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MCA - Son of ZCA
http://diyaudioprojects.com/Forum/viewtopic.php?f=10&t=3942
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Author:  Positron [ 06 Nov 2017, 15:30 ]
Post subject:  Re: MCA - Son of ZCA

mwhouston wrote:
No idea about the DAC_amp splitting.


i researched a bit on the net and some say that there will be a 3db drop in the output signal of the dac....
ultimately it can go wrong if the input impedance of the MCA is too low.


regarding the fostex fe206e that I got especially for the MCA, can this little amp be modified not to send anything above 2 or 3khz to the fostex?

Author:  KochiyaYamato [ 06 Nov 2017, 16:41 ]
Post subject:  Re: MCA - Son of ZCA

Positron wrote:
Thank you both for suggestions. I will experiment with the caps.

Is this amp driving my tweeter better? I am just looking for sound that is true to the original, not smudged by too many unnecessary electronics with lots of capacitors,resistor, chips, trafos...

One more question. Can i connect two MCA (mono) amps to the left channel of my DAC and two MCA (mono) amps to the right by splitting the output signal of the DAC? Will this create distorion? Harmonics? Each amp will drive his own speaker.

Greetings and thanks again.

I'm not sure on what you mean nor do I know about dac splitting, but you should wire the two amp inputs in parallel. In theory it should not distort when you wire input of amps in parallel.
Positron wrote:

i researched a bit on the net and some say that there will be a 3db drop in the output signal of the dac....
ultimately it can go wrong if the input impedance of the MCA is too low.


regarding the fostex fe206e that I got especially for the MCA, can this little amp be modified not to send anything above 2 or 3khz to the fostex?

The impedance is 8ohms and with calculation.
https://www.electronicproducts.com/RC_F ... lator.aspx
With a 10uF the cutt off is about 1.99khz
6.8uF on onput of mca is about 2.92khz cutt off. (this is high pass)

http://sim.okawa-denshi.jp/en/CRtool.php
I would suggest that you try 82ohms in series with input then a 1uF to ground for a 1.94KHZ low pass filter
82 and 0.68uf for a cut off of 2.85khz
Keep in mind your amp has input resistance, therefore the resistance of filter must be made small,otherwise loading effect on output changes the freq response.
Keep in mind the MCA is a inverting amp, and it may sound weird when your sub amp is non inverting but your mid highs are inverted.

I would suggest that you low pass the forstex full range at about 6-8khz before you put tweeters, full range should generally have better vocal midrange soudn quality than, midrange ,tweeters.
From my epxrience you can boost the highs a bit of any speaker by connecting a zobel for it. Something to look at. My 4inch fullrange lacking of highs had got a good fix by having a zobel.
http://diyaudioprojects.com/Technical/Speaker-Zobel/

Author:  Positron [ 05 Dec 2017, 09:26 ]
Post subject:  Re: MCA - Son of ZCA

mwhouston wrote:
No idea about the DAC_amp splitting.


After some research i found out that the best dac for signal splitting is one with a tube output stage. but i also have found that some put a single jfet instead of an opamp at the output of a dac.
is it possible to use a single jfet or tube at the output of a dac which would also at the same time supply biast current for the mca?

Author:  KochiyaYamato [ 12 Dec 2017, 05:59 ]
Post subject:  Re: MCA - Son of ZCA

Positron wrote:
mwhouston wrote:
No idea about the DAC_amp splitting.


After some research i found out that the best dac for signal splitting is one with a tube output stage. but i also have found that some put a single jfet instead of an opamp at the output of a dac.
is it possible to use a single jfet or tube at the output of a dac which would also at the same time supply biast current for the mca?

You can consider using the supply from your mca and making a small regulator with lm317T, no heat sinks required since small load. The voltage you need to drop also can be calculated ask me for further details.

You can of course try runing it direct, or also try a rc filter, This means putting a 220-4.7k ohm resistor in seriers with the supply from mca, at the other end of 4.7k connecting a resonable size cap 470uF+ cap from 4.7k to ground, this acts as a simple regulator that is good for running small loads. This is how many valve amp guys get smmoth supply.

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