sontec 1 RU build thread

[Igor]

Hi, for stereo Sontec, it comes up in range $450-800 depending on parts, case, shipping costs.
$800 is a bit over-estimated btw.

Opamp options.
The best IMHO are OPA604/2604. Clean, fast, no harsh at any frequency. Fine on +/-24V.
With power supply +/-18V, it is possible to use OP275, NE5532 in filters,
and NE5534, etc. in input/summing board.
To add really nice character, use fast Forssel's opamps in summing circuit.

 

[mcfarlane_audio]

has anyone built one of these sontecs with switches instead of pots? like on the pcbs fabio was selling? is this essentially the same circuit?

thanks !!

 

[Igor]

Hi, I built some of these Sontecs with stepped control.
Here's mastering studio where these EQ's are most prefereable favorite:
http://www.bardostudios.co.il/mastering/eng/
(just "refresh" to watch flash from start)
IMHO this PCB layout has better finnish and easy diy-able, what I can't say
from first glance at Fabio's pcb's...bit rough design...but maybe it is wrong mind.
The circuit is not essentially same.
After listening ITI, MEP230, and 8200, making some clones and comparing etc.,
I got to mind 8200 filter's are more flexible,
but by sound, op-amps are not as fast as Forssewl's or opa604's....
I did not liked high shelve, tried some circuits on breadboard again,
some of my friends listened to this, finally, shelve came from
Neumann/crossfaded with my design 2nd order 12db/oct resonant hi-shelve.
This EQ was designed more by ears...but with use of good measurement 'quippment...
btw, 16 of same design eq's are working on my design mixing console; at design stage, they
were preferred to many other's commercial products and test proto's.

 

[mcfarlane_audio]

Hello igor, im wondering if the "shape" on prushas case is just arbitrarily labeled, or is it actually .4 to 4......... i dont think this can be bandwith or db/oct, and Q would be the opposite.....so is it just an arbitrarily labeled?

Thanks so much, also im wiring mine up with switches everywhere, and am wondering how i should wire up the switch on the low shape control ? ill most likely need a 2 deck switch and just have that last position connect the 2 solder points on the rear of the pot/pcb board connector (on either side of the word "log" on the pcb? yes?

let me know if i dont make any sense

thanks so much! pics coming soon

 

[Igor]

so is it just an arbitrarily labeled?

I think yes. Take a look on front of 8200

wiring mine up with switches everywhere, and am wondering how i should wire up the switch on the low shape control ?
ill most likely need a 2 deck switch and just have that last position connect the 2 solder points on the rear of the pot/pcb
board connector

Yes, it is quite simple: pos.1 is ccw, pos.11 is cw of switch.

First waffer, solder 10x499R resistors (1-res-2-res-3-res......res-11)
Second waffer, connect 2 thru 11, solder'em to one point of switch, wipper to second point of switch.

Roboporn always wellcome.

 

[mcfarlane_audio]

hello, im working on my sontec right now, and aqm about to start building the switches, for the reverse log pot (switches) im just double checking before i start soldering tons of switches that im correct in my method

so in ccw - i will start with my highest value, with the last position being the lowest value followed by a jumper on step 24

basically i have used silent arts' log switch excel calculator and reversed the values

here is what i think is correct

for 100k dual rev log (freq for sontec)

ccw

1 - 10k5
2 - 9k53
3 - 8k66
4 - 7k87
5 - 7k15
6 - 6k49
7 - 5k76
8 - 5k23
9 - 4k75
10-4k23
11-3k92
12-3k48
13-3k16
14-2k87
15-2k61
16-2k37
17-2k15
18-1k91
19-1k74
20-1k58
21-1k43
22-1k30
23-1k18
24-jumper

cw
and the second deck will be exactly the same

correct?? thaks so much!

the other ones are easy, its the total value of "pot" / total # of positions-1 correct??

then igor has already explained the "q" switch part

thanks in advance for your help, ill post some pics soon

 

[dagoose]

hello, im working on my sontec right now, and aqm about to start building the switches, for the reverse log pot (switches) im just double checking before i start soldering tons of switches that im correct in my method

so in ccw - i will start with my highest value, with the last position being the lowest value followed by a jumper on step 24

basically i have used silent arts' log switch excel calculator and reversed the values

here is what i think is correct

for 100k dual rev log (freq for sontec)

ccw

1 - 10k5
2 - 9k53
3 - 8k66
4 - 7k87
5 - 7k15
6 - 6k49
7 - 5k76
8 - 5k23
9 - 4k75
10-4k23
11-3k92
12-3k48
13-3k16
14-2k87
15-2k61
16-2k37
17-2k15
18-1k91
19-1k74
20-1k58
21-1k43
22-1k30
23-1k18
24-jumper

cw
and the second deck will be exactly the same

correct?? thaks so much!

the other ones are easy, its the total value of "pot" / total # of positions-1 correct??

then igor has already explained the "q" switch part

thanks in advance for your help, ill post some pics soon

Cool! That is one of the things i'd still like to do with my sontec, stepped switches!
Post those pics man and let us know how the switches work out and stuff like that. 

 

[mcfarlane_audio]

thanks ill let you know, im going to start wiring as soon as someone tells me im not an *****, im 98% sure this is right but im not 100% and dont want to have to desolder 780 resistors!

im going to start a new thread one i get into full bore on the project so keep an eye out, do these calculations seem correct to you??

ill post all the calculations and resistors and parts once i have that thread goin

my big thanks is to igor for his support so far and for making this project possible for us!!

 

[Harpo]

maybe a matter of taste, but the center frequency distance between steps at the cw end seems a little large. Have a look at my Sontec calculator to get the idea. (I added your resistor values, starting at cell T53 just for comparisons sake)

good luck

 

[mcfarlane_audio]

all hail harpo!

thank you thank you thank you, this is most exciting, and some amazing math, thank you thank you thank you, i cant say that enough, you are competely correct, it seemed as though the steps got silly at that end , so this is just great, ill post results soon!!!



THANK YOU! and damn this new forum for no beer emoticons, trust me you deserve a flat!

 

[raffaelebonetti]

Hi, for stereo Sontec, it comes up in range $450-800 depending on parts, case, shipping costs.
$800 is a bit over-estimated btw.

Opamp options.
The best IMHO are OPA604/2604. Clean, fast, no harsh at any frequency. Fine on +/-24V.
With power supply +/-18V, it is possible to use OP275, NE5532 in filters,
and NE5534, etc. in input/summing board.
To add really nice character, use fast Forssel's opamps in summing circuit.

Hello Igor!
What about AD706 vs OPA2604?

Cheers!
Raffaele

 

[SJakobsen]

Hi,
in the BOM there is 4-55k resistors, where to buy them?
55k isn't a standard value, is it okay to use 54k9?

Best Regards

Soeren

 

[Harpo]

55k isn't a standard value, is it okay to use 54k9?

Difference between these is 0.18%. Don't care.

 

[mcfarlane_audio]

OK im making excellent progress, well i have switch #1 wired, i guess thats progress, 27 to go!!

but im taking breaks to finish the pcb, i have 2 questions

im a little confused about the rx resistors in the power supply, im using 2604's and 604's so i want 24 volts but what is Ux? in the equation

also ther is talk but i see pics of people using AND NOT using cf1.2, cf2.2,cf3.2 and leaving cf4.2 and 5.2?? should i wore these or not??

thanks for your help, roboporn soon

 

[Harpo]

im a little confused about the rx resistors in the power supply, im using 2604's and 604's so i want 24 volts but what is Ux? in the equation

Ux=24V in your case.
With current setting resistor 200R and 3K6 for Rx you get 1.25V*(1+3600/200) = 23.75V. Have a look at the LM317/337 datasheet for a 2nd safetybelt.
These 5pF caps for lead compensation look a little pointless. (only checking the HF band, LPF -3dB @ 1/(2*PI()*11000*5*10^-12)=2.9MHz. A 47pF might fit better if the amp oscillates without. YMMV)

 

[mcfarlane_audio]

wow thanks again, looking at it now it all makes sense i thought the BOM was saying rx value minus 3k6 and rx value plus 3k6.


aaaaanyways its all good




back to soldering!

 

[mcfarlane_audio]

every pic i see of the guts seems to tell me that everyone is using the same toroid i was thinking a 48vct at about 40va would do, what are you guys using? is that a case/shield i see around the toroid?

Thanks for all the help guys, i really appreciate it

 

[raffaelebonetti]

Hello Everyone,

I am very confused on what transformer to buy for this project. I will be powering one dual channel unit. Can someone refer to an ideal transformer from Newark or any other company!

Thanks and Cheers!
Raffaele

 

[penguin]

Hi, new to here, so hello to everyone.
i need little help on bom

i was wondering using TANTALLUM caps as suggested on bom, for

33U CPOL-EUE5-6  25-50V HIGH QUALITY TANTALLUM caps.
there are only 8 of them on stereo so, it wont kill me

there are so many to choose fom, and many different fitings. any idea which ones to use,,

and i am ok on using below opamps...?


INPUT opamp: IC8
DLR-1 Differential Line Receiver (no longer available)  so i will use
JE-990 or 992

OUTPUT opamp:IC6
JFET-993 Discrete Opamp.


which type of resistors are the best to get better performance ?



thank you

 

[Igor]

33U CPOL-EUE5-6  25-50V HIGH QUALITY TANTALLUM caps.
there are only 8 of them on stereo so, it wont kill me

33uF, 2.5-6mm pitch, radial leaded, 25-35V will be fine.
Depends on supplier which is better for you (shipping, price, availability, etc.)
Audio quality Panasonic, Philips, etc electrolyt's will be fine as well.

INPUT opamp: IC8
DLR-1 Differential Line Receiver (no longer available)
so i will use
JE-990 or 992

OUTPUT opamp:IC6
JFET-993 Discrete Opamp.

Good combination IMHO: opa604 for input line receiver and 993 for summing,
opa2604 for dc servo.

which type of resistors are the best to get better performance ?

Hm....from point of view of audiofoollery, Roederstein, Dale Velvet,  0.1 % or something like this.
Practically, metal film resistors, 1%, 1/4W will work fine