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

[Bernardo]

measuring voltage is important, but im talking about using an audio probe here. pump a test tone through the input, attach it to different points in the audio path, and find out where the noise starts-that will tell you where to start.

What you say seems very interesting, I am going to study how to do it since I do not have an oscillator. thanks for the advice.

 

[Ricardus]

I made my measurements the tl052 has: pin 4 -16 pin 8 +16 that 1646 pin5 -16 pin6 +16 ne5534 pin4 -16 pin 7 +16except ic22 ic29 pin2 +15 pin3 +11 pin4 -16 pin6 -0.5v pin 7 +16 all very close to the scheme.

the drill sound is always,

Was this in reply to my question about whether or not the HPF switch was on? Because if you have the knee adjustment fully.... counter-clockwise (I think) that HPF will oscillate BADLY.

 

[grid_stopper]

What you say seems very interesting, I am going to study how to do it since I do not have an oscillator. thanks for the advice.

very simple and cheap to do, just be sure not to connect it to any power rails
http://diy-fever.com/misc/audio-probe/

 

[Bernardo]

Was this in reply to my question about whether or not the HPF switch was on? Because if you have the knee adjustment fully.... counter-clockwise (I think) that HPF will oscillate BADLY.

sorry for my short answer, the oscillating noise is constant, it does not matter if I turn the two trimmers to the right or left, I have tried many combinations without reference tone, from right to left, the two to the right, the two to the left ect.thanks for the help.

 

[Bernardo]

I found the problem,that1646 broken.

 

[Bernardo]

Hello again, I have a strange behavior of my unit, I do not know if it is normal in the design or it is something that I have wrong. When I cut the current of the unit after a few seconds it gives a high output signal, could it be due to the discharge of the capacitors? will this be bad for my audio converter? Thank you so much

 

[Bernardo]

Hello again! I see that this wire has little movement, just a query, my unit is noisy when the gain is increased, this is normal in this design? Maybe my transistors are the ones causing the problem ?. Thank you so much!

 

[JAY X]

Hi!

When correctly built, what is the noise figure at the output of the preamp It can be expected at maximum gain?

¿Is it normal that the last part of the gain rotation is the noisiest?

Jay x

 

[Whoops]

Hi!

When correctly built, what is the noise figure at the output of the preamp It can be expected at maximum gain?

I never seen a measurement being published here of the “noise level at max gain setting”

I don’t think anyone did it or it’s able to provide that info

¿Is it normal that the last part of the gain rotation is the noisiest?

From my experience in recording with many different preamps I would say that it’s normal. Normally the last 25% of the gain pot rotation is the noisiest, it’s also when the amplification capabilities of the preamp are on its design limits.

to know if your noise figures are higher than normal I guess you would have to have a known good unit and compare both side by side

 

[JAY X]

Hi!

Finally I think i solved it!. I just washed better the flux residues and this helped to reduce noise!!. I compared the output noise with the preamps on my umc1820 audio interface, and got simmilar or better figures at same gain de settings.

Jay x

 

[moucrthi]

Hi !

I got two 4K pres that a friend started when Bruno2000 posted this thread years ago. He put the majority of resistors and capacitors but the deal is that he gave it to me for free, but I have to finish it !

I searched where to buy Cinemag or Jensen transformers in Europe but didn't find the right ones... Then I choosed to go with the Lundahl 1538 but didn't find someone who did this choice. Is there someone here who did the 4k using lundhal transformer ? Or someone else who knows where to find Cinemag CMMI10PCA or Jensen JT115EPC in Europe ?

Thanks, have a wonderful day !

 

[Whoops]

. Is there someone here who did the 4k using lundhal transformer ?

if there is it’s in this thread

Or someone else who knows where to find Cinemag CMMI10PCA or Jensen JT115EPC in Europe ?

you have to buy them from the US.
Cinemag sells direct, Jensen I don’t remember but I think they also sell direct.

otherwise do a wanted post in the Black Market Section

 

[grid_stopper]

Jensen is owned by Radial, so anywhere you can order radial from should be able to facilitate ordering Jensen, in terms of who would actually have stock- I couldnt say

 

[Barrylime]

Is there a working link to a build manual for this kit anywhere? Mainly in relation to calibration and things to look out for. Have found slightly different bold online, and a kind person sent me one, but they’re all slightly different, and don’t always include all of the details in relation to what goes where on the pcb. Thanks in case anyone is able to help, and thanks for reading this!!!

 

[Whoops]

Is there a working link to a build manual for this kit anywhere?

I don't think there was ever any kit.

For what project do you need documentation?

 

[Barrylime]

I don't think there was ever any kit.

For what project do you need documentation?

Sorry just realised this thread is for multiple SSL preamps. I'm talking about the SSL 9K preamp. Bought the PCB from PCB Grinder. I have the BOM and schematic, but would like to find some instructions for the calibration process. Also, there is nothing on the PCB that indicates the orientation of the LEDS. I'm a noob, so sorry if these things are obvious....

 

[Ricardus]

There is a post here early in the thread about calibrating the HPF. I saved it at home.

And all of the LEDs in the meter, and on the main board have the same orientation. I need to check that when I get home, too.

 

[Barrylime]

Mmmm.. I’ll have look if I can find it. Most of the links in these old threads don’t work anymore, or require permission to view. It’s all together now. As someone mentioned earlier on in the thread, the positive anode is connected to the same trace/path, and the cathode goes to the led driver IC so based on that I determined the right orientation (I hope) testing tomorrow morning, although I kind of need to get an extension card/cable for 500s… I imagine calibrating it without that is only possible by putting it in the far left slot of a rack and leaving the rest open so screwdriver access is possible..

 

[Ricardus]

If you're looking at the boards from the angle of the front panel in this pic I uploaded, all LED anodes (positive longer lead) go to the right. Even on the 4 LEDs connected to the switches.

So when I made the first one, and I looked at the meter PCB, I noticed every other LED lead had a common trace going to it. SO GUESS WHAT I DID??

Without looking at the schematic I assumed that was the negative rail. Except after I had soldered them all in I looked at the schemo, and saw that common rail was connected to all of the Anodes. I almost destroyed the meter board taking out all those LEDs. But with some jumpers I was able to save it.

LESSON LEARNED.

Schematic also attached.

 

[Ricardus]

Here's the calibration procedure from Bruno earlier in the thread:

"Some folks that are building these have asked about the HPF setup, so here goes. It's the same for the 9K and 4K boards.
R226 adjusts the "knee" of the HPF. Start with R226 fully counter clockwise, the frequency control fully clockwise, and the HPF engaged. Then send a swept tone through the unit from 20 Hz to 5k Hz, and observe a significant "bump" in response just before it takes a dive at around 400 Hz. Adjust R226 to eliminate this "bump" so that the frequency response is flat until the HPF takes over.
R3 adjusts the overall gain of the HPF section. Send a 5k Hz tone through the unit. Adjust R3 so that the output signal level is the same with the HPF in or out.
Enjoy!
Bruno2000"

And then we need to discuss the workaround to fix the out of phase output.