Running monoblocks in parallel to increase watts??

Is it possible to run monoblock amps in parallel so as to effectively increase their output wattage to each channel?? I have a set of monoblock amps now that are 100 watts per channel, and want to get a second pair of monoblocks so as to maybe have 200 watts per channel. They are tube monoblock amps, so will this effect impedence values etc??

I know this may take a special interconnect and speaker wire or at least the use of a splitter (or adding another set of output rca's on the preamp) to send the preamp signal to the pairs of amps (2 monoblocks for each channel = 4 monoblocks total) for each respective left and right channel. I assume that the output of the amps will have to "tie" together again (like biwire cable) in the run of speaker wire going from the four amps (2 per channel) to the speaker terminals?

If this possible, would I effectively be achieving 200 watts, or only like 150???


It might work if you can invert the signal to one pair of amps. It would take a fully balanced preamp and you would split the balanced out and send pin 2 plus ground to one RCA on one amp and pin 3 and ground to the other RCA of the other amp. You would have to combine the grounds. You would be effectively turning the amps into fully balanced designs. But, I don't know if this will work with your amps and do not recommend trying it.
Blowing up your amps is what will happen.
Yopur chances of doing what you want without destroying them is like 1 in 10,000.
What you want to do is a no-no for ANY kind of amplifier.
Rwwear does point out a possible way, but to do it successfully, you would have to be an electronics engineering guru. If you were, you wouldn't be asking us!!1
If you really HAVE to have more power, just buy twice as big a pair, and sell you 100 watt babies.
However, if your speakers will accommodate it, you could set up a vertical bi-amp. This won't get you 200 wpc but will get you some of the benefits you are seeking.
Two amazing things--people who don't know how to use SEARCH, and others who know NOTHING of which they speak.

RW, inverting inputs and wiring outputs like that is called bridging. I've never known anyone to try it with tubed amps. PARALLELing channels of tubed amps is an old and effective practice, of which I've written many times. The power simply adds--your 100-Watt channels become a 200-Watt amp--into HALF the indicated impedance. If you used the 8-Ohm taps, you now have 200 Watts into 4 Ohms.

To wire it, use a splitter cable to send the identical signal to both inputs and a short chunk of speakercable to combine in parallel the outputs--positive to positive and neutral to neutral.

I've done this with the 2 channels of c-j MV75s and with EAR monoamps. It's a VERY effective way to drive low-impedance loads with tubed amps.

And before someone writes that the power can't be greater because the Voltage is the same as in one channel, just use the next-higher-impedance taps. But even if there aren't, say, 16-Ohm taps to use, the paralleled taps have half the circuits'/transformers' output impedance, so the damping factor is doubled. Then the paralleled 8-Ohm channels are better able to drive that '8-Ohm' speaker that probably dips significantly below 8 Ohms.

Try it, Red, and you also might try SEARCHing next time. :-)
The inversion technique works with transistor amps (and is the way that car stereos get 15 w/channel while running only 12 volts).

That technique is: the load goes between the two '+' outputs. This assumes that the '-' outputs are tied to ground. One amp then uses an inverted signal while the other uses a non-inverted signal.

For tube amps *in general* the + outputs are tied together and the - outputs tie together and the load is between the resulting + and -. The inputs are 'Y'd together.

Power does not always double- with transistor amps and most tube amps it does but there are exceptions- for example with our S-30 the output power goes from 30 watts/ch to 90.

In all cases a loss of delicacy will be observed. This is due to minor variance between the channels. In tube amps this can be reduced by matching tubes in the left and right channels so as to reduce the variance. There is nothing to be done in the case of transistor amps.

You *do* have to be careful! One wrong step and you can quickly toast something!
I see nothing wrong with someone asking us our opinion even if we are not all experts. And I don't claim to be. But is it not correct that bridging is very simular to balanced and is why you have more gain with a truly balanced design.
Bridging is definately balanced. That is why you see bridge-able transistor amps with balanced inputs that only run in balanced mode. But there is no association with greater gain, although it is possible to achieve greater gain with less noise when running balanced.
>>I see nothing wrong with someone asking us our opinion even if we are not all experts<<

OK I'll buy that but are you willing to compensate the inquirer for any problems your "opinion" causes?

In this particular case the potential for serious and/or expensive damage to speakers and amplifiers exist if faulty "opinions" are followed.

I suggest you follow Harry Callahan's advice in the movie Magnum Force:
"Man's gotta know his limitations"
Thanks for the insight and discussion. I think I'll stay with what I got since I am not technically inclined to feel confident in the safety of this application. Lots more too it than I thought.

One of the few problems with AGon is its lack of a stronger more refined search engine. I hope maybe they are working at improving it.

Thanks to everyone for their time and input, especially Ron at Atma-sphere (was it him??) who is busy building amps and working on his own stuff I am sure.

Audiofeil you must not have read my first post. If you did read you didn't comprehend it.