Archive for January 21, 2014

TRS to XLR Interconnect Cable

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Hello,

If you have been around audio enough you know that accessories, while many times ignored, can become really costly. Interconnect cables are easy to built and you can apply simple techniques to make them much better than the more expensive commercial alternatives.

In this article i will make a TRS – XLR balanced line interconnect. The connection follows the rules described below:

TRS      TO        XLR

Tip                   Hot

Ring                Cold

Sleeve            Gnd

In choosing the cable i recommend to look for braided shield and cloth layer. These features will help get a reliable cable.

TRS - XLR Interconnect Audio Cable  TRS - XLRインターコネクトオーディオケーブル

TRS - XLR Interconnect Audio Cable  TRS - XLRインターコネクトオーディオケーブル

The picture above depicts how i like to prepare the cable for the TRS plug. You can see the braided shield which will connect to the sleeve of the TRS plug.

TRS - XLR Interconnect Audio Cable  TRS - XLRインターコネクトオーディオケーブル

TRS - XLR Interconnect Audio Cable  TRS - XLRインターコネクトオーディオケーブル

TRS - XLR Interconnect Audio Cable  TRS - XLRインターコネクトオーディオケーブル

TRS - XLR Interconnect Audio Cable  TRS - XLRインターコネクトオーディオケーブル

In the picture above you can see my favorite way of securing the plug by using the cloth to tie it around the sleeve terminal.

TRS - XLR Interconnect Audio Cable  TRS - XLRインターコネクトオーディオケーブル

TRS - XLR Interconnect Audio Cable  TRS - XLRインターコネクトオーディオケーブル

I always use heat tube to isolate the shield connection of the cable when using XLR plugs. The XLR terminals are even in height so the shield will have a few mm of bare wire. I want to avoid it to touch the plug chassis on its own so i isolate it.

To solder the cable to the plug it is a good practice to hold the plug vertically like in the picture above.

TRS - XLR Interconnect Audio Cable  TRS - XLRインターコネクトオーディオケーブル

And the finished cable.

 

Thanks for visiting.

[Project Ryu] Field Coil Loudspeaker Mid-Bass Driver

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Hello,

Recently i have finished a pair of field coil mid-bass drivers. The driver has a Fs of 50Hz and a frequency response up to 7kHz. It is a dual voice coil design features a 160mm diameter motor with a max of 1.4T in the gap, Ryu spider, non-treated paper cone, triple roll cloth surround and bullet shaped phase plug.

 フィールドコイルスピーカー field-coil loudspeaker

 フィールドコイルスピーカー field-coil loudspeaker

 フィールドコイルスピーカー field-coil loudspeaker

The voice coil construction was presented in an earlier article here. Inside the gap set at around 1T flux density, the voice coil inductance was measured at 0.52mH @1kHz and 0.15mH@10kHz.

The high compliance of the Ryu spider was measured at around 3.4mm/N for this mid-bass and makes the compliance of the cloth surround the determinant factor in the system’s total compliance value.

 フィールドコイルスピーカー field-coil loudspeaker

 フィールドコイルスピーカー field-coil loudspeaker

Below you can see the impedance measurement and frequency response of these mid-bass drivers. The frequency response is measured with the voice coils connected in parallel. you can see a nice constant 6db/octave rise in response. You can use this characteristic when designing the loudspeaker if you consider baffle step or horn loading.

 フィールドコイルスピーカー field-coil loudspeaker フィールドコイルスピーカー field-coil loudspeaker

I have tested the unit and played Isao Tomita’s Snowflakes are Dancing and The Police Synchronicity. The sound is thin with the voice coils connected in parallel and no baffle but with the voice coils in series even without a baffle you can reach a good tonal balance. This indicates the unit can be used successfully in an Open Baffle system or in a horn loaded enclosure with the voice coils in parallel.

 フィールドコイルスピーカー field-coil loudspeaker

Thank you for visitng.

Project Ryu New Spider Concept Video

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Monitoring Amplifier モニターアンプ P3: Speaker Coupling Delay

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Hello, こんにちは,

私の日本語があまり上手くありませんが許して下さい.

In this article i will present a simple delay circuit that will be used to couple the speakers to the amplifier after a certain settling time was allowed. The circuit also allows for to be controlled by an external 5V logic signal. This can be used to decouple the speakers in case a fault is detected.

これは、アンプがオンされたときにスピーカーを保護するためのDELAY回路であります。それが徐々にコンデンサを充電することによって機能します。コンデンサ電圧が一定値に達したときには、リレーを切り替えります。

The circuit schematic is presented in figure 1 and as you can see it uses just discrete components. It is a linear voltage ramp generator that commands a power transistor. The current charging capacitor C1 and the capacitor’s value are the parameters that set the ramp’s slope.

POT1は、時間遅延を調整します。

Speaker delay circuit schematic

Figure 1

In figure 1 Q3 forms a constant current source adjustable via POT1. R1, R2, D1, D2 set a voltage on the base of Q3 of about 5.4V and this means about 6V voltage drop over R6 and POT1 series connection. Assuming Ic3 = Ie3=Icharge,

Icharge = 6V/(R6+POT1)

Lets set POT1 at 90kohms for ease of calculation. This gives R6+POT1 = 100k.

Icharge = 60uA

Since Q3 is in saturation mode we can assume a voltage drop over C-E of about 0.5V so the voltage over the capacitor Vc1= 5.5V. The time for the capacitor to be charged to 5.5V is defined by the below equation:

T= (C1*Vc1)/Icharge = 0.91 second

上記の式は充電時間コンデンサを計算します。

Q2 buffers the voltage across C1 capacitor. It also provides a small delay until Vc1 reaches around 0.6V to bias Q2’s B-E junction. Q1 acts as a switch and when turned on via a 5V signal it absorbs most of the current from Q3 and capacitor will not be charged.

Q4 has the role to drive the relay. It is a small power transistor and it’s enabled via POT2. This variable transistor has the role to set the on/off steps based on the ramp voltage. If too low the relay will be on very fast and stay on if too high the relay will never activate.

Speaker delay circuit schematic

Figure 2

In figure 2 the time step is 200ms and we can see the ramp is about 1s long, very close to what we calculated. The blue trace is the Fault signal. When a 5V pulse is present the capacitor C1 is discharged very fast (pink trace) and speakers are decoupled (green trace). When the fault signal goes to logic low or ground the ramp generator shortly starts the process and enables the relay after about 1 second.

Speaker delay circuit schematic

Figure 3

 

Speaker delay circuit schematic

Figure 4

Figure 3 shows how the relay is activated faster if the POT2 is set too low in value and figure 4 shows a correct setting. The yellow trace represents power switched on.

Below you can see the circuit in the right side of the board.

Speaker delay circuit schematic スピーカ遅延回路図

 

Parts list does not contain the connectors in the schematic because the circuit most likely will be used as a part of something bigger:

Part Quantity
BC549 2
BC559 1
BD139 1
1N4001 3
R 12K 5% 0.25W 3
R 10K 5% 0.25W 2
C 10u 25V 1
POT 250K 1
POT 10K 1
RELAY DPDT 1

Thank you for visiting,

ご覧いただきありがとうございます。