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Chip Amps Amplifiers based on integrated circuits

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Old 10th August 2012, 09:37 PM   #1
7V is offline 7V  United Kingdom
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Default Building an active mini monitor - need chip amp

I'm known to some here for building Seventh Veil loudspeakers.

I'm now building an active mini monitor using Bandor drivers and need some advice on amplification. Per side, I'm using two Bandor 50mms for everything from 200Hz upwards and one Bandor 100m for below 200Hz. The drivers are very fast and transparent. What are the best chip amps I could use with an output of 20W to 30W into 8 ohms? I generally like a good valve amp but that wouldn't be appropriate for this application. I'm new to this area so would look at either a kit or a circuit board. Any advice would be appreciated.

Thanks in advance
Steve

PS: I know that there are plenty of relevant threads here but don't really know where to start in looking for the up to date information I need.
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Old 10th August 2012, 10:49 PM   #2
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Steve,

This is another Steven and I am also new to this site and these Forums. The problem I am also having is that using the search bar here even if I get very specific in what I am looking for I get a whole rash of things that don't appear to be relevant. Can someone tell us Steve's how we can better search this site without having to read every thread to find information?

Thank,
Steven
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Old 11th August 2012, 03:45 AM   #3
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I use the dropdown on the search to choose advanced search. This gives you a lot more options. The most valuable one I find is changing the search results to posts rather than threads.

Another thing you can try is going to google and then putting in your search term followed by site:diyaudio.com This will use googles powerful search engine but only return results from diyaudio.com

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Old 11th August 2012, 03:47 AM   #4
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Tony,
Thank you for the pointers. I will do that, of course I didn't see the advanced search but I am new to the site so I was just being a dweeb.

Steven
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Old 11th August 2012, 04:06 AM   #5
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No probs

Steve welcome back! I note your site is no longer around. I really liked the analogy (if I remember correctly) of the dance of the 7 veils with each one reveailing something more when removed. With the reference to the speakers that all 7 veils had been removed leaving only the naked truth with the sound

With respect to the amps, I've only got experience with the LM3886. I find it ok, but I've recently switched back to my 100W mosfet amp. My speakers are not that efficient and I suspect I was clipping the chipamp on transients (also if I were to do it again I would lower the gain somewhat, not easy now as I did it as a very compact p2p).

Hopefully some others can offer suggestions on other chips, but an LM3886 would do a good job for up to 50W into 8 ohms. There may of course now be better alternatives, it's around six years since I built mine!!

Tony.
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Old 11th August 2012, 04:25 AM   #6
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Thanks Tony,
I am looking at doing a bridged / Parallel design with 4 of the 3886 chips on the bass channel and a single unit on the high pass circuit for the tweeter alone. That should give me enough power for the tweeter no problem with either 4 or 8 ohm load. The mid/bass is a long throw speaker of my own design and the first version was about 86db per watt. I am working on raising the efficiency by changing the motor to increase the magnetic energy in the gap and decreasing the mass of the cone that I make. It is a new composite material that I have developed. Nobody has anything like it, I do nor use a traditional matrix material. I think that the National or now TI chips look good for a self powered speaker and I am just trying to determine the best opamps to use in the active crossover which will be a 4th order Linkwitz Riley design. I see the the 5532 chips are cheap but not well liked. I am leaning towards the LM4562 but still not sure if that is the best idea. Most of the information that I have found on these chips for crossover is at least a few years old and I am not up on the latest in these parts.

Steven
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Old 11th August 2012, 05:37 AM   #7
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I am no expert of the amp side, but I have been thinking about a similar issue. If using a chip amp why not build active? Use 2 smaller chip amps and a small circuit for a 2-way electronic XO and put it all inside the box, line in only or is that what you intended and just didn't say?
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Old 11th August 2012, 06:10 AM   #8
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Moondog,
I guess I wasn't very clear here. I am planning on an active cross-over and then the gain clone amp and all inside the enclosure. I haven't seen much that can compete with the National Semi chip before going for a class D circuit which I don't want to do. I just am questioning the best chips to implement the xo. Some like to use the 5532 chip for price reasons and others just hate that chip, but others also don't seem to think much of the LM4562 I see some other low noise chips but some of the prices are just plain crazy. I don't mind the price of the 4562 but if something is in the same range and is better why not use it...

Steven
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Old 11th August 2012, 06:19 AM   #9
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Quote:
I am looking at doing a bridged / Parallel design with 4 of the 3886 chips
You may find the NatSemi application note 1192 worth a look or two, if you haven't done so already.
Quote:
I see the the 5532 chips are cheap but not well liked.
Somebody likes them; they're quite popular. The data may be a few years old (or more), but it's still valid. IMO a very good active xover could be built from either of those op amps you mention.
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Old 11th August 2012, 06:53 AM   #10
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OPA2134's for the filter circuit would probably be a good choice. They are low noise, low distortion, fet input, have enough bandwidth (without being finicky about the circuit). Generally a good allround chip I's say http://www.partsconnexion.com/prod_pdf/opamp_64156.pdf

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