Attenuator comparison grid
A traveling-wave tube TWT , pronounced "twit" [1] or traveling-wave tube amplifier TWTA , pronounced "tweeta" is a specialized vacuum tube that is used in electronics to amplify radio frequency RF signals in the microwave range. A major advantage of the TWT over some other microwave tubes is its ability to amplify a wide range of frequencies i. The TWT is an elongated vacuum tube with an electron gun a heated cathode that emits electrons at one end. A voltage applied across the cathode and anode accelerates the electrons towards the far end of the tube, and an external magnetic field around the tube focuses the electrons into a beam.
We are searching data for your request:
Attenuator comparison grid
Wait the end of the search in all databases.
Upon completion, a link will appear to access the found materials.
Content:
Traveling-wave tube
Keep in mind that Marshall made a lot of part substitutions and "upgrades" to these long production run amps so many parts, especially capacitors' component values can differ from these schematics. Also be advised that Marshall model numbers have nothing to do with the year the amp was introduced. The Cathode Follower.
The Attenuator Circuit. Tweaking the Overdrive and Tone. Classic Marshall Amp Cheat Sheet. The Marshall Plexi guitar amplifier was an evolution of their very successful Fender 5F6-A Bassman copy, the JTM45 but with just two preamp gain stages it can't really be considered a "high gain" amplifier. The guitar signal enters at left at the I "Bright" Channel input jack.
The signal is amplified by the V1B preamp stage then flows through the Volume I pot to the V2A preamp then directly through DC coupling no coupling cap to the V2B cathode follower which supplies the tone stack with a low impedance signal to keep the tone stack from loading down the guitar signal. After the Tone Stack the signal goes into the Phase Inverter.
The Phase Inverter creates two mirror image signals that are degrees out of phase to feed to the Power Tubes. The "Plexi" came with two distinctly voiced channels each with two inputs.
These two channels parallel one another and meet up at the V2A second preamp gain stage. A common mod with these amps was to change the channels from parallel to series so the guitar signal went through both V1A and V1B before hitting the third V2A gain stage.
These modded amps are where Marshall got the idea for the Master Volume preamp described below. Each channel's High and Low jacks function just like the Fender standard four input circuit.
The Low inputs have their guitar signal cut in half by forming a voltage divider with the two 68k Grid Stopper resistors. The High jack's input impedance is 1 megaohm while the Low jack's is 68k.
The two very different input impedances can color the tone from the guitar's pickups so you should always try both the High and Low inputs to hear which sounds better with the guitar you're using. Humbuckers and hot pickups often sound better through the Low jacks.
Both channels parallel one another and both go through two preamp gain stages before hitting the no-gain V2B cathode follower, Tone Stack and Phase Inverter. Its small. Because of this design the Bright or "Lead" Channel responds extremely well to boost and drive pedals. The Bright Channel's very small. Its very large uF bypass cap boosts all guitar and bass frequencies for a rich full bodied tone.
The Normal Channel's ten times larger. The primary purpose of the Cathode Follower is to prevent the tone stack from loading down the high impedance guitar signal coming off V2A's plate. The Cathode Follower supplies a low impedance signal to the tone stack to keep the tone controls from affecting the amp's output volume too much.
Amp users do not want the volume to drop when they roll off some bass. But the Cathode Follower does much more than feed the tone stack. It is the first triode to go into overdrive and its interaction with the upstream gain stage adds a unique overdrive effect that limits clipping of both the positive and negative signal lobes. Introduced in , the "Master Volume Lead" series amps were Marshall's first true high gain amplifiers. They cascaded the Plexi's bright channel into the normal channel, added a pre-phase inverter master volume and cold biased "cold clipper" gain stage and tweaked the resulting circuit for an aggressive but sweet overdrive tone.
The was a watt head and the was a watt 2x12 combo. The was a 50 watt head and the was a 50 watt 2x12 combo. The change from " Master Volume" to JCM was mostly cosmetic and made for legal purposes at the end of the Rose-Morris distribution deal.
The guitar signal enters at far left at the High "Lead" Channel input jack. The signal is amplified by the V1B preamp stage then flows through the Preamp Volume pot to the V1A cold biased "cold clipper" gain stage which generates asymmetric clipping. The signal then flows through the V2A preamp then directly through DC coupling no coupling cap to the V2B cathode follower which supplies the tone stack with a low impedance signal to keep the tone stack from loading down the guitar signal.
The guitar signal is amplified by V1B one 12AX7 triode which has a cool bias from its 2. The signal then flows through the Low Channel input jack where the Low Channel input would start to the Preamp Volume pot. The pot's output flows to the V1A "cold clipper" gain stage. The cold clipper is very important to these Marshall high gain amps' smooth overdrive tone.
For minimum distortion a tube should be biased halfway between cutoff when all electron flow is stopped and saturation when electron flow is maxed out. The cold clipper's very large 10k cathode resistor sets a cold bias that leaves little room on the shutoff side so the input signal can easily be clipped when the input signal's negative lobe on the grid reduces electron flow through the tube and electron flow is shutdown completely.
This clipping is asymmetric because there's plenty of room on the saturation side of the bias point. Asymmetric clipping generates mostly sweet sounding 2nd harmonic distortion. The positive, saturation side of the guitar signal lobe isn't distorted and carries the original musical content. The JMC uses a cold clipper stage with an unbypassed 10k cathode resistor. Soldano liked to use a more aggressive 39k cathode resistor for an even colder cold clipper.
Note the following gain stage is biased warm with an ohm cathode resistor. Since a guitar signal's phase if flipped after each gain stage putting a warm biased stage after the Cold Clipper helps keep the distortion asymmetrical by keeping the undistorted lobe clean. With asymmetric clipping one signal lobe carries the clean signal while the clipped lobe carries the distortion.
The cold clipper generates early, relatively low volume, smooth, musical preamp distortion that can be controlled by the Master Volume for high gain tone at lower volume than their earlier non-master volume amps.
Without the cold clipper stage the preamp would stay too clean and the amp would have to rely on distortion from the power amp making the Master Volume less useable. As the cold clipper distortion comes on it blends seamlessly into the downstream phase inverter and power tube distortion into a cacophony of delicious high gain tone.
The cold clipper's asymmetric output signal can be clipped in later gain stages at high volume levels but note the gain stage following the Cold Clipper is biased warm with an ohm cathode resistor V2A. Because a guitar signal's phase if flipped after each gain stage, putting a warm biased stage after the Cold Clipper helps keep the distortion asymmetric by keeping the guitar signal's undistorted lobe clean.
The warm bias leaves more room on the cutoff side to reduce clipping to the undistorted signal lobe. The cold clipper is also a relatively low gain stage compared to one with a fully bypassed cathode. Soldano used the cold clipper cathode resistor value to trim gain to make his preamp work as desired.
The higher the resistance value the lower the gain. That's one of the reasons Soldano used such a very large 39k cathode resistor in his cold clipper. The operating point intersection of green lines is very low in the curvy end of the grid voltage lines so the negative half of the guitar audio signal is distorted even before clipping occurs. Signal clipping will occur with the negative lobe of the signal voltage much earlier than the positive lobe which will lead to early sweet sounding asymmetric cutoff clipping.
For information on how these lines were charted see How to Draw Load Lines. This is a cool little mod that allows you to select a 10k Marshall Cold Clipper, Soldano 39k Clipper or aggressive grid clipping in the following stage. You can also put a cathode bypass cap across the 5k resistor to generate extreme grid clipping in the following stage with the switch in the "Grid Clip 4.
You can then choose between two levels of cold cutoff clipping and harsh and aggressive grid clipping. The extra gain from the bypass cap will cause the following stage to grid clip at very low signal levels for a very different overdrive tone.
I recommend you temporarily alligator clip the cap into place to try it before warming the solder gun. You normally don't want to put a bypass cap on the 10k or 39k cathode resistor because the extra signal swing generated by the bypass cap will distort too early and too severely and sound "fizzy".
In the middle position only the middle resistor is connected. In the up and down position a resistor is in parallel with the center resistor so total resistance is their parallel resistance. The voltage across the switch is only 2 or 3 volts so its rating is unimportant. After the first preamp stage the guitar signal flows into an attenuating voltage divider. Attenuating voltage dividers are an important part of high gain amp tone.
Signal attenuating voltage dividers are present in all high gain tube amps to control the level of overdrive and saturation. The Attenuator resistor is bypassed with a pF Bright cap also called a Treble Peaker to allow high frequencies to go around the voltage divider to boost high frequencies.
If you remove or bypass the upper resistor in a voltage divider then there is no voltage divider. Removing this Treble Peaker cap is a common mod for overly bright amps to cut ice pick highs and reduce shrillness.
There are four other attenuating voltage dividers in the OD and Clean Channels that moderate gain to keep things under control at high gain settings. A high impedance guitar signal is "thin" with little current to backup the voltage swing whereas a low impedance signal is "thick" with lots of current to backup the voltage. The Cathode Follower supplies a low impedance "thick" signal to the tone stack to keep the tone controls from affecting the amp's output volume too much.
It's a passive tone control that cannot boost frequencies, only remove them from the guitar signal. It's a low impedance circuit that places a heavy load on the guitar signal so the V4A Tone Stack Buffer Cathode Follower acts as a buffer between the low impedance tone stack and the high impedance signal from the preamp.
Without the cathode follower the tone controls would raise and lower the overall signal volume even more than they already do. The guitar signal leaves the tone stack through the treble pot's wiper and flows to the Master Volume pot.
The pre master volume controls the signal level flowing into the phase inverter and controls the distortion level of both the phase inverter and the power tubes. The 12AX7 phase inverter gets hit with a hot signal from the preamp and being able to tame that signal before it hits the inverter's grid can help prevent unwanted blocking distortion at extreme volume levels.
The down side of having the master volume on the input side of the phase inverter is you don't have the phase inverter's gain to create distortion before the master volume. From there it follows the same path as the High Channel described above. With one less preamp gain stage the Normal Channel has more clean headroom and tends to be more pedal friendly. A Negative Feedback tap of 4, 8 or 16 ohms can be used instead of the 4 ohm tap shown in the power amp schematic below.
The Presence Pot was changed to 22k and a parallel 4. In the new circuit shown above the Presence Cap blocks DC and keeps it off the pot. The 4. In the old circuit if the pot fails the amplifier will completely cease to function. The simpler 50 watt power amp is shown below but the watt power amp used in the Super Lead Plexi and and Master Volume amps simply had two additional power tubes in parallel with the two shown below.
We apologize for the inconvenience...
Where we are Find your distributor Contact Us. Receiver sensitivity testing. An important factor of GPS testing is that of receiver sensitivity. The main areas of test are acquisition sensitivity and tracking sensitivity. Typically, the RF power level received by an antenna on the ground will be between dBm and dBm depending on environmental factors.
Difference between DC Voltmeter and AC Voltmeter
OTDRs can take multiple samples of the trace and average the results. The two traces pictured here were captured from the same cable plant with all of the same settings except for the number of averages. The trace on the left is only one test, while the one on the right is averaged from pulses. Notice the difference in the distance that the signal travels before it the noise level becomes significant. On the right, the noise is very low all the way to the end of the cable at 5. If you are trying to get longer distances with high resolution, using more averages with a short test pulse will usually be the best choice. It will simply take longer to acquire each trace. It can verify splice loss, measure length and find faults.
Receiver sensitivity testing
Profile The mission Conflict Minerals Policy. Modular Adapters to DB Modular couplers. Termination Tools Cabling Analysers. Category 5, 5e, 6, 6a and 7 Cable Standards C ategory 5 Cable.
The 5 Best Noise Reduction Earmuffs Review
Loyalty Points. What are points worth? Points are worth a 1p discount for every point you redeem. How many points will I earn when I shop? We display the number of points available for a product on the product's page on our website. Normally we'll give you one point for every pound you spend, but watch out for double and triple points deals for even more savings!
How can you avoid preamp clipping?
Xueyang Bao, Colleen A. Dalton, Ge Jin, James B. The EarthScope USArray provides an opportunity to obtain detailed images of the continental upper mantle at an unprecedented scale. The majority of mantle models derived from USArray data to date contain spatial variations in seismic-wave speed; however, in many cases these data sets do not by themselves allow a non-unique interpretation. Joint interpretation of seismic attenuation and velocity models can improve upon the interpretations based only on velocity and provide important constraints on the temperature, composition, melt content, and volatile content of the mantle. The surface wave amplitudes that constrain upper-mantle attenuation are sensitive to factors in addition to attenuation, including the earthquake source excitation, focusing and defocusing by elastic structure, and local site amplification.
Either your web browser doesn't support Javascript or it is currently turned off. In the latter case, please turn on Javascript support in your web browser and reload this page. Read article at publisher's site DOI :
Read times. Pages: [ 1 ] 2 Go Down. Transcendent Grounded Grid Preamp Questions. I'll listen to it before changing things, but I have a couple of questions if you don't mind: 1.
Metrics details. Hydraulic pumps are a positive displacement pump whose working principle causes inherent output flow pulsation. Flow pulsation produces pressure pulsation when encountering liquid resistance. Pressure pulsation spreads in the pipeline and causes vibration, noise, damage, and even pipeline rupture and major safety accidents. With the development of airborne hydraulic systems with high pressure, power, and flow rate, the hazards of vibration and noise caused by pressure pulsation are also amplified, severely restricting the application and development of hydraulic systems. In this review paper, the mechanism, harm, and suppression method of pressure pulsation in hydraulic systems are analyzed.
Keep in mind that Marshall made a lot of part substitutions and "upgrades" to these long production run amps so many parts, especially capacitors' component values can differ from these schematics. Also be advised that Marshall model numbers have nothing to do with the year the amp was introduced. The Cathode Follower. The Attenuator Circuit.
There are no comments yet.