Nested opamp circuit... does it really works

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at audio line level I'd use a fet input type


TL072 can be fine as an input op amp in a composite amp as long as the output isn't required to do much, TL072, LF411 and similar generation are very cheap but very old

better output stages, more modern processes seem to come at a pretty steep cost increase

still rather old but as expensive as some of the newer chips: OPA2604, OPA2134, LT1022...

the OPA627 is legendary in audio but very pricey - often faked don't even think about buying on eaby


I've used AD8610, today I'd try OPA1642 series for many audio applications

Thank you for your suggestions.
have tried opa2604 and I like the sound
but do not like opa2132 or opa2134 :eek:

You should have the input impedance defined and the DC bias explicitly set with a resistor to ground (from the input, non-inverting, terminal).

sorry just lazy to draw it out :p
 
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I have thought again the two circuits above
and theoretically the distortion of these two are the same? :confused:
 

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There really is no need to have a front op amp, it will be equally good or even better with just one op amp driving the BUF 634 with feedback going straight into the inverting input. With OPA134 it is hard to go wrong, and you will have better RFI behaviour than with a bipolar input op amp.

"feedback going straight into the inverting input"

do you mean unity gain?

the front opamp is thought to be used for amplification.
if only unity gain the output voltage is not enough.

but if the BUF634 is not used with an opamp as unity gain (eg. part of amplification)
the distortion is quite noticeable and sounds rough
as tried before :(
 

I have thought again the two circuits above
and theoretically the distortion of these two are the same? :confused:[/QUOTE]

You should not require the additional unity gain driver to obtain satisfactory distortion performance from the BUF. Nothing audible. There's something else wrong with your implementation if you can hear distortion.

Using 2 opamps here is confusing you, yes? Make it work with 1 first, much easier to understand.
 
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You should not require the additional unity gain driver to obtain satisfactory distortion performance from the BUF. Nothing audible. There's something else wrong with your implementation if you can hear distortion.

Using 2 opamps here is confusing you, yes? Make it work with 1 first, much easier to understand.

distortion i meant is the distortion from the opamp and buf634 themselves, Not from a wrong design.

made it worked with one already, but the BUF634 sounds sandy and rough so...
think about using an low distortion opamp with it.

BUF634 with unity gain opamp sounds satisfying though.
 
at audio line level I'd use a fet input type


TL072 can be fine as an input op amp in a composite amp as long as the output isn't required to do much, TL072, LF411 and similar generation are very cheap but very old

better output stages, more modern processes seem to come at a pretty steep cost increase

still rather old but as expensive as some of the newer chips: OPA2604, OPA2134, LT1022...

the OPA627 is legendary in audio but very pricey - often faked don't even think about buying on eaby


I've used AD8610, today I'd try OPA1642 series for many audio applications

AD 8610 and 8620 where my favorites. OPA 627 is to old.
 
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This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.