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TDA8932 class D amp

Posted 27th May 2014 at 01:39 AM by abraxalito
Updated 16th June 2014 at 02:09 AM by abraxalito

One channel is completed - barring the off-board hexacap shunt - second channel under construction. Then for a comparison with the TDA1521s

Update1 - both channels running now, 160,000uF on each. Bass is tuneful but LF colourations noticeable on piano (Ashkenazy Diabelli Variations). Solution to this is simple - more caps

Update2 - an extra ring of caps around the original hexacaps now, so we're around 250,000uF. Bass is so much better than from the TPA3116 but the HF is more ragged, less transparency overall than the TPA3116. So I'll next try an outrageously decoupled implementation just to check I'm not limiting the chip with poor PSU hygiene....

Update3 - I have over 30 1206 10uF caps per side now as local decoupling - HF problems are slight. Makes me wonder if I use it only on the bass/mid and a TDA1521 for the tweeter duty we might reach audio nirvana.... Looking at the DS its easy to see why the HF's a bit of a mess - the PSRR is about...
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TDA1521 chip amps rock!

Posted 23rd May 2014 at 04:13 AM by abraxalito

Here's my prototype TDA1521 dual mono arrangement - two chips per channel in bridged/parallel, sat atop 400,000uF hexacaps. The neutrality has taken a while to get used to but I'm lovin' em....
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Technics SU-9070

Posted 20th May 2014 at 01:01 AM by rjm
Updated 20th May 2014 at 03:15 AM by rjm

The Technics SU-9070 is a 2U rack mount stereo preamplifier from 1977, matched to the SE-9060 amplifier. The preamp was sold as the SU-9070II in Japan.

The circuit is shown below, for educational purposes.

The power supply regulation is quite elegant, I hope to get to that in a future post. Here, just note that there are separate regulated lines for the MC stage, the input/VAS sections of the MM and line amps, and the output sections of the MM and line amps.
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Posted in The Lab
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Technics SE-9060

Posted 19th May 2014 at 01:04 AM by rjm
Updated 20th May 2014 at 12:58 AM by rjm

There was a series of relatively slim (2U chassis rather than 4U), upmarket audio separates put out by Technics in 1977: the ST-9030T tuner, SU-9070 preamplifier, and SE-9060 amplifier. They are two degrees of separation from the top of the line models at the time, the range went 9600>9200>90x0.

I recently acquired the tuner (more on that some other time) and have the others in my sights.

For educational purposes, the amplifier schematic for the SE-9060 is shown below. The input stage and voltage amplifier was driven from regulated 55 V supplies (Va+ Va-), while the driver stage was powered directly by the rectified DC at about 50 V (Vb+ Vb-) filtered with 18,000 uF per rail per channel.

Note that there were 9060 and 9060II as well as 9070 and 9070II models in Japan, but the export model of the preamp which sold as the 9070 was actually the 9070II rather than the 9070 domestic version. Likewise the SE-9060 shown below (from a European...
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ESI Juli@ analog card interface details

Posted 15th May 2014 at 05:21 PM by 1audio

Attached is a decode of the cards interface connector to allow interfacing to external DAC's and ADC's.

I'm searching for the pins on the big Via chip that indicate the sample rate/master clock frequency. I'll post those when I find them.
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Old

Video Blog#1 Posted

Posted 7th May 2014 at 11:16 PM by Michael Rothacher

Video Blog #1 is posted here:

https://www.youtube.com/watch?v=mWTy...KhQ2ow&index=2
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Old

Ziggurat passive shunt for chipamp

Posted 5th May 2014 at 05:34 AM by abraxalito
Updated 23rd May 2014 at 01:34 AM by abraxalito

Two tiers in order to achieve the lowest ESR - top is using 4700uF and bottom, 15,000uF. Total around 0.8F, 25V.

I plan to try this out first with my TDA8566 but that's limited to 18V so if that sounds promising I'll look for a new chip which can handle the full 25V supply capability.

Update1 : Wired the top tier only underneath my new TPA3116 class D amp board from Taobao. Seems here the dynamics aren't limited by the capacitance on the output stage supply, rather on the analog supply (pin17 of the TPA3116) which goes to an internal LDO regulator. No amount of capacitance on this pin (I went up to 100,000uF) gives the chip the LF dynamics of my class AB amp so I've been off in search of a class D chip which doesn't have an internal reg so might be amenable to a hexacap on its supply...

Update2 - NXP's TDA8932 is on order now - this is a chip which can be DIYed because its in a manageably small SO32 package, so no need to order up an eval board. Over...
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