Thank you for the question and welcome to the Bose Community!.
In order for this to work with your 901's, you would need to also purchase a receiver.
You would connect the receiver to the 901 equalizer then to the amplifier you have and then from the amplifier to the 901's.
Hope this helps.
Joel - Community Support
According to my recollection, you need to have the tape loop for the 901's to function the way intended. Otherwise, you can connect them without the Bose EQ but they are going to sound like garbage.
But, I'm pretty sure in order to use the Bose EQ, you need the tape loop...
If there is another way around it, I'd be curious myself.
To reiterate what Joel said before, you would need to purchase a separate receiver to provide an audio signal, since the EQ cannot be directly connected to the Yamaha IA due to a lack of tape loop (like adam said). With a separate receiver, you can send audio out of the receiver into the 901 EQ, then out of the EQ into the amplifier. From there, the audio would travel from the amplifier to the 901 speakers via speaker wire.
If you have any other questions, please let us know.
Brandon - Community Support