5W Single Ended Class A Power Amp From Mark Houston - Page 2 - diyAudio
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Old 12th April 2011, 01:13 AM   #11
SSDIY is offline SSDIY  Hong Kong
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Quote:
Originally Posted by lineup View Post
Here is a version for 2SJ162.

Note that power supply V+ is connected to GROUND.
And so GROUND is the upper part.
But as long as you note polarity of electrolytic capacitors
it should not be a problem.

A stereo system should be 2 such with 2SJ162
as 2SK1058 has a bit different caracteristic from 2SJ162.
Hi lineup

Thank you very much for the 2SJ162 schematic. It is clear and very helpful. I want to build two of this amps for my bi-amp speaker system one amp use 2SK1058 and the other amp use 2SJ162.
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Old 12th April 2011, 01:47 AM   #12
Bigun is offline Bigun  Canada
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With the +24V and -24V supplies, you may be able to bridge them for higher power if wanted in the future (you'll need to provide for signal inversion somewhere)
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Old 13th April 2011, 12:29 AM   #13
SSDIY is offline SSDIY  Hong Kong
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Quote:
Originally Posted by Bigun View Post
With the +24V and -24V supplies, you may be able to bridge them for higher power if wanted in the future (you'll need to provide for signal inversion somewhere)
Hi Bigun

It is a good idea to bridge the amp to get more power to driver the speakers. Thank you for reminding.
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Old 13th April 2011, 12:39 AM   #14
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Keep in mind that once you bridge this circuit its no longer single-ended and 2nd harmonic is suppressed leaving a prominent 3rd. Also, you still have to come up with the bias current to run double peak voltage into whatever load.
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Old 13th April 2011, 10:08 AM   #15
AndrewT is offline AndrewT  Scotland
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Hi,
a 1058 or a 162 can easily be biased to ~1.3 to 1.4A
This will give ~8W into 8ohms from your +24V supply.
Adding a complementary transistor to convert the circuit to push-pull would be better than going balanced.
Pass has lots of variations on SE, PP, Balanced.
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Old 13th April 2011, 12:37 PM   #16
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Hi Andrew.
I'm assuming we are still using the original circuit as in post 1.
To run 1.4A bias current, the 15R resistor will need to be changed to 8.6R.
The peak output current is now 8.6R plus 8R (assuming 8R speaker load), with 12 V peak. Ie 12 volts across 16.6R = 0.72A
Peak power is Isquared times load so = 4Watts, RMS power 2 W.
This is a somewhat inefficient circuit.
You are spot on with the suggestion of going push pull, you'd get the full 12 V peak across the 8R load (assuming no losses), ie. 1.5 A which would translate to 9W rms.
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Old 13th April 2011, 12:47 PM   #17
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Taking another look at the circuit, the design parameters are quite wrong.
The 'mid point' output voltage should not be 12V. For maximum output into 8R it should be at 8 Volts. This would instantly quadruple the power output!
We'd get an earth shattering 4W rms. (with the original 15R resistor)
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Old 13th April 2011, 01:32 PM   #18
lineup is offline lineup  Sweden
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Quote:
Originally Posted by toprepairman View Post
Taking another look at the circuit, the design parameters are quite wrong.
The 'mid point' output voltage should not be 12V. For maximum output into 8R it should be at 8 Volts. This would instantly quadruple the power output!
We'd get an earth shattering 4W rms. (with the original 15R resistor)
You are right. Should be lower than 12 Volt.
The original that people build has got output at 12 Volt.
Which is not optimal.
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Old 13th April 2011, 01:41 PM   #19
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by toprepairman View Post
The peak output current is now 8.6R plus 8R (assuming 8R speaker load), with 12 V peak. Ie 12 volts across 16.6R = 0.72A
Peak power is Isquared times load so = 4Watts, RMS power 2 W.
This is a somewhat inefficient circuit.
I should have done the sums. I've been bad, now where did I put the Dunce's hat?

I have not used resistor loading in a power amp and so momentarily forgot the halving of efficiency that comes with going from PP to SE with CCS and a further halving when going from SE CCS load to SE resistor load.

Arithmetic is a very powerful tool and I do know better than to ignore it.
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Old 13th April 2011, 02:04 PM   #20
SSDIY is offline SSDIY  Hong Kong
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Quote:
Originally Posted by Andrew Eckhardt View Post
Keep in mind that once you bridge this circuit its no longer single-ended and 2nd harmonic is suppressed leaving a prominent 3rd. Also, you still have to come up with the bias current to run double peak voltage into whatever load.
Hi Andrew

May I ask what is the different between bridged and balanced if I make this amp a balanced (4 boards of this circuit one for + phase signal and one for - phase signal x 2 channel for a stereo 2 channel amp)? Please advice as my other thread in this forum I am going to change my entire stereo system from RCA to XLR.
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