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New 12" wide heatsink now available

Posted 19th January 2015 at 03:59 PM by barrredboss

Hello diy'ers! Just wanted to let you know that we now have a 12" wide heatsink available for purchase at our website. Extruded Aluminum Heatsinks from HeatSinkUSA
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Old

TDA1387 octal DAC looks like a good modding base

Posted 15th January 2015 at 11:55 PM by abraxalito
Updated 28th August 2015 at 01:16 AM by abraxalito

Thanks to Matthieu (Malefoda) for the heads up on this. It looks distinctly like a DAC inspired by the DAC-AH - note not only the 8 DAC chips but also the PCB layout closely follows that design's. The price on Taobao is about half the AH (368rmb) so I shall be ordering up one or more to have a play. Matthieu found it on another website with prices in USD, here - http://www.cart100.com/Product/42124644877/.
Note there are two options here (blue, black) - the cheaper one is a kit of parts I believe, the more expensive ($84) the finished unit. Going on the translation of the Taobao page, the kit does not include the transformers, mains switch or the case.

Update : here's the summary of the mods so far, for details go to Malefoda's thread linked in the comments.

1) Re-route the output ground so the opamp filtering caps aren't subject to injected CM noise from the destination component (amp or pre).

2) Reduce the supply voltage to the output opamps...
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Old

MUSES premium audio semiconductors from NJR

Posted 14th January 2015 at 11:29 AM by rjm (RJM Audio Blog)

Have I just been living under a rock or why the hell haven't I heard about this before now!?

http://www.njr.com/MUSES/index.html
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Old

Portable headphone amplifiers

Posted 14th January 2015 at 06:07 AM by rjm (RJM Audio Blog)
Updated 13th February 2015 at 04:11 AM by rjm

The shift of the center of gravity of the high end from component, rack systems to portable continues. Exhibit A

I've also noticed that over the last couple of years the basic blueprint for a portable headphone amplifier as defined by the Sony PHA-1 has now been taken up by all of the major Japanese audio companies.

Sony PHA-1, PHA-2, PHA-3
Denon DA-10
Onkyo DAC-HA200 and TEAC HA-P50 (variants of the same basic unit)
JVC SU-AX7 (report) (seems to be mostly Kenwood DNA)
Audio Technica AT-PHA100
and Fostex hp-p1

For all the above you are looking at a battery powered, slim-cased DAC + headphone amp typically with some sort of guard around the controls. They all feature a good variety of analog and digital inputs, offer switchable gains, and are priced over a range from $200 to nearly $1000.

You are looking at the convenience of having the DAC built in, the small size, and the rechargeable lithium...
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Old

Revisiting mods to the Lite DAC-AH

Posted 12th January 2015 at 01:57 AM by abraxalito
Updated 12th January 2015 at 02:07 AM by abraxalito

Last night the battery of my I2S source ran out so while it was on charge, I unboxed my last remaining Lite DAC-AH to have a listen to that, fed from my (mains powered) QA550 wav player. I'd bought 3 DAC-AHs a few years back when I was playing with them.

The differences between the stock DAC-AH and the Ozone Pagoda were apparent in the areas of soundstage depth, dynamics (especially at LF) and coarseness at higher levels. So this got me wondering what would be the lowest hanging fruit in terms of mods to it. My procedure before had been to implement everything I could think of before having a listen - this way its not possible to know which mods are the most effective ones and which can be omitted.

This time I'm going to be a bit more disciplined for the purposes of discovering which mods deliver the best bang for the buck. The first one I'm going to try is a passive LC filter between the DACs and the AD847s. Here's the schematic for it - its using the cheap and...
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Old

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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Old

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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Old

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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Old

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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Old

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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