FET optocoupler as VR

Leolabs · 23rd September 2006, 02:59 PM

I already read the thread about the Silonex's Audiohm optocoupler "Lightspeed Attenuator",wondering how about Fairchilds's H11F1???Although the Ron is higher,about 200 ohms.

EUVL · 24th September 2006, 05:38 AM

You get poor linearity for any input signal more than +/- 0.02V (see Figure 2 Output Characteristics of Datasheet).

Patrick

consort_ee_um · 24th September 2006, 07:48 AM

Poor linearity is another way of saying distortion

Thanks for the heads up on the lightspeed attenuator thread
Those devices are sometimes known as vactrols and used by record producers to get the sound they like using compression, an ugly word for hi-fi enthusiasts. In fact the compressor is also called a joemeek after the legendary record producer who first used the technique.
Until I discovered the Silonex parts (perkin-elmer stuff is difficult to get in the UK) I made my own devices using a yellow Led (to match the wavelength of the LDR) a LDR and some 5mm heatshrink sleeve.
In the Lightspeed attenuator the device is simply used as a volume control there is no compression.
Another way of doing it is here:
http://www.maxim-ic.com/appnotes.cfm...te_number/1118

23rd September 2006, 02:59 PM	#1
Leolabs diyAudio Member Join Date: Dec 2004 Location: Bukit Mertajam	FET optocoupler as VR I already read the thread about the Silonex's Audiohm optocoupler "Lightspeed Attenuator",wondering how about Fairchilds's H11F1???Although the Ron is higher,about 200 ohms.

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24th September 2006, 05:38 AM	#2
EUVL diyAudio Member Join Date: Oct 2003	You get poor linearity for any input signal more than +/- 0.02V (see Figure 2 Output Characteristics of Datasheet). Patrick

24th September 2006, 07:48 AM	#3
consort_ee_um diyAudio Member Join Date: May 2004 Location: Hertfordshire	Poor linearity is another way of saying distortion Thanks for the heads up on the lightspeed attenuator thread Those devices are sometimes known as vactrols and used by record producers to get the sound they like using compression, an ugly word for hi-fi enthusiasts. In fact the compressor is also called a joemeek after the legendary record producer who first used the technique. Until I discovered the Silonex parts (perkin-elmer stuff is difficult to get in the UK) I made my own devices using a yellow Led (to match the wavelength of the LDR) a LDR and some 5mm heatshrink sleeve. In the Lightspeed attenuator the device is simply used as a volume control there is no compression. Another way of doing it is here: http://www.maxim-ic.com/appnotes.cfm...te_number/1118

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