SSL 4000 EQ

[signalflow]

Any news on your 2 problems?

regards,
Wolfgang

I still don't have the unit back from the guy i lent it to but, going over somethings I miss labeled the cap in the relay portion to a 22uf instead of a 220uf which I suspect is my problem.  Everything I've read suggests at least a 100uf so I'm thinking this is the culprit......maybe(crosses fingers)

The too much gain when active problem could be a number of things but I'm wondering if the gain pot value of 25K is correct..... 

I've been going through the active filter cook book and see where in circuits like the Neve 81 series EQ where the resistors on the negative side of the op-amp need to be as close to or the same as the gain.  Same goes for the Harrison 28/32 EQ.  But the SSL is a quite a bit different and I'm having a hard time understanding it as far as referencing to a similar circuit. Cause honestly if it's meant to work the same then there are some errors in the schematic that I'm not educated enough to see and I have no problem admitting that. 

So, again, anyone that can help with checking if the values make sense in the original the help is much needed and appreciated.

-Casey

 

[horvitz]

Looking at the original schem, looks like there are some 4k7 to gnd on a center tap(?) on the boost/cut pots that aren't on yours?  Maybe something..

 

[signalflow]

Looking at the original schem, looks like there are some 4k7 to gnd on a center tap(?) on the boost/cut pots that aren't on yours?  Maybe something..

From what I understand(which isn't much)is that those are there only to ensure that the pots are acurate when no gain is need on that band. I'm gonna replace the 25K pots with 10K's and see what happens then. But first i need to get it back.

-Casey

 

[abechap024]

Hola,
Just looking through your schematics, looking for maybe why you lose 6 dB when you switch it into bypass. And also why the relays "pop".

So it seems like the EQ circuit is adding 6db, because when in bypass it is essentially just a wire. I bet changing the input chip to the THAT 1246 would fix the problem because it has a gain of -6dB. And the chip you have now (the  THAT 1240) has a gain of 0.  Anyway should fix it.

The popping relays are something...maybe if you connected a high value resistor (1M) between the 2 sides of the switch (9&10, 8&6 on the first input for example) that might cure it. Also you could try having a separate power ground for the relay, or putting DC blocking caps on one side of the switch (who wants more caps in the signal path though?) But might fix it.

Hopefully this helps!
Abe

 

[signalflow]

The schematic says 1240 but there is a 1246 in the socket.  I changed this but did not update the schematic to show the change.  So a 1246 to a 1646 should give me exact levels as if it were in bypass give or take due to the circuit. 

I think I've found the popping issue which was an actual value error in the schematic.  Still have not fixed this as the unit is still being loaned out so i won't know for sure till I get it back.

-Casey

 

[abechap024]

The schematic says 1240 but there is a 1246 in the socket.  I changed this but did not update the schematic to show the change.  So a 1246 to a 1646 should give me exact levels as if it were in bypass give or take due to the circuit. 

Ok well thats good. So are you saing that the problem is fixed, or there still is an additional +6 from the circuit?

I think I've found the popping issue which was an actual value error in the schematic.  Still have not fixed this as the unit is still being loaned out so i won't know for sure till I get it back.

-Casey

Good!

 

[signalflow]

The schematic says 1240 but there is a 1246 in the socket.  I changed this but did not update the schematic to show the change.  So a 1246 to a 1646 should give me exact levels as if it were in bypass give or take due to the circuit. 

Ok well thats good. So are you saing that the problem is fixed, or there still is an additional +6 from the circuit?

I think I've found the popping issue which was an actual value error in the schematic.  Still have not fixed this as the unit is still being loaned out so i won't know for sure till I get it back.

-Casey

Good!

There is still a +6db increase in the circuit.

-Casey

 

[signalflow]

here's the final update on the SSL EQ.  After a ton of trial and error troubleshooting I found the problem with the change in volume between the bypass and effected signal.  I had over looked the ground ref pin on the THAT1246.  Once this pin was grounded the EQ started behaving the way it should.  Also the popping was taken care of by using the correct value cap in the relay circuit.

So long story short it's working and sounds pretty damn good.  I'm gonna play around with the caps in the HF section, got some styrene caps to try out, the polyester caps seem kinda weak.  Also since having these PCB's made there have been some adjustments to the layout but nothing that should make a difference sonically.

So, there you have it.  I guess if enough people are interested I can do a small run of PCB's.

-Casey

 

[3nity]

Im in for 2 boards.Thanks

 

[benlindell]

I'm in for 2.

 

[atticmike]

two as well

 

[home_listening]

I'll take four if it goes ahead! Thanks.

That is an elegant looking layout, nice work.

 

[Dr_J]

Hi,

greate project!!
Count me in for 2!

 

[chrispbass]

should be good for 2!

 

[jandoste]

Count me in for two please!
Awesome!

 

[Indecline]

Excellent work! I'd definitely be in for at least two!

 

[websoul]

2 please!

 

[frazzman]

Count me in for 2 at least. What would you say the rough cost per channel is ??

 

[mitsos]

might be in for two pcbs...

 

[JayDubrek]

Hi Casey...put me down for at least 4...
cheers
Jay