JPS6036893Y2 - Phono input switching circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a phono input switching circuit suitable for use in an input circuit of a stereo amplifier that receives an input signal from a player.

Generally, in the input circuit of a stereo amplifier, the level of the input signal applied to the input circuit differs depending on the type of signal source, so a function is required to adjust the signal supplied to the next circuit such as the integrated amplifier to a predetermined level.

For example, in the above input circuit, if the input signal is an output signal from a player, the pickup cartridge of the player is a moving magnet type (hereinafter referred to as M
M type) and moving coil type (hereinafter referred to as M type).
Since the output level generally differs depending on the type of pickup cartridge (called C type), it is necessary to change the signal path depending on the shape of the pickup cartridge and always supply a signal at a predetermined level to the integrated amplifier. If it is a high output type such as MM type, the output signal is supplied as is to the integrated amplifier, and if it is a low output type such as MC type, the output signal is amplified by the head amplifier and then sent to the integrated amplifier. supply)
.

Conventionally, as a circuit having the above-mentioned function, for example, a phono input switching circuit shown in FIGS. 1 and 2 is common.

In other words, the circuits shown in these figures are all input switching circuits of a stereo amplifier that receives an output signal from a player, and the first phono input switching circuit A shown in FIG. The signals are supplied to the equalizer amplifier 5 directly or through the head amplifier 4 by switching the switches 2 and 3 which are interlocked with each other.

However, when the pickup cartridge serving as the signal source is a high output type such as the MM type, this circuit path is
By contacting the switching contacts 2a and 3a of , 3 with the contacts 2b and 3b, respectively, the signal can be directly supplied to the equalizer amplifier 5, and if this is a low output type such as an MC type, the switching contacts 2a and 3a are connected to contacts 2c and 3, respectively.
By contacting the C side, the signal can be amplified by the head amplifier 4 and supplied to the equalizer amplifier 5.

By the way, in this phono input switching circuit A, when the signal source is, for example, an MC type pickup cartridge, even though the signal level of this signal source is extremely small, the thread path from the input terminal 1 to the head amplifier 4 is Since the switch 2 is inserted between the switches 2 and 2, there is a drawback that the S/N ratio between the contacts of the switch 2 deteriorates.

That is, since the input contact is inserted into the weak signal line of the MC cartridge, there is a problem that the sound quality deteriorates.

Furthermore, when selectively using a pickup cartridge serving as a signal source, for example, a high-output type such as the MM type and a low-output type such as the MC type, since there is a single input terminal, the above-mentioned When switching the switches 2 and 3, it is necessary to reconnect the output cable of the cartridge to the input terminal each time, which has the drawback of being troublesome.

The phono input switching circuit B shown in FIG. It has an input terminal 10 that is supplied to the amplifier 7, and when the pickup cartridge is of a high output type such as an MM type, the signal is input when the switching contact 6a of the switch 6 is in contact with the contact 6b. is input to the input terminal 8, and if it is a low output type such as an MC type, the signal is input to the input terminal 10 with the switching contact 6a in contact with the contact 6c, and the circuit of FIG. Similarly, a signal system suitable for the shape of the pickup cartridge is formed.

By the way, according to this phono input switching circuit B, while it is possible to eliminate the drawback of deterioration in signal quality of the circuit shown in FIG. Conversely, if you exchange
It is necessary to change the input terminal each time (reconnecting the output cable of the cartridge to the input terminal), which has the disadvantage that this work is troublesome.

This invention was made to eliminate the drawbacks of the conventional phono input switching circuits mentioned above, and the purpose is to provide a phono input switching circuit that is easy to switch and does not cause deterioration of signal quality. It is something to do.

To achieve this purpose, this invention has a dedicated input terminal for a moving magnet type pickup cartridge, a dual-purpose input terminal for a moving magnet type pickup cartridge and a moving coil type pickup cartridge, and an input terminal connected to the dual-purpose input terminal. one contact is connected to the dedicated input terminal, the other contact is connected to the dual-purpose input terminal, and short-circuits and disconnects the dedicated input terminal and the dual-purpose input terminal. A first switch, one fixed contact is connected to the dedicated input terminal, the other fixed contact is connected to the output terminal of the head amplifier, and selects one of the signals supplied to both fixed contacts from the switching contact. It is characterized by comprising a second switch that outputs a signal.

An embodiment of this invention will be described below with reference to FIG.

The input switching circuit C shown in this figure has a first input terminal 21 dedicated to the MM type pickup cartridge, a second input terminal 22 used for both the MM type pickup cartridge and the MC type pickup cartridge, and these first and second input terminals. A first switch 23 that short-circuits/disconnects input terminals, and an MC that amplifies the input signal input to the second input terminal 22.
A head amplifier (amplifier) for a type cartridge, that is, a head amplifier 24 whose input terminal 24a is connected to the second input terminal 22, and an input signal input to the first input terminal 21 or through the first switch 23. A switch that selectively obtains the input signal input to the second input terminal 22 and the output of the head amplifier 24, that is, the contact 25b is connected to the input terminal 21, and the contact 25c is connected to the output terminal 24b of the head amplifier 24. connected, these contacts 25b
, 25c, and a second switch 25 for selectively obtaining the signals supplied to the switching contacts 25a.

The signal obtained at the switching contact 25a of the second switch 25 is supplied to the equalizer amplifier 26.

Next, a method of using the input switching circuit configured as described above will be explained.

First, a case will be described in which the output terminal of a player using an MM type pickup cartridge is connected to the input terminal 21.

In this case, the first switch 23 is opened and the switching contact 25a of the second switch 25 is kept in contact with the contact 25b.

An input signal inputted to the input terminal 21 under such settings of the switches 23 and 25 is supplied to the equalizer amplifier 26 as it is through the switch 25.

When the input terminal 21 is used in this manner, only the MMMM equal high output type pickup cartridge is used.

Next, a case will be described in which the output terminal of the player is connected to the input terminal 22.

In this case, when the pickup cartridge is a high output type such as an MM type, the switch 23 is closed and the changeover contact 25a of the switch 25 is brought into contact with the contact 25b, and when the pickup cartridge is a low output type such as an MC type, the switch 23 is closed. When the switch 23 is opened, the switching contact 25 of the switch 25 is opened.
If a is brought into contact with the contact 25c, the input circuit required at that time can be obtained in the same manner as above.

In this case, if the pickup cartridge is of the MM type or equivalent high output type, the output impedance of this pickup cartridge is lower than the input impedance of the head amplifier 24.

When the input terminal 22 is used in this way, the necessary input circuit can be obtained by switching the switches 23 and 25 as in the case of the input terminal 21, and if the pickup cartridge is of the MC type or other low output When the signal is in the form of a signal, the signal can be input directly to the head amplifier, which has the advantage of not causing signal quality deterioration.

Furthermore, when the pickup cartridge is an MM type, its output signal is supplied to the equalizer amplifier 26 via the switches 23 and 25, but in this case, since the output signal of the cartridge is at a high level, the sound quality is controlled by the switch 23. There is no need to worry about deterioration.

Therefore, it can be seen that the input terminal 22 is extremely suitable as a dual-purpose input terminal for MC type and MM type cartridges.

In addition, in this invention, one input terminal is dedicated to MM type, and the other input terminal is used for MM type and MCC type.
This is because most commonly used pickup cartridges are of the MM type, so it is often more convenient to make the input terminal for the MC type compatible with the MM type.

As is clear from the above description, according to this invention, there is a dedicated input terminal for a moving magnet type pickup cartridge, a dual-purpose input terminal for a moving magnet type pickup cartridge and a moving coil type pickup cartridge, and an input terminal that can be used for both the above-mentioned purpose. A moving coil type head amplifier connected to an input terminal, one contact connected to the dedicated input terminal and the other contact connected to the dual-purpose input terminal, and a connection between the dedicated input terminal and the dual-purpose input terminal. A first switch that short-circuits and disconnects, one fixed contact is connected to the dedicated input terminal, the other fixed contact is connected to the output terminal of the head amplifier, and a signal is supplied from the switching contact to both fixed contacts. Since it is equipped with a second switch that selectively outputs either one, the output signal of the MC type pickup cartridge can be supplied to the head amplifier without going through the switch, and deterioration in sound quality can be prevented. .

Further, it is possible to switch between an MM type pickup cartridge and an MC type pickup cartridge or two MM type pickup cartridges without changing the connection of the output cable, and operability can be greatly improved.

[Brief explanation of the drawing]

Figures 1 and 2 are respectively a conventional phono input switching circuit A,
FIG. 3 is a circuit diagram of a phono input switching circuit C according to this invention. C... Input switching circuit, 21... First input terminal (dedicated input terminal), 22... Second input terminal (common input terminal), 23... ...First switch, 24...Amplifier (head amplifier), 25
...Second switch.

Claims (1)

[Scope of utility model registration request] a dedicated input terminal for a moving magnet type pickup cartridge, a dual-purpose input terminal for a moving magnet type pickup cartridge and a moving coil type pickup cartridge, and a head amplifier for a moving coil type whose input terminal is connected to the dual-purpose input terminal; a first switch having one contact connected to the dedicated input terminal and the other contact connected to the dual-purpose input terminal to short-circuit or disconnect the dedicated input terminal and the dual-purpose input terminal; and one fixed contact. a second switch connected to the dedicated input terminal, the other fixed contact of which is connected to the output end of the head amplifier, and selectively outputs one of the signals supplied from the switching contact to both fixed contacts; A phono input switching circuit characterized by comprising: