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Old 26th March 2013, 05:26 AM   #5811
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Mr. Salas, thanks that you always encourages us positive.
And you properly explained and guided that my words were not enough.
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Old 26th March 2013, 10:20 AM   #5812
Phisci is offline Phisci  South Africa
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Salas, I built the 5v reflektor and after running for about 3 months, it's output voltage started to oscillate between 5v and 10v. Input was about 15v. Any ideas as to what could happening?
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Old 26th March 2013, 10:27 AM   #5813
Salas is offline Salas  Greece
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Make basic checks to its transistors and mosfets while powered like vbe, vgs, something should have failed.
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Old 26th March 2013, 11:53 AM   #5814
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Salas sorry my ignorance Reflektor is also shunt, right?
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Old 26th March 2013, 11:58 AM   #5815
Salas is offline Salas  Greece
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Don't tell everywhere, but yes, it is.
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Old 26th March 2013, 12:43 PM   #5816
Phisci is offline Phisci  South Africa
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Thanks Salas and do you think this could have been caused by inadequate heatsinking?
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Old 26th March 2013, 03:19 PM   #5817
Salas is offline Salas  Greece
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With no specific data, can't guess.
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Old 26th March 2013, 04:17 PM   #5818
pchw is offline pchw  United States
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Sorry for the igorant, what is the difference between the reflector and the bib?

Thanks,
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Old 26th March 2013, 04:57 PM   #5819
Salas is offline Salas  Greece
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The Reflektor uses a current mirror trying to keep currents in both legs the same while the bib uses a conventional common base voltage error amplifier.
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Old 27th March 2013, 12:18 PM   #5820
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Default Reflektor R5 (1k) listening tests

After reading Kazuo’s remark about the influence of R5 (1k) in post #5801 I decided to run some listeningtests myself.

First a little explanation regarding R5. R5 determines two important values:
1. The current in the Wilson current mirror. Ic = Vgs/R5. The higher the R5, the lower the current in the current mirror.
2. The amount of correction signal fed to M2 to counteract output voltage change. The higher R5, the higher the amount of correction signal. Were this circuit a DAC, then R5 was the IV resistor. Actually it is an IV resistor, because current change in the current mirror is converted to voltage here to drive M2.

The question is, what is a greater sonic advantage: a higher current in Wilson current mirror or a stronger correction signal?

Listening tests:
I started with R5=1k and paralleled it with another 1k, just like Kazuo did. In comparison with 500 Ohm music sounded a bit more rounded and friendly than with 1k, but also less dynamic and airy, and with 1k there was more micro detail. So I decided to look what happens if you increase (instead of decrease) R5. Because this boosts the correction signal it is important to check the output for stability with an oscilloscope. I went from 1k to 2k, to 3.3k, to 4.7k, to 7.5k and ended with 13k. I listened to every single step back and forth and with every step there was an increase in spaciousness and detail, without any additional harshness. 7.5k was very detailed, full and warm. 13k was clearly the best but was a fraction more lightweight than 7.5k. The disadvantage is that with 13k the Ic of the current mirror has dropped to 0.3 mA (in my case with IRF840 and Vgs = 3.98V). In all cases the output remained stable. So no issues here.

Also the kind of resistor had quite an influence on how it sounded. For example a Vishay CMF55 resistor sounded in comparison to an old non-magnetic carbon film a bit cold and technical, and I preferred the character of the carbon film.

Peter
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