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Old 21st March 2013, 02:50 PM   #3621
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Quote:
Originally Posted by brummiejon View Post
Compared to the discussions between danielwritesback and saturnus, my question is rather puny and shows my ignorance in electronics...... I want to have an input (3.5mm stereo jack socket) and a thruput (another 3.5mm stereo jack socket) so that I can link the same sound source with multiple boomboxes...... Is it as easy as wiring the two jack sockets in parallel so that the input signal can be "shared", or is there some other consideration that prevents it from being that easy? and if so, how should I wire it?
You just use a headphone splitter, like Belkin Rockstar or similar.

Given that the usual supported headphone minimum impedance is 16 ohm of almost any mp3 player or phone and that the typical input impedance of a TA202x amp is 22Kohm, any mp3 player's headphone output can effectively be split to (22000/16) 1375 TA202x based amps without the mp3 player seeing a more difficult load.

If you want an active solution something like a Behringer HA400 would do the trick.

You can even combine the two and use the Behringer to pull several of the Belkin Rockstars. That's 20 Boominators connected right away but limitless amounts is possible.

Last edited by Saturnus; 21st March 2013 at 02:58 PM.
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Old 21st March 2013, 03:31 PM   #3622
JMFahey is offline JMFahey  Argentina
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Quote:
Originally Posted by brummiejon
Compared to the discussions between danielwritesback and saturnus, my question is rather puny and shows my ignorance in electronics...... I want to have an input (3.5mm stereo jack socket) and a thruput (another 3.5mm stereo jack socket) so that I can link the same sound source with multiple boomboxes...... Is it as easy as wiring the two jack sockets in parallel so that the input signal can be "shared", or is there some other consideration that prevents it from being that easy? and if so, how should I wire it?
Short answer: yes, connect them in parallel.
Do the same if you wish in each "Boom......." and you will be able to drive many of them in parallel, by chain linking them, if coming from an earphone out or, say, a DJ mixer line out.
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Old 21st March 2013, 04:12 PM   #3623
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Thanks for the replies, I'm not too far off then..... I hadn't thought of a headphone splitter but I still intend to build the throughput into the boominator......
we are planning a beach party in the summer and the boominator will be the main soundsystem and we will link up about 20 "minirigs" and an FM transmitter to it so that the signal can be picked up on radios over the whole coastline. I keep telling my minirig pals that they won't hear their minirigs over the boominator but they won't listen.... he he... can't wait to have the last laugh, for all the right reasons........

Tweeters on their way........

BJ
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Old 22nd March 2013, 02:56 AM   #3624
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Quote:
Originally Posted by brummiejon View Post
I keep telling my minirig pals that they won't hear their minirigs over the boominator but they won't listen....
Bring some gaffa tape so they can wear the minirigs as headphones
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Old 22nd March 2013, 08:59 AM   #3625
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AMP6 BASIC Sneaky's have arrived! AND it's going to be a wet weekend = might get some time to build an amp and test in my boominator. yeaaaa, I'm excited :-)
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Old 23rd March 2013, 05:00 AM   #3626
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Originally Posted by Saturnus View Post
The 0.47uF is the optimum for with the 22Kohm input impedance of the amp6b (unless modified). The amp9b has 50Kohm input impedance.

I'd recommend something like 0.1uF for the amp9b. It shouldn't affect bass performance in any way, just limited cone movements you can't hear anyways. In fact, if anything it should result in even better midrange.
Not sure if this should be asked here or on 41hz forums.
And I am Sorry if I'm rehashing anything, but a quick search didn't give a definative answer.

The Boominator in it's original design was for lower freq of 82Hz, and rolls of pretty quickly from there.

As you say 0.47uF is optimal, but looking at the calculation with the amp6 basic calculations ( assuming this is correct)
F=1(2*n*Rin*Cin)
So based on that the following should be correct Assuming the above is using the standard 22kohm resistors

0.47uF = 15hz
0.22uF = 33hz
0.15uF = 48hz
0.10uF = 72hz

so would not the ultimate Battery/Audio combo be 0.10uF low ESR caps, or is that too close to the roll off freq?

Q1. I might as well get the exact Capacitor now what would be the perfect size?
Q2. and could I get these from Jaycar?

Cheers, S. :-)

Cheers, S.
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Old 23rd March 2013, 08:44 AM   #3627
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Please look a few posts back where I explained it but the 0.47uF is the value.

It gives an x-o of 15hz and a roll-off that due to the low Q of the filter starts at 63hz. Even though the box Fb is 82hz the Fp (port tuning frequency) is 66hz. It is important that the Fp is unfiltered for optimum performance.

The input capacitor in itself is a feeble sub-cut filter but with the correct value it helps the built-in acoustic roll-off just enough. For greater effect I suggest a more advanced filtering.

Please get the exact replaced input capacitor suggested earlier in this thread or a similar compact size low voltage polyester or polypropylene capacitor. Large "audio grade" capacitors do not work well as input capacitors. Low ESR caps are especially unsuited for the task of input capacitors. Remember there's a 22Kohm resistor directly after it so the series resistance of any capacitor would be billions of times less than that anyways.

Last edited by Saturnus; 23rd March 2013 at 08:51 AM.
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Old 24th March 2013, 07:54 AM   #3628
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Yeah, that's all true!

The bad news:
I had an all afternoon long fight with my TA2020 over a reasonable input cap solution. The volume pot on one end and resistor on the other end made most capacitors that I had on hand. . . perform exactly like bad caps. After much effort, I ended up with a large composite mess that was unpleasant to build in such a tiny space, quite the eyesore, and works nicely. I did notice that the capacitance value had to be rather huge or else a) the tone changed with volume and/or b) bass blocker.
This amp behaves exactly like an inverting amp with the buffer omitted. For one passive part to replace several active parts is not simple but rather laborious. I hope that specifically recommended models of input cap are in the wiki???

The good news:
The spot for efficiency tuning worked much better with a cap in series with the woofer crossover. I simply found the smallest size cap that also couldn't interfere with the bass it could output. What I blocked is the workload of super-low bass the woofer couldn't output and now the amplifier will play twice as loud without clipping.

More bad news:
Then I added the ClipNipper circuit to the TA2020 so that when it did clip, it switched on a compressor so that clipping never reached the speaker. That worked okay until I tried battery power. Fail! My battery instantly "sank" to 9v and that wasn't compatible with my sensor.

More good news:
SO, instead of the compressor, what I really need to do is bi-amp. The tweeter-only amp won't clip, and that solves the audio quality problem easily.
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Last edited by danielwritesbac; 24th March 2013 at 08:06 AM.
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Old 24th March 2013, 10:26 PM   #3629
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If your battery is dropping so much voltage, it sounds like you either need one with lower internal resistance, or perhaps some bulk capacitors with low ESR to take the transients.

The other thing I'm curious about is the addition of a capacitor in series with the woofer. Surely that'd interact with the twin peaks of the ported box alignment. Results would be interesting.
I'd expect it to lower current draw, due to increased resistance at LF, but (assuming a rigid supply) shouldn't alter when the amplifier clips.

I think I'd go for a 2nd order HP filter on the input board, set it to ~50Hz. I'm fairly sure that could make up part of the buffer, too. A single TL072 would do the job nicely for both channels.

There'd be virtually no current flowing with a 2nd order filter, so you'd be able to eliminate the large caps needed for speaker-level filtering.

Chris
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Old 27th March 2013, 08:18 AM   #3630
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It's coming on, holes rounded over, centre brace made and rounded over...... Just waiting for delivery of some components, neutral cure silicone and yacht primer before assembly..... woo hoo, it won't be long at this rate

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