My monoblock Gainclone LM3886 (photos link) - diyAudio
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Old 10th March 2005, 10:08 PM   #1
steeve is offline steeve  Greece
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Join Date: Nov 2004
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Exclamation My monoblock Gainclone LM3886 (photos link)

My amps built a year ago:

http://briefcase.pathfinder.gr/contents/stry/25160

Any comments welcome

WARNING: large pics !
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Old 10th March 2005, 10:40 PM   #2
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Are you going to put them in cases? Perhaps plexiglass.
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Old 11th March 2005, 07:41 AM   #3
rodolfo is offline rodolfo  Mexico
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Thumbs up nicee

very nice work
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Old 11th March 2005, 10:15 AM   #4
stry is offline stry  Greece
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jaudio,

this is my final assembly (acc to my tastes).

Characteristics:

No hum, no strange offsets (< 20 mV), no heating (when driving 84dB 4-ohm speakers), after 1 year.

Includes zobel and coil at the output.

The building platform is solid copper 10 mm!

Includes thermometer on top (at the first days, oscillation was a frequent phenomenon, and this was VERY useful !).

Cap bank is ELNA cerafine (before, i included 10.000 uF bank in parallel, but something bad happended with the bass. ... you know)

Trafos are 300 VA (custom order)

No FUSES (direct connection to mains)!

Not MUR 860 diodes (!)

Special internally hardwired ac outlets, only for two GCs

... and sound? Very very good, but ... remember: my speakers (Audio Phycic Step SLE) are not an optimum match.

PS. A lesson for me: NEVER use cap in the feedback loop of such an amplifier !!!
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Old 11th March 2005, 11:13 AM   #5
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"Includes thermometer on top (at the first days, oscillation was a frequent phenomenon, and this was VERY useful !)."

How was the thermometer used?

How was the oscillation problem fixed?
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Old 11th March 2005, 02:11 PM   #6
stry is offline stry  Greece
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Simply,

the thermometer exceeded 49oC reading during oscillation
Now, never exceeds 30oC.

Problems fixed by removing the cap from the feedback loop and by setting a 47 k resistor input (-) to ground.
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Old 11th March 2005, 07:41 PM   #7
DC Dave is offline DC Dave  United States
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Quote:
No FUSES (direct connection to mains)!
Sounds like a fire hazard to me. You shouldn't get in the habit of building anything mains powered without using fuses, IMHO.
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Old 11th March 2005, 09:37 PM   #8
steeve is offline steeve  Greece
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DC dave,

this will terrify you:

My other amp, McCormack DNA 0.5, with upgraded power supply (2 x 600 VA + 1 x 300 VA, 100.000uF total) is also direclty connected to mains (direct run to the power switchboard).

Also all four fuses at the output stages have been removed.

Of course, operation is always supervised.

But, all good (sound) things have a cost: A fatal short circuit (during the mis-insertion of a plug) burnt a handful of fets and transistors.

Anyway, i must say that i trust GC as it is. One year now and is very stable.
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