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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

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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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.


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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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:
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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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LEPAI 2020A Schematic

Posted 14th December 2014 at 05:14 AM by JOEJAZZMAN

I have built several guitar amps powered by two 7ah gell cells. The tone is fantastic using the Lepai 2020A class T amps. Problem is reliability. Having an amp go belly up in the middle of a gig is disaster.After 4 failures I need to analyze the circuit in detail. Is the chip being stressed to much driving 4 ohm spkrs? A number of questions.Can anyone steer me to a schematic? Is it poor quality components in the circuit? What is going on? Should I find a class D equivalent ? Thanks for any help.
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MJL21194 Transisors: Real, Second Source and Fake

Posted 6th December 2014 at 04:10 AM by googlyone

Over the last couple of decades I have built an awful lot of power electronics stuff, especially power amplifiers.

So I have bought and used a commensurately large number of power electronic devices.

As a young hobbyist this started with salvaging bits from refuse - especially in the late 70's and early 80's larger power devices were far from cheap. This generally worked really well, as I never did really trust what I pulled out of refuse gear, and I tested stuff that I used. (also not the least as data on power devices came from "equivelant devices" books such as the "Towers guide" and if you were really lucky you found a datasheet somewhere (on paper!). no intenet....

Why the digression?

Oddly with the advent of the internet and subsequently things like EBAY:
- I could get all sorts of things that you just could not buy locally in small quantities.
- Unscrupulous buggers out there started...
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Design ideas for Aune M1 DAC card

Posted 15th November 2014 at 02:51 AM by abraxalito
Updated 19th November 2014 at 05:43 AM by abraxalito

I'll outline here some thinking in choosing the major building blocks (aka ICs) for this card - any comments welcome as this progresses.

First up the DAC chip will be the TDA1387 initially. I don't know for sure that the output from the ARM/Xilinx card is I2S but I'm going to verify that fairly soon. There's nowhere near enough room for the passive shunt I've adopted previously so the bass performance probably is going to have to suffer. I shall pay considerable attention to the power supply arrangements though in an attempt to make up for the LF lack.

After the DAC, passive I/V will follow and then a filter using the TDK 7mm inductors I've used previously. I've slotted them into the gap between the PCB and the case and there's just enough height available. Since space is at a premium I'll experiment with a 3 inductor design - the stop band attenuation will suffer but probably I'll add a secondary LC filter at the output to make up for that somewhat. The secondary...
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New .wav player from Aune looks very interesting

Posted 11th November 2014 at 01:26 AM by abraxalito
Updated 15th November 2014 at 09:27 AM by abraxalito

Thanks to jambul for alerting me to this one - 赵宇为作品 - Aune M1 便携式播放器测评报告 [Soomal·数码多] (link is in Chinese but its mainly for the pics).

Notice that although its using the PCM1793 chip the D/A and analog circuits are all on a daughter board. This gives rise to the possibility of engineering a daughter board with a much better DAC chip (think TDA1387) and improved head-amp...

Street price here is around 800rmb (80, $130) so I shall be ordering one to have a play.

Update - looks like I'm rather slow to catch on, Taobao already has somebody's alternative DAC-AMP card, which appears to be selling fairly well, here :

I've now placed the order for the M1, hopefully it'll arrive tomorrow and then I'll follow Dave (EEVBlog)'s advice : 'don't turn it on, take it apart'. The main question I want an answer to is how...
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Posted 10th November 2014 at 10:46 AM by cspirou

This entry probably would have made more sense as my first post.

From my observations it seems like most people persue this from a cost/benefit standpoint. Companies will cut corners a lot of the time in order to control costs. The more expensive products don't cut corners but the result is a higher price. The DIY enthusiast is willing to put the time in that many companies won't in order to get superior sound. No matter what though it seems like the end goal is to have the best sounding system given the resources you have.

Personally though I don't do this hobby as pursuit for the perfect system, even though that is my end goal. I am more interested in building my own system from an educational stand point. My first love has always been science. Figuring out puzzles is what I really enjoy. So while I love music, what I enjoy most are the calculations and the planning involved to make this a reality.

The reason I chose audio is because a lot of the...
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At last, NXP has a low-end, low-power Cortex M4

Posted 8th November 2014 at 01:46 AM by abraxalito
Updated 8th November 2014 at 02:00 AM by abraxalito

NXP's ARM offerings I find to be the most power efficient and I've searched for a long time for a current-sipping M4 which is available in a lowish pin count package. Up until now the best offering in that realm has been STM's F411 with 13mA @ 100MHz. NXP's latest offering the LPC54100 beats that by a healthy margin, turning in a sub-10mA draw at the same clock rate. There's also a dual-core variant with a 100MHz M0+ with around half the current requirement. Respect - the fly in the ointment though is only 2 SPI peripherals which don't support TI mode. Pricing looks great at $2/10k.
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