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In the Forum: Melquiades Amplifier
In the Thread: Planning my DSET
Post Subject: Second Stage Half-6C33C impedancePosted by anthony on: 6/22/2015
 Romy the Cat wrote:
Anthony, I think you take the right this in a wrong way. Sure the quality of the coupling caps is important but you truly shall not be worry about it. Make the amp, get comfortable with it and then change the damn cap. It is very simple to do and I am sure you will find zillion caps to experiment with. Do not worry about it for now.  For a full range amp 2uP will be enough. The cap and plate impedance will create low pass filter. You want this filter to be a couple octave under the lower cut off of your transformer. If you get at full power -3dB at let say 18Hz then to cut off for the filter at 7-8 Hz would be sufficient.  With 2uF you will be somewhere there… Do not forget that you can always parallel the caps, to bypass the caps… there is a lot that might be done..  but later….

I will do it own the track.  Going round in circles I was.

Romy, I am checking crossover filter calculations against your DSET schematic and am having a little trouble determining the high pass filter component of the Upperbass Channel.  The 0.022uF coupling capacitor is supposed to roll off the high pass at about 60Hz according to the schematic but without knowing the input impedance to use for the half 6C33C I cannot actually check this and look at what effect different sized caps in there will have on the -3dB point.  Using 60Hz as the -3dB point and 0.022uF as the capacitor I end up with an input impedance of about 120kOhm for the half-6C33C as you run it in your DSET Milq.  Does this sound about right? 



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