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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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Old

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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Old

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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Old

MR211's Blog

Posted 25th January 2011 at 06:23 AM by asterkao
Updated 3rd September 2013 at 01:22 AM by asterkao

http://kao211.blogspot.tw/
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Old

Compact PCB For All JFET Circlotron

Posted 24th January 2011 at 11:59 PM by Michael Rothacher
Updated 2nd October 2011 at 11:59 AM by Michael Rothacher

This is the artwork for the PCB in the pictures. It fits into the ExpressPCB miniboard profile so it's a little cheaper to have made.

It will be necessary to check the orientation of the bias pots (I can't remember). I wouldn't want you to blow-up your $30 JFETs.
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Old

All JFET Circlotron

Posted 22nd January 2011 at 10:29 PM by Michael Rothacher

I've been mostly out of the audio hobby for a while, but I've had a few inquiries about the SemiSouth version of the Amazing FET Circlotron as of late. So, I wanted to post the performance graphs here before I lose them.
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Old

Getting started again is harder than I imagined!

Posted 8th January 2011 at 12:09 PM by wintermute (Wintermutes Rantings)
Updated 18th January 2011 at 10:45 AM by wintermute (audigy now working reliably!)

It seems I have been doomed to not do any of my DIY projects since my main computers hard drive crashed followed shortly after by my laptops (the laptop has had another crash after that, and the drive is now on the way out again!!)

After having to pull the cables out of my chipamp last week and plug the TV into it (because the MythTV box refused to play a DVD and I can't plug the DV18 DVD player direct to the chipamp because it has no volume control) I decided I had better get off my backside and finish my pre/active crossover. I had to do it again tonight as well (plug the tv into the chipamp), sigh...

This is all because my playmaster had something in the pre die again and is only working on one channel and I just haven't been bothered fixing it. I thought that being inconvenienced might make me more likely to finish the other projects but it has been broken for about 6 months

So on Monday I decided that I should re-install Holm-Impulse...
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Old

DCPP aka Engineer's Amplifier

Posted 8th January 2011 at 01:09 AM by alexcp (My DIY projects)

I just built a Distortion Cancelling Push Pull (DCPP) amplifier designed by Peter Millett. It sounds very nice, was fairly easy to build, and is rather inexpensive. Thank you Peter for the great design!
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Old

Playing Vinyl on a TD-124

Posted 6th January 2011 at 08:50 PM by kevinkr

I acquired a TD-124MKII back in late September and after some months feel like I have come to some understanding of its strengths and weaknesses.

I finally understand that the drive train will never be silent, and needs some periodic maintenance to perform quietly.

Belts are problematic on the MKII, and later versions of the MKI with the dual in chassis intermediate pulley. For some reason very early units seem quieter in this respect.

Motor rebuilding is pretty worthwhile, mine of course was not running so it was mandatory. My experience with motor bearings is limited, but based on replacing a number of bearing sets I would recommend the bearings available from The Analog Depot over others I've tried. They are very precisely made and run well from the get go.

I've added a Bren1 record weight which I feel clamps the record more effectively to the table's moving mass, and I thought improved some areas of performance significantly. Bass...
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Old

PreAmp Circuit

Posted 4th January 2011 at 11:33 PM by Lesa

Hello guys,

I was wondering if any genius out there who knows about preamp circuit who can explain this one to me.

See I am just getting into audio systems design and I am try to understand this preamp circuit and how it works.

A few questions:

1)what does the two cap in series does and why are they connect to ground?

2) what does R3, R1 and R2 does?

3) What is the uses of the polarity Reverse?

I have been reading up on these component but i am a little slow on understanding.

I would appreciate the help.
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