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Old 12th January 2004, 12:54 PM   #21
Nuuk is offline Nuuk  United Kingdom
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Quote:
What bugs me is that the Revox is a 5 channel AV amp, with 5xTDA7294 and only a 300VA toroid.
G'day my friend from Lisboa! It would worry me too slightly given the price of the amp but I am currently listening to my OPA627 buffered IGC with just 80VA per channel and I cannot fault the sound. I think a bit more VA is better but not essential.
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Old 12th January 2004, 01:09 PM   #22
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Hi Nuuk!
Well, I suppose it will depend on the transformer voltage.
If using a 2x18V trafo, the amp will give less output power and will demand less current from the PSU.
If you use a 2x22 or 2x24V trafo, you may get into trouble with low VA ratings.
The bass will suffer, and the amp may play well only with ultra-sensitive speakers.

I have a very small amp (my portable amp ), with two OPA548s, and a 2x12V, 2A trafo.
It plays surprizingly well, but I think it's because of the low voltage.
With around +/- 15V PSU the amp must be delivering some 10 watts RMS...
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Old 12th January 2004, 01:53 PM   #23
GregGC is offline GregGC  Canada
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Default Re: humm

Quote:
Originally posted by uvodee
I made a stereo set, first try = great, had to sell it because my first guest wanted to take it home.

second set I had problems , turned out to be a problem with the ground! (thanks for the awesome assistance Gregc.

I just finished my third set again using the LM3875's some different brand of components in caps and resistors, but my ears don't want to go along I think, it seems no different in sound to me. One problem is that i cannot connect them to my 70's Epicure speakers = too sensitive, I can only regulate the volume within 1/4 of the track, and then the sound becomes tooooo loud. When using other speakers like Pioneer of Audax there is no problem

I have components for 3 more and then I am going to start new speakers with the Jordan X92S

Right now I am using transformers from Apex, one (200 VA) for both chips and hear no irregularities.
I must say that I was quite impressed the first time using them, There were noises from the recording coming out of the speakers that I had never heard before, expecially when listeing to live classical recordings.

Jean-Pierre

After that I am starting with the Lm3886 .....

J-P,

Thanks for the good words, first.
You can use a devider at the front of the GC to decrease the sensitivity. If you want you can use a switch to turn the devider on or off depending on the type of speackers you use.
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Old 12th January 2004, 02:01 PM   #24
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Quote:
Originally posted by Luke


Hi Peter,

is that the one on the LM3875 datsheet, top of the page, fig 1.
Is that really your preferrred clone?

cheers ab
It's basically like that, with most components removed, except for 3 resistors and 2 caps
http://www.diyaudio.com/forums/showt...546#post265546

PS: Doesn't matter that cheap is different in the drawing.
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Old 12th January 2004, 08:08 PM   #25
Luke is offline Luke  New Zealand
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Thanks Peter, I might try it on my lm4780 I plan to build
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Old 18th January 2004, 06:43 PM   #26
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This shematic is good or not ???

I need to put a 0.22 ohm resistor at the output ????
I need to put a 1 uf cap between +V and -V ???
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Old 18th January 2004, 07:11 PM   #27
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The above schematic is good, but I wouldn't recommend it anymore. My current version looks like this. Note that polarity of the speakers is not mistaken. For some reason the sound is better out of phase Also, 244 Vishay is optional. I chose this value as it can be bought cheap ($3) from a forum member.
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Old 18th January 2004, 08:33 PM   #28
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Yes but...... this schematic is so different that the other !!

Do you have the complete schematic for this amp ?? Because I don't see the value of the pot on your draw.
And what is 244 Vishay ?????

What is the value of the cap at the input ???


If you have the entire schematic, I will understand more how to do the circuit....

Thank you Peter Daniel
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Old 18th January 2004, 08:36 PM   #29
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Peter, reproduction with out of phase connected speaker is unnatural. I was trying it with several amps and in every time I was get it back. This amp can't be exception .
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Old 18th January 2004, 08:57 PM   #30
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P. S. : Which Caddock - they have in program many types. P. P. S. : Reklam - " Partners for three dollars chip are only three dollars resistors - your enjoy will be triple " .
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