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Old 30th August 2003, 08:43 PM   #21
jleaman is offline jleaman  Belgium
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i should be starting my gain clone pretty quick. im thinking about heading up to my old town where my stuff is stored. ill pick my transformers up from storage and my aleph 2's stuff to start on them also. : O)

OHh to hear sound again. stupid mono speaker that is built into the mac tower is so QUIET and yeah.. LIMITED
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Old 3rd September 2003, 02:07 PM   #22
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Default here's a quad "ideal" GC Supplies

actually, they would be ideal for a lot of amplifiers -- will deliver 42 to 54 volts at 4 amps -- note the "blade" power lugs on the back -- the set failed to win $50 auction, now on at $30.
http://cgi.ebay.com/ws/eBayISAPI.dll...tem=2555300804
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Old 3rd September 2003, 02:45 PM   #23
joensd is offline joensd  Germany
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Quote:
I did some power testing for my dual LM3886 amp. I have non-regulated power supply. 8 parallel 33 ohm / 5W resistors were used as a load (= 4.125 ohms). I only tested one channel. I could only get 1 V p-p signal from my USB card. This was enough to get 18.9 V RMS or 55.2 p-p signal into load. This equals 86.6 Watts into one channel! The resistors soon got very hot, and i had to turn down power. The peak current was 6.6 A, still smaller than the 11.5 A current limit. There was no clipping. The ripple was 1.6 V. The supply voltage dropped from 33.0 V when idle to 31.4 V at full blast. I have 4*4700 uF capacitors on the PCB for power supply filtering and 2*24 V / 250 VA toroid transformer. The LM3886:s did not get very hot while testing.

See http://hepso/misc/Lm3886_amplifier.html for more details about the amp.
Hi,
Iīm always a bit puzzled when people write "the chips only get slightly warm" and the like cause the LM38XX chips are probably the "worst to cool"-amplifiers cause everything happens in a very limited space/volume.

At 35V rails which donīt sag down at full load you can indeed achieve a good 80W into 4Ohms but only at a power dissipation of 60W.
I mean we wonīt use that power level permamently
(in case we would thatīd be the last amplifier Iīd build)
but I canīt believe you didnīt burn your fingers or at least the temperature protection kicked in after a few minutes.

Show me your heatsink or go and check your skin with the doc.

Jens
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Old 7th September 2003, 11:40 PM   #24
Pedja is offline Pedja  Serbia
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Quote:
Originally posted by jkeny
Has anyone got report on how regulated supply sounds in comparison to no reg supply and if it worth buying parts & building
Pedja doesn't give much info - simply says it does all he expected it to do?
John
Hi John,

Yes, and it was about having a midrange as it is with unregulated 25V supply. But, using the same existing 1000uF as local decoupling caps, regulated supply has more airiness and bass is notably better (goes low as with 25V and is tight as with 30-32V unregulated supply). And then you can use here Black Gates (say 100uF or 220uF) without robbing the bank. With such supply for GC it might happen one will forget all the theories of musty energy in capacitors that kills the music. That enough?

Pedja
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Old 7th September 2003, 11:44 PM   #25
JoeBob is offline JoeBob  Canada
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After more listening I can agree with Pedja, the regulation I aplied was resulted in a sound that was definately better. I can't describe how things sound very well, but it was noticably better.
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Old 8th September 2003, 01:07 AM   #26
ukram is offline ukram  Finland
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Quote:
Originally posted by joensd

Hi,
Iīm always a bit puzzled when people write "the chips only get slightly warm" and the like cause the LM38XX chips are probably the "worst to cool"-amplifiers cause everything happens in a very limited space/volume.

Show me your heatsink or go and check your skin with the doc.

Jens
I'm using 10 mm thick aluminum, 100 * 100 mm, and aluminum case. My test was not very long, only about minute or two was enough to make the load resistors hot.

If the heat sink is thick enough, the chips don't get much warmer than the the heat sink. There must be enough metal to move the heat away from the chips. They say that silver is bad conductor, copper is worse and aluminum is really bad...

Has anybody tried to build a GC with silver heat sink? That would be high-end
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Old 11th September 2003, 05:47 PM   #27
joensd is offline joensd  Germany
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Quote:
I'm using 10 mm thick aluminum, 100 * 100 mm, and aluminum case. My test was not very long, only about minute or two was enough to make the load resistors hot.
That makes perfect sense then.
Most of the gainclones seen here donīt have that thick bare metal to move the heat from the chip very fast.
I used a little cooling tube with a little fan which is very effective once itīs hot but it wasnīt able to move it away from the chip fast enough.
Added a thick peace of aluminium and it did the trick.

Quote:
Has anybody tried to build a GC with silver heat sink? That would be high-end
Canīt seem to find the sheets for heat conductance of different metals but from my memory : Is it really worth it?
What about gold then.

Cheers
Jens
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Old 11th September 2003, 06:35 PM   #28
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Default thermal conductivity

gold is worse
silver is the best heat conductor metal, copper is second, alu third, as ukram already told.
in these materials (metals) thermal conduction is dominated by electron movement, so electrical conductivity behaves same as thermal.
Diamond for example is also a good heat conductor, but is electrically isolating. Thermal conduction here is by phonons (lattice movement).
Now, a silver heatsink, and diamond isolation material, that is high end!
Copper is already MUCH better than Alu, and Silver is not so much better than copper.
You could easily build a GC with a copper heatsink for a PC.
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Old 11th September 2003, 06:48 PM   #29
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METALS>??????? and here all along I thought they were an alloy
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Old 11th September 2003, 06:52 PM   #30
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I think they are all metals, and alloys are made by combining them

I followed Thorsten's suggestion and decided to use Bronze for heatsink. It's pretty expensive thou, 1 foot of 2 x 3/4" bar is $85.
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