SSL 4000 EQ

[Sammas]

The cut/boost pots are centre-tapped (4 terminal), so those would be the problem....

Isnt this just for the TR computer?

Usually in EQ's the center tap is to widen and stabilize the "0dB" region of the pot.

 

[abechap024]

Usually in EQ's the center tap is to widen and stabilize the "0dB" region of the pot.

We might want to consider making the center tapped pots optional. Could be harder to source for some people...
So, I mean since we're basically going to be making these to use the EQs, and adjust the EQs by ears...some might aurgue that the center tapped pots are very well optional.

I mean its nice to know that when the pot says "0" its at "0" but if its doing +/- .5 db or even a db does that really matter in the grand scheme of things when your just adjusting everything by ear and if you don't like how it sounds you tweak the knob anyway...

Just a thought to keep those project accessible to more people.

 

[Michael Tibes]

Usually in EQ's the center tap is to widen and stabilize the "0dB" region of the pot.

We might want to consider making the center tapped pots optional. Could be harder to source for some people...
So, I mean since we're basically going to be making these to use the EQs, and adjust the EQs by ears...some might aurgue that the center tapped pots are very well optional.

I mean its nice to know that when the pot says "0" its at "0" but if its doing +/- .5 db or even a db does that really matter in the grand scheme of things when your just adjusting everything by ear and if you don't like how it sounds you tweak the knob anyway...

Just a thought to keep those project accessible to more people.

As already mentioned, in a DIY situation a lot of things could be build easier / cheaper than in a hi class console with very limited space. The center tap is only there to ensure the 'zero'-position - why not just make the band switchable anyway? Also, why not replace the more unusual pots with rotary switches with resistor chains, maybe also the band gains (this would automatically include a center tap...)? It would also make stereo eqs with perfect stereo matching possible.

What type of SSL eq are we talking about anyway? Regarding 4/6k I remember E, G, Stereo, Pultec from my mind, I believe there might have been more? Are the schematics around? I might have them on paper somewhere if not. Anyway, reading SSL schematics can be fun, there are often little errors, probably to fool copycats ;-)

Michael

 

[Michael Tibes]

...Anyway, while we're at it, anyone ever considered a Neve V-series EQ? This should make a different thread then...

Michael

 

[Dubka]

What type of SSL eq are we talking about anyway?

SSL 4000 E  -  242 EQ

 

[signalflow]

The 82E02 and 242 are identical except for the FET switching. 

I looked at the schems on this page:

http://www.ka-electronics.com/images/SSL/ssl_drawings_index.htm


The 82E02 looks the simplest to copy as there is no electronic switching eliminating a bunch of FETs.

Peter

I've been piddlin with a 82E02 layout the past couple of days.  No Center tap option, but could be done if the pots are mounted off board, which was the intention for my layout.  Also did not add the HP LP filters, figured I'd do them separately.

It's nothing fancy and I restricted the size of the layout to keep costs down.  Plus, It's still got at least another day before I'm happy with it.  And now I'm out of excuses......

-Casey

EDIT: Added Picture for massive criticism 

 

[abechap024]

Looks awesome! i'm excited

 

[ruckus328]

The 82E02 and 242 are identical except for the FET switching. 

I looked at the schems on this page:

http://www.ka-electronics.com/images/SSL/ssl_drawings_index.htm


The 82E02 looks the simplest to copy as there is no electronic switching eliminating a bunch of FETs.

Peter

I've been piddlin with a 82E02 layout the past couple of days.  No Center tap option, but could be done if the pots are mounted off board, which was the intention for my layout.  Also did not add the HP LP filters, figured I'd do them separately.

It's nothing fancy and I restricted the size of the layout to keep costs down.  Plus, It's still got at least another day before I'm happy with it.  And now I'm out of excuses......

-Casey

EDIT: Added Picture for massive criticism 

But what are you using for pots?

 

[detonator]

Looks awesome! i'm excited

+1

 

[signalflow]

The 82E02 and 242 are identical except for the FET switching. 

I looked at the schems on this page:

http://www.ka-electronics.com/images/SSL/ssl_drawings_index.htm


The 82E02 looks the simplest to copy as there is no electronic switching eliminating a bunch of FETs.

Peter

I've been piddlin with a 82E02 layout the past couple of days.  No Center tap option, but could be done if the pots are mounted off board, which was the intention for my layout.  Also did not add the HP LP filters, figured I'd do them separately.

It's nothing fancy and I restricted the size of the layout to keep costs down.  Plus, It's still got at least another day before I'm happy with it.  And now I'm out of excuses......

-Casey

EDIT: Added Picture for massive criticism 

But what are you using for pots?

Well, that can be tricky.  But mouser has some 25klin center detent in stock, Or just wire up a switch for the 25k.  They also have dual 10k log for the Q adjust, AML also has a couple of options for the 10k log.  The 50k rev logs are most likely going to have to be special order. 

But, AML does have a dual gang 47K Rev log.  What are the disadvantages in these?  I'm assuming the loss of some of the frequencies.  Anything else? 

And I want to say Omeg is reasonably priced for low quantity orders.  I've also looked at state-elec.com for custom ordering those but haven't put in a request for a quote from either company.

-Casey

 

[Igor]

Just $0.25: this is one of most painy EQ's, IMHO. Matter of taste.

When mixing at DB, we have 100% up maintained 4K console, with clean as possible monitoring and great acoustics.
4K EQ can be great for BD/snare, when you have anything else handy; for 90% of mixes, all 8 channels of Sontec8 are patched
for most important tracks and channel's EQ's are in bypass. For BD/snare, we use frequently Neve 1064. Again, matter of taste, of course.

Without criticism, some notes on PCB layout.

For pots package, change drills to somewhat 1.4mm at least.
Change power supply traces to 0.6mm at least (you have lot of space).
Power supply bypass caps at every IC chip is not over, IMHO.
Possible to use bigger packages for freq caps.
For sentertaped pots, possible to use half resistance pot + resistor + dpdt switch to get "boost/off/cut" functionality, usefull thing IMHO.

 

[zayance]

Nice project.

Just some obs:

I see some of the top tracks very close to some pads, the most obvious are the tracks near the pots....
And some of the bottom tracks are close to pads as well....
You could try to Thin just a little portion of the track, when this one has to pass between pads, could do the trick in some situations...
Not too thin tough....


PS: But i'm sure these are observations that are corrected by now, since it's not finished, just helpin out....

 

[signalflow]

Working on the layout some this morning.  I've extended the size of the board to accommodate pot spacing to resemble the original.  I'm sure the spacing isn't exact but it'll look nice in the case.  The boost/cuts and Qadjust are mounted on the bottom and the freq's & bell switches on the top.

Igor,

I've done the first two things you've recommended.

But I'm not sure what you mean about the bypass caps being over.  Does this mean they're not close enough to the chips?

Also, since the 50k dual rev logs are probably going to be special order.  Would adding a 100K parallel resistor to each deck of a 100K rev log be a good idea to get the 50K that we need? 

Zayance,  Good eye's, that was a quick one that I had thrown together. Those problems are taken care of. Thanks for the help!

-Casey

 

[Igor]

The boost/cuts and Qadjust are mounted on the bottom and the freq's & bell switches on the top

It can be good idea to fit it into 1RU, two channels. This way, to fit the pots, they have to be at same side of pcb.

Eagle, aye? possible to use different colors for tplace and bplace.

BTW, according to Tony's post, to pass the traces between pot's pins, just change the grid to somewhat 0.635 or 0.3175 mm;
or, use 1.27 main grid and change the alt grid to smaller, than, when tracing, press alt when drawing traces out of main grid.

But I'm not sure what you mean about the bypass caps being over.  Does this mean they're not close enough to the chips?

Bypass caps at every chip. I use for my projects 0805 SMD, X7R, 0.1uf/50V, at bottom side, close as possible to every chip.
But many of folks here hate smd, take this into acc't. 2.5mm X7R 0.1uf/50V ceramics at every chip PS pins is what I meant, in other words.

Would adding a 100K parallel resistor to each deck of a 100K rev log be a good idea to get the 50K that we need? 

Yes, this will work; about 20% of initial range of pots (mean, from 7.30 to 10.00) will feel bit wrong; however, it is absolutely enough for testing.
Possible to compromize and have extended to low side range using say 100k-RlogPots in parallel with 200k resistor.

BTW:

OM-01-018 - 16mm - 3 gang 47k rev. log / 47k rev. log / 22k lin + ident- concentric shaft

http://www.audiomaintenance.com/acatalog/potentiometers_carbon_16mm_diameter_concentic_shaft.html\

Refering to 82e02, this is the eq we have on 32 channels and I hate, this pot will work 100%.
No need for 4k7 and centertap for gain, there will be bit different feel on boost/cut, however,
many eq's done this way (without CT), like Urei 545. 
To be complete Nazi, it is possible to use: 10k lin pot +10k resistor+ dpdt boost-off-cut (on-off-on) switch at every boost/cut band.

 

[signalflow]

Worked on this for a few days and started a new layout with the pots from AML that Igor suggested.

All pots and switches on same side of PCB.  PCB size is 200x100mm double sided.  I did not add in switches to bypass each filter.  This seems a bit overkill to me.  There are plenty of EQ's that do not incorporate this and work great.

If no one sees any blatant errors guess prototyping is in order now..............

-Casey

 

[benlindell]

The only problem I see is that I'm going to need a lot of these! Great work, I'm definitely excited to hear these. I'll leave the layout critique to people who know what they're talking about.

 

[frazzman]

this is awesome...i love this EQ...great news

 

[peterc]

I have been mulling this for a while.

I am only doing 500 series stuff at the moment, so what about the 4 band EQ with a switched Hi/Lo Q?

Working within panel size is a bitch, always thought 500 series should have been 4u.

Jus' sayin.....

 

[Ptownkid]

Working within panel size is a bitch, always thought 500 series should have been 4u.

Jus' sayin.....

Maybe THAT should be your next project, haha

 

[peterc]

..... and also a 300v & 6.3v supplies.

More like a picnic basket than a lunch box 8)