if you are building an SSL clone with THAT2180 series...

http://www.thatcorp.com/datashts/dn137.pdf

After reading the above THAT design note, it appears that 2180 series pre-trimmed VCAs should have resistors eliminated from circuits that were made for 2150 series with trimpots.

The SSL clone pcbs were made for 2150 series with trimpots, so
does anyone know which specific resistors (value and location on pcb) should be eliminated or bypassed?

thanks,

Chris

I think you are referring to pin 4 of the 2180.
NC
No Connection.

do a search here and you may find some other references to this.

I'm also using the 2180 vcas... I just looked at the layout and for me it seems, that you can leave out the red marked parts...



can somebody confirm this please..??

mat

This looks good.

I think I just leave the trim and the 68 out ... :roll:
Now trhat I think about it ... I may have one that still has the 68s in there ... oops :shock:

I'll have a closer look when I get home tonight ... Jakob could be here soon.

so the 47R res on the sidechain 2180 can go to then ye?

good point :shock:

I've never done that ??
... a distorted side chain might be cool ?
It would follow that you can leave this resistor out as well. I don't think you are going to notice much difference but give it a go, you can always put it back.

I must try this.

I'm using the 2180
So then I leave pin 4 open.

What is pin 4 for then ? I thought I would have to short it to ground without the 68 ohm resistor. Thus giving the VCA the ground as a reference point?

Please explain.

-Chuck

I think the easiest thing to do is to just clip pin 4 off of the vca itself...

So... what kind of distortion would I get if, hypothetically speaking, I forgot to clip the pin, soldered the resistors in, and left out the trimpot?

I've built SSls with the 2181 and the 2180 and put everything in except the trimpot. We havn't noticed anything in using the compressors on mixes, drum busses, guitars, etc.

Ian

Okay, cool. I thought mine sounded fine when it was all put together, but my ears aren't the most experienced when it comes to subtlety.

[quote author="Ian MacGregor"]I've built SSls with the 2181 and the 2180 and put everything in except the trimpot. We havn't noticed anything in using the compressors on mixes, drum busses, guitars, etc.

Ian[/quote]

Me too, with the same experience. I'll listen again and double check, but it sounded fine to me and I just left out the trimpot.

:thumb:

I clipped pin 4 off all of three 2180's and then put A/B'd with original 2180's with all the resistors in place....After listening back and forth a few times, I decided to stick with the original 2180's and the all resistors....seemed to sound better to me...

so you landed pin 4?

Pin4 : to cut or not to cut ; this is the question. :roll:

Start out with no-cut - you can always cut if you find the unit bad-sounding

(which you won't, I promise)

Jakob E.

Ok Jakob, I'll try (in the new year :wink: )
thanks!
Merry Xmas and Happy New DIY Year !!

I'm getting in all the parts for my first GSSL (this will be my first DIY project). I've been studying everything in the meantime, and I read that it's better to land any extra pins and send them to ground rather than clip them in case of any minute static charges in the air.

If I wanted to do this in the case of pin 4 on the 2180LA's, would I just eliminate the trim pot and extra resistors, and replace them with jumper wires?

[quote author="zboy2854"]I read that it's better to land any extra pins and send them to ground rather than clip them in case of any minute static charges in the air.[/quote]
You have most likely been reading about logic chips, which should not have any inputs left floating.

You should not ground an NC pin, unless the datasheet tells you to do so. Sometimes the "NC" pins aren't actually NC, but used for testing etc.

Best regards,

Mikkel C. Simonsen

I have 2181LC chips. I checked their data sheets (after I bought them, duh) and found the maximumTHD rating so much higher than other types:
2181LC=0.02%
2181LA=0.005%
Are they worthless in this design? :sad: