Question about paralleling two amplifiers

[thebadtall]

Hello. I have a question.

Lets assume I have 2 identical amplifiers with 36 watt Pmax each.

If i connect both output to 1 typical 200w speaker, is it going to play 72 watts?
or the circuit will damage?

thank you!

 

[mister_rf]

Re: paralleling two amps

Practically, each amplifier must be as closely matched as possible, to create an identical signal as the other amplifier ( in order not to appear as loads to each other).
In practice small resistors must be added in series with each amplifier's output to enable proper current sharing between the amplifiers, without them the amplifiers will fight each other and overheat.
Some examples:

http://www.shine7.com/audio/pa100.htm
http://www.shine7.com/audio/bpa300.htm

 

[thebadtall]

Re: paralleling two amps

ok, for xample if i have 10 amplifier modules , of 30 watt each, and connect em all together with resistances, to 1 mutual speaker, they are going to have a total output close to 300watt?

im asking beacause i have a couple good amplifier schematics with good quality, and would like to drive as many speakers i can, by making many amplifier modules and connecting together.

 

[keith1200rs]

Re: paralleling two amps

I am not sure putting them in parallel with have much effect unless you have a lower impedance load. The power into the load is related to the voltage you apply to it. If you don't increase the voltage you won't increase the current so you won't increase the power. However, if you reduce the load resistance and can get the amplifiers to share the load (by applying small series resistance with identical amplifiers) then you could increase the power.

Another option would be to use a bipolar drive. Drive one amplifier with a signal 180 degrees out of phase and connect the speaker between the two output terminals and connect the grounds together. In theory you will get 4x the power but I suspect that overloading the amplifiers is a possibility (you will be asking them to deliver higher current, much the same as if they were driving a lower impedance load).

Keith.

 

[thebadtall]

Re: paralleling two amps

thank you. in conclusion: no significant difference if paralleling. except if voltage is increased.

 

[keith1200rs]

Re: paralleling two amps

thank you. in conclusion: no significant difference if paralleling. except if voltage is increased.

or load resistance reduced.

Keith

 

[thebadtall]

Re: paralleling two amps


so i increase the voltage from 12v of tda2030's to 18v, having 4 amp modules in parallel, straight to 1 woofer output, without resistors, will work... ?

 

[D.A.(Tony)Stewart]

Re: paralleling two amps

IN the 70's I went to a disco in Hull Que, Canada once that had a rack of 8 Crown DC-300's or 2.4kW total to drive quad speakers. It was a seismic experience.!!

They had two DC-300A's for each port and I do not know for sure how it was arranged. Crown stopped production of the DC-300A in 1985.
Look here for info: **broken link removed** www.harmanpro.com

I have seen current sharing on SMPS of this size also working for redundancy. Instability results if the feedback on each does not have a 10% pre-load to allow some current regulation. But in linear systems you can run in current mode in parallel otherwise you need to match the ESR and phase response vs f for each driver. Running in series in differential mode is easier but you also double the effective ESR of the driver and thus reduce the dampening factor by 50%. Dampening factor is defined by the ratio of load R to driver ESR and is > 1000 on high power woofers where back EMF from sound pressure waves and resonance exists.

- - - Updated - - -

Notice that the parallel implementation of the TI LM3886 uses ESR equalization resistors of value 0.1Ω, which effectively increases the ESR of the source and reduces the dampening factor for bass. Here they succeeded in more than doubling the power using 4Ω speaker with two parallel 100W drivers. Dampening factor of 4Ω/0.2Ω= 80 is adequate for most people unless the speakers have a spurious response that gives much lower than 4Ω at anti-resonance ( low Z or series mode) vs resonance (high Z or parallel mode) then audible distortion would exist.

I suggest you measure your ESR and dampening factor to confirm but series mode is preferred and is the de facto method of boosting audio power in cars limited by 14Vdc.

So I concur with the previous suggestion.