SSL9K both channels back alive! now on to the HUMMMM

I would guess the 9Ks can only be better.

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Hopefully "Better" but probably just different.

khstudio said:

BTW, Kevin, did you get my PM about the night EQ?

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He also said they are "Clean... but not clean, BIG sounding & that they almost give you the "Sense" that there could be tranny's in there. He also mentioned having a "Color" or "Sound" to them... unlike what some others have said about them JUST being "Clean"...
Good luck man.

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That's the feeling I had about the FX series pres... Seemed like there were trafos in there, which I'm guessing there aren't... Anyway, good luck on yours.. BTW, one MAT02 measured weird, the other had both sides equal.. Im going to see what happens when I swap that bad MAT02...

WOW... OK, I'm happy again... a little bit at least. On the channel with the "dead" MAT02 I swapped in 2 hFE-matched (by my DMM) BC550C and I now have sound again... Not the best sound, mind you, LOTS of hiss, but there are a few things left to do (including swapping the 550s for an LM394).  Ok, the other channel is also without a transistor ATM because I wanted to check it a couple of days ago.  Any idea what the hiss could be, besides the case not being all there? (basically just a bottom panel right now).

Weird thing is, when I first hooked it up and ran a 1K tone out and back into PT, all I got was hiss, and when I turned the gain way up, HMMMM.  At low gains the hiss hid the hum. But I did not hear the 1K tone AT ALL. The weird thing is, I don't know what I did, I fiddled with the XLR in/out wiring, the pot wiring, and all of a sudden I heard that 1K goodness. So I'm gonna check the pot connections.. I wish the two gain resistors were on the PCB... I have them soldered to the pcb, and then soldered a wire from the resistor to the pot.. Is that the best way? I ask because I already had one resistor break off. Should I solder them to the pot instead, and run a wire to the PCB?

OK hopefully the next channel will come to life miraculously and without hiss...

thanks to anyone reading this...


EDIT: 

I have them soldered to the pcb, and then soldered a wire from the resistor to the pot..

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OK, that's obviously not the way to go.. I just broke another one... the pots (and everything else, is pretty mush loose in the air right now for lack of a case, so turning the pot has to be done very carefully, obviously to me now!

and the update: I think my hiss MAY (I say may because I have no more of those resistors and can't test right now) have been due to a "line conditioner" that sat between my house power and the pre. I took it out and in the mere instants before I turned the gain knob and broke the resistor (everything is loose atm) I didn't hear AS MUCH hiss as before. Anyway, I'll do more quantitative research when I get more resistors, but I may make this fixed gain (while I'm waiting for resistors) to check the rest of the circuit.  Any other ideas where the HISS could come from though?

mitsos said:

I checked the datasheet but didn't see that info.. bad eyes I guess. Well, this sucks.. one $10 transistor in the trash.. I'm gonna go through the rest of the circuit and hopefully all will be ok in the end..
Thanks for the info...

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Page 2, 2nd.parameter. delta hfe is the difference between current gains of both transistors in this housing, indicating how close these match.

What kind of wire do you use to connect your pot? This spot is a little sensitive to induced garbage. Shielded mic cable might help this, but connect only one end of the cable shield to a 0V spot on the pcb. On one end the cable inner wires connect to pot and resistor, on the other end to the 'gain' spots on the pcb.
In a shielded enclosure with lid shut this hum/hiss should drop significantly.
just my 2ct.

I'll try the shielded cable... I had tried twisting cable til I read someone's suggestion to use straight wiring, as short as possible. But I am thinking of etching a small pot pcb to hold the pot and resistors, then at least I won't have them breaking.

I'm a bit confused about grounding this pre, there seem to be many connections to 0V, and I've cut all but one so far to make sure I don't get ground loops.

thanks for the input.. Will try the shielded cable.

I Finally finished my SSL9k Pre!  ;D

It sounds GREAT!!! No issues whatsoever. It is a completely different animal than my API & Neve 1272 pre's I'm used to.
At first I wasn't sure what I thought about it. I had drum tracking sessions all weekend, starting Saturday to Monday... so I worked on it all week hoping to have it ready to try out. Damn if I wasn't wiring it up in the rack when the band was showing up (thank God they're friends of mine)

So, the plan was to try each pre for the Overheads, Kick & Snare to hear what we liked best:
API (8ch), Neve 1272 (4ch) & SSL9k (4ch)

OK, I was pretty shocked that my API didn't sound as good as the others. 

The NEVE & The SSL9k sounded KILLER!
It was very hard to decide but in the end, the 9k was chosen for the Snare & Kick (kick had 3 mics - D112 inside, D6 just inside hole & Royer 122 Ribbon 1+ Foot in front of kick) ALL thru the SSL9k.
We chose the Neve for the overheads & the API for Toms & HiHat.

The SLL9k is Very warm, Big & Natural sounding & seems to have a lot of headroom.
What thru me off was the lack of High-End (or "hyped highs") compared to the other Pres.
BUT, you could tell that it was "EQ Friendly"... so after listening to the tracks EQ'd a bit, it was unanimous.

mitsos said:

I'll try the shielded cable... I had tried twisting cable til I read someone's suggestion to use straight wiring, as short as possible.

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I just used regular wire, twisted together, going to & from the Gain Pots & the PCB.

I'm not having problems but... Where did you see or hear the info about NOT using twisted wire?

HARPO,

This spot is a little sensitive to induced garbage.

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What kind of garbage? When you say "Induced" are you referring to inductance? or just "injected noise in general?

I do feel like this Pre is missing a little "High-End"... could these twisted wires cause that? I will try to run sweeps on it when these sessions are complete.

khstudio said:

What kind of garbage? When you say "Induced" are you referring to inductance? or just "injected noise in general?

I do feel like this Pre is missing a little "High-End"... could these twisted wires cause that? I will try to run sweeps on it when these sessions are complete.

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Hi Kevin,

by induced I am thinking of a nearby transformer (depending on circuit my solderstation for instance likes to give me this kind of trouble), neons, badly filtered switching supplies, ... When looking at the SSL 9K mic pre schematic, there might be a reason that points W33,W38,W31,W37 close to the gain setting resistors are labled 'shield'.
[quote author=mitsos]... and everything else, is pretty mush loose in the air right now for lack of a case, so turning the pot has to be done very carefully, obviously to me now!

and the update: I think my hiss MAY (I say may because I have no more of those resistors and can't test right now) have been due to a "line conditioner" that sat between my house power and the pre. I took it out and in the mere instants before I turned the gain knob and broke the resistor (everything is loose atm) I didn't hear AS MUCH hiss as before./snip[/quote]
-Harpo

Kevin, the post was from Samuel Groner, a couple posts down. I too had twisted wire, but changed it when I saw his post in this thread:
http://www.groupdiy.com/index.php?topic=28743.msg348134#msg348134

But, if yours are working, then there's no need to change...

It's funny, the lack of hyped highs, I felt in the FX series, but it had more of a subtlety in the highs.. really nice.. So Im hoping what you heard was the same.. I haven't been able to do any definitive testing on mine.. I KEEP BREAKING THE DARNED GAIN RESISTORS!!  I'm a putz.

OK, back to work for me...

OK, back to my poor little SSL9Ks... They needed a bit of love and I got some more 27R and 39R resistors so. I redid the pot wiring on the channel whose gain resistor had broken.. the same channel I posted about with the 2 BC550Cs instead of a MAT02.. It sounds fine, now, no hum, buzz or anything beyond what I am used to. I'll have to do more extensive testing but I'm happy with it!

Now the second channel also works but only at minimum gain settings. Then I noticed I wired the pot backwards! Argh.. I was even looking at a picture while I did it. Maybe that's the problem.. Anyway, I'll redo this tomorrow if I have time.. and will report back.

Thanks for all the help so far. At last I have one channel working!

OK! So I finally got my channels working... Thanks to everyone who has helped so far..  Both of them sort of work.. But I have a boat-load of HUMMM that I am sure is from improper grounding.. I am a bit confused about how to ground this circuit properly. I checked the "grounding the SSL9K" thread in the meta, but I am still not sure. I made a diagram of how it is done right now, please correct me if it's wrong.. The diagram is of the main, balancing and PSU boards, with only ground wires marked.

NOTE:
1. Points on main and balance boards marked XLR IN and XLR OUT are attached to the shield of a mic cable connecting the XLR to the appropriate board, but it's not attached to Pin 1 of the XLRs.

2. XLR IN pin 1 connected to star ground.

3. I tried XLR OUT pin 1 to ground and floating, didn't seem to make a difference. I have disconnected audio ground from earth ground but nothing..

4. Hum seemed a bit worse with phantom (condenser mic).

5. My XLRs and pots are hanging at the moment as I am waiting on front/back plates for my case.


Thanks again!

This is interesting.

Will anyone knowledgeable help this fellow member?

I Connected all my shields from my inputs to the input GND on the boards.
My Balance boards have the GND from the main board connecting to the audio GND of the balance board.
Then I connected all the shields for the output to my DB-25 output connector. 
The only "star ground" I have in mine is that all the 0V are connected to the 0V output of my JLM power supply. 
My earth GND is via a bolt on the case next to the IEC outlet.

This set up has not given me any problems with hum or buzz.

I don't think your XLR's or your pots not being mounted to the case will make that much difference.

My 2cents.

Casey
(Signalflow)

Thanks for the bump Whoops, and Casey for the explanation. Glad to hear your SSL is working well. Did you ever get around to the firewire thing?

signalflow said:

I Connected all my shields from my inputs to the input GND on the boards.

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I had mine like this initially, but somewhere in my "extensive troubleshooting" I changed them. Will put them back like this to see if it helps.

Then I connected all the shields for the output to my DB-25 output connector. 

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I have these floating for now, will try changing the inputs first and see if I can leave these like this.

The only "star ground" I have in mine is that all the 0V are connected to the 0V output of my JLM power supply. 

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Here is another question.. I am using Keith's PSU(the one that comes with the pre boards), and it has a 0V for each output (they are all connections to the PSU ground plane)..I wonder if I should cut two of the wires and only leave one connection between PSU and star ground??
PSU info:  http://www.beatbazar.com/guests/ssltech/kps-1/index.htm

thanks again!

Have you tried rotating your toroid yet?

mushy said:

Have you tried rotating your toroid yet?

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Numerous times...

I tried wiring the inputs as above, helped a bit, but not perfect. I now noticed one of my phantom resistors was broken...

I'm wondering if the one wire from PSU to star ground would be a better idea. I think I'll try that later. The holidays are getting in the way of my DIY!

OK.. hopefully the last update to this thread... I wired input XLR and output XLR Pin 1s to their spot on the PCB (instead of direct to ground) and at first "glance" everything is OK. No extensive testing but so far sounds good, nice gain, no humm, (had hiss on one channel because I used 2x BC550C instead of a MAT-02 that went bad. I put in an LM394 and it works perfectly. Next step is clean-up and front plate etc..

Thanks to everyone who helped so far.

Glad it's all good.

Would love to see some pics....

gltech said:

Look at this schematic (rotate it so the text is oriented properly):
http://www.beatbazar.com/guests/ssltech/9k/9k-schem.pdf

The pots are oriented so that the wipers move up as the pots are rotated clockwise.

Here's another way to look at it:

Click to expand...

I don't think I remember seeing resistors on the original schematic, but apparently I need a 27 and a 39? Am I reading that right?