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Having 2 different preamps to turn on the same amp via 12v trigger

I have a an av pre for home theater and a 2 channel BHK pre for audio. The BHK is used in bypass while using home theater. 
My issue is they share the same amp and I’d like for the amp to trigger on with either pre. The amp doesn’t have line input sensing trigger. 
How can I trigger the amp with either pre ?  
So far I’ve only come up with make my own cable with diodes as to not backfeed to the pre that’s not in use. Wish I can find something off the shelf.  

dahodevil
dahodevil OP
20 posts
 

Thank you. This should work. 

blackbag20
468 posts
 

@imhififan Thank you for the link.

Bob's designs look compelling!!

dahodevil OP
20 posts
 

I had a brain fart. I thought the BHK would be turned off in HT mode. It needs to be on. So that’s the only one that needs to trigger the amps on. DONE. 
thanks 

imhififan's avatar
imhififan
2,205 posts
 

If the connection from the preamp to the power amp is XLR, by using a BobWire XLR1, there is no need to turn ON the BHK for HT.

Connect the BHK to input A, the preamp/preamp to input B, and connect the 12V trigger output 1 of the BobWire XLR1 to the amplifier trigger input, set the mode to Audio sensing.

When BobWire detects an audio signal from the BHK or preamp/pro, it will Issue a 12V trigger to turn on the power amplifier. No HT bypass required.

However, I have just discovered that the BobWire RCA1 cannot be used with the above setup because it lacks the 12V trigger output capability like the XLR1.sad

 

 

dahodevil OP
20 posts
 

Oh. I see. 
I will just use the theater bypass instead of adding something in the signal path. 
The BHK keeps the solid state section on in standby anyway and in HT bypass the tube section is disabled. 
Thank you for the information. This would work if I didn’t have another option. 
david 

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