• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Preamp schematic...

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Guiness

Guiness

Member
Joined 2003
What do you guyz think? I nice little preamp using the WE407A. The schematic came from Gark K. Anyway the power supply is mine. I had the power transformer with double 6.3V 1A rectifier filaments. So why not double rectifier for a little gain in power.

Guiness :drink:
 

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bournville

Member
Joined 2003
...You have what looks like a 10uf cap at the top of the first triode's anode 22k resistor connecting to HT+, and this looks like it connects across the last 50uf cap in the power supply.

Is this because the pre-amp is remote from the power supply and you need the 10uf cap to prevent instability, or is there a decoupling resistor missing for the circuit diagram?
 
Joel

Joel

Member
Joined 2002
joeltunnah.com
siu sin man tho said:
...Do U feel that is it fair for test?
Click to expand...

Actually, no. And I'll tell you why - different rectifiers will each behave differently in the same circuit. They have different internal resistances, capacitances, and different choke/cap input-to-filter requirements. Doing a direct swap would produce a noticable difference because of all these factors - but that's not due to any "sound" of the rectifier itself.

A true test would be to build a complete PSU for each rect type. Adjust all circuit values so each PSU has the same level of ripple, output voltage, and regulation. Listen.

(I don't think you'd hear any difference whatsoever, but that's just my opinion)

Joel
 
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siu sin man tho

Disabled Account
Joined 2002
hi joel,

we had at least 5 person to blind test different.
Sometimes not only the spec, Use ear to hear will most important.
Do u think the NOS we300B will worse than any new build one. It cost over USD 2000 per pair. If new one can better than NOS one. I think many NOS WE300b lover cannot hear the real sound.
As U said me too.
If actually every tubes must test in their ideal condition.
I think diyer must spend too too much time to test the tubes.
They will only a little bit of time to hear music. This is my opinion.

thanks for your advise.

I will deeper consoderate your advise than I hope can improve my diy skill.

thanks

Thomas

www.diyaudiocraft.com
 
analog_sa

analog_sa

Member
Joined 2002
For a change i fully agree with Joel

Just two suggestions: remove the .47uF cap from the input - it's unnecessary. Also, two 6X5's for a preamp circuit is overkill. Why waste electricity?
Click to expand...


But then such a welcome opportunity to disagree :) i was just beginning to worry...



(I don't think you'd hear any difference whatsoever, but that's just my opinion)
Click to expand...



Why must the output cap be oil? Is everyone really in love with the oil sound or is it just used as digital antidote?


cheers

peter
 
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