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Old 5th August 2012, 10:53 AM   #11
dadod is offline dadod  Croatia
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After extensive simulation here is the schematic, I think, to be used in practical implementation of this amp.
The distortion at 20kHz and 320W/4ohm is now a bit higher, risen from 0.96 ppm to 1.4 ppm but it is more stable now. During the power simulation I noticed a small oscillation at 3MHz. That was solved with R77, C33 and R78, C34 added between the drivers and output transistors in the power lines.

Combinations of the output transistors could be used for different output power and different power supply voltage.

Full power 350W/4ohm and +- 65 V of the power supply: NJL3282/1302 and MJL3281/1302

Lower power 230W/4ohm and +-55 V of the power supply: NJL0281/0302 and MJL0281/0302 (or MJW0281/0302)

I expect that lower power version could sound a bit better as suggested output transistors have lower Cob of 400pF compared with 600pF of the higher power version.
dado
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File Type: pdf DADO-TT-370w.pdf (84.4 KB, 147 views)
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Old 6th August 2012, 07:14 AM   #12
dadod is offline dadod  Croatia
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This is FFT at 15 W and 315 W on 4 ohm respectively.
dado
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File Type: jpg FFT-3kHz-15W_4ohm.jpg (162.6 KB, 468 views)
File Type: jpg FFT-3kHz-315W_4ohm.jpg (159.2 KB, 356 views)
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Old 6th August 2012, 07:17 AM   #13
dadod is offline dadod  Croatia
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Power dissipation of one output transistor and one power transistor in C multiplier. Load is 2 ohm.
dado
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File Type: jpg Powerdissipation-on one Cmult TR_2ohm.jpg (172.5 KB, 283 views)
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Old 6th August 2012, 05:12 PM   #14
Bensen is offline Bensen  Belgium
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Quote:
Originally Posted by dadod View Post
This is FFT at 15 W and 315 W on 4 ohm respectively.
dado
Hi Dadod,

I always have a look at your threads when something new is posted.
Your amps are looking very well designed. And to be honest, a bit to complex for me.

Your FFT's are looking very good, but most people here are using the the "Blackman" windowing function when showing the FFT.
Can you perform the FFT's again with the "Blackman" selected?

I use them as reference.

Greetz
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Old 6th August 2012, 06:58 PM   #15
dadod is offline dadod  Croatia
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Quote:
Originally Posted by Bensen View Post
Hi Dadod,

I always have a look at your threads when something new is posted.
Your amps are looking very well designed. And to be honest, a bit to complex for me.

Your FFT's are looking very good, but most people here are using the the "Blackman" windowing function when showing the FFT.
Can you perform the FFT's again with the "Blackman" selected?

I use them as reference.

Greetz
Here are the Blackman FFTs.
Actually it is not so complex, you can skip Loudspeaker ptotection if you don't like this type of the protection(circled).
dado
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File Type: jpg FFT-Blackman-3kHz-15W_4ohm.jpg (165.6 KB, 74 views)
File Type: jpg FFT-Blackman-3kHz-315W_4ohm.jpg (170.6 KB, 75 views)
File Type: jpg DADO-TT-370W-no-LP.jpg (294.0 KB, 265 views)
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Old 6th August 2012, 07:20 PM   #16
Bensen is offline Bensen  Belgium
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I don't have the experience yet to make the corrolation between FFT simulation and my hearing.
My last amp: http://www.diyaudio.com/forums/solid...woofer-10.html
has about the same FFT tendency as yours, many high order harmonics with clearly no higher 2nd and 3th. To be honest, I must say that I'm missing something in the music, it doesn't sound "open/transparent" enough.


My current amp in the designing process has a FFT simulation as in the picture below. ==> this is made at 1Wrms. 1W is my reference, this is already more than normal listening output power.
I'm curious about the sound.
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Old 6th August 2012, 07:26 PM   #17
a.wayne is offline a.wayne  United States
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Wouldn't you need more than 4 pr for 2 ohm operation at that power output ...?
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Old 6th August 2012, 07:44 PM   #18
dadod is offline dadod  Croatia
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Quote:
Originally Posted by Bensen View Post
I don't have the experience yet to make the corrolation between FFT simulation and my hearing.
My last amp: http://www.diyaudio.com/forums/solid...woofer-10.html
has about the same FFT tendency as yours, many high order harmonics with clearly no higher 2nd and 3th. To be honest, I must say that I'm missing something in the music, it doesn't sound "open/transparent" enough.


My current amp in the designing process has a FFT simulation as in the picture below. ==> this is made at 1Wrms. 1W is my reference, this is already more than normal listening output power.
I'm curious about the sound.
Here is FFT at 1kHz 1W on 8ohm.
ddo
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Old 6th August 2012, 07:45 PM   #19
AndrewT is online now AndrewT  Scotland
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power/voltage drops from 200W into 8r0 to 375W into 4r0, i.e. -0.56dBW
and drops from 375W to 701W into 3r0, i.e. -0.59dBW.
These two drops seems surprisingly close.

I would expect the drop into 4r0 to be much less than the drop into 2r0.
How did you measure these output figures?
Were the mains supply voltages the same? Did you meausre the mains supply voltages for all three output power measurements?
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Old 6th August 2012, 07:48 PM   #20
AndrewT is online now AndrewT  Scotland
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Quote:
Originally Posted by a.wayne View Post
Wouldn't you need more than 4 pr for 2 ohm operation at that power output ...?
2r0 loading is an easy load for a 4ohm rated amplifier.
I would expect every 4ohm rated amplifier to be able to drive a 2r0 test load without any difficulty. The only problem would be extended testing raising the heatsink temperature above the design target limit.

If you need a 2ohm rated amplifier, then it must be able to drive a 1r0 test load and preferably lower.
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