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Wide-band RF filtering for mains - part III

Posted 18th February 2011 at 04:19 AM by abraxalito
Updated 2nd March 2011 at 11:09 AM by abraxalito

OK, slight change of plan. Due to a ****-up on the ordering front with the iron wire, I ended up with some wire which is a bit too thin (0.5mm inner diameter) as they specified the outer diameter on the ordering page, rather than the conductor diameter. On reflection of course, that makes perfect sense since this isn't wire for electrical purposes at all, what use is the 'conductor' diameter? Wire with an external diameter of 1.8mm's on its way, which I hope will have ~1.2mm diameter conductor.

So, in the meantime I've been experimenting with wire I have been able to get hold of, which is shiny steel. It turns out that only 30 paces from my home is a hardware store which sells it - so I've tried winding chokes with it, just to see what happens. I've also acquired an LCR meter to see what kinds of values I'm getting at different measuring frequencies.

The first pair of chokes I wound with some really thick stuff - 2.8mm. Having aimed for 20 turns...
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Rating: 3 votes, 3.67 average.

Flush Cut Your Cable Ties!

Posted 17th February 2011 at 03:44 PM by Boofers
Updated 25th March 2011 at 12:42 PM by Boofers

If I could pass one piece of knowledge onto every person in the electronics industry it would be this: always flush cut your cable ties. I am tired of having my forearms sliced up by sharp cable ties every time I reach inside a piece of equipment. So remember, safety first, cut your ties flush. Besides, flush ties just look nicer.

Click the image to open in full size.

Click the image to open in full size.
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Wide-band RF mains filtering - part II

Posted 14th February 2011 at 04:24 AM by abraxalito
Updated 2nd March 2011 at 11:10 AM by abraxalito

I've been actively researching via Google on this project since the last posting and found out a few interesting things which I'll share here.

Firstly I checked out piano wire as the material for making the L1 & L2 input side chokes in my original schematic. I couldn't find any consistent figure for what the permeability of piano wire is - it seems steel comes in so many variants that its hard to tell. So I continued to look for alternative materials which have reasonably high permeability. Remember, its the high permeability which gives rise to skinny skin depths and hence higher losses as the frequency climbs. Normally this is really undesirable, but for our purposes its exactly what we're looking for.

Other elements which have high permeability include nickel, cobalt and iron. Nickel wire is available, but its expensive and not widely sourced. Cobalt is even more expensive with even fewer sources. Iron is the cheapest option and it turns out that iron...
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speaker enclosure calculations

Posted 12th February 2011 at 07:17 PM by seniordesign

Hello,

I am currently constructing a sealed enclosure for a 12 inch woofer with a resonant frequency of 38 Hz.
My senior design mentor wants me to alter the resonant frequency of the speaker by using a smaller enclosure to shift the frequency at which it resonates to 100 Hz. Its is being used in an interferometer, not for playing music, so I do not need to worry about sound quality.

Does anyone know of the calculations used to alter the Fs?
Thanks!
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Dynaudio PPM2 Loudspeakers

Posted 11th February 2011 at 04:36 AM by simpsonjp

I just bought a set of Dynaudio PPM2 monitors on auction at Audiogon. Does anyone know where to get any data on these speakers (ie spec sheet or reviews). Anyone own a set or have heard them?

Thanks,

Jeff
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PC Crossovers

Posted 10th February 2011 at 07:36 PM by DougL

This looked Interesting.

http://www.diyaudio.com/forums/multi...ml#post1033586

I'll have to research that.
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Digitally controlled class D

Posted 8th February 2011 at 07:24 PM by alexcp (My DIY projects)
Updated 17th December 2011 at 01:24 PM by alexcp

I wanted to build a Class D amp based on TI's PurePath chips - e.g. TAS5086 PWM processor and a few TAS5162 power stages - until I read Bruno Putzeys' "The Truth About Digital (Class D) Amplifiers". He makes a convincing argument that digitally controlled class D is a dead end street. I also noticed that very few people around here have been writing about PurePath. Shall I look at the UcD patent and application note, as well as ready made Hypex modules, instead?
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Wide-band RF filtering for mains

Posted 5th February 2011 at 04:07 AM by abraxalito
Updated 2nd March 2011 at 11:10 AM by abraxalito

Since Ostripper asked about mains filtration on the RF & Audio thread, here are some notes and ideas. I haven't built any of this yet - if you decide to, I'll be interested in any results - photos and listening reports. Be careful with this stuff, its at mains potential.

Pre-built mains filters are of some use in audio, but they're not really optimised for high-end sound. For audio source components, the draw is normally under 100W and so the current (assuming here 230V supply) is under half an amp. Few if any off the shelf mains filters are designed for such low currents.

Second, the commercial filters assume that we wish to stop conducted interference getting out as much as prevent muck getting in. The internal noise would normally only come from the rectifiers in a linear power supply (SMPSUs are a totally different matter). Once we've snubbed them (you have done that already right, or are using soft-recovery or schottky diodes?), with a linear...
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service manual NAD 7225 pe

Posted 1st February 2011 at 09:01 PM by migouel

Hi all. I have a NAD 7225 PE Amp that seems to not power up. Does anyone have a service manual for it or schematic? Where can I find info to help me fix the tuner? 4 Fuses Blown,Display,FM scan works ok.

Thanks
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My "Salas hotrodded DCB1" build

Posted 27th January 2011 at 07:06 AM by Rodeodave

I built the 10R version for now, maybe I'll up the current later. The power resistors I used are non-inductive planar 10R 5w thick film resistors (BI Technologies BPC5100J). The noise figures are comparable with metal film it seems. I just thought I'd give these a try, and since I'm using many fancy flavoured parts (at least for my taste) it fits the bill. I had to remove the original legs, which were some clamp-on soldered types, and fit them with bent copper leads since the original spacing was too small for the board. If you look close enough you can see it in the second picture.

Click the image to open in full size.


The MOSFETs are IRFP140N/9140N. The 5-LED chain is matched to 9.30V/9.29V (values measured in circuit), using 12VDC and 1k in series with it. The 3-LED chain was matched to 5.59V/5.58V (measured in circuit). The 5-LED chains are fed by 2SK170 that I once measured to...
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