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In Reply to: RE: FWIW posted by Ralph on February 20, 2014 at 09:03:26
"So, if we used batteries instead, would there be coupling caps?"
Maybe the term "coupling" is in any case not the best one to describe the role of a PS capacitor, since "coupling capacitor" carries the connotation of a capacitor between one stage of amplification and the next. The PS capacitor is in the audio path, and to that extent it has features in common with a coupling capacitor.
If batteries are used instead, then we now have the audio signal passing through them. Presumably if the batteries are essentially "ideal" (maybe like a set of car batteries in series?), they will have extremely low impedance and there will be no significant interference with the audio signal. However, given the way that passions are aroused by discussions of the pros and cons of different capacitor types, I could easily imagine analogous debates over batteries, whether Sears is better than Pep-Boys, etc., etc.!!!
I see Lew's point about whether the cathode bypass capacitors would negate the benefits of putting in cathode resistors for current-balancing purposes. My suspicion would be that any resulting unbalance for the AC audio currents would be a relatively minor issue, and the main concern is to ensure some degree of stability and balance of the quiescent DC currents through the tubes, which can be quite large and dissipate a significant amount of power. I know from my own experience that if one isn't careful, then with paralleled output tubes it can be possible for one of them to hog most of the current, and hence dissipate a lot more power than the others.
Chris
Follow Ups:
ChrisMr.Karsten says to you : "So, if we used batteries instead, would there be coupling caps?"
And you responded to him that you have responded , but I ask you now : What`s happen with car ( lead acid ) batteries when they during exploatation become discharged ? .
I think than they need some battery Charger to again become Charged !,( and usually simple battery charger consist from one main trans. and SS rectifier ).Any way I want to tell you next , only by using just my simple as possible sentence & words without Any intention to discredite you or anything simmilar !!! :
Batteries are just DC E.energy power Source Storage Units , same as Elko`s in convetional Amp PSU , further stored E.energy from batteries are partialy wasted (discharged) in power tubes , generating un-usefull heat, and finally some of that stored DC E.enegry is discharged on the load(speaker) , converting that stored E.energy in sound , also in un-usefull heat too , that generated sound is only Usefull Work that we actally need .
And yes ! all of this 3 device (charged battery , power tube ,load(speaker )are connected in series !
Finally I want to say that any serious E.Engineer look in this way how that E.machine (Amp)work , audophiles and amateurs don`t , they use term`s something like : audio-path , audio that or this , and so on and so forth , bla , bla , bla .....Best Regards !
__
Enlightened Evolution-Astral Projection
Edits: 02/20/14
"And you responded to him that you have responded , but I ask you now : What`s happen with car ( lead acid ) batteries when they during exploatation become discharged ? ...."
I'm not sure I'm catching the point you are making, but it seems anyway we are in agreement that the power supply (battery in this case) is in series with the speaker and tubes. The AC audio current that passes through the loudspeaker passes also through the battery. If you want to call that the "audio path" or not is just a matter of preference for words, but the facts are presumably not in dispute.
Chris
Chris
If we connect that same Amp ( basically one black box who amplify something ) which we usualy use in home for reproducing of music signal on the load of table shaker , which is usual tool in airplane industry , and excite that Amp with different input signal in range from 20Hz - 20Khz , same as is in audible freq. range , can we say that inside of PSU`s Elko`s pass some table shaker signal ? , I think no !
__
Enlightened Evolution-Astral Projection
"If we connect that same Amp ( basically one black box who amplify something ) which we usualy use in home for reproducing of music signal on the load of table shaker , which is usual tool in airplane industry , and excite that Amp with different input signal in range from 20Hz - 20Khz , same as is in audible freq. range , can we say that inside of PSU`s Elko`s pass some table shaker signal ? , I think no !"Banat, now I'm really puzzled where this discussion is going! I can't see that there is any new logical issue that arises for shaker tables that is in any way dfferent from the situation with loudspeakers and audio signals. They are exactly equivalent, as far as the point under discussion is concerned. It makes me suspect that the argument is more about peoples' preferred set of words to describe the same unambiguous and undisputed set of facts.
But just in case, let me pose three questions that have yes/no answers to you:
1) Would you say the shaker table signal is passing through the wires from the amplifier to the shaker table?
2) Would you say the shaker table signal is passing through the output tubes in the amplifier?
3) Would you say the shaker table signal is passing through the power supplies in the amplifier?
Chris
Edits: 02/20/14
ChrisI see no point to respond you on that 3 question !, only by giving yes or no answer , since I have allready to much clear&loud responses here , I don`t want to open new marathon of questions & answers , and it is little beat to late hours by me here on this side of planet Earth .
Best Regards !
__
Enlightened Evolution-Astral Projection
Edits: 02/20/14
nt
Maybe the term "coupling" is in any case not the best one to describe the role of a PS capacitor, since "coupling capacitor" carries the connotation of a capacitor between one stage of amplification and the next. The PS capacitor is in the audio path, and to that extent it has features in common with a coupling capacitor.
That's always been my opinion.
With regards to Banat's circuit (seems I saw that proposed on DIYAudio a few years back) it might be a good idea to use resistors that are more like 100 ohms. That would make the caps smaller and the bias would not be self bias as it would still need some bias voltage, but not nearly so much. :) Each approach has its own set of problems...
because, as you say, that would reduce the required size of the bypass capacitor. I calculated in my head that to achieve a -3 db point at 2Hz with a 30-ohm cathode resistor (so response would be flat at 20Hz), I'd need ~3000uF bypass caps. I'm sure one can get by well with a higher -3db point, however.
With my amps, that's a lot of new parts to buy and install (3 cathodes times 4 tubes per monoblock), if I were to do it. 24 new resistors and bypass capacitors, in total.
If you install such cathode resistors, you will want to increase the power supply voltage accordingly.
just after posting. 100R per cathode would drop around 13V per cathode, if I bias the whole 7241 at around 400mA, which is typical. Thankfully there is no real need to go that high in resistance.
Chris thanks............i can see with the 4ea 6C33 OTL..an the need for them to be fused....that 4 more caps may be the way to go...ezey to pull
if one feels there a down side....sound wise..i would think these should also have a smaller .1mf cap ...Ah...yes the never ending story of the OTL...an the ESL...
So it gos........
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