Sourcing THAT2180?

[Bo Deadly]

..we're talking REALLY low impedances around here, I see no reason to complicate this for the DIY'er by groundplaning just-because-we-can..?

Looking at the datasheet, the control ports are supposed to be driven with low impedance so, yes, the ground planes around those lines should not matter. But the the input does have a series resister which is 20K in the example circuit in the datasheet.

SIP packages are sometimes used for amplifiers so that the input can be at one end while the output is at the other to minimize undesirable feedback. I don't see any reason why that would be so important here but they used a SIP and put the input on pin 1 and output on pin 8 so I have to wonder why.

I don't know if a ground plane would really make a difference in practice, but why not add it? It costs nothing.

 

[elskardio]

I revised my adapter PCB to add the Trim adjustment on the back. It's using a Bourns 3224G to give an easy access from the top.

I shared the PCB on OSHPARK:
https://oshpark.com/shared_projects/y8AraFvH

The GERBER files are available here:
https://www.dropbox.com/s/wu5nraco5x898xt/2181_Adapter_Sym.zip?dl=0

Cheers

 

[Gustav]

I don't know if a ground plane would really make a difference in practice, but why not add it? It costs nothing.

If you want a ground plane, you can easily add it, before you etch or order.

Select the polygon tool.
Draw a path around the area you want the plane in, and make sure the end joins to the start of it.
Hit the "ratsnest" icon.

If you want to adjust the distance and spill, right click the line you draw, and select "properties".

Hope that helps!

Gustav

 

[john12ax7]

Important:

It is now claimed by people-in-the-knows that there is a very real possibility that the THAT chips in SIL-package are not coming back.

Reason being a fallout with the next-last place on earth doing SIL's, somewhere in india

/Jakob E.

Thanks for the info.  Not good news as this would imply there wouldn't be a final lifetime buy option either. Quite the abrupt end.

 

[Tekay]

As we use thousands of THAT circuits we checked with the European THAT Corporation distributor and they have confirmed that the VCA’s in SIL package will not disappear!

 

[Gustav]

As we use thousands of THAT circuits we checked with the European THAT Corporation distributor and they have confirmed that the VCA’s in SIL package will not disappear!

I was informed by mail, my backorders would arrive "between April and July", and when I said, in a phone conversation, "ok, I can will hold out for your worst case scenario", I was told, that would be a bad idea.

I was also told, the SIL manufacturing was shut down, not just due to COVID, but strikes and problems in India, and my distributor were considering offering the SOIC on a converter, because they were not confident, it would come back.

I dont know if they are seeking solutions to get it back on track, but I will not hold my breath waiting for SIL chips for deliveries in this uncertain scenario, when it is not that difficult to solve it - Maybe ask your rep, if they are in fact talking about the convert solution, or if they have different, and solid, information, so you can make the right choice!

Gustav

 

[abbey road d enfer]

Can't we suggest they offer a DIP solution? I know the DIT market is not their main concern but they know how important it is for their reputation.

 

[Tekay]

Just did some testings with V2181 in one of our BC1-THD.
Had to solder in a 51r between pin 2 and 4.
I can trim down the THAT2181B  THD to around 0,0007% without any GR, the V2181 lowest was 0,0015%
I guess the V2181 is a DBX2151

 

[abbey road d enfer]

Just did some testings with V2181 in one of our BC1-THD.
Had to solder in a 51r between pin 2 and 4.
I can trim down the THAT2181B  THD to around 0,0007% without any GR, the V2181 lowest was 0,0015%

Thanks for the info. It makes it a more than decent performer.

I guess the V2181 is a DBX2151

Could very well be.

 

[Bo Deadly]

I can trim down the THAT2181B  THD to around 0,0007% without any GR, the V2181 lowest was 0,0015%

Wow, that is kinda great. If you still have the test rig setup, it would be nice if you could tell us what the THD is at -15dB of gain (and +15dB) with the same part / trim.

 

[Tekay]

Wow, that is kinda great. If you still have the test rig setup, it would be nice if you could tell us what the THD is at -15dB of gain (and +15dB) with the same part / trim.

Used a BC1-THD for measurement so I can't measure -15dB of gain, I'll check the +15dB  THD next time I have it on the bench.

 

[abbey road d enfer]

Actually THD of Blackmer VCA's depends less on gain/attenuation than on the absolute input or output current.
Typically, a VCA with 1mA peak input current and 180uA output (15dB attenuation) has the same THD as with 180uA input pk current and 1mA output current (15dB gain).
Indeed, for the same input current, THD will be much higher on a VCA that has gain than on one that attenuates.

 

[porkyc]

Regarding That vs V2181.
I arrived at the same conclusion. See thread in test and Meas. "Coolaudio VCAs".
It is interesting that Coolaudio now call them 2159; the 181 number has gone.
And no, they are not as good as the THAT product. But... cost vs performance.
SIl vs SOIC. Mouser certainly seem to think they are coming back. Horrible lead time, though.
But dropping the SIL pack in these times had crossed my mind as well. Time to move on?