GSSL HELP THREAD!!!

[bubba_b]

My first post! This is a great place and all you guys seem really helpful to each other. Nice to see and thanks in advance for any help you can give me.
Anyway, I'm building my first SSL clone, also my first DIY. I've found pretty much all the parts I need except I'm having a hard time finding a transformer. I'm getting most everything from Mouser, but the transformer I'm lost on (there's just so many different ones I don't know which one's right). If anyone has part no.'s and places to go, I'd be very grateful. Also, I need the PCB's. I saw the link to audio kitchen somewhere and emailed them, but haven't heard back. Any other options for pre-made PCB's?

I'm sure once I get going on this, I'll be back with more questions and good news of success. :grin:

 

[gyraf]

Bubba,

Welcome to "The Lab".

For PCB's see "The Black Market", our trading section.

Your transformer question is better answered by someone in your local neighbourhood.

Jakob E.

 

[BladeSG]

Hi Guys,

I've finished soldering the PCB's for this project and after initially only giving the board 15VAC from the toroid, worked out it needs 30VAC (thanks to Jakob). So I rewire the toroid and power up again.

The problem I'm having is distortion. The controls seem to be working, but both channels are distorted. I measured at the + and - jumpers:

+14.83V
- 4.30 V

This led me to beleive the 7915 was at fault until I disconnected the Control PCB and measured these jumpers again. This time with the Control PCB disconnected I get:

+14.83V
- 15.10V

I've checked the Control PCB for shorts and incorrect parts and all looks good. Also rechecked the wires connecting the Control PCB.

Any ideas?

Thanks in advance.

 

[radiance]

Thanks BuzAllen.
This is what I came accross about pseudo balancing:

"...Quite commonly seen is the plain ?pseudo balanced? phase/antiphase output, where the equipment?s internal unbalanced signal is simply fed to signal + out (XLR pin 2) by means of an opamp buffer and is fed to signal ? out (XLR pin 3) simply by means of a polarity inverting opamp. This doesn?t implement a true balanced output and rather can be looked upon as a pair of unbalanced outputs, one being polarity inverted. ... "

I thougth that the SSL clone output stage was pseudo balanced but I might be wrong here.

 

[gyraf]

BladeSG,

I think you can be pretty sure there is an error somewhere on the control pcb. Check for anything shorting to or connecting to the -12V rail.

Jakob E.

 

[BladeSG]

I'm sorry but I don't know which are the 12V rails.

Thanks again Jakob.

 

[gyraf]

Look at the schematic. Look at the layout. Look at the PCB. There is a -12V (and a +12V) circuit that starts with the 79L12 regulator, and (amongst others) goes to the control pcb.

Jakob E.

 

[BladeSG]

Jakob, there doesn't appear to be anything shorting or touching.

Thanks,

Steve.

 

[mich]

something is shorting.......but you'll find it.

i had one pin of the molex conector (that conects the two boards-at the main board) shorting another.......actually it was the pcb istelf-a trace touching when it shouldent.....animo.....

 

[mich]

p.s - u also have to check with a cuntinuity meter - cause many times you dont see the problem, but its there..

most of the modern DMM have this meter in diode checking setting.

hope it helps

 

[Greg]

I've noticed that alot of problems with SSLs result from shorting (ie solder blobs) and/or cold joints... I'd recommend that evertime to solder a component in, you test continuity with points its connecting to, as well as check to make sure it's not shorting nearby points. It might take you an extra hour or two to build, but it'll save you headaches in the long run.

I've done this with everything I've built and everything has worked on two GSSLs and a G1176...

 

[tmbg]

[quote author="bubba_b"]My first post! This is a great place and all you guys seem really helpful to each other. Nice to see and thanks in advance for any help you can give me.
Anyway, I'm building my first SSL clone, also my first DIY. I've found pretty much all the parts I need except I'm having a hard time finding a transformer. I'm getting most everything from Mouser, but the transformer I'm lost on (there's just so many different ones I don't know which one's right). If anyone has part no.'s and places to go, I'd be very grateful. Also, I need the PCB's. I saw the link to audio kitchen somewhere and emailed them, but haven't heard back. Any other options for pre-made PCB's?

I'm sure once I get going on this, I'll be back with more questions and good news of success. :grin:[/quote]

Take a look at Digikey part number TE62053-ND . That's a 15VA 15/0/15 toroidal power transformer that should do nicely

 

[BuzAllen]

Thanks BuzAllen.
This is what I came accross about pseudo balancing:

"...Quite commonly seen is the plain ?pseudo balanced? phase/antiphase output, where the equipment?s internal unbalanced signal is simply fed to signal + out (XLR pin 2) by means of an opamp buffer and is fed to signal ? out (XLR pin 3) simply by means of a polarity inverting opamp. This doesn?t implement a true balanced output and rather can be looked upon as a pair of unbalanced outputs, one being polarity inverted. ... "

I thougth that the SSL clone output stage was pseudo balanced but I might be wrong here.

That being the case, you were right. That being the definition for psuedo balancing then yes, the ouput in the gssl schematic would be psuedo balanced. Sorry bout the confusion I guess I wasn't quite as sure as a I thought about what was meant by psuedo.

By this then I am guessing that a true balanced by these definitions would need to be floating (i.e like a xformer. ) All these different definitions for balanced can be confusing as I have seen many different layouts use then labled with the same name.

I just did a search on the web for 'pseudo balanced' and found another definition (which doesn't surprise me at all):

"There are many products on the market that add XLR connectors to an internal single-ended circuit. Such designs, while sporting XLR connectors, don't process the signal in balanced form. It is fair to call such units 'pseudo-balanced' "

So as usual I am still at a loss for real definitions on this. In school I learned that the term 'balanced' refered to the balanced or equal output impedance on both the cold and hot leg, regardless of whether both legs were driven. 'Differential' was used to define whether the cold leg was driven oposite polarity and 'floating' indicated floating signal lines (i.e. like a transformer)

If interested here are a couple of links to sights that go over this stuff:

A really good paper by Bill Whitlock of Jensen Xformers:
http://www.jensen-transformers.com/an/an003.pdf

Also, try this for questions on interconnecting bal/unbal gear:
http://www.dself.dsl.pipex.com/ampins/balanced/balanced.htm

Brian


Brian

 

[bubba_b]

Thanks gyraf. I'll check it out.

tmbg: Found it, thanks. One thing I forgot to specify, though and maybe you already assumed this, but I can't tell from the description. Is this trafo for 220V or 110V? Im in the US. I keep forgetting that's an issue.

On a side question, how feasible is it to make this clone a dual-mono compressor, besides just adding a second set of controls? Has anyone tried this, or is it too much trouble to bother with?

 

[gyraf]

[quote author="bubba_b"]On a side question, how feasible is it to make this clone a dual-mono compressor, besides just adding a second set of controls? Has anyone tried this, or is it too much trouble to bother with?[/quote]

We've discussed this several times. Use search to find these. But in short, no, a mono version is not feasible.

Jakob E.

 

[bubba_b]

Ok, was just curious. Thanks for the quick and simple answers.

 

[tmbg]

[quote author="bubba_b"]
tmbg: Found it, thanks. One thing I forgot to specify, though and maybe you already assumed this, but I can't tell from the description. Is this trafo for 220V or 110V? Im in the US. I keep forgetting that's an issue.
[/quote]

It's BOTH!

Wire the primaries in parallel, and it's 110, wire them in series and it's 220. 220 draws half the current at twice the voltage, which is exactly the same amount of power. Isn't math fun?

 

[bubba_b]

Excellent! Thank you.

 

[bubba_b]

Ok, so I've ordered up all my parts except for the knobs, case and meter. I've heard it said not to use a VU meter, but a mA meter. Knowing that the meter isn't the most crucial element to this unit, could I use an LED meter instead? I'd prefer to use the needle style, just wondering if anyone's used an LED on this before.

Sifam has an audio meter I really like, but it's an audio meter (the AL20). I'm assuming from their description it's not right for the GSSL? If not, too bad. It looks tight!

 

[BladeSG]

Thanks Mich & Greg.

Checked and rechecked visually and still cannot find anything that shorts. However I did find that the + wire and F wire from the Main PCB to the Control PCB are shorted. I would imagine that this is OK as both these tracks on the Control PCB end up at or going through the + and middle connection to the 50K Threshold Pot, so the short is actually the Pot itself?

Steve.