Power Iso Crack Google Drive
Ariano Waiker
The Power Drive is my new and improved take on my PowerBoost which was based around the old Colorsound Power Boost. Its a boost, its an overdrive, it is dirty, it is raw, it is loud and it is all POWER! I've added a charge pump to get it pretty close to the original 18v with a 9v supply and modified the EQs so you can get it nice and crispy with really solid low undertones without the typical compressed sound of other similar effects. This newer version also has a voltage control so you can run it anywhere from the full 17v for high head room full throttle overdrive or all the way down to 3v for that killer sputtery gated old school sound!!!
If you are looking for any cliche adjectives like "transparent" or "clean" this is not for you. If you want to sound like 10 dirty, raw amps on 11 then check this mother out and start playing with POWER!!!
"I am absolutely BLOWN away by the Power Drive. The dynamic and pick sensitivity of the Power Drive was totally unexpected, and knocking down the voltage creates the coolest freakin fuzz!!" -Mariful A. (Toronto, Canada)
PowerDrive has generated more email than anything else on this web site. At first the email was mostly negative, document.write(""); document.write(""); often blasting me for corrupting their tube designs with "sand". I even got one suggesting that I change my name to Transistorlab! After a few adventurous souls actually built their own PowerDrive circuits, listened to them, and reported their results of some of the forums, the email began to change. Now it mostly reads like " I need a PowerDrive circuit to drive a XXXX tube from a YYYY tube, can you design me one". I get 2 or 3 of these a week. Some have offered to pay me for the design. This would be great if I didn't already have a full time engineering job that demands 50 hours a week. There is no way that I have time to do this (especially with all the other stuff that is going on), so I am doing the next best thing. I created a new page that will help you design your own PowerDrive. It is on this web site here.
It is not unusual for music to have transient peaks 20 db above the average power level. Transients 10 to 15 db above the average power level are fairly common. This means that if your average listening level is 1 watt, your amplifier will be called upon to produce up to 100 watts on peaks. If you only have a 10 watt amp, it will clip the signal on the transient peak. If this is all that happens you may not even notice it. However, this is not all that usually happens. Often there is some distortion that lingers after the transient has passed. This distortion can originate from several sources.
If an amplifier uses a large amount of global feedback, the amplifier may have a finite recovery time for the loop dynamics to settle out after a temporary overload has passed. What is wrong with a lot of feedback? Simply put, at the instant an amp clips its gain drops toward zero (an increasing input voltage produces no more output voltage) and the feedback attempts to correct this situation by essentially cranking up the gain thus driving the amp further into clipping. There is a time delay for the system to recover, during which the output does not resemble the input. The greater the amount of feedback the greater the problem. And this is with a purely resistive load. Drive a speaker and the feedback network could be trying to correct for things external to the amp. Often distortion of this type produces higher order harmonics, intermodulation products, and non harmonically related signals that tend to sound terrible. This can occur with a solid state or a vacuum tube amplifier. Most modern solid state amplifiers tend to use a lot of global feedback, so they tend to sound gross when operated into clipping. The current trend is to simply build a bigger amp in an attempt to avoid clipping altogether. Most vacuum tube amplifiers use limited amounts of (or zero) global feedback, which tends to reduce this type of distortion. There is however a type of overload that is usually particular to vacuum tube amplifiers.
A problem exists in all vacuum tube power amplifiers when the input signal reaches the point where the driver tube attempts to drive the grid of the output tube positive. You say that your amp operates in A1 and that won't happen. Wrong! Unless the driver is carefully designed to clip before this can happen, it will. It has been my experience that clipping is less obvious sounding if the output stage clips first, and the amplifier is set up so that the clipping is symmetrical (equal clipping on the top and bottom of a sine wave). Refer to the typical interstage circuit below to understand this phenomenon:
For this discussion, assume that the plate voltage on the driver tube is 100 volts, the output tube grid is 0 volts, and the output tube cathode is 10 volts (numbers chosen for easy arithmetic). Assume that the driver plate load resistor is 50K and the output tubes grid resistor is 200K and the coupling cap is .1uF. As long as the driver tube's output signal is below 20 volts peak to peak, everything works as expected. The coupling cap is charged to 100 volts, and no current is flowing in or out of the output tubes grid. If a large enough positive going transient appears at the input of the amp, the driver tube will conduct heavily generating a negative going pulse at the driver plate. This will be coupled into the grid of the output tube driving it toward (and possibly into) cutoff. The output tube may go into a non linear region, or be cutoff entirely for an instant. This will cause temporary distortion due to clipping. Since the output tube's grid is driven negatively, no grid current flows, and equilibrium is maintained.
A large enough negatively going transient at the amp input is a different story however. This transient causes the plate voltage to rise in the driver tube. This rise is coupled to the grid of the output tube. As long as the positive going pulse at the output tubes grid does not overcome the 10 volts of bias, no grid current flows, and equilibrium is maintained. If the positive pulse does exceed the 10 volts of bias, the grid of the output tube goes positive with respect to its cathode. As the grid goes positive it draws current. The amount of current varies depending on the type of tube and the magnitude of the positive voltage. It is possible for some tubes to draw hundreds of milliamps of grid current with 50 volts of positive voltage on the grid. The grid - cathode interface acts like a vacuum tube diode, capable of clamping the grid voltage to a few volts more positive than the cathode. Most tubes will actually begin to draw some grid current when the grid is still negative by a volt or two. If the driver can not source any current into the grid of the output tube, distortion will occur as the grid approaches zero volts. It gets worse!
Consider an extreme case. A large negative going transient hits the input of the amp causing the driver tube to be cutoff. The plate voltage rises quickly from its quiescent value of 100 volts. The grid voltage of the output tube begins rising but as it tries to go above the cathode voltage (10 volts) it is quickly clamped at a few volts positive. At this instant all of the current that was flowing into the plate of the driver tube is now flowing into the coupling cap. Since the other end of the coupling cap is effectively clamped at say 15 volts, the cap is being discharged. The time constant of this discharging is determined by the plate load resistor, and the coupling capacitor value. If the transient lasts long enough, the capacitor will no longer be charged to 100 volts. We will assume that it now contains 99 volts. Now if the transient is removed, the amp attempts to recover. The driver's plate voltage returns to 100 volts, but some of the charge in the coupling cap was lost, so the output tube's grid is now at -1 volt. If there are no more transients the capacitor will recharge through the output tubes grid resistor. But now the time constant to recharge the coupling cap is determined by the driver's plate load resistor PLUS the output tubes grid resistor and the coupling caps value. In this example the recharging time constant is five times longer than the discharging time. This is typical. The amp may distort a normal signal during this time. The bias will be shifted toward cutoff during the recovery time. This may only cause distortion on large signals in a SE amp, but could result in crossover distortion in a push pull amp. If the transients come often enough the effect will be cumulative since the coupling capacitor never has the time to fully recharge. These "extreme cases" happen all the time in a guitar amp. The resulting blocking distortion can cause the amp to actually block a signal after an extreme overload. This is known as "farting out" to a guitar player. Blocking distortion is usually accentuated by global feedback.
How can this be fixed. The obvious solution is to reduce the value of the grid resistor in an attempt to equalize the two time constant. This also lowers the load impedance seen by the driver tube, reducing its gain and increases its distortion. A not so obvious solution is to increase (or install) the grid stopper in the output stage. This limits the current that could be drawn by the output tube. This will reduce the high frequency response particularly if the output tube is a triode. It usually helps to use the smallest coupling cap to give the required low frequency response. These tricks can help in mild cases, but what we really need is a driver topology that can feed the output tube's grid more current than it can eat!
This requires a driver with a low output impedance. Ever since the drawbacks of RC coupling were documented by Crowhurst over 50 years ago vacuum tube designers have been looking for a better driver circuit. The two most popular circuits are the cathode follower and the interstage transformer. A good interstage transformer is hard to manufacture due to the high impedances involved and the need for wide bandwidth without phase or amplitude distortion. Good ones do exist but they are expensive. Cathode followers have always invoked a "something is missing from the sound" experience. I offer another alternative, PowerDrive.
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