Zen -> Cen -> Sen, evolution of a minimalistic IV Converter

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#1,485
Hi

Without buffer the sound was constrict, and i had sensation to loosing control and energy in the bass frequency

With buffer no more these sensations
Now the input inpedance of DCB1 it's 28k and Res I/V is 2K

Hope my poor english was clear

Marco

Inviato dal mio GT-S5300 con Tapatalk 2
 
#1,486
Bias point drift?

I have been some kind of "bias drifting"
With a senoidal signal of 1kHz, output is clean an undistorted in the first minute.
After 1st minute, negative half-wave becomes clipped.
If signal is square, 1kHz, no clipping.
If signal is senoidal, 40 kHz, no clipping.

If turn-off some time, 1kHz senoidal is unclipped again 1st minute.

I have fed the circuit with batteries and a regulated psu too. Results are the same independently of what PSU you use.

I believe that the capacitors are responsible for some kind of drift when they get charged, but not sure.
 
#1,487
LuisMCP said:
I have been some kind of "bias drifting"
With a senoidal signal of 1kHz, output is clean an undistorted in the first minute.
After 1st minute, negative half-wave becomes clipped.
If signal is square, 1kHz, no clipping.
If signal is senoidal, 40 kHz, no clipping.

If turn-off some time, 1kHz senoidal is unclipped again 1st minute.

I have fed the circuit with batteries and a regulated psu too. Results are the same independently of what PSU you use.

I believe that the capacitors are responsible for some kind of drift when they get charged, but not sure.
Click to expand...

Your absolutely right, i had the same problem with some other russian film caps. But then i switch to Nichicon Muse caps and had almost no detectable DC leakage. - Nothing i could detect with my basic equipment anyway.
 
Last edited:
#1,491
EUVL said:
Your "drift" is very likely due to leakage in your capacitors.


Patrick
Click to expand...

I have tested today two new type of caps:

Polarized Elna Silmic
Bipolar Nitai electrolityc

Polarized cap ended with a great clipping.
Bipolar Nitai don't

I will try Nichicon Muse next days.

I have measured harmonic distortion with the Nitai's and found 2nd harmonic below 30 dB of fundamental with only 0,2Vrms of signal (18V psu) 😱😱

Probably i will get some litycs of low leakage for testing
 
#1,496
Patrick,

Just as I thought...

I tried a Tx 2352 1.5 K and a Caddock 2K
With the 2K Caddock the resulting sound, for my ears, was better

Also,

I'll try Wima MKS XL 10uF and BG N 470uF instead of my current Nitai BP 220uF and will report

Thanks a lot

Marco
 
#1,500
Hi All

after long trial i finished my output stage of my Copland
It have CEN for I/V and Gherard Buffer for LPF

For Cen i choose Wima MKS 10uF for decoupling Cap and Texas Tx2352 for resistor I/V

The sound it's wonderful, grainfree and very clear, never heard CD's sound so well
So, Patrick, THANK YOU!!

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