buffer buf634 question

[Bernhard]

Hi,

bad idea: I like to built a relay attenuator like the one in the Aleph P, but with 10 bit resolution.

Resistors 20k, 10k, 5k, 2.5k, 1.25k, 612, 315, 156, 78, 39.

So in worst case the impedance will go down to 78 ohm, at -6dB attenuation. ( 39 ohm to ground and the rest in parallel to input )

My question is: Can I drive this network with a buf 634 on CD-player level (2V) ?

I guess, a normal OP is not suitable.

If the BUF is ok, what configuration should I use ? Alone ? Inside feedback loop of OP ?


Greetings, Bernhard

[halojoy]

Originally posted by Bernhard
Hi,

bad idea: I like to built a relay attenuator like the one in the Aleph P, but with 10 bit resolution.

Resistors 20k, 10k, 5k, 2.5k, 1.25k, 612, 315, 156, 78, 39.

So in worst case the impedance will go down to 78 ohm, at -6dB attenuation. ( 39 ohm to ground and the rest in parallel to input )

My question is: Can I drive this network with a buf 634 on CD-player level (2V) ?

I guess, a normal OP is not suitable.

If the BUF is ok, what configuration should I use ? Alone ? Inside feedback loop of OP ?
Greetings, Bernhard

BUF634 can put out a lot of mA
2v/80 ohm is only 25 mA rms
that is okay for BUF634

Even a OPA2134 can put out that current,
BUF634 is specially made for a little higher power output

by the way, those curves of max current output
ans max power dissipation is in the datasheet

Google: BUF634 datasheet

/halo

[Bernhard]

yes, i have all the data sheets, my OP is an Op27 and this one has a shot circuit current of 25mA, so 25mA for normal operation may not be that good...

2134 would maybe better.

[halojoy]

Originally posted by Bernhard
yes, i have all the data sheets, my OP is an Op27 and this one has a shot circuit current of 25mA, so 25mA for normal operation may not be that good...
2134 would maybe better.

Yes, you are right, Bernhard

This applies also for real life opportunities:
Just because you could - doesn't mean you should!

To drive any component, resistor, cap, transistor or IC
close to its limit is generally not adviceable.
Not for good audio-quality operation.

Instead we use other components, to take the burdon of
the main device.
To get better performance, lower distortion .....

/halo - need some help with his burdon - at times

[jean-paul]

There are better alternatives for the OP27 like it's "brother" OPA627. Or use the BUF634 alone if you don't need amplification.
Sometimes less is more.

Mit freundlichem Gruss,

Jean-Paul