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Forum: FAQ - Upgrades and Tweaks 8th May 2018, 09:28 AM
Replies: 0
Views: 352
Posted By FAQ Team
WAD PreII conversion to Cathode Follower stage

WAD PreII conversion to Cathode Follower stage

The PreII was designed to provide a 5x gain for low output sources such as the Leak Troughline tuners. However, the majority of equipment has...
Forum: FAQ - Upgrades and Tweaks 6th May 2008, 12:58 PM
Replies: 0
Views: 9,409
Posted By FAQ Team
Triode and Pentode Connection for KEL84

This is a basic connection guide to change the operation of the output stage from Ultra Linear to Triode and Pentode. It does not include details of any other adjustments that may be required to...
Forum: FAQ - Common Problems 8th January 2008, 02:30 PM
Replies: 0
Views: 11,090
Posted By FAQ Team
Rectifier Flashover WAD Kits 34, 6550, 2A3

Kit/Kat 34, Kit/Kat 6550 and 2A3PSE Rectifier Flashover - Fitting Balancing and Surge Resistors


Kit/Kat 34 and Kit/Kat 6550


Some owners have had problems with the valve rectifiers...
Forum: FAQ - Technology 22nd November 2007, 10:16 AM
Replies: 0
Views: 9,674
Posted By FAQ Team
How a Valve Works - Blue Valves etc - Link

This is one of the best articles on the web covering how valves work, their uses, lifespan, and problems,

http://www.vacuumtubes.net/How_Vacuum_Tubes_Work.htm
Forum: FAQ - Technology 13th August 2007, 12:56 PM
Replies: 0
Views: 5,299
Posted By FAQ Team
Rectifier Types and Transformer Ratings

A rectifier converts AC current to DC. It uses one or more diodes. Diodes are like electrical one-way valves, allowing current to pass only on one half of the AC sine wave.

There are many...
Forum: FAQ - Upgrades and Tweaks 12th January 2006, 01:06 PM
Replies: 0
Views: 6,768
Posted By FAQ Team
Solid State Diodes - Choice

Solid State Diodes - Choice

Standard solid state diodes are reliable but retain a charge when they switch which causes a spike. This can cause direct RF radiation into circuitry and the...
Forum: News 7th January 2006, 12:48 AM
Replies: 11
Views: 3,576
Posted By FAQ Team
Re: Good FAQs

Thanks All,

The FAQ was put together a while back and we hope to update and extend it. Please let us know of any topics you'd like to see covered.

If anyone has an article they'd like to offer...
Forum: FAQ - Technology 6th January 2006, 11:25 PM
Replies: 0
Views: 5,173
Posted By FAQ Team
What is a push-pull amplifier?

Name for the configuration of the output stage. We saw in another FAQ answer that Class B operation is efficient, but suffers from the disadvantage of outputting an amplified, half-wave rectified...
Forum: FAQ - Technology 6th January 2006, 11:24 PM
Replies: 0
Views: 4,555
Posted By FAQ Team
What are Matched Valves and do I need them?

Each type of valve works within a set of electrical parameters. These include anode voltage, screen voltage (if applicable) and grid bias. When a signal is applied to the grid it is amplified by a...
Forum: FAQ - Technology 6th January 2006, 11:23 PM
Replies: 0
Views: 3,615
Posted By FAQ Team
What is meant by Class A, Class B etc?

This refers to the portion of the signal waveform that is amplified by a valve. In Class A, the entire signal waveform is amplified. Quiescent current is set at a level such that anode current...
Forum: FAQ - Technology 6th January 2006, 11:22 PM
Replies: 0
Views: 4,510
Posted By FAQ Team
What is a single-ended amplifier?

Again named for the configuration of the output stage. A single-ended output stage is so arranged that the output device amplifies the entire signal. There is no phase splitter and the output...
Forum: FAQ - Technology 6th January 2006, 11:21 PM
Replies: 0
Views: 5,323
Posted By FAQ Team
What does Bias mean?

Think of a triode valve. You have a cathode, an anode and a control grid. The potential on the control grid can control the flow of electrons through the valve, but only when it is negative with...
Forum: FAQ - Technology 6th January 2006, 11:20 PM
Replies: 0
Views: 3,748
Posted By FAQ Team
How is Bias applied in an amplifier?

Bias is applied by two different means. Firstly, it is possible to configure a dedicated negative supply from the amp's power unit and use this to set the grid negative. This is usually how bias is...
Forum: FAQ - Technology 6th January 2006, 11:19 PM
Replies: 0
Views: 5,237
Posted By FAQ Team
What is impedance; is it the same as resistance?

Resistance is a DC unit and Impedance is its AC counterpart which can vary with frequency.

(In the following formulae, we will use * to denote multiplication, / to denote division and + and -...
Forum: FAQ - Technology 6th January 2006, 11:16 PM
Replies: 0
Views: 3,394
Posted By FAQ Team
Written capacitance units

The Greek letter mu (like a u but with a tail starting the letter) is the correct symbol for micro which means millionth.

Mu isn't available on many keyboards so m is sometimes used instead. This...
Forum: FAQ - Test and Measurement 6th January 2006, 11:01 PM
Replies: 0
Views: 13,387
Posted By FAQ Team
How do I measure the power output of my amplifier?

How do I measure the power output of my amplifier?

The simplest set up needs, preferably a dual trace oscilloscope, signal generator and 8ohm load resistor. You can check at all audio frequencies...
Forum: FAQ - Test and Measurement 6th January 2006, 11:00 PM
Replies: 0
Views: 3,912
Posted By FAQ Team
Measuring the level of feedback in an amp

Measuring the level of feedback in an amp

First, measure the input sensitivity of the amplifier with no feedback.

This is the input level of signal needed to drive the amp to full output and...
Forum: FAQ - Test and Measurement 6th January 2006, 10:59 PM
Replies: 0
Views: 6,357
Posted By FAQ Team
How do I check the Bias and Plate Dissipation of my valve amp?

This is easy with a calculator if you have previously noted all the voltage measurements on WAD`s test sheet.

Notes follow or go straight to the end for the Calculation

All the WAD amps are...
Forum: FAQ - Test and Measurement 6th January 2006, 10:57 PM
Replies: 0
Views: 3,703
Posted By FAQ Team
What is X and Y and Lissajous on an Oscilloscope?

X and Y are the 2 axis on the scope screen or "graticule".

X is the horizontal axis, which represents the time the waveform is shown over.
Y is the vertical axis on which the wave height or...
Forum: FAQ - Test and Measurement 6th January 2006, 10:56 PM
Replies: 0
Views: 3,744
Posted By FAQ Team
I don't have an oscilloscope, what can I use instead?

Many tests will be unavailable to you without an Oscilloscope, although it is not essential to be in possession of one to build a fully working WAD amplifier kit, it will be useful if you wish to...
Forum: FAQ - Test and Measurement 6th January 2006, 10:54 PM
Replies: 0
Views: 3,744
Posted By FAQ Team
I don't have a signal generator, what can I use instead?

Consider a test CD disc. These have recorded sine wave test tones at stated frequencies and levels. The CD output available will be about .5v RMS that would fully drive the input of KEL84, KiT/KaT88...
Forum: FAQ - Upgrades and Tweaks 6th January 2006, 10:28 PM
Replies: 0
Views: 14,708
Posted By FAQ Team
Simple Mains Filter and Spike Suppressor

This little circuit can be added to the back of the IEC inlet inside your amplifier to help to suppress mains interference and spikes;

2 mains suppression capacitors; X class 0.047uF / 47nF...
Forum: FAQ - Upgrades and Tweaks 6th January 2006, 10:25 PM
Replies: 0
Views: 5,469
Posted By FAQ Team
Lowering feedback in KiT88 and KeL34

The circuit design of KiT/KaT88 & KeL34 are very similar. The feedback circuit is basically the same.

The 6AU6 cathode resistor and the amps feedback resistor are the same IE: R38 & R39 have a...
Forum: FAQ - Upgrades and Tweaks 6th January 2006, 10:22 PM
Replies: 0
Views: 5,241
Posted By FAQ Team
Lowering feedback in KIT34 KIT6550 KEL84

Feedback

Feedback improves the figures for noise, distortion, output impedance and bandwidth. In many ways it is a good, or even essential, part of an amplifier.

The designer will have designed...
Forum: FAQ - Upgrades and Tweaks 6th January 2006, 10:20 PM
Replies: 0
Views: 7,151
Posted By FAQ Team
PhonoII 3.18uS correction

PhonoII 3.18uS correction

As standard the PhonoII corrects for the 75uS, 318uS and 3180uS RIAA equalization time constants, in addition many good quality RIAA phono designs also correct for the...
Showing results 1 to 25 of 44

 
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