Please show me a design that demonstrates your ideal, and explain why it works as it does to negate the sound of components. Just by calling people incompetent to design amplifiers is putting yourself up as an authority, and I would like to see some demonstration of that. Otherwise, you are just being an *** calling everyone stupid.
Remember, we are all supposed to be having fun at this hobby, and your denegration of the attempts of hobbyists to learn, experiment and improve throws a bucket of cold water on everyone pursuing this. If you have insight on how to design circuits better, then please share.
Mind you, I personally try to design to get capacitors and out of circuits where possible, but it is challenging to design anything where you do not have components that influence the sound in the signal loop.
Whether or not you "buy it," it is still true. If you hear differences between two capacitors, and you can verify that you really are hearing those differences, the design is failing the basic test of what a hifi (as opposed to MI) amplifier is supposed to do- make a small electrical signal larger.
By changing the "make" of capacitor perhaps not. Heavy on the perhaps. By changing the "type" of capacitor in some instances/locations 100% absolutely you can tell.
From my experience anyhow.
It seems to me that what you are describing is that you are masking all components contibutions with the feedback you are choosing. If thats how you like thing that fine - others have entirely different milage.
There is only the engineering ideal of wire with gain in your head - as far as I am concerned it has never been demonstrated in any commerically available product. I live in the real world of imperfection where choices make a difference to the end result.
Shoog
I am talking about hifi amplifiers, and I believe we have an issue between "real-world" rather than "ideal" performance. You can still have "hifi" even with less than ideal performance, really depends whether it does the music service.
For me, it is about the sound, not some test against an ideal.
I am not calling anyone stupid. The Chinese who sell lots of poorly designed and implemented tube power amps to the west are certainly not stupid.
You only have to look at the posts on this site to see a very wide range of designs by people with an equally wide range of skills . It is not surprising there are a lot of designs that don't perform well. Even if the design is a good one, you can tell from the number of posts about getting rid of hum loops that the basics are grounding are little understood and with power amps the implementation is as important as the circuit itself. These people are not stupid they just don't know better.
Stop putting words into my mouth. I think hobbyists should learn from experiment but it is all to easy to jump to erroneous conclusions. Just because capacitor A sounds better in a circuit than capacitor B does not mean one is better than the other except in that particular implementation of that particular circuit.
Cheers
Ian
Where did I talk about feedback? Try engaging what I say rather than what the voices in your head are saying.
If it's a hifi amp, it has no "sound." If it has a "sound," it's an effects box, and if it's intended to be a hifi amp, the design is incompetent.
Interesting discussion, thanks for all the info and opinions everyone.
The amp isn't mine, I'm helping a friend replace a couple buldged/leaking caps, etc in an old console amp. I don't have the R value on hand at the moment or remember the brand/model of the amp to find a schematic (he found and printed one off), but I will look into the formulas mentioned and do some other reading on that subject. However, he liked the way it sounded before the caps started failing, so we will probably just replace like with like.
As for the discussion of good and bad designs, this transitions perfectly into some other questions I have, as I want to build my own tube amp this summer. I'm going start a new thread stating my requirements and to discuss the designs I've looked at and take suggestions on ones I haven't encountered yet.
Thanks again!
The amp isn't mine, I'm helping a friend replace a couple buldged/leaking caps, etc in an old console amp. I don't have the R value on hand at the moment or remember the brand/model of the amp to find a schematic (he found and printed one off), but I will look into the formulas mentioned and do some other reading on that subject. However, he liked the way it sounded before the caps started failing, so we will probably just replace like with like.
As for the discussion of good and bad designs, this transitions perfectly into some other questions I have, as I want to build my own tube amp this summer. I'm going start a new thread stating my requirements and to discuss the designs I've looked at and take suggestions on ones I haven't encountered yet.
Thanks again!
My question stands. What is the design methodology you use or can suggest to eliminate the influence of component sound (keeping capacitors as an example) in a "well designed" circuit. Let's not talk about poor construction issues (i.e., grounding, etc.) or highly cost constrained and poorly implemented commercial or diy designs. How do you avoid capacitors or any other complex non-linear devices (inductors, transformer, amplifying devices (tubes, transistors), etc.) from influncing the sound by design? Obviously use of direct coupling, differential circuits, etc. do alot. However at some point you have to provide protection against DC, either internally or at the output, and we are talking a capacitor, a transformer (we are talking tube amplifiers), or tight balancing/cancellation (i.e. servo or tight power supply regulation). Of course part of a good design is to protect against component failure.
My experience and the experience of others I know is that capacitor sound is real in high performance circuits. As are tubes, transformers, regulators (shunt & series), regulator error amplifiers (such as op-amps), CCS's etc. None of these items are ideal components.
My experience and the experience of others I know is that capacitor sound is real in high performance circuits. As are tubes, transformers, regulators (shunt & series), regulator error amplifiers (such as op-amps), CCS's etc. None of these items are ideal components.
I don't need to, others have already done it. Check out the excellent work done by Doug Self.
Cheers
Ian
Let me understand this. You are saying that I need to minimize signal voltage (which when you say signal voltage, I understand it to be AC not DC) across the capacitor.
Lets' talk about coupling capacitors, since it is the simplest example.
The signal voltage that the coupling capacitor sees is simply the input AC voltage multiplied by the amplification factor of the amplifying circuit. This a basic engineering, and unavoidable if you need the signal to be amplified. For one to reduce the signal voltage across the capacitor in this case, you would need to reduce the amplification.
Obviously, an circuit that doesn't amplify doesn't have a sound (now I understand! ;^>).
Seriously, a capacitor is an electrostatic device, it depends on charge attraction of electrons across the dielectric and does not allow direct electron flow (i.e., blocks DC) The higher the AC voltage (or potential), the more electrons are attracted and repulsed as modulated by the AC signal. First, you need to have enough electrons in action for fidelity of the signal to be transfered. Of course we are probably talking about a massive amount of electrons and not just one or two. Second, it is intellectual concievable that due to a massive amount of electrons in motion, you start having a point where electrons are interferring with each other as they are attracted/repelled, and therefore the impressed signal on the output plate is no longer the same and the input. However, considering the plate area involved (and compared with small area of a wire) I find this hard to believe, but not denying the potential effect.
I would postulate that there may be more of a issue with too little signal voltage, if there are any hysterisis effects across a capacitor. For instance, it is often desireable to have a DC bias (especially for electroytic capacitors)
This is a very esoteric case that is not what I consider "basic engineering". Basic engineering is keeping within the AC and DC rating of the capacitor in the circuit design. Is this what you meant?
Lets' talk about coupling capacitors, since it is the simplest example.
The signal voltage that the coupling capacitor sees is simply the input AC voltage multiplied by the amplification factor of the amplifying circuit. This a basic engineering, and unavoidable if you need the signal to be amplified. For one to reduce the signal voltage across the capacitor in this case, you would need to reduce the amplification.
Obviously, an circuit that doesn't amplify doesn't have a sound (now I understand! ;^>).
Seriously, a capacitor is an electrostatic device, it depends on charge attraction of electrons across the dielectric and does not allow direct electron flow (i.e., blocks DC) The higher the AC voltage (or potential), the more electrons are attracted and repulsed as modulated by the AC signal. First, you need to have enough electrons in action for fidelity of the signal to be transfered. Of course we are probably talking about a massive amount of electrons and not just one or two. Second, it is intellectual concievable that due to a massive amount of electrons in motion, you start having a point where electrons are interferring with each other as they are attracted/repelled, and therefore the impressed signal on the output plate is no longer the same and the input. However, considering the plate area involved (and compared with small area of a wire) I find this hard to believe, but not denying the potential effect.
I would postulate that there may be more of a issue with too little signal voltage, if there are any hysterisis effects across a capacitor. For instance, it is often desireable to have a DC bias (especially for electroytic capacitors)
This is a very esoteric case that is not what I consider "basic engineering". Basic engineering is keeping within the AC and DC rating of the capacitor in the circuit design. Is this what you meant?
Right there is where you go wrong, so nothing past that is correct, either. Draw the equivalent circuits of one amplifying stage RC coupled to another, then calculate the transfer functions. Note that the AC voltage across the cap is proportional to Xc/(R + Xc). Now, what are the ways to minimize that quantity?
Engineering. Very basic engineering. It's not hard, but you gotta do it.
Polyester. Known to be a slightly non-linear dielectric, so need to ensure no signal voltage across them (except in guitar amps and old radios, where a little extra distortion is either required or unimportant).Shoog said:
What do you mean by 'high performance circuits'? I would assume that 'capacitor sound' is a symptom of a low performance circuit.dmcgown said:
I always try to use reasonable quality capacitors in my designs, common electrolytics and industrial grade MKPs, eg Epcos (Former Siemens), so far never found audible differences.
When I use an electrolytic bypassing cathode resistor, I always put a MKP of three orders of magnitude lower in parallel, I never hear them.
Two possibilities
a) My designs are good.
b) My ear is not even good enough to ring the bell.
When I use an electrolytic bypassing cathode resistor, I always put a MKP of three orders of magnitude lower in parallel, I never hear them.
Two possibilities
a) My designs are good.
b) My ear is not even good enough to ring the bell.
Both of which mean a very small ac voltage across the capacitor. Which is the whole point - coupling and decoupling capacitors should be as near a short circuit as possible at the frequencies of interest, else they don't do the job they are supposed to do, and if they are near short circuits there can be very little voltage across them and they make no difference to the signal and hence the sound.
Cheers
Ian
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