In the meantime, while I'm "getting all learned up"... and for my own sanity; The original confusion was created by the following recommendation:
"4.7µF WIMA 5,10,12.5,15 22.5,25MM LS 35-50v POLY"
From what I think I understand now,
1) "Poly" is referring to PP... not PET, PEN, PPS, or PTFE. Is that correct?
2) 35-50V was the suggested for safe AC input, per your previous calculations and not the storage capacity (which beyond the input is just showing off🙂 )
"4.7µF WIMA 5,10,12.5,15 22.5,25MM LS 35-50v POLY"
From what I think I understand now,
1) "Poly" is referring to PP... not PET, PEN, PPS, or PTFE. Is that correct?
2) 35-50V was the suggested for safe AC input, per your previous calculations and not the storage capacity (which beyond the input is just showing off🙂 )
poly could stand for plastic, any plastic.
polystyrene, polyethylene, polytherephthalate, polysulphone, polycarbonate, there's hundreds of plastics with chains of molecules.
polystyrene, polyethylene, polytherephthalate, polysulphone, polycarbonate, there's hundreds of plastics with chains of molecules.
AndrewT:
I believe I am probably misunderstanding something. If you aren't completely frustrated with my questions yet, I could use a little more of your help 🙂
Could you give an example of F-3dB. While I understand the concept, I can't seem to find a good mathematical example to help clarify this, and I am a very visual person. I cant recall the dB to Freq. relationship.
All OK so far 🙂
Or... Does this suggest that using electrolytic is in fact OK in this situation?
I am sorry for all the questions, I know that it takes a lot of your time to answer questions like mine, and I am sure I speak for everyone when I say how grateful we are to have people like yourself involved in these forums. Thank you.
I believe I am probably misunderstanding something. If you aren't completely frustrated with my questions yet, I could use a little more of your help 🙂
Answer: I don't believe so. I think that my speakers aren't capable of 2hz 🙂 20hz is the lower limit
Could you give an example of F-3dB. While I understand the concept, I can't seem to find a good mathematical example to help clarify this, and I am a very visual person. I cant recall the dB to Freq. relationship.
All OK so far 🙂
Here is where I am a little confused. This C1 Capacitor has a coupling function, but also a High pass filter function. So does this mean that the above ideas for using electrolytic, etc is to be disregarded in this case?
Or... Does this suggest that using electrolytic is in fact OK in this situation?
I am sorry for all the questions, I know that it takes a lot of your time to answer questions like mine, and I am sure I speak for everyone when I say how grateful we are to have people like yourself involved in these forums. Thank you.
Another Question for anyone who has time/ knowledge to answer 🙂 :
When selecting Q1/Q2, Is there a point where too much gain would be harder to work with (sensitive to adjustment through R7) or is it pretty much bigger is better mentality. I believe this was kind of answered before; but I'm just trying to imagine a gain of 100 vs a gain of 1000 being trimmed by the same R. thinking they would be reacting significantly different.
Sometimes my curiosity gets the better of me 😛 . I would experiment if I had an electronics supplier anywhere near. Unfortunately this Province doesn't have any hobby suppliers for this type of project!
When selecting Q1/Q2, Is there a point where too much gain would be harder to work with (sensitive to adjustment through R7) or is it pretty much bigger is better mentality. I believe this was kind of answered before; but I'm just trying to imagine a gain of 100 vs a gain of 1000 being trimmed by the same R. thinking they would be reacting significantly different.
Sometimes my curiosity gets the better of me 😛 . I would experiment if I had an electronics supplier anywhere near. Unfortunately this Province doesn't have any hobby suppliers for this type of project!
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If you are looking for transformer have a look to these ...
Addison electronic montreal canada
stock # 151116 & # 151117 .... great deal ..
Addison electronic montreal canada
stock # 151116 & # 151117 .... great deal ..
if your audio signal is 20Hz to 20kHz then adding a filter for bandpass that is one decade outside that should allow all the audio to pass, i.e set the bandpass to 2Hz to 200kHz.
The low pass is the RF filter and will have an F-3dB of ~200kHz. This operates as a filter above 200kHz, but has an effect down to ~ 20kHz, @ ~100kHz is is 1dB down in response.
The same applies to the high pass. Set it to F-3dB @ 2Hz, it has an effect upto ~20Hz and is down by ~1dB @ 4Hz (a common specification you see in many commercial domestic duty amplifiers). In the audio band neither of these filters has much if any effect. The high pass is a coupling capacitor in the audio band. Distortion only becomes measureable if there is some audio signal across it.
Below 4Hz it has significant signal voltage across it, it is a filter at these lower frequencies. But fortunately we can't hear distortion of 2Hz, the harmonics are below audio range right up to the 9th and by the 9th the distortion component of 2Hz is going to be so low it cannot be measured.
A single pole passive filter has it's turn over frequency defined by F-3dB = 1 / {2 Pi R C}
if you want 2Hz then the formula is re-arranged to become:
RC= 1 /{2 Pi Frequency} = 1/2/3.14/2 = 0.0796seconds,
i.e set the RC of a passive single pole filter to 79.6ms.
RC is the multiplicand of the R value and the C value. It is evaluated in seconds of time constant.
Any combination of R & C can be used to arrive at RC=80ms
eg. 80k & 1uF, or 100r & 80µF
Precision is not important for this single pole filter. It is one decade below your wanted audio siganl, it could vary by +-1%, or +-30%
I hope the above answers this. It is a coupling capacitor for the audio band and a filter capacitor for signals below 4Hz.
and a BIG electrolytic does pass audio signals well, if it is well manufacturered and well looked after. D.Self was the first that I saw to explain this way back in the 1990s and it is still being misunderstood/misapplied. Don't let it run hot, cool is better than warm and reform it slowly to full rated voltage before you use it.
If you have a high input impedance, then a small value of coupling capacitor can be used to set F-3dB to 2Hz, A plastic film cap can be used when Rin/Zin is > 20k
But for high values of coupling capacitor, an electrolytic must be used to save space, weight and money.
Here I have experimented with back to back 10uF+10uF and 22uF+22uF and cannot tell the difference to 4u7F and 10uF
I have also tried paralleled series electrolytics, 4 off 10uF in series parallel with one series pair connected back to back and the other series pair connected front to front. Again this 4 cap combination seems to me to perform as well as a 10uF FKP (enormous and expensive).
I cannot recall anyone posting an objective report on a series parallel electrolytic comparison to MKP, MKS, FKP, FKS
the current gain does not affect the voltage gain nor the voltage sensitivity.
Current gain determines the base current (Ib) that needs to flow for a particular Ie (emitter current)
Ib defines the amplifier's "input offset current" and when multiplied by the input grounding resistor determines the "input offset voltage".
High hFE gives low input offsets. The extreme case is to use a zero gate current jFET for the input LTP. The input offset voltage can be zero volts if the devices operate at Idss, or can be low mV of offset when Id is slightly less than Idss. Many run their input jFET LTP at ~90% of Idss. This gives very low input offset voltage. BJT are extremely difficult to get that low. Some expensive opamps use laser trimming and other cancellation techniques to approach jFET input offsets.
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Thanks. Unfortunately I already paid for my XFMR. I hear that Primrose makes A+ audiophile quality Transformers though, so I'm trying to focus on that silver lining vs. the savings 🙂 . I`ll keep Addison in mind in the future.
As you've illustrated(quite well), the distortion caused in this application would be perfectly acceptable in the 4Hz range as it is non-audible. which would allow for use of the Wima capacitor mentioned earlier.
As a follow up; I converted RC=1/[2 PiF] into [1/RC]/[2 Pi] = F , and applied it to C1 (4.7uF: .0000047F) & R2 (820R). I believe this was the correct process, as it resulted in approximatly 80mS. WHen I try to convert 80mS to Hz, I get F = 19.89, leading me to believe that I derrived someting wrong, OR should be using a different resistance. I'm assuming the badger is designed with all of this in mind, and thought out already. I'm sure I am making the mistake. 😕
Sometimes I wish I had of chosen to go EE instead of Avionics, it is more inline with my hobbies 😛 .
Thanks again. I'll go for the larger gain units. I had the concept backwards(and wrong 😛 )
This is a valid observation! 😛 lol
I used to get excited watching Aircraft flying around. Now it turns my stomach!
4.7uF = 4.7*10^-6F
RC = 4.7*10^-6F * 820ohms = 3.8ms, not 80ms
But where did 820r come from? That is not the high pass filter resistance/impedance.
That is more like the RF filter.
Honestly, I think I confused myself. 820 was the value of R2. I am not sure of the value to use for the high pass filter resistance/ impedance. Although this circuit is probably very basic to most people here, I don't usually work with these types of circuits. I usually work with systems drawings, interconnect schematics, etc. Definitely a weak area for me.
When I hear High pass filter, I think of a capacitor passing the high freq. while a inductor carries the lower freq. elsewhere (or to return).
Very basic example: (imagine the inductor is AFTER the cap... Txt reflows online? Fixed I think...)
PHP:
Cap
+o------||--|-------------SPK +
|
B (inductor)
|
|
-0------------------------- SPK -
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OK. Fair enough. Is there an obvious R value to make up the R portion of the input filter we are discussing? Or is it more complicated given the rest of the circuit?
R2 & C2 make up the RF (low pass filter).
C1 & R3 make up the high pass filter and AC coupling/DC blocking.
C1 & R3 make up the high pass filter and AC coupling/DC blocking.
Thanks Andrew! I know it would have been way easier to just solder it all together, but this way I will have a much deeper understanding of the circuit. 🙂 I'll try to redo the math when I have a spare minute or two!
Well, Looks like I need to re-learn circuit theory. I worked out 1.02 Hz for the High pass cut off (which would kind of make sense), but I also worked out 718 KHz for the Low pass cut off. I feel like perhaps doing the F=1/([2Pi][RC]) is too simple for the amount of things going on in the diagram?
I am absolutely amazed at how little I remember about this, LOL.
My guess is that R1- R6, C3, C4, D1 - D2 all need to be factored in. Probably R49 (and the rest of the output end as well) ?
I am absolutely amazed at how little I remember about this, LOL.
My guess is that R1- R6, C3, C4, D1 - D2 all need to be factored in. Probably R49 (and the rest of the output end as well) ?
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Some use >1MHz and there are others that use the variable input capacitance of the transistor as their RF filter.
100kHz to 300kHz seems to be where most set their RF filter. Today's interference riddled homes NEED RF filtering on the leads of all audio equipment.
That includes mains and speakers and signal inputs
Capital K is Kelvin.
k is the kilo multiplier (10^3)
Thanks for the info!
I have been using K Instead of k since college. My teacher would take marks away all the time for it, lol. 😀 bad habits die hard...