It followed from the thought/promise/dream that you might pay us to start new threads with your trade mark as the title.Nuuk said:
Well if I made any money from DD, that may be a good idea! 🙄
For now I will just be happy if people read what is written there before building GCs! 😉
For now I will just be happy if people read what is written there before building GCs! 😉
Oh,
you've noticed that some can't or won't read advice either, particularly if they don't want to believe due pre-conceptions.
you've noticed that some can't or won't read advice either, particularly if they don't want to believe due pre-conceptions.
Update. Built both amps and a simple unregulated PS with bridge rectifiers and 20v secondary's (24 v after rectification). Very impressive.
Decided to tidy up the PS and having looked at what I had, decided that I could make the Snubberised PS. My God, Chip amp on steroids. If it was good before, then it is stonking now. It has only had about 6 hours on it so far. Each rail is now 30v. Hope that's not too much.
It is deathly quiet (with 97db Fostex 206E Back loaded horns) can't hear really that it is on even with my ear right up to the speaker.
I have got to say at present that it sounds better than the Chipamp kit......well at least equals it !
Once again thanks for everyone's help on here and yes, Nuuk you're right, read your site first, which of course I have done since, it's all there !
Decided to tidy up the PS and having looked at what I had, decided that I could make the Snubberised PS. My God, Chip amp on steroids. If it was good before, then it is stonking now. It has only had about 6 hours on it so far. Each rail is now 30v. Hope that's not too much.
It is deathly quiet (with 97db Fostex 206E Back loaded horns) can't hear really that it is on even with my ear right up to the speaker.
I have got to say at present that it sounds better than the Chipamp kit......well at least equals it !
Once again thanks for everyone's help on here and yes, Nuuk you're right, read your site first, which of course I have done since, it's all there !
Can you clarify the DC voltage on the supply rails?Puffin said:
I can't understand how adding snubbers to the PSU increases the voltage from 24Vdc to 30Vdc.
Could you post details of the interim and final arrangements?
BTW,
+-30Vdc is no problem, particularly so for sensitive speakers as you have connected.
It is OK for 6ohm impedance and higher.
Probably OK for 4 to 8ohm speakers if a big heatsink keeps it cool.
Similarly 4ohm speakers would do if kept cool. This being easier to do with high sensitivity speakers than with normal speaker efficiency.
I am getting 31v on the v+ and v- rails. I used this circuit attached, but left out one pair of 10,000uf caps as I only had one pair.
http://vikash.info/audio/p2plm3886/
http://vikash.info/audio/p2plm3886/
Puffin, you may have stumbled on hitherto unknown circuits! 😀
20 volt secondaries should give you 28 volt rails after the rectifier. And as Andrew says, the snubbers won't, or shouldn't, change the voltage! So where you are getting your 31 v from is a mystery to me. 😉
I tried the snubbers but didn't really like them. I only mention this because it is important to keep stressing that we need to try these things for ourselves, rather than have people lay down rules based on what they believe is 'right'! Good on you for experimenting! 😎
20 volt secondaries should give you 28 volt rails after the rectifier. And as Andrew says, the snubbers won't, or shouldn't, change the voltage! So where you are getting your 31 v from is a mystery to me. 😉
I tried the snubbers but didn't really like them. I only mention this because it is important to keep stressing that we need to try these things for ourselves, rather than have people lay down rules based on what they believe is 'right'! Good on you for experimenting! 😎
Nuuk. Wow, one step for man......etc
The total voltage is 63. something
I can say that this certainly beats the inital "crude" supply. I am only using proprietory bridge rectifiers (no MU860's). I read on one site that this particular guy's opinion was that the use of fancy diodes was a waste of money ?
The chipamp used 860's.
The total voltage is 63. something
I can say that this certainly beats the inital "crude" supply. I am only using proprietory bridge rectifiers (no MU860's). I read on one site that this particular guy's opinion was that the use of fancy diodes was a waste of money ?
The chipamp used 860's.
Have you got the message yet? That's just opinion and the only way to 'know' is to try! 😉
Now, are you saying that the voltage measured between positive rail and negative rail is 63 volts? If so please measure the voltage between positive and zero volts, and negative and zero volts.
Puffin, just a thought but when you measure the voltage after the rectifier bridge, is there any load connected? If not you won't be measuring the correct voltage!
It's been idling for the last 30 mins. Amp is on. Pos to Neg rail 60.8
Pos to 0v is 30.4 and Neg to 0v is 30.4
Pos to 0v is 30.4 and Neg to 0v is 30.4
I'd guess it's probably just a slightly higher mains voltage / mains fluctuation causing the slightly higher DC voltages. I don't think that's anything to be worrying about really?
What is the transformer spec?
115V:20+20Vac or 120:20+20Vac?
regulation=?
mains voltage at time of test?
Let's do the sums.
maximum output voltage from the transformer on no load=Mains voltage/rated input voltage *20Vac *[1+regulation]
if we substitute 117Vac as test day's voltage and 7% regulation then
secondary voltage =117/115*20*1.07=21.77Vac.
Peak voltage before the rectifier =sqrt(2) * 21.77=30.78Vpk.
Voltage after the rectifier ~30.78-0.5V (at zero curent)=30.28Vdc.
This is the peak voltage on the smoothing caps for all those assumptions made earlier.
Now connect the amplifier.
The diode drop will probably increase to about 0.6V to 0.65V when passing the quiescent load of the amplifier. In addition the ripple voltage on the capacitors will bring the measured voltage down by about 0.2V.
The quiescent voltage on the amp supply pins is now about 30.78-(0.6+0.2)=30Vdc.
as the load increases to typical average output powers, this voltage will fall by another 1V leaving the amp supply pins at about 29Vdc when delivering typical power. The voltage at the lowest point in the trough of the ripple could be another 0.5V below this measured value.
Now turn the amp up to full power.
The average value at the supply pins will probably drop to about 25V to 26V after the smoothing capacitors discharge to their new level. This voltage determines the maximum continuous power the amplifier can deliver.
From the earlier calculations it is very obvious that regulation and actual mains voltage have a dominating influence on the actual measured supply voltages.
But, I still cannot see how
115V:20+20Vac or 120:20+20Vac?
regulation=?
mains voltage at time of test?
Let's do the sums.
maximum output voltage from the transformer on no load=Mains voltage/rated input voltage *20Vac *[1+regulation]
if we substitute 117Vac as test day's voltage and 7% regulation then
secondary voltage =117/115*20*1.07=21.77Vac.
Peak voltage before the rectifier =sqrt(2) * 21.77=30.78Vpk.
Voltage after the rectifier ~30.78-0.5V (at zero curent)=30.28Vdc.
This is the peak voltage on the smoothing caps for all those assumptions made earlier.
Now connect the amplifier.
The diode drop will probably increase to about 0.6V to 0.65V when passing the quiescent load of the amplifier. In addition the ripple voltage on the capacitors will bring the measured voltage down by about 0.2V.
The quiescent voltage on the amp supply pins is now about 30.78-(0.6+0.2)=30Vdc.
as the load increases to typical average output powers, this voltage will fall by another 1V leaving the amp supply pins at about 29Vdc when delivering typical power. The voltage at the lowest point in the trough of the ripple could be another 0.5V below this measured value.
Now turn the amp up to full power.
The average value at the supply pins will probably drop to about 25V to 26V after the smoothing capacitors discharge to their new level. This voltage determines the maximum continuous power the amplifier can deliver.
From the earlier calculations it is very obvious that regulation and actual mains voltage have a dominating influence on the actual measured supply voltages.
But, I still cannot see how
could be measured, before the snubbers were fitted.
Andrew, rig up a PSU, 20 VAC traffo and bridge, and measure it with no load! I think you will see where the figure of 24v came from! 😉
You mean average AC level without any smoothing!
I wouldn't be daft enough to run an amplifier off that.
But maybe this was a voltage measured before connecting the amplifiers.
I wouldn't be daft enough to run an amplifier off that.
But maybe this was a voltage measured before connecting the amplifiers.
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