If you need assistance, please send an email to forum at 4hv dot org. To ensure your email is not marked as spam, please include the phrase "4hv help" in the subject line. You can also find assistance via IRC, at irc.shadowworld.net, room #hvcomm.
Support 4hv.org!
Donate:
4hv.org is hosted on a dedicated server. Unfortunately, this server costs and we rely on the help of site members to keep 4hv.org running. Please consider donating. We will place your name on the thanks list and you'll be helping to keep 4hv.org alive and free for everyone. Members whose names appear in red bold have donated recently. Green bold denotes those who have recently donated to keep the server carbon neutral.
Special Thanks To:
Aaron Holmes
Aaron Wheeler
Adam Horden
Alan Scrimgeour
Andre
Andrew Haynes
Anonymous000
asabase
Austin Weil
barney
Barry
Bert Hickman
Bill Kukowski
Blitzorn
Brandon Paradelas
Bruce Bowling
BubeeMike
Byong Park
Cesiumsponge
Chris F.
Chris Hooper
Corey Worthington
Derek Woodroffe
Dalus
Dan Strother
Daniel Davis
Daniel Uhrenholt
datasheetarchive
Dave Billington
Dave Marshall
David F.
Dennis Rogers
drelectrix
Dr. John Gudenas
Dr. Spark
E.TexasTesla
eastvoltresearch
Eirik Taylor
Erik Dyakov
Erlend^SE
Finn Hammer
Firebug24k
GalliumMan
Gary Peterson
George Slade
GhostNull
Gordon Mcknight
Graham Armitage
Grant
GreySoul
Henry H
IamSmooth
In memory of Leo Powning
Jacob Cash
James Howells
James Pawson
Jeff Greenfield
Jeff Thomas
Jesse Frost
Jim Mitchell
jlr134
Joe Mastroianni
John Forcina
John Oberg
John Willcutt
Jon Newcomb
klugesmith
Leslie Wright
Lutz Hoffman
Mads Barnkob
Martin King
Mats Karlsson
Matt Gibson
Matthew Guidry
mbd
Michael D'Angelo
Mikkel
mileswaldron
mister_rf
Neil Foster
Nick de Smith
Nick Soroka
nicklenorp
Nik
Norman Stanley
Patrick Coleman
Paul Brodie
Paul Jordan
Paul Montgomery
Ped
Peter Krogen
Peter Terren
PhilGood
Richard Feldman
Robert Bush
Royce Bailey
Scott Fusare
Scott Newman
smiffy
Stella
Steven Busic
Steve Conner
Steve Jones
Steve Ward
Sulaiman
Thomas Coyle
Thomas A. Wallace
Thomas W
Timo
Torch
Ulf Jonsson
vasil
Vaxian
vladi mazzilli
wastehl
Weston
William Kim
William N.
William Stehl
Wesley Venis
The aforementioned have contributed financially to the continuing triumph of 4hv.org. They are deserving of my most heartfelt thanks.
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
There are reasons why IC amplifiers are limited in power. A high power linear amp needs a lot of silicon area, and it gets uneconomical to integrate that onto one huge die.
It's also hard to make an IC withstand the high voltages needed for high power into 4 or 8 ohm loads. (Hence, Harry's suggestion won't work, because he won't find an IC that'll produce enough voltage swing to drive the output stage. Unless he were to use an output stage with gain greater than 1.)
And lastly, the heat from the power section of the die tends to destabilize the small-signal circuits. In a discrete amp you can put the input transistors right at the other end of the board to the heatsink.
The highest power IC I know of is the TDA7293. Marshall made a 350 watt guitar amp, the MF350, using four of these in bridge/parallel. These amps seem to be unreliable and blow out their TDA7293s regularly.
Compare that to the old 400 watt power amp circuit used by Peavey, with six TO-3 power transistors on a huge heatsink. They made a lot of these in the 70s and most of them seem to still be going.
If you can find lateral MOSFETs (it doesn't work with the ordinary SMPS kind) then the old Hitachi/Maplin MOSFET amp is still worth considering. It's about the simplest discrete power amp you can possibly make, and good for about 120W into 4 ohms.
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
Steve McConner wrote ...
It's also hard to make an IC withstand the high voltages needed for high power into 4 or 8 ohm loads. (Hence, Harry's suggestion won't work, because he won't find an IC that'll produce enough voltage swing to drive the output stage. Unless he were to use an output stage with gain greater than 1.)
I don't quite follow why you couldn't use an inter-stage transformer which would isolate beneficially the two stages, as well transforming impedances and voltages. Being an idle fellow, as a first start I'd probably try an ordinary AF O/P transformer in reverse, or one of the combinations possible with those multi-tap AF line transformers - but, as I said, I don't really think in a solid state way. My head may be Hollow State too!
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
Well, you could do that, it worked for Thomas Vox in the 70s:
I once experimented with a hybrid amp that used a push-pull transistor output stage, driven through a step-down transformer by an EL84. I got over 50 watts out of it, which must be some sort of record for one EL84
But I think all of this complicates things unnecessarily, compared to the classic three-stage discrete amp.
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
Yes, Steve, perhaps it does create complication - but it seemed a way to conserve all of the gadgets and gimmicks on a consumer PA IC, yet still have a simple high power output stage.
Registered Member #1819
Joined: Thu Nov 20 2008, 04:05PM
Location:
Posts: 137
Hazmatt_(The Underdog) wrote ...
I have most of the DIY audio amp books, including the two by Slone and so far his first project doesn't really work that well. Not only that but you have to have some equipment to tweak-in the amp when you build it from components, and the expense far outweighs anything you can consider at the moment. Ordinarily, getting a current mirror to work properly is no concern, but when you are trying to guarantee a clean output to the voltage amplifier stage and gain, its more like an experiment then anything else.
1. Don't bother with discrete unless you need bandwidths greater then 30KHz.
2. If you're prepaired to waste a lot of time debugging something someone else designed... maybe wrong.
3. If you really understand component selection ( I still have trouble with this)
4. If you have equipment to tweak it in
5. I have a little push pull class B amp here with 100W transistors that can only push 20W at the moment, and I expect it will be a lot of work to get it to output more.
So consider the time spent vs. the money spent, spending the money may be saving you a lot.
I don't understand what you mean by "tweaking it in". Do you mean calibrating something such as quiescent current? This depends on the specific design of the amplifier.
By the way, it might be SOA or thermal derating limiting your 100W transistors.
Harry wrote ... I don't quite follow why you couldn't use an inter-stage transformer which would isolate beneficially the two stages, as well transforming impedances and voltages. Being an idle fellow, as a first start I'd probably try an ordinary AF O/P transformer in reverse, or one of the combinations possible with those multi-tap AF line transformers - but, as I said, I don't really think in a solid state way. My head may be Hollow State too!
Signal transformers that can handle the whole 20 to 20 kHz frequency range are expensive, often costing $50 for a tiny transformer. Although I'm not too sure if that kind of transformer is what you're talking about.
Registered Member #575
Joined: Sun Mar 11 2007, 04:00AM
Location: Norway
Posts: 263
I would go for the LM3886 or if you want power go for LM4780. LM4780 consist of two LM3886 these chips are well proven and used in many Hi-Fi audiophile projects. I am currently using a tube buffered LM4780 in dual mono configuration. A LM4780 can drive two speakers at 8ohm 64 watt stereo or one single 8ohm at 128. For 4ohm impedances remember that you will need lover voltages and and bigger heat sinks.
Registered Member #575
Joined: Sun Mar 11 2007, 04:00AM
Location: Norway
Posts: 263
Nikhil wrote ...
How do i modify the chip amp ckt so as to suit a sub woofer or a tweeter ?
With a crossover filter before or after the chip amp, if the speaker already have a built-in crossover filter you should be okay without any configuration.
This site is powered by e107, which is released under the GNU GPL License. All work on this site, except where otherwise noted, is licensed under a Creative Commons Attribution-ShareAlike 2.5 License. By submitting any information to this site, you agree that anything submitted will be so licensed. Please read our Disclaimer and Policies page for information on your rights and responsibilities regarding this site.
Audio Amplifier ICs
