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Old 21st March 2006, 11:49 PM   #1
mikee55 is offline mikee55  United Kingdom
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Lightbulb Class A(Transistor) V Gainclone Debate

Hi everyone,I want to build a new Amplifier but am hopeless at making my mind up.I keep going round in circles.I made a Class A Emitter follower using TIP 141 bipolars and it was amazing,I had to keep it cool with an office fan.I'm using a chip amp from a pair of Sony PC speakers,nothing special,and it says 7watts max on the label.And yet such a small amp sounds amazing as well, driving my Goodmans Magnum K2,which are rated 50w @ 4 ohms with a 12" Bass driver.And sounds better than my JVC A-X2 @ 90w and my Technics SU V2 @ 120w.The JVC a Super A,fancy name,and with Transistors.The Technics had STK blocks and both units and are dead.
It seems as though my speakers prefer less power,making a Class A or a Chip amp ideal,especially Class A,because of heatsink size and cost.
I have a Toroid Transformer rated @ 2 x 40 volts and 5 amps each.This I would use in the power supply because it was expensive,and I have 4 x 8600uf caps from the above amplifiers,so what should I build around this supply?

Class A ? Gain clone ?
Thanks,Mikee55
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Old 22nd March 2006, 12:07 AM   #2
jleaman is offline jleaman  Belgium
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Default Re: Class A(Transistor) V Gainclone Debate

Quote:
Originally posted by mikee55
Hi everyone,I want to build a new Amplifier but am hopeless at making my mind up.I keep going round in circles.I made a Class A Emitter follower using TIP 141 bipolars and it was amazing,I had to keep it cool with an office fan.I'm using a chip amp from a pair of Sony PC speakers,nothing special,and it says 7watts max on the label.And yet such a small amp sounds amazing as well, driving my Goodmans Magnum K2,which are rated 50w @ 4 ohms with a 12" Bass driver.And sounds better than my JVC A-X2 @ 90w and my Technics SU V2 @ 120w.The JVC a Super A,fancy name,and with Transistors.The Technics had STK blocks and both units and are dead.
It seems as though my speakers prefer less power,making a Class A or a Chip amp ideal,especially Class A,because of heatsink size and cost.
I have a Toroid Transformer rated @ 2 x 40 volts and 5 amps each.This I would use in the power supply because it was expensive,and I have 4 x 8600uf caps from the above amplifiers,so what should I build around this supply?

Class A ? Gain clone ?
Thanks,Mikee55

40v ac thats to much. I don't think your building a class a amp.
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Old 22nd March 2006, 12:27 AM   #3
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Well, if that 40V is unrectified it is a bit too much for a GC as well. That voltage rating with that current is only really useful for a Class A/B amp, but there are plenty of good ones around, have a look in SS for SKA, AKSA etc...
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Old 22nd March 2006, 11:16 AM   #4
AndrewT is offline AndrewT  Scotland
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Hi,
that 40Vac 400Va transformer would suit ClassAB power amp upto about 250W to 300W total output.

A 2channel GB150 SKA driving 140W into 8ohms falls right into this category.

There are many other candidates producing similar outputs.

A single channel 250W into 4ohms is another option (using all you caps) but may not suit your stereo requirement.

For good (or better) bass performance you will need to increase your smoothing capacitance. A target of about +-12mF/channel should suffice for 8ohm speakers and double this for 4ohm.
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Old 22nd March 2006, 11:55 AM   #5
mikee55 is offline mikee55  United Kingdom
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Default Thankyou

for your thoughts.

Hi all,thankyou,erm,could I use Regulation to bring the voltage down?Might seem like a waste of power,but it would save me buying another transformer!

Thankyou.Mikee55
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Old 22nd March 2006, 12:43 PM   #6
grrr is offline grrr  Netherlands
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Default do not regulate down

look at zen lite from pass that uses a high voltage. you do not have to use a current source because you can use a higher impedance resistor (or lamp) as load .

http://www.passdiy.com/projects/zenlite1.htm

you can make a 40v+ somthing powersuply and for example a class a amp that has a idle current of 1A than use a 30 ohm resistor as load.
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