Um what do you mean here? Coupling the output of an amplifier to an 8Ω speaker with a 4.7µF capacitor will sound horrible and tinny. You seem to be talking about amplifier output coupling capacitors and crossover networks all in one sentence.To decouple the DC - a GREAT IDEA I may ad, you just use a large capacitor because it cannot pass the class A DC bias than is common on power amps and some op amps operate in class A mode. To couple with a capacitor in audio usually means just using a low value like 4.7uf because at somewhere between 3000 and 5000 hertz it will have an 8 ohm capacitive reactance and since that matches the speaker it will optimize power transfer.
Well, I did it anyway, just for fun:You don't need to measure the distortion of capacitors. It has already been done and documented
Umm, that's not what the data I posted suggests at all. Adding a 9V DC bias to the tantalum cap reduced the distortion it generated which is to be expected. But in either case, the tantalum had more distortion than the metal film cap.I'll keep this short and just say putting 9 volts DC into a tantalum cap and claiming it has higher distortion does not even begin to convince me that electrolytics - even so called audio or np or bipolar ones, are even close to tantalums for superior design and innovation opportunities in audio.
I think most will agree with you that tube amps have more distortion than modern solidstate amps. It's just that some people like tube amp distortion. I'm not one of them.SSman said:Then there is the whole tube thing that is still popular in spite of my web page rant and rave about that particular shortcoming as well as high end or headroom losses and the limitiing of innovation that they introduce.
Surely you mean DC....SSman said:Any capacitor blocks AC unless we are talking very small values
1µF at 160Hz is 1kΩ which is larger than 600Ω, therefore the capacitor will have a higher voltage across it than the resistor and contribute to more distortion than it would at higher frequencies or if it were larger.Well, I did it anyway, just for fun:
I used a HP8903B audio analyzer and connected a single pole passive RC highpass filter on the output of the audio generator running at 5Vrms @ 160Hz. R was 600Ω, C was 1µF and the distortion analyzer was connected across the resistor.
You are correct. I generated 5Vrms output and then adjusted the frequency until 2.5Vrms was measured across the 600Ω resistor. Should have used 3.5Vrms for the -3db power point.1µF at 160Hz is 1kΩ which is larger than 600Ω, therefore the capacitor will have a higher voltage across it than the resistor and contribute to more distortion than it would at higher frequencies or if it were larger.
Yes, but SSMan was talking about filters and crossover networks. I think.Hero999 said:Oversizing the capacitor would reduce the distortion even further.
I can't. But once you use a bunch of crappy caps in a multipole filter I might. I certainly wouldn't use ceramic or tantalum caps in an equalizer.By the way can you even hear 0.016% distortion?
I won't argue that point. Once the coupling cap is over sized, to say a 1Hz -3db highpass, then distortion becomes negligible in the 20Hz-20Khz audioband.We could use a much larger 10µF capacitor which would have negligible distortion and would be smaller and cheaper than the 1µF film capacitor.
True but if the capacitors are oversized by a factor of no more than about 10 for 20Hz, they should charge quickly enough to prevent that from being a problem.A larger capacitor value might take too long to charge and you would hear severe distortion until it is charged. You also might hear severe distortion for a while after the power is turned off.
I don't know about in the US but here in the UK, a 3.3:mu:F electrolytic costs half the price, is well under a quarter of the size and you probably won't be able to hear the difference.I use 330nF film capacitors for all my audio coupling capacitors with an input impedance that allows them to pass the entire audio bandwidth. They cost only 13 cents each American.
Anything to make more money from silly audiophiles who'll pay twice as much for half the distortion that they can't hear anyway.Manufacturers are still playing the "lowest distortion" game.
National Semi has their LM4562 dual opamp that has only 0.00003% distortion. It shows that the circuit was designed properly.
So using your logic you need 10:mu:F capacitor if you have two 10k stages, those 10:mu:F metal film capacitors are going to be pretty bulky and expensive.If you want to hear 20Hz at the same level that it was recorded at (if your speakers go that low) then you want a flat response at 20Hz and a -3dB frequency of 4Hz.
If there are two coupling capacitors then the -3dB frequency becomes -6dB so the -3dB frequency of each section should be 2Hz.
Why would you worry about distortion for frequencies below 20Hz?If you increase the value of a coupling capacitor because it is the distorting kind then its time constant becomes 0.4 second which is a noticeable charge-up time.
Two sections each would have a 0.8 second charge-up time
I agree, make the input impedance as high as possible but sometimes you don't have a choice.I don't use an input impedance as low as 10k ohms. I use 120k so that I can use a very good, small and inexpensive 330nF film input capacitor.
I think your reason for preferring the ceramic to the electrolytic is purely physiological. Somewhere you heard that electrolytic are worst than ceramics and believed it to be true so it's no surprise your experiment backs up this theory.
Tantalum capacitors in general ... demonstrate very stable performance over the DC voltage (bias) applied in an application. At the same time, the majority of capacitors utilizing ceramic or polymer dielectrics (monolithic ceramic, disc ceramic, MLCC, polyester, film, etc.) demonstrate significant shift in both directions - sometimes 40 % to 50 % or higher.
Capacitance change with d.c. voltage:
- Ceramic C0G or U2J: Not Significant
- Ceramic X7R or X5R: Significant – see individual part graph
- Ceramic Y5V: Very bad – do not use for a.c. coupling
- Tantalum Electrolytic: Not Significant
Standard aluminium [electrolytic] parts are much lower cost than tantalum, but are usually physically bigger. They offer good stability of capacitance with voltage and temperature and have similar ESR, so are recommended where there is enough space.
- Ceramic: Weakness: Large Voltage Coefficient (X7R, X5R, Y5V)
- Aluminum Electrolytic: Advantage: Stability: Voltage
- Tantalum Electrolytic: Advantage: Stability: Voltage & Temp
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?