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This video is our own Vintage Audio Workshop production and is an introduction to the Heathkit audio valve pre-amplifiers models UMC-1 & USC-1 covering Phono EQ, Baxandall Tone Circuits and Filters.

We will follow up with more on this subject in our part 2 video covering pre-amplifiers. Hope you enjoy!

This video tutorial is for the Dansette HiFi Mk.1 Twin ECL82 Triode/Pentode PushPull Ultra-Linear, Valve Amplifier employing a Metal Rectifier.

Built in Britain in the 1950/60's period.

We will be coming back to this circuit again when explaining Basic Valve Amplifier Theory in thorough detail.

This video is for the Hacker GP42 record player amplifier (part 1) which is a two-stage Triode/Pentode Push Pull (NOT Ultra Linear) design, circa 1964, manufactured in Gt Britain by the Hacker Brothers.

These players were often considered to be technically the best of the bunch when compared to Dansette, Bush, Ferguson, Decca, Pye and other portable record players of the time.

This is an introduction to the GP42 circuit which uses Twin ECL86 Valves and an EZ80 Full Wave Rectifier. This amplifier produces over 8 Watts of music power with a freq response of 50 - 15Khz.

In part 2 of the Hacker GP42 video we will shoot a voltage check with an AVO meter testing in more than 15 points throughout the circuit.

This is a quick run through of the Williamson 1947 circuit.

Also included is a copy of the 20 page Wireless World Williamson Special edition from 1952, collecting various articles on this amplifier from 1947-1952.
Further Updates: We will come back to this circuit design in the future when we cover basic theory in much greater detail and will include this in our Interactive Online Quiz. Our Studio Technician will also have a lot to say about this unit as well as the mic pre-amp stage.

This is our video number 23 from the 30 produced in total which covered over 8 hours video time with audio repair technician Phil Moss.

Please help support what we do by subscribing to our youtube channel and make a donation via the paypal function at the top of the home page. This would help towards future productions. We’ll be returning to the Quad amplifiers in greater depth when we cover basic audio electronics theory in the near future

This is our proudest video to date covering the Quad II British Valve Amplifier dating from the 1950's.

We have done quite a thorough job here describing the circuit and essential work and observations to carry out before powering up after being in storage for some time.

Our next video will cover the Quad Control 22 Pre Amplifier which goes with this unit.

Further Updates: We will come back to this circuit design in the future when we cover basic theory in much greater detail and will include this in our Interactive Online Quiz. Our Studio Technician will also have a lot to say about this unit as well as the mic pre-amp stage.

Here we take a look at the circuit of the amplifier section of the Bush SRP31D Stereo Record Player.

Triode Pentode - Push Pull - Ultra Linear. Valve line up: ECL86 (x2), Metal Rectifier.

We'll take a further look at the SRP31C and SRP31D models when we cover Basic Theory in the near future.

Here we take a look at the British Dynatron Mazurka Stereo Record Player Amplifier circuit, circa 1960.

The TC18 Pre-amplifier employs the ECC83 Dual Triode and the LF18 Amplifier section uses twin ECL82 Triode Pentode valves in push pull. Rectifier valve EZ81

Here we take a look at the circuit of the amplifier section of the Bush SRP31C Stereo Record Player. Valve line up: ECL83 (x2), Metal Rectifier.

Here we take a look at the circuit of the amplifier section of the Pye Black Box record player. Valve line up: EZ41 - EL42 (x2) - ECC83.

This is an update to our previous Dansette Bermuda Mk.2 video which clarifies why it's called an AC/DC type in the user manual, although strictly speaking due to the record deck motor being used as an auto transformer the record player would not run on DC.

However the chassis is a live chassis type and users need to be aware of safety concerns. We'll cover these issues further when we upload the theory videos.

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Here we take a look at the circuit of the Leak Point One Power amplifier. Valve line up: pair of EF86s.

Here we take a look at the circuit of the Leak TL-10 Power amplifier. Valve line up: pair of KT61s - 6SN7 - EF86 - 5Z4G rectifier.

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This is a Shaftesbury Duofuzz Germanium diode Distortion Pedal circa late 60s/early 70s.

Overload of the Germanium Diode begins at 0.3 volts compared to silicon diodes at 0.7 volts which is why the company chose this method of design.

This box has a fantastic grungy 60s garage rock character and at a later date we'll do another video showing some audio examples. A holy grail distortion pedal for a lot of guitar players.

Here we go through the circuit of the AMC/2 Vintage microphone Pre-Amplifier employing the AC/SP3A Valve.

Also covers vintage and virtual earth audio mixing circuits.

Here we have our audio service technician taking you through a voltage amplifier.

The RCA 5AR4 circuit employs two 12AY7 double triode valves which have the military equivalent 6072A.

This is a detailed look at a 4 channel valve audio mixing unit, which uses EF86 screened pentode valves for the mic amp stage and an ECC83 valve for the radio and crystal pickup inputs.

Our service technician gives you a good look at the unit and takes you through the circuit diagram.

This is a quick tutorial with our service technician taking you through the circuit of the Mullard 5-10 Valve amplifier, a British vintage classic from the late 50s, early 60s.

This is a quick tutorial with our service technician taking you through the circuit of the Mullard 3-3 Valve amplifier, a British vintage classic from the late 50s, early 60s.

Here is our service technician taking you through the PX25 valve amplifier circuit.

This is a classic vintage British amplifier from the late 1940s with valves by Marconi.

This is a very simple circuit which is a single ended design using a single stage EL84 Pentode valve.

This is very common for a lot of gramophone units from the late 1950s to early 1960s.

The Dansette Major Deluxe 21, Deluxe Mark 2 & RG30/31 Models often have very poor quality mains isolating transformers. These should be upgraded with the modern type and also fused.

This is the most advanced amplifier circuit of the Dansette record player range using a pair of ECL86 valves on a printed circuit board in push pull mode , giving about 10 watts total music power.

This amp includes negative feedback and a passive tone circuit with separate bass and treble pots.

We will be covering both Dansette HiFi models again in the near future in much greater detail.

Our service technician takes you through the valve amplifier circuit diagram and explains the triode pentode of the ECL80 type valve.

This is a single valve dual stage amplifier (manufactured 25th November 1961) using a triode pentode ECL82 valve. There's a lot here to learn from our service technician who takes you through the circuit.

This is a very simple circuit which is an AC only design, very common for a lot of gramophone units from the late 1950s to early 1960s.

These units should be upgraded with mains isolating transformers for greater safety.