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Old 29th January 2014, 04:45 PM   #311
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Meh, been reading Philips data sheets and they recommend 16x the normal listening level for head room. If I could afford capacitors like that...

I've had an epiphany though on protection of our precious stereo amp and speakers. Just use an 800V florescent light ballast wired to an aluminum volume knob that kicks in whenever some knucklehead turns the volume past 8. You could also set it so it is triggered to be on after you set the volume where it should be or just to a dummy volume knob that had no other function other then to persuade people not to touch your stereo w/o asking.

Idea of defeating knuckleheads isn't original to me of course. I was reading a Crown amp manual and they make them such that you can pull the volume control knobs off and replace them with a hard rubber plug.
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Old 30th January 2014, 07:56 AM   #312
AndrewT is offline AndrewT  Scotland
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Quote:
reading Philips data sheets and they recommend 16x the normal listening level for head room
16 times what?
Voltage? or Power?, or Loudness?

It is normal for us to listen to average music levels that are one tenth of the maximum power available from the amplifiers.
Many will listen at one hundredth of maximum and during quieter periods we can be listening at one thousandth of maximum power.
These are equivalent to -10dB, -20dB and -30dB relative to maximum power.

This normal listening does not require any listener to change capacitors.
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Old 31st January 2014, 05:05 AM   #313
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I took it to mean power output i.e. if you like to listen to music at say 5 Watts/channel, you should have an amplifier capable of delivering 80 Watts.

Seemed to be unique view of the problem. I literally can't stand it when distortion gets to steady state ~3%. I don't care about volume that much, sum of everything that can go wrong from an over taxed amp at 3 Watts or old cassette player. They seemed to be targeting that one note or drum beat that will spoil the whole experience for them.

I don't think I will change but I can see their point. Mona Lisa with a mustache would kind of kill the rest of the painting.

I trend towards power supplies that are just good'nuff. Transformer output geared at minimum requirements and capacitors just enough to make the hum go away. I don't worry about distortion on a single rim shot >3% in a few hours of listening.
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Old 31st January 2014, 08:25 AM   #314
AndrewT is offline AndrewT  Scotland
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Listening to 5W/channel will be described by some or many as too loud. Especially if they only had an 80W/channel amplifier for that 5W listening session. That leaves just 12dB for transients over the average level.

I generally listen at less than 1W and use amplifiers of ~60W to 170W
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Old 1st February 2014, 05:21 PM   #315
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Quote:
Originally Posted by AndrewT View Post
I generally listen at less than 1W and use amplifiers of ~60W to 170W
Same as me, always had amplifiers with around 200W RMS per channel, most of the time played at below or around 1W.
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Old 11th February 2014, 10:06 PM   #316
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Is it suitable for a subwoofer amplifier?
I plan on building the version with the TDA7293 as a subwoofer amp, the subwoofer is 2ohm ~1200W RMS, how many output pairs per amp would you recommend for that kind of power (or ~1000W RMS is more than enough)? Something along the lines of 3-4 pairs per amp?

Thanks in advance.
T.C.
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Old 12th February 2014, 08:14 PM   #317
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Hi guys, do you think it would be possible to mod these boards to use 5200/1943 outputs?

TDA7294 BTL 85W Mono Channel Amplifier Circuit Board - Blue (AC 15~35V) - Free Shipping - DealExtreme

Cheers!
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Old 17th February 2014, 01:57 PM   #318
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I made this amp, and like I said before it's amazing. Low cost, few components and it kicks.
My first one blew up when power went down because of lightning storm( I think, it just didn't work after that day), so I made new one. I made everything the same like last time, but this one has a problem. It's like sync resistor doesn't sync good. There are popping sounds and short term dc signals or something (speaker moves out like it plays really low and high volume bass) and generally speaker doesn't play what it should. Everything is wired properly, and values are the same? Any ideas what's wrong?
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Old 17th February 2014, 06:06 PM   #319
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IceTorch you may have to address the sync resistor, your TDA or 5200/1943 might have different ratings, you know there are fake chips out there, and there are also some variation in the gain on transistors.
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Old 18th February 2014, 09:43 AM   #320
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Sorry, I don't understand what address the sync resistor means. I'll have to change it's value?

TDA is
STMicroelectronics
TDA 7294
CZ029246
Vb CZ MAR

transistors are Toshiba

Is there a way to tell if it's fake?
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