# Two audio amplifiers in series (IKEA symfonisk into powered speakers)

I am hacking an IKEA symfonisk into being a cheap, Sonos connected amp, but the speakers I would like to wire it into are not passive, but active.

I am just wondering if the fact that there is an amplifier in the sonos speaker, which is sending amplified signal to the amplifier in the powered speaker, will cause issues for the speaker and potentially result in damage.

Each Sonos speaker actually has two channels (high and low frequencies) so I would also like to sum those into one signal for each speaker.

Would something like the diagram below work?

• Probably no. Active speakers have amplifiers inside and they accept inputs at about line levels (from 0.5Vrms to 1~1.2Vrms). If you apply an already-amplified signal to the active speaker's input then the signal may get distorted (clipped, due to over-amplification) which can be heard as a harsh, annoying sound. Please note that this does not mean that you are allowed to apply high voltages (e.g. 10Vrms or so) to the active speaker's input. Commented Feb 23, 2020 at 10:02

Just build an attenuator.

simulate this circuit – Schematic created using CircuitLab

If the sourcing amplifier is bridge mode, use spkr OUT+ and GND, and ignore spkr OUT-

Attenuator component values are fairly non-critical, values shown are a reasonable starting point. If it's too quiet, double R1.

• I know this is probably a really obvious question, but why is the amp in before R1? Should it not be at the end of the chain? P.S. Thanks for this great answer!
– Zen
Commented Feb 23, 2020 at 21:49
• "the end of the chain" (the bottom of R1) is Ground ... 0V ... nothing into the amplifier means nothing out. As it is you get 1 / (1+4.7) or about 1/6 of the input voltage out, which should be low enough to avoid overloading the input stage of the second amplifier.
– user16324
Commented Feb 23, 2020 at 22:35
• Please let me know what you think of the diagram I added to the question
– Zen
Commented Feb 24, 2020 at 2:48
• That's an entirely different question. And you have shorted the -ve outputs together. If those are bridge mode amplifiers, you have blown them both up.
– user16324
Commented Feb 24, 2020 at 13:37

There are a few potential problems:

• The output of the Sonos will be several volts. The input to your powered speaker will be < 1 V max and exceeding this will result in clipping distortion.
• Turning down the volume of the Sonos will prevent the clipping but since the volume control will precede the power amplifier the hum and noise from the Sonos amplifier stage will not be attenuated. i.e., the signal (music) to noise ratio will decrease.

Figure 1. A bridge-mode amplifier configuration. Note that neither side of the speaker is grounded. (Ignore the 160 W reference.) Image source lost in the mists of time.

Figure out the details of the Sonos, have a look at the power amplifier chips, read the datasheets and post the details in your question.