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Old 6th October 2006, 04:12 PM   #11
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I think the parameter Walter Jung referred to was Vth given
by the Slew Rate divided by the Gain Bandwidth

philpoole if this use of a TDA 1541 is using a inverting opamp
followed by a non inverting ie- same device if a dual , check your
schematic and apply a 22k resistor globally around both ie:
from inverting input (also the Analog Dac output pin ), then of opamp 1
to output of non inverting opamp2. Note feedback arising from
output of opamp 2 then applies to correct two devices and not
just one device. Simply amazing when applied to a Marantz
CD50 using 2x opa627 per channel , close to if not the best
sound I have heard. Simple and effective




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Old 6th October 2006, 08:26 PM   #12
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Hi Chris,
Currently (if you forgive the pun), its only a single opamp per channel (its my first revision of this DAC, I'm still in the early stages of playing), but I can see how the global feedback for two opamps can be beneficial.
It will definitely go on my todo list (there's lots to do, and its great fun).

At the moment, I'm busy making a balanced I2S driver receiver, so I can connect the DAC to my CDP more sensibly.

Thanks for the tip!

Cheers,
Phil
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Old 14th August 2016, 05:19 PM   #13
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Quote:
Originally Posted by jameshin View Post
OPA2107 is a bad I/V converter, Gain Bandwidth is too low. OPA2604 is much better.

I/V conversion OPA2604 > OPA627 x 2 > OPA2107

Analog stage OPA627 x 2 >OPA2107> OPA2604
hi
an other vote for you

opa2604 is one of the best for I/V and LPF after DAC.

thanks . afshin
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Old 5th September 2016, 07:31 AM   #14
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How about the Burson dual op amps? They are discrete and should perform better than IC"s....


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Old 5th September 2016, 06:48 PM   #15
Calvin is offline Calvin  Germany
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Hi,

the AD1862 has a settling time of 350ns for +-1mA output current.
To accurately follow the possible steep pulses it required an extremly fast OPAmp.
Without hitting the brake pedal -using a cap to slow down the signal- the typical 'Audio'-OPAmps would be too slow.
The inputs could be overdriven and the OPAmp could run into openloop condition, with the associated increase in THD.
It's on the other hand easy to build discrete 'current buffers' that provide for the low input impedance the DAC requires and that feed into a I/V resistor.
These very simple grounded base or grounded gate circuits achieve very low THD figures without relying on global feedback and as such they are extremely fast.
Besides, music sounds more like music with these and not as HiFi as with OPAmps.
Look for example for EUVL's Zen IV and Sen IV.
It makes use of JFETs (very simple design) but the same basic circuitry can also be designed with bipolars.

jauu
Calvin
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Old 5th September 2016, 08:09 PM   #16
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Quote:
Originally Posted by 6Feet View Post
How about the Burson dual op amps? They are discrete and should perform better than IC"s....


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Should, but don't. Not by a long shot.

Jan
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