Huh?
But there is no DC, input is 1V p-p digital signal? And 74HCU04 have no influence? What about 100R and 10K resistor? Are those values OK?
Last edited:
Sometimes you measure (or calculate) at AC, sometimes at DC.
This isn't the place for a lesson in basic circuit theory but...
At DC the DMM sees only the 75R. At AC you've got 2 low impedance components, the cap and the 100R and then you've got 10k||input impedance of 74HCU04 (which is pretty high, megohms) you can't see where this combination is terminated, but the resistance to ground is going to be at least ~10k. This is trivial (swamped) in comparison to 75R, so when you apply a DMM and measure the DC resistance you get a value which is trivially affected at AC.
w
Last edited:
uh oh ah 
and you asked for the HARD one
Please go read some basic lessons HERE before start pesting Joseph K and Jkeny again.
Yeah and here is real life TDR from schematic, post #174
One picture with 74HCU04 OFF and another picture with 74HCU04 ON
And input is real 75R ch. impedance with 4 m long cable
And I am not RF EE or any expert, just newbie trying to learn from experts like Joseph K, Jocko Homo & others.
and you asked for the HARD one Please go read some basic lessons HERE before start pesting Joseph K and Jkeny again.
Yeah and here is real life TDR from schematic, post #174
One picture with 74HCU04 OFF and another picture with 74HCU04 ON
And input is real 75R ch. impedance with 4 m long cable
And I am not RF EE or any expert, just newbie trying to learn from experts like Joseph K, Jocko Homo & others.
Attachments
Last edited:
to continue with this comedy.....
Jocko's formula:
100R + (RF/Aol+1)
100R + (10K/25+1)
100R + 401R
=501R (I am using Aol=25)
now we have 501R resistor parallel to 75R terminating resistor on input. Using this LINK, we put in first field 501R and in second field 75R and got 65.234R.
But DMM is showing us 75R
Very good stormsonic, you sucked me in good with that one, I was wrong in this case. I am not incapable of admitting when I have been wrong, or apologising, and I do apologise for my error in this case. I should have given more thought to my answer.
It does not, however, invalidate the majority of what I have said. This is one circuit in many, and not at all typical of the majority of application circuits in SPDIF receiver datasheets.
Now that we have got that out of the way I will continue 'pesting' Joseph K and jkeny.
When are they going to admit their errors? jkeny has explicitly denied that he presented his assertions as having general application. I quote from his first post:-
Joseph K presented his plots in support of jkenys assertion in full knowledge of the circumstances, and without any of the disavowals or later retractions that he has made that his results only applied to the Hiface equipment. In fact he explicitly excludes the Hiface.
I quote from his first post:-
w
It does not, however, invalidate the majority of what I have said. This is one circuit in many, and not at all typical of the majority of application circuits in SPDIF receiver datasheets.
Now that we have got that out of the way I will continue 'pesting' Joseph K and jkeny.
When are they going to admit their errors? jkeny has explicitly denied that he presented his assertions as having general application. I quote from his first post:-
Joseph K presented his plots in support of jkenys assertion in full knowledge of the circumstances, and without any of the disavowals or later retractions that he has made that his results only applied to the Hiface equipment. In fact he explicitly excludes the Hiface.
I quote from his first post:-
w
Last edited:
Naah, I still don't believe Jocko, he is just a fictional character, I need to check myself to believe
I left 100R and 10K in place and removed 75R terminating resistor and soldered a 200R multiturn trimmer to change termination on the fly and watch what will happen.
Keep adjusting trimmer until got almost perfect straight line.
Removed trimmer and measured value and got 89.2R. Soldered new terminating resistor, 88R7 value.
Here are pictures:
First picture with 50nS timebase, yellow encircled area where terminating resistor is influencing signal.
Second picture with 5nS timebase, yellow encircled area where terminating resistor is influencing signal.
To use RESISTOR CALCULATOR again: First field = 501R and second field = 88.7R and got 75.358R.
Now DMM is showing 88.7R input resistance
I left 100R and 10K in place and removed 75R terminating resistor and soldered a 200R multiturn trimmer to change termination on the fly and watch what will happen.
Keep adjusting trimmer until got almost perfect straight line.
Removed trimmer and measured value and got 89.2R. Soldered new terminating resistor, 88R7 value.
Here are pictures:
First picture with 50nS timebase, yellow encircled area where terminating resistor is influencing signal.
Second picture with 5nS timebase, yellow encircled area where terminating resistor is influencing signal.
To use RESISTOR CALCULATOR again: First field = 501R and second field = 88.7R and got 75.358R.
Now DMM is showing 88.7R input resistance
Attachments
Last edited:
Naah, I still don't believe Jocko, he is just a fictional character, I need to check myself to believe
What is this Jocko is he a ghost of someones Christmas past. This jokers name keeps leaking into this thread for some reason.
Jocko Homo is a guy that started his own forum DIYHiFi.org after much trouble here. He wasn't one of the most polite warmhearted people here together with some other lonely souls as they went after certain forum members in an unfriendly unpleasant way for the slightest reason or suspicion. One of them had a very nasty habit of sockpuppeting on a large scale which he did not get under control as it became an addiction. Despite their very high technical skills and actual expertise most of them have a negative feeling on a social level towards other human beings. As a result of this they always seem to think that they know all (they do know a lot as said before and the level is high) and that other people are running off with their designs. The latter is one of their returning goals on their crusades. They like to see themselves as professionals that don't want to mingle with normal DIY people that visit this DIY forum. Kits and ready made stuff were gruesome for them and the thought that somebody could buy a pizza from the sales of a PCB was making them sick .
After a lot of time, love, caring and forgiving they were banned from diyaudio.com. Please check their site, they refer to us as "diya" or Wal-Mart or maybe it is something else this week as mentioning www.diyaudio.com is forbidden at their forum. I hope you like their site. There is not a single problem registering at both sites. They have some people registered here.
After a lot of time, love, caring and forgiving they were banned from diyaudio.com. Please check their site, they refer to us as "diya" or Wal-Mart or maybe it is something else this week as mentioning www.diyaudio.com is forbidden at their forum. I hope you like their site. There is not a single problem registering at both sites. They have some people registered here.
Last edited:
The way this terrible discussion is going is more or less the way things went at that time. Unpleasant, disrespectful and leading nowhere (although I liked the "resistor-games" and the input of stormsonic).
IMO a thread can go off topic, can have some sharp discussion and at the end it should be readable for everybody without getting the feeling you are reading someone else's attitude problems.
But that is just a personal vision, not necessarily the vision of diyaudio.com.
Last edited:
For myself, I have a rough tongue, and probably take too much pleasure in exercising it. Nobody should take me too seriously, I don't mean any lasting damage, it's just my style. I tend to jump in with both feet, because in the final analysis I'm not scared of being wrong and it keeps things moving (I hate it enough to try to avoid it like the plague tho'). I have enjoyed this debate but I'm happy to let things go as they stand. I hope we can all encounter each other in other threads, without carrying over any ill-feelings from this one.
wakibaki
wakibaki
DIY attenuator?
What is inside the pre-made attenuators? Is there an easy DIY equivalent that could be assembled inside my DIY cable's RCA connectors? I don't have BNCs on any of my gear and would rather not have to change my connectors in order to try the attenuators. I can probably even work with surface mount resistors if leaded types are truly inferior for this application.
I presume the enjoythemusic review brought you here? There are many users who have reported their experiences in using the RF attenuators on Audiocircle & other forums!
They are nothing mysterious - just google t-pad or pi-pad - yes they could be DIYed but probably not to the precision of the pre-made ones. On the other hand as the pre-made ones don't come in RCA version, the DIYed one is probably better than putting a RCA/BNC adapter in-line.
FMAK reported on AA that his DIYed version is better than his pre-made one but didn't answer when I asked him about it!
They are nothing mysterious - just google t-pad or pi-pad - yes they could be DIYed but probably not to the precision of the pre-made ones. On the other hand as the pre-made ones don't come in RCA version, the DIYed one is probably better than putting a RCA/BNC adapter in-line.
FMAK reported on AA that his DIYed version is better than his pre-made one but didn't answer when I asked him about it!
Sendler, remember this use of RF attenuators is only possible if your SPDIF signal can withstand some attenuation & your DAC can still lock to it without any problems. This works with the Hiface because of it's high output but has also worked on other devices - the Shigaclone, some soundcards, Teac VRDS-10 CDP, etc.
Last edited:
- Status
- Not open for further replies.