strapping two amps

Hi Guys -
I hear people throw around this practice of strapping amps.

I vaguely understand that they are talking about connecting two amps and sending the output through one or both of the amps?

I'm confused -- how do you do this?

let's say I have two small 2 channel amp... how would I "strap" them? My goal is to take 8 wpc amps and strap them to get 16 wpc.

Is this doable?

Thanks,
Reed

I seem to have stumped everyone...

could you take two of these 8 wpc tube receivers

http://s5electronics.com/tube.html

and "strap" them together to get 16 wpc?

:scratch2:

"Strapping" refers to putting the amps into mono mode, if they are stereo amps to begin with. I have a Bedini 150/150 amp, 150 w/ch. If I strapped it, it would turn it into a mono amp of about 300 watts or so.

So they would have to have a switch that turns them into mono blocks - or do you change the wiring, capacitors, etc?

One mono signal is routed to both inputs with one of those inuts switched to be out-of-phase. Then the two positive speaker outputs are used as the output terminals. The amp must be designed from the factory to do this.

Keep in mind, doubling the power only produces a 3db increase in volume. It takes ten times the power to double the volume.

Strapping a tube amp will require a different approach than from solid state.

Here's what you'll be doing:

You'll connect the outputs from the 2 tube channels in parallel - both ground and the 8 ohm taps.

Then you'll route the input signal from your preamp to both channels. Use some sort of a Y adapter to do this.

Next, connect your 2 speaker wires to the ground and the 8 phm taps that you just connected in parallel.

With your 8wpc amp, I'd recommend you contact the vendor to confirm this arrangement. This is how McIntosh and Harmon-Kardon documented their tube amps.

Lastly, and this may well be the kicker for you: With this arrangement and with only an 8 and 4 ohm tap available to you, you'll get your best speaker matching using speakers with a nominal 4 ohm rating. Yep, this means that your normal 8 ohm-rated speakers may not sound as good as they might if operated as a single channel. Technically, this is because the strapping arrangement effectively changes the output impedance of the amps when put in parallel. You'd need a 16 ohm tap to match the 8 ohm speaker impedance.

Bottom line with your amps: Don't bother. Upgrade the amps if you need more power - or get some 4 ohm speakers.

Hope that helps.

Cheers,

David