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Old 4th June 2006, 06:48 AM   #1
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Default Total newbie questions...

Hello everybody! I discovered this website when searching for some information on the project I had in mind for quite some time now: Building my own pure Class A amplifier.

The problem with this is that actually, I'm quite illiterate in electronics. I mean, I know how to hold a soldering iron and I can tell a transistor from a diode , all the basic stuff so to speak, but I have no idea about the whereabouts of damping factors, harmonic distortions generating from the circuit itself and the different types of resistors used for an example, the different design philosophies of amplifiers, and other more complex aspects of electronic devices. Does anybody have some good recommendations for freely available material (pdfs for an example) that I could read through to understand more about things like that?

But back to my amp project. First of all, I would like to keep the money involved down to a minimum; I may have some good possibilities to get expensive/big parts like used power supplies and huge capacitors for free or very cheap, and I also have access to machining for building a good chassis.
The vague concept I have in mind at the moment would involve completely separated channels using two separate power supplies, a power output of around 20-50W, a very simple preamp section (no multiple inputs, resistor bridges for volume control) and in general the most minimalistic yet efficient material possible. Volume and weight of the whole thing (and for the major part visual appearance) don't matter to me a lot - in fact I could even incorporate car batteries into the amp for stabilizing the DC, if that would make a lot of sense.

My equipment is a bit limited as well: I would be using two soldering irons (both non-controlled, one 15W, the other 30W), a €20 digital multimeter. Unfortunately I don't have access to an oscilloscope.

So do you guys think it would be possible for a person like me, who has only superficial experience with electronics but a lot of time at my hands, to build anything worth the effort using this concept for under €100?

And then of course, as you can probably guess that I can't etch my own circuit boards, left alone design an own circuit, what existing amp model would you suggest me to build?

Hope I didn't ask too many questions that could have been answered by using the wiki or the forum search function - I just couldn't find those very basic "what you need and what you have to expect" answers in there.


So thanks in advance for your replies,

Chris
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Old 4th June 2006, 07:49 AM   #2
Netlist is offline Netlist  Belgium
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Chris,
Welcome here.
No need to tell that this forum is an excellent resource of knowledge.
Have a look at Nelson’s articles at www.passdiy.com as well.
As for the price tag, class A is never cheap (big transformers, capacitors and heat sinks) but I’ve seen many projects being build from recycled material.
20-50W? The AlephX comes to mind but I would advice a more simple amplifier as a first project. Something Zen as a starter will keep you away from frustrating debugs and is excellent learning material.

/Hugo
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Old 4th June 2006, 11:28 AM   #3
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Copy from my web page (under design).
Hope this will help.
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Old 4th June 2006, 11:31 AM   #4
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PCB? P2P is quite acceptable . . .
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Old 4th June 2006, 11:36 AM   #5
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Read

Passdiy articles and projects
Passlabs articles

Then, you could soon find yourself as a semi-pro . . .

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Old 4th June 2006, 12:43 PM   #6
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Hello Hugo,

thanks for your reply!

I'm right now looking through the passdiy site, and I think there's indeed a lot of valuable information on there (did only know the passlabs site yet).

I think I have to agree that 20-50W for a class A amp will be quite an overenthusiastic first DIY project - let's correct that down by the factor 10 - 2-5W, perhaps 10W will probably be adequate enough, as I only have a 16m² room to listen to the music actually.

Another correction appealed to me when almost sleeping last night - why should I go the route of using analog chinch inputs and resistors for varying the volume, when actually both devices I intend to use with this amp (Yamaha CDX 593 and an M-Audio Delta Audiophile 2496 soundcard) have digital outputs and incorporate ways to adjust their volume digitally - if I knew it wouldn't be completely over my head and far out of my intended budget region (could somebody please tell me that it isn't! ), I would just build the amp with a D/A converting pre-amp and no volume control at all.

Chris
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Old 4th June 2006, 03:50 PM   #7
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Hi Chris,

Have you considered a mini-aleph?

The Mini-A

It's small and cute and you can get PCBs from BrianGT:

http://chipamp.com/orders.shtml

This is essentially a smaller version of the Aleph3/30. As NetList
has mentioned, class A means big hardware (caps, transformers
and heatsinks). Since you seem to be covered in this
area, you're probably in better shape to build class A amps than
a lot of us.

As an FYI, I did not have an oscilloscope when I built my Aleph 30.

Good luck...and welcome to the forum.

Cheers,
Dennis
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Old 4th June 2006, 04:26 PM   #8
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Well, especially in terms of heatsinks/cooling I think I may have an advantage, since I'm more of a mechanical DIYer most of the time, so I have lots of scrap metal in my workshop, and the tools to give it the necessary surface area. Perhaps I might even go for liquid cooling using a few external pumps and car radiators or similarly capable equipment, since it's very much possible to get the heatsinks on the outside of the case, as opposed to computers; I could imagine such a configuration to be easily capable of disposing a few KWs of excess heat without a lot of hassle. Transformators probably won't be too much of a problem either; the biggest factor will be capacitors.

I don't know if it would make any sense to run car batteries across the power supply for cleaning the DC - has anybody taken such an option into regard yet? It would definitely take up a lot of space, yes, but it would also offer more capacity for the money than anything else I could think of - I just don't know if the batteries would be up to the job. Of course, for the amp itself I would use the same new and expensive capacitors from electronics shops as everybody else - I heard it wouldn't be a good idea to reuse amps from old equipment, can anybody confirm this (or actually, I'd prefer if somebody told me I could use them as much as I like without any problems for the quality of the amp)?

Well, however, I have to say thank you guys for those links, I will try to get as much information as possible before actually starting my project.

Chris
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Old 4th June 2006, 04:40 PM   #9
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Quote:
for the amp itself I would use the same new and expensive capacitors from electronics shops as everybody else
Most use NOS caps.
You can check if Wim still has some 33.000uF Rifa PEH169 left.
http://www.diyaudio.com/forums/showt...237#post655237
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Old 4th June 2006, 05:21 PM   #10
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Quote:
Originally posted by jh6you
Copy from my web page (under design).

where?
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