Compressor with Transistor make-up Gain

[Amled87]

So, I recently found a passive compressor schematic on the internet. The idea piqued my interest, so I decided to build 4 into a single space and then use transistor gain stage afterwards with a potentiometer wired as a variable resistor to control the make-up Gain/volume. I've provided both schematics and was wanting to make sure this would work.

I am using a BC547 transistor for my gain, and a 10k Linear potentiometer as my output volume control. I decided to use the single transistor buffer as it would also convert my signal to a low impedance and help with connecting it to my AD converters without impedance matching issues.

 

[ruffrecords]

Your transistor is powered via a 470uF capacitor in series with the supply so unfortunately it will not work. Also it is an emitter follower so it will have no gain. Lastly the bias resistors at 1K are far too low and will unnecessaily load the compressor. Oh, and you output potentiometer is wired backwards.

Cheers

Ian

 

[merlin]

That 'compressor' has been floating around the net for years. It doesn't work.

 

[ruffrecords]

That 'compressor' has been floating around the net for years. It doesn't work.

I think it is an old Elektor project intended to be driven from a loudspeaker output.

Cheers

Ian

 

[Amled87]

That 'compressor' has been floating around the net for years. It doesn't work.

Hello Merlin, not to argue with you but could you explain what is going on in this video? Because it's this exact circuit, without the transistor output stage I'm considering (for make-up Gain) but it definitely sounds compressed to me.

 

[Amled87]

I think it is an old Elektor project intended to be driven from a loudspeaker output.

Cheers

Ian

Your transistor is powered via a 470uF capacitor in series with the supply so unfortunately it will not work. Also it is an emitter follower so it will have no gain. Lastly the bias resistors at 1K are far too low and will unnecessaily load the compressor. Oh, and you output potentiometer is wired backwards.

Cheers

Ian

Hello Ian, the 470uF I just threw in there but, the negative side goes to ground the correct way to filter the power. Would the correct way be to use a coupling cap and my signal off the collector (similar to my signal coming from the plate of a vacuum tube)? This would produce gain/amplification correct? The pot symbol is the only symbol my software had available, it's just there to simulate using a potentiometer for volume control.

 

[Amled87]

I think it is an old Elektor project intended to be driven from a loudspeaker output.

Cheers

Ian

Ian, would this be more accurate? It's a transistor gain stage, feeding an emitter follower and then into my pot for volume control.

 

[merlin]

Hello Merlin, not to argue with you but could you explain what is going on in this video? Because it's this exact circuit, without the transistor output stage I'm considering (for make-up Gain) but it definitely sounds compressed to me.

I think we're hearing distortion rather than compression. But do let us know how you get on, I never got it to work but YMMV

 

[Amled87]

I think we're hearing distortion rather than compression. But do let us know how you get on, I never got it to work but YMMV

To be honest, this is just something for me to experiment with while I wait on my parts for a GSSL. However, I do appreciate the response! If it doesn't work, I still have a few LDR/LED based schematics from ESP I'll use instead.