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Old 20th November 2006, 05:47 PM   #11
phn is offline phn  Sweden
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No, I use RCA connectors. "Minus" leads and ground leads (there are two; seven leads in total including shield) are grounded.

I could lift the ground. But see no use for it since there are RCA inputs on my amp.
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Old 25th November 2006, 10:14 AM   #12
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The original question was about a coupling capacitor between a pre-amplifier and I presume, a power amplifier (not stated). For a meaningful calculation one needs the output impedance of the pre-amp as well as the input impedance of the power amplifier. These values are mostly specified.

Our good friend AndrewT did an excellent analysis of the basics. But with a -3 dB cut-off at 7,1 Hz, the effect at 70 Hz will be -0,86 dB. Still audible??

Anyway, any coupling time constant below 5Hz should suffice. Phn, you also do not need expensive mica capacitors. A lot has been said about magic capacitor effects (none quantative); it has been shown that poly-ester is perfectly capable of fitting the bill.

You could also certainly use the capacitor after the R (just make sure that that R is not shunting any d.c. to common without a blocking capacitor.) The blocking capacitor will then just form a high-pass network with the power amplifier input impedance. AndrewT gave this as some 22K; I would hope that it is rather higher, but do not have much experience of commercial equipment.

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Old 25th November 2006, 11:30 AM   #13
phn is offline phn  Sweden
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Johan, thanks for the reply. I still don't quite get it. But I'm not forcing it. If I knew why a 600Ohm load is more difficult to drive than a 10k load I might have been closer to the answer. I will get there, eventually.

Yeah, I was being stupid. I wanted to avoid starting a new thread and ended up more or less ruining this one for everybody by going OT. I will have to start a new thread anyway. I want to have the PlayStation up and running. Another lesson learned.

As for micas. I won't spend money on boutique caps. I don't consider micas boutique caps. And they can be found at reasonable prices. They may cost 2-3 times as much as poly caps. But since we talk low-value caps and relatively small sums of money, it doesn't matter that much.
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Old 26th November 2006, 06:20 PM   #14
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Quote:
Originally posted by phn
Johan, thanks for the reply. I still don't quite get it. But I'm not forcing it. If I knew why a 600Ohm load is more difficult to drive than a 10k load I might have been closer to the answer. I will get there, eventually.
Hi.Untill now, i understood that you want to replace the capacitor and resistor of the output of you PS with a transformer.The cap is there not to pass the DC component of the signal.Am i already familiar with the circuit?
If you want to use transformer instead of the cap and resistor, first of all you must know the potential of the DC you want to get rid of.This is important, becouse the transformer can carry specific max value of DC passing across the primary winding.After that value, the transformer will reach its maximum limits and start to act like a crazy - get warmer and so on...
That value depends on the type of the transformer's `iron`and the air gap between the windings and the `iron`.
The reason why a smaller load is more difficult to drive is because the current passing through the 600ohms load is a lot more that through the 10k's.The current, supplied by the unit before the load - let name it Current1, has it's maximum,and you must try to keep the value of the current passing through the load lower that that of Current1.Using a smaller load lowers the value of the DF(Demphing Factor) - not good for the sound.The DF is the result of this:
Rload divided by Ro.Rload is the resistance of the load,Ro - the output resistance of the unit before the load.
Hope my post was usefull to you.
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Old 26th November 2006, 09:55 PM   #15
phn is offline phn  Sweden
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Freestyler, thanks. The Demphing Factor is new to me. I don't think I'm able to apply it in this case.

Being stuck with these "non-working" trafos for a month, I finally started a new thread today. Now I have two threads on basically the same subject.

My current trafos are clearly not up to the job. From what I understand I need something in the line of SE interstage or output trafos, except with 600:600 or so Ohms. They will need to be big and expensive. They will most likely be too big to be mounted on the PlayStation. That sucks. But at least I know why the current ones don't work. That's a step forward. Now I need to ditch the line trafos.
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Old 27th November 2006, 12:15 AM   #16
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Quote:
Originally posted by phn
Freestyler, thanks. The Demphing Factor is new to me. I don't think I'm able to apply it in this case.

Being stuck with these "non-working" trafos for a month, I finally started a new thread today. Now I have two threads on basically the same subject.

My current trafos are clearly not up to the job. From what I understand I need something in the line of SE interstage or output trafos, except with 600:600 or so Ohms. They will need to be big and expensive. They will most likely be too big to be mounted on the PlayStation. That sucks. But at least I know why the current ones don't work. That's a step forward. Now I need to ditch the line trafos.
Excuse my mistake - it is Damping in English,we spell it demphing in Bulgarian
Yes - the trafs you have now maybe aren't suitable for the aplication.I don't know your PS's size - I never had such a thing(computers,computers) If I was you - a would prefer better capacitors (AgTa) - it is a PlayStation at all - far away from a CD Player, and calculationg a transformer is not an easy deal.But you can also try out your first idea(trafos) - it will take you a lot more time, but the result may be better!
Good luck with the project
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Old 27th November 2006, 04:10 PM   #17
phn is offline phn  Sweden
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Quote:
Originally posted by FreestylerBG

Excuse my mistake - it is Damping in English,we spell it demphing in Bulgarian
"Demphing" did throw me. But I got a couple hits when I googled, including this: "The hypotesa of the demphing of the instability and the building of the stationary periodical gratings of the refractive-index is suggested." Who am I to argue with Harvard?
http://adsabs.harvard.edu/abs/1998SPIE.3485..440B
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Old 27th November 2006, 05:14 PM   #18
Nordic is offline Nordic  South Africa
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To use ohms law to illustrate... imagine your amp needed a 1V input to reach full volume.

In fact imagine you have 2 of those amps.

One with an input impendance of 600R, and one with 10K

To put 1V over 600R it would need 1V at 0.0017A
To put 1V over 10K would need only 1V at 0.0001A This amp would be a much "easier" load on a preamp or any preceding device in the signal chain.
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Old 27th November 2006, 06:02 PM   #19
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Quote:
Originally posted by phn
"The hypotesa of the demphing of the instability and the building of the stationary periodical gratings of the refractive-index is suggested."

W H A T ! ! ! ! ?

Electronics are not quite so difficult. Take courage, Phn; one gets there with much less difficulty than one imagines. Ask me.

Regards!
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Old 27th November 2006, 08:22 PM   #20
phn is offline phn  Sweden
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Nordic, thanks. I figured it was straight math/physics. I sort of had it figured before (more current goes to ground or something such with a small load), though I had no hard figures. Working in Spice has taught me quite a bit, while at the same time preventing me from learning the fundamental stuff.

Johan, I know electronics is simple, as simple as math. I personally think it's hard. But that has to do with me and not electronics.
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