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Chip Amps Amplifiers based on integrated circuits

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Old 31st December 2002, 10:17 PM   #101
Noam is offline Noam  Canada
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Just to add some fodder (hearsay really), my local 47 Lab dealer told me that Kimura goes through more than a hundred IC's to find a pair suitable for use in the Gaincard. Alluding that while the sum of the parts are not costly, there's a lot of labor involved.

Grains of salt and happy new year.

Noam
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Old 31st December 2002, 11:42 PM   #102
Philo is offline Philo  United States
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Brian,
The top view pic looks similar to a photo my friend was looking at when he built his gainclone. His photo showed the amp in place in the case but you couldn't see the front of it to tell if it was an actual 47. He said it was a photo of an early version but was now a much neater build.
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Old 31st December 2002, 11:55 PM   #103
BrianGT is offline BrianGT  United States
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Quote:
Originally posted by Noam
Just to add some fodder (hearsay really), my local 47 Lab dealer told me that Kimura goes through more than a hundred IC's to find a pair suitable for use in the Gaincard. Alluding that while the sum of the parts are not costly, there's a lot of labor involved.
Any clue to what would possibly go into selecting ICs? Do different chips vary much in terms of DC offset and such?

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Old 1st January 2003, 03:21 AM   #104
BrianGT is offline BrianGT  United States
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Well... I decided to start my gainclone tonight while waiting for the ball to drop. I am going to make it cheap for my first one. I picked up heatsinks for $1 each from a surplus store, Allen Bradley resistors (recommended by Thorsten) for $0.06 each at another surplus store, $2 solen cap, panasonic fc caps from digikey, $2 radioshack 100k stereo alps pot. I will use my aleph 5 transformer for this (25v secondaries). I calculated ~$17 in parts not including transformer or chassis for the 2 channels that I am making for my first gainclone. This should fit in the Fruglephile(tm) category.

I kept the feedback resistor path as short as possible.

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Old 1st January 2003, 03:29 AM   #105
BrianGT is offline BrianGT  United States
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zoomed out shot...

is it alright to tie the grounds together from the power supply caps, then go to the star ground? should the input and output ground go from my ground pin, or my star ground?

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Old 1st January 2003, 09:00 AM   #106
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Brian
Use the connection between the two caps as the star ground, but run the signal ground to the ground on the chip first, then link both to the star. This is the lowest noise solution for me, obviously your milage may vary
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Old 1st January 2003, 07:06 PM   #107
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Default 47 Labs a con job outfit?

Rod Elliot writes a cutting but probably true critique of 47 Labs and their bogus and flakey engineering claims. I am looking forward to completing my Gainclone but I have no illusions that it will be any better than my JVC reciever which also uses Ampchips of some sort. My Alpine car amps use Ampchips and they are reasonable sounding. Why not put those in the house?
Greg
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Old 1st January 2003, 07:51 PM   #108
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This thread is interesting. A bunch of people are getting excited about an IC amplifier when under normal circumstances, these things would not be given any respect whatsoever. Why? because Peter Daniel's does a really nice (and I mean REALLY NICE) job of packaging the things. Could it be that people are more impressed with packaging than content? Could that be the reason why so many "high-end" pieces of equipment appear to have far more $ in the metal work than in the circuits? Could it be that an amp is an amp is an amp?

It's one of those things that make me go "hmmmmmmm...".

MR
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Old 1st January 2003, 07:59 PM   #109
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I too follow this post with interest, but I think you give people here too little credit. If you read the entire thread, you'll see that most are interested because of sound quality, not packaging. Even though Peter D. did an impressive job on the packaging, I believe he did so out of sonic concern, not pure athestics.
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Old 1st January 2003, 08:26 PM   #110
joensd is offline joensd  Germany
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DC Offset
I used this circuit for my gainclone.
You can buy PCBs from an Elektor-like magazine.
If you disconnect the pot R1 youll get a real big DC offset.
A friend of mine fried his speakers like that.
I installed an additional resistor from the input to ground which resolved the problem.
Any comments? Is this circuit useable as it is?

To the last posts:
There are a lot IC amplifiers that are crap but chips like TDA7293/4 or the complete overture series from National Semiconductors are definitely an exception.
This thread is not not only interesting cause of Peter Daniels creations but that somebody actually let a "high-end" design compete with a gainclone and be honest about the result.
We want to hear about sonical differences and reasonable circuits for the DIYer.

Jens
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