GSSL HELP THREAD!!!

[quadwould]

Building yet another GSSL...

Odd thing on this one.

Just fired up for first time. Looks to be runing smoothly.

I am giving it a Balanced Sine wave signal at -18dBfs (0VU) into each channel.

in bypass i get -18dBfs (0VU) on the Left output, and -24dBfs(-6VU) on the right.

on checking the pins of the OP ICs (5532s) I see a beautiful sine wave on both O/P pins of the Left channel 5532, and on only 1 pin of the right channel.

So from that, i have gathered, this is the reason for the 6dB lower output from the right channel.

I have tried with my scope (tek 465b) find the sinewave and whre it has disappeared, but i have an issue.

the 465b seems to not be strong enought to see the audio signal.

I can see the sine wave up until the 27k resistor at the I/P of the VCA. and the next time i can see it is after the O/P of the 5532s in the output section.

Does this mean my 465b need calibration, or is it just not able to see signals as small as these?



As a result i will be taking the whole right cnannel o/p area out, testing each component, and re installing them all. hopefully that will work.


Oh and yes I have tried changing ICs. the ref voltage is spot on.

 

[pepe]

Should I bridge the 0V link or avoid it, any suggestions?
I can not get why this ground loop should be introduced into the design but maybe there is an explanation.

 

[blackwater]

resolved

 

[digiteck]

Hi, i've bought a ssl clone a few months ago and now i have a problem with it.... (with VCA DBX2001)

The only thing i know:
- I realize my unit have a problem when i heared an anormal breath (Hi Frequences) so i bring it to a tech...
- the guy who servicing my unit find and repair the breath problem (it was 5532 & 5534 circuits) but find an anormal voltage at the output (DC voltage at the analog output : 350mV) and some distortion and think that's the VCA have suffered...(causes by a hot temperature, because one day, i think the unit temperature were about 50° Celcius because it was too closer of other unit in my rack...)

The compressor seems to work but with the problems i've listed...

If the VCA are really dead, can i replace them by 2 DBX2150 (which i have) because it's very difficult to find the DBX2001... Is it easy to do?

Thanks

Lionel

p.s. : excuse my bad english....

 

[gyraf]

Blackwater,

I understand your frustration, but please start a new thread for your complaint (preferably under "The Brewery") - as this is ment to be a help- and error-fixing thread..

Jakob E.

 

[kryckmeister]

Sounding allright bypassed, can't find any short circuits anywhere, all resistors correct. Why is my SSL distorting?

 

[Harpo]

[quote author="kryckmeister"]Sounding allright bypassed, can't find any short circuits anywhere, all resistors correct. Why is my SSL distorting?[/quote]
did you solder in the bridge right next to the meter connectors on control-pcb ?

 

[gyraf]

:razz: yup, that's the classic error

 

[kryckmeister]

[quote author="Harpo"][quote author="kryckmeister"]Sounding allright bypassed, can't find any short circuits anywhere, all resistors correct. Why is my SSL distorting?[/quote]
did you solder in the bridge right next to the meter connectors on control-pcb ?[/quote]
Yup, it's all there...

 

[Harpo]

[quote author="kryckmeister"]Yup, it's all there...[/quote]
If troublefree in bypass, the fault comes from the sidechain part or it's powersupply. Assuming, you already checked the diodes orientation, you may have a bad TL072, TL074 or VCA chip or bad 78L12/79L12 regulator. First check for stable +/- 12V voltages on TL072+TL074.
If you have a lamp for the meter connected, from where did you power it ?

 

[crisotop]

I'm currently trying to source all the parts for the gssl - I'm using Greg's BOM and have some troubles finding the two "tantulum capacitors". I'm located in Austria and want to order from Farnell/RS Components and both vendors don't have the 0.47u/6.8u in 50V, the highest available voltage is 35V.

Would that be enough, or should I use a capacitor of a different construction type?

Many thanks
christoph

 

[Harpo]

[quote author="crisotop"]... 0.47u/6.8u in 50V, the highest available voltage is 35V.

Would that be enough, or should I use a capacitor of a different construction type?

Many thanks
christoph[/quote]
Enough. Look at the schemo (always a good idea). These tantalums in the sidechain are fed from the TL074. These can provide no more than their own supply voltage (+/- 12V). Add a little headroom for better sleep.

 

[Frugaljr]

Hello all. My GSSL is finally complete. I left all of the chips out and checked for voltages, then installed, cringed, and fired it up! No sparks, no hot components.

It passes good audio for about 2-3 seconds, then hum suddenly takes over starting left, then to the right. I shut it down. Found one .1uf cap missing between transistors, installed, tried again, same result. With the compression switch on, it does compress, but does the same thing and goes to full hum, no audio.

Any ideas? Could be something that charges up. I checked all caps for orientation, they are O.K.

 

[gyraf]

Check all supply voltages under both working- and fault conditions...

specially the +12V

Jakob E.

 

[crisotop]

thanks harpo!

I wasn't sure about it, because some caps go up to 100V...

cheers
christoph

 

[crisotop]

One last question - I see lots of finished units here with an "off-board" transformer and not the pcb mount like suggested on gustav's pcbs. Is there an advantage of using regular transformers, or is it "just" cheaper?

Many Thanks
Christoph

 

[Harpo]

[quote author="crisotop"]One last question - I see lots of finished units here with an "off-board" transformer and not the pcb mount like suggested on gustav's pcbs. Is there an advantage of using regular transformers, or is it "just" cheaper?

Many Thanks
Christoph[/quote]
it depends and is sometimes a matter of needs, taste, availiable space and bucks.
The on-board transformer is limited by size and power rating to fit pin spacing. It will work fine with this pcb only.
Those "regular transformers" :?: are most often toroids, providing higher VA rating at lesser radiation for additional sidechain filtering, LED-bargraphs, cigarret-lighters or other features/gimmicks, giving you the advantage to place it further away from hum sensitive parts. Unfortunatly these toroids are more expensive, knowing it's comparing apples with oranges.

 

[crisotop]

I see - considering I'm planning to add a sidechain filter board, it might be a good idea, to use a torroid with a higher VA rating - would 25VA be enough?

many thanks
christoph

 

[Harpo]

[quote author="crisotop"]I see - considering I'm planning to add a sidechain filter board, it might be a good idea, to use a torroid with a higher VA rating - would 25VA be enough?

many thanks
christoph[/quote]
a 25VA will leave you enough safety margin for sidechain filtering or additional relais for hardwire bypass and LED's for status indication. Measure the inner higth of your case to select the required transformer and make shure, that the toroids fixing bolt under no circumstances touches the top lid of your case.

 

[crisotop]

that the toroids fixing bolt under no circumstances touches the top lid of your case.

That's one thing I remember from building a gainclone amp

How would you mount the trafo and the pcb's? I have one of purusha's cases, and the wall thickness of the bottom plate is not that massive, for example to use countersunk screws.

Thanks Harpo!