Ricardus
WILL SOLDER FOR FOOD
Whoops said:
That's the regular gain pot isn't it?
The PDFs you sent that had example panels had 2 pots for both channels. What is the 2nd pot?
See attached pic. (can't upload pics!)
SSL 4K G-Series Mic Preamp
- Thread starter Whoops
- Start date
Help Support GroupDIY Audio Forum:
That's the regular gain pot isn't it?
The PDFs you sent that had example panels had 2 pots for both channels. What is the 2nd pot?
See attached pic. (can't upload pics!)
signalflow
Well-known member
Ricardus said:
There is a gain switch. The other acts as an output fader. If you're looking at the original schematic this is denoted by MOL 1-5. The schematic for the switch itself is on another page. Which can be found in tech docs subforum.
Ricardus said:
Thats the Output Pot.
The Gain is controlled by a stepped switch
Gain Switch Wiring
Ricardus
WILL SOLDER FOR FOOD
I saw the docs for the gain switch but it seems a little vague and unclear. For example there is nothing in the BOM for the switch or resistors as far as parts go. And there is a PDF called OFF BOARD CONNECTIONS or something and there is nothing about it in the PDF. And there are no contact points on the PCB PDF for those connections. Are you just soldering those points willy nilly to the board?
Has anyone here built this and can send me some photos?
Has anyone here built this and can send me some photos?
Ricardus said:
Sorry but I can't see anything vague or unclear on the doc I posted.
Ricardus
WILL SOLDER FOR FOOD
Whoops said:
Well, I am confused.
signalflow
Well-known member
Ricardus said:Well, I am confused.
Do you have the build guide that Dustbro made for the boards? There is a 4 pin connection point for the gain switch PCB right next to C5. It's named Conn1.
-Casey
Ricardus
WILL SOLDER FOR FOOD
signalflow said:
OK. I am officially an idiot. I looked at that PCB PDF a thousand times and didn't see that. Someone shoot me.
Ricardus said:
You need to relax...
And see all the docs calmly, because the info is there.
Ricardus said:
Yes there is. There's a BOM for all the parts in the Gain switch board.
Ricardus said:
Yes there are and there's clear diagrams in the documentation
Ricardus
WILL SOLDER FOR FOOD
OK, I see why I was confused here. I've been staring at every drawing except the build guide, which clears things up for me. I thought I was supposed to buy a solder lug grayhill switch and build the stepped switch by hand.
Plus I have two separate PDFs that are BOMs for the PSU, and the Preamp, and they're incomplete. The BOM in the build guide also includes the parts for the gain switch board, which the separate PDFs do not.
Phew.
Plus I have two separate PDFs that are BOMs for the PSU, and the Preamp, and they're incomplete. The BOM in the build guide also includes the parts for the gain switch board, which the separate PDFs do not.
Phew.
Hey i also think it's confusing since there are two resistors connected to nothing. In my opinion they have to do something. And I also found out that SSL is known for leaving gaps and not fully right documented pot wiring etc. often their wiring is wrong and don't work as supposed. Just to keep that in mind. I have a procedure with using different jumpers to connect it on my prototypes and later i will remove these jumpers. i ordered my prototype board for my 500 version of G channel already. so that will clear everything up in a week or so.
signalflow
Well-known member
Which resistors are referring to?
-Casey
-Casey
Ricardus
WILL SOLDER FOR FOOD
signalflow said:
I think he is referring to R16 and R17 (also 2 caps) which say "not fitted" on that gain switch drawing. I was wondering about that also, but then I noticed they're not even in the BOM and not even on the PCB. So just ignore that.
No it's R26 and R27. They are connected to a cable shield. But a connection to nothing else. So they are not connected. To keep that in mind. That's really unclear what they do. Copy and paste is not possible with ssl stuff.
signalflow
Well-known member
Kevin said:
Looking forward to what you find out. Even Dustbro's schematic shows different wiring for the Gain switch.
-Casey
Kevin said:
Yes you are right R26 and R27 are connected to Molex1 Pin1 and Pin5 that are just shields not connected on the Gain Switch end.
I checked the SSL schematics revision notes to see if there was any mention of it but the only thing I found was this:
Rev 0, issue B, 07 SEPT 87
"R26 and R27 were 180R now 649R"
Ok there were way more issues with this circuit. The original schematic and circuits tends to oscillate at 50khz. and is way more noisy then everything i had before. I fixed this oscillation issue with adding some caps in the Gain area. Also the working point of the dual Transistor needed some improvement That should compensate the oscillation problem. Also improved the input of the circuit a little against HF Problems. Now it should run smoothly. As always SSL is not just copy and Paste i will share my changes in my documentation later on in my 4KG91 Build Guide.
That should compensate the oscillation problem. Also improved the input of the circuit a little against HF Problems. Now it should run smoothly. As always SSL is not just copy and Paste i will share my changes in my documentation later on in my 4KG91 Build Guide.
signalflow
Well-known member
Kevin said:Ok there were way more issues with this circuit. The original schematic and circuits tends to oscillate at 50khz. and is way more noisy then everything i had before. I fixed this oscillation issue with adding some caps in the Gain area. Also the working point of the dual Transistor needed some improvement
Thanks for the update, looking forward to seeing what you've found.
Casey
Kevin said:
Thanks, it will be great to check that out
