• 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.

My first preamp with tubes

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dirkwright

dirkwright

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Joined 2011
DF96 said:
Could you explain? I would expect a pentode to have poor PSRR due to its high anode impedance, but not amplify noise.
Click to expand...

OK, I spoke too soon. This shows rejection of power supply sine wave @ -1dB or thereabouts. I know that in other circuits I've been working with, I saw as much as +20dB amplification of power supply sine wave energy. Part of it depends on the size of the anode resistor. The bigger the resistor, the better the PSRR because it forms a voltage divider with the tube. Of course, this requires much higher B+ voltage, but that's the price of performance. B+ is set to +300V here, with 1 volt AC @ 120 Hz.
 

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Max Martin

Max Martin

Member
Joined 2011
I lost one of my KT88 tubes so i can't listen anymore :mad:

Anyway. Before that happened i realized that the russian 6n3p-ev are actually a better tube then GE 5670 in every way. Cleaner, more dynamic n details are all there. Just transparent and neutral. GE 5670 sounds weiled, slow and very laidback. Like listen to this preamp with cathode cap bypass that I also listen to a while (again)

So the CREE sic diodes staying and also the 6n3p.
 
Shoog

Shoog

Member
Joined 2002
Max Martin said:
I lost one of my KT88 tubes so i can't listen anymore :mad:

Anyway. Before that happened i realized that the russian 6n3p-ev are actually a better tube then GE 5670 in every way. Cleaner, more dynamic n details are all there. Just transparent and neutral. GE 5670 sounds weiled, slow and very laidback. Like listen to this preamp with cathode cap bypass that I also listen to a while (again)

So the CREE sic diodes staying and also the 6n3p.
Click to expand...

You have just realized that the much praised "tube sound" isn't what you want after all.

Shoog
 
Max Martin

Max Martin

Member
Joined 2011
That is so true. :) Nowadays when i listen to "transistors" i can feel how my brain starts to pick out things it does wrong.. with tubes i just listen to the music and everything else is just there without being harsh n rough despite it's very detailed.

One thing I've always noticed when comparing tubes to transistors is how good treble i can get. Without ever ever being harsh. Never had such a good upper octave as now noir midrange =)

SUM: I'll hope they manufacture tubes till the day I die =)
 
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S

stocktrader200

Member
Joined 2008
I have also noticed how the "harshness" disappears with tube amplification.
I can't see it on the scope but it is there. The circuits are also very simple to construct. I tried a 12AX7 as the VAS stage vs a 2N5551 (same circuit) and the difference is incredible. A 12AX7 VAS stage is going into my SX - 3700 rebuilt receiver.
 
Max Martin

Max Martin

Member
Joined 2011
I got my new quad of KT88s and one thing is sure, no more chinese tubes :)

ohh wow so open, engaging, dynamic sound i have now. Midrange is all i could hope for. (read/listen Audax PR170M0/ PHL 1120 midrange) And suddenly it feels i have twice the power :)

Genalex Reissue KT88: What a joy to my heart :p
 
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