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Chip Amps Amplifiers based on integrated circuits

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Old 29th April 2008, 09:18 PM   #91
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Quote:
Originally posted by danielwritesbac
(after we measure dc offset)
"If you're getting dc offset at your speaker terminals, reference the first page of LM3875.pdf and add the 22uF capacitor (position CI) as indicated in figure 1. "
How much offset are you willing to accept?
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Old 29th April 2008, 09:23 PM   #92
gychang is offline gychang  United States
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Quote:
Originally posted by Bluto
Gychang - Hi-

Where Ya been? I think Dan has about got this thing built in his head and just waiting for your approval.

You have alot of comments to give opinions to. This got crazy real quick.

Bluto
Bluto:

I am somewhat overwhelmed at the thread, everyone is very helpful, some information over my head. Certainly should try to help the newbies to try to build this thing, make it a pictorial lesson if possible.

You are giving me too much credit for I do not have enough know-how to grant a project or give any opinions on what others have suggested. This is great project for a newbie like me.

This forum is amazing...

gychang
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Old 29th April 2008, 09:32 PM   #93
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Quote:
Originally posted by gychang


Bluto:

I am somewhat overwhelmed at the thread, everyone is very helpful, some information over my head. Certainly should try to help the newbies to try to build this thing, make it a pictorial lesson if possible.

You are giving me too much credit for I do not have enough know-how to grant a project or give any opinions on what others have suggested. This is great project for a newbie like me.

This forum is amazing...

gychang
Well, we love your speakers!
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Old 29th April 2008, 10:33 PM   #94
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Thank you very much for your suggestions. It is time for me to start building the amp.

Northernsky
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Old 29th April 2008, 10:41 PM   #95
Nuuk is offline Nuuk  United Kingdom
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Quote:
Thank you very much for your suggestions. It is time for me to start building the amp.
Not at this time of night Northernsky!
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Old 29th April 2008, 11:25 PM   #96
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Quote:
Originally posted by Peter Daniel
How much offset are you willing to accept?
Given the resources of a 50w amplifier, I'd estimate the dc offset tolerance figure at 70mv. EDIT: That's a guess because my old meter can only read amperage at such low figures.

However, I think that you could provide a more accurate figure. What do you recommend as a tolerance?
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Old 30th April 2008, 02:44 AM   #97
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If we consider minimized circuit as in attachment, the DC offset will depend on input impedance and a chip itself. With 22k shunt resistor, the offset is usually below 80mV.

I measured at least 800 chips and offset variation (in that particular circuit) can be from 0mV to 120mV; the latter occuring for less than 2% of the chips.

If you have a potentiometer at the amp or use a preamp, the combined shunt resistance will be less than 22k and the offset goes further down, usually to less than 20mV.

So if you are certain that the source does not produce any DC offset (as it will be amplified by a factor of 30), you don't really need Ci.
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Old 30th April 2008, 08:27 AM   #98
Bluto is offline Bluto  United States
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WHHHOOOAAA Horse's!!!!!

1st time back since early yesterday AM.

I was gona start addressing all I felt qualified to one at a time then thought better to see where it had gone to but just had to stop and post before I finished.

John - your apology was appreciated but I don't know if even necessary. I figured you knew something or wouldn't have posted and I really wanted input. The reason for the thread is because as with all forums it's tough to get help for newbees on subjects others mastered moons ago. Newbees get ignored - just a fact. As I read down I see an Amp that I had saved to my personal picture Gallery long ago as a 'goal amp' for me. Didn't know til 3 minutes ago it was you. So, you obviously know your stuff. I see you and Dan know each other and you obviously have a degree of respect for him until he says something you disagree with and now your taking your toys and going home.

I guess this means that if I ever get to the point in my learning I really want to build the Amp you did I'm not going to get any help from you?

I just finished a long e-mail to Gychang and Dan not 15 minutes ago. I asked Gychang if it was O.K. with him to appoint Dan as Team Leader on this. Dan was the 1st guy with brains to step up to the plate and volunteer to help Gychang and I out. He's put alot of time into this. I appreciate all input but am especially thankful to Dan. He has virtually gone through the whole process at least in his mind.

I'm 58 years old. I'll never understand the Ego and thin skin on forums. If people don't want to help in a positive manner why don't they simply not get involved? Smarter than me regards electronics? So what? I'm not impressed. Want to discuss Soil MicroBiology for a few hours? Everyone is smarter than everyone in any given subject! Most of us know that by the time we're 15. If you want to compete join a contest!

Keep in mind this whole thread is based on a desire to build an Amp for beginners. We've already discussed in detail where those who started years ago are in the building process now at the beginning of the thread.

If you can live with that I'd like to see your continued contributions if Dan can live with you insulting him publically but if not we'll do fine without you .

Maybe I'll finish the rest of these posts and find you had 2nd thoughts regards what you said again.

You can call ME Dummy all day long .... not gona bother me a hoot.

Bluto
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Old 30th April 2008, 09:11 AM   #99
Bluto is offline Bluto  United States
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Hi Nuuk -

Regards post #77.

You're right but theres a method to his madness.

While guys like me and Gychang are near to totally lost when we listen to You, Peter, Dan and John speak Dan still has a handle on what we're after as do you . He can understand you guys and thats whats important .

From there he can make the thing simple enough for us newbees to build with limited instruction. I've agreed to write up and photograph whatever he comes up as I build it if Gychang likes the idea.

I appreciate the input of true Pro's on this as it will only help Dan design an excellent beginner Amp.

BTW - I like the way you've paraphrased the Proverb, it makes it's meaning clearer.

Thanks - Bluto
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Old 30th April 2008, 10:17 AM   #100
Colin is offline Colin  United Kingdom
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This thread seems to be wandering somewhat ... for a complete Gainclone kit, I can recommend Peter Daniel's Audiosector kits. You can even get a very high quality chassis and his thread here on the forum offers lots of advice. That's as close as you're going to get to a complete, fully finished kit.

Alternatively the Dantimax kit offers a board which has everything on it apart from the pot, input switch and transformer. This would make wiring the power supply and getting the gounding correct easier for beginners. This does leave you to source an enclosure but you could make do with a simple diecast metal box for the time being until it is up and running.

I went with Peter's kit, which is a thing of beauty. The only problem for UK builders is that the Plitron transformers Peter uses are prohibitively expensive to ship from Canada. However Airlink have been recommended on the forum and is the way I will go when (I'm ashamed to say) I get round to building Peter's kit.

There are, of course, lots of other options out there but as a sometime solderer who wanted to start off easy, these are the two that appealed to me. (Note for component tweekers - I bought two kits, one with standard and one with specialised components and will build the standard first in case I muck anything up.)

Hope this helps.
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