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Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.

Another can of worms...
Another can of worms...
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Old 10th May 2018, 01:09 AM   #1
troystg is offline troystg  United States
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Default Another can of worms...

I am assembling some analog active crossovers and I would like some suggestions on capacitor and resistor types.

What does everyone like?

Now what do you like that I can afford?

Part of the BOM that was generated is below.

Part Value Device Package Description
B1 2KBP 2KBP RECTIFIER
C1 .01uF TH-NPC050-075X040 C050-075X040 Through-Hole Capacitor
R1 POT-1/4P POT-1/4P
R2 1M TH5MM 0204/5
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Old 14th May 2018, 02:09 PM   #2
johnego is offline johnego  Indonesia
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Originally Posted by troystg View Post
Now what do you like that I can afford?
What!!? You don't need big oil can, socket, Allen-Bradley and the like. You need accuracy (parts tolerance, TC), low noise parts and less parasitic capacitance. Try high end SMD parts
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Old 14th May 2018, 02:54 PM   #3
abraxalito is offline abraxalito  United Kingdom
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Build your AXO with JFET input opamps (TL074 works a treat and is dirt-cheap). This allows you to use the cheapest NP0 capacitors (values under 1nF, typically) in conjunction with high value resistors (100k and up).
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Old 14th May 2018, 05:26 PM   #4
AuroraB is offline AuroraB  Norway
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Seriously no reason for looking "HiEnd" components.....mostly BS anyway- but do not use ceramic capacitors for X-over.... normal polyprop like Wima or the likes... should be around 25c in 25-batch...
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Old 14th May 2018, 05:48 PM   #5
Fast Eddie D is offline Fast Eddie D  United States
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Through Hole Resistors | Resistors | DigiKey
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Old 14th May 2018, 05:52 PM   #6
Fast Eddie D is offline Fast Eddie D  United States
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Design your filters so you use the same value resistor as much as possible. Then buy 10 lots and save a little money.

CMF5010K000FHEB Vishay Dale | Resistors | DigiKey
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Old 16th May 2018, 01:29 PM   #7
Kay Pirinha is online now Kay Pirinha  Germany
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Quote:
Originally Posted by Fast Eddie D View Post
Design your filters so you use the same value resistor as much as possible. Then buy 10 lots and save a little money.

CMF5010K000FHEB Vishay Dale | Resistors | DigiKey

I'd prefer replacing 'resistor' by 'capacitor', because resistors usually are much cheaper than capacitors.


Best regards!
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Old 16th May 2018, 04:12 PM   #8
johnego is offline johnego  Indonesia
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Originally Posted by abraxalito View Post
Build your AXO with JFET input opamps (TL074 works a treat and is dirt-cheap). This allows you to use the cheapest NP0 capacitors (values under 1nF, typically) in conjunction with high value resistors (100k and up).
I prefer to avoid lower capacitor value such as below 1nF. The effect with HF is not good. With lower C, the accuracy may suffer due to parasitic capacitance of the PCB. With lower C the R then need to be higher. This may increase noise, react with parasitic capacitance, introduce phase shift, lower the bandwidth, and so on.
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Old 16th May 2018, 06:09 PM   #9
Fast Eddie D is offline Fast Eddie D  United States
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Originally Posted by Kay Pirinha View Post
I'd prefer replacing 'resistor' by 'capacitor', because resistors usually are much cheaper than capacitors.


Best regards!
True, but the filters use way more resistors than capacitors. Plus, the capacitors make a way bigger difference , although there are a lot that will work very well. MKP types are great.

I've used different kinds of film caps. I like polypropylene and MKP. I've used caps I took out of nice equipment from the 80s/90s; I don't know what they are but they work great and I have a lot of them. Differences are subtle to non existent. I make other people listen too for what it's worth, and solicit their opinion.

I prefer to build with new parts. I do buy some film caps x10 but I still go through a lot more resistors. A typical circuit will need 2x the same value cap two different values, and 8x the same value resistor two different values.
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Old 18th May 2018, 10:47 AM   #10
johnego is offline johnego  Indonesia
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Originally Posted by Fast Eddie D View Post
Design your filters so you use the same value resistor as much as possible. Then buy 10 lots and save a little money.

There is a thread regarding (What do you think about) Passive Crossover. Those who have the skill for passive design might have issues with rolling active crossovers (Me included).


So, for me, TL074 is a waste of time. True, it is cheap, but who's looking for cheap sound


And the resistors, the values are all over the place because the circuitry is designed to match the opamp being used. Many good opamps are actually unique, meaning that for acceptable result they cannot be used in conventional circuit (where people can do an op-amp rolling)
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