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-   -   A brand new start (http://www.diyaudio.com/forums/solid-state/1259-brand-new-start.html)

hugobross 25th November 2001 01:51 AM

Hi,

I've just decided to quit building (and improving) the amp with all those troubles (have a look at my previous thread). I just want to start with something more reliable, because I'm not very experienced in building amplifiers. Maybe I will start calculating my own design, but I'm still looking for a schematic to drive 350 Watt RMS, 8 ohm, speakers.
If you have examples of calculations of amps or if you know where to find some RELIABLE schematics, please let me know.


Best regards, HB ....

arnach 25th November 2001 03:13 AM

Hello
 

Hmm. I went back and read your the previous thread as to which you describe. It appears that you totally ignored the advice of several very generous people who tried to provide you with a simple solution. Instead, you chose to implement or in your lingo make an "improvement", using a poor quality op-amp, thus adding phase shift and distortion to the circuit and not solving the problem.

However, as you say, a brand new start. Check out http://www.aussieamplifiers.com, by Anthony Holton. He is a member of his site, and although I have not personally built one of these designs, there are plenty of people here who have.

-- Finley.

paulb 25th November 2001 03:02 PM

Quote:

Originally posted by hugobross

I just want to start with something more reliable, because I'm not very experienced in building amplifiers.

Substitute "simple" for the word "reliable". A 350W RMS amp is not a beginner's project. Just building the power supply section is a serious proposition.
You can't get much simpler than the Zen stuff. Or, something with a proven PCB available, like those at the ESP site (http://www.sound.au.com). Rod's 60W amp at that site is based on a design he has build dozens of over the years, and I built it without any difficulties whatsoever.
Building amps can be very frustrating, as you have found.

hugobross 25th November 2001 05:27 PM

just want to tell you this:
 
Well, you can say that I've ignored the solutions of several people. Otherwise, I've contacted several ingeneers (who are my teachers at high-school) and discussed those solutions with them. They said me that the problem could be solved by changing the values of C5 en C3; connecting resistors to the emittors of T1 and T2 would be an indirect solution (like my improvement was); but then they started to have a look to the general design of the amplifier and discovered several "unlogical" things like placing two diodes in parallel (D5 with D7; D6 with D8). I've learned that when you put two diodes in parallel just one will start conducting as first, so if you want do reduce the current in one diode this is not the right method (one diode will be destructed, the other one will folow). Please tell me if this isn't like that, and why are diodes paced over there?
So, I decided to take a brand new start to spare time and reduce costs. I have something in mind to build, but I'm not sure. I also want to add that I'm not very experienced in building amps, but there's no problem to me to build difficult schematics (I've done that plenty of times successfully), but I'm not that engaged to analyse wrong-designed schematics and correcting them; when I have to recalculate everything at myself, I can better start designing one at myself. But I dont know I will succeed in doing that, because it's hard to find clear (direct to the point) calculations. Otherwise it's nog big deal to download hundreds of nice amplifier schematics, but wich one does realy work and wich one don't? I think that's the biggest disappointment of the http://www.


Best regards and thank you for the replies,


HB.





P.Lacombe 25th November 2001 09:11 PM

Hugo,

"It appears that you totally ignored the advice of several very generous people who tried to provide you with a simple solution." (Anarch)

I don't understand why you're asking advices, and don't take them in account. This causes waste of time, for you, and for people who tried to help you.

Building of an 350 W power amplifier isn't simple thing, you must consider to have more patience, and more knowledge, to do this. Or else, prepare you to more disappointments.

Regards, P.Lacombe.


rtirion 25th November 2001 09:35 PM

A single 350W rms amp is no simple or easy task. I have to agree with all of the other people trying to help you.

But maybe this could start you in the right direction.
Start with a single channel simple but very stable 100W/8 Ohm or so design with a heavy supply.
Try to fully understand all there is to this amp. If you decide to modify, only do so if you fully grasp the implication of your modification.
Build a second channel the same way and a bridging adapter, or a BOSOZ (used as unbalanced to balanced coverter) to get these in a bridging configuration.
This will give you your 350W.
Build two of those configs for stereo.

Hope this helps a little.

Sawzall 26th November 2001 12:00 AM

Take a step back
 
Got to agree with them on taking it easy. Its not something I would jump into, and I have an office full of Electrical Engineers (four of whom work for me so I could tell them to fix it :) ), two different repair shops with all the equipment in the world, and money to **** off on it. 350watts is just a bridge too far for a clean sheet DIY's unless you really are a pro.

Secondly, just why are you building this? This much wattage is not likely to sound great for full range unless you spend megabucks - and even then, it is wastefull since so much of your gain will be eaten up in the crossover. If you are really looking for loud, think about active setups with multiple amps - it offers the best results. Take a look at the pro sound people. They are using multiple amps even in things like near field monitors. Then you can build simple amps for their tasks - good sounding lower wattage amps for mids and highs, and if you want, stupidly large simple amps for the lows. In the end, this is the approach that will get you what you want with a lot less heartache of burned up parts - it is a time tested approach.

arnach 26th November 2001 12:01 AM

how long did it take?
 

Just think, how long did it take John Curl before he made a 350w/ch amp? 30+ years?

-- Finley

Nelson Pass 26th November 2001 07:43 PM

John Curl could build a 350 watt amp 30+ years
ago. Assuming that he did not, I would say he
chose not to.

hugobross 27th November 2001 08:31 PM

Well, I'm sorry it came over to you as a waste of time, this was especially not my meaning of the thread.
But I also asked my teachers at school for advice, maybe their solution could be incorrect.

Well to thank all of you helping me, I will complete the design (it doesn't ask that plenty of time), I will test it (in a lab, and of course on parties), and I will publish the results in a new thread. And of course I will correct wrong theories of teacher if necessary.

The most important thing to everyone interested in DIY, is to learn of experiences, mistakes and the most important to learn from other people doing the same.

with the best regards and see you soon,

Hugobross... ;-)




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