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Old 13th October 2012, 09:05 AM   #11
AndrewT is online now AndrewT  Scotland
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testing.
try driving a 1r0 test load for two seconds. That is not as stressful as driving a 2ohm speaker.

If the test results for the 1r0 load are good, then consider testing into a 0r7 for two seconds.
If the results are good then you can proceed with trying to establish the de-rated SOAR for reactive speaker loadings of 2ohms.
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Old 13th October 2012, 11:56 AM   #12
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Default Dear friends, i have decided to give up related this amplifier

I have found it is not producing the power i want...the efficiency is too much low, despite the sonics are awesome.

Even considering my 90 volts supply has huge voltage drop under load (drop to 73 volts when draining 400 watts from the supply)... i do think it should transfer more power to the speaker/load.

I have tried all i know.... modifications into currents, voltages, style of VAS, i have use three different VAS circuits, modifications into driver currents and output stand buy current...input modifications, gain modification...and no way to increase efficiency.... also all transistors where replaced several times in order to achieve more amplification.

I am uploading a video, as i have tested the unit this early morning and it is already operating as friends will come to the burial celebration of this unit that was considered not good to continue alive.

I thank you all by the posts, messages and emails, but after you spend several hours trying, we should decide to stop to try to have milk from stones.... this circuit i have made, this modified Dx amplifier, operating with 90 volts supply, have not produced the power i was supposing it would produce.... i could go to 190 watts RMS only..when my wish was to go to 300 - 350 watts.

Video is being uploaded showing something and reporting that i give up....not approved!

By the way..thank you Andrew T.... sadly the amplifier was not approved, but i read your tip and it was memorized to be used next time.

regards,

Carlos
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Power supply; ripple, filter, noise, stability and the use of capacitance multiplier... Portuguese and English; https://www.youtube.com/watch?v=sSm0ku1eIgg

Last edited by destroyer X; 13th October 2012 at 11:58 AM.
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Old 13th October 2012, 12:14 PM   #13
Bensen is offline Bensen  Belgium
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Quote:
Originally Posted by destroyer X View Post
Wanna help?... then inform how many output pairs i gonna need to face all that peak power?

Maybe 36 output transistors.... i have not observed that for a while... the amplifier is in prototype moment, so, i am open to suggestions and help.

Carlos
Hi carlos,

According to my calculations. 20Pairs is a good number.
Have a look at the pictures, calcutions are done with:
==> heatsink temperature is 50degrees
==> phase angle at load at 2ohm is 35degrees

My
Attached Images
File Type: jpg DX For bass - 20pairs - 1300Wrms - 2R.JPG (190.0 KB, 114 views)
File Type: jpg DX For bass - input parameters.JPG (53.4 KB, 112 views)
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Old 13th October 2012, 12:21 PM   #14
AJT is offline AJT  Philippines
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Quote:
Originally Posted by destroyer X View Post
I have found it is not producing the power i want...the efficiency is too much low, despite the sonics are awesome.

Even considering my 90 volts supply has huge voltage drop under load (drop to 73 volts when draining 400 watts from the supply)... i do think it should transfer more power to the speaker/load.

I have tried all i know.... modifications into currents, voltages, style of VAS, i have use three different VAS circuits, modifications into driver currents and output stand buy current...input modifications, gain modification...and no way to increase efficiency.... also all transistors where replaced several times in order to achieve more amplification.

I am uploading a video, as i have tested the unit this early morning and it is already operating as friends will come to the burial celebration of this unit that was considered not good to continue alive.

I thank you all by the posts, messages and emails, but after you spend several hours trying, we should decide to stop to try to have milk from stones.... this circuit i have made, this modified Dx amplifier, operating with 90 volts supply, have not produced the power i was supposing it would produce.... i could go to 190 watts RMS only..when my wish was to go to 300 - 350 watts.

Video is being uploaded showing something and reporting that i give up....not approved!

By the way..thank you Andrew T.... sadly the amplifier was not approved, but i read your tip and it was memorized to be used next time.

regards,

Carlos
use a bigger traffo or try classG or H instead....with classAB you are definitely limited to efficiency of about 64~70%

if you wish for 350watts per channel, then your power traffo should be able to give a secondary power of at least 1100watts, your primary should have a capacity of about 1500volt amperes....if you use such traffo, you will get your dream come true...
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Old 13th October 2012, 01:11 PM   #15
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Default Thank you by your comment dear Tony

I am uploading videos...here some images about the Dx Custom prototype.

Here you have a sample of it's sonics:

http://www.youtube.com/watch?v=DQYUaAYcqqI

Not approved!

regards,

Carlos
Attached Images
File Type: jpg Dx Custom 10.jpg (459.8 KB, 109 views)
File Type: jpg Dx Custom 11.jpg (617.9 KB, 102 views)
File Type: jpg Dx Custom 12.jpg (512.1 KB, 102 views)
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Power supply; ripple, filter, noise, stability and the use of capacitance multiplier... Portuguese and English; https://www.youtube.com/watch?v=sSm0ku1eIgg
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Old 13th October 2012, 01:54 PM   #16
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Default Dx Custom project give up

Here you have a video that explains:

Dx Custom not approved! - YouTube

regards,

Carlos
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Power supply; ripple, filter, noise, stability and the use of capacitance multiplier... Portuguese and English; https://www.youtube.com/watch?v=sSm0ku1eIgg
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Old 13th October 2012, 02:19 PM   #17
Boscoe is offline Boscoe  United Kingdom
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Quote:
Originally Posted by destroyer X View Post
I am uploading videos...here some images about the Dx Custom prototype.

Here you have a sample of it's sonics:

Dx Custom playing. - YouTube

Not approved!

regards,

Carlos
If this is the PSU your using how do you expect the rails not to sag?
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Old 13th October 2012, 02:25 PM   #18
Krisfr is offline Krisfr  United States
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It took 2 Dunlap Clarke 120 vct transformers to get 750 watts with 80,000 ufarads on each 120 rail. Had to bring it up with a 25 amp variac too. The DC trans where from the 1000 amp. If my memory serves me, I think each one weighed about 30 or 35 pounds. The one in your pictures is no where near as big as the ones I used.
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Old 13th October 2012, 05:45 PM   #19
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Default The one at the picture is a 500 watts unit...no more than that

Used only for testing purposes... of course i do not think it can produce high power.... for more than kilowatt we need a really big transformer that measures 2/3 of a small car battery (36Ah)

Also observe i have used only 6 transistors, because i know the transformer cannot put too much power out...the real thing should have 20 transistors or even more than that.

I understand you may think i am crazy trying to have this power from a so small transformer, the reason why is because this thread is new and some informations and ideas about this amplifier (Dx high power unit for bass) was published in the Dx amplifier thread and you may have not readed.

Uncle Charlie is making amplifier these last 52 years, and a couple of thousand units where produced.... for sure uncle is not dumb this way.

People should read more before to post things.... because just watching a picture will be confused not knowing the details about.... it is often used to feed high power amplifier with a small supply during testings, when we do not know if has a mistake in the prototype construction of not..the presence of a small transformer does not mean we gonna use that toy in the real thing.

I am still having fun..... the power was not approved...the efficiency was not good...but sound is fine:

http://www.youtube.com/watch?v=lQc0Xe43f-8

regards,

Carlos
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Power supply; ripple, filter, noise, stability and the use of capacitance multiplier... Portuguese and English; https://www.youtube.com/watch?v=sSm0ku1eIgg

Last edited by destroyer X; 13th October 2012 at 05:59 PM.
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Old 14th October 2012, 12:16 AM   #20
AJT is offline AJT  Philippines
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Carlos, now that you confirmed your amp works, it is now time to build yourself that 1500va or better traffo....
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