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DIY ES9018 DAC + LM4780 AMP

Posted 6th January 2015 at 11:30 AM by Maciej Czerwinski

Finished, front:
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back:
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what's inside:
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This device is built around DIYINHK ES9018 DAC board, with USB to I2C CM6631 converter, also from DIYINHK. USB is the only signal input. Power amplifier uses two LM4780 chips, one per channel in mono-parallel configuration. Power supply for the amplifier is made out of two HP printer power supplies. DAC power supply is more complex, but also uses three, a little bit modified, 12V supplies, wall plug in type, general use ones. Volume regulation (attenuation to be exact) is entirely digital, provided by ES9018 dac chip. It is controlled by PIC16F84 microcontroller via I2C. There is also 3-digit attenuation level display and rotary encoder is used for setting the attenuation level. Details are described in next posts.
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DIY ES9018 DAC + LM4780 AMP Details part 1

Posted 6th January 2015 at 11:30 AM by Maciej Czerwinski

DAC:
On the DIYINHK DAC board we can find ES9018 chip and ADP151 1.2V linear regulator (VDD) factory soldered. You have to populate the rest of the board yourself. I have soldered:
- ceramic and electrolytic noise filtering bypass capacitors,
- various resistors, mostly in the I/V stage,
- I/V stage op-amps (4xAD797)
- output signal low-pass filter capacitors.
The board is designed for 6 op-amps with SE output. I wanted differential output, so I have done some modifications, following the ES9018 demo board datasheet.

The I/V stage and power amp schematics (one channel):
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When the main power is switched off, the relay shorts the power amp inputs in order to avoid oscillations, generated by I/V stage during discharge of its power supply bypass capacitors, to pass to the power amp.

A/V stage section of the DAC board – one channel, ES9018 chip side (top side in my case)....
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DIY ES9018 DAC + LM4780 AMP Details part 2

Posted 6th January 2015 at 11:29 AM by Maciej Czerwinski

POWER AMPLIFIER:
It works in parallel configuration in order to drive 4 ohm speakers easier. Such configuration has quite low input impedance, around 5kOhm, and low gain of 3.7. This, with the 3x20k input signal resistor divider, gives the maximum output power of only 1W for single sine.
The two pairs of 100k, multi-turn potentiometers set the symmetry of each amplifier. It has to be adjusted manually. In order to do it, you have to supply in-phase (single ended) signal to the input of each amplifier and turn the potentiometers until the signal at the output of each amplifier drops to zero (or rather goes below the noise floor). Unfortunately it also affects the voltage at the amplifier output. There is a lot of trial-and-error work needed to achieve zero signal and zero volts at the output. It is good to do it separately for each of the amplifier from the pair by unsoldering output 0.1 ohm resistors. Signal generator and frequency spectrum meter comes in handy for this...
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DIY ES9018 DAC + LM4780 AMP Details part 3

Posted 6th January 2015 at 11:29 AM by Maciej Czerwinski

POWER SUPPLIES
Power supply for the amplifier is made out of two HP 0957-2093 printer power supplies (32V, 2.5A output), removed from their original plastic boxes and fastened together with metal bolts, nuts and plastic isolating spacers. This way they form one unit, producing +32V and -32V needed for the LM4780. Additionally there are two banks of six 1500uF/35V low ESR noise bypass capacitors in parallel at the output of the power supply. They greatly reduce switching noise, which has a peak at a frequency of around 30 kHz. There are also four 2200uF/35V caps soldered directly to the amp boards.
I have chosen the switching mode power supply instead of a classic 50Hz transformer because. SMPS is lighter, smaller, voltage regulated, requires less decoupling capacitance, does not produce any audible hum or spurious magnetic field around it . It’s main disadvantage is production of HF noise, but, as I am going to show later, it is not a big issue when the output is properly...
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DIY ES9018 DAC + LM4780 AMP Details part 4

Posted 6th January 2015 at 11:28 AM by Maciej Czerwinski

The post-regulation schematics:
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ThreeTHX203 SMPS boards soldered to the main power supply board. There are also additional 230V input filter, output bypass caps and gyrator’s TIP122 visible:
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The other side of the main board – LT1763 regulators, 5V main power daughterboard with heatsinks:
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Details of the 5V main power daughterboard. The top heatsink is for the LM1763, the two on the bottom are for TIP122 (gyrator) and LM7805 (5V for volume controller):
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ADM7150 3.3V regulators on separate board with Rubycon ZL 4700uF/6.3V low ESR bypass caps (board bottom):
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(board top):
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This photos show the how dac power supply is mounted inside the housing:
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DIY ES9018 DAC + LM4780 AMP Details part 5

Posted 6th January 2015 at 11:28 AM by Maciej Czerwinski
Updated 6th January 2015 at 11:36 AM by Maciej Czerwinski

Graphs showing the dac power supply output noise. You can see the SMPS switching frequency noise peaks at 26kHz and 32kHz. Their frequency rise a little when more current is drawn from the supply. It seems that the dac playing 1kHz is an example of the hardest load to regulate for the supply:
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VOLUME CONTROLLER:
It’s a PIC16F84 running a program written by me. It reads rotary encoder and accordingly writes values, via I2C, to the ES9018 attenuation registers. It writes single value to all 8 registers every tick of the encoder. After 10 seconds of no encoder activity, it stores the value to the internal EEPROM of the microcontroller.
The controller board has its own 3.3V regulator, the display board has 1.8V regulator for LEDs
The display module is a separate I2C dumb reader. It catches the attenuation values transmitted...
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DIY ES9018 DAC + LM4780 AMP Details part 6

Posted 6th January 2015 at 11:28 AM by Maciej Czerwinski
Updated 6th January 2015 at 05:18 PM by Maciej Czerwinski

HOUSING:
Typical steel box consists of four pieces bolted together. Dimensions: 440 x 100 x 255 mm (W x H x D). Notice the "Acqua di Gio" volume knob

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Bottom piece. I made two holes to let air flow through power amp heatsinks. There are corresponding holes in the top piece. The black plastic pieces are heatsink mountings:
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Top cover and side walls form one piece. I glued same aluminum mesh into heatsink airflow holes in order to protect the inside of the housing.
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Detailed view of front piece inner side. Display protecting glass cut out of old picture frame and painted with red transparent paint. Total DIY:
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MEASUREMENTS:
Output of the power amplifier loaded with 3.9Ohm resistor, connected to Left line input of the E-MU 0202 with two 10uF unipolar electrolytic caps. E-MU...
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New year, new DAC

Posted 31st December 2014 at 07:36 AM by abraxalito
Updated 3rd August 2015 at 12:50 AM by abraxalito

Here's the 'Ozone desktop pagoda' DAC for 2015.

A single TDA1387 feeds a 3 inductor quasi-elliptic filter followed by AD8017s as buffer-amps. The large ferrite cores in the base do the bal-SE conversion. The power supply is 4 * AA NiMH cells which should in theory last for a whole day's music.

The design is really a 'MkII' version of the Ozone portable where the AD815 buffers have been replaced to allow a more compact construction and lower power draw without the constraint of being able to drive IEMs directly. Whereas the portable used a stack of 1387s due to the choice of 7mm TDK inductors, this one's using pot-core chokes giving a much higher working impedance and hence higher output levels from just the one DAC chip. The desktop footprint is about that of a CD.

Update : I found some bargain Jamicon caps on Taobao which give the tower more elegant proportions, as well as improving the supply impedance to the buffer-amps and giving more breathing...
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Vertical Deflection PAs

Posted 24th December 2014 at 09:51 PM by Miles Prower

TV developed from B&W viewed on small electrostatically deflected CRTs, like o'scope CRTs. Screen size wasn't over 7".

Next came electromagnetic deflection, and bigger screens. At first, small signal triodes like the 6SN7 were up to the task of driving vertical deflection coils. Bigger screens and wider deflection angles meant for more demanding vertical deflection duties. This led to a hardened 6SN7GTB with grid radiator wings, a higher plate dissipation rating, and the characteristic extended into Vgk > 0 territory.

Low-u power triodes eventually gave way to power pentodes for vertical deflection duty. Some of these types look like good audio finals. Unlike the HD types, these can use impedance match ratios more like audio finals, so stock OPTs can be used.

10JA5

Click the image to open in full size.

This is a singleton power pentode with some excellent loadlines. It also doesn't have the top...
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Rating: 3 votes, 4.67 average.

Using the QA400 Tips

Posted 18th December 2014 at 04:38 AM by SyncTronX
Updated 21st December 2014 at 07:52 AM by SyncTronX

For those of use that use the QA400 FFT,
here are some tips that will help us use the
product and software for measurement.

Press the Ctrl key plus an Axis, Windowing, or Measurement soft switch parameter.

For example, PRESS Ctrl + .dBV brings up a
dialog box to set External Gain & Peak Display Format:
Click the image to open in full size.

Ctrl + .dBr brings up the following:
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Ctrl + .X Lin:
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Ctrl + .X Log:
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The Measurements soft switch parameters as follows:

Ctrl + .Pwr:

Click the image to open in full size....
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