SSL 9K Mic Pre

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Hi Whoops

I'm Ipin, I just finished installing 2 channels of the 9k, except the gain switch.
Do "stepped gain" that you posted work?
And is it going to work with 2 separate rotary switches? I can't find the double deck one here.
And also is the closer value of the resistors also working? again, I can't find the exact value. Do they really effect the Pre?

Thank you very much

Ipin


Whoops said:
someone asked me this file

Stepped Gain Switching for the SSL 9K
 

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Oh Sorry for newbie questions, Thank you for replying.
I'm not realy found the info about the separate switch one.

Thank You


Whoops said:
Why do ask that? would I or anyone have any interest in posting info that doesn't work?

If you are doing this project you need to read this thread first a lot of helpful info
 
ipindalieson said:
And is it going to work with 2 separate rotary switches? I can't find the double deck one here.

Hi,
I really don't know what you mean by "2 separate rotary switches", can you explain better?

You need one switch that has dual gangs/decks as far as I remember, if you don't find it we can help you sourcing that out.
If you use a POT it's also a dual gang pot

Just post the original specs for the switch that are somewhere in this thread, as I dont have that info present at the moment
 
Hi Whoops
Yer, instead of 1 dual decks switch can I use 2 single deck rotary switches? So it will be like turning them together (complicated isn't it haha)

Thank you

Ipin

Whoops said:
Hi,
I really don't know what you mean by "2 separate rotary switches", can you explain better?

You need one switch that has dual gangs/decks as far as I remember, if you don't find it we can help you sourcing that out.
If you use a POT it's also a dual gang pot

Just post the original specs for the switch that are somewhere in this thread, as I dont have that info present at the moment
 
ipindalieson said:
Yer, instead of 1 dual decks switch can I use 2 single deck rotary switches? So it will be like turning them together (complicated isn't it haha)

I really don't know if I'm able to help with that, but If you post the original specs for the switch I can help you sourcing that out.
 
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I know this thread is all but dead, but Neeno's pdf has since been removed. Does anybody have a current parts list? I've got PCB's, but other than that, I have NO idea where to start.
I have Keith’s from way back when…sorry about the colour. Maybe by 2026 we’ll have a consolidated archive on this pretty fun circuit.
 

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Looking further in this thread someone attached the pdf for Keith’s 9k. For some reason the sound always reminds me of Bowle’s let’s dance, but the switched gain stage is scratchy as hell. It’s embarrassing to show this work from 18 years ago but I’m going to have a go at finishing this now that I have a bit more time.
 

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Hi!

I have a gain noise problem!. When i turn the gain up to 3/4 rotation (3 o'clock), noise (hiss) is low, but when i turn it to the maximum, the noise is awful.: In the DAW i can see how It fluctuates up & down.... Somewhere i read that the last quarter is the noisiest, but it should not be soooo noisy!!.
Among other things, I have matched all the critical resistors!. ¿what else can i check?.

One more question: ¿what is the purpose of C45 (100nf)/C62(220uf 25v)? ¿to clean the psu rail noise?

Thank you for your help!

Jay x
 
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Mine are noisy(hiss) at full gain(72db). Figured that was par for the course with that much amplification.

I’ve also never had a scenario where I needed anything above noon. And that’s with ribbons. Honestly I keep the pad engaged on mine most of the time. But I’m a -18 type of guy so, your use may be very different.

C62 & C45 power filtering

-Casey
 
First, I would isolate it from the mic, cable, etc., by disconnecting the mic and connecting a 200-300 ohm resistor across the inputs – Input Lo and Input Hi, i.e. pins 2 and 3 of the mic input XLR. This will (somewhat) simulate the mic output impedance without the mic being connected. Power up the preamp and see if the noise is still as prevalent at high gains. If not, then the noise is coming from the mic.

If the noise is still there, then maybe swap out the 5534s with the same or lower noise op amps with the same pinouts, assuming that they are in dip sockets and easy to swap. On another note, if the MAT-02s or 5534s came from questionable sources such as eBay, Alibaba, etc., then they very well could be fake, and thus very noisy.

FWIW, I would only engage the input pad if the signal was clipping near the lowest gain setting. Engaging it unnecessarily is just asking for more noise because it forces the gain to be set that same dB amount higher which will be nosier, especially when using ribbon mics.
 
Hi!

I went to two studios, to test the preamp, and both tested the preamp at max gain. The noise is very noticeable: some numbers from my Daw peakmeters:. Fully ccw: -inf. 1/4 turn : -83,5dbfs, half turn: -60 dbfs, 3/4 turn: -47,5dbfs. Fully cw: -25dbfs.

The 500 version 9k5 , is far more silent. I bought the AS194H from banzaimusic, germany. The opamps are Ti 84AJL3M.NE5534P.

I would discard the mic, because we recorded also through focusrite preamps with the same mic. But i will do the test. For the test i just put the mic gain at maximum and record the output noise. When i see a thick trace...no good...:(

Jay x
 
The 500 version 9k5 , is far more silent.

Being it the 9000 or the 500 series versions both circuits are exactly the same, so if one of them doesn't behave like expected then you did something wrong in your build, it was a build error and you have to review the circuit/components and connections to figure it out and fix it
 
Ok whoops!!.

I did the load test with a 200R.
The numbers at the same gain settings:
Fully ccw:-inf, 1/4 turn: -inf, half turn: -80,5dbfs, 3/4 turn: -66,2 dbfs, fully cw: -47,2 dbfs.
I can't believe it!. So, what happens?. The mikes are not good enough for this preamp?... The mic i have is an akg c5 dynamic condenser microphone.
Jay x
 
Well, no wonder - the equivalent noise level for this mic is 25 dB! So yeah, you need a quieter mic.
But this preamp should work well with dynamic microphones like sm57 or 58.? I understand that a focusrite isa preamp can be more tolerant with bad mics...If i go to a studio to test it, they may use any mike available... This is my main worry now...
Anyway i will buy a decent dynamic mic and test again..
So, ok the problem is the mic, not the preamp, this is good news!!.:)
 
The C5 is not dynamic mic - it is a condenser that is apparently meant to be used as a live vocal mic, same as a hand-held dynamic type would be used. If a performer is speaking/singing directly in front of it, probably not going to need much gain and no one would notice the hiss. However, the problem arises when it's incorporated into studio use for more distant mic'ing, thus the gain gets cranked and the noise floor goes out the window.

Regarding the Focusrite or any other preamp, noise from the mic is going to show up (at the same gain settings) no matter what you plug it into.

A dynamic mic like SM57 won't be noisy on it's own (nor will a ribbon), but will need more gain, resulting in more preamp noise. But, if you have a quite preamp then noise shouldn't be a problem within reasonable mic'ing distances.
 

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