Built it eventually.........

[billb]

Well I'd bench tested my amp1b a year ago but put it on the shelf for various reasons. Here's a couple of images:




As you might notice, it's built into two computer PSU boxes which are screwed together. My toroidal is on the left (the box with its lid on) - you might be able to see the toroidal I used. This was a 23-0-23 (used for rails), 12-0-12 (cooling fan and power light), 0-9 (5v supply). The 23-0-23 is a tad high so I used a diode chain to reduce the rectified voltage to about 30v (seen at back of case mounted on cooling fan). The cooling fan is the original computer PSU one which I probably don't need but it's there anyway - I physically reversed it so that it blows at the amp (better IMO). The amp chip is screwed to a simple heat sink which is screwed to the casing. As the toroidal has three separate windings then the 5v and rail voltages are separetly rectified. The inputs and outputs are via 6.3mm jacks and the input has a dual gang pot to control input level. Hope this is of some use to someone. I'll attempt to contribute to the forum more than I have been lately. Regards.

billb

[krilli]

Thanks for sharing - How's it sound?

[wadoka]

I use old ATX psu cases to house torroids during the testing phase, it never occurred to me that I could bolt two together and build a nice amp out of them.
It gives the benefit the the torroid is fully shielded from the rest of the amp.
I'm going to steal your idea

[billb]

Krilli,
It sounds very clear - I'm impressed. I built it for general interest originally and have no specific use in mind yet. I occasionally play in a band and might use it for foldback although I'd be concerned at it limiting with the peaks you get from live music. I've found it generates a lot of EMI e.g. if I place a portable radio near it, the radio signal dies and I just get white noise (from the radio). The amp is radiating RF from the input and speaker leads it seems. I'm currently investigating this - I've tried filter caps on inputs and outputs but it needs more. Might try "ferrite beads", which absorb RF. I'll post back when I've tried this.

wadoka,
By all means steal my idea - I'm glad to help. I thought the metal casing would limit EMI but , as stated, the input / speaker leads still radiate this it seems.



billb