Cello Audio Palette clone - My Photo Gallery
For years I have dreamt about this beautiful and versatile preamplifier.
However the pricetag of some 16-17.000 $ used on ebay + transport from the US kind of kept me from it.
So what other thing could I do than clone it.
The Audio Palette
The Cello Audio Palette was a six-band equalizer that came alone or with a build-in preamplifier.
It was the based on Richard Burwen many years of experience with equalizing, and was introduced as the only high-end equalizer. The Cello brand was Mark Levinsons comeback after being thrown out of ...Mark Levinson.
Now equalizers were not – and are still not – considered to be a component that belongs in a high-end system. (This is probably the reason why Cello chose to call it an Audio Palette and not an equalizer). Music lovers (thinks they) want the pure and clean original sound, and do not want to add any un-necessary circuits into the signal path, which might introduce more distortion and noise.
But first of all – this one was different.
Besides it was actually Mark levinson that invented the no-nonsense line, by removing bass and treble potentiometers from his amplifiers. However not many people know the actual reason, but in an interview Mark Levinson said:
” Even though Levinson pioneered the 'straight line purist approach' to audio, he feels that despite the extra path that the signal must pass through, the advantages of the Audio Palette far outweigh the disadvantages. "A purist philosophy does not mean fewer dials. I am not of the purist philosophy - I founded it! I never said that equalizers were bad, I just said that we don't know any that are any good.
"In our previous experience, whenever we put an equaliser into the system, it sounded worse. The Audio Palette is not simply an equaliser, it is a far more complex product than that and the objective is essentially the idea of music restoration. The ability to restore the quality to approximate lifelike sound is different from the design objective of most equalisers which is to allow the engineer the ability to adjust the sound to create a variety of effects. The Audio Palette is userfriendly, anyone can learn to use it in a few minutes and you don't have to be an engineer when you want to restore music. If you don't want to restore music then u are stuck with either listening to bad sound or playing recordings that your system likes to play and 1 don't think that it is a state of the art concept - to spend a lot of money to listen to six records and 2 compact discs."
When you read it, you just realize how true it is.
Okay so how did this Audio Palette achieve the magic goal of adjusting the sound without ruining the sound quality?
First and most important of all, the equalizing part is genious, no really ...GENIOUS!
Instead having a heap of 10 to 31 bands there are only six. Exactly enough to be able to adjust detailed enough for making most bad recordings sound great, and at the same time very easy to operate. This matters a lot, because if one have to go through maybe 31 bands for adjusting the sound, it might be easier just not to do it.
Besides the Q of each band is 0.7 which is a quite soft slope for an equalizer. Normal EQs operate with a Q up to 4 ! This will seriously impact the impulse response, where a low Q of 0,7 is equal to a first-order filter and is quite gentle with the signal.
And to make it even more brilliant the range of each band is wieghted against the human hearing. So in the two mid-bands where your ears are most sensitive, the maximum range is +/-6dB, the two bands on each side, operating in an area where your ears are a little less sensitive, the range is +/-12dB, and finally the two outer controls ( 20Hz and 20kHz) where your ears really needs a kick to tell the difference the range is +/-22dB.
The result is, that even if you dont know anything about deciBel and Herz, you actually feel that the six bands have exactly the same level of impact to the sound, in each their frequency range. Again: very easy to adjust, quite logical function-wise, and it is strange that no-one else has ever made it like this.
The Original
Being a high-end product and to ensure the Audio Palette didn’t add noise and distortion, the circuitry was ofcourse very special. The inside of the huge cabinet was packed with 20-some individual PCBs with discrete class-A modules (power consumption was 100Watt – quite a lot for a preamp!), top-of-the-range components for that era, separate power supply, and some very impressive rotary switches for most of the dials. Use Google for pictures of the whole shabang – very impressive!
Later Cello introduced a lower priced ”Palette Preamplifier” which was buildt with opamps and vishay pots.
My build
All right enough about the original. I might seem suspiciously extatic about it, but I have no economic interests in Cello, or any intend to hype this product for personal gain, I am just simply amazed by the function and the geniousness of this machine – hence as a DIY-lunatic I simply had to clone it.
I started out with making an equalizer that wasn’t a true copy, but which did exactly the same fitted with standard pots.
I used Rod Elliots discription of Ranes constant-Q EQ circuit, which must be very similar to the concept. I was amazed of how well it worked, and really enjoyed the possibility to adjust the sound. I have CDs which are almost unbearable to listen to without eq, but simply turns into magic when I turn a few dials. Suddenly I could enjoy some fantastic music which I couldn’t before.
Allright so I was hooked, and the looks on the original is also just up my alley. So a lot of surfing went into finding the right knobs ( got them on ebay from Hong Kong), and a drawing for the cabinet was sent to modushop/hifi2000 in Italy.
I also did a lot of surfing to find some nice rotary switches. The original had some very nice in-house made 59 position ones, and the closest thing would be a Glasshouse 43 pos but they are quite pricey. Eventually I found some used 26 pos On ebay, which I bought a bunch of. It took me quite some time to clean them and to solder resistors to make linear attenuators from them.
Future plans
So here I am, I would say 2/3 finished, but with a working unit. The EQ board and the preamp part are made with OPA2134 and TL084 opamps on veroboards. They work, and has decent sound quality. But ofcourse I wil at some point replace the circuitry with somenthing more elegant. I have done some reverse-engineering of the original modules based on pctures, but my personal taste in circuits goes in another direction, I am thinking discrete J-fet opamps on real PCBs. The input relay board is scavenged from a autostereo demoboard.
Anyway: I have the cabinet and the switches as I want them to be, so I am going to:
a) Put some text on the knobs
b) Make a remote control circuit of volume and input selection
c) Eventually replace the circuits inside.
...But I just felt like sharing allready at this stage.
Questions? ...just shoot.
All the best from Henrik
For years I have dreamt about this beautiful and versatile preamplifier.
However the pricetag of some 16-17.000 $ used on ebay + transport from the US kind of kept me from it.
So what other thing could I do than clone it.
The Audio Palette
The Cello Audio Palette was a six-band equalizer that came alone or with a build-in preamplifier.
It was the based on Richard Burwen many years of experience with equalizing, and was introduced as the only high-end equalizer. The Cello brand was Mark Levinsons comeback after being thrown out of ...Mark Levinson.
Now equalizers were not – and are still not – considered to be a component that belongs in a high-end system. (This is probably the reason why Cello chose to call it an Audio Palette and not an equalizer). Music lovers (thinks they) want the pure and clean original sound, and do not want to add any un-necessary circuits into the signal path, which might introduce more distortion and noise.
But first of all – this one was different.
Besides it was actually Mark levinson that invented the no-nonsense line, by removing bass and treble potentiometers from his amplifiers. However not many people know the actual reason, but in an interview Mark Levinson said:
” Even though Levinson pioneered the 'straight line purist approach' to audio, he feels that despite the extra path that the signal must pass through, the advantages of the Audio Palette far outweigh the disadvantages. "A purist philosophy does not mean fewer dials. I am not of the purist philosophy - I founded it! I never said that equalizers were bad, I just said that we don't know any that are any good.
"In our previous experience, whenever we put an equaliser into the system, it sounded worse. The Audio Palette is not simply an equaliser, it is a far more complex product than that and the objective is essentially the idea of music restoration. The ability to restore the quality to approximate lifelike sound is different from the design objective of most equalisers which is to allow the engineer the ability to adjust the sound to create a variety of effects. The Audio Palette is userfriendly, anyone can learn to use it in a few minutes and you don't have to be an engineer when you want to restore music. If you don't want to restore music then u are stuck with either listening to bad sound or playing recordings that your system likes to play and 1 don't think that it is a state of the art concept - to spend a lot of money to listen to six records and 2 compact discs."
When you read it, you just realize how true it is.
Okay so how did this Audio Palette achieve the magic goal of adjusting the sound without ruining the sound quality?
First and most important of all, the equalizing part is genious, no really ...GENIOUS!
Instead having a heap of 10 to 31 bands there are only six. Exactly enough to be able to adjust detailed enough for making most bad recordings sound great, and at the same time very easy to operate. This matters a lot, because if one have to go through maybe 31 bands for adjusting the sound, it might be easier just not to do it.
Besides the Q of each band is 0.7 which is a quite soft slope for an equalizer. Normal EQs operate with a Q up to 4 ! This will seriously impact the impulse response, where a low Q of 0,7 is equal to a first-order filter and is quite gentle with the signal.
And to make it even more brilliant the range of each band is wieghted against the human hearing. So in the two mid-bands where your ears are most sensitive, the maximum range is +/-6dB, the two bands on each side, operating in an area where your ears are a little less sensitive, the range is +/-12dB, and finally the two outer controls ( 20Hz and 20kHz) where your ears really needs a kick to tell the difference the range is +/-22dB.
The result is, that even if you dont know anything about deciBel and Herz, you actually feel that the six bands have exactly the same level of impact to the sound, in each their frequency range. Again: very easy to adjust, quite logical function-wise, and it is strange that no-one else has ever made it like this.
The Original
Being a high-end product and to ensure the Audio Palette didn’t add noise and distortion, the circuitry was ofcourse very special. The inside of the huge cabinet was packed with 20-some individual PCBs with discrete class-A modules (power consumption was 100Watt – quite a lot for a preamp!), top-of-the-range components for that era, separate power supply, and some very impressive rotary switches for most of the dials. Use Google for pictures of the whole shabang – very impressive!
Later Cello introduced a lower priced ”Palette Preamplifier” which was buildt with opamps and vishay pots.
My build
All right enough about the original. I might seem suspiciously extatic about it, but I have no economic interests in Cello, or any intend to hype this product for personal gain, I am just simply amazed by the function and the geniousness of this machine – hence as a DIY-lunatic I simply had to clone it.
I started out with making an equalizer that wasn’t a true copy, but which did exactly the same fitted with standard pots.
I used Rod Elliots discription of Ranes constant-Q EQ circuit, which must be very similar to the concept. I was amazed of how well it worked, and really enjoyed the possibility to adjust the sound. I have CDs which are almost unbearable to listen to without eq, but simply turns into magic when I turn a few dials. Suddenly I could enjoy some fantastic music which I couldn’t before.
Allright so I was hooked, and the looks on the original is also just up my alley. So a lot of surfing went into finding the right knobs ( got them on ebay from Hong Kong), and a drawing for the cabinet was sent to modushop/hifi2000 in Italy.
I also did a lot of surfing to find some nice rotary switches. The original had some very nice in-house made 59 position ones, and the closest thing would be a Glasshouse 43 pos but they are quite pricey. Eventually I found some used 26 pos On ebay, which I bought a bunch of. It took me quite some time to clean them and to solder resistors to make linear attenuators from them.
Future plans
So here I am, I would say 2/3 finished, but with a working unit. The EQ board and the preamp part are made with OPA2134 and TL084 opamps on veroboards. They work, and has decent sound quality. But ofcourse I wil at some point replace the circuitry with somenthing more elegant. I have done some reverse-engineering of the original modules based on pctures, but my personal taste in circuits goes in another direction, I am thinking discrete J-fet opamps on real PCBs. The input relay board is scavenged from a autostereo demoboard.
Anyway: I have the cabinet and the switches as I want them to be, so I am going to:
a) Put some text on the knobs
b) Make a remote control circuit of volume and input selection
c) Eventually replace the circuits inside.
...But I just felt like sharing allready at this stage.
Questions? ...just shoot.
All the best from Henrik
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