diyAudio - Entries for February 2013
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Line input RF reject filter

Posted 19th February 2013 at 08:24 AM by abraxalito
Updated 26th February 2013 at 04:09 AM by abraxalito (Added zoomed passband plot)

I've only simmed this so far, no listening tests. The aim here is to have a passive filter which works into a line level impedance (i.e. 10k or greater) and which gives a decent amount of RF rejection without compromising SQ. I plan to incorporate it behind the RCA input jacks of my chipamp.

Design-wise, it started life as a simple 2nd order filter with single series L and shunt C. But when it came to wind the inductor I didn't have a wire diameter small enough to make the required value (44mH). So I split up the inductor into 2 * 22mH and then couldn't resist hanging a cap off the centre tap. The result has turned more into an over-damped elliptic with a higher corner frequency than the original, but with an impeccable phase response to 20kHz. The elliptic-type plot comes about because of the SRF of the two inductors (around 350kHz).

Since fas42 remarked on the phase performance, I've added the group delay plot for the passband. Almost pure time delay of...
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diyAudio Member
Posted in Power chip amps
Views 1546 Comments 8 abraxalito is offline

FE126En Factory Reflex, a "cruel joke"

Posted 8th February 2013 at 09:14 PM by planet10

The subject of this box has come up before, after a 3rd reply to queries, this blog post,

Click the image to open in full size.

One of 2 Fostex factory recommended cabinets. 10.5 litre tuned to 61 Hz. The other is not very good either.

From the sims you can see that with this box any bass response you have will be way down which will exaggerate the FE126's forward midrange and the 7k peak.

Click the image to open in full size.

The top curve is half-space (ie what you would get if you mounted them flush in a wall or approximately what you would get with BSC added). The lower curve is with no filters and a simulated 6 dB of baffle loss. You would need a 2-stage filter to give any semblance of flat response. You would lose some 12 dB of sensitivity and then you run into the very low xMax which means that for...
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Posted in Uncategorized
Views 1470 Comments 0 planet10 is offline

The Red Baron DAC Module V4.0 - Out of production

Posted 8th February 2013 at 09:34 AM by dvb projekt
Updated 19th June 2013 at 11:26 AM by dvb projekt

The Red Baron

Click the image to open in full size.

The evolution brings the following changes

- Separate I2S-GND route to Digital-GND
- Separate Analog Output GND route
- Separate GND route for active divider decoupling caps to Analog-GND
- Modified active divider decoupling pads for better SMD 1210 caps soldering
- Onboard SOT353 footprint for fastest DEM-Synchronizer ICs
- Un-interrupted ground plane
- MOSFET Source/Drain failure corrected

Still on the module

- Direct shunt voltage inputs with shortest onboard traces
- I2S In-/Outputs with shortest onboard traces
- I2S Attenuator and DEM Synchronizer
(by -ecdesigns-)
- Onboard Grounded-Gate MOSFET Current Buffer I/V Stage
(-ecdesigns- MK7 version)
- Separate GND-Trace for DEM-Synchroinizer
- Master/Slave
Attached Files
File Type: pdf Red Baron V4.0.pdf (593.7 KB, 531 views)
File Type: zip TDA1541A Project - BOM - for The Red Baron (9.3 KB, 199 views)
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Views 2372 Comments 0 dvb projekt is offline

Phonoclone boards, soldering, and Q1, Q2.

Posted 7th February 2013 at 06:34 AM by rjm

This is in response to several recent emails I've received, where people were having problems with, typically, one board having a bad V+ or V- regulated voltage output.

The number of cases relative to the number of boards shipped caused me to worry that a manufacturing error might have occurred, so at my request I had a customer return the phonoclone boards he had built to me for inspection.

I'm happy to report that the problem was traced to poor soldering technique, the boards themselves are fine. What had happened was solder had cooled before the component had fully settled, and pushing the component down to the board surface then tore the trace away from the bottom of the board, breaking the circuit.

Subsequently, thinking the transistors blown, he replaced them, doing a fair bit of damage to the pads of Q1, Q2.

Fortunately, I was able to fairly quickly set everything to rights, and the boards are now on their way back to him....
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Views 654 Comments 2 rjm is offline

Another Ikea Bowl Speaker

Posted 3rd February 2013 at 12:04 PM by googlyone

I stumbled on the people making speakers from the Ikea bowls. It kind of inspired me as the speakers were truly different and bizarre, but at the same time something completely different.

So I had to make some.

I fumbled around in the cupboard and came up with three choices of woofers that would do OK in a small enclosure - and after a few measurements and stuff settled on a pair of old Vifa M13SG-09-16 drivers. These were pretty well suited to an enclosure of a bit over 8 litres.

This drove me to the larger bowl, a 28cm one.

This is how they came out...

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To fit the driver I simply routed a rebate - and then cut the inside out.

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The material of the bowl was quite thin once I had finished routing things - so I cut out a circle of ply and glued it to the inside of the bowl. I had to go out for the evening at that point so I simply...
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Attached Files
diyAudio Member
Posted in Uncategorized
Views 4191 Comments 1 googlyone is offline
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