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Old 10th November 2009, 11:08 AM   #31
Did it Himself
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Why do you say the circuit is unsuitable for bridge?
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Old 10th November 2009, 11:42 AM   #32
poynton is offline poynton  United Kingdom
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Location: A life on the ocean waves when I'm not at home in N. Wales (but I'm not Welsh so no sheep jokes!)
If you want a simple amp suipable for bridging try :-

TDA2050 pdf, TDA2050 description, TDA2050 datasheets, TDA2050 view ::: ALLDATASHEET :::

or get a kit :-

Audio Power Amplifier 20W 2x TDA2003 - Assembling kit on eBay (end time 24-Nov-09 12:34:38 GMT)



Andy
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Old 10th November 2009, 11:53 AM   #33
Mooly is online now Mooly  United Kingdom
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Quote:
Originally Posted by richie00boy View Post
Why do you say the circuit is unsuitable for bridge?
I was thinking mainly of having to AC couple, and then there is the added complexity of a phase splitter to drive them, and the fact that the sonics won't be as good etc .... and how much "subjective" increase in volume will you get from all that. The power supply won't be rated for the increased output too.

Bridge use is fine for specific applications, say the limited supply available with a 12v battery etc... my opinion anyway

Keep it as it is I say.
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Old 10th November 2009, 12:10 PM   #34
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OK so actually the amp itself is fine to bridge, just achieving a bridge amp is not recommended by yourself.
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Old 10th November 2009, 12:21 PM   #35
Pigy is offline Pigy  Serbia
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Dear poynton, because I like to make stronger amplifier with bridge mode.
I know that can find on internet many similar shematic like that sheme,but stronger.
Problems is because that stronger sheme from internet I,m not sure that will work ok.
This sheme is checked.

Mooly, I understand that,I think that with ,,bipolar" capacitors not worth it.
Please,coud you tell me iff I can do my sheme in bridge mode with classic capacitor(output) because I've single supplay in sheme.
In bridge mode I need to single supplay same in single(classic) mode amplifier.
Second, I know that bridge amplifiers have more greater distortion than standard aplication.
I would like to do in bridge mode bacause that amplifier is more simple to build...
I need few parts for build....etc, but only problem is low power.
How I can solve the problem with 0 volts in coupled point?
Thank's!
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Old 10th November 2009, 12:36 PM   #36
Mooly is online now Mooly  United Kingdom
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Pigy,
If you use the discrete amp circuit you posted at the start in bridge mode you need a suitable phase splitter (using opamps) to give you the two inputs to each amp. You understand that... a bridge amp MUST be fed with signals that are 180 degress out of phase.
If you can arrange that then you need only a single speaker coupling cap (bipolar... so that's two in series) cap of say 2200 mfd (two 4700's back to back)
There is no problem with the 0 (zero) point, the inputs are ground referenced, the speaker connected between the amp outputs.
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Old 10th November 2009, 02:49 PM   #37
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Can you please explain why you prefer to use an output coupling cap in bridge.
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Old 10th November 2009, 04:34 PM   #38
Mooly is online now Mooly  United Kingdom
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Quote:
Originally Posted by richie00boy View Post
Can you please explain why you prefer to use an output coupling cap in bridge.
Because the circuit Pigy has posted has a mid point voltage (DC volts at amp output) that is not well defined and that will drift with temperature and rail variations. It's a non problem normally but DC coupling a speaker between two such amps will give an offset voltage of perhaps 2 to 3 volts or so, maybe more.

With an IC based design on split supplies that doesn't happen.

With an IC design on a single supply the problem can be better managed by using a precise DC reference to set the operating point of both amps. You can not do that for the discrete design however as it is "single ended" and prone to drift.
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Old 10th November 2009, 05:02 PM   #39
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Quote:
Originally Posted by Mooly View Post
Because the circuit Pigy has posted has a mid point voltage (DC volts at amp output) that is not well defined and that will drift with temperature and rail variations. It's a non problem normally but DC coupling a speaker between two such amps will give an offset voltage of perhaps 2 to 3 volts or so, maybe more.

With an IC based design on split supplies that doesn't happen.

With an IC design on a single supply the problem can be better managed by using a precise DC reference to set the operating point of both amps. You can not do that for the discrete design however as it is "single ended" and prone to drift.
Some years ago I find on the web a German diy project, that have the same topology. Unfortunately this article is deleted. Because I have store this websites, I have make a pdf file (see botton). The same author has descript a possible of a bridged version about this topology - but unfortunately this article I haven't. Both article was release in the no longer available German diy magazine "ELRAD" (not "elector") between 1985 and 1990 - as I know.
You can ask Mr. Gerhard Haas about this article, title "Brücken-Teufel" (bridge devil) - Go to the weblink
EXPERIENCE electronics - Contact
to send an e-mail about this -
because about EXPERIENCE electronics - HiFi-Amplifiers 'Classic'-Series
this information presently not available
Attached Files
File Type: pdf Black Devil-I.pdf (79.2 KB, 122 views)
File Type: pdf Black Devil-II.pdf (125.1 KB, 105 views)
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Old 10th November 2009, 05:10 PM   #40
wg_ski is offline wg_ski  United States
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It will take a bit of care to get the offsets to cancel, but it's possible. You need to bias from a common point and match the input stages. Use 1/2 the value of R3, double C2, and make this common for both halves. Match R2's and R1's, as well as T1's. A matched diff pair in a common can would be best for the input stage. Do this and the offset will be just fine, but if you go to this much trouble you may as well build a more advanced circuit.

The other thing you need is a phase splitter, which can be a separate outboard unit or just play with the feedback. One way is to add another resistor the same as R6 from the output of the first amp to the summing node of the second. The other way is to connect the feedback grounds (the R5 C3 ground connection) to each other instead of to ground.
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