E80f preamplifier design
Ef86 equivalent. Resources saved on this page: MySQL I can think of a few that are not pinned the same, but that isn't any use I am familiar with the and the Z, and can't say I have encountered any of the rest. All the CV numbers indicate an EF86 or equivalent. The 6BR7 is the Brimar version of the EF86 and is supposed to be good but has a different pin-out and the 6BS7 is supposed to be even quieter but has its grid connection on a top-cap.
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Image Posted on October 21, Updated on October 21, Posted on October 8, Updated on October 13, It is important to bias a tube to stay within its rated dissipation. Especially with guitar amps—they tend to run their tubes at idle conditions which are conservative. Some high-end audio amps run their power tubes quite hard—in that case, rebiasing is necessary. Many amps have no bias adjustments at all, and are designed so that you do not need to concern yourself with bias. This includes most Mesa-Boogie guitar amps, most amps using EL84s, and many single-ended triode hi-fi amps.
We suggest that users consult with the equipment manufacturer, if possible. Practically speaking, you should only replace tubes in an audio amplifier when you start to notice changes in the sound quality.
Also, the gain of the amplifier will decrease noticeably. This is usually enough of a warning for tube replacement. If the user has very stringent requirements for observing tube weakening, the best way to check tubes is with a proper mutual- conductance-style tube tester. These are still available on the used market; though new ones have not been manufactured in many years.
One tester is being manufactured today, the Maxi-Matcher. If you cannot get your own tube tester, speak to a service technician for his recommendations. See our cathode section 2A above for some idea of typical lifetimes for tubes. Large ceramic power tubes are usually operated in equipment that has metering of the plate current or power output. When the tube cannot reach the rated plate current or power output for the equipment, the tube is usually considered to be at the end of its normal life.
The operating manual should give a more complete procedure for estimating the health of the tube. Glass tubes have visible glow inside them. Most audio types use oxide-coated cathodes, which glow a cheery warm orange color. And thoriated-filament tubes, such as the SV and SV triodes, show both a white-hot glow from their filaments and in some amplifiers a slight orange glow from their plates.
All of these are normal effects. Some newcomers to the tube-audio world have also noticed that some of their tubes emit a bluish-colored glow. There are TWO causes for this glow in audio power tubes; one of them is normal and harmless, the other occurs only in a bad audio tube.
These tubes rely on ionized gas to control a voltage tightly, and normally glow either blue-purple or pink when in normal operation. If you are unsure if these special tubes are used in your amplifier, consult with an experienced technican before replacing them. As we said above, it is difficult to tell if a ceramic tube has become gassy. Usually, in a large radio transmitter, a gassy tube will arc over internally. This does not damage the transmitter.
It has protective circuits. The equipment operating manual should give more information on this. Class A means that the power tube conducts the same amount of current all the time, whether idling or producing full power. Class A is very inefficient with electricity but usually gives very low distortion. This gives the greatest possible linearity and is used with triodes such as the SVB, and with audio beam tetrodes and pentodes. This means the grid will draw current from the cathode and heat up.
A2 is not often used with beam tetrodes, pentodes or triodes like the SVB, especially in audio. Usually a class-A2 amplifier will use tubes with special rugged grids, such as the SV and SV series of triodes. Class A2 also requires a special driver circuit, that can supply power to the grid.
Class AB applies only to push-pull amplifiers. This gives greater efficiency than Class A. It also results in increased distortion, unless the amplifier is carefully designed and uses some negative feedback.
It is like Class AB, except that the tubes idle at or near zero current. This gives even greater efficiency than Class A or AB. If careful design is not undertaken, the result may be crossover distortion, which appears at the midpoint of the output waveform and has very bad-sounding effects in audio. Most solid-state audio amplifiers use class B, because the transistors undergo less heat stress when idling.
Ultralinear operation was invented by David Hafler and Herbert Keroes in It uses only beam tetrodes or pentodes, and special taps on the output transformer.
The taps connect to the screen grids of the tubes, causing the screens to be driven with part of the output signal. This lowers distortion considerably. Why are different kinds of power supplies used in various tube amplifiers? Why do some use tube amplifiers? Why do some use tube rectifiers, while others use solid-state rectifiers, while still others have electronic regulation? Tube rectifiers are still used in power supplies of some guitar amps, because the current a tube rectifier can produce varies somewhat with the load.
It is quite different in response from a solid-state rectifier. Many audiophiles also prefer this classic design for much the same reasons. Special high-speed silicon rectifiers are available at high cost.
They are rarely used in products other than a few high-end amplifiers. Tube rectifiers have faster transient response than most solid-state rectifiers, also making them useful in some high-end designs. It is expensive to regulate the high voltages in a tube amplifier, so it is done only in expensive top-line models. Class A amplifiers have less need for regulation since they draw nearly the same DC power at all times.
It is dependent on the circuit design. The only way to see if you need an amplifier with a regulated supply is to listen to it and carefully compare it with similar amps with unregulated supplies.
What are the advantages of an OTL amplifier over a conventional one with an output transformer? Should I get an OTL? What about its reliability issues? OTL, or output-transformerless, amplifiers are special high-end products. Because it is expensive and difficult to wind an output transformer for a tube amplifier to achieve the best possible performance, some designers have chosen to eliminate the transformer altogether. Unfortunately, tubes have relatively high output impedances compared to transistors.
So, tubes with large cathodes and high peak emission capability are used—in many push-pull pairs. A well-designed OTL is capable of the best audio performance available today.
OTLs usually require more maintenance and greater care in use than transformer-coupled amps. In recent years, OTLs have gotten a bad reputation for unreliability.
This was only a problem with some low-cost manufacturers, who have since gone out of business. A well-designed OTL can be just as reliable as a transformer-coupled amp. Which should I use? Parallel feed and shunt feed are the same technique. Basically, a choke is used to load the power tube usually one, in SE mode , while the output transformer is coupled to the plate of the tube through a capacitor. So, the plate current of the tube does not flow through the output transformer.
This can be a very expensive technique to implement, since the choke must be as carefully wound as the output transformer. It does offer a possible performance improvement. You should try to audition a parallel-feed high-end amp before buying it. This technique is considered too expensive for use in guitar amps.
SRPP circuits and mu-follower circuits are special designs which use a lower tube for gain , and an upper tube which serves as the plate load for the lower tube. The upper tube also acts as both a cathode follower and as a constant-current source for the lower tube. If properly designed, either circuit can offer improved performance over an ordinary resistor-loaded tube stage.
These circuits are used only in preamp stages and in the driver stages of power amps, usually SE types, in high-end audio. If you want to build your own, see Technical Bulletin 27 for a good-quality mu-follower circuit that can be used as a line stage preamp or a power-amp driver. If you want to learn more of the technical details behind vacuum-tube electronic design, we recommend the following books. All of the books are available from large book dealers and from some of our audio-tube Stocking Distributors.
Back in , British scientist John Ambrose Fleming first showed his device to convert an alternating current signal into direct current. This diode essentially consisted of an incandescent light bulb with an extra electrode inside. And since the extra electrode is cold and the filament is hot, this current can only flow from the filament to the electrode, not the other way. So, AC signals can be converted into DC.
Later and to this day , the diode vacuum tube was used to convert AC into DC in power supplies for electronic equipment. Many other inventors tried to improve the Fleming diode, most without success. The only one who succeeded was New York inventor Lee de Forest. In he patented a bulb with the same contents as the Fleming diode, except for an added electrode. This device, the Audion, was the first successful electronic amplifier.
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Circuit Diagrams of various equipment. My first steps along the road of recorded sound As a young lad of about 12 years old, my parents brought me a second-hand "Fidelity" record player. A typical model from the early 's, consisting of a small 7" turntable with a valve amplifier etc, fitted into a small carrying case. After a year or so the unit no longer worked. The amplifier had failed, but the turntable still worked. So I experimented by fitting a cheap Ronette stereo crystal cartridge into the arm.
Making Conscious Dreaming possible: the Audio Note M9 RIAA Signature
Now knowing that it was possible to recreate that "Quad" sound, via DIY, it was time to build a stereo version on a single chassis. I had always liked the looks of the Radford, so I decided to go down that avenue of design. Layout of the wound components, such as the mains transformer, was critical. In an attempt to keep "Mains Hum" to a minimum. Again, the end results were very pleasing. The E80F's draw more current for the heaters, but the mains transformer used in the DIY design, had sufficient headroom to allow for this. The overall sound was amazing, and when listing to recordings made using simple microphone techniques, the depth of the stereo image was absolutely fantastic. This was especially true, on recordings using a single pair of microphones, using the "Middle and Side" technique.
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The Svetlana EF86 is a version of a small pentode which was popular in Europe for use in hi-fi equipment from through the s. Unlike the majority of pentodes of this type, the EF86 possesses low distortion, low hum induction and low ionization noise. Further, it has a built-in electrostatic shield, making an external tube shield unnecessary. No other tube in production today has all these features.
Power supply for condenser microphone tube buffer amp
W hat started out as a dual design now ends up in a single design. Of course some iterations could be made to the 6S4A version but doing that would not meet the design criteria, which was affordable, dc-coupled and compact. So the final design is here using an E80F as input, a triode connected D3A and Magnequest parafeed B7 line out transformers. This design is stable and silent, meaning no hum and noise hiss. So what does it look like?
Vacuum Tubes
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By pham , May 22, in Do It Yourself. After a few weeks burn-in period of this little beast, I found it's very relaxing to listen to. It also enhances the soundstage and life-like of Focal Utopia makes it way more enjoyable to hear. I've gotten a few PM's asking about the schematics and stuff so I decided to open a thread to discuss more here.
Users browsing this forum: Google [Bot] and 9 guests. Posted: Mon Feb 20, pm. If the above post is about using a MC cart. On a close comparison with the more complex more expensive Hiraga MC preamp there is very little in it.
No, the idea here was to create an instrument which would not only extract as much information as possible from the groove, but also portray that information in the most elegant, beautiful, artistic, musical way possible — even if it does involve liquid helium cooling…. The E80F is quite electrically similar to the EF86 — designated as a low noise, low microphony valve especially designed for this type of service, except the E80F, some would claim, more successfully achieved those aims. I chose to use a pentode over the cascode can be viewed as a pseudo-pentode formed by two stacked triode sections I would normally use, because I needed to connect the pentode anode direct well via a coupling cap into the RIAA network, rather than via a series resistor. I am using the pentode as a transconductance device which means it outputs a current proportional to the input voltage , and need the extra headroom a pentode provides over a cascode at a given anode voltage. The EQ network itself is a departure from the norm.
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