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Old 20th January 2013, 10:23 PM   #2341
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Default Newbie

Hi Guys,

I'm new to the DIY Audio world but after some research i decided to build an LM3886 amplifier, having very little knowledge i found the challenge somewhat daunting.
My first prototype is pictured below. I was firstly surprised that it worked!! and pleasantly surprised at the quality of the sound. However, i decided to build 2 mono amps. I picked up a couple of 'kit chassis' as you can see from the photos, the transformers don't quite fit. This is for cooling purposes obviously!!.
My main gripe with these amps is the cheap and wobbly volume control. Has anyone got any good ideas how to dampen them to give a more quality feel?
Please bear in mind that these amps are my first effort.
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File Type: jpg amp photo 1.jpg (543.6 KB, 1300 views)
File Type: jpg amp photo 2.jpg (599.8 KB, 1236 views)
File Type: jpg photo.jpg (555.4 KB, 1225 views)
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Old 26th January 2013, 11:06 PM   #2342
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Hi! I've been following this thread for some time and now I'm posting some photographs of a little amplifier intended to be used for my tweeters in a multiamplified system. It's entirely "hand-made" because in my country it's quite difficult to obtain a chassis.

Click the image to open in full size.

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Click the image to open in full size.

Best whishes!
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File Type: jpg 2x20W-arriba.jpg (110.1 KB, 1561 views)
File Type: jpg 2x20W-fondo.jpg (111.0 KB, 1464 views)
File Type: jpg 2x20W-frente.jpg (71.7 KB, 1433 views)
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Old 27th January 2013, 12:01 AM   #2343
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Oooppss! I forgot to explain:
This amplifier is just a couple of LM1875 chips operating with a PS of +/-16V DC, enough to put 20W on each DX25 tweeter.
The PCB in the lower right is an speaker protector and on/off muting unit.
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Old 28th January 2013, 03:55 AM   #2344
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This LM1875 inverted amplifier was built during the New Year holidays. This is my first musical amplifier and it was inspired by projects from Maarten&Annemarie webpage. I call it 'Old Fashioned' because of its chassis-box structure. Works nicely with my AR10pi boxes (set to 1pi, -6dB, -6dB).
Click the image to open in full size.
Click the image to open in full size.
Click the image to open in full size.
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Click the image to open in full size.
Click the image to open in full size.

Last edited by fromthecrowd; 28th January 2013 at 04:09 AM. Reason: pictures did not show
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Old 28th January 2013, 08:49 AM   #2345
AndrewT is offline AndrewT  Scotland
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Click the image to open in full size.
That's what everyone will recognise as a Star Ground.
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Old 28th January 2013, 09:44 AM   #2346
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That's what everyone will recognise as a Star Ground.
That's output or power star ground. There is also signal star ground on the ground contact of the pot. Can be seen on 4th photo. At first I made one single star ground for everything, but the sound was rather poor. When input ground of the RCA plug was moved to the pot contact, the sound improved. Later I also moved the opamp positive input resistor to this point. Cannot say if this was right thing to do. There are suspicions, that the sound got worse.
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Old 28th January 2013, 10:04 AM   #2347
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Yepper. Nice work. I might've put a lock nut on there. I'm impressed with the chassis work on these last two builds. And ya gotta dig that red heat sink.
gavlar, you ask an interesting question. If you don't want to replace those volume pots, maybe you could place a felt pad between that coupler and internal panel to provide some friction for better feel. I've never really seen this addressed so don't have any answer at the ready. And in the future you may be able to find a lid or can bottom or some such to place over those transformers. You've still earned some props for your first build.
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Old 28th January 2013, 12:04 PM   #2348
JMFahey is online now JMFahey  Argentina
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@ fromthecrowd: *incredibly* creative use of standard aluminum extrusions. Congratulations.

@ ezavalla: did you cut and fold that cabinet ?
Looks real Pro.
I instantly recognized the Delza ZD14 heat sink
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Old 28th January 2013, 11:53 PM   #2349
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@ ezavalla: did you cut and fold that cabinet ?
Looks real Pro.
Yes, this time the guy who sells the metal sheets allowed me to cut and fold them (I guess he was a bit busy). I usually give him a draw and he cuts and folds the sheet for me.. and it is a dirty cheap task, so it's better to let him to do the job

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I instantly recognized the Delza ZD14 heat sink
Yes, it is a ZD14 heatsink.. about 10cm x 5cm tall.. something like 3șC/W.. but the tweeters level is low, so not to much danger there
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Old 30th January 2013, 06:36 AM   #2350
child1 is offline child1  Denmark
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Default Soundbar project

Hi All!

Wasn't really sure where to post this, so feel free to move this reply if it fits in better some other place

Anyways - thought I would post a picture of my finished soundbar project, so here it is!

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