Stage PreAmp Made
April 27th, 2009
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Stage PreAmp Made
My tube amp is making sound with the speaker plugged in, but the sound is not the speaker.?
I bought a vintage Stromberg Carlson Signet 33 tube P.A. head at a local antique shop. All the tubes seem to be in good condition and every thing turns on fine. Everything seems to be in decent shape, even the point to point wiring. I ran my iPod through the phono jack that bypasses the preamp stage, and I had a 6 ohm speaker plugged in(that was all fine and dandy, but I might try my guitar speaker-it's 8 ohms and it actually has an 8 ohm spot). I turned it on and waited about 1 minute for the tubes to get nice and warm, and I turned on the iPod close to full volume and the phono volume was at 12 o'clock. To my surprise, the speaker made no noise but a small sound came from the amp. IT WAS THE MUSIC. The amp itself is the only thing that will play the sound. I opened it up to make sure there was no speaker on the inside and there wasn't. Can anyone tell me 1. What is going on? and 2. Do you know how I can fix it?
The sound is probably coming from the laminations of the output transformer.
This is actually fairly common with tube amplifiers.
[A much-less-likely possibility is that a tube is acting as a transducer.]
It can't cause any harm, and there is nothing that can prevent it,
except maybe replacing the transformer with one that has better
adhesion between the laminations -- in other words, don't bother to try.
You could check the screws that hold the transformer together
to see if they are loose, but they are probably as tight today
as they were when the factory assembled it.
If they aren't obviously loose, don't try to tighten them.
Impedance taps on tube amplifiers are usually fairly approximate.
Most of the recommendations I've ever seen about connecting 6 Ohm
speakers to tube amps have said that the 8 Ohm tap is the best choice.
The fact that the speaker didn't produce any sound,
even though the amplifier itself did,
means that there is no connection where one should exist
in the output transformer secondary circuit.
For the following, I consulted a poor picture of the schematic on Photobucket:
Try connecting to the 4 Ohm tap.
If you still don't get any sound, shut the amplifier off,
disconnect all speaker wires, and use an ohmmeter
to check the continuity of the secondary.
You should see nearly dead shorts between any two terminals.
If it's open, the transformer would have to be replaced.
That may be possible, but it's a job for a good technician
rather than a D-I-Y-er.
There is a feedback connection from the transformer secondary
to an earlier stage in the unit, so there may be some continuity
(at least 4000 to 5000 Ohms, more or less)
between the secondary and the chassis.
Don't let that confuse your investigation.
Oops! Gotta add some more:
If there is a short in the transformer (which is much
more difficult, but still possible, to determine),
that would be another reason for replacement.
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Groove Tubes Gold Series GT-6201-M Preamp Tube $20.95 Groove Tubes Gold Series GT-6201-M Preamp Tubes exhibit low noise, hum and microphonics and are specially selected for use in recording microphones. A very quiet selected version of a 12AT7. These were used for critical applications such as microphones which use the 12AT7, studio gear, and vacuum tube preamplifiers that use a 12AT7 tube.This is a Russia made NOS JAN spec tube (Joint Army/Navy Spec) made in the late 70's.These GT-6201-M Preamp Tubes feature long lasting, really heavy duty dual triodes, usually used in the driver stage of an amp, aka: Phase inverter, and they take a beating driving the power tube changes.Country of origin: RussiaCountry of origin: Russia |
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Groove Tubes Gold Series Gt-6201-M Preamp Tube $20.95 Groove Tubes Gold Series GT-6201-M Preamp Tubes exhibit low noise, hum and microphonics and are specially selected for use in recording microphones. A very quiet selected version of a 12AT7. These were used for critical applications such as microphones which use the 12AT7, studio gear, and vacuum tube preamplifiers that use a 12AT7 tube.This is a Russia made NOS JAN spec tube (Joint Army/Navy Spec) made in the late 70's.These GT-6201-M Preamp Tubes feature long lasting, really heavy duty dual triodes, usually used in the driver stage of an amp, aka: Phase inverter, and they take a beating driving the power tube changes.Country of origin: RussiaCountry of origin: Russia |
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LR Baggs Gigpro Universal Preamp $89.95 The Para DI , Gigpro and Mixpro are three universal preamps from LR Baggs that will improve the tone of just about any pickup you plug into them. All of these preamps feature adjustable gain, class 'A' discrete circuitry, and a phase button to fight feedback. These preamps are versatile enough to work with acoustic guitars, electric guitars, violins, bass, and other stringed instruments. LR Baggs endorsers include: Jackson Browne, James Taylor, Dixie Chicks, Lenny Kravitz, Vince Gill, Kathy Mattea, Janis Ian, Phil Keaggy, Pete Anderson. The Gigpro is a smaller single channel belt clip preamp that is modeled after the Para DI and will work with almost any type of pickup or mini-mic. Place it on your belt or guitar strap and it will give you fingertip control of your sound right at your side. As a musician, you are an artist...a communicator. The notes, chords, rhythms, and melodies you play on your instrument need to be heard loud and clear by your audience. Whether your focus is getting the best tone from your instrument on stage or in the studio - L.R. Baggs products can help you sound great. They've spent 20 years developing the best sounding pickups and preamps on the planet. This is the sound you've heard from players like Vince Gill, Pete Townsend, Doyle Dykes, Eric Johnson, Phil Keaggy, Earl Klugh, Alison Krauss, Lenny Kravitz, Kathy Mattea, Natalie Merchant, Jean Luc Ponty, James Taylor, and countless other talented players around the world. So...are you ready to find the right gear to take your tone to the next level? Their electronics are the product of 20 years of relentless improvement and the quest for perfection. Their quality has been recognized with great reviews and numerous awards. They have also garnered a well deserved reputation as the most advanced and best sounding circuitry for pickups on the planet. They are magic. You can be assured that you will sound your absolute best when you use any L.R. Baggs preamp. The Gigpro is a single-channel belt clip preamp that will work with most pickups. It also provides 9V phantom power for mini-mics and other phantom powered onboard electronics. They have pared the features down to the bare essentials but you will find everything you need to get the best sound possible from your pickup. The EQ, for example, has only two bands plus a variable low cut but you will be amazed at how flexible and intuitive it is to use. The circuitry is generally modeled after the ever-popular Para Acoustic D.I. but L.R. Baggs has made several key innovations. First, the circuitry is 100% Class A and discrete from input to output. Secondly, they have designed the circuitry in a way that makes the sound of the preamp almost tube like. Third, the EQ is entirely passive. Fourth, they have used only the highest grade audiophile components. When you add it up, the Gigpro is the best sounding, easiest to use, most effective and quietest preamp that L.R. Baggs has ever created. Big things do come in small packages |
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Groove Tubes Gold Series GT-12AT7 Preamp Tube $13.49 The Groove Tubes GT-12AT7 preamp tube is manufactured to the highest quality JAN spec. NOS, made in Russia for extremely long life. Used widely in most U.S.-made amps and, in particular, Fender amps. Fender amps with reverb use 2 - 12AT7s -- one for the reverb drive stage, and one as a phase inverter to drive the push/pull output stage. The makeup of the 12AT7 is very similar to the 12AX7 and it can be substituted for a 12AX7 in a pinch. Some players prefer the 12AT7 in the driver stage of a Marshall for a cleaner, brighter tone. (The driver or phase inverter is the 12AX7 located nearest the power tubes.) The 12AT7 is rarely used in a tone-generating stage, but rather in function stages, so the Groove Tubes GT-12AT7 is selected for durability.Country of origin: RussiaTested under extreme conditionsGuaranteed free of excess noise and squealJAN spec.MilitaryNOSExtremely long lifeCountry of origin: Russia |
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Groove Tubes Gold Series Gt-12At7 Preamp Tube $13.49 The Groove Tubes GT-12AT7 preamp tube is manufactured to the highest quality JAN spec. NOS, made in Russia for extremely long life. Used widely in most U.S.-made amps and, in particular, Fender amps. Fender amps with reverb use 2 - 12AT7s -- one for the reverb drive stage, and one as a phase inverter to drive the push/pull output stage. The makeup of the 12AT7 is very similar to the 12AX7 and it can be substituted for a 12AX7 in a pinch. Some players prefer the 12AT7 in the driver stage of a Marshall for a cleaner, brighter tone. (The driver or phase inverter is the 12AX7 located nearest the power tubes.) The 12AT7 is rarely used in a tone-generating stage, but rather in function stages, so the Groove Tubes GT-12AT7 is selected for durability.Country of origin: RussiaTested under extreme conditionsGuaranteed free of excess noise and squealJAN spec.MilitaryNOSExtremely long lifeCountry of origin: Russia |
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Groove Tubes 12AT7 Preamp Tube $16.95 The 12AT7 is durable and usually used as a phase splitter or driver tube (part of the power section). It is great for most US made amps, especially Fender. Great for Marshall in the driver stage for a cleaner, brighter tone (should be changed every time power tubes are replaced for best performance). |
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Mullard 12AX7 Preamp Tube $19.99 The Mullard 12AX7 Preamp Tube delivers a large sound stage with excellent detail. Factory selected for low noise and minimum microphonics. |
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Mullard 12Ax7 Preamp Tube $19.99 The Mullard 12AX7 Preamp Tube delivers a large sound stage with excellent detail. Factory selected for low noise and minimum microphonics. |
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Universal Audio 710 Twin Finity Microphone Preamp $799 The 710 Twin Finity uniquely combines both the classic retro warmth of UA tube design and the transient bite of solid-state. Housed in a 2 rack space, half-rack, all-metal chassis, the 710 Twin Finity was created specifically to add the tonal versatility and sonic inspiration missing from generic audio interface preamps. Versatility makes the 710 Twin Finity the perfect preamp partner for any mic collection. Plus, the discrete JFET DI input circuit can also easily handle any electric instrument. Guitar and bass players will especially appreciate the 710s ability to bring out the best of both active and passive pickups. Universal Audio 710 Twin Finity Features Twin Finity Tone-Blending Mic/Line Preamp & Hi-Z Instrument DI Dual-Path 310 volt Class-A Tube and Transimpedance Solid State Preamp Phase-Aligned Tone-Blending of Tube and Solid State Dual Gain Stages: Wire with Gain to Creamy to Crunchy Discrete JFET DI with 2.2M ohm Ultra Hi-Z impedance Monolithic Balanced Output Stage 70dB+ of gain, +48V Phantom, Pad(-15dB), Phase Invert, and Low Cut Filter(75Hz) Output and Drive backlit VU metering Portable, Rack-Mountable design for Studio, Desktop or Stage 19 inch Rack Kit Included, Optional Desktop Handle Kit also available Front Panel Hi-Z Input (switched from Mic/Line automatically via Jack Detect) Rear Panel XLR Mic Input, XLR Line Input and XLR Line Output Universal Internal Power Supply Heavy-Duty Metal Construction, Designed and Made in the USA The key to its sonic flexibility lies in its innovative circuit design, featuring a solid-state transimpedance input amp simultaneously driving separate, phase-aligned tube and solid-state gain stages, which are then summed to a single output.. The mix between the 310 volt single-ended class-A triode tube stage and solid-state transimpedance stage is controlled via the Blend Knob. Blending is continually variable between 100% tube and 100% solid-state offering a practically infinite range of unique pre-amp tones and the ability to easily dial-in your own signature sound. Like all our other preamp designs, the 710 Twin Finity features dual gain-stage controls (Gain/Level) which can radically vary the amount of coloration and distortion by allowing you to crank up the input gain like a guitar amp. The VU meter features a unique Drive mode allowing you to see how hard you are driving the input stage. |
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PreSonus TubePRE Microphone Preamp $71.89 The PreSonus TubePRE Microphone Preamp lets you add character to your signal by varying the amount of gain and tube drive. A 12AX7 tube in this single-channel mic preamp fattens your signal while dual-servo gain stages let you simultaneously output to your amp and console. Sterling specs include 10Hz-80kHz frequency response, a 94dB noise floor, and >90dB S/N ratio. Capacitor-free circuitry and wide dynamic control give you a big boost without noise. Includes 48V phantom power, phase reverse, 20dB pad, and 80Hz rumble filter. A large VU meter with a cool blue backlight keeps you informed. Balanced/unbalanced and XLR I/O give the PreSonus TubePRE flexibility. Great as a studio direct box.12AX7 and dual-servo gain stagesCapacitor-free gain stage for maximum fidelity and low noiseXLR mic and high-Z instrument inputs on back panelXLR (balanced) and 1/4" (unbalanced) outputs on back panelSupports dual output of signal10Hz-80kHz frequency response>90dB S/N ratio94dB noise floorVariable gain and tube driveGain: 3dB to +48dBTube drive: 0dB to +20dB48V phantom power-20dB pad and polarity reverse80Hz rumble filterLarge VU meter with blue backlightExternal wallmount power transformerRackmountable with optional adapter |
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UltraSound Ultra PDI Preamp DI $129 The UltraSound Ultra PDI Preamp DI is a great direct box and a full-featured preamp. The Ultra PDI lets you dial in clear, natural sound. Routes to a stage PA from a balanced XLR output. A parallel 1/4" out sends signal to your stage amp. The effects loop features a 1/4" send and return rather than a TRS system requiring a Y cord. Tone controls include active bass and treble EQ, mid-dip shape control, and a notch filter. Operates on 48V phantom power or battery (not included). |
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Ultrasound Ultra Pdi Preamp Di $129 The UltraSound Ultra PDI Preamp DI is a great direct box and a full-featured preamp. The Ultra PDI lets you dial in clear, natural sound. Routes to a stage PA from a balanced XLR output. A parallel 1/4" out sends signal to your stage amp. The effects loop features a 1/4" send and return rather than a TRS system requiring a Y cord. Tone controls include active bass and treble EQ, mid-dip shape control, and a notch filter. Operates on 48V phantom power or battery (not included).Full-featured preamp and DI box Bulletproof metal housing Input gain control to allow proper setting for the great variety of acoustic pickup outputs Balanced XLR output for routing signal to PA system Parallel 1/4" out for sending signal to stage amp Both stage and PA outputs have their own level controls Parallel input jack allows a tuner to be plugged in in-ine without degradation of signal Effects loop 48V phantom power capability Active bass and treble EQ Mid-dip shape control permits removal of honky mids Notch filter permits dialing out problem feedback Combination of controls allows any acoustic player to dial in a natural, useable sound at amplified volumes |
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Xotic BB Preamp Part 2 - Les Paul
Audio mixers to mix different sounds and enhancing sound effects
Sound mixers, also called as sound boards or sound consoles are the most general type of audio equipment in the audio production world. Each sound operator should know about the different sound mixers available and the correct way to use them. A sound mixer take two and even more signals, merges them together and offers more than one output signal. In addition to mixing signals, sound mixers enable to adjust levels, improve sound with effects and equalization, make monitor feeds as well as record various mixes.
Mixers are available in wide variety of designs and sizes from massive studio consoles to little portable units. Mixers are generally described through the total number of channels they sport. For instance, a 12-channel mixer includes 12 input channels. That is you can put in 12 individual input sources. You may also notice a specification like “24x4x2” that signifies 24 input channels, four subgroups and 2 output channels.
The mixers accessible are perfect for project as well as home studios or also on stage and in the recording studios. Many of the mixers present incredibly low-noise along with separate mic pre THD and are proficient enough to handle sound inputs varying from whisper to scream or even can easily handle hot line level signals devoid of any extra coloration. Some mixers provides a control room or phones source matrix, tape outputs, Master aux section along with EFX, a high volume headphone amplifier as well as balanced TRS and XLR outputs.
The most amazing aspect of audio mixers is that instead of unsealed, cheap potentiometers, many of audio mixers include co-molded pots that provide substantial impact relief and strain. A majority of the audio mixers available are the perfect pick for any type of situation that needs superior audio mixing, particularly where budget or/and space constraints are a problem. The audio mixers are beneficial for all kinds of recording purposes, including mixing the line output of more than one instrument amps in one mixer channel.
What makes the audio mixers an essential part of the audio recording equipment are its various exclusive features that almost each mixer possess. Ultra low noise mixer along with highest headroom, 4 precision engineered XDR premium studio grade mic preamps, 14 line input, constant loudness pan pots, 3 band active EO of 2.5 kHz, 80 kHz and 12 kHz, phantom power for the premium condenser mics and in built power supply are few of the features of audio mixers.
Few audio mixers also sports planet earth switching power supply for the global use, separate 48v phantom power-switches at all mic inputs and 60 mm logarithmic tape faders for linear, smooth fades.
About the Author
Michael Russell, the writer has a thorough knowledge about audio recording equipment. To get details about other studio recording equipment visit the website http://www.dragonaudio.com.
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