T&L Publications

Does anyone know where i can get some information on designing using the NE570/571 compander IC..<p>I have got the standard Data Sheets (which are normally available) but i am after some circuits / schematics etc that use the IC as a Compressor and Expandor in HI-FI products<p>Can anyone help ??<p>IS there a better compander IC that i should be looking at ??<p>BobMcN

Hello Bob.<p>Here it is:<p>http://www-eu4.semiconductors.com/acrob ... /AN174.pdf<p>Enjoy,
Miguel

I made a compandor from the NE570 decades ago, using the app note information. I made separate compressers and expanders to avoid complicated switching arrangements.<p>It is possible to improve the attack time to make it quite fast with the use of a charge pump. That way, percussive transients such as piano or drums sound better, especially if the music is quiet and suddenly loud. Without the charge pump you can hear the compandor kicking in in this situation. I think EDN or a similar publication had a schematic for this but its 20 or 30 years ago so you would have to do a lot of tracking down to find the information.<p>The slew rate of the onboard opamps is relatively low, about the same as a 741, I think. So using an external op amp with faster slew rate and lower noise, as the app note illustrates, makes sense for higher fi. However, some tapes I made with the compandor decades ago sounded pretty good to me, although some "breathing" was audible. But the dynamic range and the lack of tape noise was quite nice. Cheaper than a DAT, for sure.<p>Grant

Thanks for the info chaps ! (i already had the app note...)
Is the Ne570 pretty old then ?
Is there something that is more up-to-date...
I am worried that if i design it in it will become obsolete
Any help please <p>BobMcN

Hi.
We used to manufacture the dbx 266 compressor/expander at my workplace; I just looked at the schematic and no NE570 in there.<p>Page 43 has the block diagram here:<p>http://www.dbxpro.com/ftp_mirror/PDFs/M ... Manual.pdf<p>Hope it helps,
Miguel

What is your application?<p>In addition to the NE570, Telefunken made a compander chip several decades ago. They also marketed a commercial version; the system was called Highcom. I have no idea if it's still around, but I doubt it.<p>The most widely used noise reduction is of course Dolby, but you must buy the chips and licence from Dolby.<p>I am not sure if you know what you want to design. When your design goals are clear, you can go looking for what you want. I briefly looked on Google and found sevaral other compander chips mentioned. If you want to design something you have to do your homework about what is available, and what you want to accomplish, and how others have solved the problem(s).<p>There is also literature out there, such as journals, for example the J of the Audio Engineering Society. If you look you will find a wealth of information.<p>Grant

Here's a list of compander chips:<p>http://www.vego.nl/7/7_024.htm<p>The details are in Dutch, nutthe chip numbers will allow you to search for datasheets<p>Grant

I found a couple of articles which might interest you. One is "A simple but Effective Noise Reduction System" by Craig Todd when he was at Signetics. (Does anyone remember them?).<p>The other one is from the April 12, 1979 Electronics, "Charge pump cuts compandor's attack time."<p>Grant

(original poster...) Where can i get this article you mentioned ?<p>I have sussed out most of the NE571 compressor / expander circuitry and tried most of the data sheet variants and some of my own, but i am still not happy with it, i just dont feel like i have any control over the ratios !!
Still searching for help..
Many thanks to everyone who has given input on this thread<p>BobMcN

I will copy them and snail mail them to you. My email is grant.fairATsympatico.ca [do the obvious with the AT]. Email your address back channel and I can likely mail them this weekend.<p>Grant

Or you could try to contact Craig Todd directly at Dolby Labs. Here is a bit of current information about him.<p>http://www.dolby.com/press/pa_pr_0210_smpte.html<p>If you track him down by email, and he helped you out you could probably find no finer source of info, since he is one of the primary developers of Dolby noise reduction systems. No harm in asking by email.<p>Grant