GSSL add-on help thread

[Script]

Signals on the two 47k out read the same L R ? If so, could swap SC VCAs to confirm they are ok, assuming they are the same type (eg both 2180) -- and careful with IC orientation of the VCAs here.

I standard mode, the compressor works and each side compresses evenly, but the meter is showing much less compression than I would expect.

Could be one of the signals doesn't reach its destination at all -- the one flipped between "47k sum" and "turbo".

I'd start by looking at the Standard / Turbo mode switch and by checking connectivity (DMM beeper) of wiring coming from the 47k to main board and turbo board. Does it connect as needed ?

 

[craigmorris74]

Signals on the two 47k out read the same L R ? If so, could swap SC VCAs to confirm they are ok, assuming they are the same type (eg both 2180) -- and careful with IC orientation of the VCAs here.



Could be one of the signals doesn't reach its destination at all -- the one flipped between "47k sum" and "turbo".

I'd start by looking at the Standard / Turbo mode switch and by checking connectivity (DMM beeper) of wiring coming from the 47k to main board and turbo board. Does it connect as needed ?

I can't believe this, but I'm pretty sure I just had a component in the wrong place, and one that I thought I was being careful putting in the right place. I had the 47ohm resistor feeding pin 4 on the 2180B on the main board. Switched it to the spot connected to pin 3, and now both sides compress identically. I feel really dumb.

 

[Script]

Good

 

[t_carvalho]

Hello everyone.
I have a GSSL bus comp with a turbo mod that bought from a friend many years ago and works great. Now i would like to add to it the sidechain mod as well and change the faceplate, add a new meter and push buttons.

First question i would like to ask is what is the difference i using 1 or 2 sidechain boards since i´ve seen designs with 1 or 2.
The comp also has a commuter board to light up the push button when they are engaged, dont know how ill tackle that one, hopefully someone can help.
I´ll leave a few pics.

Cheers

 

[craigmorris74]

Hello everyone.
I have a GSSL bus comp with a turbo mod that bought from a friend many years ago and works great. Now i would like to add to it the sidechain mod as well and change the faceplate, add a new meter and push buttons.

First question i would like to ask is what is the difference i using 1 or 2 sidechain boards since i´ve seen designs with 1 or 2.
The comp also has a commuter board to light up the push button when they are engaged, dont know how ill tackle that one, hopefully someone can help.
I´ll leave a few pics.

Cheers

Since it has the Turbo mod, it has two sidechains. You need a sidechain filter board for each channel.

 

[t_carvalho]

Since it has the Turbo mod, it has two sidechains. You need a sidechain filter board for each channel.

Yes, i did a bit more research on the turbo mod and in fact it needs 2 sidechain boards, thanks for your reply. Is there a BOM from mouser or farnell that i can use? Did a search on the forum but couldnt find it.

Cheers

 

[tomyjaunin]

Hello everyone
desesperate not to get a cavendish from expat, i decide to draw my own.
but i miss informations about the pinout of the 2503, anyone could help me?
thanks!

 

[Bernardo]

Please someone who can help me. I'm installing the goldcan dbx202. Everything works fine, but I can't find the input impedances of the dbx202 vca and the 5532 outputs. I get a lot of saturation. I have read that the 27k input of the vca is changed. for 15 plus a trim of 50k the 15k of the 5532 are changed to 27. I have followed these instructions and it gives me a lot of output gain. some help please.

 

[tomyjaunin]

You can find a schematic on gyraf audio
https://www.gyraf.dk/schematics/Dbx202.pdf

 

[Bernardo]

thank you tommy for your help, very useful, According to the schematic, I have to change the 27k resistor for a 50k input resistor, in addition to adding 1uf, and change the 15k of the 5532 for another 50k. would this be correct?
Thanks a lot

 

[Script]

This is a reply to a post in the vanilla gssl help thread.

No external, it's an EQ shelf in the sidechain while the sidechain is functioning as normal.

So you would have the option to select your sidechain Freq ie 120hz the sidechain would act as normal. The shelf EQ would be ontop of this.

It doesn't seem to have been done.

I've had the lend of the Elysia alpha. If you look at the sidechain there is an option the EQ the sidechain. It sound great just for tightening things up without adding more compression.

From looking at the graph plots it just looks like a shelf +/- in the sidechain.

I don't think it's a shelving filter 'on top'. Elysia manual says. "possible to realize 'almost' shelving filter".

I still think it's a parallel configuration into a summing amp. One stem is plain signal at unity,, while second stem in parallel is a HPF, which is sweepable and has gain, and that can be changed to LPF by flipping at op amp from IN+ to IN-. (I might be wrong though)

Thus parts of the filtered second stem are added or subtracted in the summing amp. The detector does not care about polarity.

 

[petermontg]

Thanks Script. That would make more sense to what I am hearing it do.

I'll give it a go in parallel and report back with my findings in the new year.

Just so subtle at tidying up the top end that it's hard to ignore.

Best peter

 

[Script]

HPF plus gain might be a bit like 'tilt'. Switch to LPF and it's a bit like inverted 'tilt'. Add a bandpass filter with sweepable Q (a third pot on faceplate) and we would get 'smiley' and 'inverted smiley'. Filter 'factor 10' switches the caps in the filter, I'd think.

Or for simple testing, could just add an output buffer for Ext Send and an input buffer for Ext Ret and hook a graphic or parametric EQ into the side chain. But more rack space and also where's the fun in that ?

Yes, please report back. Very interested

 

[Davey78]

Hey guys, after using my plain gssl for some months now I lately had some time and decided to finally put the turbo in and modify some frontpanel things etc. Well adding the turbo didnt work as expected and I destroyed one 2181 (because of stupidity). Thank god it isnt as hard to get as last year, so ordered some new ones. However today I tried to trace the layout back to get some more understanding and troubleshooting and came up with the following questions: The turbo board is a copy of the sidechain section right? But what is the purpose of the tl074 pin 10 connection to the S/C C.V connector? I expected the 470R to connect there, but I see pin 8/9 of the tl074 going to that resistor instead. There is no matching connection on the gssl board on those pins, so what are we doing here? Could someone enlighten me?

 

[tomheavybeats]

I am just about to buy 2503 API style transformers for the Cavendish Mod but the standard ones from Capi Gear require minimum spend to ship to the UK.
I am wondering if anyone has used Sowter 2503 Trafo:

https://www.sowter.co.uk/acatalog/VINTAGE-RECORDING-AMPLIFIER-TRANSFORMERS-A-to-K.html
Much more convenient for me as in the UK and it says its replacement for 2503 but the footprint looks different so not sure if it will fit the PCB from Expat Audio? Can anyone confirm if they have used and fit fine please?

 

[Dominique Poinçot]

Hi,

I'm about to build my first GSSL, and have spent lots of time researching the subject.

I have one doubt though :

I'm using 2180 VCAs, so should I still put the 27K* resistors at the input ? Or should I just short the PCB there ?

Thanks,

Dom

 

[Ricardus]

I've noticed a lot of people building these who are populating some spots around the VCAs that my kit didn't call for. I built the kit that PCB Grinder used to sell. Mine works perfectly as is. Mine is using 2181s also. I know if you're using the big square vintage VCAs you do need to add more components.

Someone the other day just asked me about this in a PM, and the best I could do was send him a pic of mine.

So here it is.

 

[Ricardus]

Oh, there is one jumper I forgot to put in in that pic. You can see it to the right of the rightmost VCA by the two resistors. I put that in after I took the pic.

 

[Dominique Poinçot]

I've noticed a lot of people building these who are populating some spots around the VCAs that my kit didn't call for. I built the kit that PCB Grinder used to sell. Mine works perfectly as is. Mine is using 2181s also. I know if you're using the big square vintage VCAs you do need to add more components.

Someone the other day just asked me about this in a PM, and the best I could do was send him a pic of mine.

So here it is.

Thanks for the picture !

I thought the 2181 needed to be trimmed, but yours don't seem to have the trim circuit ?

You do have the 27K resistors on, so I think I'll leave them in.

For the jumper, I thought pin 4 on the 2180 wasn't connected. Where did you get this information ?

Thanks,

Dom

 

[Ricardus]

Thanks for the picture !

I thought the 2181 needed to be trimmed, but yours don't seem to have the trim circuit ?

Everything I have read about this circuit with the 2181 was that the 2181 was self trimming.

You do have the 27K resistors on, so I think I'll leave them in.

For the jumper, I thought pin 4 on the 2180 wasn't connected. Where did you get this information ?

I don't know. I don't have mine in front of me.