This is the amp’s wattage control. This technology was developed by Kevin O’Connor at London Power and is used under License Agreement.
Lower settings produce less wattage.
Higher settings produce more wattage.
Gain Mode Switch
The Drive works together with the power Scale control to keep the amps tone at any wattage. In other words cranked tone at any volume. When the Scale is set to maximum the power amp produces full wattage, any other Scale setting will produce less than full wattage. Scale set to minimum is the amps standby mode. The Drive control determines the amount of saturation and compression that the power amp produces. As the amp is Scaled down the Drive should also be turned down to keep the amps natural full volume tone. A good rule of thumb is: adjust the Drive and Scale controls together. In other words: if you adjust one, then adjust the other to dial in the best tone. Of coarse there are no right or wrong settings, dial these controls in to achieve the tone your looking for. Simply keep these points in mind:-High drive settings and low scale settings will produce a saturated/compressed tone.-Low drive settings and high scale settings will produce the cleanest tone.
The Cut switch works in conjunction with the Drive control. With the Cut ON (switch in the Up position) there are less highs and upper mids. To keep the tone more focused and the bottom tighter, keep the Cut Off (switch in the Down position) and the Drive dialed back.
Feedback Attenuation – controls the amount of negative feedback that is employed in the power amp. Negative feedback is a common guitar amplifier method to control the tightness and gain of the power amp. Too much negative feedback can cause a thin constricted sounding amp and too little can cause a bloated sounding amp. With the Fat set to minimum a great deal of negative feedback is employed, which keeps the power amp tight with less body and gain. With the Fat set to maximum the power amp is running open loop (no negative feedback), for maximum gain, body and wattage from the power amp.
AC input – Ultra switch – Foot switch jack - Valve select – Speaker output – Effects loop
Foot Switch Jack
Standard stereo ¼ inch connector for controlling effects loop and internal gain boost
Power and Tubes
The tube on the left is a EL84 and is enabled with the EL84 switch.
The two octal tube sockets can accommodate several tube types and are enabled by switches V-2 and V-3. The tube types that can be used are: 6V6, 6L6, 5881, 6CA7, EL34, and KT77.
Any combination of these tubes can be used with no re-biasing required, simply plug and play.
The EL84 and V-2 work together producing one half of the audio waveform, and V-3 works alone producing the other half of the waveform.
The example in the picture is a EL84 combined with a 6V6, and V-3 is using a EL34. This is one of my favorite tube combinations to use in this amplifier. The output signal is very balanced and it turns the 20 watt into a 30 watt.
Speaker Output Section
The impedance selector is labeled 1- 2 -3 because any setting can be used with a 4ohm 8ohm or 16ohm speaker cabinet.
Use the setting that you like the best. When using different output tube combinations, listen to the different impedance settings to see what one you like best.
This effects loop is a 6SN7 tube driven parallel type with variable send and receive levels that will accommodate both pedals and rack gear.
This loop is based on a design by Kevin O’Connor of London Power, I’ve been using it for many years now and find it to be about the best there is.
All prices are in USD and do not include shipping or taxes. There is an approximate 6 month backlog at this time. A $1500 deposit is required to get on the amplifier build list, the balance is then due when the amplifier is ready to ship.
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