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Old 29th April 2008, 03:28 PM   #71
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Quote:
Originally posted by MJL21193
I can't speak for anything you have tried to do, but can only comment on. . .
My opinion: Headphone output from a TV, mp3 player or soundcard are not ideal sources for any amplifier. I wouldn't bother building anything if that's the only thing I had to drive it.

Line output from my soundcard drives my 21V/V gain chipamps just fine.
Thanks for the info. It is very helpful.
Since our results differ, the probable meaning is that the ouput capabilities of sources differ.

This has me thinking that I should do a standardized power amp project and propose a preamp as an add-on project.
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Old 29th April 2008, 03:34 PM   #72
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Quote:
Originally posted by danielwritesbac

, and used the 100k example because that roughly matches headphones.
??
Typical headphone impedance is quite a bit lower than 100k.

Quote:
Originally posted by danielwritesbac


Thanks for the info. It is very helpful.
Since our results differ, the probable meaning is that the ouput capabilities of sources differ.

This has me thinking that I should do a standardized power amp project and propose a preamp as an add-on project.

With each successive post you sink further.

I'm done here.
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Old 29th April 2008, 03:41 PM   #73
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1- They do not have the 4.7uf polyester capacitor in 50v version but only in 63v version. Does it matter? would the 63v work the same?

Yes, it will work fine. You can always go higher in voltage rating (if physical size isn't an issue) but not lower.

2- The schematics refer to carbon resistors, but there are three types: ceramic, compound and film.

Carbon film.

3- I cannot find 22k and 680R 1/4 W resistors. They only have 1W ones. Again, does the difference in Watts matter?

They have 1/4w metal films in those values.

4- Cannot find 10k .35W metal film resistors. Only 10k .33w metal film "fusible" ones. Is this OK?

Use 0.5w metal film.

5- Is 2R7 the same as 2.7R?

Yes.
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Old 29th April 2008, 03:43 PM   #74
Colin is offline Colin  United Kingdom
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>This has me thinking that I should do a standardized power amp project and propose a preamp as an add-on project.

Good idea. Keep it simple and add the preamp later if you feel it is required. You can use the pot plus gainclone as a standalone integrated for the time being.
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Old 29th April 2008, 04:45 PM   #75
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Default Re: Help Please!

Quote:
Originally posted by A Sanchez
I am going to build this version:
http://dogbreath.de/Chipamps/GainCar...nCardCopy.html
I am ordering the parts from Farnell and I am having difficulties locating the right ones due to unknown terminology and other aspects, for example:
1- They do not have the 4.7uf polyester capacitor in 50v version but only in 63v version. Does it matter? would the 63v work the same?
2- The schematics refer to carbon resistors, but there are three types: ceramic, compound and film.
3- I cannot find 22k and 680R 1/4 W resistors. They only have 1W ones. Again, does the difference in Watts matter?
4- Cannot find 10k .35W metal film resistors. Only 10k .33w metal film "fusible" ones. Is this OK?
5- Is 2R7 the same as 2.7R?
Many thanks for your help.
Regards
Antonio
1. That is a component specific WIMA brand 4.7uF 50v capacitor, and the design appears reliant on this choice (IMO).
2. Carbon film resistors are a tan/cream color, and they are the most common sort.
3. You can find a "variety pack" of 1/4w resistors at your local electronics hobby shop.
4. Use an ordinary metal film resistor.
5. Yes, and a speaker output zobel needs at least 1/2w if not a 1w resistor.

For reference, the amplifier design from the link above will play 1 decibel louder than lm3875. Given that there's no noticable difference in power output, there must have been something else that you find attractive about that (above link) project. Personally, I would inquire about component specific information, and if the amplifier from 2005 is still in use or if it was replaced/updated. Here's the email address associated with that link above: mick 'at' feuerbacher 'dot' net
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Old 29th April 2008, 04:54 PM   #76
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Default Correction.

Quote:
Originally posted by MJL21193
Typical headphone impedance is quite a bit lower than 100k.
Thank you for pointing out the error.
Insulting others isn't an appropriate response for a request of information.

Typical headphone impedance is, in fact, 120 ohms.
http://sound.westhost.com/project100.htm
And there's a link, in case someone wants a headphone jack.
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Old 29th April 2008, 04:57 PM   #77
Nuuk is offline Nuuk  United Kingdom
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Daniel.......

I built my first Gainclone some years ago and it sounded fantastic. May be I just got very lucky because because I didn't know anything about the likes of "component specific information", or any of the other wonderful issues that you come up with.

You see, the real beauty of the chip amp is the very low component count and the simplicity of the circuit. So it is quite possible to build a working GC, enjoy it, and then think about tuning a bit by substituting other parts and hearing the differences that they make.

I guess that you are trying to be helpful but if you read between the lines of the posters on this thread, they are complete novices and looking for ABC guidance, rather than being educated to degree level on the finer points of tuning a chip amp. As such you may be doing them a dis-service rather than moving them forward! But perhaps my signature says this all a bit more clearly!
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Old 29th April 2008, 05:00 PM   #78
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Default Re: Correction.

Quote:
Originally posted by danielwritesbac


Insulting others isn't an appropriate response for a request of information.

Typical headphone impedance is, in fact, 120 ohms.
http://sound.westhost.com/project100.htm
And there's a link, in case someone wants a headphone jack.


Hi Daniel,
You actually do insult to yourself when you steadfastly agrue with established fact.

Read more of Rod Elliot's site, he has lots of sound information to share. Short on mumbo-jumbo but long on fact.
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Old 29th April 2008, 05:12 PM   #79
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Default Re: Re: Correction.

Quote:
Originally posted by MJL21193
Hi Daniel,
You actually do insult to yourself when you steadfastly agrue with established fact.

Read more of Rod Elliot's site, he has lots of sound information to share. Short on mumbo-jumbo but long on fact.
I like to find the "high" and "low" parameters rather than assume, so this is most of the esoteric content that you'll find in other threads.

As for this thread, I have reported post#68 (my own post) to the moderator and asked for its removal on the grounds that its confusing. . .because I was really confused when I asked the question.

Rod Eliot's site is fascinating. Check out the corner frequencies topic on his subwoofer equalizer boost technology. Short on fact, but rattles the house nicely.

EDIT: got to get on topic. . . Rod Elliot also has some amplifier and preamplifier information, and most is a good read.
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Old 29th April 2008, 05:20 PM   #80
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Quote:
Originally posted by Nuuk
Daniel.......

I built my first Gainclone some years ago and it sounded fantastic. May be I just got very lucky because because I didn't know anything about the likes of "component specific information", or any of the other wonderful issues that you come up with.

You see, the real beauty of the chip amp is the very low component count and the simplicity of the circuit. So it is quite possible to build a working GC, enjoy it, and then think about tuning a bit by substituting other parts and hearing the differences that they make.

I guess that you are trying to be helpful but if you read between the lines of the posters on this thread, they are complete novices and looking for ABC guidance, rather than being educated to degree level on the finer points of tuning a chip amp. As such you may be doing them a dis-service rather than moving them forward! But perhaps my signature says this all a bit more clearly!
I'm actually requesting help in . . . avoiding. . . voicing the amplifier.

EDIT: We're doing the NFB next, its decision time, and I "hit the brakes"--time to ponder. . . and ask for help.

I think we got a solution. It was "Plan A" anyway.
That's a "factory standard" chip amp implemention with component values from LM3875.pdf.
and later. . .
a preamplifier (a more traditional item to "tinker" is the preamplifier).

Suggestions needed!
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