Connecting digital piano to stero receiver

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Earl,musician soon
Connecting digital piano to stero receiver

I would like to connect a Yamaha CP33 digital keyboard to my Pioneer VSX-D209 receiver. I am planning on buying this digital piano to be used as the sound source in a self contained unit that I plan on building that will resemble one of the square pianos of the 19th century. When completed, it will have its own amplification and speakers.


In the meantime I would like to get the best sound possible with what I have .I have spoken to the manufacturer, dealers and friends and there seems to be many opinions about the results I’ll get-providing I keep the keyboard volume down and not blow up my older equipment. The predictions range from just great sound to just barely acceptable and that I should use the microphone out on the piano or some sort of attenuator between the piano and receiver or perhaps do nothing at all.


I think there are two problems that need addressing but I don’t know the technical language to state them properly, but I will do as best as I can. First, there is the strength of the output of the piano that will be going to the pre-amp of the receiver that must be changed without adding distortion or somehow filtering some of the complex sounds that should go through. Second, there is something called equalization that sometimes exists but must be identical in both the source and the receiver so as not to distort the volume levels over the sound spectrum. (I had an amplifier in the 50’s that had a knob that let you choose several equalizations, such as RCA, I think Columbia, and RIAA[I think] and others depending on the vinyl record and the tone arm’s cartridge).


The output on the keyboard is described as MIDI (IN/OUT), PHONES, “OUTPUT (L/MONO, R).


The input on the receiver is for “CD, VCR/DVR, CD-R/TAPE/MD, DVD/LD, TV/SAT..........200mV/47 k...”


Any information would be greatly appreciated.




Larry Dillon
CP33 Specifications

CP33 Specifications
Keyboard GH keyboard 88 keys (A-1 C7)
Sound Source AWM Dynamic Stereo Sampling
Polyphony (max.) 64
Voices 14 x 2 variations for each Voice
Effects Reverb, Effect, Brilliance
Controls Dual, Split, Click, Transpose, Touch (Hard/Medium/Soft/Fixed), Functions
Pedal SUSTAIN PEDAL (can be used with half-pedal effect), AUX PEDAL (assignable to various functions)
Controller Master Volume Dial, Pitch Bend Wheel, Modulation Wheel, Zone Control Sliders
(W x D x H)
1312 x 330 x 151 mm (51-5/8" x 13 x 5-15/16")
Weight 18 kg (39 lbs., 11 oz)
Accessories AC Power Cord, Foot Pedal FC3, Owner's Manual

Are the output for the L/mono,R regular RCA jacks?  If they are then the output standard on these jacks are .775 Millivolt, an industry standard for 0 db, so they can be used on a tape monitor input or an aux input.

Earl,musician soon
Yamaha CP33 manual describes

Yamaha CP33 manual describes them as " Jacks"...( 1/4" mono phone plug ).



Larry Dillon
Yes Earl Use a 1/4 inch phono

Yes Earl Use a 1/4 inch phono plug to an RCA female adaptor from the Piano, then you should be able to then use a set of RCA cables to the reciver inputs. Ask the Yamaha peeps what the output voltage is there just to make sure. As you could if its over 0db simply use an antenuator

Earl,musician soon
Well, yes, they all said this

Well, yes, they all said this but what I am concerned with is the equalization curve that the receiver inputs have or may not have that must match any equalization in the signal coming from the piano if indeed that signal is equalized. Weren't the tape monitor inputs equalized for some type of noise reduction system like Dolby? But I don't know about the aux inputs's equalizatiom. 

Also what kind of attenuator would I use to be sure that I am not introducing distortion because of the fiddling with the piano's original signal?

And thanks, Larry, for the information. 



Larry Dillon
First of all find out what

First of all find out what the VOLTAGE output is!  This is most important!  Or yes you will burn up the input section of the amp.  Now really this reciver is not the best choice to power a piano.  you should have a separate EQ and a straight power amp with no eq or preamp.  You can use it But will it give you the sound your looking for?? probably not but will amplify it.  now I dont want to burst your bubble but you be the judge. First, like i said before, find out if the output from the line out exceeds .775 volts.  They should know this at Yamaha. If it does not just simply plug it into an AUX input and dont worry about the EQ curve as you cannot change that on this reciver as it already has all thisd built in, thats why im saying it most likly will not be the right sound for you unless it has a way to by pass the tone circuitry.

Earl,musician soon
Thanks, Larry, for trying not

Thanks, Larry, for trying not to burst my bubble and I will try to get the information you wrote about.

 If the equalizqtion curve issue is indeed insurmontable perhaps I should now get an amplifier that could eventually be used with a dedicated speaker system but for the time being be connected to my Pioneer speakers and subwoffer. I would guess I could find a moderately powered unit that would fit the bill. I think I would look for quality over power in exactly the right kind of amplifier. 

Thanks again

Earl Guedry 

Earl,musician soon


Pioneer says that there isn't any way to bypass the equalization in their receivers and Yamaha hasn't called back after searching for the voltage output on the keyboard but my receiver apparently remains not suitable regardless.
I was looking at and this amplifier seems suitable, at about $150.00.

Samson S120A Power Amplifier (120 Watts)
Product Description
Ideal for powering near field monitors or installation sound, the new Servo 120a provides you with "reference-class" audio performance and reliability in a compact package. Perfect for studio, live sound and home theater applications, the 120a's bipolar design and toroidal transformer power supply ensure reliability and quiet performance.

1-space 19-inch rackmount servo-controlled power amplifier
60 watts per side at 4 ohms stereo
120 watts at 8 ohms (bridged mono)
1/4 in. balanced phone jack and RCA inputs
Bi-polar design and toroidal transformer power supply
Individual left and right level controls
5-segment, 3-color LED meters
Convection-cooled design
Headphone jack with speaker output mute

Do you think this type of amplifier would meet all the requirements for connecting a digital piano to standard speakers as well as raw speakers in a future application? Is this one in the correct category of amps that I should be looking into.


Larry Dillon
Yes it sounds very useable.

Yes it sounds very useable. I would also check into some sort of EQ or limiter between the amp and the keyboard.

Earl,musician soon
Yamaha called back with the

Yamaha called back with the information about the voltage. They said between .5 and 1.33 volts was the output of the digital piano. They also said I could use my receiver because unless I would use the "phono" input there is no equalization, but I don't know. Seems like I read somewhere that each type of recording method has its own EQ, but it's still not flat. I assume the piano's signal is flat. My receiver has no aux input. Maybe that would be flat, if it existed.

What is an EQ or limiter? could I get that built in the amplifier? What I hope to build is one piece of furniture with the Yamaha for a keyboard and raw speakers producing the sound. Yesterday, I just remembered  that I already have two unused speaker units that I made years ago from Philips components. Each is three way with a 12" woofer and two crossover networks with two volumn controls under the front grill cloth. If they still sound as good as when I used them I could incorporate them.

Do the monitors that Yamaha wants me to buy have an EQ or limiter, do you think?




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