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-   -   Any suggestions for noiseless turn-on of hybrid design? (http://www.diyaudio.com/forums/solid-state/23266-any-suggestions-noiseless-turn-hybrid-design.html)

thoriated 26th November 2003 06:35 AM

Any suggestions for noiseless turn-on of hybrid design?
 
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 26th November 2003 10:38 AM

Re: Any suggestions for noiseless turn-on of hybrid design?
 
Quote:

Originally posted by thoriated
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!



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