Dx Supply, output adjustable, stabilized power supply

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#181
Mister Terry have you seen mister Carlos videos? he operate Dx Super A with AA batteries

I mean this does not mean that your are going to do it, he is just showing that Dx Super A can operate at that minimum supply voltage

Audio amp. powered by Triple A batteries - Amp. movido à pilha - YouTube

I did it too with a small transformer and it even operates too meaning there is a lot options but fallow mister Carlos suggestions 🙂

Regards
Juan
 
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#183
ohooo I see mister Terry the idea of the regulator is to keep a constant and steady power a reservoir when power is need it, I was checking a few minutes ago and the power consumption playing soft music is about 327mA (330mA) on the positive rail the regulator should be just right.

Regards
Juan
 
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#184
Juan Vargas new email adress is

juanvargasdiaz1970@yahoo.com

In this year, when Juanito born, i was already in the army.

Young Juanito.

Carlos
 

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#187
Hi Guys,

I have been using my DX Supply with an SKA GB150. I am using a 40-0-40VAC transformer and dialing it down to +/-50vDC rails. It is feeding both channels which are set to 250mA per rail each. I had fairly large heatsinks installed on the supply but they never even got warm to the touch. I wanted to reduce the size to make it easier to install in the case I am building for the SKA so I remove the heatsinks and just cut some pieces of 1/4" x 2-1/2" x 6" aluminum bar and attached them to the MJL21193(PNP) MJL21194(NPN) outputs. They still barely get warm to the touch even after prolonged playing. So I am curious, what does it take for the outputs to need large heatsinking, Class A?

Thanks, Terry
 
#190
I'm suggesting you play a sinewave through the amplifier connected to the power supply to generate sufficient current draw through the pass transistors in your power supply. If you are playing music at normal levels through a medium power Class A/B amplifier, and the quiescent current in the normal range, then the average power draw is going to be low. If you want to see the pass transistors' heatsinks get hot to confirm proper operation, then play the music really really loud or drive the current into a dummy load.
 
#191
OK, I see what you are saying. I guess that was my point. I did play the amp really loud for and extended period of time to make sure the bars(heatsinks) would be sufficient. The heatsinks on the SKA were plenty hot but the heatsinks on the PSU were barely warm. I was just wondering because I saw some pictures of some pretty big heatsinks on these PSU's and wondered if any of them got hot and if so, what amp were they driving. Mine doesn't even breaks a sweat.

Thanks, Terry
 
#192
That low heat dissipation implies low Vdrop through the regulators when delivering 250mA of Iq.
Normal music playing does not increase the average current draw that much.

But the low Vdrop could be a problem.

What is the regulator Vdrop when mains is at maximum tolerance?
What is the regulator Vdrop when mains is at minimum tolerance?

If the Vdrop is high the regulator will run hotter.
If the Vdrop is low then the regulator will drop out. That is what you must check.
 
#193
AndrewT said:
That low heat dissipation implies low Vdrop through the regulators when delivering 250mA of Iq.
Normal music playing does not increase the average current draw that much.

But the low Vdrop could be a problem.

What is the regulator Vdrop when mains is at maximum tolerance?
What is the regulator Vdrop when mains is at minimum tolerance?

If the Vdrop is high the regulator will run hotter.
If the Vdrop is low then the regulator will drop out. That is what you must check.
Click to expand...

Hi Andrew,

Not sure what you are referring to with Vdrop. It is a 40-0-40vAC transformer. With just normal bridge and filter it produces around +/-58vDC. I have the DX supply adjusted down to +/-50vDC for the SKA. It holds right there seemingly regardless of what level the amp is playing at. Almost not voltage change at all.

Thanks, Terry
 
#194
58V supply and 50Vdc output tells you that the Vdrop across the regulator is 8Volts.
That voltage varies. It varies a lot.
As your current draw changes the Vdrop changes.
As your mains supply voltage changes the Vdrop changes.
You need to know that the regulator never falls out of regulation.
You do this either by modeling or by measurement.
Find out how low the Vdrop becomes in worst case operation.
Find out how high the Vdrop becomes for worst case regulator heat creation.
 
#195
Maximum current info is needed to see if the Dx Supply

Will be good to do this job....it was made to 4 to 5 volts of voltage drop (voltage in the colector minus voltage in the emitter....or input voltage minus output voltage)... was made to the Dx Amplifier,

Of course other amplifier can use it, but we must check if the supply can face the power or not..and this depends on the current and voltage drop.

This voltage drop is multiplied by the maximum current..then we gonna have the power ...and this must be checked to know if the supply will hold the job without fail...transistors have maximum current, maximum voltage and as a result maximum power, and this must be checked.

Power into the series pass transistors, to each rail, is the rail current multiplied by that particular rail voltage drop.

You said 58 will go in and 50 will be the the adjusted voltage...so...we have 8 to multiply by the maximum current the SKA will drain from the suipply (full power at 2 ohms current)..... then we gonna see if your transistors (type and quantity) will be enough.

In the reality, dear Terry, this calculation is for "worst case scenario", because real world the input voltage (58 volts) will drop depending the current drained)...so...we have a safe margin after the calculation based in 58 volts.

regards,

Carlos
 
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#196
I played it for two days straight and nothing got even warm in the PSU. I have increased the voltage to +/-52V because that is what Greg Ball suggested. I don't hear any difference. I'm not going to take a chance and play the amp into 2ohm at full volume. It handles 4ohm just fine.
 
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