Contest: Linear Power Amp in a mint tin (class Aa, class AB, or class B) - Page 18 - diyAudio
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Old 1st January 2013, 11:40 PM   #171
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Hey guys, this is a power amp thread. Here is a link to the DiyAudio.com headphone amp area: Headphone Systems - diyAudio

Meanwhile, back to power amp in a mint tin contest, which is more like:
At least 9W@10%THD (7.5W@1%THD) per channel to 8 ohms stereo amplifier
OR at least 20W@10%THD (16W@1%THD) to 8 ohms monobloc Parallel amplifier

An LM386 headphone amplifier is not quite that strong.
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Last edited by danielwritesbac; 1st January 2013 at 11:48 PM.
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Old 1st January 2013, 11:55 PM   #172
qusp is offline qusp  Australia
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no problem

if I paralleled the buffers on the output of the dac/headamp or added a follower that power would be within reach, the battery will put out 140A bursts and its connected directly to the buffers (regulated front end)

but its too large =)
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Old 2nd January 2013, 12:33 AM   #173
JMFahey is offline JMFahey  Argentina
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Dear danielwritesbac, don't worry
*I* asked some details about in/out connectors and clearly will post a project following the original rules.
Remember what was actually written in Post #143.

A couple posts later our friend Kindhornman asked about its suitability driving earphones, while battery driven.
Out of courtesy I suggested there were *other* ways to do it , even hinted that LM386 were the way to go, yet it's clear it would be posted "here" (DIY Forum) but of course in another thread.
Because I think it deserves its own.

Why a simple question and answer (which should have finished that issue there and then) gave birth to around 30 posts, is beyond me

OK, back to the original project.
Which on my side still needs getting a suitable tin can, as mentioned.
Most or all of the rest of the stuff is already available.

Maybe I'll have to wind a custom transformer, but I think I already have wire and lamination, must check stock.

In fact, just *now*, in this boring long afternoon with *all* shops closed and nothing good on TV, by sheer coincidence, I'm building a 12V battery powered amp. 16W bridged into a 6" 4 ohms speaker; but I'm not posting it here because it's *not* housed in a tin can, but in a little "guitar type" Tolex covered combo, which although *loud* does not exactly match the OP specs.
But stay tuned for the tin can one
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Old 2nd January 2013, 08:50 AM   #174
qusp is offline qusp  Australia
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haha are you seriously trying to shirk any responsibility for the tangent? I suppose I shouldnt be surprised..... we arent getting in trouble at school here, be a man and wear some blame where its due please, then move on.

YOU carried it on and made a very confused, provocative and argumentative post directed at me when I wasnt even talking to you, about you, or your as yet unrevealed design. I couldnt help but reply to that, which is childish in its own way, but I wont lose any sleep over it.

do you think you may be punished, so are trying to squirm?

just apologize for the distraction and move on, it really is that simple
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Old 2nd January 2013, 09:47 AM   #175
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Daniel,
Sorry for highjacking your thread. I surely had no intention to do that with my original question. But I will say that this is an interesting exercise you have going on here.

Steven
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Old 2nd January 2013, 11:09 AM   #176
qusp is offline qusp  Australia
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agreed, its quite interesting, I dont have time to take part but i'll be interested in the results. I would also think that laterals would be useful here, something using a current mirror or dual NP transistor part (or opamp) teamed with a couple of the alfet (semelab) bipolar to247-5 lead parts like ALF08NP16V5 due to simple biasing, inbuilt current limiting, thermal stability and overall being pretty bulletproof.

not the cheapest of parts though
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Old 2nd January 2013, 02:20 PM   #177
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Quote:
Originally Posted by JMFahey
In fact, just *now*, in this boring long afternoon with *all* shops closed and nothing good on TV, by sheer coincidence, I'm building a 12V battery powered amp. 16W bridged into a 6" 4 ohms speaker; but I'm not posting it here because it's *not* housed in a tin can, but in a little "guitar type" Tolex covered combo, which although *loud* does not exactly match the OP specs. But stay tuned for the tin can one
That's quite close.
There's just one glitch:
An audio amp will power a 20 ohm speaker a lot more efficiently than a 0.2 ohm speaker. Likewise an audio power amp will power an 8 ohm speaker more efficiently than a 4 ohm speaker. So, the presence of batteries didn't indicate maximized efficiency. Got an 8 ohm option?
Staying tuned. Tuned?
I wonder who's going to put in a tuner to make mint tin integrated amplifier receiver combo?
Quote:
Originally Posted by qusp View Post
agreed, its quite interesting, I don't have time to take part but I'll be interested in the results.
See post 1 for the monophonic option that will be faster and easier to build.
Quote:
Originally Posted by qusp View Post
I would also think that laterals would be useful here, something using a current mirror or dual NP transistor part (or opamp) teamed with a couple of the alfet (semelab) bipolar to247-5 lead parts like ALF08NP16V5 due to simple biasing, inbuilt current limiting, thermal stability and overall being pretty bulletproof. not the cheapest of parts though
Lateral Fet = Dmos = Power Mosfet, now widely available and very inexpensive in somewhat less convenient Dpak packages with different model numbers.

Dual Transistor such as dual BC560 (saturates easily at small signal), dual BC327 (doesn't saturate easily at small signal), are available from Philips-NXP and/or Fairchild in somewhat less convenient SMD packages with weirdly different model numbers.

Lateral Fet also available in a chip power amplifier, the TDA7296, which is a good part that suffers from a poor datasheet (needs a trimmer party to find hi-fi which is not in the datasheet) and a mad pinout that makes optimizing a PCB layout both difficult and dual-layer.

There's a few inconveniences, but I didn't see any big expenses.
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Old 2nd January 2013, 04:49 PM   #178
JMFahey is offline JMFahey  Argentina
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Fine.
I mentioned it because that's what I was *actually* doing and relatively close to this project.
And since I'm limited by the 12V battery, 4 ohm loads draw more power than 8 ohm ones.
But let's go back to the original project.
I just NEED to get those d*mn tin cans !!!
Incredibly, none available in the dollar shops around here.
I remember when they were chock full of them in all sizes. Oh well.
Will try downtown.

As a side note on:
Quote:
Staying tuned. Tuned?
I wonder who's going to put in a tuner to make mint tin integrated amplifier receiver combo?
It's common urban slang.
From Urban Dictionary: stay tuned
Quote:
1. stay tuned

To hang on, awaiting more news on a subject.


On old dial-tuned AM radios before there were even preset buttons, it was a non-trivial task to tune into a particular station. So radio news announcers would tell their audience to stay tuned to the station if they were expecting more info on the current story."

Literally: "(crackle) explosions reported at Pearl Harbor naval base in (crackle) Hawaii...stayed tuned for more news..."

Modern: "Chad's about to tell Rachel he's been cheating on her. Stay tuned for the screaming."
So stay tuned for the 2x9W or 1x20W mint can amp
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Old 3rd January 2013, 10:51 AM   #179
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Stay tuned, right, from the 1920's Neutrodyne. Yeah, it did take a while! My grandad could work that radio really fast.

Mint tin, Office Depot, Walgreens, have the old fashioned size mint tins like mine that will even fit an STK chip, as shown in post #6.
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Old 3rd January 2013, 05:26 PM   #180
PetruV is offline PetruV  Romania
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Quote:
Originally Posted by johnr66 View Post
I think I could reconfigure this BTL 45 watt amp for stereo using horizontal mount ICs and lower profile components. The board would mount up to a heatsink with impeller type fan. The board in the pic is only 1-3/4" x 2-1/4".

I'm not sure if I could get it below 3/4" thickness (or even an 1") and not have thermal issues.

Click the image to open in full size.

Some of the car stereo power amp ICs need as few as three film caps to function, although I like to add RF filtering on the input. This may be another option. Power supply would be simpler as well.
What chips are those are they 12v powered please respond
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