This page describes TX ATV Transmitter for 23 cm with output adjustable from 100 to 250mW. BA1404 HI-FI Stereo FM Transmitter Be 'On Air' with your own radio station! BA1404 HI-FI Stereo FM Transmitter broadcasts high.
This audio amplifier circuit delivers up to 200 W of top-class quality for loudspeaker from 4 to 16 ohm. Operating voltage is between 24 and 36 V, max 5 A.
AMB β1. 8 Stereo Headphone Amplifier. After acquiring the excellent. HD6. 00 headphones, I realized that the headphone. CD players simply. After auditioning the HD6. I became motivated to design and build a high- quality headphone.
In keeping with my minimalist philosophy in audio, I decided that. Unlike the Headroom Max, there is no crossfeed or filter feature.
There are two sets of input RCA terminals, internally wired in parallel. This is to allow the headphone amp to be inserted into the tape monitor.
Y- cables or adapters. Two output jacks allow simultaneous. I originally planned to use all- discrete components, but decided instead. IC opamps. Op amps were at one time considered lowly creatures not worthy in. However. there are now new devices that offer truly remarkable performance. Combine. that performance with reduced parts count, PC board real- estate savings.
In addition, due to standardized IC pin- outs, I thought it. Most opamps do not work well driving headphone directly. The. output current capability and output impedance characteristics. This is the reason why the headphone outputs on preamps, CD players.
To protect the opamp from. There are "power opamps" with high. I decided to use the opamp merely as a voltage gain stage, and use. This sort of output. Walt Jung's IC Op Amp Cookbook.
Audio IC Op Amp Applications book, and are used. However, rather than the usual bipolar.
I decided to use power MOSFETs, because I have been a. Ever since my good. Hafler power amplifiers from the late 1.
I have been smitten by their excellent reliability, speed, and. Moreover, they are noted. After sketching out a schematic diagram of what I wanted to build.
I came across the. Headwize forums. almost identical circuit to what I designed from. Sheldon Stokes (a.
Sheldon even offers etched and pre- drilled PC boards for sale. I decided to use version 1. Sheldon's board, which made my job easier. This board also includes the power supply section, simplifying. My circuit was largely identical to the SDS Labs. I use somewhat different component values and parts.
I have since made some parts changes to make it more like. SDS design, most of these are to make them fit the SDS board. The following paragraphs describes my amp in more detail. The beauty of this design is in its simplicity and relatively. To this end, I chose quality parts. The power supply features a Amveco toroidal power transformer. International Rectifier 4.
GBU0. 6 bridge rectifier and. It is regulated with. Fairchild LM3. 17. T and LM3. 37. T regulator ICs with adjustable voltage. Bourns 2. 5- turn cermet trimpots. These are adjusted to supply. VDC. The original SDS design was fixed at ±1.
V, but. I needed to reduce this to accommodate the Analog Devices opamps. The voltage regulator ICs. There is 3. 7,6. 00µF worth of Nichicon and ELNA low ESR electrolytic. Two of these capacitors are mounted on the chassis rather.
There is more current reserve here than many power. The IC opamp is a dual unit, and is socketed to be easily swappable. So far I have tested with the following list. The first four are. I also tested for comparison purposes.
I will try other opamps. See the data sheets of these. Analog Devices AD8. AR. (Fast. FET™, 1. V/µS SR, 1. 15. MHz GBP). Analog Devices AD8. AR. (JFET, 6. 0V/µS SR, 2.
MHz GBP). Texas Instruments/Burr- Brown OPA2. PA. (FET, 2. 0V/µS SR, 8. MHz GBP). Texas Instruments/Burr- Brown OPA2.
PA. (FET, 2. 0V/µS SR, 8. MHz GBP). National Semiconductor LM6.
IN (bipolar, 3. 00. V/µS SR, 1. 00. MHz GBP). Signetics/Texas Instruments NE5. AP (Bipolar, 9. V/µS SR, 1. MHz GBP). Texas Instruments TL0.
CP (JFET, 1. 3V/µS SR, 3. MHz GBP). NTE 8. 58. M (JFET, 1. 3V/µS SR, 4. MHz GBP). NTE 8. 89. M (JFET, 6. V/µS SR, 2. MHz GBP). NTE 7. 78. A (Bipolar, 0. 5.
V/µS SR). The two Analog Devices opamps have SOIC- 8 (surface mount) package. They are each mounted to a SOIC- 8 to DIP- 8 adapter. One concern about using opamp ICs is the power supply voltage. V for the Analog Devices units. This restricts the maximum available output voltage swing, which may.
However, upon. testing with the HD6. I found. that this amplifier provided enough voltage output to achieve very loud. If using headphones with much higher.
I recommend using. V or more of supply voltage. An important modification from the "stock" SDS Labs.
R1. 2/R6. 2 resistors, and the substitution. R1. 0/R6. 0 with 4. A CRDs (current regulating diodes; the Vishay- Siliconix.
This is simple and does not require altering the. PC board layout, but should only be done if the output devices are.
MOSFETs. It is not appropriate with bipolar output transistors. The modification has several important benefits. The opamp is now biased to source 4.
A of current at its output. A. This is regulated. CRD, and is the entire amount of current flowing through the. Vbe multiplier. (In the original design, the opamp may sink a small. It is rather ineffective at keeping the opamp. A. With this circuit change, the current is.
Sourcing current out of the opamp is usually better than sinking. NPN transistor in the opamp's complementary.
PNP. transistor. The NPN is usually more linear. If you want to. make a similar modification to your SDS Labs amp, but want the.
R1. 0/R6. 0 and substitute R1. R6. 2. with the CRD). Having a steady and regulated amount of current flowing through. MOSFET biasing section improves the circuit's ability. MOSFETs. This is because the MOSFETs' gates are.
The power supply rejection ratio (PSRR) of the output buffer. This is perhaps the. An additional NP0 multilayer ceramic decoupling capacitor is added and. Overall voltage gain is set to slightly less than 5 (1. B), different. than the original SDS design which has a gain of 2 (6d.
B). With some. high impedance headphones the original gain is not sufficient to achieve. At this gain. comfortable listening levels can be achieved with most line input devices.
Sennheiser HD6. 00, while the volume control is near center. The original Harris RFP1.
N0. 5/RFP1. 5P0. 5 power MOSFETs specified have. Some SDS builders used the Hitachi/Renesas 2. SK2. 13/2. SJ7. 6. Harris and International Rectifier devices. While the 2. SK2. SJ7. 6 have. low input capacitance (which is desirable), they have low transconductance. A). Moreover these.
USA. I chose to use the. IRFZ2. 4N (N- channel) and. IRF9. Z3. 4N (P- channel) power MOSFETs. International Rectifier.
These are 5th- generation HEXFET™. Newark Electronics. The MOSFETs are biased to run with 8. A of quiescent current.
Vbe multiplier. based on a Motorola 2. N5. 21. 0 small- signal NPN transistor, and.
Bourns cermet trimpot. The MOSFETs and voltage regulator. ICs are cooled by AAVID/Thermalloy extrusion heat sinks. The MOSFETs each dissipate. The heavy bias causes the output stage to operate in class A. This operates the output MOSFETs in their "sweet spot". All resistors are precision metal film units, most of them.
Vishay- Dale RN5. HF compensation are via NP0 multilayer. NP0 multilayer ceramic capacitors from. Vishay and Kemet.
This assures stable operation of the voltage regulator. ICs and a low power supply rail impedance over a wide frequency band. The amplifier is direct coupled at the input and output, as well as.
The inputs feature Vampire RCA jacks, the outputs are via. Neutrik locking phone jacks. These all have gold contacts. The volume control is a high quality stereo potentiometer from Noble. The IEC AC power entry and switch module is from Corcom, and there is an.
LED power- on indicator on the front panel. The chassis/enclosure is home made. The base is aluminum, and is. The side walls. are black glossy acrylic, the front and rear panels are clear acrylic. The top cover is clear acrylic with a cutout to. Virtually all fasteners are socket head.
The enclosure was much more time- consuming and took. I think the. result speaks for itself. Attention is paid to the internal wiring to ensure that there is no. The aluminum base plate is connected to the signal ground.
All wiring are. twisted tightly into pairs where appropriate to improve noise induction. I did not use silver/teflon or other.
I do not believe that the short runs within the amp. I added inline. Molex KK series modular plugs to all lines leading to the main circuit. Heat- shrink tubing is used to cover all soldered connections at the.
In essence, what I built is a small power amplifier specifically for. As such, it has very low output impedance. Even though I tested with some opamps with bipolar inputs, they should.
The high input bias current of the bipolar opamps causes unacceptably high. DC offset, and it varies considerably as the volume control setting. With the FET opamps, the output DC offset is less than a.
The broadband noise. AC mains noise. likely to be magnetically- induced due to the proximity of the power.
PCB layout. This is one area of the amp that could use some improvement. The compensation capacitor values are "tuned" here for best.
AD8. 06. 6AR. With this opamp. With certain other opamps there is a very small but well.
This can be tuned- out by increasing the compensation. I opted to leave things as is because. I found that the AD8. AR opamp provides the best sound.
AD8. 06. 6AR measures slightly better in terms of. The OPA2. 13. 2PA and OPA2. PA perform well, but with.
I personally did extensive listening comparisons between this amp and the. Headroom Max and the.
Moreover, at a recent local Head- Fi gathering. A- B style listening comparisons to a fully- loaded. Meier Audio Corda HA- 2. Ray Samuels Audio Emmeline HR- 2, and other.
It validated that this amplifier could stand amongst the better.