Questions tagged [tube]

The word "tube" may refer to a broad range of engineering items, including electron (vacuum or gas) tubes.

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My DIY tube amplifier distorts more than I planned

I have built a JTM145 clone. The original amplifier is clean and distorts when the volume is turned up, but my own copy of that amplifier distorts at low volume at the second 12AX7 tube from pin 7 to ...
Eternal_Sunshine's user avatar
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45 views

Help understanding the control circuit of a gas discharge tube

I'm trying to interpret exactly how you get this famous IxU curve of a gas discharge tube you can find on several places, including the Wikipedia page about electric discharge. Image - Original work: ...
user2934303's user avatar
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1 answer
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Tube preamp overdrive question

Is it possible to add an overdrive gain pot (instead of just simply a bypass switch) to a preamp tube circuit? I am designing a new amplifier, and I want to include an overdrive/distortion option to ...
Mike Hale's user avatar
1 vote
1 answer
129 views

RF power amplifier tuning of output stage tube vs transistor

In the old days with vacuum tubes for power amplifiers we carefully tuned the output stage, dipped the plate current to get maximum efficiency. Looking at todays transistor PA circuits I don't see a ...
user3799318's user avatar
2 votes
1 answer
118 views

Required transformer voltage for voltage regulator tubes in series

First of all some small context: I am attempting to design and build a clock with old electricial components, without silicon components. This question is about the power supply circuit. Note that I ...
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2 answers
234 views

Is it possible to add a potentiometer instead of a fixed resistor to control negative feedback?

Here you see the circuit of my tube amplifier. Is it possible to replace the resistor with a 250k potentiometer to control the negative feedback, or can it cause some other problems?
Eternal_Sunshine's user avatar
2 votes
1 answer
565 views

How does the feedback in this tube amp output driver work?

The figure shows the output stage of a vacuum-tube audio amplifier. While I was reading through this schematic, I noticed there is a some kind of feedback associated with R24. However, this feedback ...
Emm386's user avatar
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Voltage output on thyratron gas tube relaxation oscillator VCO?

I know that thyratron gas tubes can be used to make a sawtooth like relaxation oscillator: My question is for a modification of this same circuit that makes it act like a voltage controlled ...
Michael Weaser's user avatar
8 votes
2 answers
958 views

Why is a pentode tube more power efficient than a triode tube?

As title. I read some article and it says something like this: Tetrode was invented to reduce grid-plate capacitance. Pentode was invented to reduce secondary emission. I also heard that a pentode ...
Moses's user avatar
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321 views

Looking for Power Transformer for ECC99 OTL Headphone Amp

I'm planning on building an OTL headphone amp using a pair of ecc99 (I got matched pair of soviet 6n6p in my hand). Eliminating output transformer would reduce the complexity of the circuit and the ...
Moses's user avatar
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What is secondary peak to peak of 290BEX transformer if primary pp is 325V and turns ratio 1:2.95?

I want to be absolutely sure of this because it is the first crucial part of my LTSpice Fender 5e3 simulation. Currently I have this .subckt(with comments): ...
Youka Naava's user avatar
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I have a carvin v3m 50watt tube amp head, red plating/bias help

The amp has 4 el84 tubes and 4 12ax7 pre amp tubes, the amp lost about half of its volume and the power tubes are red plating, is there any thing other than the tubes that I should be looking out for ...
Joe Cortez's user avatar
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2 answers
146 views

How to match harmonica impedance to a tube amp to eliminate feedback

What circuits eliminate feedback between hi z harmonica mics and high gain guitar tube amps? Do FET circuits work? I have used tube bases attenuators in the past for 50 watt amps, but they reduce the ...
William Edwards's user avatar
0 votes
2 answers
285 views

Are fluorescent tubes dangerous?

I'm disassembling a Sega GameGear. The capacitors inside are all rated 50v or lower, so it shouldn't be hazardous in that regard (I will discharge them anyway just to be sure). However, the metal ...
mars's user avatar
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1 answer
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need for decoupling capacitor in a Fender Bassman

why is there no need for a decoupling capacitor in the second preamp stage (highlighted section)? I would imagine a 0.02-400V capacitor just before the grid of the second half of the valve to block ...
Sarkipinty's user avatar
0 votes
2 answers
84 views

Gas discharge tube load type

I can not find any information about the type of load of neon lamps, for example neon probe or wall contact plug or extension cord with switch with small red lamp. I think this is a passive capacitive ...
Szymon's user avatar
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Short circuit in Peavey Valve King VK212

This is a follow up question from: Guitar amplifier repair: burnt fuse, capacitor, what else? I continue to work on the same case. In another module I've found a short to ground where the red dot is: ...
Piotr Tyburski's user avatar
1 vote
2 answers
3k views

Replacing selenium rectifier diode with silicon 1N4007

I want to replace this selenium diode on an old tube amplifier with a silicon equivalent. Normally, this diode would have a lower value resistor in series with it such as a 15 ohm. Instead, this one ...
Jon's user avatar
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3 answers
212 views

Photo-multiplier Tube Pin Configuration

Pin configuration of a photo-multiplier tube (PMT) is presented in its manual as can be seen in the attached image. All dynodes have been related to specified pins (numbered circles in the image) ...
Sam's user avatar
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2 votes
2 answers
211 views

Biasing network for phototubes and photomultipliers

I have some doubts about typical biasing network for vacuum phototubes and photomultipliers. Precisely, let's start by a simple photocathode. I have seen some biasing network like this one: In this ...
Kinka-Byo's user avatar
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14 votes
1 answer
354 views

Why is there a winding on a capacitor?

I just came across this tube RIAA preamp on which there is a coil on the input capacitor, can someone please explain what's the reason of such thing? The schematic and the actual circuit bellow. The ...
Gabriel Santos's user avatar
3 votes
5 answers
1k views

Obtaining 4-4.2V rail from 5V output of LM7805 voltage regulator

I'm creating a numitron clock with 4xIV-9 tubes (seven-segment filament displays) and have decided to illuminate them using shift registers controlled by an arduino. Each segment takes a voltage of 4-...
Daniel Bod's user avatar
0 votes
3 answers
647 views

Are these UV-C tubes meant to be run only on pure AC ballast?

I’ve this portable small T5 4W UV-A 300-400nm black light tube lamp with me. I’m trying to see if it’s possible to use a 4W UV-C lamp in the same fixture. But I noticed that the lamp has the violet ...
The_Vintage_Collector's user avatar
2 votes
0 answers
235 views

Fuzzy digits when driving with TPIC6B595

I designed a schematic and PCB of a simple Nixie clock and I hope that someone will be able to explain what's happening. The problem is that when I'm driving the cathodes with TPIC6B595 shift ...
Adam's user avatar
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12AX7 Valve Overdrive/Distortion Effect Pedal

I'm following the schematic below using the recommendations plus a couple of extra LEDs. With the footswitch in the enabled position, I'm not getting any sound. In the bypass position, the input and ...
Joe's user avatar
  • 161
6 votes
2 answers
2k views

Troubleshooting Hum in a Tube Guitar Amp

I have a Fender Deluxe Reverb Reissue guitar amplifier that hums whenever I turn on the reverb. It sounds like loud 60 cycle hum. The reverb effect is still applied, but is accompanied by the hum. ...
Avid Pro Tool's user avatar
0 votes
1 answer
456 views

How to measure the output impedance of a valve preamp?

I was trying to measure the output impedance of a DIY preamp for the past couple of days without any luck. Each time, I got to the same result of around 3K3 ohm, which is unbelievably low. This is ...
i_alan's user avatar
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1 vote
2 answers
117 views

Replacing elements in a tube amplifier

I assembled a tube amplifier.According to the specified scheme (Old Russian radio "Record 66"). 1.What is the function of capacitors C9 and C8 ? 2.What will change the capacity of these parts? Will ...
Gen Ts's user avatar
  • 113
2 votes
1 answer
491 views

Identifying Noise in 12AU7 Based Headphone Amplifier

I've been working on making a tube based headphone amplifier as a fun personal project. The amplifier is based around this 12AU7 vacuum tube. The project for the most part is following this existing ...
Nick J's user avatar
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1 vote
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570 views

Magic Eye Tuning Tube Variable Negative Voltage

I am thinking about several applications of magic eye tuning tubes as display pieces and had a question about their operation. I have attached a sample circuit from a datasheet for an EM84 tube. I ...
Efram Goldberg's user avatar
6 votes
2 answers
1k views

UHF Tesla coil powered by low voltage?

I want to know if it is possible to use a 2.4 GHz magnetron as a oscillator for a Tesla coil circuit. The idea is to use a oscillating relay-driven step up transformer (12 V to 10 kV) and then charge ...
South African Railfan's user avatar
1 vote
2 answers
1k views

What is a ESD tube?

In the ESP32 datasheet, what do they refer to with "ESD tube"?
DavidEnds's user avatar
0 votes
2 answers
74 views

covering sides of LEDS without adding heat

I'm doing a project in which a 5mm LED is near a 5mm phototransistor. There are times in which the sensor must pick up external light even with the LED on. I understand one option is to turn the LEDs ...
Mike -- No longer here's user avatar
1 vote
1 answer
328 views

Tube amps on voltage regulator

I have one basic question, because I don't know much about tube amps. I live in a country where during winter, voltage can be from time to time low (around 160V-180V). I decided to keep my amp safe ...
Whoopty Doo's user avatar
2 votes
1 answer
429 views

an/prm-10 grid dip question - how the voltage can be negative at the grid? [duplicate]

I am trying to repair a recently bought AN/PRM-10 grid dip. I have replaced some electron tubes by new ones and (almost?) everything seems to be OK regarding the voltages at the pins of the electron ...
MikeTeX's user avatar
  • 1,864
4 votes
4 answers
1k views

Open-air electron tube

So, I know that vacuum tubes only work because they're, well, a vacuum, and gas-filled tubes have a hysteretic effect relating to gas ionization. My question, however, is this: Would an open-air '...
Hearth's user avatar
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0 votes
1 answer
811 views

Preamp for Magic Eye VU meter [closed]

I want to build a Magic Eye Tube VU. This tutorial http://www.antimath.info/electro/vu-meter-em84/ says: If this circuit is used with a tube amplifier, the “IN” connection in the picture is ...
Velociraptor's user avatar
3 votes
2 answers
739 views

12 - 330v boost converter

I recently bought a G10/241E tube and I need a power supply for it. There are no designs of a 330V DC power supply and no buck-boost converters would work with such voltage. The datasheet and example ...
Velociraptor's user avatar
2 votes
5 answers
6k views

Triode - how come grid is "more negative" than cathode?

This is probably the most lame question of all the time here, but... I cannot understad grid-cathode "negative" polarization. For me, grid is always positive to the cathode. I mean, in practice, ...
emroe's user avatar
  • 65
9 votes
3 answers
3k views

Why are thermionic valve/tube heaters generally designed to be 6.3 V?

Why are the heaters generally 6.3 V (or multiples thereof)? Does it make for an easy transformer winding ratio when used in countries with 120 VAC or 240 VAC mains? They often pull quite ...
Colin's user avatar
  • 4,539
0 votes
1 answer
5k views

Compatibility & Interchangability of KT88, KT100, KT120 and KT150 Tubes in Tube Amplifiers

Are (immediately from the start or over time) the tubes that come with a tube amplifier (say the popular KT88 in Single Ended mode or Push Pull mode) replaceable with say the larger KT120 or KT150 any ...
Sam's user avatar
  • 515
3 votes
2 answers
553 views

Replacement for tube-based trigger switch (Thyratron) in high-voltage supply

A now-deleted question asked whether it's possible to replace the trigger in a specific application (laser supply, source here): and other things. For me, it boils down to a single, less ...
Marcus Müller's user avatar
1 vote
2 answers
2k views

Why the current in X ray tube is in milli amps

If we see a X ray generating tube the voltage applying to tube is in kV, but the tube current is in milliamps. Why this current is in mAs not in amps?
Ashok Kumar's user avatar
2 votes
4 answers
2k views

Step down transformer for vintage tube amplifier

Hi so I've just bought a 60's tube guitar amp from the U.S, I live in Australia. Through searches across the internet I've found a few potential issues with the safety of running the amp through a 240-...
Alex Holroyd's user avatar
0 votes
1 answer
329 views

CAM 5 LASER CUTTER : needing to change the laser tube [closed]

My boss and I discovered that one of the laser tube needs to be changed, and when we figured which one needed it, I told him not to touch the red wire, that there may still be power in it. Well he did,...
Josh Blackburn's user avatar
0 votes
2 answers
2k views

Tube amp low voltage [duplicate]

I am building a 18W tube amplifier based on this layout. I found a schematic for a similar amp. my problem is that there is low plate voltage on all of the tubes (by plate I mean pin 3): when I ...
Sarkipinty's user avatar
0 votes
2 answers
408 views

What component: a glass tube wrapped with a wire mesh and has a single metal pole inside?

I found this while trying to fix my noisy hot/cold water dispenser. It has a blueish glow and makes a loud buzzing noise of around 56-58 Hz. I'm planning to replace it, but there doesn't seem to be ...
kelvinilla's user avatar
0 votes
2 answers
489 views

Guitar Tube Amp RC Filter frequency fluctuation

In a simple LP or HP RC filter, is there a scenario where the centering frequency can fluctuate? So say the filter is a low pass and its set to pass everything up to 800hz, is there a situation where ...
user43970's user avatar
2 votes
1 answer
200 views

Gas Tubes: neutralization of space-charge causes drop in tube resistance? Deionizing voltage re-combination?

The following paragraph is from Chapter 3 of the book Principles of Electronics. When cathode is heated, it emits a large number of electrons. These electrons form a cloud of electrons near the ...
user avatar
3 votes
1 answer
161 views

What is a Reacto Tester unit and are there any projects in which I can use it?

I was given an old piece of electronics. It is a Reacto Tester made by Antronic Corp from Chicago. After a quick glance at the manual it seems that its a tester for tube display units such as ...
KingsInnerSoul's user avatar