Dhillon Posted October 12, 2019 Posted October 12, 2019 Dear SNA'er needing your help. Full story is I recently purchased a Aqvox phono, one of the optional function is there're internal DIP-switches to bridge the output-capacitors. But it's only safe to operate if the connecting Preamp input has a coupling-capacitors http://www.aqvox.de/phono.html So then I raised the question to the Preamp manufacturer. (they replied me in German). But instead of answering my question they just sent me the diagram of the preamp design Anyone can tell me if the design has capacitors at the input please? (I intentionally removed the model number from the below diagram, so if you know the model by the design, please don't say so / don't ask)
Ian McP Posted October 12, 2019 Posted October 12, 2019 If using the top five RCA inputs the pre amp has an input capacitor (0.1uF 63V) before the first valve. If switched to balanced mode (the two XLR inputs below the five RCA inputs it has no input capacitor. In most cases you will be using the RCA input for MM/MC rather than balanced mode. 2
Decky Posted October 12, 2019 Posted October 12, 2019 (edited) The only problem is it should be at least 1uF (2uF to be generous). Ah, bummer - sorry I did not see that input impedance is 1Mohm - yeah 0.1uF will do. Either way you should aim for a corner frequency for the RC high pass filter to be around 1Hz . (Fc=1/2*Pi*C*R) Edited October 12, 2019 by Decky
Dhillon Posted October 12, 2019 Author Posted October 12, 2019 (edited) thanks @Decky I think I'll leave the phono caps on and connects to the preamp with balanced then. It has to be at least one in between anyway so hopefully those in Aqvox are of better quality (and it seems safer this way as well) Edited October 12, 2019 by Dhillon
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