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Old 23rd June 2012, 12:10 PM   #1501
AndrewT is offline AndrewT  Scotland
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let's suppose the resistor sees a dynamic temperature change of 20C degrees due to varying signal.
The 5ppm resistor will have a dynamic change in resistance of 100ppm, the 50ppm resistor will have a dynamic change in resistance of 1000ppm or 0.1%

That change will result in possibly as much as 0.01% change in the output voltage if no other measures were in place to lower the impedance.

But compare the change in semiconductor parameters. They completely swamp these tiny resistor value changes.

If you now look at the ambient temperature changes in the PSU, you will find that the resistor change in resistance cannot be measured as a change in output voltage. It holds at it's new value. That new value might be 0.5% higher than when cold, or could be 0.005% higher than when cold. But you cannot measure that drift change because it is completely swamped by all the other changes in voltage. You cannot hear the drift change in resistor resistance for exactly the same reasons. 5ppm or 50ppm does not affect the sound at an amplifier fed with the regulator.
We hear AC we cannot hear DC.
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Old 23rd June 2012, 12:14 PM   #1502
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by merlin el mago View Post
I compared a trimmer vs a low ppm Vref resistor.

How do you say "Balderdash !!"
However if you use a 300ppm VR instead of Vref device then expect anything to happen to output voltage.
Understand how the regulator works and give it a chance to work properly.

The idea of using a VR as the sole device in the Vref string is defeating the whole SALAS reg philosophy.
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Old 23rd June 2012, 12:29 PM   #1503
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AndrewT I don't want to discuss with you I know we hear AC but don't forget all is DC powered.

I understand also semis have tempco & surely affects more to the reg.

I know Salas philosophy and I know LEDs are less noisy than resistors.

Still don't answered how do you say: "Balderdash"
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Old 24th June 2012, 12:18 AM   #1504
alazira is offline alazira  United States
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Quote:
Originally Posted by merlin el mago View Post
AndrewT I don't want to discuss with you I know we hear AC but don't forget all is DC powered.

I understand also semis have tempco & surely affects more to the reg.

I know Salas philosophy and I know LEDs are less noisy than resistors.

Still don't answered how do you say: "Balderdash"
"Balderdash" is just a colorful way of saying "Poppycock" , at least as far as low tempco resistors goes according to his analysis.
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Old 24th June 2012, 07:16 AM   #1505
AndrewT is offline AndrewT  Scotland
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In a regulator passing constant !!!
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Old 24th June 2012, 07:51 AM   #1506
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Originally Posted by merlin el mago View Post
You aren't alone: welcome to the "Golden Ears Club"
well I have an AXON 4,7 uF PP at output and clearly see his dark signature
that Is why ask

for me AXON Is not a option at all
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Old 24th June 2012, 08:29 AM   #1507
Swarky is offline Swarky  Spain
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Balderdash is a concise but polite and slightly old-fashioned way of saying "I´m sorry but my experience prevents me from agreeing with that. = pamplinas (con cariño).
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Old 24th June 2012, 02:10 PM   #1508
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Quote:
Originally Posted by alazira View Post
"Balderdash" is just a colorful way of saying "Poppycock" , at least as far as low tempco resistors goes according to his analysis.
Thanks

Quote:
Originally Posted by Swarky View Post
Balderdash is a concise but polite and slightly old-fashioned way of saying "I´m sorry but my experience prevents me from agreeing with that. = pamplinas (con cariño).
I think balderdash = tonterias
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Old 24th June 2012, 03:03 PM   #1509
Siberia is offline Siberia  Lithuania
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Default where's my voltage gone

Hello,

I'm building a two box Pearl II RIAA setup with SSLV1.1's. Tx, rectification bridges and first caps (4700uF) are in the PSU box. 0V lines are tied together when entering 3 wire umbilical. Shunts with additional 4700uF caps and RIAA boards are placed in the other.

At the entering of RIAA box I've got nice and steady 35.3VDC. Meanwhile after connecting SSLV with dummy load (600R) attached, I've got 30.5VDC on board smoothing cap and can't get my target 24V right.

I used two red leds, 1.8 kOhm for R303 and 5K trimmer for my Vref setting. With the trimmer at the max there's above 22Vout.

What might cause the lowdown? I've tried PSUD2 simulations and none of them confirm the actual voltage behaviour.

Thanks.
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Old 24th June 2012, 05:34 PM   #1510
Salas is offline Salas  Greece
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Normally the 35.3 to 30.5 should be bcs you CCS load your Tx and rectification stage.
Lets assume a 3mA (in circuit Id) mid way GR K117 in your Vref and 6.8K max resistance. That gives 6800*0.003=20.4V plus Vbe and Led(s). Looks normal. Boost your Vref. How high you wanna go? No more than 24-25Vo with your Vi I would suggest. Try 3K3 instead of 1K8 and see what happens.
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