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

[Rob Flinn]

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?

Its all relative. If you check they probably have a better spec than the original 2151 chips, which several people here have used & been more than happy with.

 

[Michael Krusch]

And, if you are unhappy with the distortion, you can still use the LC's for the side chain.

 

[aurt]

If I remember correctly, pin 4 on the 2180 is still a functional trim. if you are worried about the untrimmed performance of the LC version, you can quite likely trim it to a finer spec.

 

[gar381]

I Looking for a north american source for THAT2180LA's.
I found them at [email protected] $8.95 USD each plus shipping
and $7.44 each at www.thatcorp.com but you have to buy 25 of them.
Anyone have a cheaper Idea?

Thanks

Gary

 

[smilinfu]

http://www.blacklionaudio.com/black_lion.htm
I have not ordered from them so I can not vouch for them myself. I think some other folks have.

 

[thedug]

The 2180 is auto trim, but if you hook up the 1M resisters and the trim pots are you "overiding" the auto trim?

If so, can you just leave out the trimmer?
I think I read somewhere else awhile back about clipping the 1M resisters out.

Doug

 

[bzardeley]

People, I've seen a couple posts lumping the 2180 and the 2181 together.

Note that the 2180 IS pre-trimmed and the THATCORP data sheets leave Pin 4 disconnected in "typical applications."

The 2181 on the other hand is NOT pre-trimmed and still must be connected to a trimming network for minimum distortion (if that's what you're after!).

I can't speak for using 2181's in the audio chain (my GSSL has 2151's in there) but on the side chain there was a difference depending on whether the 47R resistor to ground was left connected to Pin 4 or not. One could argue that distortion in a detection circuit would have a noticeable effect on its abiltiy to track (and hence compress) audio. For the purpose of this circuit I may be splitting hairs but all the same it's worth investigating when you put your GSSL's together.

Cheers to all-

 

[thedug]

So..

On the side chain leave out the 47R.

On the audio channel leave out the 1M and/or trimmer.

BTW: As far as distortion on the side chain, wouldn't it have to be alot to cause problems? I mean.. the rnc uses a cheap A/D and has a digital sidechain so I can imagine that his thd ratings can be that good.

i.e. it prolly sounds nasty.. but it is a great sidechain and it cost $$. But you never hear it.

Doug

 

[obostic]

Hi,

I've done an extensive search and found very little information concluding which resistors to remove when using the THAT2180 series VCAs. Can anyone definitively state which resistors need removing? Even simpler, which resistors from the PCB directly corresponds to the THAT design Note 137 figure 1. resistors R2, and R3.

Thanks,

 

[astrovic]

http://diy.fischerworks.com/gssl_vca.shtml - with many thanks to Matt Fischer for this one!

Note: I think its fair to say that Matt's site is mostly a reading of the application notes and applying same to the device - so nothing is "definitive" per se (but it's pretty good :thumb: ). From my own experience, I used the 2180LB's, followed Matt's site and it worked straight off the bat.

 

[obostic]

astrmovic,


Thanks alot this is exactly what I was looking for.

 

[drive]

I'm trying to decide witch vca I'm going to use, I guess I'll go with the 2180lb because it seems that there are less things to change, is this the case ?
I've been on matt's site and there are question marks for 100k and 2 * 47k, does this mean that they don't need to be replaced ?

 

[drive]

maybe I can answer my own question, the two 47k are probably left out if you use a side chain right ?
For 100k I still dont know ?

 

[obostic]

I am using THAT2180LC and THAT2180LA and the 100K was replaced with 127K to correct the ratio, some have used 120K as well. I determined what I needed by first installing a 50K trim pot in series with the 100K resistor and a resistance of 127K gave me the correct ratio.

 

[idylldon]

Bumping this for a quick question:

When using 2180 VCAs is it necessary to change the 3.9K to a 5.1K resistor? I can't find any documentation for this other than Matt's site, which is based on a reading of the data sheet and not necessarily based on empirical measurement.

Cheers,
--
Don

 

[Gege]

Hi
I have the same questions that you idylldon

Do I change the pattern like on the Matt's Site ? (remove and replace some resistance)

I have THAT 2180LB

I followed the REV 7 and I welded all (even pin4 of VCA)

I hope not to have made mistake 

For the moment the compressor works, but I think I can improve


Sorry for my english, i'm French !

Gege

You can find my project here http://baguep.free.fr

 

[geetar_king]

Using the THAT2180 in the sidechain,  has anyone changed the 3K9 resistor in the sidechain to 5K1?


I've also left out the 47R resistor in the sidechain that connects to pin 4 of the 2180. It's not needed. No connection for pin 4.

 

[xprodux]

i built mine with  thats 2180 la's through out , bent pin 4 on both vca's , left out trimmer , everything else as is , left side chain as is  , 100 ohm changed to 127 for correct ratio . sounding lovely , ratios all good ,no probs at all .

very suprised  as this was my first diy project , after a minor resistor error she sounded great .

like to say a quick thanks to all who made the Gssl possible  , and all who post here with help .

 

[geetar_king]

My levels between Left and Right are a little off. About 0.3 dB difference

Anyone know how to correct this?    Is there any particular resistor that I can replace with a trim pot maybe to tweak??

 

[clintrubber]

PS
HOW CAN I DO FOR ADD A PICTURES TO THE POSTS?

Hi,

If I were you I wouldn't even try, since disabling Caps Lock is already too demanding for you as it seems. 

Please don't keep posting in all capitals, you should have noticed by now that it irritates people.

Apart from that feel welcome here!

Regards,

  Peter