Pro Audio Design Forum

When I originally designed the matrix I was concerned about gain build-up during encoding in the Mid (L+R) channel and also in the decoder which produces not L and R, but 2L and 2R . In anticipation of that I designed the following circuit and then allowed myself to get talked out of using it off-fo...

The LM833 is compared by Douglas Self to the NE5532 with slightly higher noise and somewhat less drive capability. I think the 833 was National's answer to the 5532 and it's not a bad choice either. There may be a modest need for speed and output current in this stage to keep the output impedance fr...

It's 77 here right now at noon with a high in the low 80s predicted. Great weather for doing after-Christmas cleanup.

If it dries out I may go for a bike ride. We've had really high humidity and things are very slick for 1-1/4" English racer tires.

so low gain opamp noise is not as much of a concern as source impedance at control ports. You are correct that the op amp should buffer the pad or have less than unity (inverting) gain. I misspoke previously. An op amp's impedance rise vs frequency is particularly critical with most BIFETS showing ...

Merry Christmas Roger and everyone!

Just back from a long day of eating....

John - One op amp driving one port would be best. We might consider however having a resistive attenuator at the Ec and using something more like 20dB/V rather than the native 6.1 mV/dB. As long as the source impedance at Ec is low the attenuator would not add significant noise or CV modulation. Off...

Uh, is that monitor a CRT? It looks like the image is wall-to-wall so it's probably an LCD. If it's a CRT it could create significant radiated and cinducted interference. I often pickup 15.575 kHz and ~59.94 Hz measurement spurs at very low level that I think are conducted through the power line fro...

Very nice job! I have to say, I really have no clue on how to meassure noise. Could this reading indicate it's below 120dB? Also, it's not noise but a slight psu hum.I don't hear it with master & headphone volume cranked up full but still The noise level is very low. To get an actual measurement...

Hi Jonas - I got the prototype board from Roger on Thursday and hope to be stuffing it today. We've had some really good weather in Texas the last couple of days - 75 and sunny - and I needed to take advantage of that. Today it's 28 degrees with a high of 38 so doing work in the shop with a hot sold...

So the lamp is a transducer burnout protector rather than de-boing device.

EDIT: Listening to some of the heavily distorted Perez Perado tracks from the 50's and 60's I can see why they added the lamp.