The B-17B needs some type of indication to show when the preamp and amplifier are in the “clean” signal area and when they are cranked up past the level where distortion kicks in. For this purpose you can’t beat the cool factor of the old analog VU meters. Unfortunately these have become rare in the digital age, and where they are available they tend to be expensive. It would not be hard to spend more than the entire cost of the amplifier parts on a couple of new analog VU meters.
With that in mind I considered designing some LED bar graph type VU meters for the B-17B preamp prototype. But then I recalled a piece of surplus equipment that I had purchased for just a few bucks a while back. It is – or was – a commercial-grade VHS editor. And as you can see from the photos below, it has some miniature VU meters built in. My intent when I bought this thing was to use it for surplus parts, since I don’t plan on editing any VHS tapes in the near future.
Although my intention is still to design the B-17B to use off-the-shelf available parts, I thought it would be OK to use these meters in the preamp prototype. We can figure out later if we want to use LED meters in the final version or find a source for reasonably priced analog VU meters. So with that it was on with the teardown…
What a mass of spaghetti in this thing! I definitely got my money’s worth just in wire and hardware.
Eventually I got to the front panel. You can see the board with the VU meters below.
And with a little desoldering, here they are. Success!