If you look at the grid through a microscope you will see that it is actually very fine wire. The fragility comes from the fact that it only takes a few mA of current thorugh the grid to heat the wires to the point where they distort. Once the grid wire is warped, it changes the tube characteristics.
Heater-cathode leakage is not due to arcing, but conduction through a weak insulator/semiconductor.
It is not the current itself which damages the grid, as that might be less than a mA, but the migration of stuff between grid and cathode caused by the current. Of course too much current will directly damage the grid, as most small signal valves are not designed to cope with grid current. When I said 'robust' I meant with respect to a few 100uA of current. I guess that is a fairly extreme use of 'robust'!
It is not the current itself which damages the grid, as that might be less than a mA, but the migration of stuff between grid and cathode caused by the current. Of course too much current will directly damage the grid, as most small signal valves are not designed to cope with grid current. When I said 'robust' I meant with respect to a few 100uA of current. I guess that is a fairly extreme use of 'robust'!
Preamplifier with PCC88
I ask you a few sentences for Tube/Valve PCF80?
Thank you and cheers!
DF96, thanks for the information. Please to help and others drafting the preamplifier with PCC88, I need a schematic or project.
I ask you a few sentences for Tube/Valve PCF80?
Thank you and cheers!
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Hi radio!Hi
High-End tube preamplifier with 12AX7 (ecc83) is a excellent!
Regards
I made this high-end tube preamplifier with ECC83 (Philips MINIWATT).
Excellent, excellent ... all excellent. Stereo image by the depth and breadth excellent! Middle and high-toned spectrum of real tube saund, purity and high definition. Just good.
Recommendation: Who wants to enjoy the real tube saund let making this preamplifier and let enjoy.
The right thing to enjoy the tube/valve sound
Radio to thank for this preamplifier.
For this you need to provide quality power supply for preamplifier and success is there!
tank you and cheers!
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DF96, thanks for the information. Please to help and others drafting the preamplifier with PCC88, I need a schematic or project.
I ask you a few sentences for Tube/Valve PCF80?
Thank you and cheers!
PCF80 is an excellent punchy little tube. The triode and pentode operate at about the same plate current which makes it very versatile valve.
Shoog
Yes, fortunately valves are so versatile that using the wrong valve in the wrong circuit with the volume control in the wrong place can still result in not too much damage to the sound. As I said earlier in this thread, this preamp is "high-end" only in the sense of being eccentric - it isn't even ridiculously expensive! It would work better as a guitar preamp, for people who really appreciate distortion and lumpy frequency response (-45dB second, +5dB peak just above the audio range, according to its designer's measurements).
New Line-Stage
Hi guys!
For resistor R11 = 1k2 and cap 220uF/16V
Believe excellent sound gives this Line-Stage pre-ampamplifier!!.
Cheers!!
Hi
Here they are:
R1=12k, R2=30k, R7=470k, R9=1M, R8=30k R10=100k, R11=2k7, R12=560k,
R13=100k, R14=1M, R15=1k5, R16=100k/o,5W, R17=1k/1W. Out P1=50k/log
all resistors with 1% metal film!!
C1=470nF/63V-MKP, C2=220nF/400V-MKP, C3=5p6/500V-stiroflex, C4=33pF, C5=220nF/400V-MKP
C6=3,3uF/100V-MKP, C7=100uF/350V, C8=100nF/400V.
Regards
Hi guys!
For resistor R11 = 1k2 and cap 220uF/16V
Believe excellent sound gives this Line-Stage pre-ampamplifier!!.
Cheers!!
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