• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Parallel amp connection to speakers, SS + tube

Hi all-
I want to connect my DIY KT-88 SE amp to my Klipsch KG-4's that are in my HT setup in parallel with my SS Yamaha HT receiver. Will this damage either device? I'd only be using one at a time. The other option is some sort of amplifier selector switch box, kind of like a speaker selector box in reverse.
Anyone have a similar situation where the use different amps on one set of speakers?

Glenn
 

kevinkr

Administrator
Paid Member
Back in the day I regularly repaired the consequences of connecting tube and solid state amplifiers in parallel under the proposed usage conditions. The solid state amplifier always lost resulting in blown output devices.

Indianajo has it right, you must use a switch, and as he says it would be a good idea to assure that there is always a light load on the tube amplifier. I think a 100 ohm 1W resistor would be adequate in most cases unless exceedingly careless. (At your own risk)

Make very sure that no amp output grounds are common inside the switch either - it would be best to use a DPDT switch and switch both sides of the speaker load - prevents ground loops, and in the case of a BTL output on a receiver (IMHO probably not that common) would prevent the destruction of the receiver's output stage. It would be best to build your own.
 
Thanks guys, glad I asked!
Time to build an "Amplifier selector box" I like the idea of putting loading resistors in the circuit.
Of course I asked this question because I didn't want to keep switching speaker wires manually every time I wanted to use a different amplifier due to laziness, now I have to build a switch box, oh well :D
At least I didn't cook my expensive Yamaha HT receiver!

Have a good new years everyone.
Glenn
 

john65b

Member
Paid Member
2005-01-09 2:32 am
Chicago
Kinda off topic, but still relevant -

I built an A-B Test Switch from Elliott Sound Products to switch (online) two amps on a single speaker set - all from my comfortable seating position. The Switch Box has Relays to properly switch the speaker leads from one amp to the other.

A-B Box For Amplifier Comparisons

BTW - you would be surprised how close amps can really sound...that time to unhook/reconnect an amp really can sway an opinion...

This thing has saved me gobs of money chasing the "Best" amp.
 
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To the OP - If your AV processor/amp has PRE-OUTS you could hook up the tube amp to your front right and front left outputs and usually there will be an option on the HT unit to listen straight analog bypassing all the stuff inside for HT sound processing. Just an idea no one mentioned yet.

Cheers,

Bob