# Tag Info

1 vote
Accepted

### Questions about center-tapped transformer for tube amplifier (MC 275)

I'm answering my own question so that people who ask a similar question in the future can use my answer as a reference. Most of full-wave rectifier example uses either (1) a transformer w/o center-tap ...
• 301
1 vote

### Boost Voltage of Signal Generator Output (via Audio/Signal Transformer?)

Audio transformer is a good solution if it doesn't matter that output amplitude will vary based on frequency and load. For stable output, a high voltage opamp would be good solution. It also has the ...
• 5,008

### Boost Voltage of Signal Generator Output (via Audio/Signal Transformer?)

Your turns ratio of 20 is pretty high... A standard power supply transformer most likely won't have the bandwidth. You can always try with a 110V:5V transformer, they're cheap enough for quick ...
• 61.8k

### Boost Voltage of Signal Generator Output (via Audio/Signal Transformer?)

Where can I get more info on turns ratio (as I cannot derive the turns ratio from the impedance ratio)? If you have a step-up turns-ratio of $1:N$, the output voltage, $V_O$ is: - $$V_I\times N$$ ...
• 389k

### Boost Voltage of Signal Generator Output (via Audio/Signal Transformer?)

In a theoretically perfect transformer, the impedance ratio is the square of the turns ratio. This is confirmed by most of the datasheets you linked. A turns ratio (voltage multiplication or ...
• 13.2k
1 vote

### Why do tube amplifiers have such (relatively) small reservoir capacitors?

There are two main engineering reasons you see small reservoir caps in tube amps: In the Before Time(tm), i.e. when tubes weren't obsolete, a 47uF reservoir cap was an expensive and massive beast. ...
1 vote

### Mono audio amplifier repair help (Harman Kardon HK775): resistors getting hot

You can calculate what the power dissipation should be from the voltages and resistances shown on the schematic. $$P=\frac{E^{2}}{R}$$ For example R441 and R442 are shown as 12k, 1/2 W resistors. They ...
• 5,198
1 vote
Accepted

### How does the feedback in this tube amp output driver work?

What's hard to tell from the schematic, is the phase and ratio of the transformer windings. The YEL and ORN windings are all common to the output transformer (BLU). The phasing, I think, is consistent:...
• 5,118
1 vote

### Controlling mode of operation for TDA8948J audio amplifier

I encountered same problem with my Philips Micro Theater MCD122 which use same audio amp IC. My problem was intermittent sound from left or right speaker randomly. When I check Mode voltage it was ...
• 11
Accepted

### Audio frequency response over Bluetooth

The vendor is clueless. Ignore their recommendations. Binaural beats generate the beat in your mind. They use audible sounds that are close together in frequency (say, 1000 and 1005 Hz.) Your ...
• 59.8k
1 vote

### Audio frequency response over Bluetooth

Binaurals are usually created by using two frequencies differing by (in this case) 5Hz. Each frequency is fed into a different ear. It only works with headsets. Having said that, the two frequencies ...
• 12.2k
1 vote

### Audio frequency response over Bluetooth

Bluetooth audio is compressed in order to fit into the very limited available bandwidth. As part of the compression process, the encoder uses a model of human hearing to decide what to transmit and ...
• 10.7k
1 vote
Accepted

### Simple transformer construction help

You need to match the impedance of the crystal radio, to the impedance of the phones, for maximum audio signal transfer. Depending on its design, the impedance of the crystal radio could range over ...
• 11.1k

### Simple transformer construction help

There's two things that are killing you here: First, an earbud is not an efficient transducer. For a crystal radio you need a transducer (i.e. piezo earphone or old-style high-impedance headphones) ...
• 37.7k
1 vote

### Simple transformer construction help

A ferrite bar has a great deal of leakage inductance, and makes a poor transformer at audio frequencies. You need much higher inductance to get sufficient impedance to match the output of your crystal ...
• 1,121

### How does the attack / release element of this audio compressor function?

Question 1: Q4 and Q9 provide an adjustable bias to Q5 such that Q5 injects a constant current into D6 and D7 (don't forget they are PNP transistors so the relevant voltages are relative to V+). At ...
• 29.7k

### Relationship between volume control position and signal voltage

Here's how I measure it. I used: an ItsyBitsy M4 microcontroller's 3V pin to provide a fixed 3.3VDC which served as a "signal", a Fender S1 potentiometer as a volume control the Itsy's A4 ...

### How to calculate the input impedance and transfer function

Please label your components in future. It would make answering so much easier. Here's my version of your circuit to simplify things: simulate this circuit – Schematic created using CircuitLab ...
• 9,233
1 vote
Accepted

### Single transistor VCA for gate type CV signals

Try muting circuits: https://sound-au.com/articles/muting.html Note the catch with unbalanced switches or mixers: the bias current flows into the signal path. Your example does, in fact, (nearly) ...
• 5,118

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