Before I begin, let me first say that I have searched the forums, passdiy and the net in general and nothing came up.
But my search criteria may have missed it, so I apologise in advance. I would appreciate it if you could tell me the correct search criteria.
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If you are using the power supply as designed by Mr . Pass, can please measure the voltage across the 1st cap on the power supply and let me know?
I am building the preamp using the same/similar board sold in the group buy. BUT I'll be using choke input instead of cap input (which is the default on the power supply) and choke input requires larger secondary.
Thank you for help
But my search criteria may have missed it, so I apologise in advance. I would appreciate it if you could tell me the correct search criteria.
========================
If you are using the power supply as designed by Mr . Pass, can please measure the voltage across the 1st cap on the power supply and let me know?
I am building the preamp using the same/similar board sold in the group buy. BUT I'll be using choke input instead of cap input (which is the default on the power supply) and choke input requires larger secondary.
Thank you for help
The voltage on C28 and C30 will be a little over 80V. I could point out that it's noted on the power supply schematic, but that would silly of me (please do your homework...please?) so let's do it the hard way.
It works like this:
The transformer is an Avel Lindberg D4007 (on the schematic as AL D4007)
A quick trip to the Avel Lindberg website shows that the secondary is 30-0-30V
Note that the two secondaries are in series, so that's 60Vac
A quick tickle of my calculator's tummy then tells me that 60V * 1.4 = 84Vdc
After subtracting diode losses and allowing for the fact that the transformer probably isn't going to deliver exactly 60Vac (due to variations in the line voltage and the manufacture of the transformer itself), it's just easier to say 'a little over 80V.'
The characteristics of the D4007's secondary are useless to you because you're going to have to use a different transformer--one with a higher secondary voltage--if you intend to use an LC filter.
It's not worth getting too worried about anyway. All you need to do is to make sure that you have sufficient voltage for the regulator to run efficiently (about 65Vdc minimum, but 70V would be better) and you'll do just fine.
Grey
It works like this:
The transformer is an Avel Lindberg D4007 (on the schematic as AL D4007)
A quick trip to the Avel Lindberg website shows that the secondary is 30-0-30V
Note that the two secondaries are in series, so that's 60Vac
A quick tickle of my calculator's tummy then tells me that 60V * 1.4 = 84Vdc
After subtracting diode losses and allowing for the fact that the transformer probably isn't going to deliver exactly 60Vac (due to variations in the line voltage and the manufacture of the transformer itself), it's just easier to say 'a little over 80V.'
The characteristics of the D4007's secondary are useless to you because you're going to have to use a different transformer--one with a higher secondary voltage--if you intend to use an LC filter.
It's not worth getting too worried about anyway. All you need to do is to make sure that you have sufficient voltage for the regulator to run efficiently (about 65Vdc minimum, but 70V would be better) and you'll do just fine.
Grey
Jarthel
I couldn't help but notice you have started a myriad threads with different questions about the 1.7. That most of your questions can be answered by either searching, looking at the schematics or with a basic electronics text is besides the point. What i really don't understand is why do you need a new thread for each tiny query that comes to your mind?
As these threads are not likely to benefit anyone else and only reduce the S/N ratio of the forum i can only hope a moderator will combine them into a single thread: "Jarthel fighting the Aleph"
I couldn't help but notice you have started a myriad threads with different questions about the 1.7. That most of your questions can be answered by either searching, looking at the schematics or with a basic electronics text is besides the point. What i really don't understand is why do you need a new thread for each tiny query that comes to your mind?
As these threads are not likely to benefit anyone else and only reduce the S/N ratio of the forum i can only hope a moderator will combine them into a single thread: "Jarthel fighting the Aleph"
analog_sa said:
Bookies stand ready to take your bets as to the winner.
I second the motion to combine the questions. Tidy this stuff up a bit. Granted it'll take time to track down all the threads, but it would cut through the clutter. Sadly, the problem is ongoing.
Gawd, I'm glad I'm not moderator anymore. Thankless task.
Grey
P.S.: Jeez, saw recently where almost 10% of people in some locale (don't remember where...England, maybe?) were willing to bet that the world would end by 2010 or so.
And you guys think I'm pessimistic?
I think the planet will make it. I'm not so sanguine about humanity's chances, though.
jarthel said:I know the math but obviously with only 2000uF as cap input, you won't get the full 1.414 factor. Hence the reason for this thread
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if you can't read, I will repeat it again. I have searched the forums, passdiy and the net and nothing came up.
The reason you couldn't find it by searching is because everyone else read the schematic (or did the calculations) and did not feel the need to start threads about it. The schematic says clearly that the raw DC is 80V, right up there at the top. Straight lines are wires, assumed to have zero resistance, and that line comes straight off C28 and C30. Thus the astute observer concludes that the voltage on the first bank of caps is also 80V.
One man's 'obvious' is another man's oblivious. The 1.414 ratio does not depend on the amount of capacitance. You can put a few pF across a bridge rectifier and it will charge to 1.414 times the RMS of the secondary, less diode losses. There is some tendency for the rail to draw down depending on the current draw of the circuit, but for a preamp you're not going to see much, if any, difference and this circuit is no exception. The circuit just doesn't take all that much current to do its thing.
Please do your homework. Simulations are not a substitute for thinking. Or even simple reading.
Grey
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