Direct coupled 45 amplifier schematic
This review page is supported in part by the sponsor whose ad is displayed above. Manufacturer's e-mail. Between the Circuit and the Implementation lies the Shadow "The circuit for the 2A3 came through a long distillation and a bit of experimentation. I got together all the 2A3 circuit designs I could find and tried each one.
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45 SE Triode Schematic Required
A further object is to provide a high fidelity amplifier with a high degree of reliability and capacity to deliver high overloads at frequencies down to substantiallyzero frequency or direct current as well as in the video region of the frequency spectrum.
A further object of the invention is to obtain prompt and faithful response to transient conditions and high fidelity amplification of speech and other signals of constantly varying frequency and amplitude which make the transient characteristics of the amplifier of as great importance as the characteristics under steady state conditions.
Another object of the invention is to make'the magnitude and phase of the output voltage substantially independent of load impedance variations that would normally be encountered and to provide a generator having the power to be the principal factor in the determination of magnitude and phase of the output voltage. Still another object is to apply corrective feedback for the reduction of distortion Without creating undesirable transients.
A further object is to eliminate the necessity for directcurrent flow in the load circuit, transformer coils, choke coils or devices which may be subject to magnetizing or to other unilateral effects.
An additional object is to permit grid excitation toenter the positive grid region without creating distortions 'or transients in the coupling circuits. A further object is to accomplish maximum coupling elficiency and minmium reactive eifects in a simple circult.
Still another object is to permit the free interchange of direct current and direct-current potentials. It is also an object to make corrective feedback fully effective at direct current and to obtain great stability.
Other and further objects, features and advantages of the invention will become apparent as the description proceeds. The grids of the output tubes are supplied in opposite phase by a phase splitter circuit. Preferably, an input amplifier tube is provided, having a direct feedback connection from the output circuit.
For thesake of Obtaining a most faithful wave reproduction and permitting high positive peak currents to be supplied at high peak voltage, cathode follower connections are provided for exciting the grids of both the output tubes. A better understanding of the invention will be afforded by the following detailed description considered in conjunction with the accompanying drawings, in which Fig. Like reference characters are utilized throughout the drawings to designate like parts.
In the arrangement illustrated in Fig. By way of example, the plate power supply is illustrated as taking the form of a step-up transformer 11 energizing a voltage doubling rectifier circuit consisting of a pair of rectifier units 12 and 13, connected across a pair of condensers 14 and 15, connected in series between the plate input terminal lines represented as a grounded line 16 and positive high potential line The secondary winding of the transformer 11 is connected to the common terminal 13 of the condensers 14 and 15 and to the common terminal 19 of the rectifier units 12 and This circuitis preferred because it automatically provides a fixed appropriate screen potential for tubes T2 and T3.
As shown, the tube T1 has an anode 21 connected to the positive side 17 of the plate supply and the tube T2 has a cathode 22 connected to the negative side 16 of the plate supply. The tube Ti has a cathode 23 connected to, the anode 24 of the tube T2. If the tubes T1 and T2 take the form of tetrode vacuum tubes, as illustrated, screen potential is provided by a dropping resistance 25 connected between the positive plate supply 17 and the screen grid 26, and a screen-voltage condenser 27 is connected between the screen grid 26 and the cathode The screen potential for the tube T2 is provided, by a dropping resistance 28 connected between the mid-terminal 18 of the plate power supply and the screen grid 29 of the tube T2.
In this case the condenser 15 serves also for stabilizing screen voltage. The output from the circuit is taken from the common terminal 31 of the tubes T1 and T2.
For example, as illustrated, there may be a grounded terminal 32 and an ungrounded output terminal 33 coupled to the parallel output terminal 31 from the tubes T1 and T2 through a condenser V For exciting grids or control electrodes 34 and 35 of the tubes T1 and T2 in phase opposition, a phase splitter is provided which may take the form of an electronic discharge tube T shown as a pentode vacuum tube in Fig. The anode 36 of the tube T3 is coupled to the grid 34 of the tube Ti and the cathode 38 of the tube T3 is coupled to the grid 35 of the tube T2.
For the latter coupling, a direct connection is provided since the tube T3 acts as a cathode follower. If large quantities of positive-current peak power are to be handled, preferably a cathode follower T4 is inserted between the anode 36 of the tube T and the grid 34 of the tube T1. As illustrated, the tube T4 may take the form of a triode vacuum tube having an anode 43 connected to the positive side 17 of the plate power supply and a cathode 44 connected through a cathode resist-or 45 to the negative or grounded side 16 of the plate power supply, the cathode 44 being directly connected to the grid 34 of the tube T1 The tube T3 may have a screen grid 46, voltage for which is provided by a suitable source, for example, as.
Patented Jan. The input signal is supplied to the phase splitter tube T3 through a control electrode or grid Preferably, an input amplifier tube T is provided shown as a triode vacuum tube having an anode 48 connected through an anode resistor 49 to the positive side 17 of the plate power supply, a cathode 51 connected through a cathode resistor 52 to a suitable point such as a terminal 53 in the negative power supply 42 and a control electrode or grid 54 to which the input signal terminal 55 is connected.
The anode 48 is coupled to the grid 47 of the phase splitter tube T 3, preferably by a direct connectron where maximum fidelity is desired. For obtaining corrective feedback, effective at all frequencies, even at direct current, a direct connection is made between the cathode 51 of the input amplifier tube T5 and the output terminal 31 of the output tubes T1 andTa, by connecting a conductor 56 between the cathode 51 of the tube T5 and theanode 24 of the tube T2, preferably with a current hmiting resistor 57 interposed in the connection.
In order to maintain a suitable negative bias on the grid 54 of the input amplifier tube T5, a voltage divider is provided, consisting of resistors R5 and Re, which are connected in series between the grounded signal terminal 60 and the negative terminal 53, which is the negative terminal forthe circuit of the tube T5.
The input term1nal55 to which the grid 54 is connected, is as shown, the common terminal or junction terminal of the voltage divider terminals R5 and Re. The negative power supply 42 may be of conventional form consisting as illustrated, of a rectifier unit 58 supplied from another secondary winding of the transformer 11, including conventional filter condensers 59 and series resistors 61 with a voltage regulator gas type tube 62 for the negative power supply terminal 41, and a filter circuit consisting of a resistor 63 and a condenser 64 for the negative supply terminal It will be understood, however, that a separate negative power supply is not required and suitable relative potentials or biases of the various electrodes may be provided in any desired manner known to those skilled in the art.
The two output tubes T1 and T2 are direct coupled order to obtain the unity coupling that is necessary between these tubes to prevent creation of transients which are otherwise unavoidable in push-pull class B circuits in which the output tubes are alternately driven beyond plate current cutoff.
The direct coupling between Tiand T2 connects these two tubes in parallel, and since T1 is a cathode follower, there is imparted to this output circuit an extremely low output impedance or generator impedance, which gives this generator the power to be the principal factor in the determination of the magnitude and phase of the output voltage, thereby maintaining these quantities substantially independent of load impedance variations that would normally be encountered.
Under these conditions, since the generator impedance remains a substantially pure resistance over the entire range of normal operation, corrective feedback for the reduction of distortion can be applied without creating the undesirable transients which must occur in any amplifier with degenerative feedback in which the load impedance varies and can affect the phase of the output voltage from which the feedback voltage is derived.
This connection of T1 and T2 furthermore eliminates the necessity of direct current flow in the load circuit, the transformer coils, or other choke coils because the tubes mutually supply initial plate current to each other; and, during operation, these tubes alternately valve only signal currents into the load.
This arrangement permits grid excitation to enter the positive grid region without creating distortions or transients in the coupling circuits. Maximum simplicity, maximum coupling efiiciency, and minimum reactive effectsare also achieved by this driver circuit. The cathodel follower T4 is connected between T3 and T1 to provide the extra grid current required by T1 during high power output peaks.
The cathode follower has the fortunate property of being especially able to supply high positive peak currents at high voltage. This is exactly the requirement for efficiently exciting T1. T4 furthermore, draws very little current from the power supply except when high current is needed to drive T1 during which interval T4 actually delivers some of its output power directly to the amplifier load through the electron circuit which exists during this interval between the cathode and grid of T1.
This extra power is just what is needed to help reduce distortion during high power peaks. The voltage amplifier T5 provides the final step for the creation of a high fidelity amplifier that is capable of reproducing wave forms with great accuracy.
The amplifier stage usingTs is designed for maximum gain, minimum phase shift, and maximum cathode to ground irn pedance in order that the maximum amount of corrective feedback may be applied with greatest simplicity, greatest effectiveness, and at the expense of a minimum amount of the output power. All circuitsin this amplifier are direct coupled to permit the free interchange of direct current and direct current potentials. This applies also to the inverse or negative feedback circuit.
Since the corrective feedback is thereby made fully effective at direct current, the amplifier possesses an extreme degree of stability. R5 and R6 do not benefit from the self stabilizing property of the amplifier because these resistors must necessarily be outside of the feedback loop. Operation of the output tubes of the amplifier is not limited to the negative grid region because direct coupling permits the transfer of power to the grids without setting up serious transients.
This is further exploited by providing low impedance circuits to drive these grids, thereby increasing the amplifier efiiciency, increasing the available power from any given tube and reducing the load resistance required for optimum termination of the amplifier. When output tubes such as the 6V6 or 6L6 are used in the amplifier the optimum termination resistance for maximum power output for a pair of these tubes is in the order of ohms. The output from the amplifier, in the absence of an output transformer, normally appears on two terminals, one of which is hard at ground potential.
Only signal currents flow between these terminals as would be the case if an output transformer were used. It follows therefore, that it is practical to build the amplifier without providing space for an output transformer on the assumption that there is much more inexpensive space on the reproducer unit or in its cabinet for mounting the output transformer.
In multiple reproducer sound reinforcing systems, the distribution line can readily be fed without a transformer at the amplifier. The effectiveness of the corrective feedback at direct currents practically eliminates any necessity for selecting tubes to obtain optimum or maximum performance. Through the action of the direct current feedback, the tube biases are automatically adjusted for very nearly optimum performance of the amplifier in the presence of wide variations of the tube characteristics extending in some cases even to the use of tubes of different type numbers.
This is especiallytme in the case of the output tubes. My invention is not limited to the use of particular tube types nor to exact electrical dimensions of circuit components.
Nevertheless, I have found that good results over wide range of frequencies may be obtained where the tubes T1 and T2 are 6V6 tubes supplied at volts, with the transformer 11, stepping up from volts to volts A. The particular tube types to be employed, will of course, be varied according to the power output required. Moreover, the circuit is not critical as to the selection of tubes and it is not necessary to match tubes or to select from tubes of the same type in order to obtain a tube which will have precise characteristics in order to obtain satisfactory operation of the circuit.
As illustrated in Fig. While I have described my invention as embodied in concrete form and as operating in a specific manner in accordance with the provisions of the patent statutes, it should be understood that I do not limit my invention thereto, since various modifications thereof will suggest themselves to those skilled in the art without departing from the spirit of my invention.
A vacuum tube amplifier comprising a cathode follower vacuum tube having a cathode, a second vacuum tube having an anode connected to thecathode of said cathode follower vacuum tube, an input tube having a cathode.
Blitz Apr. USA en. Multi-stage tube or transistor amplifier with at least three stages, which contains stages through which the operating current flows essentially one after the other. Multi-stage pulse amplifier with transistors in basic connection and inductive coupling of the individual stages.
Principles of Transistor Circuits
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SET Asylum
Log in or Sign up. Steve Hoffman Music Forums. Wouldnt you guys be tempted for this amp? Location: North Bergen, NJ. I am very much so. I only had a pair of Bel Canto Orfeo amps and it was great! WHitese , Oct 19, Location: Chicago, IL. Its an interesting idea, but have your own parts made There are a limited number of old Mc transformers left that should be reserved for ailing Mc amps that need them.
46 driving 45 – SE Amp
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Wouldnt you guys be tempted for this amp?
As headphone listening becomes more and more a dominant form of high fidelity listening Bottlehead. Jeb has everything documented as far as upgrades are concerned and agree with his findings. The two stereo channels each use half of the tube. In his own words: "Here we have details of my latest build and modding journey for the newest kit in my collection, the excellent Bottlehead Crack with Speedball Upgrade. Instead all the parts are mounted and soldered on terminal strips and connected with solid core wires between the components. I cannot wait to fire it up.
IspraNet Audio: Direct Coupled Single Ended Amplifier
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Direct coupled 2a3 schematic
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The outstanding characteristic of this amplifier from a technical point of view is the use of a direct coupled circuit - that is, no capacitors or coupling transformers are used between stages. I t is basically descended from the classic Loftii and White design presented for the firt time in in the well-known American magazine Radio News. This article caused a sensation not only because of the measured performance of the amplifier, which was exceptional for the times, but also because of the extreme simplicity of the design. In addition, the "comfortable" in those days output power of slightly more than three watts, makes the amplifier's great success easy to understand.
Recently I revisited a beloved amp, the SE This time I will share a more orthodox design without sand in play. If you want to go full DHT, then you have a challenge. I looked back into my favourite list of valves and obviously the 46 came up at first thought. I have used it before with great success in my SE Amp.
THE construction of the amplifier to be described in this article was actually initiated a little over two years ago, at which time I became an enthusiastic audio ham. During the recent war I was associated with radar in a practical way and so became acquainted with the cathode-follower which was used extensively in radar as an inexpensive medium for matching a high impedance to a low impedance in voltage amplifier stages. At that time, it appeared to me that the cathode-follower might be ideally suited for audio output stages where the problem of getting a good impedance match is generally difficult and usually expensive.
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