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Old 11th May 2009, 08:38 PM   #1741
Salas is offline Salas  Greece
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Try easiest wrap way and see in practice if hum goes. If sound worsens or hum field don't go 100%, then we think why. Don't forget to ground the tape to chassis. It must have electrical continuity to GND. Take care of covering secondary exit.
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Old 11th May 2009, 11:19 PM   #1742
Salas is offline Salas  Greece
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Ricardo, I have a mod 4U to try. Instead of just D1, can you use a 3.9V-4.3V Zener plus two or three Leds until you reach about 7.5V on the Cascode transistor base? If yes, tell me if you can hear lower noise or different tone. I don't have this version handy to mod myself, but I wanna know.
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Old 12th May 2009, 09:50 AM   #1743
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I will do that in the weekend.

Thank you Salas
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Old 12th May 2009, 10:26 AM   #1744
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Ricardo if you have spare caps you can tray kg-R-Jensen on psu....
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Old 12th May 2009, 05:19 PM   #1745
RCruz is offline RCruz  Switzerland
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Quote:
Originally posted by nicoch46
Ricardo if you have spare caps you can tray kg-R-Jensen on psu....
Hi nicoch46
I did think about it but I do not know if it is needed anymore. The hum is field generated and it is my present focus.

Sound is becoming real magical with the present setup...

Hi Salas

Regarding D1 mod, I use only leds in my 317 based sregs.... Can I do the same here and loose the zener ?

If I must use a zener, can I use two in paralell ? (This tech reduces noise in the sregs).

Ricardo
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Old 12th May 2009, 08:15 PM   #1746
Salas is offline Salas  Greece
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I just put the base voltage of a small Zener in the Vref string there bcs its equivalent almost to a led, so to avoid using many LEDS. But if practically does not bother you, do it all LEDs. Just trim to around 7.5V total. Green or red are OK. The thing is capacitor bypassed, but bcs 6.5-9V is not a best region for Zeners, I wanna see if some noise still escapes. Up to 4V7 Zener must not scare you, or above 12V.
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Old 13th May 2009, 05:57 PM   #1747
RCruz is offline RCruz  Switzerland
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The schematic I am using (Gain 46db for medium MC ~1mv) indicates D1 = 1N4738A (8.2v zener), so I am a little confused.... why use 7.5v instead ?

Also I do not understand the frase : "Up to 4V7 Zener must not scare you, or above 12V." Do you mean zeners generate max noise from 6 to 9 v so 12 volts is ok ?

Sorry for the nube questions but I need to know.

Ricardo
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Old 13th May 2009, 06:20 PM   #1748
Salas is offline Salas  Greece
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Quote:
Originally posted by RCruz

Do you mean zeners generate max noise from 6 to 9 v so 12 volts is ok ?
Ricardo
Yes.

The 8V2Z is bypassed by a capacitor. Generically its noisier than Zeners under 6V or 12 and over. We did not have noise, but lets see if some escapes the bypass.
7.5V I slightly prefer for THD in first stage maybe. And it can be done with LEDs.
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Old 13th May 2009, 06:34 PM   #1749
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I believe this is a must do mod.

I do not know if I can reach exactly 7,5v with leds only.... What is the best voltage [<-window->] or the minimum possible value?

Ricardo
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Old 13th May 2009, 09:37 PM   #1750
Salas is offline Salas  Greece
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7.5-8.5V
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