New answers tagged

1

Just build an attenuator. simulate this circuit – Schematic created using CircuitLab If the sourcing amplifier is bridge mode, use spkr OUT+ and GND, and ignore spkr OUT- Attenuator component values are fairly non-critical, values shown are a reasonable starting point. If it's too quiet, double R1.


1

There are a few potential problems: The output of the Sonos will be several volts. The input to your powered speaker will be < 1 V max and exceeding this will result in clipping distortion. Turning down the volume of the Sonos will prevent the clipping but since the volume control will precede the power amplifier the hum and noise from the Sonos ...


1

The oldschool Vactrol uses an LDR which is a light dependant resister .The light source can be a led but in the old days it was incandescant like 6.3Volt 0.3 amp .The LDR is very linear and can take rather high voltages .Old large ones would take 100 Volts .This means that noise pickup was not a problem .Unfortunately these LDRs were made of Cadmium Sulphide ...


1

The vactrol works as a gain-setting element for the op-amp. Gain will be 1+R15/R(vactrol). The more the LED light, the lower R(vactrol), and the higher the gain. Another way to do this is to use a voltage-controlled FET as an attennuator. Here is an EDN article describing how to do that: https://www.edn.com/a-guide-to-using-fets-for-voltage-controlled-...


0

You can't hear 0 to 200Hz. It would need to be modulated on a carrier. A SSB low power transmitter on one side and SSB receiver on other side.


0

A loudspeaker and a microphone. For 200m reach you probably also need a semi-decent amplifier. You would hear annoying tones, but it fulfills all of your 4 above requirements


3

In many of these old-school devices the motor speed was controlled by a centrifugal governor on the rotor of the motor, so faster was not an option only slower. I built this: it worked well enough to be a fun toy: simulate this circuit – Schematic created using CircuitLab it just plugged into the 'Cue' socket (J4 REM on your schematic) placing it ...


2

Hopefully you know that this is an intercomputer data transmission line interface, it sends and receives serial data stream which is inputted and outputted by a serial data port of a computer. The datasheet http://pdf.datasheetcatalog.com/datasheet/nationalsemiconductor/DS006750.PDF claims several kilobits per second are transferrable, but the actual ...


0

The old school recorder is designed to run on four 1.5 Volt dry cells or a simple unregulated mains transformer .The nominal 6VDC motor is designed to give small speed variations for large voltage variations .This means that reducing motor volts using a 100 ohm wirewound pot or any other means will not give good results .Consider changing the ...


0

This motor in the lower right corner is connected directly to the 6V supply on top right, so there is no speed control.


1

Ok, firstly I think that switching circuit is going to click, no matter how many caps you scatter around, simple charge injection in the cmos switches will see to that at the impedance levels you are running there. The trick with coupling (as opposed to filter) caps is to keep the AC voltage across em negligible, which is to say make them large compared to ...


0

Is the detection too slow? Do I have an error in my schematic? Using Arduino as a DC voltmeter here should work since all the DC voltages are within the range of 0V to +5V. Ensure that the path to the Arduino input is DC-coupled (no intervening series capacitors). Since Arduino's analog-to-digital converter is a sampling type, it could be too fast. When ...


2

The "proper" way to do this, as you asked, is to use an audio transformer per channel. Pricey though. The way we've got round this on a PA installation I operate is to use unbalanced auxiliary outputs to drive the power amp. The main outputs on our mixer (a Yamaha MX12/4) are balanced XLRs so we use two of the unbalanced 1/4" group outputs to drive the (...


1

It depends if you have a true balanced output. If you do, grounding the "cold" line is OK. If you don't, Tony's answer is better because it avoids the short on the "cold" (ring) to gnd. If the mixer only has jack (not XLR) outputs, I'd doubt it's to full professional standards, so read its manual carefully. (OK it does have XLR ... still, its manual ...


1

(Added) It depends if sleeve = Pin 1 is a supply, shared or floating Gnd. If unsure; Use either Pin 2 or 3 for each L/R channel but use same pin # to be in-phase. Do not short pin 2-3 on XLR, otherwise audio will mute (cancel)


0

I know. It's too late. I also tried class D amps. What i understand is the filter inductor is not capable of passing that much current though it without core saturation. when you add 0.68uF capacitor after inductor, huge current is passed through the LC network because most of the supply voltage (high frequency component) appear across inductor. inductor ...


1

How many minutes in total are above 60 dB? You can't tell that from the graph alone. Loudness can change many times in a second, and one of the pixels in your image is 24 seconds long – and you're not specifying whether "minute above 60 dB" means that a single instant in that minute was above 60 dB, or the average loudness in that minute, or somethingelse....


-1

If you don't need much current, it's not too difficult to make the -10 rail from the +10 one using a circuit called an inverting buck DCDC. That would be easier than trying to convert your bipolar design to single-ended, though that could be done as well. EDIT: ok, 40W, so a good-sized supply. I suggest a pair of 12V switchers, with floating outputs, re-...


1

It's not a good idea to replace the voltage levels that a system is expecting. Unless you're modding the synthesizer to accept your GND, 10V and 20V. Audio systems generally have a bipolar supply because it's necessary for the opamps inside to properly amplify an AC signal ( you can't amplify a negative voltage if your supply only has a positive rail). ...


0

I just made a Bluetooth connector for the aviation headset. I used 100 ohm on both and it seems to work just fine I can still hear everything just fine. I might try to go down to 10 ohms for the line coming in and keep the Bluetooth at 100 since it is really loud without resistance.


1

The maximum you need is an amplifier designed to drive an 8 ohm load with 120 watts continuous and 150 watts peak. The load on the amplifier will be 8 ohms, given two 16 ohm speakers in parallel. How much power you actually need depends on the space you are trying to fill with sound. In a large hall, 120W may be appropriate. In a small room, it will be ...


0

Do the math. 10uF into a 32 ohm earphone cuts frequencies below 500Hz. 100uF cuts frequencies below 50hz. 220uF cuts frequencies below 23Hz.


0

Sounds like a ground loops and or a missing output capacitor. When the bluetooth module stops playing for x seconds, it turns off its output, so it stops actively driving the output jack. So the line starts floating and picks up the noise from the charging module. You can try a 10 uF ceramic capacitor in line/series on each of the left and right output, to ...


1

Depending on how much current you need, and how well balanced the load is there are several solutions. The easiest to implement is probably using TI's TLE2426 'rail splitter' which will give you a +/- and a virtual ground. If the output current from this is insufficient it can be buffered with something such as a BUF634 (eye wateringly expensive) or a ...


9

What purpose do the 22pf capacitors serve? Audio mixers can have many inputs sharing the same virtual earth at the op-amp Vin- input (see pin 6 of the TL084 below). This adds a lot of parasitic capacitance (purple box above) from Vin- to ground and creates a peak in the amplification of the op-amps internal input noise: - Engineers refer to a phenomena ...


6

The 1Kohm line out resistors also reduce reverse-EMI distortion, with the EMI/RFI passing from the opamp Vout ---- through the 22pF Cfeedback - to the summing node. I first read of this phenomena --- where radio frequency energy on the OUTPUT WIRES is conducted backward thru the feedback network --- in discussion of "how to improve the performance of your ...


17

1) The 22 pF capacitors improve stability. A mixer sometimes drives a fairly long cable, which appears as a capacitive load, which can cause opamps to oscillate. So the 22 pF capacitors improve phase margin. They also reduce gain at high frequencies (well above the audio band) which can help in electrically noisy environments (radio transmitters, studio ...


0

Looking at the block diagram, the input jacks are unbalanced, with the third terminal being a switch contact to the tip. The switch contacts connect to RCA jacks on the rear panel, which will be disconnected when a plug is inserted in the front jack. The tip contact is the "V" at the end of the top line of the jack, and the switch contact is the upward-...


1

Concentrate on one of the stereo outputs first, say left. You want, at one extreme for it be be the left input signal whilst at the other extreme you want it to be the right input signal. So, you need two voltage controlled amplifiers (VCAs) that can attenuate a signal to nearly nothing and those two VCAs need to operate oppositely to each other such that ...


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