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Old 30th July 2013, 12:02 PM   #1481
EUVL is offline EUVL  Europe
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Panasonic FC 470F 35V, 10mm dia. x 20mm Length.


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Old 31st July 2013, 07:18 AM   #1482
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Patrick and suburra

why are you using 1.4K as a R_iv with PCM63
Isn't It a 1.5 K recommended with PCM63
do I need a buffer If I drive 20 K attenuator with SEN
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Old 31st July 2013, 08:04 AM   #1483
suburra is offline suburra  Italy
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Hi

Patrick, for PCM 63, recomended 1.4K for 2Vrms Out
I tried 1.4K/1.2K/2K
2K was better for my ears, and Caddock Mk132 better then Vishay TX2352

For sure 10K shunt attenuator needed a buffer
Maybe with 20K you can try without

Marco
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Old 31st July 2013, 08:43 AM   #1484
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thank you for reply

can you describe difference with / without buffer
you said that lows are not correct ?
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Old 31st July 2013, 02:40 PM   #1485
suburra is offline suburra  Italy
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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
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Old 12th August 2013, 07:33 AM   #1486
LuisMCP is offline LuisMCP  Spain
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Default 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.
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Old 12th August 2013, 09:34 AM   #1487
ryanj is offline ryanj  Australia
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Quote:
Originally Posted by LuisMCP View Post
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.
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 by ryanj; 12th August 2013 at 09:40 AM.
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Old 12th August 2013, 09:58 AM   #1488
LuisMCP is offline LuisMCP  Spain
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Quote:
Originally Posted by ryanj View Post
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.
mmmm... interesting.

Ouch! I have read BOM and saw *bipolar* caps.
Mine are polarized caps
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Old 13th August 2013, 01:34 PM   #1489
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Quote:
Originally Posted by LuisMCP View Post
mmmm... interesting.

Ouch! I have read BOM and saw *bipolar* caps.
Mine are polarized caps
you can use polarized caps
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Old 13th August 2013, 02:15 PM   #1490
EUVL is offline EUVL  Europe
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Your "drift" is very likely due to leakage in your capacitors.


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