That Corp compressor pedal schematic

[atreidesheir]

New app from That Corp for a guitar pedal cmpressor.
http://www.proaudiodesignforum.com/forum/php/viewtopic.php?f=6&t=606
The designer is looking for input.

[derevaun]

This thread is relevant to my interests  Thanks for posting this!

[atreidesheir]

The 4316 is a new chip optimized for low current circuits  and Battery-operated dynamics processors
— Compressors
— Limiters
— Noise Gates
— AGCs

"The THAT4316 is a single-chip Analog Engine® optimized for very low-voltage, low-power operation. It incorporates a high-performance class-AB voltage-controlled amplifier (VCA) and true-RMS-responding level detector. The 16-pin QSOP part is aimed at battery-operated audio applications including companding systems for wireless microphones, wireless instruments, and in-ear monitors, as well as dynamics processors of all types. The 4316 operates from a single supply voltage down to 2.7V, drawing only 1.2mA at 3.3V."

Small Bear is not carrying it yet.  But they will.
Here is the datasheet link for the THAT corporation 4316 vca chip.
http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&ved=0CDcQFjAB&url=http%3A%2F%2Fwww.thatcorp.com%2Fdatashts%2FTHAT_4316_Datasheet.pdf&ei=0TmiUqjOFqnOsATsoYCICA&usg=AFQjCNEH-bZmv2ZO_2rWKR4lkkRKDA56cA&sig2=BQiGQxK1MdCswsXUu9krGw&bvm=bv.57752919,d.cWc

[jubal81]

It's available from Mouser and only $3.30. SMD only, though
A bit concerned that it's a 5V chip.

[micromegas]

http://www.waynekirkwood.com/images/pdf/A_THAT4316_Battery-Powered_One_Knob_Squeezer_Guitar_Compressor.pdf

[midwayfair]

It's available from Mouser and only $3.30. SMD only, though
A bit concerned that it's a 5V chip.

Probably because 5v is more than sufficient for its stated purposes, none of which are guitar pickups.

A humbucker can distort that on its own, without any gain at all.

[atreidesheir]

They actually make DIP adapter boards for their chips.

[wayne kirkwood]

Thanks for the link to the post.

Let me clear up this bit of confusion...

A bit concerned that it's a 5V chip.

Probably because 5v is more than sufficient for its stated purposes, none of which are guitar pickups.

The 5V maximum supply voltage of the 4316 doesn't limit it's overload or operating capability to <5V because the VCA inputs/outputs and RMS detector input are currents, not voltages. (V-I by virtue of R10 and R20, and I-V by R12 and Op Amp D.)

The resistors which convert the input and output currents to voltages can be scaled upward in value for use at elevated levels which exceed the 5V supply of the 4316. (THAT have an application note here which applies to the 218X-series but the current-in/current out aspects are the same. http://www.thatcorp.com/datashts/dn123.pdf)

The RMS detector output is not constrained by supply voltage since it scales at ~6mV/dB or ~120mV/20dB around a mid-supply value of +2.5V.

With input/output resistors scaled properly and a supply voltage to support the final output stage I-V converter's signal swing, the part can be used at pro levels of +21 dBu or more.

I do realize that most people might prefer a higher input impedance (or full bypass). Those that do need a higher input Z can scale R1 and R2. R1 could easily be 10M; R2's maximum value is limited by the MC33178's bias current.

For someone not wanting to use a variable gain output stage (Op Amp B) there is a trick that can be used to center bias Op Amp D, the VCA I-V converter, from 2.5V to 4.5V. A resistor from the inverting input of Op Amp D (also the 4316 pin 13) can be taken to ground to give the stage additional DC gain. This shifts the bias center point from 2.5V typically to 4.5V. It increases the noise gain of Op Amp D slightly and burns some current but its a useful trick.

Wayne