ART PRO VLA II mod - HPF and general mods

[Aleguitarpro]

Hi.
I started modding my pro Vla II.
I found a lot of thread and discussion about first version...

I changed in I/O board the 4 NE5532 and the 4 NE5532 in the main board with IC sockets (to test OP275, OPAs and other opamps).
I changed the 6 10uF/50V electrolitics with 22uF/63V Panasonic FC caps.
I think it's not necessary to change the TL072 and TL074 because they are in the sidechain and in metering section

The VLA II has several carbon resistors in the I/O cards, but I think that the 8 resistor I've to change are the 400ohm carbon resistors (300ohm in VLA first version), but if someone has experience in modding VLA II suggestions are welcome!

I'd like to make two other changes:

1) I'd like to have GR showed in analog meter disabling the LED GR meter and this is not a big problem...

2) I'd like to understand how to modify the frequency response of the sidechain amp, adding a HPF filter with 1/2 frequencies to select.
I noticed that the VLA II doesn't affect the low frequency too much... So, I think there is a sort of pre-calculated HPF filter in the sidechain.
The only schematic I've is of the first version.
Is possible that the responsible of the frequency response are C53 and R123?

Thanks,
Ale

 

[PRR]

The sidechain path may be broken between C28 and VR1A. The load (R44||VR1A) may be as low as 1.8K, so your filter may need buffering.

 

[Aleguitarpro]

The sidechain path may be broken between C28 and VR1A. The load (R44||VR1A) may be as low as 1.8K, so your filter may need buffering.

Thank you.
I'll try and I'll post the results.

A.

 

[till]

Thank you.
I'll try and I'll post the results.

A.

Hey Aleguitarpro,
did you have success with modding the sidechain amp stage?
I'm very interested in a sidechain HPF for the Vla ii.

 

[Aleguitarpro]

Hey Aleguitarpro,
did you have success with modding the sidechain amp stage?
I'm very interested in a sidechain HPF for the Vla ii.

Yes, I did it few years ago. I don't remember exactly what I did but I remember I did it passive (without buffering or making an active filter with an opamp) and worked great.
I sold this unit years ago so I can't take a look inside, sorry!

 

[till]

Thank you for the fast reply!
I hope I will find a similar solution. Passive sounds good