sontec 1 RU build thread

[Igor]

Regarding stepped gain controls.
Use less resistance at center, i.e. kinda S-curved control for
exact db steps.
I.e. 2k7-2k7-2k4-2k4-2k2-2k2-2k-1k8-1k5-1k3/0/-1k3-1k5-1k8-.....2k7.

Added:

BTW, what is the deal with uraltone switches?

6 positions for Q is enough/IMHO
Take a look at Mass***9500.
This way, you can have 2x6 pos switch for low shelve etc.
Q is kinda "lin" pot, 10x499r, or 5x1k, or 4x1k27 is fine there.

I used rev-log pot calculator for first stepped Sontec, then, the values were bit changed,
gigathanx to my friend Charles for his ears and guys from Bardo and Hook&High mastering studios
who working with my gadgets some years.
http://www.hooknhigh.co.il/english/index.html
http://www.bardostudios.co.il/studios/mastering

 

[dagoose]

Thanks Igor,

It is indeed really that simple when i look at it this way.
The Q will be 11 steps, not much more work then 6 steps but i think that 6 is indeed enough but i want to fill the steps on the panel.
I was thinking that for the low shelf i need a 2 deck switch, 1 deck for resistors and the other deck lowest position for the low shelf/peak switching.

I got the 'uraltones' 24x2 for 8,15 euro's each.
They don't have the feel of a elma indeed but they are almost a 10th of the price of an elma!

 

[zayance]

I got the 'uraltones' 24x2 for 8,15 euro's each.

The seller on ebay, got me those for 7.5dollars  , that makes them for about 6euros, that was the price break for 20 pots order when i asked.

BTW, what is the deal with uraltone switches?

Mine are not from uraltone but that's what it is:

http://cgi.ebay.com/1-PC-Selector-Switch-24-step-2-pole-Attenuator-Pot-New-/270581450882?cmd=ViewItem&pt=LH_DefaultDomain_0&hash=item3effe94882#ht_603wt_1138

 

[MrShhh]

Regarding stepped gain controls.
Use less resistance at center, i.e. kinda S-curved control for
exact db steps.
I.e. 2k7-2k7-2k4-2k4-2k2-2k2-2k-1k8-1k5-1k3/0/-1k3-1k5-1k8-.....2k7.

Does anybody have the formulas for working out the above resistance curve? Is it a standard kind of log curve or something else specific to this eq?

 

[Pieter001]

Hello,

Im ordering the parts for the sontec right now but don't understand something from the Bom.

1 rx+ 3k6 2% for 24v
1 rx- 3k6 2% for 24v

(200R/1.25V)=(Rx/(Ux-1.25V))
Rx in Ohms

What are the right value i need to order?
3k6?

Pieter

 

[Harpo]

Im ordering the parts for the sontec right now but don't understand something from the Bom.

1 rx+ 3k6 2% for 24v
1 rx- 3k6 2% for 24v

(200R/1.25V)=(Rx/(Ux-1.25V))
Rx in Ohms

What are the right value i need to order?
3k6?

depending on what supply voltage your opamps can take

http://www.groupdiy.com/index.php?topic=27972.msg403084#msg403084

Your chips might only stand +/-18V or +/-22V, so you can rescale the needed value from 3K6 for +/-24V to the allowed supply voltage for your opamps.

 

[Pieter001]

Thanks for the reply. Didnt see the post back in the thread.

 

[dagoose]

Did some calculating and things for the switches and i come up with 21 steps which is nice becaus eon the gain you have 10x up and 10x down and step 11 = 0
I'm wondering concerning the freq switches, why is it that the high shelf switch has different values for the resistors then the other switches when you calculate them?
Is it because of the highest freq for shelf will be to high if you use the same values? step 21 is 365r with low/mid/hi but with the shelf the value is 576r.

I came up with this for thefreq pots/switches.

FREQ band = 101k total

1
20k
2
15k4
3
12k4
4
10k5
5
8k25
6
6k8
7
5k36
8
4k64
9
3k6
10
2k94
11
2k4
12
1k96
13
1k54
14
1k3
15
1k07
16
820r
17
681r
18
560r
19
442r
20
360r
21


Gain switches 48k2 total amount

1 -12db
3k9
2
3k3
3
3k
4
2k7
5
2k4
6
2k2
7
2k
8
1k8
9
1k5
10
1k3
11 MID position =0
1k3
12
1k5
13
1k8
14
2k
15
2k2
16
2k4
17
2k7
18
3k
19
3k3
20
3k9
21 +12db

 

[Harpo]

Did some calculating and things for the switches and i come up with 21 steps which is nice becaus eon the gain you have 10x up and 10x down and step 11 = 0
I'm wondering concerning the freq switches, why is it that the high shelf switch has different values for the resistors then the other switches when you calculate them?
Is it because of the highest freq for shelf will be to high if you use the same values? step 21 is 365r with low/mid/hi but with the shelf the value is 576r.

Different frequency ratio between lowest and highest position for your high band.
For your resistor values, I only had them calculated for E96 and E48 type resistors. Anything lower values per row ie.E12 or E24 would have to use a lookup table for historical reasons.

 

[dagoose]

Did some calculating and things for the switches and i come up with 21 steps which is nice becaus eon the gain you have 10x up and 10x down and step 11 = 0
I'm wondering concerning the freq switches, why is it that the high shelf switch has different values for the resistors then the other switches when you calculate them?
Is it because of the highest freq for shelf will be to high if you use the same values? step 21 is 365r with low/mid/hi but with the shelf the value is 576r.

Different frequency ratio between lowest and highest position for your high band.
For your resistor values, I only had them calculated for E96 and E48 type resistors. Anything lower values per row ie.E12 or E24 would have to use a lookup table for historical reasons.

OK, what i expected indeed.
Concerning the values, i just went trough all values at RS and picked the closest values to the original calculation. ok.. i skipped some because i don't need 5000 x one value.  ;D
I came pretty close to the values compared to the excell sheet!
Now up for some soldering when the switches and R's  come in, i think about 800 resistors? pure zen.  :-*

 

[dagoose]

Today i had a better look at the filterboard concerning chopping it up and it's quite easy and will turn out quite nicely i guess.

The 2x low band are real easy to chop apart so that you have 2 boards for the low bands that i can mount vertically near the switches which is really nice.
Then you have the 2x mid/high section with the main inputs/outputs/psu and they are not 'cutable' without messing up the board so these have to stay together as one board. Then the hi shelf is also quite easy, only thing is that the 10k summing resistor 'has to go' because that is where the board is going to be cut but that is just a matter of moving it somewhere else. The summing resistors will all have 2 values for a 12/6db gain switch so that had to be modded anyway.
That gives 4 filterboards in total and the mid/high baord will still be the mainboard where all connctions are made and then the 2x low and 1x hishelf board will have their connections  made to the 'mainboard'.

The panel is going to be great! Peter/grandmaster audio is working on it, pretty much excited about this!
Now for some nice knobs.. i think big metal knobs but not sure yet.  ;D

 

[dagoose]

i couldn't resist, a glimpse of the frontpanel.

 

[zayance]

Looking good 

 

[muffy1975]

Dear Igor and Team Sontec EQ,

my dual eq worked 1st time. No hum ( gosh it's quiet ) just a great signal.

My only concern are the rails. The + rail = 24.2V and the - rail = -23.6V.

Is this OK team? I believe I put two equal 3.6k resistors in the PSU. Is this what I need to change to get them both at 24v ish?

Regards and many smiles

Michael de Albuquerque
Oxford
England

 

[dagoose]

I don't think it will do any harm but what you can do is use a trimpot instead of the 3k6 resistor so that you trim them both to 24v.

 

[haima]

i wouldn't worry about it Michael - it will surely be of little consequence IMHO.

congrats on the working build!

 

[MrShhh]

Hey dagoose, how would I go about calculating the gain switch values if I want to use 23 positions instead of your 21? I had all the switches soldered up in linear fashion with 2k2 resistors which of course, does not work as intended (nothing's ever as simple as it seems!) Thank you!

 

[kambo]

i am back people.. 
super busy lately...

MrShhh : check back some pages... there were detailed info on switches....

 

[dagoose]

Concerning modding the 24 steps 'uraltone' switches, check here. http://www.groupdiy.com/index.php?topic=40384.0

 

[electrisizer]

high guys!
is there another (perhaps german) order option for the 5k lin pot sw and the 5k lin pot?

im not in the USA.

does it matter how much "watt" the pots have or could i even take some with more watt?

thanks