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Old

ADAU1442 DSP - micro production line!

Posted 4th July 2012 at 02:36 AM by googlyone

I got to the point with my new audio DSP / crossover that I had no more excuse not to load the remaining PCB's I had manufactured.

I initially only loaded one of them, on the basis that if I had a clanger in the layout I could get a new spin of the boards.

Well the thing is all working and I have updated the DAC board - so the remaining five boards needed loading. I find a bit of PCB manufacture and loading to be quite therapuetic - as my previous blog entries will show.

This weekend I found my limit - loading the SMD's for these five boards - by hand in my toaster oven - took about three hours, then loading all the through hole parts, particularly headers and power supply parts blew away I would guess six more hours. I am over it!!!!

They do look pretty though!

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The only part remainig to be loaded on these boards is the ADAU1442 regulstor transistor. Thay will allow me to...
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Old

Musical monitor: And the story continues ...

Posted 4th July 2012 at 02:22 AM by fas42
Updated 16th July 2012 at 12:22 AM by fas42

The project will proceed, exactly as stated in the earlier posts. Just a shame people couldn't help injecting unhelpful comments, and I was provoked into responding. Ahhh, well ...

So, now some peace and quiet! Hopefully at least a few will find something of benefit in what I relate here, and my methods may resonate with some.

Anyway, may all enjoy good listening, no matter what!

Cheers,
Frank

Postscript: Hah! Dumb me, I didn't spot this earlier: [url]http://www.diyaudio.com/forums/blogs/janneman/297-dont-such-scientist.html[/url]. Some excellent thoughts and comments ...
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Old

loading surface mount IC's

Posted 1st July 2012 at 12:21 PM by googlyone

One thing that always used to give me grief at home was loading fine pitch surface mount IC's.

I recently bought a toaster oven having read several people's experience using these to relow SMD's.

I lashed out and bought the el-expensivo fan forced model, as this was in one forum reported to give more even heat. After some playing around I concluded the oven would actually be really very good.

I found that if I did the following (with my oven):
- Turn on and run on 2 bars until temperature = 100C,
- Turn down to one bar, and run for 60 seconds,
- Turn on two bars and continue until the temperature is 210C,
- Turn all bars off, leave fan on and open the door a crack.

The heat continues to increase to about 220, and the profile is really very close to many manufacturers recommended profiles.

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I don't use silksceeens, I use a syringe and put a very little...
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Old

OPTIMUS STA-2160

Posted 29th June 2012 at 07:27 PM by Antoinel

Hello
Does anyone have the schematic of the power amp section of the subject AM/FM receiver? Please share it. Thank you
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Old

Mathematics of DAC droop correction

Posted 29th June 2012 at 05:09 AM by abraxalito

Here's one of the clearest articles I've seen which explains the background and a couple of solutions to DAC roll-off.

Flatten DAC frequency response | EDN

Both the solutions proposed compromise the dynamic range. My own solution, a hybrid analog/digital approach relies on DACs being cheap - I've termed it 'LAID' which stands for 'Longitudinal Array of Inexpensive DACs'.
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Old

Front Panel Express Panels for the O2 Headphone Amp

Posted 28th June 2012 at 04:49 PM by MrSlim

The B2 file is for the BOX Enclosures B2-080 case, that is used in the standard "transportable" O2

The B3 files are for front and rear panels on a BOX Enclosures B3-080 case, used in the "Baby" desktop configuration of the O2. This configuration includes mounting holes for a 1/4" headphone jack and volume control on the front, with all the rest of the jacks and buttons on the back, along with a pair of RCA jacks for input. The PC board in Baby Desktop is installed backwards.
Attached Files
File Type: zip B2.zip (945 Bytes, 184 views)
File Type: zip B3_front.zip (565 Bytes, 177 views)
File Type: zip B3_rear.zip (823 Bytes, 159 views)
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Old

New CS4398 plus PGA2320 DAC board set to work

Posted 25th June 2012 at 01:57 AM by googlyone

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ID:	719Just finished set to work of the new DAC for the digitial crossover. This includes a PGA2320 programmable attenuator on the output of the CS4398 DAC.

This replaces the home made PCB thai I was using on the CS4398 output. I went the professionally made board mainly because PCBCART was able to deliver 16 of these to my house for $140, that includes tooling!!! The actual boards were like $3 or 4 each!

The quality of these baords is fine - though I must admit that I am not breaking any new ground in PCB technology here.

The board is only double sided - I thought about adding a seperate ground and power plance - but the routing density is so lot it would be crazy. The whole back side only has a handful of tracks on it - and is a ground plane in itself. The top side even has room for significant ground fill.

All the digital stuff is in between the connector and the DAC, with a few SPI lines up the left hand...
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Old

Prototype MOS DAC

Posted 23rd June 2012 at 08:22 AM by abraxalito

The prototype is listenable now, but a bit too much background noise/hum pickup to do serious listening. It needs an on-board post filter and amp, which I'm working on now. In the meantime, here's the pics - the DAC itself is built of 5 'dac-sleds' each with a stack of 4 chips. The 'sleds' are then arranged around the central tower holding the resistor ladder. A separate board handles the timing logic and 18 tap delay line.
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Old

NwAvGuy odac 24/96 DAC review

Posted 23rd June 2012 at 07:02 AM by rjm (RJM Audio Blog)
Updated 2nd July 2012 at 04:52 PM by rjm

I cased up my odac board (NwAvGuy via jtktam) in a small aluminum project box.

The DAC is a simple two-chip affair, with a Tenor TE7022L controller fronting the ESS ES9023 DAC and integrated line driver. A couple of voltage regulators, the clock oscillator, and an eeprom chip round out the principle component list.

I compared it with my Onkyo SE-200PCI sound card. This 24/192 (115dB S/N A-weighted, 0.003% THD 0dB 1kHz) PCI card sells for about $15,000 yen and is based on the VIA Envy24HT and Wolfson WM8740.

I'm listening to 16bit 44.1kHz .wav (CD rips), though VLC [sample rate converter set to sinc, best quality, resampling quality 8]. Windows 8 release preview [default format 24/192 (onkyo), 24/96 (odac)]. Line out though Oyaide PA-02TR interconnects to the Sapphire headphone amp, and Sennheiser HD-600s.

**

So, I was planning on writing up a big 'ol review with my impressions, but, well... there's not really a...
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Attached Files
File Type: pdf ODAC-release.pdf (196.7 KB, 808 views)
File Type: zip Odac and Onkyo Comparison.zip (28.3 KB, 387 views)
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Old

modest base requirements for a line stage

Posted 22nd June 2012 at 06:44 AM by rjm (RJM Audio Blog)
Updated 29th June 2012 at 05:38 AM by rjm

Copied from this post, for reference.

Quote:
Originally Posted by RNMarsh
Here are my own modest base requirements for a line stage (similar for power amp):

1. Open loop BW of 40KHz or more (-3dB)... 20KHz min.
2. IM and THD of less than .001% at 1v rms into 30 ohms for any frequency between 20Hz and 20KHz.
3. No coupling caps on input or output or in feedback path.
4. No use of dc servo circuits to track and correct dc offset and drift.
5. No more than 6-8 transistors (excluding power supply).
6. S/N ref 1 volt rms and without weighting of at least -130dB (input can be shorted or terminated).
7. No significant harmonics above the 2nd and 3rd.
8. Closed loop gain between 12 and 20 dBv
9. Low Zout (less than a fraction of an Ohm at any audio freq).
10. Distortion not be changed by source Z.
11. Transistors should be low cost and not be exotic, hard to obtain, very expensive or no longer manufactured.

There might
...
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