SSL 9K & 4K (E Series) 500 / 51X NEW BOARDS Mic Pre Thread 2011

[Ricardus]

But now i recognize another Problem. The low cut pot sounds not like it cuts frequencies where it should do.

By turning cw it Sounds like some kind of sweep eq. It seems to boost the frequencies. I dont get it. Very Strange.
I think that i populated Everything the Right why. So i dont Know

Did you calibrate the HPF? It needs to be calibrated to work properly.

There are two pots on the board. One is to properly shape the "knee" of the filter, and the other is to gain match it to the volume when the HPF is switched off.

So if the knee is currently shaped with a peak (as opposed to being flat) the filter will cut lows but also raise the frequencies right at the point where the cutoff frequency is set.

If you're using the boards from PCB Grinder then you also need to fix the out of phase output issue. It involves cutting two PCB traces and running two jumpers.

 

[frejo89]

Youre just so great- thank you! Completely forgot that !!

Concerning the out of Phase output issue. Mine ist from pcbgrinder. I dont now the exactly Revision. But it Shows something like „bruno2000“

https://www.pcbgrinder.com/produktside/9k5-500-series-preamp
I ordered it in october 22

 

[frejo89]

Did you calibrate the HPF? It needs to be calibrated to work properly.

There are two pots on the board. One is to properly shape the "knee" of the filter, and the other is to gain match it to the volume when the HPF is switched off.

So if the knee is currently shaped with a peak (as opposed to being flat) the filter will cut lows but also raise the frequencies right at the point where the cutoff frequency is set.

If you're using the boards from PCB Grinder then you also need to fix the out of phase output issue. It involves cutting two PCB traces and running two jumpers.

Can you Tell me How to fix this issue ? When my pcb is the affected one ?

 

[Ricardus]

Can you Tell me How to fix this issue ? When my pcb is the affected one ?

Which issue are you talking about?

 

[frejo89]

Which issue are you talking about?

Sorry. You were talking about These issue to fix on pcb:

„If you're using the boards from PCB Grinder then you also need to fix the out of phase output issue. It involves cutting two PCB traces and running two jumpers“

So were do i have to cut the traces and Running to Jumpers

 

[Ricardus]

There is a drawing on this thread somewhere. I have the drawing on my computer at home so I will post it later.

What about the HPF calibration. Did you already do it?

 

[frejo89]

There is a drawing on this thread somewhere. I have the drawing on my computer at home so I will post it later.

What about the HPF calibration. Did you already do it?

I already did the calibration. Its really a pleasure right now - I like it.

Ok - no stress to yourself. Feel free to post later, I will have a look at this.

Goog night!

 

[Ricardus]

I already did the calibration. Its really a pleasure right now - I like it.

Ok - no stress to yourself. Feel free to post later, I will have a look at this.

Goog night!

Here is the PDF. This view is from the component side of the board but the traces that need to be cut and the jumpers all go on the back side of the board.

 

[frejo89]

Thank you ! Working all fine now !
Great Preamp !

 

[Ricardus]

Thank you ! Working all fine now !
Great Preamp !

Excellent.

I love mine. I use them all the time.

 

[frejo89]

Hey together. Still stoked about my SSL 9k.

Another question :
Is there some mod of line in for the front? Or no chance to do this for having line jack in front in addition?

 

[emrr]

maybe @bruno2000 is also still a member here?

He (Joe Neil) passed away in 2018.

https://www.legacy.com/us/obituaries/atlanta/name/joseph-neil-obituary?id=19767035

 

[Ricardus]

Ellijay. Wow. I'm not far from there these days.

 

[frejo89]

He (Joe Neil) passed away in 2018.

https://www.legacy.com/us/obituaries/atlanta/name/joseph-neil-obituary?id=19767035

oh no, iam sorry. That is very sad to hear

my dad also passed away in 2018

 

[JAY X]

He (Joe Neil) passed away in 2018.

Joseph Neil Obituary (2018) - Ellijay, GA - Atlanta Journal-Constitution​

View Joseph F. Neil's obituary, send flowers and sign the guestbook.
www.legacy.com


Sad to hear that!. R.I.P.
His Legacy in audio will continue with us.


I have some questions about the input impedance of the 9k5 preamp. It is all about the PAD circuit i think....

With the PAD switched OUT ¿What impedance see a Dynamic or condenser microphone? 10k8 at each side (+IN & -IN)??...
These 10k8 resistors are in paralell with the input traces, so in theory 10k8//0R = 0R??

With the PAD switched IN, I understand that any mic will see the two 10k8 and one 2k2 resistor across +IN & -IN.. ¿Right?
23800R for line input level.

To make a condenser or dynamic microphone see a suitable impedance (around 1000-1300R) should i activate the PAD always?
With the PAD switched out the 2k2 resistor is not across the +IN & -IN. So how does any mic see a suitable impedance...

I'm sure I'm missing something important!!

Thank you for your help!!

Jay x

 

[JAY X]

Attached is the preamp schematic, to see what I'm talking about.

 

[JAY X]

Ok....Now I see... The minimum impedance that any microphone will see with this preamp is 10k8 on each polarity, so 21k6 balanced impedance. 10k8/1k1 (half U pad), makes a 20dbu pad.

If i want to lower the input impedance to 1k2 or 2k4 balanced for some condenser microphones, then the pad, if activated, will only reduce the level of microphone input by 0,75dbu: (1k2/1k1) (half U pad).

Jay x

 

[wreutz]

Hi all,

I just finished my build of this (rather challenging build regarding amount of documentation and forum threads to read) and have only partial success

Checked all +/- 15 V pins on all ICs: check
Added all ICs and fed a Testsignal to the input: check, LEDs light up, input volume changes when turning, pad is working, so far so good

BUT: I have absolute NO OUTPUT :-/

narrowed down the problem:
Pin 4 of the THAT1646 shows a clean sinus signal and it changes amplitude when turning the input volume knob
On the output pins 1 and 8 I get a very very low signal but it changes a bit its amplitude when changing the input volume but the amplification is way too little.
Any Ideas?
There are not a lot pieces involved in this problem.
Changed the THAT1646 -> no change
What could it else be? diode bridge? the two capacitors C4 and C5?
These are bipolar but have a + sign on the PCB and in the schematics???

cheers from Austria

 

[culteousness1]

Check all solder connection of that area. The problem is most probably related to the output section.
IIRC, the plus symbol is on the board due to the fact that a bipolar cap was missing in Neil's eagle files.

Best of luck and keep us posted!

 

[wreutz]

That did the trick!!
Thanx a lot. I have 30+ years experience in electronics and built some DIY audio projects and soldered countless cables and multicore cables and multipin connectors but still a solder connection got me this time

Resoldered all pins of IC4 and the surrounding pins and now it works!
I will definitely check / re-solder all other connections as well to be on the safe side

After that: calibration.