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Cmoy first build questions - Page 3

post #31 of 60
9/6/10 at 12:20pm
Thread Starter 

heres a new shopping basket.cmoy list.bmp i have a dc plug, and 2200 25v caps.

could somenoe ecplain what the gain does? thanks rob cmoy list.bmp

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post #32 of 60
9/6/10 at 7:04pm

Your shopping basket didn't show up...

 

Gain is basically by how much it amplifies the incoming signal.

A gain of 1 means that it does not amplify at all.

A gain of 2 means the signal level doubles.

More exactly, if you have 1 volt going in, you get 2 volts coming out.

For a gain of three, 1 volt in gets you 3 volts out, and so on...

If your gain is too low you will find yourself with the volume

all the way up and still not loud enough. If the gain is too high

you might have hiss all the time and barely be able to turn up

the volume before it is too loud. The trick is finding just the right

gain for you...

Most people find a gain of 5 seems to work best in most situations.

Myself, I use a lower gain, 2 or 3. My headphones are sensitive and

my source are pretty strong to start with so I don't need much gain.

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post #33 of 60
9/7/10 at 11:36am
Thread Starter 

ok, thanks. thats strange the shopping basket works for me? i will do it again later.

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post #34 of 60
9/10/10 at 11:35am
Thread Starter 

ok, here is my new shopping basket:

 

1.
 62-7273
4 Available 47R 2W 1% METAL FILM RESISTOR RC £0.0700 £0.28
2.
 20-0155
4 Available 3.5MM STEREO JACK SOCKET (RC) £0.1800 £0.72
3.
 10-5778
4 Available 1UF 100V 10% MET POLYESTER CAP (RC) £0.1000 £0.40
4.
 18-0105
4 Available PP3 / PP6 BATTERY CLIP 150MM (RC) £0.0600 £0.24
5.
 32-0465
2 Available 16MM KNOB WITH BLUE POINTER (RC) £0.1400 £0.28
6.
 11-3728
4 Available 2200U 25V RADIAL ELECTROLYTIC (RC) £0.1300 £0.52
7.
 62-7285
6 Available 10K 2W 1% METAL FILM RESISTOR RC £0.0700 £0.42
8.
 62-7291
4 Available 100K 2W 1% METAL FILM RESISTOR RC £0.0700 £0.28
9.
 65-1460
2 Available 10K log dual 16mm control £1.6900 £3.38
10.
 22-1720
2 Available 8 PIN 0.3IN TURNED PIN SOCKET(RC) £0.1400 £0.28
11.
 55-1478
2 Available L-7104QBC-D 3mm Blue LED 1500mcd £0.3400 £0.68
12.
 75-0125
2 Available SPST MINIATURE TOGGLE SWITCH ON-OFF(RC) £0.4900 £0.98
13.
 62-7283
4 Available 4K7 2W 1% METAL FILM RESISTOR RC £0.0700 £0.28
14.
 62-7922
4 Available 1K 1W METAL FILM RESISTOR (RC) £0.0800 £0.32
Totals    £9.06 £9.06
Spend another £20.94 to qualify for Free Delivery (UK Mainland Only)
Delivery    £4.95
Sub Total    £14.01
VAT    £2.45
Grand Total    £16.46

i am not going to bother having a wall plug, as it is extra complication, and i doubt i would use it, as i have a full sized surround amp at home :)

i am going to get school to order the stuff, as then i save £5 on postage :)

when i get the parts, i will use this as a build thread.

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post #35 of 60
9/10/10 at 2:07pm

You don't need the high watt resistors, .250 (1/4) watt will do nicely.

On the other hand, they won't be a problem either, just bigger than

they need to be.

Other than that, everything looks OK.

 

Good luck with your build

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post #36 of 60
10/4/10 at 12:22pm
Thread Starter 

ok i have ordered these opamps from ebay, they are cheap, and GENUINE!!!

i will see which i prefer. I am waiting for an ebay seller to get more stock of their radio shack lookalike pcb, and my school to put in the order.

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=260655563826&ssPageName=STRK:MEWNX:IT

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=260655962997&ssPageName=STRK:MEWNX:IT

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post #37 of 60
12/10/10 at 12:35pm
Thread Starter 
Hi,
I haven't posted here for a while, but I have now got all the necessary components and soldering iron tip. I have soldered the power supply on one of my cmoys, and it works!!! I get just over 10v on both channels (it started at 18v?) after a little playing with a craft knife. My soldering is not pretty, but the voltage readings are ok, and the only bridges (that I know of) are ones where the jumpers are. Just one question, when I disconnect the batteries, why does my led stay on for a whilst afterwards? Is this meant to happen?
Thanks
Rob
Ps. I will get some pics biggrin.gif
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post #38 of 60
12/10/10 at 12:41pm


The LED is using the power stored in the supply caps.

 

Quote:
Originally Posted by Rchez08 View Post

Hi,
I haven't posted here for a while, but I have now got all the necessary components and soldering iron tip. I have soldered the power supply on one of my cmoys, and it works!!! I get just over 10v on both channels (it started at 18v?) after a little playing with a craft knife. My soldering is not pretty, but the voltage readings are ok, and the only bridges (that I know of) are ones where the jumpers are. Just one question, when I disconnect the batteries, why does my led stay on for a whilst afterwards? Is this meant to happen?
Thanks
Rob
Ps. I will get some pics biggrin.gif
Reply
post #39 of 60
12/10/10 at 2:19pm
Thread Starter 
Ok thanks. I'm guessing cos I am using big caps it carries on for a long time.
I may solder up the amp section tomorrow, but I will atleast try and get some pics biggrin.gif does it matter if the solderings messy?
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post #40 of 60
12/10/10 at 2:22pm

We all had to learn to solder at one time or another...I bet

my soldering was pretty poor the first time.

The more you do it, the better you should get at it.

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post #41 of 60
12/13/10 at 2:10pm
Thread Starter 
Ok, thanks for your comments. I have now fully assembled the amplifier smily_headphones1.gif it works, but I haven't noticed a real increase in quality, only in volume, which my headphones decide to fuss at :/ time for some grados or sennheisers I guess... or not wink.gif I need to now case up the amp. I'm thinking of a wooden box, to stop any shorting, and the components are a bit bigger than I expected, so no altoids tin :/.
The only one thing I have noticed with it is that the volume control is really sensitive. If I had my iPod on full, it would take only the tiniest turn to get it to blast out, and then once it got about halfway round there was no real increase. Any idea if I could fix this easily? Or is it just how it will be (I can always just lower the volume on my iPod.
Rob
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post #42 of 60
12/13/10 at 3:13pm

Try turning the ipod all the way down, turn the amp all the way up.

Slowly increase the volume on the ipod to a comfortable listening level.

Does the volume on the amp now work as expected?
 

Quote:
Originally Posted by Rchez08 View Post

Ok, thanks for your comments. I have now fully assembled the amplifier smily_headphones1.gif it works, but I haven't noticed a real increase in quality, only in volume, which my headphones decide to fuss at :/ time for some grados or sennheisers I guess... or not wink.gif I need to now case up the amp. I'm thinking of a wooden box, to stop any shorting, and the components are a bit bigger than I expected, so no altoids tin :/.
The only one thing I have noticed with it is that the volume control is really sensitive. If I had my iPod on full, it would take only the tiniest turn to get it to blast out, and then once it got about halfway round there was no real increase. Any idea if I could fix this easily? Or is it just how it will be (I can always just lower the volume on my iPod.
Rob
Reply
post #43 of 60
12/13/10 at 3:29pm

Have you got a linear or log pot? you need a log for smooth volume increaes, it should have an A ie 10KA or A10K stamped on the body

 

cheers

FRED

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post #44 of 60
12/13/10 at 11:14pm
Thread Starter 
Dammit. It says 10pm frown.gif I swear I ordered a log pot.
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post #45 of 60
12/13/10 at 11:56pm

I've not seen 10pm on a pot but it doesn't sound like a log pot so the volume will be very sensitive in the first bit of travel, in fact a PITA to listen to :-)

 

cheers

FRED

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