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Old 21st September 2003, 07:11 PM   #11
joensd is offline joensd  Germany
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Quote:
- who likes hot tea while listening to music... ;-P
Me!
Most of the time I prefer a cold can but sometimes a hot tea is just right.
You might laugh thinking about it but I originally planned my class-a headphone amp for the PC so that the heatsink sits on top and I can put my cup on it...

Jens - thinks that this forum is just right for fanatics
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Old 23rd September 2003, 01:59 AM   #12
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My amp is a Kenwood 100Wx2, from I think circuit city. I don't know if that matters, but do you think the 3886s wil provide better sound?

-Mike
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Old 23rd September 2003, 02:11 AM   #13
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Go to a PA equipment store and listen to the active studio monitors with CDs you are familiar with. Brands like Mackie and Genelec use chip amps in their power packs.

I have a pair of Yorkville YSM1p's and they have 3886's inside. They are a steal at about $800 Cdn for the pair.

:)ensen.

Warning, once you listen to studio monitors, you'll wonder why they are so inexpensive.
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Old 25th September 2003, 01:28 AM   #14
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I was wondering if it was possible to make the amps switch between normal, bridged and parallel. I know you can use a DPDT switch for bridged/normal, but I have never used parallel before and was wondering if I could make a stereo amp using 4 3886s and be able to switch between the 3 modes. I am using the schematic on the first page of nationals datasheet

Thanks for the help, Mike
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Old 25th September 2003, 03:27 AM   #15
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Quote:
Originally posted by soundNERD
Also, does anybody know where I could find that paper that lets you print PCBs from a laser printer for the chapest? I choked when I saw DigiKeys price for only 5 sheets.
I'd HIGHLY recommend not going for cheap stuff here. My friend and I tried SEVERAL methods including transparencies, "treated" transparencies, HP Photo paper, etc etc...ALL came out with poor results that required about 30+ mins on PCB pen work on either side of the board. We then discovered Press N' Peel Blue...works perfectly. Honestly, I can't tell you how much time, effort, and money we put in before the press n' peel. The stuff may be a bit expensive but it's worth it. Try:

http://www.techniks.com/
http://www.allelectronics.com/cgi-bi...e&category=445

Hope it helps,

Doovieman
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Old 25th September 2003, 04:22 AM   #16
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also, with the 38xx chips (3886 and 3875), a lot of people have had success with just p2p wiring, obviously make sure the pins are not touching anything bad, as you could start a fire...

the 4780 chips have pins a little too close to try this type of mounting.
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Old 26th September 2003, 01:51 AM   #17
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Can you elaborate a bit more? do you mean p2p as in run the output from one amp through the input of the next?

Also, can the LM3886 drive a 8, 4 or 2 ohm load in normal mode? or just 8 and 4?


Thanks, Mike
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Old 27th September 2003, 01:25 AM   #18
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One more thing. With my (little) experience of bridged amps, I know that i have had to invert inputs on one of the two amps, having the first + and the second -? But in the briding adapter @ www.sound.westhost.com, the circuit doesn't show inverting one amp. Do I or don't I?

-Mike
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Old 27th September 2003, 01:33 AM   #19
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p2p, point to point. basically no PCB, just soldering the resistors and wires directly to the pins by using surgical ninja skills.

which circut. in the "simple" version, the botttom opamp is inverted.

from this circut, the input to both amps are both normal. the input to the first is +V, the second is -V.
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Old 27th September 2003, 01:39 AM   #20
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For the active adaptor (Proj 14) one of the op-amps gives the inversion by accepting the channels "ground" and sending it on to the one of the power amps. As you can see, the + out goes to power amp that driver the speaker + terminal and the - out goes to the power amp that drives the speaker - terminal. As always don't connect the - outputs of the power amps.

The simple adaptor (Proj 20) assumes you are breaking open a 2-channel amp (stereo, dual mono, etc.) and hot-wiring it so that it accepts a lone signal into the L channel. The L amp + terminal goes into the speaker + terminal and the R amp + terminal goes into the speaker - terminal.

If you think of the various modules as "black boxes" then the connects are the same as my original post about bridging. The fact is that bridging creates a "balanced" signal that is then fed to 2 power amps whose + outputs are connected to a speaker.

:)ensen.
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