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Old 1st February 2004, 09:43 PM   #1
cm961 is offline cm961  Canada
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Default New 4 channel GC finished

Hi guys,

I finally finished my gainclone. It took me a lot longer than I wanted considering I started with a case and a power supply already setup and ready to go. The details can be found here. Basically the project worked out ok considering it cost me about $4, excluding parts which I already owned.

I have a severe distortion problem though, but I really don't think its the power amp. I believe I blew my tweeters.

There is a large turn on thump, I know this is a common problem but I thought it would be better with these chips, and I believe that's what killed my tweeters, if they're dead. I'm about to do some tests. Is there a circuit, which does not require relays that will help with, if not eliminate, the turn on/off thump?

Thanks,
Pete
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Old 2nd February 2004, 08:12 AM   #2
Nuuk is offline Nuuk  United Kingdom
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Hi Peter,

As I have to work on a limited budget, I have to be careful about what I buy too. But I have found that it can be false economy to skimp on parts.

Reading your link, for instance, you could have saved blowing those regs by using two stages of regulation so that the voltage drop wasn't so big. Yes, extra parts but the cost would have been offset by not having to replace the blown regs! Just a thought!
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Old 2nd February 2004, 02:47 PM   #3
cm961 is offline cm961  Canada
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Hmm you make a good point. How would you make two stages though? You mean say one 7812 inputs the 35V and outputs into the others input, or would it be a different type of regulator. Because I have tons of regulators. Or pehaps I could have used a 7824, which probably has a higher input voltage, and then down to a 12. That would probably increase reliability as well (even though its extra parts) because the regulators wouldn't be running as close to their maximums. I have them heatsinked at least (just bolted to the floor of the aluminum case).

Also I investigated my distortion problem and it turned out as follows. I synthsized a A note (220Hz) to tune my guitars to. A few weeks ago I converted it from .wav to .mp3 and the signal was totally clipped after encoding. I mean badly clipped, like at about 2/3rd of its maximum it just totally leveled off. Well I'd say its time for a new encoder, since it was encoded at 192kbps with the xing encoder which comes with Audiograbber. I knew mp3s were generally bad, but I didn't know they were that bad!

Pete
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Old 2nd February 2004, 03:37 PM   #4
Nuuk is offline Nuuk  United Kingdom
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Quote:
Or pehaps I could have used a 7824, which probably has a higher input voltage, and then down to a 12.
Yes, that's the sort of thing. I prefer to use 337/317's but basically each set of regs is dropping less voltage and not being pushed so near their limits.

Of course the first stage of regulation must be suitably rated to be able to acept the input voltage.

Here's an example from Decibel Dungeon .
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