Cello Audio Palette

kevinh

Member
2007-05-08 4:19 am
I agree. The point is to enjoy music, we are choseing our own ways to achive that.




What I find interesting about this discussion is that in seeking the 'best' sound there are factors that have a primary effect on the sound then other factors that are secondary, then factors that are minor at best.


In my opinion the Speakers and Room Acoustics are primary factors in the sound of a system.

The electronics are secondary. There are identifiable factors in the quality of the sound, eliminating crossover distortion, making sure that distortion components are low order distortion primarily 2nd harmonic with less 3rd and that distortion decreases in a liner manner with volume and remains low order harmonics. Clean power to the electronics and so on.

The rest cables and so on are very minor to non existent.

I think that a well designed tone control like the Palette. has the influence of speakers and room acoustics. Probably just below that level but much more influence than the difference between well designed electronics.


I think that in trying to perfect the 2nd and 3rd order factors many of us don't pay enough attention to the rooms acoustics and tone controls for our systems.

Now that the Burwin Bobcat has been reduced in price to $469 USD it will be my next purchase.
 

GoranB

Member
2010-03-03 12:33 pm
Poland
What I find interesting about this discussion is that in seeking the 'best' sound there are factors that have a primary effect on the sound then other factors that are secondary, then factors that are minor at best.


In my opinion the Speakers and Room Acoustics are primary factors in the sound of a system.

The electronics are secondary. There are identifiable factors in the quality of the sound, eliminating crossover distortion, making sure that distortion components are low order distortion primarily 2nd harmonic with less 3rd and that distortion decreases in a liner manner with volume and remains low order harmonics. Clean power to the electronics and so on.

The rest cables and so on are very minor to non existent.

I think that a well designed tone control like the Palette. has the influence of speakers and room acoustics. Probably just below that level but much more influence than the difference between well designed electronics.


I think that in trying to perfect the 2nd and 3rd order factors many of us don't pay enough attention to the rooms acoustics and tone controls for our systems.

Now that the Burwin Bobcat has been reduced in price to $469 USD it will be my next purchase.

Every segment of an audio system is important less or more. Good audio source and amplifier should be followed by good speakers and adequate room. I also agree that speakers are very important in the audio chain. We can use EQ to try to fix the frequency responce in our rooms, but how we can be sure that we are doing the right thing? Our ears are not the reference we can follow, its too subjective. Without adequate meassuring equipement installed in our rooms (SF) we cant be sure if we are doing right.
 

GoranB

Member
2010-03-03 12:33 pm
Poland
Measuring the room and having good speakers in a good room is always the primary focus. In my ideal situation I would put the most $$$ into the best speakers I could afford and an equal amount of $$$ into a properly designed room using acoustic design materials like those from RPG

RPG Diffusor Systems

It could be the primary focus for those who are lucky to have separated room for listening, but majority of us can only dream about. In a hypothetic, almost perfect room for listening, equiped with the best audio equipement it could be that there will be no need for an equalizer.

Anyway i deeply support Nrik's project. He made really good work with the case, probably he will use better circuits and parts in the future to upgrade his project.
 
I'm all for being able to adjust the sound. I tried many affordable units and couldn't listen to them. I only wish I could afford or build something like the OP did. I found some pictures of insides of both Palette and Audio Palette. Latter was a "cheapy" version ($6500 new), used op-amps etc, inside looks normal. There is one on Audiogon right now, sitting at $1700 already. There is an Audio Palette there as well, asking price $15500. That one is filled out to the rim!

In any case, I am tired of living with a straight wire... I wonder if there are any affordable EQs out there that would not make my ears cringe. So far - and surprisingly - the least damage was caused by the long discontinued Behringer digital signal processor DSP8024, but it's like a computer and is difficult to operate. BTW, DSP 2496 that came after, IMHO - sucked.

Suggestions?
 

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Tone Controls are a must. Personally I prefer a four band baxandall (variable slope) that I have developed over several decades of experimenting. Those rich fools who have no tone controls on their $5000 preamp probably also spent over $1K on their speaker wires (heh heh heh)... Your tone control unit is probably one of the best investments you could make in a system.

Linkwitz uses the OPA2134 opamps in his active crossovers (me too). They sound excellent to my ear. Put power supply bypass caps (usually 0.1uF) within 2 inches of any opamp, closer is better. If all the resistors over 1K are metal film 1%, all the caps are Polyprop or better, it's unlikely that further improvements will be audible. Using a "star-center" grounding scheme properly is where a lot of people make mistakes.

High surge current gnd. wires at the primary filter caps and bridge rectifier should join together first, before entering the "star center" gnd. bolt. I use regular 78 and 7915 TO-220 regulator chips in the power supply, but because the power supply is always directly in the signal path, and can destroy the stability (phase margin) of any high feedback circuit (opamps in this case) if it presents an inconsistent impedance over frequency , I always put at least a few uF of polyprop caps across the output of any power supply, so the opamps see a short for AC from about 1HZ to many many mHZ.

I even use separate ground return wires and power supply bypass caps for each section of circuitry. AND passive Rf filtering at the audio and AC inputs, since opamps turn to crapp when trying to deal with Rf energy that gets brought in by everything external acting as an antenna. I BW limit to 100kHZ with a simple RC at the inputs, and 0.01 3kV caps across the AC line in and 0.1uF (or more) across any electrolytics. It's often these little "side issues" that taint or corrupt the quality of an otherwise good circuit. Hope this is helpful. Maybe you already know all of this.
 
I once saw an ad for an equalizer from Acoustic Research. Looked like it was well made. A poor man's Cello Palette. Does anyone know if it was actually produced?

Yes it was, and they pop up for sale from time to time, prices vary greatly I've had one. The looks and build were much better than the sound. Like a typical eq of that era it detracted more of the sound than it helped. That one was advertised as poor mans Cello. I switched to digital sound processing after that.
 

talaerts

Member
2005-10-15 8:09 am
This is a lovely project.

For another approach, I use the Quad 44 pre-amp which also features a very effective tone control, with just a few controls. For overly aggressive cds, it really brings more music.

[IMGDEAD]http://www.retrohifi.co.uk/tone_controls.jpg[/IMGDEAD]

The left control adds bass or filters it from a chosen frequency (it's 2 functions in one knob).
The middle Tilt controls shifts the balance between bass and treble
The right control allows to filter the treble from a certain frequency (chosen with the outer switch) and a chosen slope (chosen with the inner knob). This last control works very well for bad sounding cds.
I wonder if there are clone circuits of this functionality.

About the Audio palette, if it's not too much work to type this, exactly what is the function of each knob?
 
Some more information on the Cello Palette (introduced around 1985). Dick BurwEn did do the conceptual design for ML (I have a copy of the original blueprint schematic - which uses op-amps). ML's great designer, Tom Coelangelo then took that design and created the Palette using all discrete parts (crafted from a number of op-amp and voltage follower modules). The frequency controls were the same 51 (or so) stepped attenuators used for volume controls in the Audio Suite, another landmark ML product.

The frequencies and boost/cut amounts were 20hz, +-22dB; 120hz, +-12dB; 500hz, +-6db; 2Khz, +-6dB; 5Khz, +-12dB and 20khz, +-22dB. The Palette was available in two models - one had switching for multiple inputs. Both had an in-out switch, left/right input level controls and a ganged output control. Cello boasted that the unit contained some 3000+ parts and must have been a BEAR to assemble.

In the late 80's, Cello decided to come out with a less expensive unit (I'd say it was 85% of the functionality at half the price) - and this product was called the Palette Preamplifier. It looked very similar to the original Palette but used IC's - basically a whole lot of 627's. It's design is very similar to the octave equalizer on pages 2-53 to 2-56 of the National Semiconductor Audio Handbook EXCEPT that Burwen did not put all of the equalizer sections in parallel but put a few in series and those in parallel with the others. And for best results, the paralleled equalizer sections have to be driven from as low impedance as possible, so Tom used a 627 followed by an IC buffer to do that job.

In the early 90's, Cello entered into an ill-fated venture with Teledyne?/AR and advertised at least the equalizer, an amplifier and perhaps a speaker or two under what name?? Didn't realize that the venture actually released a few units.

3 or so years back, a friend found the remains of Cello (gathering dust after the 2000 bankruptcy auction) in a Connecticut warehouse. I got a number of parts, PC boards and the like and was able to put together a Palette Preamplifier. But I did it differently; Built the equalizer into a case separate from the preamplifier and separated the two by a 30ft umbilical. This allows me to make any necessary equalizing adjustments right from my listening position - a feature that most equalizer designers have totally missed.
The finished unit is a joy to use. Burwen realized that the midband controls don't have to have a lot of boost cut (I don't use more than 2 to 3 dB) while the extremes can use more - 22dB is probably too much - 12 to 15 is fine.

I mostly use it in a "subtractive" mode - reducing the 2-5kHz "glare" on many female CD vocals has made the difference between stopping midway through the first cut versus listening to the whole album. In the "additive mode" adding some 120Hz midbass and maybe some 20hz can really improve some other albums. As an aside, I'm amazed that on many recordings, I can "rock" the 20hz control to either stop with no effect - nothing on the material below 50 hz or so.

I believe that the key to the Palette's success was that it was as close to "transparent" as any (program) equalizer ever made.

Charles
 
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6L6

Moderator
Paid Member
2010-10-22 6:43 pm
Denver, Colorado
Nrik - Your project is fantastic! What's the possibility of seeing a schematic?

The first amazing-gonzo-megabuck system I have ever seen (heard) was a friend of my mother's, who had a completely Cello system driving a pair of Martin-Logan CLS. He was a guy who made his own (very good) recordings and such. Anyway, he had his Audio Palette next to his listening chair. I got to play with it, and it was totally and completely awesome.

To this day I think that it was the coolest widget ever in all of audio.
 
I once saw an ad for an equalizer from Acoustic Research. Looked like it was well made. A poor man's Cello Palette. Does anyone know if it was actually produced?



Stellavox - excellent right up! Thank you very much

I've had a Cello inspired AR EQ, and it was not very good nor transparent.

I wish i could find a warehouse filled with Cello Suites and such :)

M





[IMGDEAD]http://img810.imageshack.us/img810/6453/dsc01105jpg29000561.jpg[/IMGDEAD]
 
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This interesting thread continues:

Kevin, I'd like to comment on your comments about the most important factors in the sound of a system. I've had the pleasure of "experiencing" a few systems where I can actually hear "over or around" it enough that I can forget about the "gear" and listen (enjoy - revel - whatever) to the INFORMATION it is producing - please note that I didn't say MUSIC yet. If you can believe that what you are hearing is what is "in the grooves" then unfortunately you can become attuned to a whole series of what I'll call "transcription imperfections". Like the acoustics where the room was recorded - microphone "peakiness" and resonances (very common with vocals) and the like. This is where I've found that an instrument like the Palette can help.

And I don't have a website yet where I can post pics of my unit - that's next on the agenda.

Oh; and Goran, you ask how you set the EQ for the different material. My simplest answer is "by ear". As with everything else, there is a learning curve - realizing where the frequencies of certain types of music "appear" combined with understanding how the various EQ filters "effect (or should it be affect?)" those frequencies. After a while you "get it" and can accomplish a "re-eq" in a matter of seconds - then sit back and enjoy the rest of the album. Having the control unit right at your listening position aids immeasurably - in fact I think it's a must. I now put any "EQ notes" on the material sleeve. Cello actually supplied a pad of paper with all the controls shown - you could use one sheet for each piece of material and add an arrow where you finally set the control.

A very interesting experiment is, after determining the "optimal" settings on the EQ unit for a particular album, listen to the rest of it then go back to track one and switch out the EQ and listen again. You won't have to do this for long, and everyone I've done this for has been astonished.

As I did say though, transparency of the EQ device with all band controls effectively "off" (or in neutral) is key. From then its ALL subjective - but then again isn't everything with this hobby.

And I don't use it very much - only when I think there is a "real problem" ???!!!

Cheers everyone!

Charles
 
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