GSSL HELP THREAD!!!

[gyraf]

The 2K meter resistor is for current-output, i.e. for a current-reading meter. For voltage reading, the meter resistor won't do no difference.

Jakob E.

 

[Silvas]

Thanks Jakob !

i suspected that "no resistor" was the way to go so i haven´t soldered it, but i was unsure...

 

[Silvas]

A question regarding the trafo :


Very hard (read : impossible) to get the toroid here in Colombia.


Speaking of sound:

will be a negative thing to use a normal transformer (maybe a silicon or some fancy core) instead of a toroid one? will be noisier, dirtier or something? Will i need to use additional shielding?

Yeah, i know, i just can order a couple good toroids from digi-key, but my goal is to use locally available parts (except the VCA´s, will use 2181LB so i can trim them to sound "dirty" as i like compressors to be) so i can build many many compressors to round up my PT mixing rig !

i´m almost red-eyed from reading the whole thread i printed on 6pts font ! 200 pages !

excuse me for my crappy english

 

[ChrioN]

I have a question regarding the bypass switch:

Can I use a switch with only 2 solder leads? Its a simple on-off switch, pushed in its shorting the 2 solder leads, and pushed out its not conducting.

At gyraf.dk, I read that one can just solder in a jumper on the PCB to skip the bypass-function. The schematic shows that the switch is only switching 2 points.
But if you look at the PCB layout PDF at gyraf.dk, there are 3 more wires to solder to the switch, (COM, ON, OFF).

I am confused :?

 

[radiance]

[quote author="ChrioN"]I have a question regarding the bypass switch:

Can I use a switch with only 2 solder leads? Its a simple on-off switch, pushed in its shorting the 2 solder leads, and pushed out its not conducting.

At gyraf.dk, I read that one can just solder in a jumper on the PCB to skip the bypass-function. The schematic shows that the switch is only switching 2 points.
But if you look at the PCB layout PDF at gyraf.dk, there are 3 more wires to solder to the switch, (COM, ON, OFF).

I am confused :?[/quote]

Look at the schematic...When in bypass mode, the "com" is connected to the "off" point. When in compression mode th "com" is connected to the "on" point. So NO, you can't use a switch with two solder leads, you need at least a single pole dual trow switch (SPDT). If you also want to switch the gain make-up on and off, you need a dual pole dual trow switch (DPDT).
You can do this all with a 4pole 3pos Lorlin switch as sugested on Jakobs site....

 

[ChrioN]

Thanks for clearing this out.

I'm using pushbutton switches, and they ain't labeled as SPDT, DPDT etc.

Instead, it says
Contacts: 2 NO
Connection Method: ST

It looks like this:

ST is Single Throw right?

 

[radiance]

Find out with your multimeter (continuity) how your switch works. I can't tell from the pic and describtion.....

 

[living sounds]

Hi again,

my SSL clone is working now! Had to get over several obstacles, but now it sounds great. Thanks for not answering the really stupid questions, as I learned a bunch by figuring it out by myself. ;-)

I've got a S/N ratio now of around 100db - ist that a good value for the unit? Also, one channel is 2-3db quieter than the other.

Jakob, is there any point in switching the bypass caps (polyester right now) for higher quality (I've got a bag of 100n polystyrene caps lying around)? If so, which are the ones that make a difference?

Thanks for a great project - the thing really smokes all plugins!

Gregor

 

[bluezplaya]

I discovered that both my 12v regulators were bad so I replaced them. First the 78L12, which I had in my spare parts bin. I am now getting 12V+. However, I had to order the negative (79L12) from Mouser and it got in today. I removed the bad one and soldered the new one in to find that it too wasn't giving me -12V :shock: . There is about -24V going into the center leg but when I measured the other leg I was getting 0V. Can anyone shed some light?

Thanks,
Adam
:sam:

 

[balluda]

I also have trouble with my -12v rail,when I measure at the -12v point I´m getting -25,4v but when I measure later on in the rail I have -12v.What´s going on ? What should the reading for the middle leg of 79L12 be ? I get -25,4 V . Could someone measure it,please ?/Cheers

 

[Ricey]

[quote author="balluda"]I also have trouble with my -12v rail,when I measure at the -12v point I´m getting -25,4v but when I measure later on in the rail I have -12v.What´s going on ? What should the reading for the middle leg of 79L12 be ? I get -25,4 V . Could someone measure it,please ?/Cheers[/quote]

looking at a 79L12 reg from the flat side (pin 1 to the left) the pinout goes; left=GND , middle=Vin , right-Vout ...

so the reading at the middle pin is just the rectified, filtered output from the transformer... which should be around -19.6V for a 2x15V trafo or -23.8V for a 2x18V trafo (RMS of input voltage minus 2 diode drops of 0.7V (from the rectifier))...

So you're probably using an 18V transformer and getting worried about nothing... its the output on the right-hand pin (looking from the flat side) that matters... you should get a reading of -12V +/- 0.5V

 

[Ricey]

I've also got issues on my own SSL PSU regulation...

Around 50% of the time i switch my ssl on the 7915 latches on to around -0.7V. It's very odd... I've scoped the in and out on that regulator with the 2 channels on my scope... The input from the 1000u filtering caps is the same each time, but around 50% of the time, the 7915 just locks low...

When it is locked down @ -0.7V and you switch it off, as the voltage on the filter cap drops, around half way down (10V say) the regulator voltage jumps up to 10V DC and then falls down as the cap discharges...

I've tried wiggling everything around for a bad connection, but that's not it... Is this some kind of oscillation or just a bad 7915? I've heard they're pretty hard to break! And it's brand new from Farnell...

All the other regulators are all happy and nothing's getting warm whether the 7915 is going high or low...

When it does go high, everything seems to be working just fine...

Any ideas anyone?

P.S. is there anything i should pull out whilst sorting out the supply? is there anything that'll get mad if i feed it -0.7V down it's 15V rail whilst all other voltages are normal?

 

[balluda]

Thanks,I´m cool with that. I have 25,4 V feeding the circuit (78L12 and 79L12 ,traffo is ~20 V) and I´m using 25v capacitors, could that be the cause of the hum I´m having ?

 

[Ricey]

how much hum and when?

if you put the makeup to the max, you do get a tiny bit of 50Hz hum in with the noise floor. I've heard of people only getting rid of it buy adding an offboard PSU unit... but i'm sure there are workarounds for it...

 

[Ricey]

how have you got the units ground wired up?

 

[Harpo]

[quote author="Ricey"]I've also got issues on my own SSL PSU regulation...

Around 50% of the time i switch my ssl on the 7915 latches on to around -0.7V. It's very odd... I've scoped the in and out on that regulator with the 2 channels on my scope... The input from the 1000u filtering caps is the same each time, but around 50% of the time, the 7915 just locks low...

When it is locked down @ -0.7V and you switch it off, as the voltage on the filter cap drops, around half way down (10V say) the regulator voltage jumps up to 10V DC and then falls down as the cap discharges...

I've tried wiggling everything around for a bad connection, but that's not it... Is this some kind of oscillation or just a bad 7915? I've heard they're pretty hard to break! And it's brand new from Farnell...

All the other regulators are all happy and nothing's getting warm whether the 7915 is going high or low...

When it does go high, everything seems to be working just fine...

Any ideas anyone?

P.S. is there anything i should pull out whilst sorting out the supply? is there anything that'll get mad if i feed it -0.7V down it's 15V rail whilst all other voltages are normal?[/quote]

These regulators, especially 79xx, lock up if they see a wrong-polarity voltage at their output when they start working. This may be prevented by diodes antiparallel with the regulator. Don't know the current draw of the circuit, but brand dependant some need a higher min.load for whatever reason, so pulling additional 20mA by a 680R/1W may help in case the prementioned diodes (1N400x) didn't solve this issue already.

 

[Ricey]

sorry actually it's the 7815 that is having issues in my SSL... repeated typo's sorry...

 

[balluda]

[quote author="Ricey"]how have you got the units ground wired up?[/quote]

I have ground from starground to xlr-input to main PCB, I got a big hum on the outputs ,more in the left one. I havn´t conected the control PCB ,I hooked it off to see if the hum would disapear but it didn´t.

The traffo sais 18v but I´m getting 20,5V from it, I wonder why and I´m thinking the powering could be the problem....

 

[Ricey]

well my issue was all down to a bad 7815, which are pretty un-common i think. Went to the local store and replaced it with a fresh one (incidentally the same manufacturer) and all is well with my supply voltages now... :razz:

How accurate do we need our supply voltages to be?

I'm getting: 14.88 ; -15.26 ; 12.08 ; -12.18 which is all within specs of the regulators and it's all nice and smooth (tiny amount of HF ripple (around 0.1mV)). But do I need to be trying a few different regulators to try and get my supply voltages a bit closer to what they should be?

Balluda... was the 20.5V reading taken with your DMM set to AC just of either of the outer taps with the centre tap as reference ground? Is that without load?

It does sound like your supply is a bit high... you'd be better off with a 2x15V really... but all it means is your regulators will have to be dissipating a bit more power.... it's no particular reason for the unit to be noisy AFAIK... were you careful to make sure you used insulated washers or something like that to make sure your ground plane didn't get connected to the case when you bolted it all in? Have you checked and double checked for solder blobs/bad joints/missing vias/component orientation on the boards? (apparently it's common to forget one of the via wires on the control board).

 

[gyraf]

How accurate do we need our supply voltages to be?

+-10% is fine..

Jakob E.