GSSL HELP THREAD!!!

[mac]

Hi everyone,
I am currently putting together a hybrid 2RU box with a turbo GSSL and 2 9k preamps. My power supply is an 18-0-18 torroid with the 9k psu and mnats psu for the 15v feeds (I am going to retain the 78l12 adn 79L12 pair on board).

Question: has anyone done tests to see if retaining the two 1000uf caps on the board is beneficial when using an external PS board? I was thinking that this together with the 10r resistor pair would give me and additional CR filter stage on board for the 12v rails (pink highlight on the attached sketch).

Or perhaps the small gains are not worth the expense of the two big caps, for additional filtering on the 12v rails?

Should I pop a pair of resistors in for the links (in orange) so that I am achieving an additional CR filter for the 15v rails too?

Mac

 

[Soeren_DK]

Is it possible to drive 3 LEDs in serial from the LED output on the control board or should I build a little separate PSU for the meter light?

Cheers
Søren

 

[Harpo]

Is it possible to drive 3 LEDs in serial from the LED output on the control board or should I build a little separate PSU for the meter light?

Cheers
Søren

It is possible, but you have to decrease the current limiting resistor for the additional 2 forward voltage drops in the LED series string for the same current. [(Vsupply - 3*Vf LED) / I LED]. For 12V supply, maybe 3.3V for a white LED and brightness set for 10mA this would be 210R. Just look up the datasheet for your type and colour of LED and keep in mind that forward voltage is a typical value, your LEDs might be at the min.or max.end within parts range.

 

[Soeren_DK]

It is possible, but you have to decrease the current limiting resistor for the additional 2 forward voltage drops in the LED series string for the same current. [(Vsupply - 3*Vf LED) / I LED]. For 12V supply, maybe 3.3V for a white LED and brightness set for 10mA this would be 210R. Just look up the datasheet for your type and colour of LED and keep in mind that forward voltage is a typical value, your LEDs might be at the min.or max.end within parts range.

Thanks for the reply. The limiting resistor, is it this 1k resistor?

Cheers
Søren

 

[Harpo]

The limiting resistor, is it this 1k resistor?

Yes. (1K probaby for a red or green LED)

 

[Soeren_DK]

Perfect... Thanks. 
After building the unit 2 years ago its time to get some meter light in the unit.
Last question, can it inflict some noise or hum? The unit is quiet as a sleeping alcoholic

Cheers
Søren

 

[Harpo]

The unit is quiet as a sleeping alcoholic

This mod won't snore  ;D

 

[MikeClev]

People have warned earlier in this thread that the 12v supply is being run close to its limits as it is, and advise against drawing any additional current from it (stable 12v supply is important for the sidechain). They suggest hooking extra LEDs up to the secondaries of the PSU transformer.

Hope that helps...

 

[Harpo]

People have warned earlier in this thread that the 12v supply is being run close to its limits as it is, and advise against drawing any additional current from it (stable 12v supply is important for the sidechain). They suggest hooking extra LEDs up to the secondaries of the PSU transformer.

Hope that helps...

Correct for LEDs in parallel config, switched to show different functions, that might/would exceed the 78L12 limits.
The circuit described by Søren is 3 LEDs in series for 1 function (on/off), drawing the same current as the single LED, and depending on colour of LED for their differing forward voltage, 3 blue or white LEDs in series is the max amount for a 12V feed.

 

[Alessio]

Hi everybody, I've finished my GSSL and I'm ready for the next one. I have two quick questions:
1- I did some mods to my gssl and now I would like to increase the make-up in order to have more gain.
Is it possible without modify the entire circuit?

2- Does all the SIFAM AL 19 meters fit in 1U rack? I was thinking to use the AL19B for my next unit but then I saw the AL19W or AL19WF that are illuminated and I like them more. Do you think I can use those?
Or is there a way to illuminate the AL19B or the PPM14? (that aesthetically are nicer)



Thank you very much!
Alessio

 

[mac]

Hi everyone,
I am currently putting together a hybrid 2RU box with a turbo GSSL and 2 9k preamps. My power supply is an 18-0-18 torroid with the 9k psu and mnats psu for the 15v feeds (I am going to retain the 78l12 adn 79L12 pair on board).

Question: has anyone done tests to see if retaining the two 1000uf caps on the board is beneficial when using an external PS board? I was thinking that this together with the 10r resistor pair would give me and additional CR filter stage on board for the 12v rails (pink highlight on the attached sketch).

Or perhaps the small gains are not worth the expense of the two big caps, for additional filtering on the 12v rails?

Should I pop a pair of resistors in for the links (in orange) so that I am achieving an additional CR filter for the 15v rails too?

Mac

;D

 

[Harpo]

My power supply is an 18-0-18 torroid with the 9k psu and mnats psu for the 15v feeds (I am going to retain the 78l12 adn 79L12 pair on board).

The 9k psu isn't relevant then for this circuit.

Question: has anyone done tests to see if retaining the two 1000uf caps on the board is beneficial when using an external PS board? I was thinking that this together with the 10r resistor pair would give me and additional CR filter stage on board for the 12v rails (pink highlight on the attached sketch).

Or perhaps the small gains are not worth the expense of the two big caps, for additional filtering on the 12v rails?

I doubt this is benefical. The 1000uF caps with MNats psu in front seem on the high side, but should work (with a 9k psu instead maybe only once because of missing diodes across the regulators). I'd probably try 470uF max, if any, to not exceed the cap value in front of the regulators. YMMV. The 10Rs in front of the 12V regulators might be dropping too much with your already regulated 15V DC feed. From 7xL12 datasheet you want at least 14.5V in front of these regulators.

Should I pop a pair of resistors in for the links (in orange) so that I am achieving an additional CR filter for the 15v rails too?

This isn't raw DC from rectifier/cap where an additional CR stage might be an improvement, but already smooth DC. Additional resistors in your orange links would rise regulators output impedance and act as current limiters/fuses.
From your attached sketch, a 3rd blue link between MNats psu 0V and your GSSL 0V will be of much more use.

 

[mitsos]

damn, I was all excited about having a nice new GSSL to play with... all was fine, then I went to install a switchable turbo, and poof, no more sound... All my voltages are OK on both boards and I connected according to the manual at Expat audio.... but... hmm. (well I do get some reaaallly low output, but I have to crank the gain on the line amp of the interface to hear anything).

No controls work, Ptown meter shows nothing (but lights up pretty ),

I removed the audio VCAs and jumpered pins 1+8 but still get no sound...

Then I disconnected the turbo (but left the wiring in place) but still get nothing...

I went over all the resistors on the turbo board, they are all the right values, I checked them with a meter before stuffing and checked them in circuit now..

I scoped the input with a 1.2V signal, and get 450mV at the 47K resistors. I don't know where to go from here.... if someone has some pointers....

thanks in advance!

 

[mac]

Thanks for your comments Harpo.

Yes I omitted the 0v on my drawings oops.

The 9k psu isn't relevant then for this circuit.

I dont think you understand what I am proposing however. The mnats psu is fully adjustable and will deliver +15v 0v and -15v.

The 9k psu is only for the 9k's, but I described my setup because of the 18-0-18 torriod I was using.

I shall bolt it all together and see what happens...

Mac.

 

[Voodoosound]

Excuse me but i have searched everywhere and can not find an answer to this question.

I am trying to order the Lorlin switches for my GSSL with Super Sidechain.

Do they need to be Shorting (MBB) or  Non-Shorting (BBM)  :-[\

Thanks !

 

[Alessio]

Anyone? please...
I'm ready to order the parts.

Thank you,
Alessio

 

[mitsos]

Not sure about the makeup gain, but as far as meters, take a look at the meter at hairballaudio.com. The black one is made for this circuit and should fit a 1U.

 

[Alessio]

Thanks Mitsos,
but these meters seem too cheap to me. I've used the Beheringer one for my first GSSL and it's not accurate, it's not linear, so I was thinking about SIFAM quality...
I think the AL19wf should fit in 1U rack... but I'm not 100% sure

 

[mac]

Alessio,
you will have to check the datasheets from canford. They are all a bit different, (and may depend upon your 1ru case also). For instance the retros are too big at about 55mm.

The back of my PPM14 was massive and only just fits with about 2mm to spare on the back of the meter (because of the design of my 1RU case).

datasheets here http://www.nrgrecording.de/SIFAM_PPMsatcanford.co.uk.pdf

Mac

 

[Voodoosound]

Anyone please ?

Excuse me but i have searched everywhere and can not find an answer to this question.

I am trying to order the Lorlin switches for my GSSL with Super Sidechain.

Do they need to be Shorting (MBB) or  Non-Shorting (BBM)  :-[\

Thanks !