ART PRO VLA - Kenetec mod

[Silvas]

I was wondering the same...

Besides the fact that many people may like MF better than CF...

roger foote suggested this

Main Board:
Replaced 4-NE5532 with OP275
Replaced 2-TL072 with OPA2604
Replaced 2-TL074 with TLE2074 (probably not needed)

Rear I/O Board:
Replaced 2-TL072 with OPA2604
Replaced 6-10 uf @50V electrolytics with Panasonic FC 22uf @ 63V
Replaced 8-300 Ohm 5% Carbon film resistors with 200 Ohm 1% Metal film
(The caps are marked C35,C38,C41,C56,C58 AND C63)

Why replace the 300 R resisters with 200 R?  Or is that a typo?  (Which resistors?)

 

[joe-electro]

I just wanted to update you guys on a couple of things regarding the Kenetek Pro VLA II mod. First, the UTC A-20 is not exactly the same as the Stancor WF-30.  For whatever reason, the A-20 has provides way too much voltage gain (~8 dB) for use in this mod when wired 1:2. It will cause distortion in the audio chain; it throws off the threshold and ratio controls and the metering is way off.  If you're planning on using UTC A-20's for this mod, wire them 1:1. Second, the schematic that is being thrown around is for the Pro VLA, not Pro VLA II.  There are differences in the sidechain circuit although I have not taken the time to trace out the differences. Just be aware that if you're making decisions based on that schematic you may find that your mods aren't behaving as you thought they should.

Thanks,

Joe

 

[malak]

Hey guys, i'm a noob too but have just purchased a pro VLA. I'm going to do the standard tube mod, but I was wondering if someone could elaborate a bit more on the OPA swap, what kind of difference it makes to the sound and how difficult it is to do for someone who doesnt often mod circuitry? I've built stepping tone generators and stuff but i'm not going to try and brag about that...

Thanks so much!

 

[malak]

^bump?  :-[

 

[RedNoise]

Hi Balak :
According to me BurrBrown in input output section "tightened" the signal globaly...More clear , more "open" in the high end...
I did this mini mod a long ago so I do not really remember the circuit etc , but I love to have done it !
(Have to change caps , tubes and add stancor WF30 ...)
I did not change the TL074 .

Traces on pcb are really really thin so...Take care not to heat them too much...Quite easy with a Weller electro-desoldering pump...

 

[lassoharp]

Hey guys, i'm a noob too but have just purchased a pro VLA. I'm going to do the standard tube mod, but I was wondering if someone could elaborate a bit more on the OPA swap, what kind of difference it makes to the sound and how difficult it is to do for someone who doesnt often mod circuitry? I've built stepping tone generators and stuff but i'm not going to try and brag about that...

Thanks so much!

The difficulty will likely be related to ease of accessibility and working in tight quarters.  I considered doing this on an original VLA I had and from what I saw I'd say the job could be considered - depending on your state of mind -  a mildly tedious job or a real PITA.  Like RedNoise said, be really careful with the iron.

 

[malak]

Thanks guys - if the tracing is that dodgy i dont think taking the chance is a wise idea. My iron isnt the most reliably accurate so i think i'll just stick with the tube swap mod! Thanks again

 

[Silvas]

For me, the tube swap and input opamp change was enough ! really nice compressor.

 

[malak]

^that's what I was referring to, Silvas. Any comment on how difficult the opamp swap on the input stage was?

 

[Silvas]

^that's what I was referring to, Silvas. Any comment on how difficult the opamp swap on the input stage was?

Just be careful when desoldering...

 

[Spencerleehorton]

HI Guys,

just wanted to get hold of a high res schematic for either version of art pro vla mk1 or mk2 please if you could send it to me please.

regards

 

[beatswork]

I'm using the Art Pro VLA II purely as a tube buffer between balanced components. I was thinking of replacing stock tubes with a lower gain equivalent so that I could crank the gain without overdriving connected amp. Thoughts?

And would be highly appreciative of any other insights on optimizing as pure tube buffer - I.e. bypassing compression, changing out resistors to increase plate voltage etc.