Sontec mastering equalizer

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Fablab

Well-known member
Joined
Nov 12, 2008
Messages
347
Location
Italy
Hi, some time ago I have seen "around on the net" a DIY version of a Sontec mastering equalizer.
I remember there were more small boards
Now I'd like to experiment with this circuit, but ... it is disappeared
Someone know the reason ... and where is it possible to find that files?
Thank you
 
Fabio's site is down so all the info on the sontec mastering eq from that site is gone.

Be patient, Igor is working on a Sontec mastering project that will be available soon (can't wait).

You can check out Igor's white market thread for info on the Sontec EQ, schematics and all. The only thing that makes it a mastering EQ is to use stepped attenuators.
 
But didn't those "oldschool" Sontec DIY mastering equalisers actually use DOA's for the individual filters as well? Each band had an individual board, lot's of space for parts.

I sure hope igor allows this with his new sontec revision. Using stepped attenuators for the old igor board is trivial already.
 
Kingston said:
But didn't those "oldschool" Sontec DIY mastering equalisers actually use DOA's for the individual filters as well? Each band had an individual board, lot's of space for parts.

I sure hope igor allows this with his new sontec revision. Using stepped attenuators for the old igor board is trivial already.

I already asked. He is gonna stick with the OPA604 in the filter positions as he says they perform better and provide less phasing than DOAs in that particular part of the cuircuit.

However, I expressed that having the option would be cool, so I too hope he will implement the DOA footprint on all boards.

I have just pulled out the pdf of bauman's board and it does give the DOA footprint as well.

I might build 2 sontecs now... one with DOAs throughout and one with 604s...

I'm also thinking of building a Barry Porter EQ as well... So I'm considering those topologies...
 
I'm doing a dual fabio sontec - I'd recommend going for Igors  ;)

Much less painful.

The fabio is 10x pcbs for the filters,  2x pcbs for the buffer amps,
and 1x psu pcb.

Plus the pots are not easy to get that mount on the pcbs, so basically
they are hanging off.

That's a lot of wiring and mounting of pcbs!

And they were not cheap!

I agree though that doas are interesting. But probably not as high performance.

Still - if you are interested in info, pm me.

Cheers
 
Matthew Jacobs said:
I already asked. He is gonna stick with the OPA604 in the filter positions as he says they perform better and provide less phasing than DOAs in that particular part of the cuircuit.

I wonder how. OPA604 is not even a particularly good opamp. There are dozens of modern better performing alternatives if aiming for that analytical sound (with even less distortion).

Number one reason I would ever even consider a DOA for a filter circuit would be coloration. I would not expect any DOA to perform better "on paper" than some super high end modern opamp I could just as well use in that position. For serious analytical approach I would go for something like ADA4898-1 or ADA4898-2(for dual). OPA604 and OPA2604 are basically distortion generators in comparison.
 
Just wondering if the ADA4898 are really that much better then OPA's in practice. Why is nobody talking about them more then since they excist for quite some time?
I seriously wonder..
 
Just looking at the original schematics for the Sontec EQ and it uses 5534 and TL071 in the filter section...

I think the logic behind this is that in this particular part of the circuit (gyrator I believe) the opamps are less crucial. I'm sure it's a cost / benefit decision.

This is DIY so we can build it the way we love it and with the components we love / can afford.
 
DOA sontec is a clear winner vs OPA sontec without a doubt...
IMHO, if worried about phase, there is always RED EQ  ;)
 
dagoose said:
Just wondering if the ADA4898 are really that much better then OPA's in practice. Why is nobody talking about them more then since they excist for quite some time?

because they are expensive, need special care when implementing, and very few people care about opamps details in that level. There are dozens of opamps nobody ever mentions here on the forum for "NASA" grade audio, etc. sonar usage and easily beat the usual suspects in most audio performance aspects.

OPA's on the other hand have a good reputation so people talk about them even if they don't even know any details. Most of them are average at best, not even that great sound.
 
Kingston said:
Matthew Jacobs said:
I already asked. He is gonna stick with the OPA604 in the filter positions as he says they perform better and provide less phasing than DOAs in that particular part of the cuircuit.

I wonder how. OPA604 is not even a particularly good opamp. There are dozens of modern better performing alternatives if aiming for that analytical sound (with even less distortion).

Number one reason I would ever even consider a DOA for a filter circuit would be coloration. I would not expect any DOA to perform better "on paper" than some super high end modern opamp I could just as well use in that position. For serious analytical approach I would go for something like ADA4898-1 or ADA4898-2(for dual). OPA604 and OPA2604 are basically distortion generators in comparison.
I dont think these opamps, with 2.5pA/sqrtHz noise current, are a good choice in the "gyrator" position. They are optimized for <500R source impedance, the GML circuit is about 10 times higher. It would probably be possible to scale the values of the components to optimize for the 4898, but is not a simple endeavour.
 
Kingston said:
But didn't those "oldschool" Sontec DIY mastering equalisers actually use DOA's for the individual filters as well? Each band had an individual board, lot's of space for parts.

I don't think so.  Only the input buffer and output amp had DOA's.  I think DOA's on the filters was a feature added by Fabio.  You can ask Jaakko about his Fabio Sontec build.  He used Forssell's throughout his over-the-top build.  Sadly, I think the posts were lost.  I think his consensus was it wasn't really worth it in the end. 
 
MikoKensington said:
I think DOA's on the filters was a feature added by Fabio.  You can ask Jaakko about his Fabio Sontec build.  He used Forssell's throughout his over-the-top build.

Yeah that's what I meant about olschool sontec DIY builds. I know the original used NE5532 (or was it NE5534) for filters. In fact I tried those for my build as well. I liked it better than the OPA's, but in the end opted for LME49860. This is the way to go for analytical and distortion free sound. The difference above something like 5khz is remarkeable, especially if you want to lift those frequencies instead of just adding aphex aural exciter-like distorted "tizz". They allow high rail voltages also so they are a great match for DOA I/O.
 
Thanks for the info.  Since you have experimented with a few opamps in yours, can you comment on the color introduced by the various options.  You say the LME49860 is on the analytical end of things.  Do the other options lend character or graininess?
 
MikoKensington said:
Thanks for the info.  Since you have experimented with a few opamps in yours, can you comment on the color introduced by the various options.  You say the LME49860 is on the analytical end of things.  Do the other options lend character or graininess?

taking into account we are in subtle territory,

OPA2604 (and the single version) certainly add grain. They are not good opamps, don't buy into the OPA hype. I mean, you either like it, or you haven't had a chance to shoot out for better options. NE5532 is surprisingly good. And not just for their age, but they are really good sound. I've been considering building a unit with just these, for "rock". But in the end LME49860 is best. I don't know how else to put it but transparency and resolution. They are transparent to the point of being boring, but what else would deserve the name 'mastering EQ'?

PS. at this level of subtleties, choice of caps matter.

the three opamps mentioned above are of the very few real choices for high rail voltages if you are using DOA for input debalancing and summing also. Or are there more for 22V bipolar? I'm always looking for more options.

There are many other opamps for 15V rails, but I won't bore anyone with that here, especially since I haven't used them in sontec.
 

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