SSL 9K Mic Pre

[marshman]

After further investigation, that one channel is much worse than the other. The one is almost perfect, while the second has much more noise.

Can anyone direct me on what to look for? I have inspected all solder joints and components and everything looks ok. I have swapped out all the chips and that changed nothing.

I am thinking that next I should pop all the chips out and measure for DC milliamps at pins 2 and 3 of all the sockets to try and narrow down where the DC might be sneaking in. Am I heading in the right direction?

Anyone?

mm

 

[kato]

Previously, Andy Millar mentioned that the 2.2uF input caps should be high quality.

By input caps, I'm assuming: C69 and C55

But what about C84 and C68 - the ones behind the IC's, also 2.2uF.
Should they also be high quality?
(they have slightly narrower lead spacing.) Does audio pass through C84 and C68?

 

[MartyMart]

[quote author="kato"]Previously, Andy Millar mentioned that the 2.2uF input caps should be high quality.

By input caps, I'm assuming: C69 and C55

But what about C84 and C68 - the ones behind the IC's, also 2.2uF.
Should they also be high quality?
(they have slightly narrower lead spacing.) Does audio pass through C84 and C68?[/quote]

Yes audio does pass through 84/68 also so I would recommend decent caps.
The lead space was a touch smaller so I used WIMA 2u2 50v caps here with
a 5mm lead stretching across the 7.5mm optional holes.
50v is fine on the audio PCB as the max voltage is +/- 18v.
MM.
Marshman , have you checked that your 2k2 pots are fine ?

 

[kato]

Thanks MM! I appreciate the response!

 

[mitsos]

Hey everyone, I'm trying to get my ssl9k's together, and I'm almost there.. I've got one channel all together ready to be powered up. ALMOST. I just can't seem to get the put-two-diodes-in-series 15V thing right.

Background: when I first wired the PSU the negative rail was around -22V. I read somewhere here that it may be because it was unloaded, so I strapped a 3K9 resistor on it and it went straight to -18V. Good. The other rails were at +18 and +44V.

So I put two pairs of 1N4004 diodes in series (one pair for + and one for -). I put them in the way I read here, the anode of the first pair to the +18, and the cathode of the second pair to the -18V. But when I powered it up (with the 3K9) the "15V" positive rail went down to 17.4V (less of a difference that I had hoped, but at least it's working) BUT the voltage after the diodes on the negative rail went to -18.6V! How? The -18V was still -18, so I don't get it... How could the diodes make this more negative?

Thanks for the help..

 

[Svart]

which way did you face the diodes on the negative rail? Remember, they face the opposite direction then they would if you had them on the positive rail.

As far as the drop, what type of diode are you using to drop voltage? Silicon diodes can have anywhere from .5 to .2v of drop depending on their design and usage. Schottkys and other types can have down to .1v of drop so you really need to know what kind you are using because you could have 4 or more diodes in series before you get close.

I'd just get some +/- 15v regulators and be done with it. Get them in the isolated TO-220 style, attach them to the case and run some short wires to them. You'll be fine.

OR you can just run it all on +/-15v... the difference would be a dB or less.

 

[mitsos]

hey Svart, I am pretty sure I faced the diodes the right way, they way they are listed on the "corrected SSL9K schematic" and in the DrPat's diagram on page 7 of this thread...

I am using some 1N4004 that I had lying around. Two on each rail, on the positive I'm getting .6V drop, so 0.3 each? I have to see if I have the right regulators (I live in a small town, so no way to buy any until next weekend). If I do find them, would I connect them to the legs of the +- 18V regulators? Would I put caps after like on the PSU?

I had previously tried with 3x 1N4148 on each rail, but the results were about the same (similar voltage drop). And the negative rail voltage increased with these also.

Can I try reversing the diodes on the neg rail? Is that dangerous? In the blowing up a PSU dangerous?

Like I said above, to get the negative rail to sit at -18V I had to short it with the 3K9 resistor. I kept this resistor in place for the above testing otherwise the neg rail went up to -21 volts. I am going to try moving it to the -15V rail to see what happens.

 

[mitsos]

ok, so that did it... I moved the resistor from the -18V rail to the "-15V rail"... And now I the voltage decreased. I am getting -15.9, I assume this is within safe limits?

thanks for the help svart.. appreciate it.. still have to get those 2520s together by the way. the ones you sent me. I originally messed up my mouser order.. some stuff was too big other stuff was smd!

 

[RedNoise]

Hi there!
I'm sorry to ask this following question , but as I'm noob , I just want to learn...
>>>Could someone give here a complete wiring diagram???



I've tried , tried , and read many threads about the 9k...but I'm lost.Sorry!
Thanks.

 

[kato]

[quote author="RedNoise"]Hi there!
I'm sorry to ask this following question , but as I'm noob , I just want to learn...
>>>Could someone give here a complete wiring diagram???
[/quote]

Are you looking for the schematic? Its hosted here at SSLtech's place:
http://www.beatbazar.com/guests/ssltech/9k/9k-schem.pdf

Or are you asking about the whole, how to rack an SSL9k.
That's no different from any other project here. But be aware, the 9k project has no pad and no DI. So if you've seen completed builds with DI / LED meters it means they've used add-on solutions like JLM's DI kit and the
Keef's bargraph driver.

The boards are labeled so if you just sit down and start hooking it up, I think it will pretty self-explanatory.

Post any specific Q's here and I'm sure collectively we can help you out.
I haven't built mine yet but I can document the basics for you when I get around to it. Are you ready to rack now?

Also see meta:
http://www.groupdiy.com/index.php?topic=8852

 

[RedNoise]

Hi Kato!
I've got all the schematics and have done a "humble" lot of researches about this pré,but thx for givin all that links , so helpfull...

-My problem is that I just fear to burn something by wiring the different pcb each other.I'm not affraid by rackin a unit(I've yet done some"humble" DIY :wink: )
I'm not shure how to 'split' 18v rails to 15v...I saw Patrick's schematic , think I understand how to do , but I'm not sure how to split teh rails : I want to put two or four pre in a 1 unit tall.Does it mean I must have 16 wires just to correctly feed them (regarding power only)???
-Same thing for the rev log 2K2:how and where should I wire them??

Six month ago I do not knew what a resistor was...It's just a new passion , completely infinite , but really passionating.So I was sorry to ask a so beginner question (again)!jajajaja!
Gone to look some pics with a magnifying glass! :green: :green:

 

[mitsos]

[quote author="RedNoise"]
-My problem is that I just fear to burn something by wiring the different pcb each other.I'm not affraid by rackin a unit(I've yet done some"humble" DIY :wink: )[/quote]

Check your voltages prior to hooking up your main boards by shorting with a resistor. Can't remember the value I used, but it's in one of these threads.

[quote author="RedNoise"]
I'm not shure how to 'split' 18v rails to 15v...I saw Patrick's schematic , think I understand how to do , but I'm not sure how to split teh rails : I want to put two or four pre in a 1 unit tall.Does it mean I must have 16 wires just to correctly feed them (regarding power only)???[/quote]

I'm pretty sure you can "daisy-chain" from one board to the next, but you wan to use connectors, instead of soldering the wires direct to the PCB. I couldn't find any 1-pin connectors so my +-15V are directly soldered.

[quote author="RedNoise"]
-Same thing for the rev log 2K2:how and where should I wire them??[/quote]

Check my thread in the lab.
http://www.groupdiy.com/index.php?topic=28684
Gltech posted a pretty clear picture on the second page. Compare with the schematic and you'll see exactly how to wire it.

most importantly, take your time. I think "measure twice, solder once" could save you much of the trouble I'm having troubleshooting hiss and DC problems.

 

[RedNoise]

Thank you Mitsos , gone to try this wiring.
Don't worry I take my time!
If I understood correctly : the sym pcb is for two mainboards??right???

 

[mitsos]

You mean the balance PCB? Yes it is for two channels. So for four channels, you will use 1 PSU (if you do the diode trick), 4 Main boards and 2 balance boards.

 

[RedNoise]

ok Mitsos.
Regarding to the psu....I may do a 2U rack...so 8 pre.
Does it mean I should build two psu with two trafo??I've a 50VA 2X18....is it enough for 8 pre??

 

[mitsos]

Should be fine:
http://www.groupdiy.com/index.php?topic=27883&start=0&postdays=0&postorder=asc&highlight=ssl9k+50va

 

[RedNoise]

thx!
very appreciated help!
EDIT: :thumb: :green: :thumb: :green: :thumb:

 

[nielsk]

Has anyone considered using THAT 300 transistor array for the MAT02? I believe paralleling the extra transistor would lower the noise floor somewhat, & not be to difficult to adapt a wire wrap socket to the dual footprint. At $3.00 a pop it seems promising, and no stock on LM394s or MAT02s anywhere.......

 

[signalflow]

Nielsk,

http://www.analog.com/en/other/matched-transistors/MAT02/products/product.html

scroll to the bottom of the page and you can see the different models and their prices. I used the FH for my 8 and they work fine and sounds great! Plus they are way cheaper. They are in stock and you can order direct that's what i did.

Casey

 

[mitsos]

I got my MAT02s direct from Analog, and they got here pretty quickly considering they came from the Philippines. Price was good, but $10 shipping sucked since I only got two..

Then I bought these recently to check if I killed one of the MATs. Still waiting for them after about ten days, hope they'll get here!

http://cgi.ebay.com/NS-Supermatch-Pair-transistors-LM394-LM394H-2PCS_W0QQitemZ280253984086QQihZ018QQcategoryZ36331QQrdZ1QQssPageNameZWD1VQQcmdZViewItemQQ_trksidZp1638Q2em118Q2el1247#ht_1601wt_0