Hi everyone,
I have read a good deal of this thread, but I confess not all of it, so if these questions are answered above, my apologies. (I tried a search...)
I want to build p2p versions of the regulator circuits in posts #11 and #12 to test a version of the symmetric B1 using BF862 jfets. Since these have lower max voltage than 2SK170 I need +/- 9V output. (I should add, this buffer is up and running with a simple 7809/7909 regulator. The point is to build this more sophisticated reg to compare...)
I have two (basic) questions.
1. The schematics show an input of +/-17VDC. There is no mention of pre-regulation, so am I correct in supposing that this could be the output from a 12 - ct - 12 transformer, rectified and with say a pair of 2200uF caps smoothing it? By my mathematics this is just a little short of +/- 17 VDC...
2. If I want +/- 9 VDC output instead of +/- 10, can I do this by adjusting the strings of LEDs to give a different reference voltage? It seems to me this should be possible, but I can't see how to make the numbers work...
Thanks for any help
Cheers
Nigel
I have read a good deal of this thread, but I confess not all of it, so if these questions are answered above, my apologies. (I tried a search...)
I want to build p2p versions of the regulator circuits in posts #11 and #12 to test a version of the symmetric B1 using BF862 jfets. Since these have lower max voltage than 2SK170 I need +/- 9V output. (I should add, this buffer is up and running with a simple 7809/7909 regulator. The point is to build this more sophisticated reg to compare...)
I have two (basic) questions.
1. The schematics show an input of +/-17VDC. There is no mention of pre-regulation, so am I correct in supposing that this could be the output from a 12 - ct - 12 transformer, rectified and with say a pair of 2200uF caps smoothing it? By my mathematics this is just a little short of +/- 17 VDC...
2. If I want +/- 9 VDC output instead of +/- 10, can I do this by adjusting the strings of LEDs to give a different reference voltage? It seems to me this should be possible, but I can't see how to make the numbers work...
Thanks for any help
Cheers
Nigel
1. Usually transformers output more than nominal with this small load (usually also in spec like +12% or something like that), so I got nearly 14 volts from transformer and 19 volts as DC.
2. Make the 5 leads string one volt less, that should give 9 volts out.
OK, thanks. So output voltage is the total drop along the 5 led string, plus Vbe on Q3?
Cheers
Nigel
Yep. You already use a current mirror version in your racing green vault lock pot pre, yes?
Yes, but I'm still trying to understand how these circuits work. I am learning a little electronics theory bit-by-bit as I build stuff. (With a lot of help from you guys...
) I got into this hobby by accident, really, I only meant to build a LM3876 chipamp because I had no working stereo, and here I am a couple of years later with an ever-increasing pile of electronics and parts, and my wife is starting to question my sanity... Cheers
Nigel
Sub your Zener in that greenie with a couple of leds and a little resistor to equal 3V9 Z and ear a better resolution, before the wifey catch us then...
Only in the negative supply, correct? The +ve supply presumably has too big a Vref for this to be worthwhile?
Little resistor is in series, I imagine, is the value to be calculated depending on the voltage drops across the leds?
Cheers
Nigel
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On the plus side you can sub with just resistors. Worthwhile too. I have mentioned in that BF thread. Its the running current times the resistance that will work as a ref. Maybe find on a trimmer first and then sub. Because the negative is more critical better the main part be leds, its practical because it takes just 2. But you can find some reds or greens that will Vf at 1.95V so no little added resistor at all even.
Supply Rail Voltages
What supply rail voltages are everyone using?
I was wondering if anyone has experimented with the supply voltages and what
their opinions were.
I have a B1 circuit with adjustable positive and negative regulated supplies and
did some experimenting with each supply rail while watching the distortion on
a spectrum analyzer. I found that the best possible results come from a
supply with +9v and -9.75v. The 2nd harmonic is cut in half by this configuration.
All other harmonics (only 2nd, 3rd and 4th generated by the B1) are pretty much
the same. The FETs are matched at 10.6 mA.
I have no idea how this sounds though because I don't have all the bits put together yet
What supply rail voltages are everyone using?
I was wondering if anyone has experimented with the supply voltages and what
their opinions were.
I have a B1 circuit with adjustable positive and negative regulated supplies and
did some experimenting with each supply rail while watching the distortion on
a spectrum analyzer. I found that the best possible results come from a
supply with +9v and -9.75v. The 2nd harmonic is cut in half by this configuration.
All other harmonics (only 2nd, 3rd and 4th generated by the B1) are pretty much
the same. The FETs are matched at 10.6 mA.
I have no idea how this sounds though because I don't have all the bits put together yet
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Maybe this
VPT12-2080 Triad Magnetics Transformers
But unsure about VCCS requirements and you have to rectify then regulate to get your 5V.
For this price you could buy 2 transformers from Antek, but being in a different country maybe I wont be much help sourcing.
Uriah
VPT12-2080 Triad Magnetics Transformers
But unsure about VCCS requirements and you have to rectify then regulate to get your 5V.
For this price you could buy 2 transformers from Antek, but being in a different country maybe I wont be much help sourcing.
Uriah