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

[atticmike]

On ssl9k both trimers are for HPF calibration purposes but I'm not totally sure on 4k...

Arnau

oh, so both are for calibrating the HPF?

Damn, because both of my channels are sort of dead. Whereby one breaks out if i crank it all the way up, sounding very noisy. Any idea what the issue might be?

 

[Apache5]

on 9k5 R226 adjusts the "knee" of the HPF and R3 adjusts the overall gain of the HPF section.  If yours is the 9k5, and you deactivated HPF, trimers are useless and they are on a not used branch of the circuit. Be sure you have correctly deactivated de HPF, I dont know how you can do that exactly... I think this has been explained on this thread at some point, but must be easy, look at the schematic. I can't help much debuguing it sorry...


Arnau

 

[atticmike]

got it working

Just didn't connect the xlr out on one channel properly.

 

[ylagandre]

First of all I'd like to introduce myself as a filmmaker interested in converting the SSL 9K into a portable preamp to record with my Tascam DR-40. This would be my second amp build and I am interested in modifying the HPF to have two settings. At first I thought the three gang pot was to control the HPF but when I looked at the schematic I saw that R9 is no where near the HPF circuit. Please forgive the basic question, as I am new to audio equipment and electronics, but what is the three gang pot for?

 

[Harpo]

First of all I'd like to introduce myself as a filmmaker interested in converting the SSL 9K into a portable preamp to record with my Tascam DR-40. This would be my second amp build and I am interested in modifying the HPF to have two settings. At first I thought the three gang pot was to control the HPF but when I looked at the schematic I saw that R9 is no where near the HPF circuit. Please forgive the basic question, as I am new to audio equipment and electronics, but what is the three gang pot for?

Welcome ylagandre.
The tripple 47K rev.log pot R9 (each gang in series with 2K, giving adjustable resistive range between 2K up to 49K) is setting the HPF in conjunction with the 220nF caps C203,C204,C205. Pot dialed in full CCW (49K) set this HPF to 14.76Hz on paper, pot dialed in full CW (shorted out, remaining resistance 2K) set this HPF to 361.7Hz on paper.
1st.stage is a 1st.order 6dB/oct. slope HPF, followed by equal parts value 2nd.order 12dB/oct. slope Sallen Key HPF.
Attenuator R13/R3 in front is used for compensating the K=3 gain of the 2nd.filter stage. Trimmer R226 is used for tweaking the damping d, set by R223,R226 for K=3-d gain.

 

[ylagandre]

Wow, thanks for the welcome and quick reply, which cleared somethings up for me... I'm trying to "clone" the Sound Devices MM1 and in their manual it reads "High-pass filter with two selectable corner frequencies, 80 and 160Hz, 6dB per octave." I want for the interface of my amp to be as stripped down and utilitarian as possible. That means I'd like to control the HPF with a single toggle switch with an 80hz, 160hz and off position. In order to do that can I just bridge the HPF circuit switch into the on position and replace the three gang pot and series resistors with a simple three step attenuator? What is the formula to determine the resistance necessary to cut a given frequency (on paper of course)?

 

[Harpo]

6dB/oct slope HPF, single toggle switchable at 80Hz/160Hz/bypass without cutting traces might look like this.
-3dB cutoff frequency is set by 1/(2*PI()*R*C) with R in ohm and C in farad.
Solving for R with cutoff 160Hz is 1/(160/(1/(2*PI()*220E-9)))=4,521.45ohm. Next avail standard value is 4K53, substituting the series string of R215+deck1 of R9.
The On-Off-On toggle in the lower On-position halfs the cutoff frequency for 80Hz by paralleling a 2nd. 220nF cap; the upper On-position shorts out C203 for your bypass setting; toggle in center/Off-position set HPF for 160Hz.
Compensation cap C231 might need an increase to 22pF to keep IC208 stable.
Don't fit the dotted parts.
good luck.

//edit: corrected 'None' with 'Off', see following post.

 

[bruno2000]

6dB/oct slope HPF, single toggle switchable at 80Hz/160Hz/bypass without cutting traces might look like this.
-3dB cutoff frequency is set by 1/(2*PI()*R*C) with R in ohm and C in farad.
Solving for R with cutoff 160Hz is 1/(160/(1/(2*PI()*220E-9)))=4,521.45ohm. Next avail standard value is 4K53, substituting the series string of R215+deck1 of R9.
The On-None-On toggle in the lower On-position halfs the cutoff frequency for 80Hz by paralleling a 2nd. 220nF cap; the upper On-position shorts out C203 for your bypass setting; toggle in center/None-position set HPF for 160Hz.
Compensation cap C231 might need an increase to 22pF to keep IC208 stable.
Don't fit the dotted parts.
good luck.

Nice!  But wouldn't that be an on-off-on toggle?  Center off?
Best,
Bruno2000

 

[Harpo]

Nice!  But wouldn't that be an on-off-on toggle?  Center off?
Best,
Bruno2000

Depending on vendor, yes. (at least C&K or NKK calls this switching function on-off-on),
essentially switch center pole connecting to either of the throw positions, center position available with open connection.

BTW I am missing the sense of the 10K R224 as drawn, only loading IC205. I'd expected this resistor in series to the R226 shunt arm trimmer for calculated total shunt arm value 11K25 instead. Could you comment on this?

 

[ylagandre]

Thank you for so generously sharing your know-how... I am of course full of questions. I noticed that there is a version of this project with a transformer and one without. Could someone elaborate on the audible differences between the two?

 

[okgb]

This thread contains TWO preamps , the 9K5 and the 4K 
the 4k uses the input transformer , the 9k5 does not .

 

[Toure14]

Where is the BOM for the 4K5 or better yet does someone have a mouser cart already put together that they can share?

Thanks

 

[bruno2000]

Where is the BOM for the 4K5 or better yet does someone have a mouser cart already put together that they can share?

Thanks

Link to BOM with Mouser part numbers is in first post.
Best,
Bruno2000

 

[Toure14]

What threw me off is the link  is for the 9k5...

Is it the same for the 4k5 as well?

 

[Toure14]

I need the most updated 4k BOM or cart if someone would be willing to share it

Thanks

 

[bruno2000]

What threw me off is the link  is for the 9k5...

Is it the same for the 4k5 as well?

Sorry!  The 4K5 BOM is on page 3.

http://www.dopplerstudios.com/pictures/SSL4KBOM11.pdf

Best,
Bruno2000

 

[Toure14]

Thanks for the speedy reply Bruno.

I have a few more questions on the clarification side of things then it's order time..

I noticed a few members were catching missing resistors or component parts that were not listed on the bom iinitially or listed incorrectly on the BOM (I think one example was 27 resistors instead of 25 for one of the builds). Have these small issues been corrected?

You also mentioned that the original transformer was the Jensen in both the 9k5 and the 4k5 correct? If so what is the part number? Or if it was mentioned already what page of the thread?

Last, and I know this may be reaching or possibly the wrong thread...but do you know of anyone or (build thread) who has built the ssl bus compressor in the 500/51x format? Or the EQ for that matter?

I'd love an DIY SSL complete channel strip. Only one I know who is even remotely close is Igor who builds a 4k compressor but from what I have seen on his threads and post from his customers it might be years before I get my stuff or not at all...sad


Thanks in advance
G

 

[bruno2000]

Thanks for the speedy reply Bruno.

I have a few more questions on the clarification side of things then it's order time..

I noticed a few members were catching missing resistors or component parts that were not listed on the bom iinitially or listed incorrectly on the BOM (I think one example was 27 resistors instead of 25 for one of the builds). Have these small issues been corrected?

You also mentioned that the original transformer was the Jensen in both the 9k5 and the 4k5 correct? If so what is the part number? Or if it was mentioned already what page of the thread?

Last, and I know this may be reaching or possibly the wrong thread...but do you know of anyone or (build thread) who has built the ssl bus compressor in the 500/51x format? Or the EQ for that matter?

I'd love an DIY SSL complete channel strip. Only one I know who is even remotely close is Igor who builds a 4k compressor but from what I have seen on his threads and post from his customers it might be years before I get my stuff or not at all...sad


Thanks in advance
G

The parts in question were the bypass caps, and I believe that has been fixed.
The transformer is a JT-115.  The 9K does not use a transformer.
I can't comment on the compressor, although I have bought boards from Igor and did not have a problem.
Best,
Bruno2000

 

[Toure14]

There is provision for a Zobel network, and / or R loads / C loads at the secondary of the input transformer.


What are the above networks for? Excuse my ignorance

 

[CJ]

transformers can have resonant peaks past the audio range which may be many times the normal sec voltage, so the networks are to tune out these peaks,