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Messages - flester

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106
The Newcomer's Forum / Re: First real build. LM386.
« on: January 02, 2018, 07:29:40 AM »
Doesn't really matter what brand you use. But before you order a new pot, you might want to try soldering a 1.5k resistor from wiper to ground, which will somewhat simulate the log curve.
Onlt asking about brands as the ones I got were trash. I think 10k is too much for the gain as its in parallel to a 1.35k res within thw chip. It works more like a high/low gain switch than a pot

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107
The Newcomer's Forum / Re: First real build. LM386.
« on: December 31, 2017, 09:21:57 AM »
Cool, congrats!

The gain and volume pots are supposed to be logarithmic, if yours are linear, then they probably have an exponential curve effect to the ear, as we percieve the power vs volume logarithmically. You can simulate the log response by putting a resistor from the wiper to tje ground, but then you need a bigger pot or to decrease the impedance going into the pot.

Glad to see it works, cheers.
Thanks I might try that. Just used the pots I had so I knew they might not be right. 1k lin was recommended for the gain but the vol specified 25ohm. (Ruby Amp project on generalguitargadgets.com). Certainly getting great enjoyment from the project and looking forward to playing it

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I tried making a few changes and basically all the 1k pots disintegrated from too much soldering and de soldering. So ended up with 10k linear for gain and no vol pot. Gain does nothing from 0 to 9 then it all happens between 9 and 10 so look likes i need a log pot. Any good suppliers or brands i should look for?


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108
The Newcomer's Forum / Re: First real build. LM386.
« on: December 21, 2017, 09:47:39 AM »
Cool, congrats!

The gain and volume pots are supposed to be logarithmic, if yours are linear, then they probably have an exponential curve effect to the ear, as we percieve the power vs volume logarithmically. You can simulate the log response by putting a resistor from the wiper to tje ground, but then you need a bigger pot or to decrease the impedance going into the pot.

Glad to see it works, cheers.
Thanks I might try that. Just used the pots I had so I knew they might not be right. 1k lin was recommended for the gain but the vol specified 25ohm. (Ruby Amp project on generalguitargadgets.com). Certainly getting great enjoyment from the project and looking forward to playing it

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109
The Newcomer's Forum / Re: First real build. LM386.
« on: December 20, 2017, 04:19:50 AM »
Since taking these photos I glued sheets of pickguard inside to provide support for the pots and jacks as the walls are rather thin. Also sub mini toggle switch in between the pots.

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110
The Newcomer's Forum / Re: Pot switch replacement on gorilla amp
« on: December 20, 2017, 04:15:33 AM »
I remember Gorilla amps from way back. 'A great little amp even if you dont wear socks'

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111
The Newcomer's Forum / First real build. LM386.
« on: December 20, 2017, 04:11:47 AM »
I mentioned this in other posts but heres a rundown as a novice on my LM386 build. I call it the Bearskin amp. Its a veroboard project very similar to the Little Gem , Ruby, and Smokey amps. No internal speaker. 1K gain pot plus a IK volume control on the output side.
Overall very pleased with this build. The only issue is the volume pot. It is linear slope but still seems more loggy if u know what I mean. Admittedly the quality of the pot is not great but maybe I need a different resistance or slope?

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112
Amplifier Discussion / Re: Capacitor conducting DC?
« on: December 14, 2017, 04:49:42 PM »
When tested with an ohm meter, every capacitor will conduct for a short period of time, depending on the RC charge time. R being the internal resistance of the ohm meter. If it conducts continuously, the cap went bad.
Thanks all. I just had no output or even a click when powered up. To be honest it ended up a mess with broken copper strips etc as I'm new at this. Just going to start again and use 8 pin socket instead of soldering chip to board. Have spares for all the parts anyway.

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113
Amplifier Discussion / Capacitor conducting DC?
« on: December 14, 2017, 09:24:10 AM »
Just troubleshooting an LM386 amp build on veroboard very similar to the Ruby Amp on runoffgroove.com. (it worked on breadboard!) when i do a continuity test one of the capacitors seems to conduct. Is this normal or does it indicate a bad capacitor? Its 100uF electrolytic.

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114
Amplifier Discussion / Re: USB charging
« on: December 13, 2017, 06:20:20 AM »
Safe?  No less safe that any other circuit you build.

Feasible?  Very simple circuit.

Make sense?  Not to me, maybe to other people.  Little plug into the wall chargers are cheap or even free:
https://www.4imprint.com/sampleitem/134168?gclid=EAIaIQobChMIzqD9itrN1wIVGLXACh0C4ACREAQYASABEgLXsfD_BwE&mkid=1pla-s134168&ef_id=Wbo0QgAABcNrZEKB:20171120174403:s

Otherwise, under $2:
https://repairpartsusa.com/dual-usb-home-charger.html?gclid=EAIaIQobChMIzqD9itrN1wIVGLXACh0C4ACREAQYAyABEgIlvPD_BwE

And I can locate those wherever I want, rather than having to go over to my stereo to charge up.

If I needed one in my stereo, and there was no convenience outlet on the unit, I might buy a cheap charger and take the circuit out of it and install that.
Thanks. Just worried about frying the battery or burning the house down. I found this charger circuit http://www.stufinnis.co.uk/pp3charger.html which should do the job though

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115
Amplifier Discussion / Re: Heatsinks for your poweramp
« on: December 11, 2017, 09:22:07 AM »
The LM386 is Not simply an opamp.
It is a power amplifier in it's own right.

The quiescent current with a 12Vdc supply is in the milliwatts.
So that wont make you say ouch.
The power dissipation of the package is 500 milliwatts (1/2 watt).
Again, no need for a heatsink.

If the device got that hot, it is hooked up wrong.
Most probably it is now bad.
Thanks. Almost certainly was mis-wired but have sorted it out and runs fine on the breadboard and no longer gets hot. Seems to still work but I have spares anyway

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116
Amplifier Discussion / Re: Heatsinks for your poweramp
« on: December 10, 2017, 05:49:31 AM »
Does an opamp  like the lm386 need a heatsink? While testing a breadboard build i pressed down on the chip and suddenly went ouch! as it had got pretty hot. (It may have been connected wrong ny the wau)t least I willl remember the name of the chip as its branded on my finger.







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117
The Newcomer's Forum / Re: Velleman Kit 4001
« on: December 02, 2017, 02:57:56 PM »
You can't reduce gain very much, I guess minimum is around 20X , because it becomes unstable.
So reduce R2/R1 ratio to about 20:1 but not less, any ectra reduction myst be input padding."Which is not all bad, you can add a passive tone conrol which will be lossy anyway.
OK here is plan B. I've been playing around with the Lm386 opamp and decided it might suit my little enclosure better than the TDA2003. I thought id use 2 of the TDA2003 modules with each one driving a 4" car  speaker in some sort of cabinet. Maybe shaped like the Roland Street Cube https://m.thomann.de/ie/roland_cube_street_bk.htm

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118
Amplifier Discussion / USB charging
« on: November 20, 2017, 07:17:14 AM »
Lots of stuff is USB chargeable these days. Is it feasible or safe to build in USB charging to a diy amp or other builds?

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119
Amplifier Discussion / Re: NO soldering wireless guitar amp project.
« on: November 16, 2017, 05:50:28 AM »
You can always insert a pot before the transmitter to wipe off some voltage.
Agree with Joe,,,,,Cool Idea :dbtu:
Yes great idea on the pot.
What I like is that I can play my electric travel guitar in anyones house, boat, car, caravan... as long as they have an FM radio. Lucky them!

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120
Amplifier Discussion / Re: NO soldering wireless guitar amp project.
« on: November 13, 2017, 02:44:23 PM »
Thanks. My first attempt at guitar amplification was trying to connect a soundhole pickup on my acoustic into the 'hifi' in my photo. Didn't really work, maybe better impedance matching would work but I was afraid of frying the hifi.

A few steps on I made a TDA2003-based amp, it's OK but clips rather harshly. Then someone gave me the headphone amp, I had the transmitter for playing MP3s in the car, one thing lead to another and this was the result. Hey, I can now play my Hofner Shorty in the car!

The amp has 'off', 'c' (clean) and 'd'  (dirty) settings. There is basically no clean sound because the amp causes the transmitter to clip even on 'c'. The 'd' just goes to cheap and nasty distortion which I kind of like. Vox make some headphone amps designed t emulate classic amps such as the AC30....

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