Cello Palette Style EQ Design (was High End Tone Control)... - Page 2 - diyAudio
Go Back   Home > Forums > Source & Line > Analog Line Level

Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
View Poll Results: If you where to build a Cello Palette functional clone, what technology do you want?
I want a Software Palette, Analogue EQ is SO 20th Century 8 16.67%
I want a purely passive EQ to which I want to add my own input buffer and output amplifier (MPPJBTS) 9 18.75%
I want a Minimalist discrete EQ using Tubes (ZenEQ derived from the "East German EQ") 15 31.25%
I want a Minimalist discrete EQ using Solid State (ZenEQ derived from the "East German EQ") 22 45.83%
I want Op-Amp's with parallel and summed bands (e.g. NitePro EQ3D) 5 10.42%
I want Baxandall Sections with Op-Amp's connected in series (e.g. Carl_Huff) 3 6.25%
Multiple Choice Poll. Voters: 48. You may not vote on this poll

Reply
 
Thread Tools Search this Thread
Old 28th March 2012, 03:43 AM   #11
EUVL is offline EUVL  Europe
diyAudio Member
 
Join Date: Oct 2003
> It was designed in East Germany in the late 70's and remains somewhat legendary for it's sound quality. It avoids the use of looped feedback, which similar western Pro-Audio design already used in massive amounts routinely. I can attest to the sonics of this type of EQ, I used it extensively.

For a High End solid state design, I would have thought that one would want to at least get rid of the coupling caps ??


Patrick
__________________
xen-audio.com
  Reply With Quote
Old 28th March 2012, 03:52 AM   #12
Previously: Kuei Yang Wang
 
Join Date: Nov 2002
Hi,

Quote:
Originally Posted by jameshillj View Post
As I understand this, the primary duty of the "Tone Stack/Control" is to correct recording anamolies but my speakers fall off pretty quickly below 34Hz, would it be better to move the lower 20Hz filter up to at least 34Hz for my system? And the next speakers I have in mind require the Link Transform eq (the B2 alignment, closed box design and would this conflict with this tone control design?
One could include suitable circuits after the actual control, such a combination of Speaker LF EQ and Highpass. I would not as such change the Centre frequencies of the EQ.

Quote:
Originally Posted by jameshillj View Post
Having to work with a "Sea of Knobs" for years, it's not something I want to do at home - you just don't bother after a while.
It depends, I find I did when I used a Behringer DEQ in a similar style/application... The use must be quick, intuitive and easy, the EQ must be easily available.

Ciao T
Attached Images
File Type: jpg TL System with EQ.jpg (80.0 KB, 671 views)
  Reply With Quote
Old 28th March 2012, 06:33 AM   #13
Previously: Kuei Yang Wang
 
Join Date: Nov 2002
Hi,

Quote:
Originally Posted by EUVL View Post
For a High End solid state design, I would have thought that one would want to at least get rid of the coupling caps ??
Why? As I routinely work with Tubes I have no irrational fear of coupling capacitors. Often, but not always they are a better choice than the direct coupling alternatives, which in actually still have coupling cap's, but so to speak "hidden from sight".

I notice Papa Pass's "Zen" range also has coupling cap's...

FWIW, the point is not to copy the East German design exactly, but to use the principles embodied. It would be possible to make a fully DC coupled circuit using rail symmetrical folded cascodes. But this would need a DC servo which I find most of the time worse than a high quality coupling cap. Complementary FEt's that are suited are also becoming hard to find. And I'd rather like to keep a level of simplicity that parallels the Pass B1.

I am sure what I can do with eight or nine J-Fets or less if I add some inductors and a handful of resistors and capacitors can be extended into something that requires over 30 Op-Amp's and offers less functionality and worse subjective sound quality, but I'll leave that sort of thing to those who have made it their life's work.

Ciao T
  Reply With Quote
Old 28th March 2012, 10:51 AM   #14
EUVL is offline EUVL  Europe
diyAudio Member
 
Join Date: Oct 2003
> As I routinely work with Tubes I have no irrational fear of coupling capacitors.

Somehow I knew you were going to say this.




Cheers,
Patrick
__________________
xen-audio.com
  Reply With Quote
Old 28th March 2012, 10:57 AM   #15
EUVL is offline EUVL  Europe
diyAudio Member
 
Join Date: Oct 2003
BTW if I understand the circuit correctly, it might be simpler to do this fully balanced input / output if direct-coupled.


Patrick
__________________
xen-audio.com
  Reply With Quote
Old 28th March 2012, 11:19 AM   #16
gk7 is offline gk7
diyAudio Member
 
Join Date: Oct 2007
Location: Vienna, Austria
Great project; some questions:

I take your point that one can use a high pass filter after the EQ
(adds another stage though) and cello uses 20Hz too, but if I have for
example a ported box tuned to 40 Hz, I would not expect any useful output at 20Hz while
probably some adjustment at 40 Hz would be nice to have. The East German EQ
uses 63 Hz (probably a bit high) and the Neumann W491 45 Hz.

Are there plans to have the lowest center frequency adjustable,
let´s say 20-40 Hz ?

You mentioned the use of FETs, which do you have in mind (so we can
buy some as long they are available) ?
  Reply With Quote
Old 28th March 2012, 01:55 PM   #17
Gopher is offline Gopher  United Kingdom
diyAudio Member
 
Join Date: Nov 2005
Location: UK
How is this thread any different from the other one? It's already turning into a talking shop with everyone putting their bit in but nothing getting decided. There'll be 10 or so pages of this then it will fizzle out like the other thread.

Oh and Thorsten - I did make concrete suggestions. Look again. If you want part numbers how about OPA627 with a National buffer or the AD 811 or AD815 if you want to use multiloop.

Last edited by Gopher; 28th March 2012 at 02:01 PM.
  Reply With Quote
Old 28th March 2012, 04:11 PM   #18
Previously: Kuei Yang Wang
 
Join Date: Nov 2002
Folks,

I had the chance today to run the "ZenEQ" concept through Tina-Ti. This is not necessarily meant to be a final design, rather a quick study how a simple circuit may perform.

This reminded me that if we require a more or less proportionate boost in dB vs. rotation we need to use potentiometers that are "S" curve, not linear. These are hard to get these days.

If using linear pots then the adjustment range gets bunched up towards the extremes. This is not necessarily a bad thing, as it makes very small adjustments very precise, the downside is that if we need a lot of correction we are left with very little usable travel.

If using switches as controls this is of course of no consequence at all, as we simply can select the correct resistances to give correct dB/vs. Attenuation.

Attached is Tina-Ti File I used (needs latest version) and some simulation results, all using 10K//1nF load. I am not sure how accurate the models buld into Tina-Ti are etc., but it would seem okayish for ballpark.

I would specify 2SK170 BL or V for the circuit, Tina-Ti lacks the model, so I made up a compound from 2N3819 & a PNP BJT, 2SK170 will show worse THD. I am for now showing ideal chokes, they can be replaced by gyrators, but I lack the time right now. For the LF choke 2H with < 120 Ohm DCR are needed, I do have a few such around, so we know they can be made.

The schematic looks like this:

Click the image to open in full size.

The curves produced by stepping the pots in 10% intervals (this is equivalent to rotating linear pots 10% of the rotation for each step):

Click the image to open in full size.

The frequency response with controls perfectly centred (impossible with pots) looks like this:

Click the image to open in full size.

The LF rolloff is a result of the 2.2uF coupling capacitors shown. I habitually use this value, it works fine IME.

To illustrate two interesting EQ results, here what it looks like with all controls set halfway towards maximum cut from neutral:

Click the image to open in full size.

This illustrates rather well how the various bands combine and with a weighting that is similar to the ISO Equal loudness peaks and through...

And here a EQ setting that can help with modern overproduced recordings, by cutting back presence and "kick" bass, and dialing the extremes up, all just a touch:

Click the image to open in full size.

The required pot settings for this (0 = centre, 0.5 is half way between zero and the respective end, linear pots assumed) are:

15Hz = +0.5
120Hz = -0.5
500Hz = +0.2
2KHz = 0.0
5KHz = -0.8
20KHz = +0.6

Here harmonics for 1V out which adds up to 0.005% THD according to Tina-Ti:

Click the image to open in full size.

and for 4V out which adds up to 0.05% THD according to Tina-Ti:

Click the image to open in full size.

Clipping (1% THD) is at 5V.

Tina-Ti has a seriously funky way of showing noise, anyway, it works out ot -120dB unweighted re. 1V, which seems too good to be true. Still, might be on the money:

Click the image to open in full size.

I hope all of this gives people some ideas for the "ZenEQ" and what sort result could be possible, to see if it is worth proceeding. To me the performance looks acceptable, we can get better measured results using Op-Amp's, but I doubt the sound will be improved.

Ciao T
Attached Images
File Type: gif ZenEQ.gif (15.0 KB, 888 views)
File Type: gif Compound.gif (36.4 KB, 888 views)
File Type: gif Frequency Response.gif (30.0 KB, 885 views)
File Type: gif SNR 1V.gif (28.7 KB, 891 views)
File Type: gif THD 1V.gif (34.2 KB, 881 views)
File Type: gif THD 4V.gif (31.5 KB, 887 views)
File Type: gif Anti-Presence-EQ.gif (32.0 KB, 893 views)
File Type: gif All controls -0.5.gif (31.1 KB, 884 views)
Attached Files
File Type: zip ZenEQ.zip (4.1 KB, 35 views)
  Reply With Quote
Old 28th March 2012, 07:10 PM   #19
Previously: Kuei Yang Wang
 
Join Date: Nov 2002
Hi,

Quote:
Originally Posted by Gopher View Post
There'll be 10 or so pages of this then it will fizzle out like the other thread.
That is probably my fault. I refuse "to lead" and to be the one who lays the down guru style on how it can only "one way, this way and no other". I'd rather people find THEIR way. Hence i gave many options and ways.

Anyway, what I can contribute for now is on the table. True, I assume that there will be some of the least common of all senses applied when using the circuit I suggest, no attempts to drive headphones directly off the output of the EQ and other such sillyness.

Anyone wants to do something Op-Amp based instead, on a similar level, please chip in...

Ciao T
  Reply With Quote
Old 28th March 2012, 07:32 PM   #20
diyAudio Member
 
Join Date: Dec 2004
Location: Bakersfield, CA
ThorstenL,

Please continue working up your FET & inductor solution. I've got a stash of suitable inductors leftover from the old days when I had an Auditronics 36 Grand mixing console. The EQ in that console was the reason that I kept it so long. I still have a stash of parts hoarded away. I have stash of FETs as well. If you complete the design I will be sure to build it.
__________________
Best Regards,
Carl Huff
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Cello Audio Palette Nrik Analog Line Level 70 6th January 2014 05:00 PM
Best chip for digital tone control in high-end preamp ? bongo1 Parts 11 18th June 2013 01:12 AM
High End Tone Control EUVL Analog Line Level 144 1st April 2012 06:11 PM
Tube eq or tone control - how to design it? marz.tv Tubes / Valves 5 20th July 2009 12:01 AM
Cello Palette voltage change? young_pup Solid State 3 27th September 2006 10:23 PM


New To Site? Need Help?

All times are GMT. The time now is 07:34 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright ©1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2