Below we have given an insight into Valve Amplifier Push-Pull Output Stage Operation. The guitar valve amplifier Push-Pull Output Stage is used in circuit design when output power, more than about 15W, are required. This arrangement allows the valves to be operated in Class AB, which is considerably more efficient than Class A (up to 80% compared with up to 50% respectively) reducing the amount of input power that is wasted by the circuit and released as heat in power valves. The hotter the valves run also reduces reliability.
Not only this, but Class AB also allows us to operate the valves at much higher anode voltages and the load line can actually go beyond the maximum power dissipation curve. In this way the peak power level can actually exceed the combined maximum anode dissipation power of the two valves!
Balanced Push Pull Amplifier Circuit
A perfectly balanced push-pull stage will cancel all even harmonic distortion and sum odd harmonic distortion generated within the power stage. However, guitar amps rarely use matched valves and usually have a less-than-perfect phase inverter. (Even if the phase inverter is perfectly balanced it will inevitably go out of balance when the power stage is overdriven.) This is desirable for the retention of even order harmonics, providing distortion with both warmth and ‘growl’.
An output transformer designed for Push-Pull Output Stage operation has a centre tap. The HT is applied to the centre tap and either end of the primary winding is connected to the anode of a power valve. In this way, current flows in opposite directions through the output transformer. If these currents are equal they will cancel out and this is why push-pull output transformers can be made much smaller than single ended ones with the same power rating- there is (almost) no standing current in the transformer so no air gap and less iron is required.
The Push-Pull Output Stage valves are driven with identical but out-of-phase grid signals. When one grid goes positive, the other goes negative. When one valves conducts more, the other conducts less: one pushes, the other pulls. The output signal developed in the transformer is the difference between the two AC currents.
Buy Guitar Amplifier Valves and Tubes
We have a full range of replacement guitar amplifier valves and tubes including single valves, matched sets and complete guitar amplifier re-valve kits available for the most popular amplifier types. These can be purchased by using the following links:
Read our Guitar Amplifier Technology Pages
- Guitar Amplifiers Explained – All Types & Makes
- Valve Amplifier Single Ended Output Stage Explained
- Valve Guitar Amplifier – Output Tubes Explained
- Valve Guitar Amplifier – Pre-Amplifier Tube Operation Explained
- Valve Guitar Amplifier – Technology Explained
- Valve Guitar Amplifier – Tube Amp Basics Explained
- Valve Guitar Amplifier – Tube Maintenance and Care
- Valve Guitar Amplifier – Tube Operation Explained
Also See These Product Listings
- Makes of Guitar Effect Pedals (All the makes like Boss, Dod, EHX etc)
- Types of Guitar Effect Pedal (Overdrive, Fuzz, Delay, Chorus and many more)
- Buy Boutique Guitar Effect Pedals (Custom Made Pedals as used by Famous Guitar Players)
- Makes of Guitar Amplifier (Marshall, Fender, Orange and many more)
- Types of Guitar Amp (Valve, Head, Combo, Solid State, Acoustic etc)
- Buy Boutique Guitar Amplifiers (Custom Made Guitar Amps)
- Buy Guitar Amp Speaker Cabinets
- Replacement Guitar Amp Valves (Single, Matched, Full Kits)
- Guitar Amp Valves Matched Sets (Pairs, Quads, Sextets – Tested and Matched)
- Full Guitar Amp Re-Valve Kits (Change All the Valves)
- Best Deals on Musical Instruments
Push Pull Valve Amp Example Circuit Diagram
About the YUMA GOLD Website
The YUMAGOLD website has been as a one stop shop for your guitar and audio gear. Our unique review system collects prices from across the web and displays them in a list. Review the SAVE button in the top menu for examples of current savings.These are chosen as they have very strict consumer controls to protect the buyer. This web site is constantly expanding and new products are being added daily.
Join the Mailing List
Join the mailing list using the link below to receive weekly emails showing the latest deals that are available online with high quality musical instrument gear with up to 50% off.
If you would like to advertise your products on our site let us know by using the contact form in the top navigation menu.