SPDIF amplifier

D

Dirk Bruere at NeoPax

Jan 1, 1970
0
I want to amplify and distribute SPDIF to three systems over maybe
100m feeding into systems that take AES/EBU.
So, thinking of putting the SPDIF through an amp and then splitting it
through a 4 Way off the shelf passive F- Splitter.
Can anyone recommend a cheap amp that might be suitable for this?
People have suggested TV amps but I can't seem to find any that don't
cut off below about 88MHz (FM).

I'd also like to boost the voltage a bit as well since I'm feeding
into EAS/EBU.
I know I could probably put one together using a buffer amp chip or
something but I don't want to have to get into making, soldering and
packaging a solution of my own.

Someone somewhere must do what I want at a reasonable price.
I know someone does it at an *unreasonable* price - approx $350, but that seems aimed at audiofools. Dirk H Hawker Jan 1, 1970 0 Why don't you buy or build a COP and convert it to AES then send it. AES is designed to send on long runs, SPDIF is not. Since your going to AES in the end just convert to AES at the source and use balanced CAT-5 cable to get it to the XLRs on the AES. Hawker D Dirk Bruere at NeoPax Jan 1, 1970 0 Why don't you buy or build a COP and convert it to AES then send it. AES is designed to send on long runs, SPDIF is not. Since your going to AES in the end just convert to AES at the source and use balanced CAT-5 cable to get it to the XLRs on the AES. "COP"? Anyway, building is out of the question for various reasons. Still, your advice sounds good. Thanks Dirk D Dirk Bruere at NeoPax Jan 1, 1970 0 Why don't you buy or build a COP and convert it to AES then send it. AES is designed to send on long runs, SPDIF is not. Since your going to AES in the end just convert to AES at the source and use balanced CAT-5 cable to get it to the XLRs on the AES. Another quick question. If/when I get my AES signal how do I split it? Can I just join the cables at source or do I need do do anything with resistors etc to match impedances etc? Dirk M Mark Zenier Jan 1, 1970 0 I want to amplify and distribute SPDIF to three systems over maybe 100m feeding into systems that take AES/EBU. What about a distribution amp for VGA video? Mark Zenier [email protected] Googleproofaddress(account:mzenier provider:eskimo domain:com) H Hawker Jan 1, 1970 0 In response to your COP question and splitting. A COP was a device made by Fostex (COP-1) that was designed to do this. I don't know if they are still made or not but COP has become a generic word these days to refer to a device for SPDIF to AES conversion. Check with Full compass or some other company for what they have. I think - Gasp - Beheringer and others make such devices on the cheap. As for splitting. AES-1992 (what I assume you are referring to as opposed to the AES over Coax who's name escapes me right now) is basically RS-422. RS-422 cannot be "split" it must be daisy chained so you go from the source to the first input and out from it (directly at the XLR connector) to the last one. You terminate the last input. The problem with this is most manufactures terminate all AES inputs so if you split it you get double termination. It "Might" work but it is not a good idea. You can remove one terminator, or you can try an active splitter. An active splitter will consist of 1 receiver and 2 transmitters. Or you can go into the first AES in, out the AES out and into the AES in of the second device. Simple splitting as you imply is not going to cut it. Good luck Hawker C [email protected] Jan 1, 1970 0 I want to amplify and distribute SPDIF to three systems over maybe 100m feeding into systems that take AES/EBU. So, thinking of putting the SPDIF through an amp and then splitting it through a 4 Way off the shelf passive F- Splitter. Can anyone recommend a cheap amp that might be suitable for this? People have suggested TV amps but I can't seem to find any that don't cut off below about 88MHz (FM). You may be able to run SPDIF through a distribution amp designed for BASEBAND video, however the signal levels for SPDIF tend to be higher (or was it lower?) so that may not work too well. But the first thing to realize about SPDIF is that it is a digital signal, so you don't need the kind of linear amplifier intended for video... in fact, you would do much better with a non-linear amplier such as a logic gate. The idea is to make a decision about the incomming signal, and then loudly proclaim the answer, renewing your noise margins. With some care at the input circuits and a 75 ohm series resistor on the output you could probably use any 74xxx series CMOS.... I think you can even invert the signal with no problem. In actual products, I've seen RS422 driver chips used. One thing you do want to be careful of though is that you get something that does not distort the duty cycle of the waveform - some receivers have trouble locking to the embedded clock if the duty cycle is far off. And in playing with SPDIF a a scope is an essential tool. Always make sure to terminte your inputs in the characteristic impedance of the line... otherwise you will get ringing, and that will case failures... I've hardly ever seen a more practical example of transmission line effects - literally had setups that did not work, stuck a short Y cable at the receiver, popped a terminating resistor on the extra lead, it works, take the resistor off it doesn't... that was of course an input with the design flaw of presenting an impedance much, much higher than 75 ohms. D Dirk Bruere at NeoPax Jan 1, 1970 0 Hawker said: In response to your COP question and splitting. A COP was a device made by Fostex (COP-1) that was designed to do this. I don't know if they are still made or not but COP has become a generic word these days to refer to a device for SPDIF to AES conversion. Check with Full compass or some other company for what they have. I think - Gasp - Beheringer and others make such devices on the cheap. As for splitting. AES-1992 (what I assume you are referring to as opposed to the AES over Coax who's name escapes me right now) is basically RS-422. RS-422 cannot be "split" it must be daisy chained so you go from the source to the first input and out from it (directly at the XLR connector) to the last one. You terminate the last input. The problem with this is most manufactures terminate all AES inputs so if you split it you get double termination. It "Might" work but it is not a good idea. You can remove one terminator, or you can try an active splitter. An active splitter will consist of 1 receiver and 2 transmitters. Or you can go into the first AES in, out the AES out and into the AES in of the second device. Simple splitting as you imply is not going to cut it. The three machines that need the AES signal are in different locations. -- Dirk http://www.onetribe.me.uk - The UK's only occult talk show Presented by Dirk Bruere and Marc Power on ResonanceFM 104.4 http://www.resonancefm.com E Eeyore Jan 1, 1970 0 Dirk said: I want to amplify and distribute SPDIF to three systems over maybe 100m feeding into systems that take AES/EBU. So, thinking of putting the SPDIF through an amp and then splitting it through a 4 Way off the shelf passive F- Splitter. Can anyone recommend a cheap amp that might be suitable for this? People have suggested TV amps but I can't seem to find any that don't cut off below about 88MHz (FM). A video DA should be OK to distribute SPDIF but the signal voltage of SPDIF is too low for AES. Graham D Dirk Bruere at NeoPax Jan 1, 1970 0 A video DA should be OK to distribute SPDIF but the signal voltage of SPDIF is too low for AES. Graham I know, although it's right on the edge over short runs. I was hoping for a bit of voltage amplification. Anyway, look like I'm going to have to make my own given the ludicrous prices companies are charging for what is basically a simple circuit. I estimate that the total cost of the parts excluding PCB for a 1:3 distributor will be around £10 one off. And that includes xformer isolation. Which is somewhat lower than the hundreds I've seen quoted. Just got to find a decent circuit design, or create one. Been looking at this (half way down) http://www.epanorama.net/documents/audio/spdif.html Opinions? Suggestions? Maybe I'll sell some as a sideline... Dirk E Eeyore Jan 1, 1970 0 Dirk said: I know, although it's right on the edge over short runs. I was hoping for a bit of voltage amplification. Anyway, look like I'm going to have to make my own given the ludicrous prices companies are charging for what is basically a simple circuit. I estimate that the total cost of the parts excluding PCB for a 1:3 distributor will be around £10 one off. And that includes xformer isolation. Which is somewhat lower than the hundreds I've seen quoted. Just got to find a decent circuit design, or create one. Been looking at this (half way down) http://www.epanorama.net/documents/audio/spdif.html Opinions? Suggestions? Ebay of course ! http://cgi.ebay.co.uk/S674-1-to-6-V...1QQihZ020QQcategoryZ67772QQrdZ1QQcmdZViewItem Graham D Dirk Bruere at NeoPax Jan 1, 1970 0 Dirk said: I want to amplify and distribute SPDIF to three systems over maybe 100m feeding into systems that take AES/EBU. So, thinking of putting the SPDIF through an amp and then splitting it through a 4 Way off the shelf passive F- Splitter. Can anyone recommend a cheap amp that might be suitable for this? People have suggested TV amps but I can't seem to find any that don't cut off below about 88MHz (FM). I'd also like to boost the voltage a bit as well since I'm feeding into EAS/EBU. I know I could probably put one together using a buffer amp chip or something but I don't want to have to get into making, soldering and packaging a solution of my own. Someone somewhere must do what I want at a reasonable price. I know someone does it at an *unreasonable* price - approx$350, but
that seems aimed at audiofools.

Looks like I'm going to be doing a DIY job, since we can't buy in at the
right price.

So, here's the design.

SPDIF feeding into an AD818 wideband amp, with a gain of 4.
The o/p of this to an HC Schitt trigger and this feeds into four RS485
line drivers. Each o/p then drives an audio digital transformer for
isolation (and to get rid of any potential ground loop problems we may
encounter).

Opinions?

--
Dirk

http://www.onetribe.me.uk - The UK's only occult talk show
Presented by Dirk Bruere and Marc Power on ResonanceFM 104.4
http://www.resonancefm.com

D

Dirk Bruere at NeoPax

Jan 1, 1970
0
Dirk said:
Looks like I'm going to be doing a DIY job, since we can't buy in at the
right price.

So, here's the design.

SPDIF feeding into an AD818 wideband amp, with a gain of 4.
The o/p of this to an HC Schitt trigger and this feeds into four RS485
line drivers. Each o/p then drives an audio digital transformer for
isolation (and to get rid of any potential ground loop problems we may
encounter).

Opinions?

BTW, I'll be using the free Eagle layout package and a cheap PCB
prototyping house in the UK. Apart from my valuable time I estimate
total overall cost for a 1 in 4 out converter (one off initially) to be
around $100 including XLR connectors. Production should bring that down to around$50 in the quantities we
want including labour cost.

--
Dirk

http://www.onetribe.me.uk - The UK's only occult talk show
Presented by Dirk Bruere and Marc Power on ResonanceFM 104.4
http://www.resonancefm.com

M

martin griffith

Jan 1, 1970
0
I want to amplify and distribute SPDIF to three systems over maybe
100m feeding into systems that take AES/EBU.
So, thinking of putting the SPDIF through an amp and then splitting it
through a 4 Way off the shelf passive F- Splitter.
Can anyone recommend a cheap amp that might be suitable for this?
People have suggested TV amps but I can't seem to find any that don't
cut off below about 88MHz (FM).

I'd also like to boost the voltage a bit as well since I'm feeding
into EAS/EBU.
I know I could probably put one together using a buffer amp chip or
something but I don't want to have to get into making, soldering and
packaging a solution of my own.

Someone somewhere must do what I want at a reasonable price.
I know someone does it at an *unreasonable* price - approx $350, but that seems aimed at audiofools. Dirk Try Kramer, they do this sort of junk for example: http://www.kramerelectronics.com/indexes/item.asp?desc=30 martin D Dirk Bruere at NeoPax Jan 1, 1970 0 Try Kramer, they do this sort of junk for example:http://www.kramerelectronics.com/indexes/item.asp?desc=30 martin Cheapest I can find is around$380 ie about 10x the price I can make
the boards for myself. Additionally, they don't even have XLR
connectors which I had budgeted for in my own design costing.
Now you have definately convinced me to do my own :-(
Maybe I'll offer the board for sale as well.

Dirk

M

Jan 1, 1970
0
Cheapest I can find is around $380 ie about 10x the price I can make the boards for myself. Additionally, they don't even have XLR connectors which I had budgeted for in my own design costing. Now you have definately convinced me to do my own :-( Maybe I'll offer the board for sale as well. Dirk Are you going to reclock, etc? and what was the price of the Kramer? Nothing on the site, that i could find martin D Dirk Bruere at NeoPax Jan 1, 1970 0 Are you going to reclock, etc? and what was the price of the Kramer? Nothing on the site, that i could find martin The$380 was the cheapest I could find for the Kramer.
And yes, I will be reclocking since the other ends feed into DSP based
systems.
I'm resigned to the fact that I won't find what I want at a reasonable
price.
I've sketched up a design based on what I wrote above and will
breadboard it this week. If it's OK I'll do a cheapo layout and get a
oneoff PCB manufactured with XLR connector positions etc. Probably
take me the best part of a week altogether, but since we will
eventually need around 100 it looks like it will save us some $30,000 over the next year. Dirk M martin griffith Jan 1, 1970 0 The$380 was the cheapest I could find for the Kramer.
And yes, I will be reclocking since the other ends feed into DSP based
systems.
I'm resigned to the fact that I won't find what I want at a reasonable
price.
I've sketched up a design based on what I wrote above and will
breadboard it this week. If it's OK I'll do a cheapo layout and get a
oneoff PCB manufactured with XLR connector positions etc. Probably
take me the best part of a week altogether, but since we will
eventually need around 100 it looks like it will save us some $30,000 over the next year. Dirk And Kramer is the bottom of the food chain..... 380$, ouch
Are you using the CS8406/CS8416 to re clock, or something more
sophisticated?
If you are using transformers, it may be cheaper to wind your own,
more info on epanorama, the commercial ones seem to be a rip off

martin

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