Michi RHC-10. Bi amping?

J

johnandchris

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Hi everyone. A technical question for anyone with knowledge.

I have been toying with a change in my amplification for a while. I have a Rotel RC-995 into 2 RB971 power amps and they are perfect, just really wanted something different.

I have just managed to find a passive pre amp, A Rotel Michi RHC-10 which is a very well regarded passive pre-amp. I have not received it yet but i am looking into how to connect it up.

The Michi only has one set of RCA outs (there is another but it is for a tape loop) and whilst i will be happy running it through one of the RB971 amps, i would rather run it through 2 for the power.

Does anyone have any ideas how i could use my 2 RB971 amps in a bi-amp configuration with the Michi, or is it a no go.

If not i may have to look at a more powerful power amp (if anyone has a Michi RHB-10 or RHB-5 that they dont want i may be interested!!!)

Grateful of any help on this one.

Thanks

John
 
You can simply connect the pre-amps output to both power amnps with a splitter cable. However, because the pre-amp is passive, the impedance (load) seen by your source equipment will be halved (assuming both power amps have the same input impedance). This can be bad depending on the output impedance of the source and the value of the potentiometer in the passive preamp.

For example if your power amps have 47K input impedance and the pre-amp uses a 10K pot, and your source impedance is 100Ohms, you are probably okay. If the amps have an input impedance of 15K and the source has an output impedance of 1K, you are in trouble. Do a bit of searching and get back with the details.

The result of a bad match would be frequency response changes at the extremes, which vary when the volume position is adjusted.
 
Just had a thought. The RB-971 amps are bridgeable so can therefore be used as a monoblock.
If i move the jumpers into the monoblock format, connect one amp to the left channel from the pre and the other to the right, i will be able to drive each speaker off 1 amp. I think that this would be OK.

What benefits would this have over using 1 of the amps as a stereo power amp. Are there any downsides?

John
 
No downsides to this, only benefits. Mono-blocking is better than putting one amp on bass and one on tweeters.

Think about it this way - if you split the amps between channels, then you split the heavy power requirement (bass) between two amps. Alternatively, if you have one amp for the bass and one for the treble, you still have one amp working its knackers off, and one that is hardly trying.
 

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