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Old 24th November 2011, 03:41 AM   #131
tomchr is offline tomchr  United States
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Quote:
Originally Posted by SpreadSpectrum View Post
The DAP will be new to me. I'm looking forward to learning something new with this.
It's not rocket surgery. It does test your soldering equipment, though. Must .... have .... thermal .... mass....

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By the way, I got my boards today. If only my digi-key order were anywhere close to me right now...
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Boards are in as well. Look forward to populating over the next few weeks.
Nice! Yeah, I noticed all US shipments except one were delivered today (11/23). Let me know how assembly and test goes.

I should also note that due to the general craziness of Christmas/Festivus/"The Holidays"/Winter Solstice I will ship the last order of 2011 on Tuesday December 13. Any orders placed after that date will ship in early January. Just keep this in mind in case you want Santa to bring you boards for Christmas. I'll be around and follow DIY Audio, though.

~Tom
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Last edited by tomchr; 24th November 2011 at 03:43 AM.
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Old 28th November 2011, 04:00 PM   #132
tomchr is offline tomchr  United States
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So far I've tested 5.0 V @ 1.5 A; 6.3 V @ 1.2 A; 7.5 V @ 1.25 A; and 7.5 V @ 2.5 A using the values in the Known Good BOM spreadsheet. The output voltages come in within 1~2 % of the target value, which is about as good as one can ask for. The output impedance looks good and indicates better loop stability than I was seeing with my setup a few months ago due to better choices of output capacitors. I still need to look at the transient response, though.

I'll post pictures when I have a little more data together.

~Tom
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Old 28th November 2011, 08:31 PM   #133
TheGimp is offline TheGimp  United States
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I'm waiting on parts to build a 2.1V regulator for use with 4P1L. Using 2.1V and driving both ends of the filament with the center tap common will reduce the voltage delta across the entire filament. This may or may not have any bearing on actual performance of the 4P1L.
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Old 28th November 2011, 08:50 PM   #134
mogliaa is offline mogliaa  United Kingdom
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Originally Posted by TheGimp View Post
I'm waiting on parts to build a 2.1V regulator for use with 4P1L. Using 2.1V and driving both ends of the filament with the center tap common will reduce the voltage delta across the entire filament. This may or may not have any bearing on actual performance of the 4P1L.
It has lower distortion. See my post re 4P1L line stage....
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Old 29th November 2011, 03:25 AM   #135
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That was my impression from reading "The Thermionic Vacuum Tube". I'll go back and review your 4P1L Line Stage.
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Old 29th November 2011, 07:23 AM   #136
tomchr is offline tomchr  United States
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It actually does make sense that the distortion should be lower if the filaments are in parallel. See Wavebourn's comments in the 4P1L line stage thread.

I'll add 2.1 V to the list.

~Tom
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Old 29th November 2011, 07:31 AM   #137
mogliaa is offline mogliaa  United Kingdom
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Hi Tom,
I should try the 2.1V, however I need to run it a lower filament current to minimise distortion and microphonic feedback. Can you adjust the current manually in your regulator?
Thanks,
Ale
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Old 29th November 2011, 01:19 PM   #138
TheGimp is offline TheGimp  United States
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Ale, the only way to lower the current is to lower the voltage set point. It can be adjusted by changing either of two resistors in the feedback divider.
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Old 29th November 2011, 01:46 PM   #139
iko is offline iko  Canada
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Ale, this is not a current limiter like Rod's design. This is a real voltage regulator.
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Old 29th November 2011, 04:51 PM   #140
tomchr is offline tomchr  United States
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Originally Posted by mogliaa View Post
I should try the 2.1V, however I need to run it a lower filament current to minimise distortion and microphonic feedback. Can you adjust the current manually in your regulator?
The filament obeys Ohm's law regardless of what voltage/current source is connected. So if you want lower current in the filament, just lower the output voltage of the regulator. If you want the current to be 10 % lower, make the output voltage 10 % lower. As others have pointed out already, this can be done by changing R1, R2.

The output impedance of this regulator is very close to zero Ohm. In other words it's about as close to an ideal voltage source as you can get. I'll post plots of Zout over the weekend.

~Tom
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