Hi Peter,
I assuming that the short piece of green ribbon you are using probably provides some level of stray or gimmick capacitance already - have you mounted a crystal directly on the board without some capacitance?
One other question is I noted the thevenin equivalent source impedance of the spdif out with 75//200 is: 55 ohms - are you using 50 ohm coax? I am planning on using 243 and 110 ohm resistors which results in ~75.8 ohm source impedance for my 75 ohm coax. (Of course I do not have 75 ohm bnc..
I keep looking... 
) I'm assuming signal in the range of 3.3Vpp on the processor chip spdif output.
I assuming that the short piece of green ribbon you are using probably provides some level of stray or gimmick capacitance already - have you mounted a crystal directly on the board without some capacitance?
One other question is I noted the thevenin equivalent source impedance of the spdif out with 75//200 is: 55 ohms - are you using 50 ohm coax? I am planning on using 243 and 110 ohm resistors which results in ~75.8 ohm source impedance for my 75 ohm coax. (Of course I do not have 75 ohm bnc..
I keep looking... ) I'm assuming signal in the range of 3.3Vpp on the processor chip spdif output.
Yes, I installed the crystal directly on the board and it works fine without caps.
The Shigaraki transport uses indeed 200/75R resistors at the output and I had originally 220/75R Caddocks there, but later after some suggestions for another forum member decided to try some other resiustors in that spot. The Caddock 75R was definitely the best choice for 75R shunt, however the series resistor choice was not that clear.
After some experimentation no resistor at all gave most "clean" sound, however I was noticing also some edginess and in a long run it didn't work for me. The Caddock wasn't that good here, and Vishay S102 seemed to give the best results sonically. I tried two values I had on hand: 240R and 62R. The first one added too much veiling and 62R was just about right: more smooth than direct connection and almost no signature of it's own.
Riken is a bit more euforic, but overall good choice too when cost is consideration.
In all test I was using Belkin Synapse 6ft digital intrconnect: by some people regarded as one of the best out there, no longer available though
The Shigaraki transport uses indeed 200/75R resistors at the output and I had originally 220/75R Caddocks there, but later after some suggestions for another forum member decided to try some other resiustors in that spot. The Caddock 75R was definitely the best choice for 75R shunt, however the series resistor choice was not that clear.
After some experimentation no resistor at all gave most "clean" sound, however I was noticing also some edginess and in a long run it didn't work for me. The Caddock wasn't that good here, and Vishay S102 seemed to give the best results sonically. I tried two values I had on hand: 240R and 62R. The first one added too much veiling and 62R was just about right: more smooth than direct connection and almost no signature of it's own.
Riken is a bit more euforic, but overall good choice too when cost is consideration.
In all test I was using Belkin Synapse 6ft digital intrconnect: by some people regarded as one of the best out there, no longer available though
An externally hosted image should be here but it was not working when we last tested it.
As to BNC connectors on digital cables, I'm not that crazy about it any longer.
When I got my 6ft Belkin I cut it in half and terminated one end with Vampire BNC, however, I noticed it sounded worse than the original RCA/RCA 6ft cable.
I later found the info about cable length and reflections, and this seems to be more critical than termination itself:
http://www.uhfmag.com/Issue74/UHF74.pdf
"When a transition is launched into the transmission line, it takes a period of time
to propagate or transit to the other end. This propagation time is somewhat slower
than the speed of light, usually around 2 nanoseconds per foot, but can be longer…
When the transition reaches the end of the transmission line (in the DAC), a reflection
can occur that propagates back to the driver in the transport. Small reflections can occur
in even well matched systems. When the reflection reaches the driver, it can again
be reflected back towards the DAC. This ping-pong effect can sustain itself for several
bounces depending on the losses in the cable. It is not unusual to see 3 to 5 of these reflections
before they finally decay away. So, how does this affect the jitter? When
the first reflection comes back to the DAC, if the transition already in process at the
receiver has not completed, the reflection voltage will superimpose itself on the transition
voltage, causing the transition to shift in time. The DAC will sample the transition
in this time-shifted state and there you have jitter.
If the rise-time is 25 nanoseconds and the cable length is 3 feet, then the propagation
time is about 6 nanoseconds. Once the transition has arrived at the receiver, the reflection
propagates back to the driver (6 nanoseconds) and then the driver reflects this back to the
receiver (6 nanoseconds) = 12 nanoseconds). So, as seen at the receiver, 12 nanoseconds
after the 25 nanosecond transition started, we have a reflection superimposing on the
transition. This is right about the time that the receiver will try to sample the transition,
right around 0 volts DC. Not good. Now if the cable had been 1.5 metres, the reflection
would have arrived 18 nanoseconds after the 25 nanosecond transition started at
the receiver. This is much better because the receiver has likely already sampled the
transition by this time."
When I got my 6ft Belkin I cut it in half and terminated one end with Vampire BNC, however, I noticed it sounded worse than the original RCA/RCA 6ft cable.
I later found the info about cable length and reflections, and this seems to be more critical than termination itself:
http://www.uhfmag.com/Issue74/UHF74.pdf
"When a transition is launched into the transmission line, it takes a period of time
to propagate or transit to the other end. This propagation time is somewhat slower
than the speed of light, usually around 2 nanoseconds per foot, but can be longer…
When the transition reaches the end of the transmission line (in the DAC), a reflection
can occur that propagates back to the driver in the transport. Small reflections can occur
in even well matched systems. When the reflection reaches the driver, it can again
be reflected back towards the DAC. This ping-pong effect can sustain itself for several
bounces depending on the losses in the cable. It is not unusual to see 3 to 5 of these reflections
before they finally decay away. So, how does this affect the jitter? When
the first reflection comes back to the DAC, if the transition already in process at the
receiver has not completed, the reflection voltage will superimpose itself on the transition
voltage, causing the transition to shift in time. The DAC will sample the transition
in this time-shifted state and there you have jitter.
If the rise-time is 25 nanoseconds and the cable length is 3 feet, then the propagation
time is about 6 nanoseconds. Once the transition has arrived at the receiver, the reflection
propagates back to the driver (6 nanoseconds) and then the driver reflects this back to the
receiver (6 nanoseconds) = 12 nanoseconds). So, as seen at the receiver, 12 nanoseconds
after the 25 nanosecond transition started, we have a reflection superimposing on the
transition. This is right about the time that the receiver will try to sample the transition,
right around 0 volts DC. Not good. Now if the cable had been 1.5 metres, the reflection
would have arrived 18 nanoseconds after the 25 nanosecond transition started at
the receiver. This is much better because the receiver has likely already sampled the
transition by this time."
I've been following this post with interest, having wanted to replace my Pioneer DVD 'transport' for quite awhile. If someone could make a transport kit based on this (or another) mechanism, I would think it would be a good seller. Heck, even a metal plate template ala Front Panel Express would be useful.
kstagger said:
It would be cool, unfortunately the mechanism and board this project is based on has been discontinued.. The replacement from what I have been able to glean is less user friendly. The hardware that this project is based upon is proving really hard to get here in the USA. I've been trying since the very day this thread was opened by Peter. I should have a donor boombox in the next day or so, whether or not it has the right mechanism remains to be seen. For some reason I was too cheap to buy a seriously overpriced refurb on Amazon when it was still available, but if the one I got has the right board and mechanism I will have saved at least $40 over the other one.. (And it's new, not a refurb.)
Thanks Peter. Unfortunately I don't have access to the NOS ERO, so I'll have to use the MKP1837 or perhaps a WIMA or something. I've never really liked the OSCONS, I'd be more likely try to the Elna or Rubycon ZA/ZL first, but the Black Gates are cheap enough for me.
Looks like I'll buy the following once the item arrives, as from what I've gathered from the thread this seems to be the current recommendations:
Digikey:
(1) 300-8441-ND
(1) LM7808CT-ND
(2) MSR860GOS-ND
(1) HM548-ND
Michael Percy:
(1) Caddock MK-132 75.0R
(1) Vishay S102 60.0R
(1) BG STD 1000/25
(1) BG FK 2200/35
(2) BG N 4.7/50
(1) BG N 10/50
(1) BG N 33/16
(1) BG NX 47/6.3
Hopefully I didn't miss anything!
Looks like I'll buy the following once the item arrives, as from what I've gathered from the thread this seems to be the current recommendations:
Digikey:
(1) 300-8441-ND
(1) LM7808CT-ND
(2) MSR860GOS-ND
(1) HM548-ND
Michael Percy:
(1) Caddock MK-132 75.0R
(1) Vishay S102 60.0R
(1) BG STD 1000/25
(1) BG FK 2200/35
(2) BG N 4.7/50
(1) BG N 10/50
(1) BG N 33/16
(1) BG NX 47/6.3
Hopefully I didn't miss anything!
Percy
I have had significant problems contacting Mr. Percy.
Hope all is well, but I could not get an order in with him. Had to use Soniccraft and PartsConnexion instead. Both I can talk to on the phone as well. Too bad, he has a good selection of parts.
This is not meant to bash him, just a heads up.
I have had significant problems contacting Mr. Percy.
Hope all is well, but I could not get an order in with him. Had to use Soniccraft and PartsConnexion instead. Both I can talk to on the phone as well. Too bad, he has a good selection of parts.
This is not meant to bash him, just a heads up.
Getting hard to find in the UK as well, I just got one from www.bennettsonline.co.uk Don't know what I'm going to do with it but thought I better get one. If I wait till I understand what to do then it'll be too late