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Who has experience using tube...

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Dec 15, 2019
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Who has experience using tube preamps? How often did the tube change? What problems did you encounter? 22F3AD57-9CF5-416E-923B-261351442768.jpg

I used vacuum tubes when I was young, but switched to transistors 58 years ago.
Tubes wore out and needed replacing (changing?) over and over.
Rock bands like the distortion produced by tubes and many bands replace the tubes before each show.
I like the very low distortion produced by transistors and ICs.

Not sure if you're asking about amplifiers or just pre-amps...
I've had tube audio equipment. Tubes are prone to decline in performance with age and use. If a tube gave me doubts there was a tester at my local auto parts store. I put the tube in the correct socket, waited for it to warm up, then dialed a knob selector. A meter indicated the tube's status, good or weak or gassy. It was beyond my ken to experiment with tubes. A high voltage supply is needed, as well as detailed knowledge of pin connections, etc.

Many years ago, most "convenience" stores had tube testers and sold replacement tubes because they were so unreliable. Where can you test and buy tubes today? Will they already be used and worn out?
There was an audio store in my city that sold amplifiers with tubes glowing on top. The amplifiers were solid state with transistors and the tubes were only to see and to feel their heat.


There was an audio store in my city that sold amplifiers with tubes glowing on top.
A modern way of reusing waste....and the customers (like to) pay for it.
For sure a clever business idea. (not my style)


Someones like tubes due to their their own distortion and sound and nowadays the people who want to listen original sounds pay thousands bucks for tube amplifiers even tube radios..
Aging is the most common problems for tubes and also performance degrading is another one.They produce also heat like a electrical heater..

Years ago I took my 1 year old Heathkit tubes amplifier to a MacIntosh amp clinic where they measured 25% distortion and told me to change the tubes. With new tubes it measured 1% distortion. The replacement tubes were fairly expensive to be changed every 3 months or less.

every decision has its up side and its downside

tubes are less susceptible to static discharge, EM Pulse, etc

For my 2m power amplifier I still use a tube (3CX1500C7). The output power is in the range of 1.5 kW.
Disadvantage compared to a SS-PA is the high voltage supply (size and weight). Advantage is the robustness against mismatch of the antenna.
As a transmitter manufacturer (former Ampegon) we still use tubes for the high power (e.g. short wave transmitter 500kW, 3.9MHz - 26.1MHz). The tube for this is the TH576 (Thomson).
Here is a picture of the TH576 in the 500kW transmitter.


I like tubes, for purely nostalgia reasons.

A particular problem for preamp tubes, specially in high gain stages, is that poor quality devices may not have been fully evacuated, and the residual gas molecules produce noise.
That gas will also deteriorate the cathode faster than usual.
Unfortunately, most simple emission-type testers don't have the capabilities to test for residual gas.

One question; what is a crowbar doing on top of an audio preamp?

One question; what is a crowbar doing on top of an audio preamp?

I find the dichotomy of a modern printer (and cables) in what looks like a picture from the 1930s kind of interesting. Even the crowbar looks like it could be hand forged.

Game of words) This preamplifier from the “Limited Edition”, which uses original vintage transformers made in the legendary LOMO factory. The word "crowba" in Russian sounds "LOM". LOM-LOMO)))

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