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Old 10th April 2003, 12:19 AM   #1
Guiness is offline Guiness  United States
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Default Preamp schematic...

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.

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Old 10th April 2003, 12:20 AM   #2
Guiness is offline Guiness  United States
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And the power supply
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Old 10th April 2003, 12:21 AM   #3
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Circuit looks fine to me, I guess the 407 works a bit like a 12AU7 eh? (Darnit why am I always comparing tubes to the AU. LOL)

I don't get the 1k on the output though.

PS schem?

Edit:
Ah, there it is What diodes are those? 6X5?? Can't read the chokes well either.

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Old 10th April 2003, 12:50 AM   #4
Colt45 is offline Colt45  Serbia
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6X5's arent directly heated. you can use the same filament supply for them as for everything else
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Old 10th April 2003, 01:18 PM   #5
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...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?
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Old 10th April 2003, 02:13 PM   #6
Joel is offline Joel  United States
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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?

I can't read the choke values, but I assume they are at least 10-15 henries? Then the cap values are good.

Joel
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Old 10th April 2003, 04:41 PM   #7
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Hi, the tube for rectifier if use 80, EZ80 or we417a will better than 6X5.
I don't know why, but this my test result.

thanks

Thomas

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Old 10th April 2003, 04:48 PM   #8
Joel is offline Joel  United States
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Quote:
Originally posted by siu sin man tho
Hi, the tube for rectifier if use 80, EZ80 or we417a will better than 6X5.
I don't know why, but this my test result.
Thomas, what do you mean by "better"?
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Old 10th April 2003, 04:57 PM   #9
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hi joel,

I put the same pre-amp which can use several types of rectifier tubes.
Test them in one set which we feel that it had a quiet good tone Balance.
Then use several disk & blind test to get the result.
Do U feel that is it fair for test.
any advise.

thanks

Thomas
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Old 10th April 2003, 04:58 PM   #10
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Hi joel,

its we412a, not 417a, sorry fpr the mistake.

thanks

Thomas
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