Sounds alike this one
http://www.youtube.com/watch?v=warJLziW6gk
This one uses the same schematic, same topologie...sound is almost the same.
Also you have, into youtube, audio testing made with the Dx Amplifier:
http://www.youtube.com/watch?v=SoZA5f7wJhM
regards,
Carlos
http://www.youtube.com/watch?v=warJLziW6gk
This one uses the same schematic, same topologie...sound is almost the same.
Also you have, into youtube, audio testing made with the Dx Amplifier:
http://www.youtube.com/watch?v=SoZA5f7wJhM
regards,
Carlos
It is very important to use a good supply to the Dx Amplifier
I will show you my supply, the one used to test.
It is using, now a days, 27000uf plus 27000uf.
The voltage without load is 44 plus 44 volts.
When i am draining 2.6 amperes each rail the voltage goes to the nominal voltage suggested to the Dx Amplifier, 36 plus 36 volts.
So, the supply is correct to the amplifier.... when producing 100 watts over 4 ohms loads, the voltage will be the correct one....
Using it to 8 ohms loads you gonna have much more than 50 watts RMS, as voltage drop will be smaller.
Here you can see the supply voltage.
Under load conditions... supply is loaded with 14 ohms resistance (2 resistances of 7 ohms and 70 watts each one of them)
regards,
Carlos
I will show you my supply, the one used to test.
It is using, now a days, 27000uf plus 27000uf.
The voltage without load is 44 plus 44 volts.
When i am draining 2.6 amperes each rail the voltage goes to the nominal voltage suggested to the Dx Amplifier, 36 plus 36 volts.
So, the supply is correct to the amplifier.... when producing 100 watts over 4 ohms loads, the voltage will be the correct one....
Using it to 8 ohms loads you gonna have much more than 50 watts RMS, as voltage drop will be smaller.
Here you can see the supply voltage.
Under load conditions... supply is loaded with 14 ohms resistance (2 resistances of 7 ohms and 70 watts each one of them)
regards,
Carlos
Attachments
Here you can see the ripple.... and this was measured
while the supply was loaded..... a rail beeing loaded and the ripple was around 1 volt peak to peak.
Observe the scope channel two is adjusted to 1 volts peak to peak... this represents a very small power into 8 ohms speaker.
The amplifier will be producing more than 100 watts RMS, while the mains noise, the ripple power, will be lower than 50 miliwatts RMS...so... you will not even listen.
So.... when reproducing music, full power, you will not have strong mains frequency noises (ripple) mixed with your audio.
regards,
Carlos
while the supply was loaded..... a rail beeing loaded and the ripple was around 1 volt peak to peak.
Observe the scope channel two is adjusted to 1 volts peak to peak... this represents a very small power into 8 ohms speaker.
The amplifier will be producing more than 100 watts RMS, while the mains noise, the ripple power, will be lower than 50 miliwatts RMS...so... you will not even listen.
So.... when reproducing music, full power, you will not have strong mains frequency noises (ripple) mixed with your audio.
regards,
Carlos
Attachments
What this really means.
If you plug a 8 hertz tone into your amplifier, and adjust to full power.... or 100 watts RMS into 4 ohms loads, then you will not listen audio, as 8 hertz is not audible to humans...you feel vibrations only..... but if you have ripple, then you will listen the ripple..in our case..this small ripple is almost inaudible..you have to almost touch the speaker diafragm with your ears to listen it clear...and may receive a big punch from the speaker into your
face.... be carefull with that..also air pressure into your ears may be dangerous..use some cotton to attenuate.
Well...you may say:
- "What a hell.... who cares about no audible tones.... what's the advantage not to listen noises when i am also not listening to the tones"
Well..this will happens with music too..with the tones you listen..they will not have this dirty ripple poluting your audio clarity.
5000uf each rail to each ampere is the minimum filter...better to use more than that.... i am using, now a days, 27000uf each rail, not only to the Dx Amplifier, but also to the DHR Turbo.
regards,
Carlos
If you plug a 8 hertz tone into your amplifier, and adjust to full power.... or 100 watts RMS into 4 ohms loads, then you will not listen audio, as 8 hertz is not audible to humans...you feel vibrations only..... but if you have ripple, then you will listen the ripple..in our case..this small ripple is almost inaudible..you have to almost touch the speaker diafragm with your ears to listen it clear...and may receive a big punch from the speaker into your
face.... be carefull with that..also air pressure into your ears may be dangerous..use some cotton to attenuate.
Well...you may say:
- "What a hell.... who cares about no audible tones.... what's the advantage not to listen noises when i am also not listening to the tones"
Well..this will happens with music too..with the tones you listen..they will not have this dirty ripple poluting your audio clarity.
5000uf each rail to each ampere is the minimum filter...better to use more than that.... i am using, now a days, 27000uf each rail, not only to the Dx Amplifier, but also to the DHR Turbo.
regards,
Carlos
Attachments
I have increased my DHR Turbo supply that was not using all the capacitance needed
This way i have reduced the 2.8 volts peak to peak ripple to less than 1 volts peak to peak.
Capacitance increased from 12.000uf plus 12.000uf to 27.000uf plus 27.000uf.
And i really think that 40K each rail would be even better.
regards,
Carlos
..............................................................................................
Before this encreasing in capacitance i was able to listen some noise..some ripple...not difficult to listen...but now a days sittuation is much better.
This way i have reduced the 2.8 volts peak to peak ripple to less than 1 volts peak to peak.
Capacitance increased from 12.000uf plus 12.000uf to 27.000uf plus 27.000uf.
And i really think that 40K each rail would be even better.
regards,
Carlos
..............................................................................................
Before this encreasing in capacitance i was able to listen some noise..some ripple...not difficult to listen...but now a days sittuation is much better.
Attachments
Re: I have found some unstabilities... system not aproved!
What is the startup sequence for this amp to set bias and what is the preferred bias level?
I have read many hundreds of posts, and am confused.
Many times Carlos says to set bias then offset then bias and so on....but here on the Nordic boards there is only 1 trimpot, VR1 for bias and there is no VR2 for offset.
Schematic - I think this is accurate for the Nordic boards
Even the procedure on http://users.tpg.com.au/users/gerskine/dxamp/dx%20amplifier-07.htm mentions VR3 which is not in this circuit and it uses components and test points not applicable to the Nordic boards.
All I have available to adjust is the VR1/bias resistor which is VR3 on the DX web pages
Usually the procedure is to measure voltage across emitter resistors and set to the desired bias. So turn VR1 until you get 8.8 mV across R25 or R26, this is equal to 40mA in the 0.22 ohm resistors.
However, it appears that the suggestion is to put in power resistors into the DC rails and measure the current draw. 33 ohm resistors in series with + rail and dropping 1.5 volts means about 45 mA is being drawn from the + rail (which draws about 10 mA more than the - rail).
It also appears that VR1 (bias) should be set to 0 ohms when starting.
Will this work-
1. Set VR1 to 0 ohms.
2. plug amp in to variac
3. turn on and turn up voltage slowly, watching voltage across R25
4. turn up voltage slowly... till DC supplies are near where they should be.
5. adjust VR1 so that current is flowing about 2-3 mV measured across R25.
6. turn up all the way and measure offset at output, which you can't adjust. Hope that offset is low!
7. let sit and watch voltage across R25, adjusting VR1 and after 1 hour it should be 8.8 mV = 40 mA.
8. measure voltage R26, it should also be 8.8 mV.
???
OR is there some reason to measure the complete current draw of the + rail by using the resistors in series (slowly increasing variac and finally adjusting VR1 so that after 1 hour you have 1.5 volts across 33 ohms = 45mA?)
What is the startup sequence for this amp to set bias and what is the preferred bias level?
I have read many hundreds of posts, and am confused.
Many times Carlos says to set bias then offset then bias and so on....but here on the Nordic boards there is only 1 trimpot, VR1 for bias and there is no VR2 for offset.
Schematic - I think this is accurate for the Nordic boards
Even the procedure on http://users.tpg.com.au/users/gerskine/dxamp/dx%20amplifier-07.htm mentions VR3 which is not in this circuit and it uses components and test points not applicable to the Nordic boards.
All I have available to adjust is the VR1/bias resistor which is VR3 on the DX web pages
Usually the procedure is to measure voltage across emitter resistors and set to the desired bias. So turn VR1 until you get 8.8 mV across R25 or R26, this is equal to 40mA in the 0.22 ohm resistors.
However, it appears that the suggestion is to put in power resistors into the DC rails and measure the current draw. 33 ohm resistors in series with + rail and dropping 1.5 volts means about 45 mA is being drawn from the + rail (which draws about 10 mA more than the - rail).
It also appears that VR1 (bias) should be set to 0 ohms when starting.
Will this work-
1. Set VR1 to 0 ohms.
2. plug amp in to variac
3. turn on and turn up voltage slowly, watching voltage across R25
4. turn up voltage slowly... till DC supplies are near where they should be.
5. adjust VR1 so that current is flowing about 2-3 mV measured across R25.
6. turn up all the way and measure offset at output, which you can't adjust. Hope that offset is low!
7. let sit and watch voltage across R25, adjusting VR1 and after 1 hour it should be 8.8 mV = 40 mA.
8. measure voltage R26, it should also be 8.8 mV.
???
OR is there some reason to measure the complete current draw of the + rail by using the resistors in series (slowly increasing variac and finally adjusting VR1 so that after 1 hour you have 1.5 volts across 33 ohms = 45mA?)
We had, as optional, into HRII (this was posted into this same thread)
to use differential having resistances as colector loads (this way off set trimpot works) and the use of transistor as colector loads...the way you have into the schematic.... this way.... the off set control can be substituted by a fixed resistance as will not operate.
regards,
Carlos
to use differential having resistances as colector loads (this way off set trimpot works) and the use of transistor as colector loads...the way you have into the schematic.... this way.... the off set control can be substituted by a fixed resistance as will not operate.
regards,
Carlos
Well boys...i did my best...all was effort and some hard work
and i did it without ask for money...was pleasant to me and produced fun to a lot of folks that used to read....i think i did it the best i could.
Sorry not to be perfect..but at least i have tried and for sure i have produced a lot of amplifiers and texts to help beginners.
After mistakes done, is very easy to us to see the thread weak points..hard is when rolling all stuff to perceive what is good and what is bad....say...during the stuff rolling to stop to think about circuits and people questions and start to be evaluating... alike someone outside the problem. looking what is going on with binoculars... in a cold way...without emotions..only counting goods and bad moments.... it seems to much to me...also seems to me this is more adequated to moderators to be controling as supervisers... controling not to go out from the rails, off topic and that stuff.
Thread was special..had human relationship...some social moments too...and that made it interesting for some folks...i think was the strong point in my point of view...human.....had humanity.
It is not possible to give satisfaction to everyone...if you write too much, people may say that you write to much in a complaining way....and the opposite is also true.
I have to thank you two to point my errors..for sure i have made several and your feedback was very usefull during the thread....now a days..well..... those things are past...only a couple of delayed folks are building.
I hope people have learned with my errors the way i have learned, and also try to contribute with our forum.... the way you did Todd and also Greg.
I am more interested into the future.... those amplifiers are mumified so old they are...let's watch ahead..only one or two are assembling now a days...those threads resulted in enougth production.... many amplifiers were made by forum folks.... this was the result.
If people really wants...there are enougth information to assemble that can be readed... and much more than the needed in basic instructions to beginners... the ones do not want to build..well..those may prefere complain.... what can i do..they are not builders..they are thread analisers, organizers, criticisers and evaluators..not builders!
I am collecting things from this thread..pictures and builder names..to make a slide movie....and i am very happy to see how many folks have built.
regards,
Carlos
and i did it without ask for money...was pleasant to me and produced fun to a lot of folks that used to read....i think i did it the best i could.
Sorry not to be perfect..but at least i have tried and for sure i have produced a lot of amplifiers and texts to help beginners.
After mistakes done, is very easy to us to see the thread weak points..hard is when rolling all stuff to perceive what is good and what is bad....say...during the stuff rolling to stop to think about circuits and people questions and start to be evaluating... alike someone outside the problem. looking what is going on with binoculars... in a cold way...without emotions..only counting goods and bad moments.... it seems to much to me...also seems to me this is more adequated to moderators to be controling as supervisers... controling not to go out from the rails, off topic and that stuff.
Thread was special..had human relationship...some social moments too...and that made it interesting for some folks...i think was the strong point in my point of view...human.....had humanity.
It is not possible to give satisfaction to everyone...if you write too much, people may say that you write to much in a complaining way....and the opposite is also true.
I have to thank you two to point my errors..for sure i have made several and your feedback was very usefull during the thread....now a days..well..... those things are past...only a couple of delayed folks are building.
I hope people have learned with my errors the way i have learned, and also try to contribute with our forum.... the way you did Todd and also Greg.
I am more interested into the future.... those amplifiers are mumified so old they are...let's watch ahead..only one or two are assembling now a days...those threads resulted in enougth production.... many amplifiers were made by forum folks.... this was the result.
If people really wants...there are enougth information to assemble that can be readed... and much more than the needed in basic instructions to beginners... the ones do not want to build..well..those may prefere complain.... what can i do..they are not builders..they are thread analisers, organizers, criticisers and evaluators..not builders!
I am collecting things from this thread..pictures and builder names..to make a slide movie....and i am very happy to see how many folks have built.
regards,
Carlos
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