SSL 9K Mic Pre

[Harpo]

I have a little trouble finding where to connect the leads on the pcb from the gain pot.
The problem is that i don't see it clear for the A side.

have a look at the pictures from maybe previous page of this thread (there are others), or follow the pcb traces to spots of known component placement to identify the missing link (hint:both between R109 and C59, labled 'A').

I Know that B pot goes to R81 on the board, and Rb39 pot goes to R115 on the board.

Or the other way round, doesn't matter. Just to make sure, Rb39 is not a part number, this resistor 'Rb' has a value of 39 ohm, one leg connected in series to the pot, other side to pcb. Same as 'Ra', but value 27 ohm. These resistors set/limit the max.avail gain when the pot is dialed full cw (=zero ohm).

Also i will use mono shielded wire and i don't know where to connect the shield and the signal.
I think B pot r81 is shield and Rb 39 is signal.

No. Both ends carry signal with the shunt resistor (Ra+VR3a or Rb+VR3b) in between.

 

[JAY X]

Hi Harpo,

To make it all more clear i attached an image:

The gain points are clearly labelled in the pcb board, and i found some time ago the gain pot wiring image.

My problem is to identify the right hole on the pcb to put in the wires coming from the gain pot.
There are 2 A and B gain points, the wires comming from the resistor on the gain pot should go to the right hole in the pcb, and the same for the other side of the gain pot...
And here is where i start confusing myself...

Well, have a look to the image, and see where are the mistakes.

Thank you Harpo

JAY X

 

[Harpo]

Or the other way round, doesn't matter.

Nothing wrong with the image. A resistor is not polarized. This series resistor, containing a fixed (the 27R or 39R) and variable part (the pot, wired as rheostat), add up to a variable resistor with the min.value of the fixed part. It is still a 2-legged device. This is not a voltage divider (3-legged device) where part orientation might matter. Just for the fun of it, take a multimeter, set for measuring resistance. Attach one lead to the free end of the resistor, the other lead to the free end of the pot. Note the measured value. Now flip the leads connected to the multimeter. Compare measured value with your noted one from previous test.

 

[JAY X]

Thanks Harpo,

In the next days i will try to wire this, and tell you what happens.

JAY X

 

[bruno2000]

Here's a question that has always puzzled me about the 9K.  R122 (6K8) and R123 (100K) are in parallel.  That combo yields 6K367 ohms.  You can get a 6K34 1% resistor.  Is that not close enough?
Thanks!
Bruno2000

 

[stereokillah]

hello guys ,

i've build two unit dual mono the first withJLM di opamp and the second with JLM DI fet.

All work fine but just one thing the unit with fet DI give a bad sound up to zero Db i power on, it's seems to be the relay cause if i make it of without let the the relay to be off i and i power on the unit the sound do not present.

i've tried to inversed the di and it's the same problem, where is the fet the sound follow.

Also i've tried to make a differnet way ground for this di and nothing change.

SOmeone have idea please?

 

[3nity]

the JLM FET di induce hum into my 2 1290s. ...

??? ??? ???

 

[stereokillah]

don't have hum i've chance , only a bad sound like bip when i power the unit on.

 

[stereokillah]

In fact 3nity , i also hum but just when i use the DI enter

 

[stanz]

I too have hum from a pair of JLM FET DI boards. Put them in on ch 1 & 2 of a 4 ch SSL9K. Works great when no DI, just mic input. I have tried various configurations f power supply and ground source. Tried 48v and +18 for power. Tried shield from signal cables as schematic for the old version of JLM DI suggests. Tried separate ground wire to main ground point of power supply.

The DI circuit has a relay to switch signal source. Circuit can be powered with anywhere from +12v to +48v. Take mic input into JLM DI, output continues to preamp board. Signal source switches between Mic input or DI jack. No hum when switched to mic input. Seems to me it should be very straight forward.           


JLM does mention if DI is used externally and powered with phantom power it should feed a transformer. Not sure why it would matter if it is in a preamp or a stand alone box.

 

[ytsestef]

Today I finished soldering my 9K, everythings seems fine (without ICs mounted), voltages are correct etc. Now I need to drill the case and mount everything up to ground it. Pics probably coming soon if it works!

The LED resistor (330R/2W) get VERY HOT (too hot to touch) after a while. Is this normal?? I found the value using an online calculator. It actually is very bright so I'll try some 1k-2k resistors tomorrow but I only have 250mW ones. Will they do? How do I know what the correct power rating is for LED series resistor? Why does it get so hot?? The regulators don't seem to bother at all (not even warm).

 

[mitsos]

Don't use online complicators. They suck. That's a very low resistance for a LED R (probably calculated for max current?).  Do the calculation yourself using Ohm's Law (V=IR, or actually R=V/I) to find the resistor value based on the current you want in the LED (more current = higher brightness and vice versa) and then P=IV to get the resistor's power rating.  You don't want to be anywhere near max current unless you want blinding LEDs.

 

[ytsestef]

Don't use online complicators. They suck. That's a very low resistance for a LED R (probably calculated for max current?).  Do the calculation yourself using Ohm's Law (V=IR, or actually R=V/I) to find the resistor value based on the current you want in the LED (more current = higher brightness and vice versa) and then P=IV to get the resistor's power rating.  You don't want to be anywhere near max current unless you want blinding LEDs.

Thanks! I take it that in this case V = the difference between the input voltage and the LED voltage (2.4V). So 18 - 2.4 = 15.6
I guess 13mA should be OK for "not blinding brightness" - the led current max rating is 25mA, so that makes half of it.
So: 15.6 / 0.013 = 1200

And for power rating:

0.013 x 15.6 = 0.2028

Did I get this right? If so, seems like a 1k2 1/4W resistor will do OK, right?
I will try this tomorrow, but I still don't get why does the 300R 2W resistor gets overheated  ??? ???

 

[mitsos]

That's pretty much it. 1K5 might give you a better margin. Try and find the brightness you prefer.

Your 330R was getting hot because it was dissipating 3/4W... That's pretty hot I believe. Btw, I get 47mA there, I'm surprised your LED survived. But it is within normal operating conditions for the 2W resistor, that's why it got hot but didn't smoke. And your regulators (assuming lm7818) can do 1A. Neither the SSL nor the LED need much current, that's why they weren't running hot.

 

[freq_a_beat]

Hey All,

Just a question. I want to order the GSSL and the Neumann pbc's, but I'm a little lost. When I look at the list of materials for the GSSL clone, I dont know what exactly to order. There are several variances of some of these items. Can anyone give me an actual list of materials and where they purchased each? I want to build both the Neumann and the SSL. PLEASE!!!!!!

 

[mitsos]

That's part of your new found hobby. Get ready to spend hours at mouser, digikey, newark, etc.

wrong ssl thread btw (this is the mic pre thread, not the comp), but anyway... click in the search box and type "Greg's parts lists" (without quotes).

Greg made 2 parts lists for the GSSL comp with digikey/mouser numbers. I don't know if anyone has a list for the neumann, but it is very simple, you can order the parts from mouser (or better yet TAW has much better prices on Wimas, but I don't think they like to do reistors unless you're getting 50 or 100 of each value, still cheaper than going to Mouser). The tricky thing about the neumann is the pots. The sfernice pots are pricey, you could use Omegs but (I recently found out) they are too tall to fit in a 1U enclosure if fitted to the PCB. Sfernice are available at www.audiomantenance.com. IF TAW are out of Omegs you probably have to get them direct.

 

[Whoops]

Sometime ago there was a thread in the Black Market of someone selling MAT02 from Hong Kong.
I think the price was 50 dollars for 10 MAT02.
I have the link for the thread, but it doesn't work anymore.

Does anyone remember the name of the forum member that was selling them?
Or anyone has an email contact?

thanks

 

[flintan]

What is the input impedance of this pre? Is it possible to make it variable in som way?

 

[signalflow]

If you can find it I believe the original schematic for the 9000 has impedance switching.
Tried finding the original but had no luck, maybe contact SSLtech since the DIY 9K was his design and
ask if he has the original or know where it's posted at.  Then let me know!! ;D ;D ;D

-Casey

*EDIT*  Found it, I had it all along.  Which would explain why I remember seeing it!! ;D ;D ;D ;D ;D

File sent to the group mail account to keep the rest of the 9000 schems company!

 

[flintan]

Ok thanks! That's interesting!

Not sure if i read the switching scheme correctly.. In "low z" connection there is a 2,2k resistor in parallel with input pos and neg? And then there's a U-pad with 10k in series and 2,2k in parallel when engaged, and 22k in parallel while inactive?

What is the 22k resitor, R103 good for? It's sitting across the phantom power resistors so it shouldn't make much difference?