Commercial complete Gainclone kit for a beginner?

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It works!

Thank you all for your help.

The amp works just fine but I will take all your suggestions into account in the fine tuning process.

It didn't exploit :eek: and has no hum at all :cool:

I am using a portable radio as source and very cheap speakers but the sound is clean and very promising.

I will report later in the weekend after I try it with proper sources and speakers.

Question: Can I try it with an active preamp without removing the pot? By the way I am using a 100k pot that I took from an old amp. Is 100K too high?


Regards

Antonio
 
Peter Daniel said:
Without source connected, it's a normal reading.

RE: 85mv dc offset into speakers.

I didn't mean to contradict on whether that's suitable for speakers. Its just that my personal preference is "lower than 70mv."

Also, I've noticed that amplifier chips may vary per individual sample. For instance, I've got a pair of matched LM3886's. One does 20mv DC offset and the other does more than 200mv (not acceptable).

Swapping the 22k input impedance resistor for 15k instead,. . . and then both chips were "less than 70mv" on DC offset.


There's a "trick" for DC offset:
(AC coupled, aka fully decoupled)
You can use the optional "Ci" cap at the NFB to prevent amplification of DC.
Reference LM3875.pdf to see the location of Ci.
That forces zero DC offset.
This looks wonderfully easy on the schematic.
However, it may also force a lot of shopping to find a Ci cap for seemly sound. . . eventually costing a tidy sum and a lot of time-consuming frustration. That is why, both Peter and I, wish to avoid Ci. Limricks!! Oh no. ;)

Instead, I'd like to propose this circuit for very low DC offset:
(Shown is LM3886TF)
 

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I've seen noise with 100k pots,
weird muffled sound with 50k pots at some (not all) locations on the dial,
missing bass with 10k pots. . .
and never any trouble from 20k pots.


However, it may also force a lot of shopping to find a Ci cap for seemly sound. . . eventually costing a tidy sum and a lot of time-consuming frustration.


I am SO very happy that I'm not a rank newbie doing my first chip amp research at this point in time. Statements like those above would lead me to believe that the endeavor is a mine-field of potential problems with a razor thin chance of success, when the reality is that nothing could be further from the truth.
7-10 components per channel IS NOT overly complicated for anyone able to find this webpage and parts selection is NOT that critical.
Ever look at pics of the original GainCard board? Ever read a review ?
Try this link


Sincerely,
7/10
 
seventenths said:
I am SO very happy that I'm not a rank newbie doing my first chip amp research at this point in time. Statements like those above would lead me to believe that the endeavor is a mine-field of potential problems with a razor thin chance of success, when the reality is that nothing could be further from the truth.
7-10 components per channel IS NOT overly complicated for anyone able to find this webpage and parts selection is NOT that critical.
Ever look at pics of the original GainCard board? Ever read a review ?
Try this link

Sincerely,
7/10

Did you notice during the misquote spree, that a simple solution was given for each? Why was that omitted from the quote? Malice?
 
Malice? Absolutely not man! I just think that the whole thread has a TON of potential for confusing the ever-living snot out of anyone considering a chip-amp as their first build. Period.
First build? A simple amp with whatever parts are readily available will work quite well and provide a great platform for further experimentation/learning.

I find your enthusiasm more than admirable, but the endless stream of BS is beyond annoying. How many poor souls have gone on a capacitor shopping spree as a result of the "screaming woman" analogy? Hopefully none, but I doubt it.


sincerely,
7/10
 
seventenths said:
Malice? Absolutely not man! I just think that the whole thread has a TON of potential for confusing the ever-living snot out of anyone considering a chip-amp as their first build. Period.
First build? A simple amp with whatever parts are readily available will work quite well and provide a great platform for further experimentation/learning.

I find your enthusiasm more than admirable, but the endless stream of BS is beyond annoying. How many poor souls have gone on a capacitor shopping spree as a result of the "screaming woman" analogy? Hopefully none, but I doubt it.

sincerely,
7/10

Notice the padding resistor on the input filter capacitor. That standardized method solves problems from sources attempting to drive capacitive loads, and using standardized methods helps to prevent problems.

Since the point is avoiding problems, a 20k pot is recommended, for general compatibility. Once again, that helps avoid needless shopping. Is it perhaps offensive that a $1 component can do hifi quite well?

You're absolutely right about this thread having gotten out of hand. I'll post the completed beginner's project on a new thread.
 
Daniel,
I guess my deeper point is; If the original 7 component builds were any more complicated, I for one, may not have ventured into a hobby that I have enjoyed immensely. Many have taken the same steps, yet many are still on the brink, the small creek before them appearing as daunting as the mighty Mississippi and at times, you seem to be the tour guide touting the ever-present dangers and merciless pitfalls before them. I know, however, that you are trying to help.

On occasion, I still listen to my first Lm3875 Chip-amp. Every component but the trafos and chips were straight out of the local Radio-Shack and even with an (gasp) electrolytic Ci, I still find the amp provides a great deal of listening pleasure. I don't run with any "audiophiles" but my friends and family agree.
Yeah, I may be skewed toward elegant simplicity... it's easier here for the common man.


7/10
 
seventenths said:
Daniel,
I guess my deeper point is; If the original 7 component builds were any more complicated, I for one, may not have ventured into a hobby that I have enjoyed immensely. Many have taken the same steps, yet many are still on the brink, the small creek before them appearing as daunting as the mighty Mississippi and at times, you seem to be the tour guide touting the ever-present dangers and merciless pitfalls before them. I know, however, that you are trying to help.

On occasion, I still listen to my first Lm3875 Chip-amp. Every component but the trafos and chips were straight out of the local Radio-Shack and even with an (gasp) electrolytic Ci, I still find the amp provides a great deal of listening pleasure. I don't run with any "audiophiles" but my friends and family agree.
Yeah, I may be skewed toward elegant simplicity... it's easier here for the common man.

7/10

Agreed! Elegant simplicity is coming up soon. I'm waiting on the post office. Got to make some samples, because the photos really help.
 
7/10ths -

I think the 'masses' missed the point.

Since this started I've had opportunity to see dozens of threads where someone posted a schematic of a new GC they'd designed and asked for opinions. One by one the 'Gurus' tore it apart or gave their blessing. Poster made appropriate changes , built GC and thread was over.

All Dan did here in my mind was to listen to a need from a couple of newbees and attempt to do same as others but wrote his thought process 'out loud' so those with knowledge had opportunity to dissect it a stage at a time to see it's flaws, if any. Boring to death for a newbee who doesn't understand it but invaluble as a point of critique as well as in stating reasoning when he develops a build manual of much condensed version. He's basically given everyone who wanted to an opportunity to shoot down his design publically and also as graciously made changes when someone more knowledgeable then himself made any error he had made clear.

Upon completion it's a total record of how and why his design came to be. No one 'who knows better' will have opportunity to say they were not invited to critique an ongoing process. It takes some guts to stand up to the barrage that's come in.

I see the point in all you're saying. I think when Dan is done and he organizes all of this others will also see it went exactly where the original poster requested it to go.

I'd be willing to bet once Peters thread gets started dumb newbee questions won't appear as dumb as others might suppose them and many will see why some of us did not take on a kit or a scratch build based upon info we could see on the Web or in instruction manuals. See my next post.

BTW - You made comment regards posting more photos of your latest build once batteries were back up on your camera. I'd like to see the backside as well. Nice build.

Thanks - Bluto
 
Bluto,
Thanks. You'll have a ball once you get your feet wet. Enjoy.
Oh and as to the pics, well I was in San Francisco last week on business and some lost soul decided that he needed not one, but both of my camera's more than I did. He also apparently needed my sonicare, my binoculars, both of my electric razors and an armload of other belongings. I'm now completely disheveled, unshaven with horrible breath and no means of documenting the situation.
Maybe I can dig up my daughter's cam?


peace,
7/10
 
Thank You Greg !

Greg & 7/10ths -

I had made the point way back in this 'thesis' that I had found Web info and Manuals online I'd read not complete enough for me as a newbee to follow for 1st time build.

Greg posted link to 'Schoolies Amp' which I'd never seen. When looking at link it gave limited info but I immediately noted how much easier it was to follow than all else I'd seen and posted that observation. Can't recall post #'s, about page 6 of all of this.

Greg was gracious enough to send me copies of Schoolie Amp build as well as Assembly Manuals and Guides from both Altronics and Dick Smith Electronics.

Greg - Thank you so much. You provided no return address, please PM such to me so I can at least get postage to you.

You Guys should see this stuff. This is actually real close to 'absolute dummy' doable 'as is'. There are diagrams of parts explaining what they are. There are explanations of what electrical symbols mean. There are color codes. There are Glossary's with definitions. It goes on and on....!! It doesn't stop at 'Dummy'. For the 'learned' the explanations become as deep as needed.

I have something to say.

While watching the Tube last night I came to find out that American kids don't have Shop Class anymore. What??!! No Woodworking, Electricity, Metal?? For Me this goes back nearly a half a Century. Do you realize how antiquated that makes my skill levels beyond what I've sought to learn on my own? If such is the case is it any surprise that at my age what I read that passes as knowledge and Instruction is difficult to follow? If from American sources it's coming from people who had no education in these fields at all beyond that which they received at Schools of Higher Learning! I hate to admit it but as an American this reality makes me pretty sad. This literature from Australia ought to shame American Educators. I'm 58 and I understand this! Yet when I read explanations from Audio Gurus on American sites there exists a snobbery and an assumption that those participating had a Degree in Electronic Engineering prior to an interest in Audio. Now that I realize that our School System has sunk to the point that not only are we only graduating 60% from High School but we're also teaching them nothing while they are there I don't feel so bad realizing the participants at Forums never learned any basics themselves until their 2nd semester at College. As they were required to get past such in weeks it's no wonder they can't teach it to others.

Thanks again Greg - more of a lesson here than what I stated. Knowledge of this nature and DIY is a cement that holds Families and Societies together. Education is for doing, not knowing.

Bluto
 
Bluto,

We don't do education here -- we do schooling -- two very different things. I think I can relate to where you're coming from. I'm a little younger than you, but roughly of that era and we started our first woodworkig classes in 1st grade and and at least until I got sentenced to Catholic high school, there was always some kind of shop-related class every semester of every year. My dad was an ME but had a very keen interest in elctronics, so I was also learning to solder when I had my first woodworking classes, but I lost my sight at 31, so am now coming at this whole thing from a totally different perspective, and while I know the basic concepts of how thing work, how to soler, etc., I'm trying to come up with a good way to translate these kinds of projects and their associated schematics and diaggrams into a useable format for me.

I know it isn't exactly your situation, but there are really quite a lot of things in common in terms of how to communicate information in very clear and concise ways, and one of the best ways to do that is to give people with different learning styles a variety of means to access the information. Words for some, pictures for others, and although not really possible in a virtual invironment, guided hands-on work -- just like those shop classes used to be.

If you want to look at an example of a guy who has started to do this, check out funwithtubes.com and see that many of his circuits have links to verbal descriptions of the circuits. I don't agree with a lot that the author of that page has to say aout tube desighn and audio in general, but that's not the point, and I do give him credit for making a very good start.

-- Jim
 
Help!

Oh, I'm so excited! A very huge box of parts arrived today! Finally, I got authentic LM3875's. They've been out of stock for so long.

Of course they sent me the discontinued LM3875T models--its like Murphey's Law or something. Since those aren't insulated. . .

Does anyone know of a good spot to buy micas, here in the U.S.? I'd sure like to know of a source for perfectly-flat, non-rubberized, insulators.

Thanks for your help!
 
Hi Jim -

Your post is inspiring.

Sometimes it's easy to fall into a 'pity' trip when you have health issues. Then you see or hear from a guy in your situation and realize what a sound kick in the tail you have coming.

Sight, hearing , breathing and mobility. The list doesn't get much more basic than that.

I wish you well in your endeavor, you've come a long way if you succeed here and even further if you can figure a way to teach the methods that help you to others in your situation.

I'll check out info you provide .

Thanks - Bluto
 
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