Several Questions about the LM4780 GainClones - diyAudio
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Old 15th June 2004, 08:18 AM   #1
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Default Several Questions about the LM4780 GainClones

Pardon me, but I have written a whole epistle here (chapter, verse and numerous diversions) but here it is:

I have signed up to buy the basic LM4790 kit, but I have a few questions that have been addressed only in passing elsewhere.
  • Not counting the cost of the enclosure (which can vary all over the map depending on the esthetics), what is the range of costs for the entire amp project, including things that are not in the kit?

    Specifically, what is NOT in the kit?

    When is it likely that the order will happen?

    Is there some way that I'm being clueless?
A lot of mention has been made about the use of a regulated supply to give the amp better transient current capability. I am going to be using mine to drive GR-Research AV-1 speakers that go down to about 55 hz. I'm in a pretty small room, and these are surprisingly efficient for such small speakers. Eventually there will be a separate subwoofer, but I don't have the budget for that yet.
  • So will I need to add the regulator for adequate bass response in this situation?

    Or will the small filter caps be enough?

    Is there a schematic and or circuit board for a good regulator?

    Can it be added later without a lot of rebuilding?
I am a very good technical writer (I can also do pretty good illustrations and other graphics if needed) and if people want to post here some answers to this, I can organize them and make a good PDF or web page out of them.

I really like the discussion here, but I would like to see some of this expertise organized into a more comprehensible manner.

*********
BTW, I really like the GR-research speakers. I researched the hell out of everything before I made my choice and bought the drivers without hearing the system first. I don't have as much expertise with amp building as with speakers (I dabbled in the late 70's and early 80s, and was building Sub-sats way back then). I learned how to listen for good sound at the very least.

So I hope I've picked the right project for my budget with this gain clone.

I am currently using a rather beat-up Proton receiver I got for cheap on e-bay to drive these. It sounds slightly better than the even cheaper Kenwood it replaced. (The kenwood would thermally shut off after doing a really bass-heavy loud passage every now and then and the proton has slightly better bass). Both are pretty articulate in the mids and highs, especially given that I paid less than $70 for each of them including shipping. BTW, this is a really old Kenwood, before they started making that cheap stuff in the 80s. Don't laugh, it sounds pretty good.

Better name brands, like Marantz (and most certainly anything from NAD) got bid up thru the roof of my puny budget. I couldn't afford to pay for names.

The main thing I'm looking for on the gain clone is a bit more headroom and perhaps more sonic clarity as a result. So far, the GR-research speakers seem capable to do far more than what I'm giving them.

P.S. I'm sure the caps in my old amps could use replacing, but I don't know where to start on that either. Or whether it is just good money after bad. I can sell them as is for what I paid for them.
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Old 15th June 2004, 09:05 AM   #2
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A regulated supply should sound better. See Pedja's site for more details.

You sound as though you are quite new to all this though, so may I suggest building a non-regulated amp first. The regulator can be added later without a complete rebuild.

How much will it cost? I don't know what comes in the kit but other items that spring to mind are: case, sockets, selector switch, volume control, speaker terminals, mains cable, plug, grommet, fuses, power switch, transformer. You will have to price these up for yourself but a ballpark figure excluding the case would be about 50-60 USD using a cheapo volume control.

Are you being clueless? Only you can answer that one!

Quote:
I really like the discussion here, but I would like to see some of this expertise organized into a more comprehensible manner.
That's another way of saying that you cannot really be bothered to read through the posts to get the inormation that you want! I have spent 15 minutes posting this information which is all on this forum for the reading!

from the Nepalese Mantra:

Judge your success by what you had to give up in order to get it.
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Old 15th June 2004, 09:23 AM   #3
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i agree.
I spend hours reading the countless posts in the lm3876 thread, often being distracted by PCB design-vias or not, special caps or not,when all i really wanted to know,is how much power id get if i bridged the 2 parallel chips...it took an afternoon to find



a simple FAQ with the 1st ten questions people ask,would save 90% of the asking!

perhaps add it to the wiki page?
Cheers!
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Old 15th June 2004, 09:40 AM   #4
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There is nothing stopping anybody trawling through the posts and condensing the information into smaller 'packages' that could then be put on some web space.

That's what I did originally with the FAQ page on Decibel Dungeon.

There are several other very good chip amp sites around for the searching but it does seem that some people are relying on others to do all their research for them!

When you post on this forum, you are requested to tick a box confirming that you have searched the forum for an answer to your question before you post!

Now I don't mind helping anybody but I am finding myself answering the same questions over and over again. Yes, I know that I don't have to but out of courtesy, I do.

And I get more than a few emails through Decibel Dungeon asking questions that are answered on the site. So not only do some people expect others to spend a large part of their time creating web sites, they then can't even be bothered to use the search facility to find the answer that they want.

It's a great pity that the Internet is seen as a free source of information. I totally agree that information should not have to be paid for but many see this as an excuse to take advantage of the situation by taking all the time and putting nothing back.

I have 'taken' lots and recieved lots of help via the Internet but I hope that I have also put a little bit back. And before I ask others for answers, I have a good look for myself first.

I'll step of this soapbox now but I think what I have said is well worth the time it took to type!
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Old 15th June 2004, 10:50 AM   #5
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Aaaaaaaaaamen!

Some of us really work hard to make something new, try this and that, listen, try again, report the results, schematics, everything people can find here.

But then, I receive personal mails to send the schematic of my pre.
And when I repply with the link and the post where I comment the values of the components, I receive this: "yeah, just thought it would be easyer to ask you".
A guy even told me he was going to build my pre, and then this beauty: "Carlos, can I connect the pre to my speakers?" , I told him: "this is a line pre, you need an amp too." Question: "what's a line pre?".
Wazzat?
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Old 15th June 2004, 12:48 PM   #6
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This is something of a 'chicken and egg' situation.

When people keep asking the same questions, the number of threads grows and questions get answered, often in part, in the various threads on the same subject.

Then people come here and say that they can't find what they are looking for, ask the same questions again, and the information that they (and others) seek gets buried deeper in the heap of threads.

That's the reason for the 'have you searched' check box when we post but I guess it is easier to just click in it and post anyway.

But if you can't find anything here, you should try the health forum that I go to. 95% of the posters are female and every thread descends into a long chain of irrelevence. Nobody seems to mind though and yes, the same questions get answered time and time again.
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Old 15th June 2004, 03:11 PM   #7
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I wasn't expecting you to jump all over me like this. I HAVE been reading and searching the pages for days on end, several hours a day.

I have not found the answers to any of the questions I made here. Most of the discussion is mentioning things in passing that I don't yet understand.

What I was hoping for, was some advice to fill in what I had not yet discovered. I do intend to make it worth your time by posting a how-to that I will keep regularly updated.

Even if I am clueless, there are several questions here that haven't been answered.

I am not one of these people that don't understand basic physics or electronics. I have a degree in Mechanical Engineering; but I don't have enough electronic engineering expertise to make sense of so much of the stuff mentioned in passing here.

I was just asking for a little help. I do appreciate the answer to one of the most important questions -- the cost of the parts.
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Old 15th June 2004, 03:56 PM   #8
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Sorry Geewizbang, my rant is a general one and not aimed at you personally.

I hope that I did answer your questions first. What questions did you feel still need an answer?
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Old 15th June 2004, 04:13 PM   #9
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Quote:
Originally posted by geewhizbang
I was just asking for a little help. I do appreciate the answer to one of the most important questions -- the cost of the parts.
Why not ask int that thread?
I think there's a thread for this, plenty of people there...

geewhizbang, my post was not directed to you in personal, sorry if I didn't make it clear.
Note: I could only write your name with copy-paste.
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Old 15th June 2004, 06:01 PM   #10
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So that it wouldn't get buried in the middle of whatever else you were discussing at the moment in that thread?

*****
First, I should assure you that I understand that the open-ended discussion is very, very valuable.

There just needs to be someone involved with collecting the information into a more accessible form to help the less-experienced get their feet wet.

A newbie like me may be better at doing this than an experienced hacker, because I have the questions right now.

*****

I want to collect all of the newbie stuff in one place, so that people like me can get more questions answered efficiently.

(at least the reasonably intelligent ones --- we don't have a prayer of helping someone that doesn't want to understand basic physics).

****

BTW, I have a few more.

1. For all of the discussion about inverting / non-inverting, nobody explains what that is. They just assume that you know. I gather it has something to do with how the amp is connected to the ground plane. I know that this is basic, but I would like to know.

2. What is a zoebel? They are discussed all over the place, but I haven't found a definition.

3. Is a metal box recommended, or is just having grounded metal shielding between the high voltage AC stuff and the low voltage amplifier circuits good enough?

And an observation: Some of us are less interested in tweaking at first. Some of was want a known-to-work solid design. Then we can do our tweaking from there. Or not. I might just be happy and leave good-enough alone.

So many of you have so much tweaking experience, that even as you describe a design, you make it very unclear what the final design was. Lacking a place to start, it is hard to put your tweaks into perspective.

For example, my first speaker project was a plop-in-the box speakerlab kit. I built the box myself. For my skills at the moment, that was a great choice. I later moved on to buying raw drivers, building my own crossovers, etc.

I think that this gain clone can be a good first project, but given my very limited budget, Ijust need to have fewer open questions before I commit my time and funds to it.
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