sontec 1 RU build thread

can other pots be used on this project besides alpha? for U.S. ?

I've got a quick question. I've got the 4k7 on the underside of the board so I can have 12dB boost/cut, but I'm only getting 6dB boost/cut.

I've made sure I've got 4k7's in there, and I've even tried lower and higher values on there. The most I can get is 9dB boost/cut with a wire bridge connection.

I've compared to my trident EQ and even to my plugin EQ's, and they're giving me the amount of boost they're telling me.

It's the same on both channels of the sontec...... so besides the 4k7 area, what else should I be looking at to resolve the problem?

There may be some issues like:

- Check if the GAIN pots are 50k, lin, centertap;
- Check the summing resistors R18-R22 are 20k and r21 is 10k;
- Check the values of CLF1/2, CLMF1/2, etc, they should be in 5% range.

Check for mistakes, wrong placed components, etc. If gain pots are 50k, they should give +/-12db with 4k7.

Thanks for sending the boards Igor, the build is humming along!
Wondering... What are the three small boards attached to the I/O board for? I looked back in the forum archives but didn't see anything. Many thanks!

Put them below the switches mounted on PCB, if using case from Purusha.

Hi there.

I am looking forward to this build. The boards are on the way and I have managed to secure most of the parts.

I have a question about the power transformer. Would 30VA suffice for +/-24V As I am thinking of getting this one from Hairball.

http://hairballaudio.com/shop/product_info.php?products_id=37&osCsid=9f5e8f09df1061774567eb8d0b4432cd

Any help is greatly appreciated.

Thanks, Charles

Project looking excelent

Molex: Is that Mini-Fit?
http://www.molex.com/molex/products/group?key=minifit_products&channel=products

Hey guys,

I had a 50k pot disintigrate on me.

Anyone got a spare or two I could purchase?

Thanks,

mm

Greetings!
I seem to have an interesting problem with my Sontec. Everything is working as advertised EXCEPT that the boost/cut volume will change depending on the Q setting  I've ran a signal through it and into a spectrograph and the wider the Q setting, the lower the bell is. I don't get it. Anyone know what may be causing this?? I have wired this EQ as a mastering EQ with all stepped switches (24 position for gain and freq, 6 for Q) and have not cut the board as others have done. I'm stumped with this one.. any help would be appreciated!

Aha.... I think I debunked my problem. Checking the resistors around the Q pot, I found that RF*.2 (1.2, 2.2 ect...) was 54.9OHM, not 54.9K!! ( I couldn't find a 55, so I ordered a 49.5). I'll have to pick up some resistors tomorrow and swap them out to see if that's the only problem, but it looks like it is. I'll post results.

Hey Mark.

Interesting seeing your post this morning as I just started putting the PS together. I got the hairball transformer which I think should be fine too.

I also bought those heat sinks in the BOM from Mouser. I ended up mounting the 100UF's on the bottom of the board and have the heat sinks slightly off the board so they make no contact with any parts. This is working well and my standoffs are a little taller than the caps on the bottom.

I just checked my DOA pins and they are the .062's from Mouser #575-034420. They do fit into those holes.

Looking forward to finishing this up. Just waiting on the pots from Alphastat.

Good luck on your build!

Charles

For what it's worth, these are the TO-220 Heatsinks I ordered. Fit perfectly on The PS Board
Mouser: 567-637-10ABP

Hi! I would like to ask a (maybe silly) question: In the BOM says resistors
10x 1m
1x  2m
1x 3m9    Are Mega or mili ohms? Should be 1/4 Watt or any other Watt can do the job?.....maybe a mouser code?
For 55k can i use 20k and 35k in series?

gda said:

Hi! I would like to ask a (maybe silly) question: In the BOM says resistors
10x 1m
1x  2m
1x 3m9    Are Mega or mili ohms? Should be 1/4 Watt or any other Watt can do the job?.....maybe a mouser code?
For 55k can i use 20k and 35k in series?

Click to expand...

Welcome,

- Mega 1/4  1%

- Of course

Hey guys,

I've finally got arround to putting together this eq and on first power-up, voltage tested good at PS output (+/- 23.9). But when I connect the PS to output boards, RPS3(22r) smoked on one channel only.  (btw, I have red boards)

(I read the post about "inversed PS polarity output" but that seems odd to me)

Anyone have any thoughts? ???

Sylvain D. said:

Hey guys,

I've finally got arround to putting together this eq and on first power-up, voltage tested good at PS output (+/- 23.9). But when I connect the PS to output boards, RPS3(22r) smoked on one channel only.  (btw, I have red boards)

(I read the post about "inversed PS polarity output" but that seems odd to me)

Anyone have any thoughts? ???

Click to expand...

I don't know what's that inversed polarity thing...
just make sure you have positive rail wired to the positive PS input of all the other boards, same for Negative and voila... EDIT: and Grounds of course...
Follow PCB traces if you have a doubt...

pH said:

Wired up my first channel and got smoke from the 22R resistors, it seems the PSU markings on the filter board have + and - reversed. Once I traced through the schematic and hooked it up correctly all is fine.

Great EQ! Amazing level of precision.

Click to expand...

I was refering to the post above on page 4.

But, merçi Zayance.  I will take a closer look.

Got it!!

I had reversed one of the +/- pairs going from the PS to one of the I/O boards.
One of those late nite solder sessions... I should have gone to bed earlier. ;D

All of my opamps are OPA2604 or OPA604. My transformer is 2x25Volt, 30VA.
Should Rx 3k6 be fine?
My transformer has red, orange, black, yellow wires (which as mentioned are going straight on the suply board) and one black and one brown. Are they going on the main switch and from the switch straight to the 220Volt socket? What about fuse? should I use one and how should I connect it?
What about grounds? As you understand I have problems with the "outboard wiring"...it's my first "big" project....please help! Thank you a lot!You really helped me a lot with all your posts guys...be well!

Does this in the bom mean I can either run it:

with 1 X ad706 OR OPA2604(24V PS) 'CAN BE OTHER LOW OFFSET DUAL OPAMP,

OR

2 X times OPA604 OR JE990 ETC 'CAN BE OTHER LOW DIST FAST HIGH CURRENT OPAMP,

OR

5 X OPA2604 OR OP275 ETC 'CAN BE OTHER LOW DIST FAST DUAL OPAMP

?

What are my benefits with each setup?