Any suggestions for noiseless turn-on of hybrid design?

[thoriated]

Hi -

I've almost convinced myself to build my own 6 channel hybrid amplifier for home theater use, not least because I think it's one of the most economical options to get good SQ. I think I may be able to put together six 150 watt channels for not much more than $500-$600, with the approximate breakdown as follows:

$150 for 1500VA toroidal transformer
$100 for heat sinks
$100 for filter caps
$100 for semiconductors, mostly complementary power mosfets
$25 for tubes
$100 for miscellaneous

In the past, I've used transistor output optoisolators to unbias the output devices until the input tubes have warmed up. However, I noticed a slight 'click' with this approach when the amp became active.

I'd be interested in other ideas, aside from using mechanical relays, that is.

Also, with a 1500VA transformer, would NTC thermistors alone provide enough turn on surge limiting, or should I use a delay relay also? I plan to run only about 100,000 uF total give or take filter capacitance with series inductance in a pi configuration for each output stage supply.

Oh, finally, I was wondering if anybody knew a board house that could turn one or two double sided panelized FR4 PCBs for reel cheep from Gerber files for the individual amp modules.

Thanks in advance!

 

[Panelhead]

Hi -


In the past, I've used transistor output optoisolators to unbias the output devices until the input tubes have warmed up. However, I noticed a slight 'click' with this approach when the amp became active.

I'd be interested in other ideas, aside from using mechanical relays, that is.

I really like using a manual mechanical relay. An automatic relay would not do all I can do with a switch and a load resistor.
I use the load resistor side of switch to check biasing, warm up the amp sometimes, and protect the drivers when shutting everything down in a hurry.

George

Also, with a 1500VA transformer, would NTC thermistors alone provide enough turn on surge limiting, or should I use a delay relay also? I plan to run only about 100,000 uF total give or take filter capacitance with series inductance in a pi configuration for each output stage supply.

Oh, finally, I was wondering if anybody knew a board house that could turn one or two double sided panelized FR4 PCBs for reel cheep from Gerber files for the individual amp modules.

Thanks in advance!