Mini amp circuit

This is the place for any magazine-related discussions that don't fit in any of the column discussion boards below.
User avatar
sofaspud
Posts: 531
Joined: Wed Feb 13, 2002 1:01 am
Location: San Antonio, TX
Contact:

Re: Mini amp circuit

Post by sofaspud » Sun Jan 31, 2010 4:25 pm

CeaSaR,
I also have CircuitMaker v6.2c and while I haven't done so, it is possible to add new components to the library. Instructions
are found in Help under "Adding New Models to an Existing Symbol." Unless you're a SPICE power user and can create your
own models (I sure ain't) you'll need to find the ASCII files for the parts you want on the manufacturer's website.

User avatar
CeaSaR
Posts: 1698
Joined: Sat Nov 08, 2003 1:01 am
Location: Phoenixville, PA USA
Contact:

Re: Mini amp circuit

Post by CeaSaR » Sun Jan 31, 2010 10:24 pm

Sofaspud,

I'm a user of the "student" version - can't make macros, limited to 50 parts per schematic, etc. I did find that if
I found a PSpice .LIB that I need, I can go in and enter all info for the device I want to create that new part.

Steps:
Draw the default part, ie. default NPN. Click and edit the part. Give it a new name, description and fill in any info
for the part - IS:, BF:, NF:, etc. by copying directly from the ASCII .LIB file.

I found my TIP series at the Cadence.com page for their PSpice downloads. I found it through a Yahoo! search
that lead me to a handy Spice Model Index.

Now for more fun... Mwahahaha!

CeaSaR
Hey, what do I know?

User avatar
CeaSaR
Posts: 1698
Joined: Sat Nov 08, 2003 1:01 am
Location: Phoenixville, PA USA
Contact:

Re: Mini amp circuit

Post by CeaSaR » Tue Feb 02, 2010 11:12 am

sofaspud wrote:I was/am interested in the original (well, v6.0?) circuit for use as a headphone amp and also to power a set of Philips SBP1100
speakers I picked up at Walmart. Pretty decent small 2" speakers rated 1.5W that I'd like to use with my laptop mostly. I wanted
something better than the usual LM386-type chip amp for these unusual hemispherically-enclosed speakers.
Hmmm... is that Losmandy amp stable into 2 ohms?
"...most Philips stuff is obsolete..."? I thought they just spun off the semiconductor division and rebranded it as NXP. I am having
trouble finding a datasheet for the LM2822M. Anyone know where it's hiding?
My last schematic is on page 6 of this thread, near the bottom. Since you have CircuitMaker also, I could send
my files to you and you could play with them to suit your needs. I have both my "collaborative" design and Robert's
updated version of the Losmandy amp. Let me know if you want them.

As for the LM2822M, all I found is a Chinese site and couldn't make heads or tails out of it. It looked like it was
another search page, and I was not going to go through translation for it.

CeaSaR
Hey, what do I know?

User avatar
CeaSaR
Posts: 1698
Joined: Sat Nov 08, 2003 1:01 am
Location: Phoenixville, PA USA
Contact:

Re: Mini amp circuit

Post by CeaSaR » Tue Feb 02, 2010 11:21 am

Bob Scott wrote:I think that the word you were fishing for could be "beta multiplier", the two transistor pair that works like a darlington but uses one PNP and one NPN. That is the name we used circa 1970 for those audio output transistor pairs.
Yes, that's it!

Thanks,

CeaSaR
Hey, what do I know?

User avatar
sofaspud
Posts: 531
Joined: Wed Feb 13, 2002 1:01 am
Location: San Antonio, TX
Contact:

Re: Mini amp circuit

Post by sofaspud » Tue Feb 02, 2010 8:25 pm

CeaSaR,
That is a kind offer which I believe I'll take you up on. I've pm'd you about it.

And yeah, my LM2822 searches turned up screens full of Chinese characters. This is a Philips 8-pin DIP and the links appeared to be
distributors' sites. Lends credence to Robert's "sellin' 'em by the box" comments.

I had a powered subwoofer project in mind, and had been looking at the TDA7396. The Losmandy seems to fit the need perfectly, as
it'll be using a 2 ohm speaker. I got it from a dumpster diving expedition at the local car stereo/window tint shop. Seems that when
they do an upgrade install, they often throw out the old speakers, wire, radios, etc. Great for junkbox inventory enhancement. :)
And... I'm doing my part to help the environment. :mrgreen:

User avatar
CeaSaR
Posts: 1698
Joined: Sat Nov 08, 2003 1:01 am
Location: Phoenixville, PA USA
Contact:

Re: Mini amp circuit

Post by CeaSaR » Tue Feb 02, 2010 8:43 pm

PM'd you back.

Gotta love the parts recycling. Does your part for the environment AND gets you stuff you can use.

I've been playing around with the original scheme, pushing the voltage up and beefing the output, adjusting
R14 with success (sim-wise). Could be useful to you.

CeaSaR
Hey, what do I know?

User avatar
CeaSaR
Posts: 1698
Joined: Sat Nov 08, 2003 1:01 am
Location: Phoenixville, PA USA
Contact:

Re: Mini amp circuit

Post by CeaSaR » Wed Feb 03, 2010 12:21 am

Robert,

I knew I had seen something like the Losmandy amp before. See this. I knew I wasn't senile...yet. :lol:

CeaSaR
Hey, what do I know?

Robert Reed
Posts: 2276
Joined: Wed Nov 24, 2004 1:01 am
Location: ASHTABULA,OHIO
Contact:

Re: Mini amp circuit

Post by Robert Reed » Wed Feb 03, 2010 9:29 am

Nope
Not really that similar (lots of components and different output configuration). But one thing of great interest in this circuit is the standard Op-Amp with it's normal supply voltages driving high voltage supplied output stages. I was wondering if I could do this with individual transistor amplifiers rather than followers driving the output stages. And sure enough, your post confirms that thought. Thanks for posting that as it will be good food for thought in the future.

User avatar
Bob Scott
Posts: 1192
Joined: Wed Nov 20, 2002 1:01 am
Location: Vancouver, BC
Contact:

Re: Mini amp circuit

Post by Bob Scott » Wed Feb 03, 2010 3:01 pm

[Retracted due to brain expectoration]
-=VA7KOR=- My solar system includes Pluto.

sghioto
Posts: 319
Joined: Wed Dec 26, 2007 5:16 pm
Location: N. Florida
Contact:

Re: Mini amp circuit

Post by sghioto » Wed Feb 03, 2010 5:22 pm

I have just one question. Is this thread ever going to end? :wink: :razz:

Steve G.

User avatar
CeaSaR
Posts: 1698
Joined: Sat Nov 08, 2003 1:01 am
Location: Phoenixville, PA USA
Contact:

Re: Mini amp circuit

Post by CeaSaR » Wed Feb 03, 2010 10:13 pm

This is the thread that never ends... it just goes on and on my friends....

song

:mrgreen: :mrgreen:

CeaSaR
Hey, what do I know?

User avatar
CeaSaR
Posts: 1698
Joined: Sat Nov 08, 2003 1:01 am
Location: Phoenixville, PA USA
Contact:

Re: Mini amp circuit

Post by CeaSaR » Thu Feb 04, 2010 10:38 am

Bob,

Back to the early times on this thread. Re: bridged amplifier. Taking the ubiquitous LM386, doubling the number
of ciruits and feeding the same signal to the inverting (-) input on 1 and the non-inverting (+) input on the 2nd,
then feeding the outputs of those to either side of the same speaker (#1 to spkr+, #2 to spkr-), would this give
approximately 2x's the power? On page 6 of this thread about 1/3 of the way down, you said that a bridged
version of the discrete design woud give approximately 4x's the power without the need for output caps. Would
that still stand for an "op-amp"/single chip based design? I'm not sure how that works.

CeaSaR
Hey, what do I know?

Robert Reed
Posts: 2276
Joined: Wed Nov 24, 2004 1:01 am
Location: ASHTABULA,OHIO
Contact:

Re: Mini amp circuit

Post by Robert Reed » Thu Feb 04, 2010 5:56 pm

Caesar
You can bridge any thing. Two requirements - the driving signals have to be 180 degrees out of phase and the load must float between them - no ground connection. When you apply the two signals you double the voltage across the load. This is a 6 DB increase. 6Db translates to 4 times the power.

User avatar
CeaSaR
Posts: 1698
Joined: Sat Nov 08, 2003 1:01 am
Location: Phoenixville, PA USA
Contact:

Re: Mini amp circuit

Post by CeaSaR » Thu Feb 04, 2010 7:47 pm

Robert,

Yes, the 2 would be 180 deg. (exact same signal to opamp1 pos. input and opamp2 neg. input) and
then the resultant outputs fed to the opposite sides of the speaker. Twice the voltage, understood,
because the pos. half still goes the same amount while the neg. half heads the same amount in the
opposite direction. Twice the potential across the load. 2 x's voltage = 6 Db = 4 x's power.

So if the single original unit could provide 1 W, then the bridged version could put out ~4 W?
Do I understand this correctly?

CeaSaR
Hey, what do I know?

Robert Reed
Posts: 2276
Joined: Wed Nov 24, 2004 1:01 am
Location: ASHTABULA,OHIO
Contact:

Re: Mini amp circuit

Post by Robert Reed » Thu Feb 04, 2010 8:22 pm

You Got it.
Just remember that if this is a modification to an existing circuit, the existing power supply has to have the beef to supply that exta load power.

Post Reply

Who is online

Users browsing this forum: No registered users and 13 guests