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.
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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Hi nicoch46nicoch46 said:
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
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.
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
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
RCruz said:
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.
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
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
1k 5w are ok to test the shunt ?
to much new stuff , lot space , I need to rebuild the amp ,order better hook cable ,some caps, metal and so on...🙄
to much new stuff , lot space , I need to rebuild the amp ,order better hook cable ,some caps, metal and so on...🙄
1K means 46mA on the dummy load. Rather OK. Also means 2W on it in your case. 5W is OK even for a lengthy test then.
Hi Salas
I have been playing with the leds and the best choice seems to be 1 bright blue + 2x "normal" red leds.
With these i get 7.49v dropout.
Can I use bright leds ?
Ricardo
I have been playing with the leds and the best choice seems to be 1 bright blue + 2x "normal" red leds.
With these i get 7.49v dropout.
Can I use bright leds ?
Ricardo
for R6 mod I have made heatsink for Bc550/60 from nice flat mundorf OFC copper 😀 😀
plus some turn of thin copper wire (for garden) ad cpu paste
plus some turn of thin copper wire (for garden) ad cpu paste
Best option for D1 is made of 4 leds.. two red + two yellow. (7.65v drop)
Should I put the red ones between the yelow or connect two reds to gnd + two yellow to Q3 base ?
Ricardo
PS: R6 mod is fundamental but I did not know it needed heatsinking.
Should I put the red ones between the yelow or connect two reds to gnd + two yellow to Q3 base ?
Ricardo
PS: R6 mod is fundamental but I did not know it needed heatsinking.
Don't matter the sequence, put them as you like. They add up their residual noise in a less than linear total anyway they are put. Eager to hear what you hear.
But don't press yourself to hear a difference.
*In Nicoch shunt there is 46V out so the Voltage across the BJT is high and it nears thermal max with the stronger than a resistor load CCS current. That is why he sinks it.
But don't press yourself to hear a difference.*In Nicoch shunt there is 46V out so the Voltage across the BJT is high and it nears thermal max with the stronger than a resistor load CCS current. That is why he sinks it.