12 Volt trigger for Krell KSA amplifier.....


I have a Krell KSA 250 amplifier in my system and it is the only amp in my system with which does not have 12 volt trigger to turn it on. Does anyone know if it would be possible to convert the power switch to have a 12 volt trigger attached somehow to it? And yes I am that lazy that I don’t feel like turning it on every time I want to listen to it…. :-) Let me know your thoughts on this and thanks in advance!

Mello
ectomorph81
How good are your DIY skills ? I have a couple of solutions for you, but they involve some amount of DIY. The simplest is a relay with 12VDC coil and contacts rated 20-30A @ 120V. The relay coil can be driven by a 12V wall wart, plugged into a switched outlet.

You will need an RC snubber across the relay contacts to suppress arcing each time they switch current. This arcing, if not suppressed, will eventually destroy the contacts.

You will also need a reverse-biased diode across the coil, to suppress back EMF that occurs each time the controlling voltage is cut. This EMF can be damaging to any sold state device in the wall wart, such as a voltage regulator.

The other option is the same type relay, controlled by an IR receiver chip like the TinyIR2 kit by Tauntek.com (URL below). The TinyIR2 can be taught any IR remote code. It cannot drive a relay by itself, so you will need a relay driver circuit in-between. You will also need a 12VDC source for the TinyIR2 and relay driver circuit. A 12V wall wart with enough current rating to operate the TinyIR2 and relay coil (probably 100-300mA) should be adequate.

I have DIYed these options and they work fine. Paste the following URL into your browser to see a recent post on the same topic.

http://www.avsforum.com/avs-vb/showpost.php?p=15938148&postcount=5

http://www.tauntek.com/tinyir2-learning-ir-remote-control-receiver.htm
First of all Thank you for your reply Gbart!!! And I am all about DYI projects but am having some troubles finding some of the parts described above? I think I may have found something that will work for the relays but would like to run it past you to double check my findings...

Here is the 12VDC coils I found:

http://www.rvparts.com/product-12-100530

http://www.spadepot.com/shop/Relay-DPDT-30A-12VDC-Coil--P8366C233.aspx

As far as the RC snubber or reverse-biased diode I could not seem to find a single site that had anything describing these parts. The wall wart which I'm sure I already have one that will work. Please let me know where I might look for the RC snubber or reverse-biased diode and if the listed above relays will work? Thanks again for your help!

Mello
All of the parts you need can be obtained from Digi-Key. YMake sure that you connect the diode properly -- i.e., cathode to the positive output side of the wall wart.

30A 120V DPDT relay:
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=Z269-ND

0.1uf 275V X rated cap:
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=399-5426-ND

100 ohm 1/2 watt resistor:
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=100H-ND

1N4007 diode:
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=1N4007DICT-ND