sontec 1 RU build thread

[Igor]

Hi Group!

I am having a strange problem with my Sontec and hopefully someone here can help. Everything is working ok except the HF band on the second channel. The band works but as the frequency control is turned more counter-clock-wise a hum develops. It's ok until about 6K but any more to the left and it gets bad. Flipping the Shape toggle to 12dB increases the hum even more. The pot is also a little scratchy to. I have checked connections and re-flowed the solder joints in that area but no luck. I have also swapped all the power and signal connectors with the other channel and I still get this problem. So i am pretty sure it is isolated to that board and band. Any help would be greatly appreciated!

Thanks, Charles

Front panel and gain, freq potentiometers should be grounded.
Power transformer can be the source for EMF. Try to move power transformer out of box
(be carefull, high voltages; good insulation on wires, attention, etc).

All EQ's I built are relatively quiet, if 0db is 1V RMS, at the input, test conditions - S/N, Boonton 1120, no filters,
the thrashy noise etc was always about or lower -80 db with all gains at 0 and EQ ON
(this way, filters outs are going to summing circuit).
With EQ switch off, I measured about -92...-98 db. In perfect lab conditions, maybe, it will be even better.

Ah yep. Trick: increase input signal till the EQ is 0.5 db below clip, you will get even better results, like some manufacturers do/claim in manuals

I have BTW some noise from somewhere on electricity at my workshop, it starts at the morning and goes about 2 at night... kill all humans!!!
T4 lamp on my workbench adds some noise, too - when it closed and it is night here, all measurements looks almost perfect. Well, OT.
Please post what was the noise source for HF.... just a human curiosity

 

[cstella]

Thanks Igor!

I will check the grounding and also report back on the noise. It sounds like a 60 cycle type hum. It is only present on the HF band of one channel though so it seems like it has to be something around there. The other channel is fine.

More soon!

Thanks, Charles

 

[peskado]

I had the same problem
made ground for front panel and pot
now it work perfect

 

[dagoose]

Most of the times if the frontpanel is not grounded is that because there is paint on both the panel as well as the case, which is quite a good isolator. So sand of the paint on the edges where your frontpanel touches the case and most of the times that is enough. Be aware that blank metal can/will oxidate after a while..

 

[cstella]

Thanks guys! I will try this for sure as soon as I can.

Best, Charles

 

[sedit1]

Hi,

I have a problem. Just finishing my sontec rev 1.7 black boards..I fired up the first channel but in filter pcb my c22 bypass cap stared to smoke up...
I cheked the orientation and the +24v coming from 22r rps4 resistor goes straight to c22 - minus polarity when the cap is connected like in the silkscreen...

So what am I missing here???

Thanks!

 

[sedit1]

Hi,

I have a problem. Just finishing my sontec rev 1.7 black boards..I fired up the first channel but in filter pcb my c22 bypass cap stared to smoke up...
I cheked the orientation and the +24v coming from 22r rps4 resistor goes straight to c22 - minus polarity when the cap is connected like in the silkscreen...

So what am I missing here???

Thanks!

Found the solution...It seems that In filter pcb the -24v/+24v have switched places if you just follow the silkscreen...Reminder to self always check the schematics..

 

[Igor]

Strange.... What revision of boards?

 

[sedit1]

Strange.... What revision of boards?

Hi Igor! The i/o pcb is Rev.1.6 and the filter pcb is rev.1.7. If you look at the silkschreen in i/o pcb (PS/PS2)there are markings G + - when you look at filter pcb the +- markings are reversed, G - +.

It might be that I'm missing something, not that experienced But got it worked out and the eq works great and the sound is amaizing!! Thanks for a great project!

 

[Igor]

Ah yep... the silkscreening was reversed, but pinout is correct. 1 goes to 1, 2 to 2, etc. Yes, this is one of my favorite EQ's too. Enjoy!

 

[Igor]

Most of the times if the frontpanel is not grounded is that because there is paint on both the panel as well as the case, which is quite a good isolator. So sand of the paint on the edges where your frontpanel touches the case and most of the times that is enough. Be aware that blank metal can/will oxidate after a while..

I soldering the wire from starground to one of pots, so, it works.
The cases I use have good contact between parts, front is always grounded like Butters, for SP fans.... so I had no this prob. But was interesting to read

 

[pieca]

Igor,
no more PCB in stock on your website?

 

[Igor]

What the heck! After we moved site to new faster hosting, things started to disappear!
Try this:
http://www.ij-audio.com/store/equalizers/sontec_pc/

 

[steki]

Hey guys, which ferrite bead for the FB 0R position instead of a jumper is the best for this project or is it indifferent what kind of ferrite I use?

 

[dogma]

Hi - I've emailed igor but have had no reply. I can't find the boards on his site nor on his white market page. I'm sure they where on his site a couple of weeks ago. I'm looking for a pcb for a stereo build. If igor or someone has or knows someone with some spare boards to sell please pm me or email me at thenewmandmshowAtgmailDOT.com - cheers, Matt

 

[druu]

I don't have boards but may have a complete EQ ready soon to sell, minus knobs possibly, if anyone is interested.

 

[andydiy]

Hi!

Ask the following ALPHASTAT, addition to the PS Potentiometer-Service GmbH something to buy, there are other places to buy it?

10x  50k CTPOT                                                                                                           
2207 RD1601-20F4-30R
ALPHASTAT 63250-01610/B50K 50K LIN CENTERTAPCENTERDETENT
10x 100K RLOG DUAL_ALPHA_2                                                                                   
4196 RD1602-20B4-30R
ALPHASTAT 63256-02600/C100K 100K REV-LOG

In addition, I want to buy Power Transformer, In Mouser company, Have one would be better Power Transformer?

My country is 220V.

Thank you!

 

[ptron]

Hi!

Ask the following ALPHASTAT, addition to the PS Potentiometer-Service GmbH something to buy, there are other places to buy it?

10x  50k CTPOT                                                                                                           
2207 RD1601-20F4-30R
ALPHASTAT 63250-01610/B50K 50K LIN CENTERTAPCENTERDETENT
10x 100K RLOG DUAL_ALPHA_2                                                                                   
4196 RD1602-20B4-30R
ALPHASTAT 63256-02600/C100K 100K REV-LOG

In addition, I want to buy Power Transformer, In Mouser company, Have one would be better Power Transformer?

My country is 220V.

Thank you!

I believe Alphastat is the only place to buy those pots... they are not standard stuff as u may know.

all the best!!

 

[andydiy]

Thank!

In addition, I want to buy Power Transformer, In Mouser company, Have one would be better Power Transformer?

My country is 220V.

Thank you!

Hi!

Ask the following ALPHASTAT, addition to the PS Potentiometer-Service GmbH something to buy, there are other places to buy it?

10x  50k CTPOT                                                                                                           
2207 RD1601-20F4-30R
ALPHASTAT 63250-01610/B50K 50K LIN CENTERTAPCENTERDETENT
10x 100K RLOG DUAL_ALPHA_2                                                                                   
4196 RD1602-20B4-30R
ALPHASTAT 63256-02600/C100K 100K REV-LOG

In addition, I want to buy Power Transformer, In Mouser company, Have one would be better Power Transformer?

My country is 220V.

Thank you!

I believe Alphastat is the only place to buy those pots... they are not standard stuff as u may know.

all the best!!

 

[andydiy]

Hi!

Someone can give me a complete BOM ?

If the to mouser best!

Thank !