Clean, modern and inexpensive VCA?

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cyrano

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AFAIK Cool audio licensed the design from the original designers and they used the original layout.

In theory, that should yield an exact replica, but the production method is unknown, so ymmv.
 

JohnRoberts

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AFAIK Cool audio licensed the design from the original designers and they used the original layout.
do you have a link reference about that?
In theory, that should yield an exact replica, but the production method is unknown, so ymmv.
THAT corp also used a high performance semiconductor platform that could make a difference in VCA performance. Cool audio is associated with Behringer FWIW.
===

To repeat the OP's query, has anybody bench tested these ICs in comparable applications?

JR
 

cyrano

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do you have a link reference about that?

Sorry, John, couldn't make it surface on Google. The quote problem is part, but having generic named brands like THAT and cool audio certainly doesn't help.

It's just something I've read a long time ago. And I couldn't find much about it on the Cool Audio website. But boy, have they expanded their range:


And now TC Electronics is part of the group, they'll probably be adding a lot of other stuff too.
 

Rob Flinn

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Just the fact that the 2164 with all 4 sections in parallel has the same noise performance as a Black can DBX from 40 years ago should tell you something about these cool audio VCA's .....
 

scott2000

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Wonder what's up with these guys? They even do the 4301 from looking around their info. But it doesn't reflect on their home page set up. Guess you'd have to inquire....


 

Bo Deadly

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Just the fact that the 2164 with all 4 sections in parallel has the same noise performance as a Black can DBX from 40 years ago should tell you something about these cool audio VCA's .....
Clearly the cool audio ICs are for cheap synths. For that, they're great and serve their purpose. I'm glad they exist.

For pro-audio, the problem isn't noise as much as THD. But I don't think it's fair to compare the cool audio 2164 to something from THAT. A proper comparison would be Cool Audio 2181 to THAT 2181. THD of the cool audio part is in the 0.02% range which is really not bad. But the THAT 2181B is in the 0.002% range which is very good and comparable to conventional amplifier circuits without a VCA.

That is if you believe the datasheets. It would be interesting if someone did an empirical comparison.
 

mr coffee

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The confusing numbering is pretty annoying. A couple important points worth noting,,

The CoolAudio V2162 is not related to the SSM2164-style SSI2162 paralleled VCAs - it is a Dual Blackmer VCA with both Vc+ and Vc- control ports , and comes in an SO-16 package.

@cyrano and JR,
IMHO the CoolAudio V2162 is pretty unlikely to be licensed from THAT and use THAT masks from the 2181 or 2162.

I am basing this on the simple fact that the THAT 2162 has an on-chip resistor from Vc+ to the SYM trim pin, and the CoolAudio V2162 requires an EXTERNAL resistor from Vc+ to the SYM pin to adjust the offset. The external resistor on the CoolAudio trim diagram is specified to be 51 ohms, roughly double the value of the on-chip resistor on the THAT 2180 series (25 ohms) and the THAT 2162 (30 ohms).

FWIW
 

Bo Deadly

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I'm guessing you didn't look at the link I posted earlier in this thread .
No but if you mean this post data:

Code:
Test Criteria             dBx202 | B&B Audio | THAT 2181B | V2164 | Cool V2181
Distortion
Unity gain SMPTE  IMD 0dBV 0.03%        0.01%       .007%   .058%        .031%
Unity gain THD+N 1Khz 0dBV 0.01%        0.01%       .012%   .021%        .014%

Noise
Noise (l 0dBV) 20-20Khz BW -90dB        -90dB       -95dB   -91dB      -93.5dB
Noise (rel 0dBV) CCIR-468  -83dB        -84dB       -88dB   -84dB      -87.5dB

what am I misunderstanding?

I'm not sure I trust this person's figures for that 1KHz THD which THAT clearly shows being almost 0.002% at 1Vrms.

Taking low noise / low THD measurements is highly non-trivial. It's not uncommon to find that replacing or repositioning some wires causes numbers to drop dramatically. I wouldn't accept anything like this as gospel.
 

Rob Flinn

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No but if you mean this post data:

Code:
Test Criteria             dBx202 | B&B Audio | THAT 2181B | V2164 | Cool V2181
Distortion
Unity gain SMPTE  IMD 0dBV 0.03%        0.01%       .007%   .058%        .031%
Unity gain THD+N 1Khz 0dBV 0.01%        0.01%       .012%   .021%        .014%

Noise
Noise (l 0dBV) 20-20Khz BW -90dB        -90dB       -95dB   -91dB      -93.5dB
Noise (rel 0dBV) CCIR-468  -83dB        -84dB       -88dB   -84dB      -87.5dB

what am I misunderstanding?

I'm not sure I trust this person's figures for that 1KHz THD which THAT clearly shows being almost 0.002% at 1Vrms.

Taking low noise / low THD measurements is highly non-trivial. It's not uncommon to find that replacing or repositioning some wires causes numbers to drop dramatically. I wouldn't accept anything like this as gospel.
The table I'm reading on the first page of the data sheet says for the 2181B Max trimmed THD @1v, 1KHz, 0dB is 0.02% not 0.002% .......
 

Bo Deadly

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The table I'm reading on the first page of the data sheet says for the 2181B Max trimmed THD @1v, 1KHz, 0dB is 0.02% not 0.002% .......
Those are part code specs. So they might be a hedge. The number in Electrical Characteristics says max 0.008% and the plot in Figure 10 shows 0.002% so the numbers are all over the place. Gotta love datasheets.
 

Lee_M

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Just the fact that the 2164 with all 4 sections in parallel has the same noise performance as a Black can DBX from 40 years ago should tell you something about these cool audio VCA's .....
In fairness, the SSM2164 design isn't much younger than the "black can" DBX.
 

Lee_M

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You would expect all 4 of it's VCA's in parallel to show a better Distortion figure than 1 black can though.
Does paralleling VCA's reduce distortion? I was aware of the benefits to noise reduction, but I didn't realise it affected distortion too.

Comparing the datasheets of the SSI2164 and the SSI2161 doesn't give any indication of reduced distortion (THD figures are identical for both, under all test conditions), but it does show the 6dB noise reduction for the SSI2161.



On a side note, I'd also trust the genuine Sound Semiconductor parts to more reliably meet their datasheet specs than the Cool Audio knockoffs. I just wish they made through hole versions of their chips, I'm not a fan of working with SMT components.
 

neil.johnson

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Does paralleling VCA's reduce distortion? I was aware of the benefits to noise reduction, but I didn't realise it affected distortion too.

Comparing the datasheets of the SSI2164 and the SSI2161 doesn't give any indication of reduced distortion (THD figures are identical for both, under all test conditions), but it does show the 6dB noise reduction for the SSI2161.



On a side note, I'd also trust the genuine Sound Semiconductor parts to more reliably meet their datasheet specs than the Cool Audio knockoffs. I just wish they made through hole versions of their chips, I'm not a fan of working with SMT components.

Yes paralleling addresses the SNR but not distortion, as the noise is incoherent and so increases by 3dB for each doubling whereas the coherent signal increases by 6dB giving an effecting SNR boost of 3dB per doubling. So four in parallel would see the SNR increase by 6dB but won't have any appreciable affect on distortion as that is related to the signal.

It's getting really, really hard to find packaging houses doing DIP now. From what I understand SSI have no plans to introduce any DIP parts, so adaptor boards it is. Tis the sign of the times....

Oh, and the V2164 is "derived" from the original SSM2164 whereas the newer SSI2164 has been improved by the original designer, including fixing the infamous missing-rail self-destruct.

Neil
 

Lee_M

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It's getting really, really hard to find packaging houses doing DIP now. From what I understand SSI have no plans to introduce any DIP parts, so adaptor boards it is. Tis the sign of the times....
Yeah, I spoke to them a while back about DIP versions of their parts, they seemed pretty confident that option wasn't going to be on the cards. Definitely a shame, but I guess it's to be expected with modern IC production.
Oh, and the V2164 is "derived" from the original SSM2164 whereas the newer SSI2164 has been improved by the original designer, including fixing the infamous missing-rail self-destruct.
Yeah, the SSI2144 (updated version of the SSM2044) had a few little tweaks like that done to it, I had good results using those in place of the vintage chips, despite having to use adapter boards.

I know that the Alfa (Latvia) version of the SSM2164 VCA (AS2164) includes the missing rail protection, but I'm not sure if that part has undergone any other improvements beyond that. It is available as DIP though, which is always nice.


Alfa actually makes quite a few different VCA types, including a 2180 clone (along with various other remakes of specialist/niche synth ICs, transistor arrays, etc.) but I've not played around with any of their parts yet, it'll be interesting to see how they stack up.

 

Rob Flinn

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Does paralleling VCA's reduce distortion? I was aware of the benefits to noise reduction, but I didn't realise it affected distortion too.
Yes, you're right there. However the 4 VCA's in parallel gives a 1dB noise improvement over the black DBX. So it still doesn't really cut it.
 

Lee_M

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However the 4 VCA's in parallel gives a 1dB noise improvement over the black DBX. So it still doesn't really cut it.
The noise performance of these chips is heavily dependent on the Rin and Rout resistors.

Using 30k for Rin/Rout (the largest recommended value for the 2164) gives the worst noise performance, while using 7k5 reduces output noise by up to 8dB in Class AB mode or up to 12dB in Class A mode.

Further still, those resistor values need to be divided by the number of VCAs if you're using multiple sections in parallel, in order to actually realise the noise improvements of that arrangement.

Unfortunately, the measurement thread linked above doesn't seem to mention which value of resistors were chosen for Rin/Rout in those tests.

The attached images are cropped from the SSI2161 and SSI2164 datasheets.
 

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neil.johnson

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Yes, you're right there. However the 4 VCA's in parallel gives a 1dB noise improvement over the black DBX. So it still doesn't really cut it.
Ok, cool, but what can you buy and use today?
You have THAT 2180 class and you have 2164 class. Sure, the 2180 class are better performers, and you pay for that performance: looking on a UK disti (thonk.co.uk) the THAT 2180C is £5.72, the SSI2161 is £2.99. Engineering is all about getting the right level of performance for the right price.
 
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