class A amp project for Mark

[Ian Mackenzie]

I am not sure if this is the right forums (not Lansing diy) but here is a link to a project I am helping build with Mark (pasadena)

http://www.diyaudio.com/forums/showt...0&pagenumber=1

Most of the technical stuff will no doubt be boring for you guys so I will post a few pics as well

The amp is rated at 100 watts rms nominal into 8 ohms per mono block.

This design is a diy version of the AX Passlabs amp series and uses the Pass Labs Super Symmetry and Aleph current source patents. This is a diy exercise so there is no infringment of the patent.

It is intended that this amp will ultimately be used to drive a set of XPL200's in biamp mode.

To start with there are some concept images.

[Ian Mackenzie]

I decided on a square box for weight reduction and structural integrity. The square design also avoids the large rectangular box typical of this type of amp.

It measures about 260mm cubed or there abouts. The heatsinks are 100mm x 150 mm x 44 mm and are rated at 0.61 c / watt each. In use the amp will idle at about 45c in at an ambient temperature of 25c and draw about 250 watts off the mains

The transformer was specially made and is rated at over 625Va and has two 21 volt secondaries rate at 11.9 amps

This is over 264,000 uf (12 x 22,000 50 volt Panasonic) of filter capacitors used in a CRCRC smoothed DC supply.

There will be 16 IRF240 power fets per channel, in use each fet is biased to about 0.7 of an amp for a total of about 5.6 amps of bias.

I must say what seemed like a neat idea has turned out rather complex and a long job in the making. Numerous tools and jig and been either purchased or made for this type of fabrication.

The material is aluminium sheet (4mm angle), 3mm & 4mm plate and bar stock size of 12 x 20mm and lots and lots of drilled and tapped M4 and M3 holes.

[Ian Mackenzie]

Here is the control pcb and associated mounting hardware.

Also some images of the pcb etching process, the powersupply simulation... and construction in progress.

Questions from interested posters welcome.

Ian

[Uncle Paul]

Ian,
This is fascinating stuff for me. As always, you planning and execution is first class.

I'm planning a bi or tri amped 4344 inspired DIY using the MOX crossover and Aleph amps. Not sure if the LF amp will be Aleph, or if I want to use a different class there.

I'd go 4345, but have to unfortunately compromize due to size. Cabinet drawings are finished, parts are sourced, and construction has begun.

Electronics are phase 2 of the project. I have enough amps and crossovers to keep them playing while I complete the DIY electronics.

I've been pouring though the threads (including yours) in the Pass Labs forum at DIYaudio trying to make sense out of all the various versions and variants to determine which is/are the best for my application. It seems that the Aleph X, though 5 years old, is still pretty tough to beat. I'd appreciate any input you have on this.

I plan on integrating the crossovers into the amp pcbs to reduce the number of cross connects and related woes.

I learn something new everytime I read one of your posts, here or there.

Thanks,
Paul

[Ian Mackenzie]

Hi Paul,

Enjoy your loudspeaker project.

The Mox sounds like a good plan if you are going the Aleph route.

It always brings out the most natural sound.

I will be incorporating a Mox in a Pass diy preamp as a followup to this project.

The std Aleph is a nice choice and is easier to build.

They have a more romantic presentation and work well with JBL's.

The X Aleph brings excitement and revelation from the energy and spatial detail in the presentation

Because of size and heat issues consider one of the better class A/B amps for the woofer.

If you are going diy have a look at the SKA GB 300 for the woofers or one the Anthony Holton aussiamps. Some of the class D amps are also interesting.

Ian

[Guido]

The std Aleph is a nice choice and is easier to build.
They have a more romantic presentation and work well with JBL's.
Ian

Yes, Yes and Yes!!!