Hi Skyraider;
>>>...I used shielded audio cable for the inputs too...<<<
That's next - I just spent all day moving the rear chip to sit alongside the front and have just passed the first hour of a medium power test into a pair of RS40-1354/RS40-1270D speakers. So far so good (*knocking on wood* as I type for good luck!!). Even after a 10 minute high power test (volume maxxed) it didn't get particularly warm - just slightly warm to the touch.
>>>...I copied off the PCB design that is recomended in the datasheet, it has HUGE tracks to cope with all the currents...<<<
Hmmm, I need to learn and practice making my own PCB's. For now, I'm still sticking to the "tried and true" point to point wiring that has carried me through my valve projects. I wish I had a pic of the amp modules as assembled - I used 1/8 watt resistors for the feedback loop (and the resistor/cap loop between pins 2 and 4) - those little buggers actually fit in between the pins! And the diodes are 1N4007's with only about 1/16" of lead left that's bent into a hook - they slip in between the pins as well (after a little gentle bending).....
How's the 3886 going? I saw your other posts on it. Did you try fitting the PS decoupling caps directly to the chip's pins? That was the final ingredient to success on the oscillation front over here.
Good luck and all the best!
Morse
>>>...I used shielded audio cable for the inputs too...<<<
That's next - I just spent all day moving the rear chip to sit alongside the front and have just passed the first hour of a medium power test into a pair of RS40-1354/RS40-1270D speakers. So far so good (*knocking on wood* as I type for good luck!!). Even after a 10 minute high power test (volume maxxed) it didn't get particularly warm - just slightly warm to the touch.
>>>...I copied off the PCB design that is recomended in the datasheet, it has HUGE tracks to cope with all the currents...<<<
Hmmm, I need to learn and practice making my own PCB's. For now, I'm still sticking to the "tried and true" point to point wiring that has carried me through my valve projects. I wish I had a pic of the amp modules as assembled - I used 1/8 watt resistors for the feedback loop (and the resistor/cap loop between pins 2 and 4) - those little buggers actually fit in between the pins! And the diodes are 1N4007's with only about 1/16" of lead left that's bent into a hook - they slip in between the pins as well (after a little gentle bending).....
How's the 3886 going? I saw your other posts on it. Did you try fitting the PS decoupling caps directly to the chip's pins? That was the final ingredient to success on the oscillation front over here.
Good luck and all the best!
Morse
Morse,
Ive completed my LM3886 an hour ago, it is still abusing my neighbours untill now=)
I found out my problems, it is oscillation due to improper ground lines. To fix it, I rewired everything, I discard the PCB, used P2P wiring. Every ground line is connected to a perfect star, making it like an ideal sink/source. Now the hissing noise is barely audible, and I will post my mistakes and its fixes in the forum later. Thanks u guys=)
I am thinking of starting tube projects soon, once I can track down a good transformer manufacturer. I might need your advice later in future, morse.
Ive completed my LM3886 an hour ago, it is still abusing my neighbours untill now=)
I found out my problems, it is oscillation due to improper ground lines. To fix it, I rewired everything, I discard the PCB, used P2P wiring. Every ground line is connected to a perfect star, making it like an ideal sink/source. Now the hissing noise is barely audible, and I will post my mistakes and its fixes in the forum later. Thanks u guys=)
I am thinking of starting tube projects soon, once I can track down a good transformer manufacturer. I might need your advice later in future, morse.
Even though Im new here, in my opinion. chipamps are better wired P2P. They have very minimum external components, and a properly designed P2P has very short signal path, reducing noise pickups, and thick cables can be used for high current lines, etc. Very often poorly designed PCBs produces lots of noises, and I dont believe PCB tracks are ever thick enough for the earth currents.
as usual, correct me if im wrong=)
as usual, correct me if im wrong=)
Hi Skyraider;
Glad to read that you got the 3886 off the ground!
Interesting comparison of P2P vs PCB wiring! I should still learn to make my own PCB's though....one of these days I'd like to scratchbuild a CD player and that would be a pain P2P. 'Course the audio amp section of that would be with valves if the wallet will bear it.... 😉
>>>...I am thinking of starting tube projects soon, once I can track down a good transformer manufacturer. I might need your advice later in future, morse...<<<
Ask away, or email me whenever you have questions if you ever want advice on valve amps. I've made my share of mistakes - and have some nice successes too. For pics, my site's over at http://home.earthlink.net/~shidenkai/index.html
All the best,
Morse
Glad to read that you got the 3886 off the ground!
Interesting comparison of P2P vs PCB wiring! I should still learn to make my own PCB's though....one of these days I'd like to scratchbuild a CD player and that would be a pain P2P. 'Course the audio amp section of that would be with valves if the wallet will bear it.... 😉
>>>...I am thinking of starting tube projects soon, once I can track down a good transformer manufacturer. I might need your advice later in future, morse...<<<
Ask away, or email me whenever you have questions if you ever want advice on valve amps. I've made my share of mistakes - and have some nice successes too. For pics, my site's over at http://home.earthlink.net/~shidenkai/index.html
All the best,
Morse
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