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FAQs

Most of the questions that have been asked thus far are from guitar players who have been consulted during the design process and pre-order customers:

 

Where can I find prices?

Please click here

 

Will there be an effects loop?

There is.  It is common to both channels and has a High/Low sensitivity switch to best match the signal level with effects pedals or line level processing.

 

Why only 20 watts?

Much of the 'magic' of guitar valve amplifiers happens when the power stage is driving at or near its limits, and beyond.  This is true of our amplifiers too.  20 watts doesn't sound very powerful but it is an ideal output power to get the most from a valve amplifier without being unpleasantly or unusably loud.  There's also a common misconception that power equates to loudness in a linear manner - it does not.  A 20 watt amplifier is generally perceived to the human ear to be approximately 65% of the loudness of a 100 watt amplifier due to the more logarithmic nature of the human ear's dynamic range.

 

What's the power output exactly?

There are a number of methods to measure the power output from power amplifiers.  For reference purposes, it is often measured using a resistive load matching the nominal minimum impedance (eg. 8 ohms) and a sine wave is applied and increased to the onset of amplifier clipping.  With this method, the amplifier achieves 20 Watts continuous average power **.  Guitar amplifiers are often used well into power amplifier overdrive (distortion).  The resulting output substantially deviates from a sine wave used in bench testing, changing the crest factor of the output signal.  In this situation, output power can exceed 30 Watts continuous average power **.

(** Note: Continuous average power is often referred to as "RMS Power" however the term is technically incorrect.)

 

What speakers can I use with the Dexter Head?

Loudspeaker loads of 4, 8 or 16 Ohms may be connected and the amplifier must be set to the correct impedance load setting for correct operation.  It is recommended that the power handling specification of any loudspeaker, or combination of, should be a minimum 30 Watts continuous average power.  Of course, we recommend using a FastBack 212 (or 2) for optimal tone.

 

What are the alternative modes you've talked about?

As well as the use of channels A and B as switched independent channels, there is the ability to switch the preamplifier stages to 'Psycho' and 'Schizoid' modes.  In 'Psycho' mode, the 2 channels work in parallel enabling them to be mixed.  In 'Schizoid' mode, Channel A is routed to the input of Channel B, ie. the channels are in series.  This allows for tone controls before and after preamplifier overdrive, providing more tonal flexibility and the option to create different levels of boost for clean, rhythm and lead settings.

 

Where's the standby switch?

The amplifier has no standby switch.  There is some confusion over whether there are any benefits associated with standby modes.  This stems from misinterpretation of manufacturer's documentation in the early days of valve amplifier development.  Very high power transmitting valves can be damaged when HT voltages are applied to the anode whilst the cathode is cold.  It was the manufacturer's advice, and thus common accepted practice to implement circuits permitting cathode heating to a specified temperature before applying HT voltages.  This is not so with the types of valves used for audio amplification purposes but it seems that many early guitar amplifier manufacturers read this and assumed that it applied to all valves.

Dexter Amplifiers warm up and pass signal in only 15-20 seconds so simply powering off when not in use for short periods is of little detriment.

 

What's the speaker in the combo/FastBack 212?

They are custom designed, exclusive to Thornton Amplifiers.  A choice of Alnico and Ceramic motor units is available (one of each works fantastically in a FastBack 212).  Loudspeaker driver design is absolutely critical to achieving the desired results for any audio application - not just guitar.  An immense amount of effort has been focussed on this critical component, as with every other component.  For more information, please look HERE.