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

[druu]

Oh BTW, I haven't yet finished my BP EQ, still (slowly) sourcing parts and populating the boards. I'll be making it dual ganged for single control set, already have the Sontec with M/S for dual mono mastering duties.

 

[frazzman]

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.

Hey Druu,

Cheers dude. I'm in Melbourne, I just updated my profile.

That info is really helpful. I wish I got the chance to make Igor's sontec EQ. I'm just really lacking a good stereo EQ, particularly for mastering duties. The Net EQ gets a pretty good wrap for being a quality EQ.

They do look tedious as hell but that doesn't bother me too much, just chip away at them slowly. What brand switches did you use? Looking at the net EQ thread, some people have had good experience with the uraltone/chinese switches.... they sure are a hell of a lot cheaper to the grayhills or something in that area. I've got to get my hands on some of these stepped switches to get my head around them. How do they hook up when you substitute them into the net EQ circuit? I'm guessing it will make more sense when I actually see one of these switches.

Did you order PCBs from Gustav for the net EQ? Is it a double sided PCB?

I'm working on a BOM now, hopefully given that we're in the same geographic location we can help each other out with any tricky parts etc.

Still trying to get my head around the switches options for the net EQ. For the Q switches I could use the standard ALPHA 12x1 pole rotary switches (the kind you get from Jaycar..)
For the gain and frequency switches,  24x2 pole switches, although looking through the thread - there seems to be a requirement for 24x3 switches for some parts - for peak/shelf?)

What did you end up going with? Apart from the switches, it looks like a pretty straight forward build.

I just finished a D-LA2A which was my most intricate project so far... sounds awesome... Haven't come across too many Aussies on here

 

[druu]

Most pots and rotaries connect the same way; in, wiper and out. Centre '0' ones will have that extra ground reference wire you simply wire into the middle of your resistor chain, making four connections per pole.

Yup most use the 'uraltone' type switches. I buy mine through eBay, http://stores.ebay.com.au/supermarket098/ - super reliable seller for me. He also does 6 pole 24 step rotaries, required for shelving for a dual ganged BP EQ. He does all sorts, if you're buying a chunk from them maybe send them an email and ask for more of a discount, i'm sure they'll be happy to help out.

PCB's from Gustav, yes double sided and quite large.

Yeah I did have issues trying to source some caps, so far only populated resistors, relays, dip8 holders and regs. Looks like we need to buy the caps scattered (from different places, argh).

 

[frazzman]

Most pots and rotaries connect the same way; in, wiper and out. Centre '0' ones will have that extra ground reference wire you simply wire into the middle of your resistor chain, making four connections per pole.

Yup most use the 'uraltone' type switches. I buy mine through eBay, http://stores.ebay.com.au/supermarket098/ - super reliable seller for me. He also does 6 pole 24 step rotaries, required for shelving for a dual ganged BP EQ. He does all sorts, if you're buying a chunk from them maybe send them an email and ask for more of a discount, i'm sure they'll be happy to help out.

PCB's from Gustav, yes double sided and quite large.

Yeah I did have issues trying to source some caps, so far only populated resistors, relays, dip8 holders and regs. Looks like we need to buy the caps scattered (from different places, argh).

Thanks mate, i'll share my BOM with you when its complete as it might help you with the caps. I usually use futurlec.com.au for most electro's & resistors, then RS for just about everything else... then of course If I forget to order something and i'm in the mood for being ripped off i'll goto jaycar.

 

[ricardo]

If you are going to use 'switched pots', you might as well build the Calrec.

Gyraf mentions the only 'difficult to get part' are the reverse log pots.  But if you use normal log pots, it just means your frequency knob is backwards  ;D

 

[frazzman]

If you are going to use 'switched pots', you might as well build the Calrec.

Gyraf mentions the only 'difficult to get part' are the reverse log pots.  But if you use normal log pots, it just means your frequency knob is backwards  ;D

Hi Ricardo,
For mastering applications I don't think pots will cut it. Too difficult to match left and right channels with accuracy. Cheers

 

[druu]

I think riccardo meant if you're using rotaries youre no longer limited by pot types.

 

[frazzman]

I think riccardo meant if you're using rotaries youre no longer limited by pot types.

Hey Druu,
Thanks for that.
I've actually just about finished my BOM with Aussie sources if you're looking for any more parts... Still scratching my head a bit about the switch decisions but I'm sure it will come together. Are you going with alpha style 1x12 rotary switches for the Q controls and 2x24s for the gain and freq controls ? The PCB itself seems pretty straight forward to populate.... Btw... Futurlec are ridiculously cheap for opamps, $0.40 for an ne5532 compared to good old jaycar at $4 a pop...

 

[druu]

As mentioned earlier I'll be making mine a dual ganged setup, one set of controls for stereo operation. I'll be sourcing the switches from eBay.

I got 60x NE5532's from eBay from a reputable seller for cheap. the last time I bought from futurelec, stock came from Thailand.

 

[dmnieto]

As mentioned earlier I'll be making mine a dual ganged setup, one set of controls for stereo operation. I'll be sourcing the switches from eBay.

I got 60x NE5532's from eBay from a reputable seller for cheap. the last time I bought from futurelec, stock came from Thailand.

Dual gang switches? I have been trying to source them from everywhere without luck. Where did you get them from?

 

[druu]

Not sure if we're thinking of the same thing here. I was referring to using a single, 4 pole rotary switch for controlling both left and right channels simultaneously.

 

[frazzman]

Not sure if we're thinking of the same thing here. I was referring to using a single, 4 pole rotary switch for controlling both left and right channels simultaneously.

Hi druu.

I'm with you now, I can actually see when looking over the Net EQ thread that some builders have gone both ways, some have actually done what I had in mind, which is essentially dual mono with steppd switches.

I think your way is better though, less switches if we go with 4 pole and control both channels together..

I need to play with some of these rotary switches, I'm a bit confused as to how it would look in reality. If we are using 1 switch to control 2 channels, would than mean we would duplicate the resistors across two poles?

To better explain would it end up looking someething like this crappy paint drawing - assuming resistors are the same values on each of the two pole?

Sorry for the noob questions on this, never had the experience with these switches...
Harpo's spreadsheet seems to look like its covering the idea of seperate controls for each channel (but I'm sure its easily adapted to this situation)

 

[ricardo]

For mastering applications I don't think pots will cut it. Too difficult to match left and right channels with accuracy.

Are you claiming that all Mastering EQs have only switched controls for Boost/Cut, Freq & Q?  Got any examples?

Matching is a lot to do with good circuitry.  Certainly M-series, which is what Gyraf's Calrec EQ is from, has been used to master many important records.

 

[frazzman]

For mastering applications I don't think pots will cut it. Too difficult to match left and right channels with accuracy.

Are you claiming that all Mastering EQs have only switched controls for Boost/Cut, Freq & Q?  Got any examples?

Matching is a lot to do with good circuitry.  Certainly M-series, which is what Gyraf's Calrec EQ is from, has been used to master many important records.

Hi Ricardo,
No not at all, I believe you could get great results with either. However I think stepped pots are easier for recall, plus remember potentiometers have maybe 20% tolerance, so you won't match the level of accuracy you would get with stepped pots... Just my 0.2cents

 

[druu]

Hi druu.

I'm with you now, I can actually see when looking over the Net EQ thread that some builders have gone both ways, some have actually done what I had in mind, which is essentially dual mono with steppd switches.

I think your way is better though, less switches if we go with 4 pole and control both channels together..

I need to play with some of these rotary switches, I'm a bit confused as to how it would look in reality. If we are using 1 switch to control 2 channels, would than mean we would duplicate the resistors across two poles?

To better explain would it end up looking someething like this crappy paint drawing - assuming resistors are the same values on each of the two pole?

Sorry for the noob questions on this, never had the experience with these switches...
Harpo's spreadsheet seems to look like its covering the idea of seperate controls for each channel (but I'm sure its easily adapted to this situation)

It depends. Some people may prefer dual mono if they have an M/S encoder to allow different settings for each channel. I already have a dual mono EQ so that's why I'm going for the ganged approach this time, strictly L/R.

Your pic looks about right. But it depends on what you need and which control you're making the switch for.

For example, if one channel requires a single pole 10k pot, a 2 pole rotary soldered with a chain of resistors up to 10k would be suitable for both channels for that single control (if that makes sense). So what you're assuming above is correct. For best tracking between the channels you would need to tediously measure each resistor to match them, pretty much a given for a mastering EQ.

 

[frazzman]

Hi druu.

I'm with you now, I can actually see when looking over the Net EQ thread that some builders have gone both ways, some have actually done what I had in mind, which is essentially dual mono with steppd switches.

I think your way is better though, less switches if we go with 4 pole and control both channels together..

I need to play with some of these rotary switches, I'm a bit confused as to how it would look in reality. If we are using 1 switch to control 2 channels, would than mean we would duplicate the resistors across two poles?

To better explain would it end up looking someething like this crappy paint drawing - assuming resistors are the same values on each of the two pole?

Sorry for the noob questions on this, never had the experience with these switches...
Harpo's spreadsheet seems to look like its covering the idea of seperate controls for each channel (but I'm sure its easily adapted to this situation)

It depends. Some people may prefer dual mono if they have an M/S encoder to allow different settings for each channel. I already have a dual mono EQ so that's why I'm going for the ganged approach this time, strictly L/R.

Your pic looks about right. But it depends on what you need and which control you're making the switch for.

For example, if one channel requires a single pole 10k pot, a 2 pole rotary soldered with a chain of resistors up to 10k would be suitable for both channels for that single control (if that makes sense). So what you're assuming above is correct. For best tracking between the channels you would need to tediously measure each resistor to match them, pretty much a given for a mastering EQ.

Thanks mate. I got 1% tolerance resistors for the main boards and < 1% for the rotary switches. I'm basically using Harpos spreadsheet as the basis for the frequencies and which rotary switches to order. I wanted to use this mainly for stereo applications as well so no need for dual mono, so I'd be inclined to go with you're approach as well. Have you worked out which switches and how many of each? As I see it , there are 4 scenarios to cater for - HPF switch, Q, freq bands, gain (-/+ 5db in 0.5db increments - pos 11 is 0). All the freqs in Harpos sheet look good to me I just need to work out what to order and how I'm going to rig it up

 

[druu]

I've not yet looked into the rotaries yet for this project. Just have a look at the boards; I think Barry's docs state to assume all pots are 10K unless otherwise stated. If a pot is a single pole 10K LIN, then multiply by two for both channels. For example Low Frequency Q control is a 10K Lin single pole pot. So for the rotary equivalent it would be a 2 pole pot, one pole wired to each board. Same for +/- Gain, single pole 10K Lin CT (the extra wire will be for centre tapped 0v reference, wired to the middle of your resistor chain.

Feel free to email me if you're not sure, i'll help where I can.

 

[frazzman]

I've not yet looked into the rotaries yet for this project. Just have a look at the boards; I think Barry's docs state to assume all pots are 10K unless otherwise stated. If a pot is a single pole 10K LIN, then multiply by two for both channels. For example Low Frequency Q control is a 10K Lin single pole pot. So for the rotary equivalent it would be a 2 pole pot, one pole wired to each board. Same for +/- Gain, single pole 10K Lin CT (the extra wire will be for centre tapped 0v reference, wired to the middle of your resistor chain.

Feel free to email me if you're not sure, i'll help where I can.

Thanks a lot, I've built a lot of projects and have 'Aussie' BOMs on hand if you ever need anything, happy to return the favour.

Looking at the pcbs, I figure the following is required for stereo operation:
HPF filter is 2 pole > stereo: 24pos x 4 pole
Q controls are 1 pole > stereo: 24pos x 2 pole
Gain pots are 1 pole > stereo: 24pos x 2 pole
LF and HF are 3 pole > stereo: 24pos x 6 pole
MF1 and MF2 are 2 pole > stereo: 24pos x 4 pole

 

[druu]

Sounds about right.