Tandy PZM mics pre-amp

  
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The Sennheiser Dummy Head Stereo recording was a huge breakthrough in the concept of recording at the time. It enabled the reproduction of 3D information as our ears perceive it. The other day I received an email from someone who happened upon this page. He reliably informed me that the Tandy PZMs and the Crown ones used identical piezo modules s
Tandy PZM mics pre-amp - schematic

ourced from the same factory. Apparently the best ones were selected for the Crowns, and the rest were relegated to the cheap Tandy models. So there you have it - quality was spread to the masses because it was probably seen as a good commercial opportunity to `minimize waste`! The modules are just screwed to the hard metal plates and some of them stripped so I glued them on with two part epoxy. The wooden wedges are reinforced with massive oregon pieces at the back. These mics have a particular sound characterised by vibrancy and warmth. They are a bit distorted by audiophile standards but the spatial information makes up for it. Many of the overdubs on the `Sheds` album were done with this device, and you can here the mics picking up the acoustic qualities of some of the lead guitar as well as the sound from the guitar amps. One day I found one of the mics had failed, the problem being that the little audio transformer in the battery powered module had gone open circuit. This was a disaster for me! I bought some new type boundary mics from Radio Parts but I think they are a bit harsh - and still powered by a small lithium battery - with no on / off switch!. I decided that it would be good if I could replace the module with a powered preamp to both supply power to the PZM mic and retrieve the signal. I did this by supplying the mics with a small constant current Darlington circuit. It worked a treat. The preamp is noisier...



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