“Your signal has already seen more capacitors than you will find in the mouser catalog”
Again why throw the Baby out with the Bath Water. Just because there are things in the Recording Path that we have no control over is absolutely no reason not to strive to reproduce all those inaccuracies as accurate as possible. This is why Audiophile Recordings are so prized by there owners. Or if we assume the agreement in the above quote to be valid then I asks why is such a person seeking High Fidelity anyway when just about any Audio system with enough power to obtain the required Loudness will do. Also why would someone with the view in the quote care about the quality of their capacitors since the recording Equipment more than likely used an Electrolytic type.
kwhead > “Actually, Douglas Self has demonstrated (as in actually measured) that the cap commonly placed at the bottom of the feedback chain can be one of the most significant contributors of distortion in an otherwise well designed amp.”
Again more supporting evidence supporting a complete DC coupled Signal path both in the Primary and feedback Paths and yes I also think the cap used from the Inverting input of the Input stage Diff amp to ground or in the feedback loop dose degrade the sound as much as a coupling cap would however this is more often than not the result of using a large value Low voltage Electrolytic in this Location. I have seen caps as High as 3000uf at 6.3 volts used hear such a cap will have so long a time constant that if used with an Input coupling capacitor will have a negative effect upon the group delay of the system. When considering a Design you must take into account the entire system not just one part of it, otherwise you will not see the Light at the End of the Tunnel.
Again there are things outside of our control, However why settle for further compromise with things that we can control.
“Pick high quality caps that do the job. If you can eliminate one without doing something stupid then do so. Don't invest in capacitors sprinkled with magic pixie dust. DC coupling maybe nice, but a driver slightly DC biased will most likely have more problems than would be caused by one good capacitor removing the bias. Those are my design criteria (not that anyone else cares ).
"Ppl, since you DO have an all in one system, there is no need for a cap in signal path . But I do want them in my speaker amp - they'd be dead already had I not have one as occasionally in my experimenting DC can come through. The amp also seems to have an overcurrent protection as a few times relays clicked and disconnected the speakers for few seconds due to inrush of current (e.g. big turn-on thump on a connected source)."
I have used an ALL DC coupled Path on My Loudspeaker Amps and not one Time have I ever have a driver fail in over 15 years of use because of DC, however I do make darn sure that no DC is present on any source I connect to this and all of my Audio systems since now all are DC coupled from the DAC and I have one real Nice Mag Phone Preamp that also is DC coupled and has only 0.1mV of DC on the output. Also I power up the power amp last.
Regarding your DAC yes this was my Primary Reason for adding your DAC to my portable PPA was to assure a pure DC coupled Path both primary and secondary feedback path the only cap is the Bass Boost and that can be turned off however. Thanks for the reminder to replace the socket on the Board since it is now a lose fit with most Brown Dog adaptors and the DAC is mounted upside down I should do that soon as my CD3K I am sure would protest if that op amp fell out !OUCH!
JohnFerrier>”Prune,
Circlotron's concatenated IC op-amp test certainly is interesting; however, he will not be someone that claims to have golden ears as he has posted that his hearing rolls off at <10khz…”
“aos,
Anyone breadboarding circuitry can use the cheapest voltmeter to check for DC offset. I’ve tossed any DC offset adjustment in my discrete circuit because with careful selection, I’ve got the output offset to <1mV.”
“As far as capacitors, I’m putting all 20 square inches of polypropylene capacitors into the power supply…four 9V alkaline batteries. As far as capacitance in the signal path, I’m living with parasitics and about 200pF of active device capacitance.”
Ah a breath of fresh air and finally some real logic applied to the subject we should give John the Audiophile Nobel Prize”
aos “I do check for DC before plugging stuff in, but as I mentioned connections can get loose on an experimental unit as you keep plugging and unplugging and if you do this often, sooner or later you will have an incident. E.g. just keep rolling op amps and you'll have a case where one of your soic to dip adapter pins will fall out or lose contact - that can be all it takes. It may be once every 2 years but I don't plan on re-purchasing my Studio S100's every 2 years”
I use mill-max sockets and the IC will only come out with lots of force and half the time the IC is ruined after extraction. So don’t use the same sockets you wore out from op amp rolling. I have a 90% confidence level that my IC’s are going to stay put for as long as I leave them installed, by using fresh Mill-Max Machined Pin IC Sockets, because I do not plan on replacing my CD3K or any other headphone for that matter in 2 years.
John> “hehehe...rolling op-amps...when I'm finished, the only thing I'm rolling is CDs...they roll better than op-amps ; ).”
Me also that sounds like a lot more fun
Ricker>” and again , all studio mic preamps have capacitor coupling as do digital effects and ADC inputs,all equalizers including digital domain EQs , mixing console ,monitor amps,the monitors themselves unless a single full range driver is used ,etc.
As for feedback path vs. signal path caps-i never said they were equal just that they are there and have an effect regardless of how much.
not that it really matters.the final mix is EQ'ed to obtain the "house sound" anyway so the inherent phase shifts of a frequency modification circuit are there”
I am in total agreement so why would you want to alter what is on the recording with additional phase shift and response deviations
Pink Floyd> “Hold on guys...... as interesting as this is I was trying to find out which type of cap sounded best to your ears. ie: I think polypropelyne caps sound best overall but they inject a rubbery, bouncy signature into the sound etc etc etc. Polyester sounds more natural though it has a tendancy to reveal a lot more information whether good or bad etc. etc etc.........
That type of thing is what I was looking for. I'd even appreciate comments like " polypropelyne sounds like freshly mown grass with a hint of wild nettles allowing the capacitor to inject an undercurrent of newly laid tarmac which underpins the proceedings and makes the music sound so quintessentially Pimms and lemon.”
Ok the reason I ststed none was because you don’t get more perfect than reality so you can add whatever audiophile vernacular to describe the sound of perfection any way you wish so if one were to AC couple my choice if price and size were no object
Polystyrene Film/Foil= sharp detailed transients low time smear and the Closest thing to a wire you can get however Large value versions are hard to come by and costly.
Teflon Film/foil= almost as good as above but somewhat fuller mid-bass for the same value
Polypropylene Film/Foil = Use where cost and or size are as important as sound quality
Avoid any Metalised film cap these sound Tizzy and blur the sound
