of stereo).

The alternative to bi-amping is splitting the amplified signal into bass and treble component, in the loud speaker enclosure, using a passive crossover.

Bi-amping greatly improves fidelity because passive crossovers present the amplifier output with varying impedance due to the presence of the inductor.

Below is a concept drawing. The overall dimensions of the chassis are 18" W x 11" H x 16 1/2" D. Slightly wider than the standard audio enclosure. The chassis is designed for optimal placement of PC and amp components to prevent problems with heat and electro magnetic interference.



I began the construction by cutting all of the chassis components from a single sheet of aluminum, 5052, 2' x 3' x 1/8" and a stick of aluminum angle 3/4" x 3/4" x 1/8" x 8'.

The plate and angle were cut using a table saw and a carbide tipped, non ferrous blade. The 1/4" wide ventilation slots were milled with a plunge router and spiral "o" flute carbide bit.



The next step will be drilling about 60 holes and assembling the chassis using machine screws (most of them counter sunk).

 

Sounds awesome.

Or it will sound awesome.

 

Pi-Amp Bi-Amp

Ah ... you're from Tejas. I love Texas; lived in Houston for six years, going there next week. I love the food. There are no cooks in Colorado. Might as well eat in Wyoming.

 

Actually I'm from Colorado too. The only 'mountain' in Houston is the city dump. -Although I've seen some buffet-folk who qualify as mountainous...
I really miss bedrock under my feet.

 

Pc and amp combo isnt correct they are two different thongs and shouldnt be combined. There's too much going on in the audio side and the comp side for them to be combined.

Good luck though you might chang my mind!

 

You could take a look at pi-amp dot com to see the basic version. The sound is awesome. By the way, what are "thongs"?

 

Yeah, everyones from Colorado. I do miss the floods in Houston.

 

30 years in Denver suburb Westminster for me. Now I'm elsewhere too.

 

Colorado is a tough place to make a living, especially when the economy is slack.

Test assembly, edges still sharp, ran out of counter sink machine screws, still need to miter those bottom corners.







Weight 17.5 lbs. Looks like a microwave oven. Any ideas how to finish aluminum (I'm just a wood guy). I could buff it to a mirror like finish or run over it with a random orbit sander down to 400 grit for a mat finish or go to the expense of powder coating. Never have had powder coating done before. Any help on this would be great.

Next I will build the drive head, power supply distribution unit, and toroid transformer mounting bracket. The drive head will contain two 3.5" HDD's and one optical drive. The PSDU will contain the reservoir capacitors, fuses and bridge rectifier for the amp side of build.

 

Pi-Amp Bi-Amp (Drive Head Installation)

The drive head is completed. This is the trickiest part of the chassis assembly.



Alignment is critical; things should wind up tight and square.





Th drive head supports two hard disks and one optical drive and serves as a heat sink for the these drives. Note: During initial assembly I do not use washers. The final assembly we be done using nuts with integral locking washers.





The drive head can be quickly removed by backing out the three screws on the front control panel and lifting straight up.



In my previous post I mentioned the PSDU and toroid bracket. These are also complete but I will show them during the power supply installation. That will place them in context.

 

Looks very impressive, and I'm sure it would be even moreso if I knew exactly what you were building lol, I can't say I know a whole lot about amplification and such.

Are there any good sites that I could read up on this sort of thing? I've been wanting to get into it for a while, but I don't really know where to start.

Great looking build though, good finish quality. Keep up the good work!

 

Judging from the picture further up, you must have been in diapers when you started building amps!

This is really cool! Can't wait to see it finished!

 

Pi-Amp Bi-Amp

Thanks, I'm glad you like it. I will try to keep this log speedy (time permitting). You can see the basic version at pi-amp.com (there are lots of links crediting my sources of inspiration). Same concept here, however I will change the layout slightly for weight distribution and use an aluminum case to cut back on the size. A good site for hardcore amp builders is diyaudio.com.

Sorry! I should have elaborated; that is my assistant, he drills all the holes and helps me with fresh ideas.

 

Really good table saw work. 50% of what I make on a table saws are projectiles.
Yes. Tropical Storm Allison was entertaining for a while, Then came the mosquitoes.

 

Pi-Amp Bi-Amp / Chassis Complete

Installed the toroid bracket and PSDU. The PSDU may look a little odd but it will contain five amp power supply components. The mounting brackets are narrow to avoid touching the reservoir capacitors. Real estate is getting scarce!



Just a view from the other side.



Looking at the underside of the chassis cover. The angle brackets are positioned to support the amp fins and rear panel.



Fully assembled, finally got those countersink machine screws. Sanded all pieces (except the angle) with a random orbit sander. Cleaned with mineral spirits. Edges smooth. Yes, you can stand on it.



Cut out access holes for main board I/O and ATX12V power supply. Used a jig saw and finished with a Nicholson.



Nothing fancy on the bottom, a little rough. Chassis is very rigid.



All metal work complete except holes for main board tray, switches and binding posts. Time to go to clean room mode. Next step is installing the main board tray and amp power supplies.

I will not be able to post for at least another week, take care.

 

awesome

 

Pi-Amp Bi-Amp

Installed power supplies for the four amplifiers and active crossover. Powered up and tested fine. Installed the micro ATX main board tray. Test fit main board and expansions cards, no trouble. Test fit ATX12V power supply, good fit.

I'm tired. I forgot how tedious wiring can be.







The next step will be installing the main amplifiers and doing the control wiring.

 

This project is extremely interesting, so here are some suggestions:

1. A "class D" version would be great ! (something like the Woodpc v3);
2. Biamping is great and could be even more interesting - and cheaper - to use a software xover (http://xover.sourceforge.net/ for example);
3. An integrated DAC could enhance fidelity too...
4. Keep in serious consideration to build a 100% fanless PC-section;
5. Smaller size/weight version would be desirable;

Hope that inspires !

 

I really wish I had more of an understanding about amplifiers! The build looks fantastic, wonderfully clean and precise

 

I think this is the forth log entry ... star date ?

Installed four Marshal Leach V4.5 Class B amps (120 Watts RMS each, though I think the toroid transformer, at 370 VA, may not quite deliver; don't need the pain). I purchased the PCB blanks from Dr. Leach and assembled each amp before cutting parts for the chassis.

The functions on the controls panel are fairly basic. I like toggle switches.

Top row, left to right, HDD LED, PC power - boot, PC power LED.
Bottom row, left to right, amp power, bi-amp or 2 channel four speaker stereo selector, master volume, head phone selector, headphone jack.



The small circuit board mounted at the base of the front controls panel is the active crossover. It was designed by Elliot Sound Products, I purchased the PCB blank and assembled with components according to the crossover frequency needed for my speakers.



Scoped each amp to ensure no DC offset, crossover distortion and set low pass and high pass amplitude (I like lots of crisp highs). The small trace is the 30 KHz input and the large trace is 30 KHz output.



The next step is installation of PC components (yep, there's a PC in there; the brains behind the operation).