"Cool" VCA

Well, that won't work. Try this:

** Take another look at figure 4. The graph indicates THD v *amplitude* showing the range from 20mV to 10V rms. "Vrms" should be mVrms.

Figures 2 and 3 show that THD is largely independent of frequency, for a given output level.

BTW: The Coolaudio V2164 is electrically the same as the obsolete Analog Devices SSM2164.

.... Phil

Horrible data sheet.

In fig 3, you can throw away all the chips and use the four pots to control gain.

In fig 6.3, trash the VCA chip and use four MDACs to control gain.

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John Larkin         Highland Technology, Inc 

lunatic fringe electronics

That'd be quite a VCA that could handle 20kV RMS. The same error is present on the AD datasheet, too. Putting amplitude on a logarithmic scale from 20-20k-whatever doesn't really help understanding...

They're up for sale in quantities of 100s for $1.50 on the site, they can be had for about $3.50 at a couple US distributors. Probably a lot less than the AD part cost when it was active

Well, the AD datasheet may be more to your standards but it retains the error of putting Vrms on a 20-20k scale.

a buck fifty for four sections in quantities of 100s is pretty reasonable and for some applications probably gives the LM13700 a run for its money in the VCA role.

The ADI data sheet is a lot better. The cool people stole the graphs and muggled the text.

The chip could be useful in some instrumentation apps, but it's not very precise and it is noisy. OK for audio, barely.

We're working on three different sensor simulator boxes now, all needing precise analog attenuation. The slow ones use 16-bit MDACS, and the fast one (around 10 MHz i/q) will use Analog Devices precision analog multipliers. They are I think the only people still making precision multipliers (and dedicated DDS chips.)

--

John Larkin         Highland Technology, Inc 

lunatic fringe electronics

You're up early this morning, John! Or is it a late night? :-)

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John Larkin wrote in news: snipped-for-privacy@4ax.com:

snipped-for-privacy@decadence.org wrote in news:pnlsgt$bfl$1 @gioia.aioe.org:

Digikey shows two non-ADI multipliers, the MPY634 (old Burr-Brown part) and the Renesas HA9P2556, probably an old Harris part.

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John Larkin         Highland Technology, Inc 

lunatic fringe electronics

Sometimes I wake up around 3AM, for an hour or so, and think or something. I think that may be a natural pattern.

Sometimes the cat snores and wakes me up too.

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John Larkin         Highland Technology, Inc 

lunatic fringe electronics

A lower noise part, the Dual VCA from THAT corp is THAT 2162

I need precision linear multiplication for my 10 MHz i/q box, so I'll probably go with the AD835. It's 250 MHz, and analog very quantitative.

--

John Larkin         Highland Technology, Inc 

lunatic fringe electronics