Clon C-3850

Regarding AC transformers: Bought two from a U.S. vendor in Florida. Wired one up to power the clone and it sounded fine.
Received an email from the vendor today that the labels for the line voltage leads 110 vs. 220 to the primary might be incorrect. Yep.
And like the novice I am, I did not check with the meter because the clone still sounded fine at just a few volts supply!
Did not seem to damage anything on the board...
 
I don't believe in wonders...you can use every good supply with LM317/337. I can show 3 supplys i have tested with my phono preamps. There was no difference. Not what i expected...
LM regulators have the better ripple performance as constant regulators, thats the fact. Big capacitors in the regulator input making "wonders"...
The C3850 has a poor power regulation. To make something better its helpful to choose a board with LM regulators ore someting else.
Series regulation with TL431 will work to.
There is a reason why the C3850 Board is cheap....7 USD...😉
Now we are trying to build a Ferrari from VW base...🙂

Greets
Peter
 

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I finally put one together. Ha. This goes in the queue with a bunch of other stuff so I will follow up later.
Some transistors face 'the other way'. ebc vs cbe is all, do not fret.
Cheers.
 

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hi stoxx
cool heat sinks. where you get these?

regulator
you know that every kind of cap will help to get the ripple noise/voltage less and less but as Peter wrote. its a cheap PCB.

as you can see in the schematic. there are no implementations to reduce the noise from the rails to IPS, VAS or OPS. e.g. a smal resistor is the easierst way to reduce ripple voltage but you loos a bit of voltage for drive the stages.
RC network or cap multiplier are other soutions like a small coil -- see HPA noir

C3850 schematic 2.jpg



noir PSU
1738651480240.png



kr
chris
 
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a smal resistor is the easierst way
Yes, indeed. I mentioned this here before. The LM7815 & LM7915 are of no interest to me on this circuit board. I suggested a simple CRC filter on board. We have the two capacitors and where the regulator was, we can add a 10 ohm resistor(or inductor) where the regulator was supposed to be. It will have to dissipate a solid watt of heat in my setup, so I was thinking about precision power resistors. I have a good selection of external power supply boards I can use. I can decide later. For testing I will use +/- bench supply.
 

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With an RC low pass filter, you get a filter slope of -20dB/decade. With a 10 ohm resistor, you could have -20dB ripple rejection with a single 1500uF cap (Fc of 10.6 Hz). An extra 1500uF cap gets you -40dB. With a single, cheap LM7815/7915 you get -60dB ripple rejection at 120Hz, and you get voltage regulation.
 
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I have used industrial SMPS (48V 2000W PFC) with Icepower 200AC modules. The 48V noise was not a problem, but the +12V/-12V driver supply needs to be quiet. That particular supply has quoted "Ripple & noise < 150 mVPP , 30 MHz bandwidth / < 2 mVRMS psophometric".
 
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