Upgrading VCAs on Amek Angela II

[meverylame]

Hey all,
*Cross post from PRW*

I'm managing a facility that has an Amek Angela II. The other day I had a session where I had to use a laptop as a sampler and was playing some songs through it to line check and was pretty appalled by the quality of the channel. Given this is a 20 year old console so its likely pretty due for a recap, the experience did make me wonder about trying to upgrade the VCAs (inline board so and also has a vca on both the big and small faders) while I'm in there. The VCAs in the console is the DBX 2150a that has the symmetry adjustments on the backend, according to the THAT corp guide I need to be using a 2181LB(which is the trimable middle grade modern vca) . Talking to a few different techs I've received a few different responses as to what to do, which is to use the 2181LA (the trimmable high grade modern vca) and also to use the 2180LA (the pre-trimmed high grade VCA). SO, for starters, what do you guys think? 2181LB? 2181LA? 2180LA? Jump off a bridge?

For convenience here's the THAT guide on it:

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

Secondly, and really my initial question when researching this. I was initially considering using the trimmable style THAT VCAs, and in the guide for replacing them they have a table (see below) with some example values for how to correctly modify the circuit to work given a certain operating voltage.

So they reference having more support for integration on the 2181 datasheet http://www.thatcorp.com/datashts/THAT_2 ... asheet.pdf

For the life of me I can't find any data on this (could be an idiot), but even it ends up being better to use the pre-trimmed VCA, I'd still be very curious to know how to correctly calculate this. Here's the schematic for the board.

Any thoughts? Anyone actually do this mod? Bueller?

Thanks a million guys!

 

[Tubetec]

The monitor mix section actually sounds better and cleaner than the main fader output from the channels due to the Vca.
If I were you Id' be thinking about getting the vca's out of the equation . In the studio I was in we got hold of some Angela non Vca modules side by side test was night and day . Retrofitting conventional log faders and doing away with the vca's is possible as far as I know.

 

[JohnRoberts]

They say the 2181A is the best of the best... why would they lie.

Have to tried re-trimming the old ones?

JR

PS: Of course you can mod a channel or two and then listen to them.  8)

 

[meverylame]

Tubetec, Yes, I totally agree that completely deucing the VCA would be ideal, but definitely takes this from a sub 1000 USD project to a  2k-4k project. So, yes, that is the ultimate winner, but I don't think the owner of the complex is gonna jump for that. Also there is some broadcast work that happens in here where the VCA functionality is great.

John, OK, 2181A is what I've been leaning towards. On paper are a lot cleaner than the current 2151a. No idea what that'll sound like, but its a start. I'm planning on trying a pair of channels "all the way", recap, Jim Williams PIP card, VCA, yada yada yada, to see what's worth spending the money on. So, that said, any ideas on how I can calculate on how to implement the 2181a in to the circuit I'm talking about?

Thanks again for the replies!

 

[john12ax7]

I would agree with JR, re-trim the old ones first and see what difference it makes. If you decide to change then go for the 2181 since the trim pot is already there. The 2181A may be unnecessary, I would be inclined to try all 3, A, B, and C. Adjust, measure and listen to see what makes the most sense value wise.

 

[moamps]

.... how I can calculate on how to implement the 2181a in to the circuit I'm talking about?.....

Remove R200, replace R201 with 240k (B ver) or 680k (A ver), replace C97 with 22pF NP0/COG, adjust the lowest THD using VR17.

 

[fazer]

Also recap that bitch.

  I worked at a studio with 2 motzarts.  They were delivered. And in the 1st year Ameck sent techs out to determine the caps all needed replaced.  6 years later all the caps needed replaced again.  The motzarts had a vca bypass switch and it did clean up slightly but I heard great mixes from those boards with the vca automation. 

 

[fazer]

Also the headroom was not like a neve or api and such on the ameck so make sure you don’t run levels hot.  I’m sure your doing that but lots of people don’t follow standard op level on the daw playback.  You want 0 VU 1.225 volts out of the daw not a hot level you trim back to fit and no peaking red led’s in the chain.  The motzarts was clean when not overloaded anywhere in the chain.

 

[meverylame]

Remove R200, replace R201 with 240k (B ver) or 680k (A ver), replace C97 with 22pF NP0/COG, adjust the lowest THD using VR17.

Hey thanks! Two quick things, the datasheet does mention that all the examples are spec’ed on is a bipolar 15 volt system, the console is 18, does that matter? Also does the trimmer being 22k matter?  Again, thanks for your time.

 

[meverylame]

Also recap that *****.

  I worked at a studio with 2 motzarts.  They were delivered. And in the 1st year Ameck sent techs out to determine the caps all needed replaced.  6 years later all the caps needed replaced again.  The motzarts had a vca bypass switch and it did clean up slightly but I heard great mixes from those boards with the vca automation.

Oh I have spent quite some time behind ole Mo’. The one I spent the better part of my early 20s behind had the RN modules and from what I remember sounded pretty great, but was pig on maintenance. Thing was also a furnace, just cooked the caps. And thinking of it, the switch lubes prolly took it pretty hard too. I remember liking it a lot more than a neve VR, and about as much as a SSL. I can say, all the outside engineers HATED the layout and labeling of the board. The horizontal patch bay layout, really seemed to blow people’s minds. Not to mention the all the really nomenclature they used on the channels, like prefader was a greater than sign, and assign to monitor path was a triangle. Just absurd.  The upside of this is that I’ve always felt like I’m basically unshakable on any console or patchbay because that one was so weird. Anyhow, thanks!

 

[abbey road d enfer]

Any thoughts?

If your channels sound like s..t because of the VCA's, it points out to either a very poor implementation, or a need for re-trimming and/or recapping.
Assuming this mixer sounded fine when it went out of the factory, I would start with retrimming the VCA's, which costs almost nothing, then I would re-cap a couple of channels and compare to the others.
The difference of performance between a well-tuned 2150 and a 2181 is not tremendous. If you end up replacing the VCA's, use the 2181A.

 

[meverylame]

If your channels sound like s..t because of the VCA's, it points out to either a very poor implementation, or a need for re-trimming and/or recapping.
Assuming this mixer sounded fine when it went out of the factory, I would start with retrimming the VCA's, which costs almost nothing, then I would re-cap a couple of channels and compare to the others.
The difference of performance between a well-tuned 2150 and a 2181 is not tremendous. If you end up replacing the VCA's, use the 2181A.

Yeah, this is mid 90s update that is really more similar to an Einstein, than the 80s version that people actually dig on. I've trimmed the VCAs in the console as is, and am still looking for some more help than what that provides. My current ideology is to take 2 channels all the way there with recap, VCA mods, and Jim Williams PIP upgrade, and then simply recap two channels to get a firsthand impression what each modification provides.

 

[moamps]

...the datasheet does mention that all the examples are spec’ed on is a bipolar 15 volt system, the console is 18, does that matter?

No. If it is good for 2150, it will be fine for 2181 too.

Also does the trimmer being 22k matter?

No.

 

[abbey road d enfer]

My current ideology is to take 2 channels all the way there with recap, VCA mods, and Jim Williams PIP upgrade, and then simply recap two channels to get a firsthand impression what each modification provides.

What is the "Jim Williams PIP upgrade"? If it's about replacing the op amps with new ones that go faster than light, I would not rush to do that...

 

[meverylame]

What is the "Jim Williams PIP upgrade"? If it's about replacing the op amps with new ones that go faster than light, I would not rush to do that...

No it's not the put video amps everywhere method of "upgrading".

 

[jensenmann]

IMHO recapping will make the most obvious difference in sound, more than chip swapping. While you´re at it you can increase the coupling caps in capacity. That will lower lowend phaseshift. And if you´re determined then add small film caps (0,01-0,1uF) parallel to every electrolytic for smoother and more natural highend.
The sonic difference between 2150 and 2180 VCAs will be most obvious with handling a lot of GR. If you don´t use the VCAs for extreme compression or level rides then the difference may not be that huge. OTOH no VCA sounds better than any VCA, though.