Electrolytics can be surprising.
I bought my McIntosh MC240 in 1978, used. Look how the original 'lytics in the voltage doubler fare 40 years later, especially the dissipation factors. I have some current F&T replacements ready to be fitted, but when I look at the specs, I'm hesitant. Would you replace them?
I bought my McIntosh MC240 in 1978, used. Look how the original 'lytics in the voltage doubler fare 40 years later, especially the dissipation factors. I have some current F&T replacements ready to be fitted, but when I look at the specs, I'm hesitant. Would you replace them?
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You aren't driving a 1978 car though. And if you were would you complain if you'd needed an engine rebuild? Expecting a domestic amplifier to last as long as Voyager 1 and 2 is a little odd.
If they measure right or you can't hear any hum or anything wrong because of them , I wouldn't do it.
Unfortunately in the audio world there are many funny stories about cap's replacement, where new audiophile caps just screw the sound of some 40 years old equipment....
Yes. Of course (OMHO). Soon or late.
Did-it to renew my first commercial amp 'baby', designed and produced around 1970 and ... still working. More or less ;-)
As the modern electrolitics are smaller than the old ones, for the big caps in the power supply, I had emptied their cans, put the new ones in the old cans, and reassembled the whole, to keep the "vintage" original look.
For the little ones on the boards, just replaced with new good ones.
I replaced the potentiometers and all the old carbon film resistances by metal film ones. The sound has totally changed, surprised how good it is, now.
May-be my son will do the next cap change after my death ? ;-)
Btw: The power amp was one rail, regulated power supply, pseudo complementary output stage, Current-feedback like (but too high value for the feedback resistance).
Kept like it was: We have to assume our mistakes and laziness.
A proof that 'CFA' is an old classical topology which preceded LTP.
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You might probably know that sometimes cleaning the noise in a system leave some empty space for other system's problem to be heard like weird oscillations or distortions that looked like they were never there before...
Training ones ears to dislike equipment/sound that was once acceptable is to join the ranks of the sad audiophiles and their never ending journey, for which, there is no medication to reverse the sickness.
much cheaper pill though and you save more for the trips in nature, concerts and live performance with your wife, kids or girlfriend too...Unfortunately most of the electronics engineers i know had very bad tastes in women so they missed both pills...
I do not worried about oscillations: Mr Nyquist was yet a (bad) friend*. As it was an industrial product, we took good stability margins.
We were quite proud to be able to display those performances:
Power: 2X50W.RMS
Distortion <0.1% (in real <0.05%)
bandwidth: 25Hz to 32KHz.
In fact, distortion was (and still after restauration): <0.05%
At this time (1973) how many commercial amps were able to show better ? Mc Intosh, for 4X the price ?
* Can be often seen in company of Mr. Murphy.
Sorry, you don't get my point, or rather, Bruno's.
Specs are how the design object is supposed to be performing. By positing it should be current feedback, you are excluding possible solutions that might be better than CF from the outset. A true engineers nightmare.
🙂
Well...I think Bill mentioned his own "look in the bin" stories , so we can pretend that we swallowed it, just spit it out as quick as possible and never mention the red pill when having sex.
About capacitors in the signal line:
ALL high end DAC chips from ess and akm use coupling caps between DAC and amplification stage. The latest generations claim sub -126 dB distortion . You cannot listen to any high end DAC without the signal through an electrolyte. And in the case of current output DAC, that electrolyte has to do some real work because as seen from the DAC it is effectively grounded on the other end.
So, what harm could a capacitor do if only pushing against a much larger resistor as in an input stage. None, nada, niente, niks.
So you are completely right, use a cap if it makes sense (but don't interpret this as agreement with your covariance idea or brand attachment, equally nonsensical as an abhorrence of caps in the signal line IMO.)
The best rejoinder on caps I ever heard was from Nelson Pass. I paraphrase:-
'so you're worried about capacitor coupling? Get over it'
I don't understand your point.
I believe Richard is experienced enough to know what and why he is doing.
On my side, I would not pretend to give him any lesson. We just exchange our experiences, tricks and point of view. (That are often very close.)
If for any reason, and you have no informations at all about them, he decided to go in a direction or an other, the only thing you can think is: "Appointment in the listening room" on his JBL M2.
On my own, I decided to use a Class D for my sub, a class AB VFA for the stereo bass-medium, and a CFA for my horns. For more than only one reason, like looking blind at distortion numbers that are overkill for the 3. May-be something you dislike, according to your own personal preferences ?
About Bruno, i think he is one of the best engineer in this domain.
His Class D amps are among, if not THE best class D amps on the market. As well as his SMPS.
Not at all the best amp you could find, in full range, when you compare with some more classical others.
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Come on Vacuphile. This is audio - not some industrial, medical or telecoms application that may need some serious tradeoffs or performance must have's.
In this game its more important to specialize in a particular topology, refine it over time and become expert in using it.
The fact is some folks like VFA and some CFA . . . leave it at that.
🙂
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Mark, you are right, one should not bus through Indochina and post on a mobile after having a beer or two.I was generalizing from a AK4490 board I worked on.
Can't link, but if you look at the AKM datasheet, figure 41, that is a recommended circuit.
Mark, you are right, one should not bus through Indochina and post on a mobile after having a beer or two.I was generalizing from a AK4490 board I worked on.
Can't link, but if you look at the AKM datasheet, figure 41, that is a recommended circuit.
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