Cello Palette Style EQ Design (was High End Tone Control)...

[EUVL]

Thorsten,

Do you think #37 will drive 11 bands, or do I need to have 6+5 bands (2 amps in series) ?

Could you kindly propose a filter portion for :
25, 50, 100, 200, 400, 800, 1600, 3200, 6300, 12500, 25000 Hz ?


Thanks,
Patrick

 

[ThorstenL]

Hi,

Do you think #37 will drive 11 bands, or do I need to have 6+5 bands (2 amps in series) ?

I would suggest changing the potentiometers to 22K, this way the actual load remains the same, even with greater numbers of bands.

Could you kindly propose a filter portion for :
25, 50, 100, 200, 400, 800, 1600, 3200, 6300, 12500, 25000 Hz ?

Sorry, but no time for that. Use LT-Spice or Tina-Ti and work it our...

Ciao T



Thanks,
Patrick[/QUOTE]

 

[danielwritesbac]

Attached the version with gyrators for the two LF bands where mouser does not stock suitable inductors.

Thank you for the examples!

However, I may have found the inductors, and that is the question.
1H series to 1H = 2H Murata Power Inductor
500mH Bourns RF Inductor

I wasn't asking if they're perfect, but rather I was asking if they're same or better performance than gyrators?

P.S.
Reference: wide parameters inductor search
P.P.S.
15hz??? Howabout ~35hz?

 

[EUVL]

> 1H series to 1H = 2H Murata Power Inductor
If the link was correct, then 100uH is perhaps not quite the same as 1H ??


Patrick

 

[danielwritesbac]

There was an error in the Mouser summary page. And, I am absolutely not familiar with shopping for signal inductors.

So four of the Bournes (500mh*4)?

Or, hopefully, if the lowest dial was changed to a valid audio band frequency, that repair would decrease inductor size.

 

[EUVL]

DCR of the Bourns 500mH is 736R. 4 in series gives about 3k.
Quite a bit higher than the 120R required.

Gyrator or special-order inductor it will be, I am afraid.


Patrick

 

[ThorstenL]

Hi,

However, I may have found the inductors, and that is the question.

....

I wasn't asking if they're perfect, but rather I was asking if they're same or better performance than gyrators?

The DCR is too high. You may be able to find suitable inductors (or get them made) on the pages of people like Sowter Transformers.

Tamura used to make large value variable inductors for supposedly some video application, these would work but are likely discontinued and even when available they where very hard to get (AFAIK only Sound Shop Big in Tokyo).

15hz??? Howabout ~35hz?

Your call. If you have a look at the curves you will notice the bass boost is quite broadband, up to very boost levels. Do not mistake this design for a common graphic EQ.

Ciao T

 

[EUVL]

Since we use the name Cello Palette in the title, this is what the original article does :

"The top row of six knobs is dedicated to basic preamplifier operation (input selection, tape monitor, left and right input balance, EQ in/out, and output level), with the lower six knobs reserved for selected equalization points: up to ±22dB at 20Hz, ±12dB at 120Hz, ±6dB at 500Hz, ±6dB at 2kHz, ±12dB at 5kHz, and ±22dB at 20kHz."

Not that we have to copy 1:1.


Patrick

 

[ThorstenL]

Hi Patrick,

Since we use the name Cello Palette in the title, this is what the original article does :

"The top row of six knobs is dedicated to basic preamplifier operation (input selection, tape monitor, left and right input balance, EQ in/out, and output level), with the lower six knobs reserved for selected equalization points: up to ±22dB at 20Hz, ±12dB at 120Hz, ±6dB at 500Hz, ±6dB at 2kHz, ±12dB at 5kHz, and ±22dB at 20kHz."

This is what the lower grade Cello Palette Preamp reviewed by Stereophile does.

My specs are more or less based on the original Audio Palette, which is rather more "High End"...

Frequency Adjustments:
25kHz control: +/- 24dB in 1.00dB increments
5kHz control: +/- 12dB in 0.50dB increments
2kHz control: +/- 6dB in 0.25dB increments
500Hz control: +/- 6dB in 0.25dB increments
120Hz control: +/- 14.5dB in 0.50dB increments
15Hz control: +/- 29dB in 1.00dB increments

The manual for that one is here:

http://www.matthew-james.net/Customer-Content/WWW/CMS/files/audio-palette-owner-miv.pdf

Of course, anyone wanting to run with these bare bones and wanting to turn this into a full formal project is welcome to mod my specs.

What I presented was simply meant to illustrate what sort of results a very simple topology could give, compared complex, ten-thousand Op-Amp gizmo's and the like (the objective performance is quite acceptable I think).

Ciao T

 

[PierreQuiRoule]

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.

Thank you .

 

[ChicagoJTW]

What about smaller inductors in series? Any reason why that wouldn't work? Using gyrators for two out of seven bands kind of fouls up the layout.

 

[PierreQuiRoule]

[...] for my own use I'd probably build this:

and thanks again .

 

[danielwritesbac]

Triad has a 1H inductor transformer available. Maybe it would work if one chose a sensible bass control like 30hz to 45hz?

 

[jameshillj]

..."sensible bass control" You've missed the point, I'm afraid - this is a "Cello Style Eq Design" not your "common garden variety" tone controls and the filters are set for a different purpose.

You can design your own particular filters, you know, or perhaps do your own mods to this one when it gets to completion - there'll be others looking for a similar 35Hz low bass turnover point, I'm sure - might even try it myself!.

 

[ThorstenL]

Hi,

Triad has a 1H inductor transformer available. Maybe it would work if one chose a sensible bass control like 30hz to 45hz?

This type of inductor is intended for power supplies. It may not work very well in our circuit.

Ciao T

 

[KSTR]

What about smaller inductors in series? Any reason why that wouldn't work? Using gyrators for two out of seven bands kind of fouls up the layout.

Series'd inductors is quite ineffective, with the same core and winding volume you can have 4x the inductance when it's a single coupled inductor instead of two decoupled ones adding only to 2x.

Lundahl have a "RIAA" inductor that would give 1.8H with series connected coils, but that'll be expensive

 

[ChicagoJTW]

You can design your own particular filters, you know, or perhaps do your own mods to this one when it gets to completion

I think the point is if there aren't any inductors available at a reasonable size and price, there will be no completion. The whole point of this design, it seems, is to use passive parts for highest sound quality. But the scarcest passive part is the large signal inductor, upon which it completely relies. We're just trying to find out if the bass band components are even available.

 

[kevinkr]

Cinemag makes (made) a variety of audio inductors and were there to be a group buy with sufficient quantities I suppose they might be interested in making the inductors for this project.

 

[EUVL]

What's wrong with gyrators for 15Hz and 120Hz ?

Patrick

 

[Dirk95100]

Instead of gyrators you can use a general impedance converter.

General Impedance Converter