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Chip Amps Amplifiers based on integrated circuits

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Old 25th February 2003, 04:51 AM   #11
cowanrg is offline cowanrg  United States
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Quote:
Originally posted by Steve Eddy


Um, that circuit needs to be powered with a bipolar supply. In other words, +V and -V. If you're using two 12 volt batteries in series and running a straight 24 volts to the power supply pins on the chip, it's not going to work properly with that circuit.

You'll need to use the batteries like this:

It sounds like you may have it hooked up to a single 24 volt supply.

The LM-3875 can operate from a single supply, but not using Peter's circuit.

se
ah cool. i can try that... so basically use the point where i connected the positive to negative to make the series, and make that the ground? i can try that. the batteries have plenty of juice i think. they are like 5 pounds each.

i still have a question of if that transformer will work for this application. i just want something to test it out, so i can see how this damn thing sounds.
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Old 25th February 2003, 05:00 AM   #12
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Quote:
Originally posted by Peter Daniel
I tried it with my Aleph X and it definitely influences sonics. With the resistor in place, the amp seems to be cleaner (or smoother) sounding. I don't really know the reason behind it.
Could be because it's loading down the output stage of your source component. With that 50k resistor (or using the pot with the volume turned all the way up) your input impedance is about 8.3k.

Shouldn't be a problem for most solid state output stages, but a lot of tube output stages may start to choke on it.

Also, the lower the input impedance, the more significant the effects of cable capacitance, i.e. it will start rolling off the highs at a lower frequency.

That perhaps might also explain why it sounds smoother.

Anyway, as long as you like the result that's all that counts.

se
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Old 25th February 2003, 05:02 AM   #13
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Quote:
Originally posted by cowanrg


ah cool. i can try that... so basically use the point where i connected the positive to negative to make the series, and make that the ground? i can try that. the batteries have plenty of juice i think. they are like 5 pounds each.
Well, the point where you connected the positive and negative battery terminals to wire them in series, yes.

And how much juice the batteries have depends not on their weight but how much juice they have. If they've been discharged, it doesn't matter how heavy they are, they'll be out of juice.

Quote:
i still have a question of if that transformer will work for this application. i just want something to test it out, so i can see how this damn thing sounds.
Sorry, I missed that question. What transformer do you mean?

se
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Old 25th February 2003, 05:17 AM   #14
cowanrg is offline cowanrg  United States
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this transformer:

http://www.allelectronics.com/cgi-b...-245&type=store
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Old 25th February 2003, 05:19 AM   #15
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Sorry, that link doesn't work for me.

se
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Old 25th February 2003, 05:20 AM   #16
cowanrg is offline cowanrg  United States
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try this then...
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Old 25th February 2003, 05:26 AM   #17
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Worked that time, thanks.

Yes, that transformer will work.

se
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Old 25th February 2003, 05:42 AM   #18
cowanrg is offline cowanrg  United States
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cool. gonna order a couple and see how they work.

gonna fix my circuit too and see if i can get something out of it. well, something better than before at least
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Old 25th February 2003, 05:47 AM   #19
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Quote:
Originally posted by cowanrg
gonna fix my circuit too and see if i can get something out of it. well, something better than before at least
Good luck!

se
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Old 25th February 2003, 06:13 AM   #20
cowanrg is offline cowanrg  United States
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well, im listening to it now.

it doesnt have that NASTY noise in the background. however, i put in that 50K resistor like peter said, and there is a nice BUZZ in the speaker. and, its very quiet. i tried without, and its fine.

also, i am not using the 4.7uf cap on pin 8. the idiot at the electronics store forgot to put it into my bag maybe that has something to do do with it. i will say this thing has some POWER. im not 100% quality, but that's partly due to the power its getting probably... in the 5 minutes ive been listening to it, its gone from 26.4 volts, down to 25.33 and dropping as we speak.

any ideas as to why adding that resistor adds so much hum? (from the ground, i have a kinda star ground, and from that there is a lead going to the ground on the rca jack, and in between the star ground and the rca ground, im connecting it... i hope thats right...)

oh yeah, is there any way to avoid that nice thump when i connect the positive and negative? will a switch stop that, or do i need a soft start circuit?
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