user 65064
Member
- Joined
- Mar 20, 2017
- Messages
- 24
Hello guys, I hope you're enjoying a nice Sunday!
I would like to ask help from the forum since I'm currently designing a summing mixer trying to lower noise and distortion as much as I can.
Each preamp section must be able to drive 9 busses that direct it to inverting nodes of summing amplifiers (1 for master + 8 for subs) and it's feed by a pot with a "worst case source res." of 1.25 kohm.
To achieve an optimal noise performance resistor that are not feed by the preamp signal are grounded and so the load remains constant.
Using 4 kohm resistors their parallel results in a load of around 450 ohm, my set up involved the use of a parallel configuration using 2 x Opa2134/2 as buffer (see attached file).
Since they are rated to be able to drive a 600 ohm loads, I guess that paralleling them for a load of 450 ohm would be good regarding THD performances and considering the - 3db noise advantage of this config.
I guess the source of 1.25 kohm wouldn't be a problem causing heavy distortion considering the doubled input capacitance of these FET devices, they are rated to work well below 2 kohm sources without compensation, any advice regarding this?
Should I consider a doubled source res. feeding any single op amp?
Setting a bootstrapped configuration may worth or would it be a minor benefit?
Anyway I'm wondering if a push-pull set up involving a single Opa134 (compensated) would be an alternative solution (see attached file) regarding noise performance and distortion.
Any further advice is welcome!
I thank you for your time and I wish you a nice day! ;D
Best.
Herva
I would like to ask help from the forum since I'm currently designing a summing mixer trying to lower noise and distortion as much as I can.
Each preamp section must be able to drive 9 busses that direct it to inverting nodes of summing amplifiers (1 for master + 8 for subs) and it's feed by a pot with a "worst case source res." of 1.25 kohm.
To achieve an optimal noise performance resistor that are not feed by the preamp signal are grounded and so the load remains constant.
Using 4 kohm resistors their parallel results in a load of around 450 ohm, my set up involved the use of a parallel configuration using 2 x Opa2134/2 as buffer (see attached file).
Since they are rated to be able to drive a 600 ohm loads, I guess that paralleling them for a load of 450 ohm would be good regarding THD performances and considering the - 3db noise advantage of this config.
I guess the source of 1.25 kohm wouldn't be a problem causing heavy distortion considering the doubled input capacitance of these FET devices, they are rated to work well below 2 kohm sources without compensation, any advice regarding this?
Should I consider a doubled source res. feeding any single op amp?
Setting a bootstrapped configuration may worth or would it be a minor benefit?
Anyway I'm wondering if a push-pull set up involving a single Opa134 (compensated) would be an alternative solution (see attached file) regarding noise performance and distortion.
Any further advice is welcome!
I thank you for your time and I wish you a nice day! ;D
Best.
Herva