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Old 22nd June 2012, 10:01 PM   #11
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Quote:
Originally Posted by Antoinel View Post
I can already see your build. A printed circuit board [say 2 feet long by 6 inches wide per channel] with 2 rows of repeating low power amplifying units. Clearly, the BUFs will be on heatsinks along both of the long sides of the PCB. Their power outputs will then merge to the center of the PCB via small ohm high watt resistors [for isolation]. This build is feasible. Best regards.
Whoa now, that's way too much work.

No PCB's for this one. I will clamp them all together in a horizontal row with little pieces of aluminum plate between each one for heatsinks. The two rows will form the sides of the amp. All the pins will be folded over each other and soldered together. Local supply decoupling soldered directly on each IC.

The BUF634 can be paralleled pin for pin and doesn't need any external resistors to isolate the outputs. I believe they already have 10 Ohm output resistors internal to the IC; at least I remember reading that before.

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Originally Posted by franzm View Post
Yeah that's pro; this is the technically challenged version.
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Old 26th June 2012, 05:15 AM   #12
qusp is offline qusp  Australia
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the sweet spot is around 10, higher than this and your barrier to more useable power becomes the voltage swing in the VAS and buffer itself. you could parallel 8-10 for each amp, then bridge 2 of those amps for each channel

I guess you saw this project from opc? using the PCB for heatsink and higher performance obviously, but same idea. silly idea? haha this amp produced the best numbers within its power band (up to 15wpc) that ive ever seen.


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Old 26th June 2012, 05:35 AM   #13
osscar is offline osscar  Latvia
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Here you can see BUF amplifier:

Prophetmaster's Class "A" Power Amplifier с выходным каскадом на 41 шт. BUF634T

Russian text, but pictures can be seen.
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Last edited by osscar; 26th June 2012 at 05:39 AM.
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Old 26th June 2012, 11:50 AM   #14
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QUSP and OSSCAR: This build is awesome and ingenious.
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Old 26th June 2012, 11:52 AM   #15
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Quote:
Originally Posted by theAnonymous1 View Post
Whoa now, that's way too much work.

No PCB's for this one. I will clamp them all together in a horizontal row with little pieces of aluminum plate between each one for heatsinks. The two rows will form the sides of the amp. All the pins will be folded over each other and soldered together. Local supply decoupling soldered directly on each IC.

The BUF634 can be paralleled pin for pin and doesn't need any external resistors to isolate the outputs. I believe they already have 10 Ohm output resistors internal to the IC; at least I remember reading that before.

I am on your side. The simpler the build, the better and more reliable the outcome.

Yeah that's pro; this is the technically challenged version.
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Old 26th June 2012, 11:56 AM   #16
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theAnonymous1. I am on your side; a simpler build is much better [my earlier reply was inadvertently inserted in the quote = your text]
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Old 26th June 2012, 12:05 PM   #17
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I made a tweeter amp with these. It worked fine. Had a little more noise (hiss) than some others, but it was acceptable. Everything else was a great.
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Old 26th June 2012, 12:50 PM   #18
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Would love to admire your build [picture] if available. Food for my thought. Thanks.
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Old 26th June 2012, 01:13 PM   #19
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Quote:
Originally Posted by qusp View Post
the sweet spot is around 10, higher than this and your barrier to more useable power becomes the voltage swing in the VAS and buffer itself. you could parallel 8-10 for each amp, then bridge 2 of those amps for each channel.
Yeah, 40pcs per channel might be a little overkill, even for driving 4-Ohm loads bridged. It will give a little more Class-A working room without additional bias though and each device will be dissipating less heat.

Quote:
Originally Posted by osscar View Post
Here you can see BUF amplifier:

Prophetmaster's Class "A" Power Amplifier с выходным каскадом на 41 шт. BUF634T

Russian text, but pictures can be seen.
I see he used 41pcs per channel and only SE on +/15V rails. From what I can read I guess he used that many for the higher Class-A power output.

I don't understand a few things in his schematic though; like why the 330R on the input to each buffer and a 56K to ground. Is an output zobel really needed? He also uses 10R output resistors when the application note for parallel BUF634 says they are not needed....

Quote:
The output resistance of the
BUF634 is about 10Ω. Therefore, series output resistors for
decoupling the individual buffers are no longer necessary.
http://www.ti.com/lit/an/sboa065/sboa065.pdf

Last edited by theAnonymous1; 26th June 2012 at 01:15 PM.
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Old 26th June 2012, 02:02 PM   #20
osscar is offline osscar  Latvia
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hi,
author of this amplifier is a member of DIY Audio:

diyAudio - View Profile: Prophetmaster

maybe he will answer your questions - i have not studied this circuit and possible solutions or upgrades.

how I remember from past - it is a Class A amplifier.
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