As you turn up the volume on traditiional amps, the louder you get, the more the notes bloom. This slightly delayed, blossom response is caused by power supply sag. But excessively loud music is harmful to everyone's ears, and many attempts are being made to achieve that "cranked up to 10" amp tone at low volumes.

But not one of these methods addresses the basic power supply design. As the wattage is turned down using any of these methods, either the power supply becomes stiffer or the power tubes and output transformer are placed in risk of failure.

Specifically, these methods include:

Dummy Load (a.k.a. attenuator)
Dummy loads are devices that go between the output of your amplifier and your speaker. The purpose of a dummy load is to absorb the amount of power you desire, and to send any remaining power to the speaker. Your amp is still making the same amount of power--it's just that some of it gets diverted to a 'dummy load' instead of being sent straight to your speaker.

While dummy loads work great on paper, they disrupt the coupling between the output tubes, output transformer and the speaker. As less and less power goes to the speaker, the worse and worse your amp will sound.

Amps aren't like the mail where you put your packet of power into the speaker cord and off it goes. The output tubes, the output transformer, the speaker cord, the speakers and speaker cabinet are all closely linked as a system, not just a chain of events. If you break up the system and insert another device, something bad happens sonically.

Finally, attenuators are notoriously hard on power tubes and output transformers often causing warranty nightmares.

Master Volume
 Master volumes control the level of the signal being sent to the power amp after it has passed through the preamp. This technique allows guitarists to overdrive or distort the preamp at low volumes, but the only way to get power amp distortion is to turn the volume all the way up.

Preamp distortion is key to heavy metal music, but preamp distortion alone is either an "on" or "off" experience. It does not provide the dynamic touch response that power amp distortion provides. In fact, some heavy metal players dislike power amp "flub," preferring the tightest power supply money can buy. Most players, however, prefer a delicate (or not so delicate) mix of both.

Variable Transformers (a.k.a. Variac)
 A variable transformer is a device that you use between the wall and your amplifier. You plug the variable transformer into the wall socket, and then plug your amp's power cord into the variable transformer.

A variable transformer adjusts the amount of voltage your amplifier receives. Two reasons for wanting to control this voltage include:

Three problems with variable transformers include:

  • The more you turn down the voltage, the worse your amp will sound. This problem can be solved by a competent technician who can add a second power transformer to your amp to supply your heaters with enough voltage. The heater transformer is then plugged into the normal wall voltage, and the remainder of your amp is plugged into the variable transformer. While this approach is certainly Rube Goldberg, it does work.

  • The timbre and touch responsiveness of your amp changes as you change voltage settings. Specifically, your amp's power supply will sag less and less as you turn down the voltage. Your amp will feel increasingly stiff and bright, completely obliterating the reason for using the variable transformer in the first place--to enjoy 'cranked up to 10' tone at lower volumes.

  • You can't plug and play; instead you are constantly adjusting and readjusting. This is because you cannot set a variable transformer to a specific output voltage; you can only set it to a ratio of input to output voltage. When the wall voltage changes (which it does all the time), you need to sit down with your variable transformer and a volt meter to readjust the voltage to the output you want.

Internal Variable Transformer
 An internal variable transformer (or power scaling) is automatic. However, it does come with all of the other problems associated with variable transformers, and does not allow your customers to control Sag. More importantly, power scaling puts up to 400 volts or more on the potentionometer.

Although some potentionometers are rated for 400 volts or more, the Sag Circuit eloquently manages voltages and heat, never putting more than 40 volts DC on a potentiometer, even at 100 watts.



Maven Peal Instruments, Inc.
P.O. Box 71, Strafford, VT 05072
phone: 802-765-4607
email: dave@mavenpeal.com

Copyright © Maven Peal Instruments, Inc. 2000-2008
Maven Peal¨ is a registered tradename owned by
Maven Peal¨ Instruments, Incorporated.




dummy load
(attenuator)		 master volume variable
trans-
formers		 Maven Peal
Sag Circuit
Wattage control yes no yes yes
Power amp
distortion at
low volumes		 yes no yes yes
Power amp
distortion
control		 no no no yes
Eliminates
power supply
hum		 no no no yes
Impervious to
varying wall
voltages		 no no no yes
Easy on
power tubes		 no yes yes yes
Keeps amp to
speaker signal
path intact		 no no yes yes
Removes
high-end
fizz		 no no no yes

    The Maven Peal Sag Circuit
    The Maven Peal Sag Circuit is a DC regulator, meaning that it comes after the power transformer, rectifier or diodes and filter capacitors that comprise a traditional power supply. The Sag Circuit affects the entire amplifier, eloquently and efficiently managing heat like no other power supply can.

    The Wattage knob doesn't just give your customers control over the actual number of watts the amp is producing (allowing them to adjust the actual headroom), it also allows them to fine-tune the mix between the level of power amp distortion and the level of speaker distortion.

    The Sag know allows your customers to control voltage supply sag with the turn of a knob, from 0% to 25% with tube amplifiers, and up to 50% with transistor amplifiers. With the Sag knob, your customers can dial in the tightest, cleanest most sparkliing tone available from any amp (0% sag) up to the most touch responsive, dynamic tone available, without getting "flubby."

    The Sag Circuit is DEAD QUIET. All other approaches cannot eliminate power supply hum, because these approaches are all happening outside the power supply.

    And for the first time in a long time, changing guitars and tubes really makes a difference. Your customers will be able to change power tube flavors with the flip of a switch or touch o footpedal.

    No other approach gives you the noise free control over your power supply like the Maven Peal Sag Circuit. No other amp can give your customers authentic control over power amp distortion like Maven Peal.

    Additional Player Benefits
    Maven Peal's patented design (patent numbers 5,635,872 and 5,909,145) also creates an impressive list of additional player benefits:

    • No power conditioner required--the Sag Circuit removes all wall voltage noise by including the highest quality power build-in conditioner
    • Zero power supply hum (essential for recording)
    • Absolute freedom from wall voltage variations

    For more information, check out about Maven Peal.