sontec 1 RU build thread

[Igor]

Hi people, I updated second post of this thread, in case of whatever:

HERE YOU CAN FIND ALL DOCS:

http://twin-x.com/groupdiy/thumbnails.php?album=399

 

[haima]

awesome! thanks igor 

 

[boji]

MrZpliff
Best way of running the Calrec EQ unbalanced ?
« on: March 07, 2008, 06:02:56 pm » Quote  
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Hi !
What's the best way to run Gyraf's DIY version of the Calrec EQ unbalanced. Me think's disconnect pin 3 on both input and output and just connect pin 2(+) and ground.  :?
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gyraf Reply
Ground -input, leave -output floating..

Sontec seems to be the opposite of this, correct?
Which is to say the sontec8 is built to be unbalanced out...

 

[Igor]

Exactly. Instead of adding balanced line driver running at +/-18V max, I left it unbalanced.
This EQ runs on +/-24V, and there's a plenty of headroom.

From the other side, I personally prefer gear with high power supply rails, balanced input and
"balanced-ground-compensated" output, like here.
You can add output transformer to Sontec to make output balanced, it is easy.
JT-11 (IIRC) should work fine here as well as any other 1:1 or 11...2) ratio trunny.

 

[boji]

Thanks Igor for the feedback!

 

[xarolium]

Dear diyer,

i would like to know if i could use this DAO http://www.audiophonics.fr/burson-audio-opamp-aop-simple-p-3715.html for the output and input stage or which other DAO could i use?

thank you

 

[Igor]

You mean, DOA (Dead On Arrival or Discrete-Op-Amp), right?

Can't read french, but this opamp seems have different pinout than 990* etc.
I like OPA604 at input stage and fast Fred Forssel's opamp (993) at summing circuit.

 

[RedNoise]

Isn't this Burson a DIP8 pin compatible?

 

[Harpo]

compatible in DIL8 configuration for some chips maybe, but dimensions 48 x 22 x 24 mm ?
At least you'll have to cut some windows in your 1HE case lid to make them fit thru. Not reliable, but might look funny with the DOA ends sticking out like a tube amp ... : 
(Why can't they give some chip data, at least say being bipolar or fet type DOAs)

 

[RedNoise]

might look funny with the DOA ends sticking out like a tube amp ... : 

;D ;D ;D

 

[Igor]

I'd stay out of company selling gold-plated USB cables.
/just kidding/

Nice looking op-amp, but useless here.

 

[king-rb]

is it posible to get the boost/cut to 5db? i know the values for 6db but im not sure if the best way is to decrease r18-r21 or rf1c aso.. + rf18 aso..

 

[Igor]

It is possible to increase R18...R22 to 47k, r21 to 22k (closer standard values).

 

[bobine]

A new EQ was born today...

Aside from a few bad solder joints in a couple of bands and a ground problem to fix with the freq pots, everything works on paper:

(shouldn't the overall gain remain at the baseline when a band is raised or lowered?)

But it sounds terrible...when the gain goes above +9 it suddenly sounds like a ring modulator...both channels, every band. In this pic, the green is just before distortion and the others just after. Weird.

Edit: It sounds great. I changed the source and lowered the input levels and now the unit is behaving...I was apparently overdriving something when I raised band gain levels... not sure where since the output levels always seemed fine. ???  End Edit.

I used OPA604s for input & summing and OPA2604s elsewhere.
Anyone else have this happen? I may try limiting the gain to +6 to avoid this if cleaning up the ground problems doesn't fix it.

Otherwise, this was a lot of fun to build and play with...  

 

[dagoose]

Just wondering, what would be the ideal DOA's for this sontec?
I already have one running with opa's but i'm going to build another one now with stepped switches and DOA's.
So... what (DIY prefered) DOA's are the best to use?

 

[haima]

i think igor likes the forssell 993...

(me is a big fan of Forssell newer fast (993) opamps,
I think they UNBEATABLE by any other amplifier in this Sontec).
They are ideal opamps with very nice color.

 

[Igor]

Hi Bobine, the graphs looks a bit strange for me. The overall gain should not change when boosting/cuting. And, seems like an oscillation at >15k? Let me know which soft was used to take these graphs,  and maybe it is good to put it on scope. I don't trust to soundcard-based analyzers Let us know if everything works fine after the fix.

Ultimate op-amp. Forssell's 993 is a cherry at summing circuit, IMHO.

 

[dagoose]

Yep, forsell 993's it will be
OK.. now trying to find some decent 24 steps switches, elma's will be a 'bit' expensive maybe, i need 20. 

 

[zayance]

I bought 20 chinese stepped attenuator on ebay for my Sontec the dealers name is hampton if i remember correctly, got me a good price for them, they are Vishay i believe.
Seems like we will be building same sontec, i went for forsell also ;-)

 

[Holger]

My third:

I can really recommend this EQ. Jump on this as long as Igor stocks it...