Parallel amp connection to speakers, SS + tube

porkchop61 · 29th December 2010, 12:27 PM

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

indianajo · 29th December 2010, 01:24 PM

Yes, the tube device would damage the receiver . Use a speaker selector box in reverse. Make sure you have a light permanent load on the tube device to keep the output voltage from going too high if you turn it on with speakers disconnected.

kevinkr · 29th December 2010, 02:00 PM

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.

Pano · 29th December 2010, 03:09 PM

Right. And beware the Radio Shack speaker switch boxes as they have a common ground.

porkchop61 · 30th December 2010, 01:29 PM

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

At least I didn't cook my expensive Yamaha HT receiver!

Have a good new years everyone.
Glenn

hidnplayr · 30th December 2010, 01:51 PM

I'd use a relay (with 4 switching contacts), switched by the power supply of your tube amp.

porkchop61 · 31st December 2010, 01:05 PM

That's a good idea!
That way it's automatic

Thanks!

Happy new year!

john65b · 02:02 PM

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.

Original Burnedfingers · 31st December 2010, 02:00 PM

The Elliott device is not acceptable. The grounds should not be combined to be on the safe side. THis device absolutely couldn't be used with a SS bridged amplifier.

john65b · 02:24 PM

You are correct...do not connect the grounds as shown...

I had my amp grounds switched along with the positive speaker lead - I think I eiether doubled the number of relays, or did not double up the DPDT relay pins. I have to check.

29th December 2010, 12:27 PM	#1
porkchop61 diyAudio Member Join Date: Aug 2004 Location: Mansfield, Connecticut	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 __________________ "Imagination is more important than knowledge"

29th December 2010, 01:24 PM	#2
indianajo diyAudio Member Join Date: Jan 2010 Location: Jeffersonville, Indiana USA	Yes, the tube device would damage the receiver . Use a speaker selector box in reverse. Make sure you have a light permanent load on the tube device to keep the output voltage from going too high if you turn it on with speakers disconnected. __________________ Dynakit ST70, ST120, PAS2,Hammond H182(2 ea),H112,A100,10-82TC,Peavey CS800S,SP2-XT's, T-300 HF Projs, Steinway console, Herald RA88a mixer, Wurlitzer 4500

29th December 2010, 02:00 PM	#3
kevinkr diyAudio Moderator Join Date: Sep 2004 Location: Boston, Massachusetts Blog Entries: 6	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. __________________ www.kta-hifi.net

30th December 2010, 01:29 PM	#5
porkchop61 diyAudio Member Join Date: Aug 2004 Location: Mansfield, Connecticut	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 At least I didn't cook my expensive Yamaha HT receiver! Have a good new years everyone. Glenn __________________ "Imagination is more important than knowledge"

30th December 2010, 01:51 PM	#6
hidnplayr diyAudio Member Join Date: Sep 2008	I'd use a relay (with 4 switching contacts), switched by the power supply of your tube amp. __________________ Real tubes have top-caps

29th December 2010, 03:09 PM	#4
Pano diyAudio Moderator Join Date: Oct 2004 Location: North Carolina Blog Entries: 4	Right. And beware the Radio Shack speaker switch boxes as they have a common ground.

31st December 2010, 01:05 PM	#7
porkchop61 diyAudio Member Join Date: Aug 2004 Location: Mansfield, Connecticut	That's a good idea! That way it's automatic Thanks! Happy new year! __________________ "Imagination is more important than knowledge"

31st December 2010, 01:54 PM	#8
john65b diyAudio Member Join Date: Jan 2005 Location: 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. __________________ "I speak Spanish to God, Italian to Women, French to Men, and German to my Horse" - Charles V Last edited by john65b; 31st December 2010 at 02:02 PM.

31st December 2010, 02:00 PM	#9
Original Burnedfingers diyAudio Member Join Date: Nov 2002	The Elliott device is not acceptable. The grounds should not be combined to be on the safe side. THis device absolutely couldn't be used with a SS bridged amplifier.

31st December 2010, 02:08 PM	#10
john65b diyAudio Member Join Date: Jan 2005 Location: Chicago	You are correct...do not connect the grounds as shown... I had my amp grounds switched along with the positive speaker lead - I think I eiether doubled the number of relays, or did not double up the DPDT relay pins. I have to check. __________________ "I speak Spanish to God, Italian to Women, French to Men, and German to my Horse" - Charles V Last edited by john65b; 31st December 2010 at 02:24 PM.

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