DIY active cable

Koy · 27th March 2003, 10:15 PM

Doing experiments with interlink (signal) cables I noticed I was not able to find the the optimal one. Even trying more expensive one. Browsing on the net I discovered very interesting solution - an active cable, by author called AudioBuffer - http://www.pha.inecnet.cz/macura/buffer_en.html. Not expensive, simple circuit. What do you think about?

Bill Fitzpatrick · 28th March 2003, 12:58 AM

Link is no good.

seangoesbonk · 28th March 2003, 01:28 AM

Should be:
http://www.pha.inecnet.cz/macura/buffer_en.html

Cradle22 · 28th March 2003, 07:24 AM

Hi!

Looks nice, although I I use an OPA134, I would also use it as a balanced line driver (since this is what OPA134 is for).

Of course, then you will need to use the corresponding de-balancing circuit (don't know the OPA nr right now), unless you have balanced inputs on your amplifier...

But sometimes I will check it out (I have some of those OPAs lying around...)

Bye,

Arndt

carlmart · 28th March 2003, 10:12 AM

Quote:

Originally posted by Cradle22

Looks nice, although I I use an OPA134, I would also use it as a balanced line driver (since this is what OPA134 is for).

Of course, then you will need to use the corresponding de-balancing circuit (don't know the OPA nr right now), unless you have balanced inputs on your amplifier...

But sometimes I will check it out (I have some of those OPAs lying around...)

I think you are mixing up the letters: the balanced driver is the DRV134. The OPA134 is a regular opamp.

Carlos

carlosfm · 28th March 2003, 01:42 PM

Hi,
Is the op-amp really needed?

Don't think so.
Only if you need the gain, in case of a headphone amp.
The buf634 alone has 250 ma current drive, not 200 as it says on that link.

Koy · 28th March 2003, 01:50 PM

Gainf of the BUF is lower than 1 ( about 0.9) i.e. you need gain stage to correct it. Unless you accept attenuation of the signal.

carlosfm · 28th March 2003, 03:49 PM

Koy,

You have a point there.
But on the datasheet you can see:

GAIN:
RL = 1k, VO = ±10V 0.95 0.99 [ [ V/V
RL = 100, VO = ±10V 0.85 0.93 [ [ V/V
RL = 67, VO = ±10V 0.8 0.9 [ [ V/V

I suppose that above 1kohm load it's unity gain...

PMA · 28th March 2003, 04:14 PM

Carlosfm,
yes, the opamp is needed. It estimates the overall behavior of the circuit, the BUF634T is there to
1) deliver enough current to drive matched cable,
2) to eliminate capacitive load
3) to minimize thermal feedback on OA chip
It results in considerably better sound. Though it might seem not making sense, it really does. The best way is to try it.

PMA · 28th March 2003, 04:17 PM

Carlosfm,
there is a load of 50 Ohm + 50 Ohm, i.e. 100 Ohm. The terminating resistor of 50 Ohm is a must. Omitting it all the effect disappears.

27th March 2003, 10:15 PM	#1
Koy diyAudio Member Join Date: Jan 2001 Location: Zlin	DIY active cable Doing experiments with interlink (signal) cables I noticed I was not able to find the the optimal one. Even trying more expensive one. Browsing on the net I discovered very interesting solution - an active cable, by author called AudioBuffer - http://www.pha.inecnet.cz/macura/buffer_en.html. Not expensive, simple circuit. What do you think about?

28th March 2003, 01:28 AM	#3
seangoesbonk diyAudio Member Join Date: Jan 2002 Location: Vancouver, BC, Canada	Should be: http://www.pha.inecnet.cz/macura/buffer_en.html __________________ My girlfriend's sub is bigger than mine...

28th March 2003, 07:24 AM	#4
Cradle22 diyAudio Member Join Date: Jan 2003 Location: Dortmund, Germany	Hi! Looks nice, although I I use an OPA134, I would also use it as a balanced line driver (since this is what OPA134 is for). Of course, then you will need to use the corresponding de-balancing circuit (don't know the OPA nr right now), unless you have balanced inputs on your amplifier... But sometimes I will check it out (I have some of those OPAs lying around...) Bye, Arndt __________________ ************************ A Sacrifice For Freedom

28th March 2003, 01:42 PM	#6
carlosfm Banned Join Date: Mar 2003 Location: Lisbon, Portugal	it's only a buffer... Hi, Is the op-amp really needed? Don't think so. Only if you need the gain, in case of a headphone amp. The buf634 alone has 250 ma current drive, not 200 as it says on that link.

28th March 2003, 03:49 PM	#8
carlosfm Banned Join Date: Mar 2003 Location: Lisbon, Portugal	BUF634 Koy, You have a point there. But on the datasheet you can see: GAIN: RL = 1k, VO = ±10V 0.95 0.99 [ [ V/V RL = 100, VO = ±10V 0.85 0.93 [ [ V/V RL = 67, VO = ±10V 0.8 0.9 [ [ V/V I suppose that above 1kohm load it's unity gain...


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28th March 2003, 12:58 AM	#2
Bill Fitzpatrick diyAudio Member Join Date: Jun 2001 Location: Eugene, OR	Link is no good.

28th March 2003, 01:50 PM	#7
Koy diyAudio Member Join Date: Jan 2001 Location: Zlin	Gainf of the BUF is lower than 1 ( about 0.9) i.e. you need gain stage to correct it. Unless you accept attenuation of the signal.

28th March 2003, 04:14 PM	#9
PMA diyAudio Member Join Date: Apr 2002 Location: Prague, Kitakyushu, Fukuoka	Carlosfm, yes, the opamp is needed. It estimates the overall behavior of the circuit, the BUF634T is there to 1) deliver enough current to drive matched cable, 2) to eliminate capacitive load 3) to minimize thermal feedback on OA chip It results in considerably better sound. Though it might seem not making sense, it really does. The best way is to try it.

28th March 2003, 04:17 PM	#10
PMA diyAudio Member Join Date: Apr 2002 Location: Prague, Kitakyushu, Fukuoka	Carlosfm, there is a load of 50 Ohm + 50 Ohm, i.e. 100 Ohm. The terminating resistor of 50 Ohm is a must. Omitting it all the effect disappears.

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