SSL 9K Mic Pre Thread 2009

[TheGuitarist]

http://www.groupdiy.com/index.php?topic=36799.0

i'm running a group buy if you're interested at all. But you can get the pots from www.audiomaintenance.com  they are 2k2 reverse log dual gang pots.

 

[RedNoise]

hi Guitarist!
You got to to change a "e" for a "a" , otherwise link do not work ! 

 

[sonolink]

Same here

 

[pedrocruz]

Hello to all,

I have a question about the PSU, i imagine this question im about to make has been answered already but with so many SSL 9k posts in kinda lost...

Is it possible to make the PSU capable of power 8chs of SSL 9k?
Im building in a near future 8 ch of SSL 9k preamp. I was thinking of building 2x PSU to power 4ch each PSU, but ive been told that with some mods to this PSU design maybe i could power 8chs with one PSU only.
I imagine i would need more VA from the transformer but would i need to change anything else in the PCB?

Any help is hilghy appreciated!

Many Thanks!
Pedro Cruz

 

[mitsos]

Pedro, here is a quote from PRR about ssl9k current. Seems like 8 channels should run just fine off one PSU.  Get a 2x20VAC trafo (minimum 25VA) and you should be OK.

The supply current for this preamp is under 40mA per channel. 8 channels would be 300mA. I do not see this PS schematic, but assuming it is conventional you should use a 600mA to 1A transformer, and fairly good size heatsinks on the regulators, like 2 inches 5cM square.

The drain of the 052 is so small I would just use 15V Zeners with say 1K resistors for one channel, 150 ohm resistors for a +/-15V supply for 8 channels.

 

[pedrocruz]

Hi Mitsos, Thanks for your reply,

I was told that for the +/-15v i would just need to solder a 3v zener Diode from +18v ---3vZener--- +15v and the same for -18v ---3vZener--- -15v.
Im not sure yet where is the Cathode side but that would be simple to find out with a multimeter.

The Quote you wrote he talks about resistors. would i need them? how would i connect them?
Sorry im roakie in electronics...

The drain of the 052 is so small I would just use 15V Zeners with say 1K resistors for one channel, 150 ohm resistors for a +/-15V supply for 8 channels.

Cheers and Thank you

 

[mitsos]

I don't know about the zeners, never used them here but seems like a good idea.  Most people just use a string of normal diodes, 3-5 or so per rail, since they each drop about .6-.7V or so.  There are diagrams on how to hook them up.  The line on the diode is the cathode. Anyway, if you're doing multiple channels, put the diodes on perfboard to get your voltage down and run wires from there to each channel's +/- 15V pads.

 

[pedrocruz]

Ok Mitsos,
Thanks for the help!

So basically, to power the channels, i only would need to get a trafo that is more powerfull than 25VA right?
And what about the 48v? in worst case scenario, having 8 condenser mics with phantom power on, is the 25v trafo+circuit capable of handling those 8 mics?

Thanks
Best Regards!

 

[audiophreak]

  Hi,
    ..... sorry if this has been covered but don't recall seeing  it.... what is " Ra, Rb, Rp1, Rp2 " in the BOM, I don't see anything on the PCB with that designation ?

 

[mitsos]

Ra and Rb are part of the gain circuit, they are soldered between the gain pot and the PCB. Check other SSL9K threads for pics if you need.  Rp1 and Rp2 IIRC are the 6K8 phantom resistors, they are not onboard as there is no phantom circuit on the board. These go to XLR pin 2 and 3, respectively, the other ends are tied together, and go to the phantom switch/circuit. 

 

[audiophreak]

Thanks mitsos  ! 

   

 

[audiophreak]

Helloo again... ;D

  I think I read somewhere in the 9k threads that the 5534 has a max voltage of 22v,in checking the data sheet, that is a fact, ( at least for the ones I have )  in ordering the TL052, noticed that the max voltage of it is  + - 15v , is this the reason that this project needs + - 15v and + - 18v ?  and is there an alternative to the TL052 so the whole project can be + - 18v  ?

  Thanks,  sorry if this has been covered ...

 

[audiophreak]

  ... I guess that had been covered.. :'(

  ... moving on.... I cant seem to find the 3.3pf and 10pf in film caps, only monolithic multi layer and ceramic disc, are these what people are using ?
  any suggestions ?
 

  Thanks  ;D

 

[mitsos]

just use ceramics.  C0G/NP0

And yes, the +/-15V is for the TL052.  Some people have also used IIRC, the TLE2072, which can handle +/-19V.

EDIT: forgot to clarify that if you use this (or another chip with low offset V/drift that can handle +/-18V), you obviously won't need +/-15V, and can just run wires from your +/-18V to the +/-15V pads.

 

[audiophreak]

Thanks again mitsos , very much appreciated  ;D

 

[audiophreak]

Hello again  ;D

  Question about the PSU board, I think I saw a pic of someones build and saw a piece of aluminum for a heat sink on the voltage regs bolted across all three.... can this be done in this project ?

  Thanks

 

[briomusic]

if you screw all regulators to the same piece of metal (including, for example, the enclosure) you have to electrically isolate them. this is done with a thin piece of plastic between the reg and the metal and a T-washer around the screw. it is important to check that there really is no continuity between the v-reg and the piece of metal before powering up.

 

[audiophreak]

Thanks briomusic !

  I think I've found a solution.

 

[TheGuitarist]

Hey guys, having a bit of an odd problem. In my 4 channel 9k pre, i have 3 channels working but one not. So i went hunting around, checked that it was getting the 18vs and 15vs, getting audio to the board etc. Getting all of that, i looked at my solder job and i didn't see any shorts or anything like that, so i proceeded to check that i'd mounted all the ic's properly.

I touched IC24 which looks to be the output IC and it was hot, i mean heatsink on voltage regulator hot. Now this can't be good. Can anyone think as to why this may be happening?

I checked the voltages and i didn't see anything unusual there, but maybe i missed something.

Any help you could give would be awesome. Or even if there is a way to test that the audio is getting through all up until the last chip that'd be helpful.

Oh yeah, also, i switched out the chip so unless i have 2 bad chips, its not that.

Also if it means anything the transformer is acoustically buzzing VEERRRRYYYY quietly. The other channels are fine, just thought i'd mention that.

 

[TheGuitarist]

bit of an update, i switched out a cap and now i'm getting signal, but its really distorted.

I also tried switching out all the ics as well.