I buid this amp but no have 1,3v zener diode ..the small value is 2,2v any solution?
http://www.pi.infn.it/~federico/Immagini/gl.zip
http://www.pi.infn.it/~federico/Immagini/gl.zip
Use silicon diodes in series for small values. Each diode is approx 0.6 volts. Use LED's, different colours have different volt drops.
I would use two 1N4148 in series like Mooly suggested.
Use like 2-3 mA. This will give close to 1.3 V.
This makes R7 could be 22k or 15k.
I should try 15k = 3mA
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The precise voltage (1.3V) at Q4 base is not the important thing.
The thing is to get close to 20 mA (0.020 Ampere) through Q4.
After you have got something like 1-1.5 Volt at Q4 base, measure voltage across R12.
If is, for example 0.60 Volt.
Then current is = 0.60V/27Ohm = 22.2mA. Close enough!
If voltage across R12 is 0.40V, then we get current is:
0.40V/27Ohm = 14.8 mA
... so we will change R12 to 20 Ohm.
Current is now:
0.40V/20 = 20mA. Which is the current we want in Q4
Formula, to get 20mA (0.020 Ampere):
R, Ohm = Voltage across R12 / 0.020
Use like 2-3 mA. This will give close to 1.3 V.
This makes R7 could be 22k or 15k.
I should try 15k = 3mA
-------
The precise voltage (1.3V) at Q4 base is not the important thing.
The thing is to get close to 20 mA (0.020 Ampere) through Q4.
After you have got something like 1-1.5 Volt at Q4 base, measure voltage across R12.
If is, for example 0.60 Volt.
Then current is = 0.60V/27Ohm = 22.2mA. Close enough!
If voltage across R12 is 0.40V, then we get current is:
0.40V/27Ohm = 14.8 mA
... so we will change R12 to 20 Ohm.
Current is now:
0.40V/20 = 20mA. Which is the current we want in Q4
Formula, to get 20mA (0.020 Ampere):
R, Ohm = Voltage across R12 / 0.020
Attachments
re
diodes no work for me and red and green led too. have an ac sound in the speaker(cheap speaker)
i see again the formula thanks to all
diodes no work for me and red and green led too. have an ac sound in the speaker(cheap speaker)
i see again the formula thanks to all
Whats 28ma. Do you mean the current through R12. The absolute value in itself is not too critical but I do see that the amp has no adjustment for quiescent current.
I would be happier with R10 replaced by a 2.2k preset set initially to it's highest value ie 2.2k. That will give no current through the outputs, much safer for testing.
Anyway I would use I think 3 IN4148's ( you realise they go the other way round to a zener !! ) to give a little compliance and adjust R12 to give around 20 ma.
I would be happier with R10 replaced by a 2.2k preset set initially to it's highest value ie 2.2k. That will give no current through the outputs, much safer for testing.
Anyway I would use I think 3 IN4148's ( you realise they go the other way round to a zener !! ) to give a little compliance and adjust R12 to give around 20 ma.
Re: re
How old is the amplifier?
The AC sound, how does it sound? Can you tell more.
The adjustment of Q4 and R12 has nothing to do with the AC sound.
Must be something else.
tadiam said:
How old is the amplifier?
The AC sound, how does it sound? Can you tell more.
The adjustment of Q4 and R12 has nothing to do with the AC sound.
Must be something else.
re re
now work well have an small crak in the speaker when turrn on/off the amp but work well.the sound not is special but sound well.
thanks again t
he seach continue
now work well have an small crak in the speaker when turrn on/off the amp but work well.the sound not is special but sound well.
thanks again t
he seach continue
re question
hey mooly do you know this company.is of your country
http://www.dnm.co.uk/materials.html
I am curious.
In the photo see (too read)..mos fet in the output (two per channel)regolarors too two per channels.
an integrated circuit CI ?..and no much more...and...price hight too.
how sound this listen this any conceptual schema....
hey mooly do you know this company.is of your country
http://www.dnm.co.uk/materials.html
I am curious.
In the photo see (too read)..mos fet in the output (two per channel)regolarors too two per channels.
an integrated circuit CI ?..and no much more...and...price hight too.
how sound this listen this any conceptual schema....
I have heard of the company and Dennis Morecroft, but have never listened to, or seen any of the products.
There is a lot of marketing talk in all that info, and as with any design it's how it ultimately performs that is what matters most.
What speakers and source are you using. How good an amp are you after ?
There is a lot of marketing talk in all that info, and as with any design it's how it ultimately performs that is what matters most.
What speakers and source are you using. How good an amp are you after ?
It doesn't pay to read the DNM blurb too closely.
They space the power transistors off the aluminium heatsink using an aluminium oxide spacer. The problem with that is that aluminium oxide has a thermal conductivity of 18 W/m.K while aluminium has a thermal conductivity of 237 W/m.K. So the 'thermal coupler' has a thermal conductivity that is only 7% of the heatsink - not too smart I would have thought
They space the power transistors off the aluminium heatsink using an aluminium oxide spacer. The problem with that is that aluminium oxide has a thermal conductivity of 18 W/m.K while aluminium has a thermal conductivity of 237 W/m.K. So the 'thermal coupler' has a thermal conductivity that is only 7% of the heatsink - not too smart I would have thought
amazing that he can sell an amp like this for thousands of $'s.
Wish I had that ability.
But maybe he doesn't sell many, and drives a 10 year old VW.
Hmmm.
Wish I had that ability.
But maybe he doesn't sell many, and drives a 10 year old VW.
Hmmm.
re re
I use an ls70 polk speakers(1200 Pounds..price..in an old hi fi choice) naks cd an cassette...ned tuner yamaha tuner...sl1200 mk2 turntabe ,ortofon cartridge and my comercial amp is an HK1400 line amp...and an small pair ob infinity reference EL speakers too old.
I use an ls70 polk speakers(1200 Pounds..price..in an old hi fi choice) naks cd an cassette...ned tuner yamaha tuner...sl1200 mk2 turntabe ,ortofon cartridge and my comercial amp is an HK1400 line amp...and an small pair ob infinity reference EL speakers too old.
re2
now build an small op amp amplifier 4 transistors and an op amp and sound more clear.is easy...i work over this have diference in the sound when exchange the power supply type ...diodes zeners or discrete regulators...
now build an small op amp amplifier 4 transistors and an op amp and sound more clear.is easy...i work over this have diference in the sound when exchange the power supply type ...diodes zeners or discrete regulators...
no matter all the above
is this an amplifier worth constructing ????
it looks like my kind if amps .....very simple to make
any opinions about it ????
thanks
is this an amplifier worth constructing ????
it looks like my kind if amps .....very simple to make
any opinions about it ????
thanks
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