Miguel,
I check, rechecked, and checked some more. i am sure I missed something! Could damage occur from soldering. However, I did not overdo the soldering at all.
I am using LM3875. I am not aware of any enable pin.
I received 4 samples from National and none of them produce sound. I am probably doing something sytematically wrong.
Anyone else out there with such misfortune?
Vic
I check, rechecked, and checked some more. i am sure I missed something! Could damage occur from soldering. However, I did not overdo the soldering at all.
I am using LM3875. I am not aware of any enable pin.
I received 4 samples from National and none of them produce sound. I am probably doing something sytematically wrong.
Anyone else out there with such misfortune?
Vic
Good news, bad news.........
First the good news. I had a bad transformer. While investigating my connections for the 1000th time, I began to hear some crackling. Next, a foul smell. and then smoke from my transformer. I connected another transformer. The heavens opens and sound emitted from my test speaker!
Now, the bad news. Overconfidently, I connected my power setup to the right channel. The ground connection shorted against the LM3875 case. First a 'pop', then the chip began glow between the metal backing and the case and between around pins 4 an 7. I stood there like an idiot thinking, "Wow, it continues to heat up for some reason." I was so caught up in the intersting situation unfolding before me that I didn't kill the power supply. It began to smoke badly.
Well, at least I figured out my problem.
At this rate I could start a new thread on "Not just another A-hole's gainclone" I where would be the main contributer.
First the good news. I had a bad transformer. While investigating my connections for the 1000th time, I began to hear some crackling. Next, a foul smell. and then smoke from my transformer. I connected another transformer. The heavens opens and sound emitted from my test speaker!
Now, the bad news. Overconfidently, I connected my power setup to the right channel. The ground connection shorted against the LM3875 case. First a 'pop', then the chip began glow between the metal backing and the case and between around pins 4 an 7. I stood there like an idiot thinking, "Wow, it continues to heat up for some reason." I was so caught up in the intersting situation unfolding before me that I didn't kill the power supply. It began to smoke badly.
Well, at least I figured out my problem.
At this rate I could start a new thread on "Not just another A-hole's gainclone" I where would be the main contributer.
Don't let it get you down Ric. Anyway you have found out what the problem was and, as they say, the man who never made a mistake, never made anything.
At least with the Gainclone, replacing the parts won't cost too much to have another go. Keep persevering because the end result is worth the effort.
Bricolo, yep. you can see in the pics they've been replaced with some cheapies till i can get new Panasonics.
btw, the cheapies have a noticable different sound which is worse.
after replacing one the first time it blew and watchin it blow again lol, i knew i had a problem. took some time to notice the mistake.
btw, the cheapies have a noticable different sound which is worse.
after replacing one the first time it blew and watchin it blow again lol, i knew i had a problem. took some time to notice the mistake.
Blow it up!
Hey Matttcattt,
How about putting some tape isolating the caps?
Don´t worry, some days ago i blew up a crappy transformer.
I'm doing a Gainclone too, I'll report later.
What happened is that I finished the first channel, and was testing with a portable minidisc and a crappy speaker.
While I'm waiting for the new transformer to arrive, I tested it with a crappy old 2x12V/1.5A transformed I had.
Let me tell you it worked fine a first power on.
I was so happy with the sound coming from the speaker that I started raising and raising the volume until the sound stoped.
0 volts on the secondaries of the transformer...
And not even a little smoke!
Oh well...
I'm waiting to receive my 2x24V/8A (that's 8A for each primary) toroid, custom-built to my requirements.
Then I'll test it properly, and make the other channel.
Hey Matttcattt,
How about putting some tape isolating the caps?
Don´t worry, some days ago i blew up a crappy transformer.
I'm doing a Gainclone too, I'll report later.
What happened is that I finished the first channel, and was testing with a portable minidisc and a crappy speaker.
While I'm waiting for the new transformer to arrive, I tested it with a crappy old 2x12V/1.5A transformed I had.
Let me tell you it worked fine a first power on.
I was so happy with the sound coming from the speaker that I started raising and raising the volume until the sound stoped.
0 volts on the secondaries of the transformer...
And not even a little smoke!
Oh well...
I'm waiting to receive my 2x24V/8A (that's 8A for each primary) toroid, custom-built to my requirements.
Then I'll test it properly, and make the other channel.
I have finished both channels of my gainclone using the OPA548, and i like how it sounds, i now want to make one with the OPA541 as i have 2 of these. i have two power suplys, one is +/- 15v with 33000uf and the other is 35v with 2200uf, which power supply would be better with which amp?
i also want to try bridging and parrelleling and i want to know which i should try first.
what sort if speaker cable is best suited to gainclones? solid core or stranded cable? thick cable or thin cable? i have some cat5 cable (some stranded, some solid core) and i dont know wether to use a single pair for both or wether to wire all the pairs together.
i also want to try bridging and parrelleling and i want to know which i should try first.
what sort if speaker cable is best suited to gainclones? solid core or stranded cable? thick cable or thin cable? i have some cat5 cable (some stranded, some solid core) and i dont know wether to use a single pair for both or wether to wire all the pairs together.
Sorry for breaking the conversation.
I've made a prototipe amplifier with inverted LM3886. I have 21V dual secondary 300VA transformer
and 19000uF per rail for now, maybe I'll take quarter of that on the end or who knows. It is going
to fit in the box I have this way or the other one. I've made a tiny PCB (40x44mm) for it.
When I measured the DC offset, great, only 1.4mV, but I'am not sure if it is oscilating, because
there is 50mA drown from minus of PS, and 50 from plus with no load. I remember reading from the
datasheet that the total quiescent current is 50mA, but I'am not sure if it means 25mA from +,
and 25mA from - of PS? Otherwise it could be the oscilations that I'am not in position to detect
because I have no osciloscope.
I need some help.
Tomorrow I'll probably post a photo of PCB and the prototipe.
thanks,
mario
I've made a prototipe amplifier with inverted LM3886. I have 21V dual secondary 300VA transformer
and 19000uF per rail for now, maybe I'll take quarter of that on the end or who knows. It is going
to fit in the box I have this way or the other one. I've made a tiny PCB (40x44mm) for it.
When I measured the DC offset, great, only 1.4mV, but I'am not sure if it is oscilating, because
there is 50mA drown from minus of PS, and 50 from plus with no load. I remember reading from the
datasheet that the total quiescent current is 50mA, but I'am not sure if it means 25mA from +,
and 25mA from - of PS? Otherwise it could be the oscilations that I'am not in position to detect
because I have no osciloscope.
I need some help.
Tomorrow I'll probably post a photo of PCB and the prototipe.
thanks,
mario
They chosen like that because Riken isn't available in less than 0.5W, but if you use different type choose the Wattage that fits best between the pins of the chip (between - input and output). 0.5W is actually a bit too long. 1/8W Holco might be a good alternative.
I started using 1W 10K Rikens because this is what I was given at the beginning, later had a chance to compare it with 0.5W version and 1W sounds indeed better (it is also 1.5 times more expensive). So I would say the wattage values are also selected for better sound. In my case the path length from input jack to the chip is more than 3 resistor lengths so 1W fits better here as well
I started using 1W 10K Rikens because this is what I was given at the beginning, later had a chance to compare it with 0.5W version and 1W sounds indeed better (it is also 1.5 times more expensive). So I would say the wattage values are also selected for better sound. In my case the path length from input jack to the chip is more than 3 resistor lengths so 1W fits better here as well
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