What's a good, simple and cheap 1U stereo eq unit?

Hi guys,

Haven't attempted a 3 or 4 band eq unit before and wondered what everyone's thoughts would be on a simple but fairly cheap unit, preferably something I can self etch single layer.
I do want to have a few api 550a and 550b versions eventually but I can see there is a fair bit of work involved.
All ideas welcomed.

Regards

Spence.

I will suggest Gyraf Calrec 1549 or AUDIOX W492 

I think the Nite3D EQ is a single layer board.

Nite eq is good, cheap and an easy self etch...

However getting the freq response flat (at center position on all pots) is a bit of a minefield ... I etched built 2 channels in a few weeks but then spent months tweaking it, the build itself is not complex but getting it 100% is fiddly if you're anal like me. I know a lot of builders probably didn't goto the lengths I went to

Hi frazzman,

Think you have found the perfect eq for what I want, I can't seem to locate the self etch files if your able to post please, then I'll start building a few, only want to build 8 of them for my patch bay.

Regards

Spence.

Spencerleehorton said:

Hi frazzman,

Think you have found the perfect eq for what I want, I can't seem to locate the self etch files if your able to post please, then I'll start building a few, only want to build 8 of them for my patch bay.

Regards

Spence.

Click to expand...

For what it's worth, I have built both the trident 80b ones and eq3d ones and find the trident both better sounding and much more flexible (with the sweepable midbands).

Well I think I'm going to go for a combination of nite eq if I can find the self etch files and the Neumann 492 first of all and see how they sound and function.
The S800 look great but also looks a fair bit more involved with transformer etc which add a fair bit onto the build price.
The idea is really to try and use up all my left over bits as much as possible from my other builds, I have loads of NE5534, THAT1646, OPA2604, TL072, NE5532 about 20 to 50 of each of these.
I have quite a few 18/0/18 toroidal that are 200vac which would do for a psu to power quite a few.
Rather than use any output transformers I also have plenty of SSM2142, DRV134 for line balancing.

Regards

Spence.

Spencerleehorton said:

Well I think I'm going to go for a combination of nite eq if I can find the self etch files and the Neumann 492 first of all and see how they sound and function.
The S800 look great but also looks a fair bit more involved with transformer etc which add a fair bit onto the build price.
The idea is really to try and use up all my left over bits as much as possible from my other builds, I have loads of NE5534, THAT1646, OPA2604, TL072, NE5532 about 20 to 50 of each of these.
I have quite a few 18/0/18 toroidal that are 200vac which would do for a psu to power quite a few.
Rather than use any output transformers I also have plenty of SSM2142, DRV134 for line balancing.

Regards

Spence.

Click to expand...

I don't believe my S800 build has any output transformers.. The outputs are definitely opamp balanced. This BOM from Peterc uses 5 TL071 and one 5532:
https://dl.dropboxusercontent.com/u/16318714/S800_BOM.xls

Of course, not trying to peddle any stuff here, it's your project, just saying that there is no output trafo in mine and it's all good.

Spencerleehorton said:

Hi frazzman,

Think you have found the perfect eq for what I want, I can't seem to locate the self etch files if your able to post please, then I'll start building a few, only want to build 8 of them for my patch bay.

Regards

Spence.

Click to expand...

Hi Spence,
Here you go. Everything you need is here:
http://www.khstudio.us/EQ3D.htm

Make sure you read the build thread. It's an easy eq to build but hard to get right. Due to pot tolerances of +/- 20% and the design of the eq, you need to offset the center position of each pot to get a flat response. I.e. Measure the resistance at center and then tweak the series resistor for each band so that the pot center position is compensated... Hard to explain, but easy to pickup from reading the build thread. I still couldn't get my eq to be perfectly flat with all pots centered but came pretty close. I think a lot of builders would have taken the easy way out and left this. So you need to replace the 5k62 series resistors with trim pots ...

frazzman said:

http://www.khstudio.us/EQ3D.htm

It's an easy eq to build but hard to get right. Due to pot tolerances of +/- 20% and the design of the eq, you need to offset the center position of each pot to get a flat response. I.e. Measure the resistance at center and then tweak the series resistor for each band so that the pot center position is compensated... Hard to explain, but easy to pickup from reading the build thread. I still couldn't get my eq to be perfectly flat with all pots centered but came pretty close. I think a lot of builders would have taken the easy way out and left this. So you need to replace the 5k62 series resistors with trim pots ...

Click to expand...

I don't think it is possible to get flat response with Nite EQ regardless of how much tweaking.  The circuit is flawed.

I recommend the Calrec but I'm biased as I worked on that in Jurassic times.

ricardo said:

frazzman said:

http://www.khstudio.us/EQ3D.htm

It's an easy eq to build but hard to get right. Due to pot tolerances of +/- 20% and the design of the eq, you need to offset the center position of each pot to get a flat response. I.e. Measure the resistance at center and then tweak the series resistor for each band so that the pot center position is compensated... Hard to explain, but easy to pickup from reading the build thread. I still couldn't get my eq to be perfectly flat with all pots centered but came pretty close. I think a lot of builders would have taken the easy way out and left this. So you need to replace the 5k62 series resistors with trim pots ...

Click to expand...

I don't think it is possible to get flat response with Nite EQ regardless of how much tweaking.  The circuit is flawed.

I recommend the Calrec but I'm biased as I worked on that in Jurassic times.

Click to expand...

You can get pretty close... Mines within +/- 0.2db. Not exactly transparent mastering grade but it still sounds damn good. If you ignore your frequency analyser, I doubt you can hear a wide -0.2db cut/boost

Yes, that's one of the reasons I don't like the EQ.. I have to yet tweak for centers to be off. But I still prefer 80b sound.

frazzman said:

Spencerleehorton said:

Hi frazzman,

Think you have found the perfect eq for what I want, I can't seem to locate the self etch files if your able to post please, then I'll start building a few, only want to build 8 of them for my patch bay.

Regards

Spence.

Click to expand...

Hi Spence,
Here you go. Everything you need is here:
http://www.khstudio.us/EQ3D.htm

Make sure you read the build thread. It's an easy eq to build but hard to get right. Due to pot tolerances of +/- 20% and the design of the eq, you need to offset the center position of each pot to get a flat response. I.e. Measure the resistance at center and then tweak the series resistor for each band so that the pot center position is compensated... Hard to explain, but easy to pickup from reading the build thread. I still couldn't get my eq to be perfectly flat with all pots centered but came pretty close. I think a lot of builders would have taken the easy way out and left this. So you need to replace the 5k62 series resistors with trim pots ...

Click to expand...

baadc0de said:

Yes, that's one of the reasons I don't like the EQ.. I have to yet tweak for centers to be off. But I still prefer 80b sound.

frazzman said:

Spencerleehorton said:

Hi frazzman,

Think you have found the perfect eq for what I want, I can't seem to locate the self etch files if your able to post please, then I'll start building a few, only want to build 8 of them for my patch bay.

Regards

Spence.

Click to expand...

Hi Spence,
Here you go. Everything you need is here:
http://www.khstudio.us/EQ3D.htm

Make sure you read the build thread. It's an easy eq to build but hard to get right. Due to pot tolerances of +/- 20% and the design of the eq, you need to offset the center position of each pot to get a flat response. I.e. Measure the resistance at center and then tweak the series resistor for each band so that the pot center position is compensated... Hard to explain, but easy to pickup from reading the build thread. I still couldn't get my eq to be perfectly flat with all pots centered but came pretty close. I think a lot of builders would have taken the easy way out and left this. So you need to replace the 5k62 series resistors with trim pots ...

Click to expand...

Click to expand...

I've actually come to the same conclusion, i've shelved my Nite EQ. Im sick of messing around with it. It sounds ok on individual sources but I wanted to use it on the master bus for some flavour but it just doesn't sound right as its freq response is all over the place. You ever used a S800 on a stereo bus? There seems to be a real slump in good stereo bus EQs lately... I really wish I made Igors Sontec when it was still around

Yeah real shame about the sontec eq not being available, maybe someone could change this?
I would much rather have a eq which would be good for mastering.

Regards

Spence.

Spencerleehorton said:

Yeah real shame about the sontec eq not being available, maybe someone could change this?
I would much rather have a eq which would be good for mastering.

Regards

Spence.

Click to expand...

Yeah... I've started researching Barry porters net eq, which by all accounts looks amazing but info on it is a bit sketchy. I've seen some pretty impressive builds of it. There's a new build which a dIY racked sontec / gml clone.... Looks nice but looks pretty expensive to build and it's a partial kit, not just pcbs

Spencerleehorton said:

Yeah real shame about the sontec eq not being available, maybe someone could change this?
I would much rather have a eq which would be good for mastering.

Regards

Spence.

Click to expand...

there is no mastering eq simple and cheap

Why not go for the Barry Porter? There's nothing sketchy at all about the info, has been straight forward for me so far. The documentation that Barry provides also makes sense.

I guess the only sketchy info is the BOM that's going around isn't 100%, some minor errors in there but use the BOM along with the PCB overlay that JLM produced and compare the two when sourcing parts.

I am currently designing a mastering EQ with Mid side matrix based on the Quad 8 444 in a 51x format... And I am basically going to offer the gerbers for free, it is transformer balanced, but I may be able to squeeze solid state balancing as an option. If it works well you can try to get two boards and build a PSU for it. Just food for a thought, I am still in proto phase.

druu said:

Why not go for the Barry Porter? There's nothing sketchy at all about the info, has been straight forward for me so far. The documentation that Barry provides also makes sense.

I guess the only sketchy info is the BOM that's going around isn't 100%, some minor errors in there but use the BOM along with the PCB overlay that JLM produced and compare the two when sourcing parts.

Click to expand...

Hi Druu,
Good to see another fellow Aussie on here. I've decided to go with the net eq also. It's just not as popular as some of the other builds which have 100s of pages of discussion in case you get stuck... The net eq does seem to be highly acclaimed amoung mastering engineers. Anyway, I'm not worried about the BOM. Just the stepped switches. I have never used these in a build before, except for rotary switches in the gyraf builds. I was going to use Harpos spreadsheet for the resistor values. Soldering all those resistors sure looks tedious but I think it's critical for this application.

Did you use stepped switches in yours? If so, any tips? Aside from deciding on the resistors values, is there much else to it ? Is it just a matter of soldering them in series along each gang of the pins ? I've been doing some reading trying to get my head around using these in place of pots. What about wiring them up to the boards? I can see there is a wiper on these switches but what about the other 2 lugs that are on a standard pot? Sorry for all the questions... Appreciate any insight

Hey frazzman, where are you located? Worth updating your location in your profile.

I was in the same shoes as yourself when I built my Sontec (Igor's boards). I ended up hassling Harpo a tonne! But he was happy to assist and now I feel obligated to pass on that info so let me know if you need assistance at all.

Stepped switches aren't difficult, mega tedious but not difficult to put together. Use Harpo's spreadsheets and you can't really go wrong! Once you've done a couple and found your rhythm you basically lock into the process pretty quickly.

See here for some images of the process:

http://amnet.net.au/~amunday/sontec/images/

And here's something I think Harpo sent me a while back which will help make sense for Gain switches:



HTH.