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Connecting a Bose active equalizer IV to a Sausui 9090

i2h82lose1's picture

Is it ok to use connections for the Dolby Adaptor/4 Channel Adaptor Circuit



Re: Connecting a Bose active equalizer IV to a Sausui 9090

I disagree with the pre-out/main-in suggestion . Firmly.
I would never suggest you connect this EQ between the pre-out and main in
because you no longer have complete control of the volume anymore.

as an example, with a dirty switch in the EQ (very common) you would get a tremendous
noise explosion through the power amp if connected at the pre-out/main-in.
Or a dirty slider will crackle and get amplified by the power amp and could cause
damage to your spdeakers
Try it. You'll find out the hard way.

much, much better to connect at the tape circuit per Bose's instructions.
the 4 CH adaptor circuit on the 9090 is electrically the same as an extra tape circuit
so connecting there is fine. ( I've owned several 9090's and Bose 901's at different times)

During the 20 years I worked as a Bose service station repairman I never ran across
any problems with the 901 EQ's beyond the common dirty switches and controls
that many vintage stereos endure. Usually chemical cleaning takes care of this.
I do not agree with the cd player damaging the EQ comment, either. that's "baloney".

the Bose 901 EQ is really no different than anyone else's EQ in terms of how it
gets hooked up. same for most audio signal processors. many manufacturer's suggest
connecting in the tape circuit, which is why they give you a tape circuit loop in
the EQ. (exception would be an active crossover )

by keeping it in the tape connectors circuit, well before the volume control and pre-amp output, you eliminate the possibility of damaging your amplifier or speakers by unexpected noise amplification.
if you put it between the pre-out and main in, any "pop" or "scratchiness" in a
slider control or a switch will get amplified by the power amp and served to the speakers. Since this occurs after the volume control, it can be VERY VERY LOUD.
I know. I've experienced this. The power amp will amplify noise as well as music.

anyway, as you can tell, I disagree with the other commentor's suggestion.
the EQ will tailor the frequency to the 901's in either location, but in my opinion
it would be much safer at the adaptor or tape circuit.
thanks. good luck.

Re: Connecting a Bose active equalizer IV to a Sausui 9090

I never said that the equalizer could be damaged, but overloaded.

Look at the total response curve of the 901 series IV equalizer. 12 to 20 dB gain at 40Hz. For your information, 20 dB gain means that the output voltage would be 10 times larger than the input voltage. The output voltage of CD players can be as large as 2 Volts, on loud passages. But the supply voltage inside the Bose equalizer is limited to ±15 Volts. So, the equalizer will be overloaded at some frequencies. In other words, there would be severe clipping. At 16 kHz, the voltage gain can be as high as 30 dB on this equalizer, meaning a voltage ratio of 16:1

Typical equalisers have only ±12dB or ±15dB range, much less than Bose equalizers.

Bose's instruction to connect in the tape loop is a marketing strategy because if they had suggested to use the pre-out and main-in connection, there would be much less buyers.

As for the pop and noise of dirty controls, if you connect the equalizer in the tape loop they will be amplified by the preamp plus the power amp.

Re: Connecting a Bose active equalizer IV to a Sausui 9090

yes it is ok.

Re: Connecting a Bose active equalizer IV to a Sausui 9090

The best place to connect your equalizer is between the preamplifier output and the main amplifier input. Your receiver has these connectors. The 4-ch adaptor is before the volume control and your Bose equalizer could be overloaded at some frequencies when using a CD player, because the output voltage of CD players can be as high as 2 V. Bose equalizers have never been designed to receive this voltage.