[kasra]

Im intrested in building the curcuit that can be found in this thread:
http://www6.head-fi.org/forums/showt...rossfeed+grado

Since i have lots of LM6172 im going to use those.
Having read tangents cranky op article I was wondering if the bandwidth limiter cap should be applied to the "B"-marked/second opamp? If so how?

How about the ground channel? How do I apply the cap there?

Also are there any better solutions for ground channel?

thank you!

 

[rickcr42]

Quote:

Since i have lots of LM6172 im going to use those.

you need to be aware just how finicky this chip can be.Don't do layout just right and you will have not an amp but an oscillator.Can be real pain to work with but Tomo has had good success by using the TI eval module as a starting point and the WNA amp threads below have a lot of general info on using this chip.

The "current doubling" circuit may not be suitable because it will be even harder to get right but good luck anyway.

 

[kasra]

thank you

Is it just as simple as in the manual: when configured as buffer: "a feedback resistor of 1k must be added in parallell to the feedback capacitor. (>2pF)

Theorthically I just add 1k parallelled with >2pF in the feedback of the second/"B"-marked opamps, and both the ground opamps?

 

[kasra]

What do you guys think about these modifications?
Are they done the right way? Any other suggestions?

On top its the linestage, and the one under is the ground

 

[rickcr42]

looks pretty good but i do question the use of such high value resistors in the feedback loop plus the 10 pf bypass caps are at two different impedances (the resitors again0 and will have different hinge points for the RF roloffs.

Give it a try on the old breadboard and report the results

 

[kasra]

Quote:

Originally Posted by rickcr42 looks pretty good but i do question the use of such high value resistors in the feedback loop

These were values from tangents homepage, what advantages does lower values give me?

Quote:

Originally Posted by rickcr42 plus the 10 pf bypass caps are at two different impedances (the resitors again0 and will have different hinge points for the RF roloffs. Give it a try on the old breadboard and report the results

Well would that affect the sound in any way?

Also what do you think about putting a TLE2426 insted of those 2 1k resistors?

 

[rickcr42]

Quote:

These were values from tangents homepage, what advantages does lower values give me?

lower feedback loop impedance and possibly lower noise though results vary with various chips

Quote:

Well would that affect the sound in any way?

you are putting two separate amplifiers in parallel,running them side by side into a common load.

Using a different hinge point for each is like having three tires the same on your car and one not the same.It will go but do you really like it ?

And again,this chip is one that has a rep for being a bit touchy and any chance it gets to oscillate it will.Keeping the two amps matched and hopefully stable is a desired goal here or you may not even know the amp is oscillating until it burns up from overheating.The sound is not always a giveaway on this when the problem is ultrasonic