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JensRasmussen 3rd October 2003 12:43 PM

About my amps mains connections
Iím building an amp with four channels I one box (For biamping and/or bridging)

For the power supply Iíll be using 2*500 VA torrid transformers. But the question is how to do the mains cabling?

I have a capacitorbank of 240mF that needs to get started when I turn on the amp. This made me think about how you all make the connection on the primary side of your transformers on bigger amps.

I also wonder about what type of switches you use for your mains?

My plan is to have a stand by 12 V inside the box to power a series of relays for the mains and amp output relays. The mains will run thru a series resistor to the primary side of the transformer, and after a second or so this resistor will be shorted out to make the mains be coupled directly to the primary side of the torrid.

Iím making an interface to connect the amp to my B&O preamplifier; this controls power up and muting of the amp. This could also be used to control the amp via some small switches and there by not having to worry about high current switches?

Any comments and ideas are welcome



sss 4th October 2003 10:56 AM

try rod elliots site
project 39- soft start circuit

li_gangyi 4th October 2003 12:11 PM

Essentially it places a few resistors before the trafo and then shorts it out a couple of seconds later using a do have to get a long-life relay though...

sss 4th October 2003 12:50 PM

i your transformers are very bigu can give it some time before shorting it , then the relay will last longer

JensRasmussen 4th October 2003 01:31 PM

Delay for shorting the resistors
Thanks for the info on the ESP page,

I have made a 1Ĺ second delay before the resistors are shorted.

Don't you worry about this stuff when you build amps?


sss 4th October 2003 01:40 PM

i'm using relays too :)

li_gangyi 4th October 2003 01:55 PM

Guess there are no better ways...only a clean relay will do...

peranders 4th October 2003 02:39 PM

You only need 0.1-0-5 s for the delay (a couple of periods) but up to 1 sec is OK. I have around 0.2 sec only for 600 VA transformer. This helps the fuses not blowing.

li_gangyi 4th October 2003 02:45 PM

How about a full revised schematic with all the component values and a simple layout??

JensRasmussen 4th October 2003 03:24 PM

PCB and schmatics
I have a prototype PCB (single sidet) working, will post the final result incl. pictures when I have it.


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