Hayling Island

Hayling Island

Friday, January 27, 2017

Class B DIY

I thought I would finally get around to building the amps from the bits that I bought a long time ago.

I came across the pages at Elliott Sound Productions a long time ago, and since I am no good at designing analogue electronics beyond an emitter follower or a long-tailed pair, I bought the components. I filed them safely in a box, and forgot about them.

More recently, I thought it would be fun to exercise some layout skills and engage my friends at Itead Studios in creating a small PCB.

So I am sure that Mr Elliott won't mind me showing the results of this small bit of labour. It's his design, just I didn't buy one of his PCBs - I thought it would be fun to try my own. I am going to build five of them, after all - two for the Studio, where the reference monitor is currently running on an ageing Cambridge P60; one as a test amp for the laboratory, and two in bridge mode for a subwoofer project, to drive a Peerless 850140 10 inch driver I bought 17 years ago from Wilmslow Audio. I've been buying little bits and pieces from them for more than 40 years.

Now if only I could lay my hands on the heatsink I put aside for this project when I was young ..


The first prototype board. I couldn't find any BC546A in the lab, but I did find some MPSA42. They're high voltage NPN transistors so they will be fine. The pinout is opposite to BC546A so they are in backwards compared to the silk screen. 

PS: I have a handful of the blank boards left over; if anyone would like one or two, please drop me a line via Google, and we can arrange for them to be sent. 

Saturday, January 7, 2017

Making progress again ..

The Dell machine arrived. After much faffing around trying to get Windows 98SE running on it (it's a pig, it can't find all of the device drivers for the network etc), I decided to go for a simpler solution. I found this FreeDOS thing, which at first sight seemed to be ideal.

So, I downloaded FreeDOS onto a bootable CD, booted the machine with that and created a 2GB (cuz that's how big a normal DOS partition could be) partition.

I then installed Linux on the beast, running dual boot so I could get the machine on the network, and copied over the files from the Fireball server on to the DOS partition. (Linux can write FAT file systems, you know).

I then ran FreeDOS up, so I could try to run LIFUTIL - and was shocked to find it works. Now all I had to do was to find a 720K diskette, format it in LIF format, and then put the right driver for the 1GSa/s card on. I went through all the files, and eventually found that the SYSTEM_0.13 file was the correct one (by a process of hex editing the files and looking for the description string), put that on the disk and moved it over to the HP 16500A front drive.

Wow. We have a working scope.