For a complete HI-FI amplifier (with EQ and) with the possibility of PCB mount pots is something I have avoided, as are the pots that are available in different parts of the world, necessarily compatible. Due to popular demand, this project has been developed (with a complete PCB) to fill the gap in the creation of the PTA to provide.
The amplifier is very easy to get on the board, and an innovative tone defeat. Rather than disabling the sound system completely, they are massively de-sensitized, and defeated the have a maximum range, . This can be increased if desired, so that you can have two settings of tone, a rising standard of 10 dB and a cut and the other with a very subtle 3dB boost and cut – that’s enough (surprisingly) a very minor adjustments to the way you need for day-to-day hearing.
Otherwise, the design is fairly conventional, with a great advantage over other models that require almost no cable. Transfer of the source is as you want – I suggest you bring a rotary switch on the rear of the enclosure, and a shaft extension with the tree in front. This leads to a minimum of wiring and reduces crosstalk from other active inputs.
Picture 1 - A and tone controls
Circuit Description
The input stage is shown with a gain of 2 times (6dB), configure and also acts as a buffer circuit for tone control. The tone control is a fundamental type Baxandall, but the addition of R117, 118 and 119 provide the flexibility and ease of reconfiguration, which is not the traditional arrangement.
R119 is the hard part of this circuit (which is unique, too
- I have not seen before, this technique is used). As it is 100k, which limits the range of tone control to a reasonable + /-10dB. To increase more and cutting, R119 (R219 and receive) can be omitted altogether. Conversely, reducing the value of a small area, will also, with about 6 dB at 20 Hz and 20 kHz to 7.5dB with 22K.
The sound system (and overall) performance is shown in Picture 2 (in increments of 10% of pot), and it appears that the midrange is hardly affected. This is in contrast with the majority of drawings in which the controls are aligned to 1 kHz, and it is a very audible in the media. For those who want absolutely no use of tone controls, I suggest that the both without tone controls are designed and in line with true minimalist design.
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