This idea may be old hat, but I didn't find it in the archives.
I am building (slowly) a Tripath-based amp using a EB-0104A eval board, Jensen input transformers, etc. I am using a 1kVA, 55V toroidal transformer from Avel-Lindberg as the main pwoer transformer. I found some scrap rack-mount cases at work. Since the case is a little tight, and I didn't want to give up power supply capacitance (36000uF for each of the positive and negative supply rails), I had real trouble figuring where to put another transformer (even a small one) for the 5V supply.
Then it hit me! I could wind extra turns on the main toroid. With 120V RMS in, I get 0.69V RMS/turn. Ten turns gives me a nominal 8.6VDC with diode losses, and if I allow for a 25% output drop due to low line or heavy load, this gives me about 6.4VDC or so on the output. I plan to regulate this with an LT1763 low noise, low dropout regulator.
Also, I was thinking about winding the auxiliary winding with coaxial cable. That way I can tie the outer conductor to ground and have an electrostatic shield.
I hope to finish my amp sometime this summer (kids and work keep me quite busy).
Hope this helps someone.
John
I am building (slowly) a Tripath-based amp using a EB-0104A eval board, Jensen input transformers, etc. I am using a 1kVA, 55V toroidal transformer from Avel-Lindberg as the main pwoer transformer. I found some scrap rack-mount cases at work. Since the case is a little tight, and I didn't want to give up power supply capacitance (36000uF for each of the positive and negative supply rails), I had real trouble figuring where to put another transformer (even a small one) for the 5V supply.
Then it hit me! I could wind extra turns on the main toroid. With 120V RMS in, I get 0.69V RMS/turn. Ten turns gives me a nominal 8.6VDC with diode losses, and if I allow for a 25% output drop due to low line or heavy load, this gives me about 6.4VDC or so on the output. I plan to regulate this with an LT1763 low noise, low dropout regulator.
Also, I was thinking about winding the auxiliary winding with coaxial cable. That way I can tie the outer conductor to ground and have an electrostatic shield.
I hope to finish my amp sometime this summer (kids and work keep me quite busy).
Hope this helps someone.
John