sontec 1 RU build thread

Igor · Dec 3, 2008

Hi Kevin, please check your e-mail.
JLM opamps are no good for Sontec.
They can be good for other things,
but not here. Or, Sontec will need some mods.
If you want discrete, use Forsselltech DLR and 993.

OK, he sent me a schematic for his MEP 250 (A)
I was checking over the filters & noticed none of the values match the ones in your clone.
Now, I know there are different revisions of this EQ BUT which Version is yours the closest to or derived from :?:

Please see on schematic

khstudio · Dec 3, 2008

Igor,
I've been talking about using the JLM 99v's for Month's... why not warn me earlier???

I really like the sound of the 99v's on the output & really can't afford to spend over $150 MORE for the 993's right now.

So... HOW can I or SHOULD I mod it to work???

It CAN"T be that much trouble... that's why I asked you. I can't believe your only advise is:

Put opa604's or Forssell's 993.

Best Regards, Igor.

Come on man.

Also,
I don't understand your response about what "Version" or model this came from?
You said:

Please see on schematic Smiley

I don't get it.

delaymix · Dec 3, 2008

Igor,

Can you explain the differences in practice between DLR and a 990?
Thanks.

khstudio · Dec 3, 2008

I found these topics:

Sontec x 8 Build Thread:
http://www.groupdiy.com/index.php?topic=28215.msg340724#msg340724

I this thread, the guy mentioned using 99v's & Igor never mentions it being a problem... nor did the poster, or did he mention any DC on the output... maybe he didn't measure it???

Sontec Website:
http://www.groupdiy.com/index.php?topic=19895.msg234792#msg234792

This thread mentions using the 99v -

I know DrPat used 99v's for his "Real" Sontec's output & liked them a lot... but he was using & slightly modified Servo circuit.
He was the one that told me how KILLER they sounded on the output of this circuit & recommended me to get them, so I did.

I'm good friends with Pat but he's been busy mixing in LA for a few weeks & I can't reach him.

Also, Igor's AMP Section (& Servo setup) is a little different than the original which is the reason I'm asking HIM what to do.

Joe from JLM has emailed me a few times with regards to the 99v's & this circuits DC Servo but I'm still left confused. :-[

Here was the last email with Joe:

HI Kevin

Thank you soooo much man!
[Joe]

I will be posting this info on the "Sontec Help" thread to help others
too!!!!
[Joe] ok

OK,
I'm not questioning your 1st email... I'm just not sure if we're just
"patching" a wrong design???
[Joe] No the design is fine for small mV offset opamps. Just that the 99v
has a couple of volts offset.

#1 - do you even recommend a DC Servo with your 99v - because the offset
is so high?
[Joe] No the DC servo is fine. I am just not a big fan of DC servo unless it
has a very low time constant so it doesn't interfere with the low end.

(Or should I just use a Cap on the output???)

[Joe] If you want to use no DC servo you would be best to use an output cap
from the opamp output as well as a second output cap from the opamp output
to feed the EQ bands.

#2 - are the recommendations you gave me optimal... or would YOU set it
up differently?
[Joe] For the 99v I would normally use a 100uF Bipolar in place of R11 just
because we have them in stock and that is about all that is needed.

( I don't mind making ANY changes that need be!!!)
#3 - Is there a DC Servo circuit posted on your web site that you'd
recommend for the 99v?
Remember - THIS Sontec circuit is using the "Inverted input" for
signal & Non-inverted for Servo...
does THAT make a difference in how the Servo is set up???

[Joe] Yes I prefer 12dB per octave DC servo instead of the 6dB per octave
version.

BTW... this EQ is amazing... I love it & can't believe how musical it is.
I'm sure your great op-amps are adding to the "sound".
[Joe]

Kevin

khstudio · Dec 12, 2008

Igor,
Sorry to be a PITA but I need you help. ;D

I've been using the JLM Hybrids for both in & output amps for now & they sound OK...
But I'm not completely sold on them.

Before I go spending over $200 for the Forssell amps, I want to try removing the DC Servo circuits & use CAPs on the outputs of the Op-Amps instead... for BOTH the input & output. (I must admit, I don't care for DC Servo's 90% of the time... they seem to do funny stuff to the "Sound".)

Could you PLEASE list ALL the components that should be removed? :-[

Also, could you recommend a Cap size & Voltage?

NOTE:
This will allow me to do 2 things... Here the circuit "without the Servo" & be able to test the 99v's.

Thanks man!

Kevin

user 10827 · Dec 12, 2008

Hi Guys,

FWIW i have just finished mine, but i could not afford the 993 and DLR op-amps, i stuck with OPA604, i have to say it still sounds bloody fantastic and specs up very very well, very low noise floor, IMD and THD are just stupidly low,

I might one day swap them out, id be interested to see the difference, whether i could hear the difference i suppose is the more important question.

any way here it is..

http://www.sinestarproject.com/sontec.jpg

http://www.sinestarproject.com/sontecin.jpg

Big thanks to Igor,

Cheers

Pete

Igor · Dec 12, 2008

Hi Kevin, you don't need to ask same question here and by mail.
Anyway, I'll answer twice

(in case someone stucked with same prob)

I never had any experience witj JLM op-amps in this circuit.
Just take into account, to make your EQ working with
JLM's I have first to buy them, then put inside EQ, then
fix all the issues , then tell you what to do.
And have no neither time nor other reasons to do it

As I can understand, JLM is not actually opamp,
it is kinda BA340 etc circuit where feedback comes to emitter of input transistor,
it means offset and different input impedance of + and - inputs.
Can't say it is bad, I using same thing on my single ended cascode FET-bipolar
topology amp. circuit in my pre-amp Albatross. For coloration in micpre,
SE is ideal. For circuit where you need ideal op-amp with some nice color....nope.

Take Forssell's if you want to make this EQ COOL
and say "here's the THE EQ with discrete opamps".

(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.

I'd first finnished your EQ with 604's or 5534's then
after checking everything and being sure it works 100%
was going for discrete to listen and compere the differencies.
Get it working, then, play with op-amps.

Igor · Dec 12, 2008

@Pete:
Enjoy!
Nice case

khstudio · Dec 12, 2008

Igor,
Thanks for your response.
Bear with me bro... I DO love this EQ & think you did a great job & I appreciate your help!!! ;D

OK,
I wasn't asking YOU to "Buy & Try" the JLM's... I asked how I "Should disable the DC Servo correctly" so I could try it & hear it for myself!"

Also, it's not about me being able to say "Hey, check out my Discrete Op-Amp EQ"... it's about sounding good. (& the way I would like it to sound)... Not to mention more $$$ I have to put out for the Forssell's.

I DID try to find 604's but they were ALL sold out in the US.

Also, I did call Fred about getting his amps.

But I'd still like to hear the circuit "without" the Servo (& add a Cap)

I know you designed this EQ BUT this is DIY & I don't see anything wrong with "Trying" it... I just need your help with HOW to best disable the Servo... that's all.

One more thing... I mentioned DrPat using the JLM 99v in the output of his REAL Sontec MEP250A & he loves it.
NOTE: Pat runs a very Professional studio & has worked with many top artists... so I respect his opinion. He knows good gear & what he's listening to.
I DID have the 99v's in my outputs & REALLY, REALLY liked the way they sounded!
...BUT the only way I could use it was to plug it into other (Capacitor input) Gear.

drpat said:
The Sontec is the unofficial king of mastering EQ's. There are others, but boards are available for the Sontec. You're not gonna find the real opamps, but you can still build the essence of one with substitute opamps. I used JLM99V opamps in my real Sontec when my original opamps blew up.
I had to change a couple of original components to make them work correctly, but it wasn't a big deal at all.

drpat said:
The mod sounds great! It's punchier, the low end is way nicer (and I liked the stock Sontec low end), and the high end is a tad bit more open. It definitely changed the sound, but it still has THAT Sontec character. In other words, I still reach for it for the same reasons that I would normally reach for a stock Sontec, plus it seems to work on other sources that the old personality, didn't seem to excel at, like kick drum.

I recommend this mod to all Sontec owners, weather their amps are dead or not.

Igor · Dec 13, 2008

Hi Kevin, I think it will be better to ask Joe about how to use JLM-99 in this EQ.
I don't want to give you solution pulled from the air and plain math.
Have to try it on my workbench first, test etc. Simply have no time for this.
I promissed to give support on this EQ, but not mods.

user 10827 · Dec 13, 2008

guys!! guys!! guys!!

I just have to say, i have been playing with mine a lot, cant keep my hands off it, seriously i have not felt this close to a EQ ever, i'm more of a compression kind a guy...well a legs man too...but.. :

so maybe forget the JLM or forsell for now, just use it with OPA604 etc, which lets face it is not in any way bad, but personally i think it has a lot to do with the design rather than the components..which are of course important but you know what i'm saying..

pete

Igor · Dec 14, 2008

Farnell and Newark both have OPA604's.

http://il.farnell.com/texas-instruments/opa604apg4/op-amp-low-distortion-fet-604/dp/1178434
http://www.newark.com/texas-instruments/opa604ap/operational-amplifier-op-amp-ic/dp/88K1967

khstudio · Dec 14, 2008

Igor said:
Farnell and Newark both have OPA604's.

http://il.farnell.com/texas-instruments/opa604apg4/op-amp-low-distortion-fet-604/dp/1178434
http://www.newark.com/texas-instruments/opa604ap/operational-amplifier-op-amp-ic/dp/88K1967

Hey cool!!! ;D

They must have JUST got more in... it's funny because they said the wait time was going to be MUCH longer. :

BTW, I tried using a cap on the output with the 99v & it STILL had DC on the other side of the cap.

I've never seen anything like it before... there must be something going on in the circuit I can't see or don't understand, so I put it back to stock.

NOTICE:
The FORSSELL DLR-1's are No longer being offered or made!!!!!!!!!!!!!!
I talked to Fred yesterday.

Tubefreak · Dec 15, 2008

Igor said:
Hi, 4k7 will give exactly +/-12db.

Hi, do you know which resistors I need if I only want 5dB of boost/cut as max scale?

THANX
Maarten

Holger · Dec 30, 2008

I've tested my second unit last weekend and wondered about the strange pot noises when adjusting freqs and levels. I also noticed a loud noise while switching the EQ on and off. I took it back home and measured a 20V DC on pin 2 of my output. Wow. Today I found -21V DC at pin 1 (output) of the MF 3 band OPA 2604 in one channel.
Can someone point me to the place where this huge amount of DC is introduced? I exchanged some 2604, it's always the same problem, no matter if the EQ is switched on or off.
The board itself looks good, I didn't see any bad solder point (Edited: note to self: need better glasses)... My other three channels are working perfect.
Clueless: Holger

Fixed: forgot to solder pin 5 of the mid freq 3 OPA 2604. Oh, oh, what a bug... :

chinchaigo · Jan 22, 2009

Igor, I was going to put in a pair of DLR-1 and JFET-993 but I just found out that DLR-1 is not in production anymore; so, do you have any other recommendation for the opamps?

Igor · Jan 22, 2009

Bad news

I very liked Fred's opamps.
For input, JE-990 or 992 (slower Forssel's opamp) will work fine.
OPA604 is very clean and fast cheap. I luv them as well.
You need something very fast for summing...
IMHO OPA604 is best chip for this.
I haven't tried JE-990 etc, because they are not fast enough.
Try to pm me for my design discrete opamps, they can be next sub to Forssel's IMHO.

user 10827 · Feb 7, 2009

Hi Igor,

On the next Sontec build i would like to add a switches to enable or defeat each band,

Is it as simple as inserting a switch between R18 through to R21?

best

Pete

Igor · Feb 7, 2009

Exactly. Like S1 refering to schem.

rrs · Feb 19, 2009

Hi
Considdering this for my next project. 2 channels.
And anyone guide me on the cost of this in US dollars and what Opamp options there are?

Thanks.

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