Tuesday, August 13, 2019

Daven 3 1U4 electron tube microphone preamplifier vs Pleiades (130Ω,40mH) microphone gentle slope filter


At your risk. All known safety precautions should be followed. Any voltage or current can be dangerous. A fuse should be connected in series with a battery for fire hazard protection.


Signal path:


Male singing voice - Fostex M80RP mic at 6-8in - Pleiades (R,L) filter or Daven 3 1U4 preamp - Sony TC-D5 Pro with its 20dB pad if Daven is connected - Sennheiser HD580


If both Pleiades filter and Daven pre are connected the sound is very thin, unusable.


If none of them are used ie mic straight to Sony the sound is so bass and mid heavy that is unusable. (Proximity effect produces exaggeration of mid band as well.)


If only Pleiades filter is connected and no Daven pre, the sound is natural but bandwidth seems exaggerated ie there seems not to be flat frequency response from producer's brain to listener's brain.


When the Daven 3 stage 1U4 electron tube preamp is only used (no Pleiades filter) the sound is natural, bright and very interesting. Reminding classic great recorded vocals of the past reproduced from a vinyl record.


The Daven preamplifier had been powered by one 1.2V battery for cathode filaments and 5 used 9V batteries in series creating a electric field potential difference of 41V for the anode (or plate supply).


The Daven did not noticeably distort this time. Possible reason that thus time it's 2400Ω? output impedance is terminated with the a few KΩ mic input instead of the HD580 headphones much lower impedance.



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