AVC

0 Members and 1 Guest are viewing this topic. Read 2115 times.

trev4h

  • Jr. Member
  • Posts: 10
AVC
« on: 3 Apr 2015, 02:07 am »
Will the AVC have a red circuit board like the rest of the modules?  All the current pics show a green board.  Also, If I get an AVC now, when you develop the AVC/Tube combo down the road, will I be able to add the tube stage to it down the road? 

RDavidson

  • Full Member
  • Posts: 2513
Re: AVC
« Reply #1 on: 3 Apr 2015, 03:26 am »
Something to note is that the AVC is meant to give the purest sound. This type of volume control inherently provides a low output impedance to the amplifier. Most amplifiers "want" a low impedance signal in order to work/sound their best. Adding a buffer after the AVC is really unnecessary inless you want more electronics in the signal path or need a little bit of voltage gain that a buffer can provide, beyond the little bit the AVC provides in its upper last few volume steps.

The RVC is different. It uses just a ladder of resistors. The issue with fully passive attenuation like this is it does nothing to the source signal impedance, which can be high. In some cases an RVC is OK if the source impedance is low (low enough for the amp being used). BUT, to ensure it isn't a problem, the use of a buffer (in this case a tube buffer) lowers the output signal impedance to the amp. It can also add some tonal color.....which can be a pro or con, depending on what you like.

Given this info, it really makes very little sense to add a tube buffer after an AVC. After an RVC, it makes COMPLETE sense.

Vinny is giving everyone the best options all around.
AVC = pure and versatile.
RVC + buffer = colored (in a good way if you're one who likes what tubes do) and versatile.
RVC = pure but perhaps not the most versatile.
« Last Edit: 3 Apr 2015, 04:43 am by RDavidson »

WireNut

Re: AVC
« Reply #2 on: 3 Apr 2015, 07:43 am »

RVC + buffer = colored (in a good way if you're one who likes what tubes do) and versatile.



So If I wanted good volume controls plus tubes the RVC + Buffer is the way to go?
Does the tube stage add any gain to the preamp output?
Are balanced Ins / outs available or only unbalanced connections?
« Last Edit: 3 Apr 2015, 08:02 pm by WireNut »

brh

  • Jr. Member
  • Posts: 102
Re: AVC
« Reply #3 on: 4 Apr 2015, 12:33 am »
So If I wanted good volume controls plus tubes the RVC + Buffer is the way to go?

Currently, that's the only way to go if you want tubes and a volume control.

Does the tube stage add any gain to the preamp output?

Nope, unity gain.

Are balanced Ins / outs available or only unbalanced connections?

Currently unbalanced only, Vinnie has mentioned that a balanced solution is in the works.

Vinnie R.

Re: AVC
« Reply #4 on: 4 Apr 2015, 03:52 am »
Will the AVC have a red circuit board like the rest of the modules?  All the current pics show a green board.  Also, If I get an AVC now, when you develop the AVC/Tube combo down the road, will I be able to add the tube stage to it down the road?

Hi trev4h,

Eventually, we should have red PCBs for the AVC.  The upper PCBs for the AVC were already green from Bent Audio (John Chapman was selling them as Slagleformers before we started using them in LIO), so we have been using them and John did the lower board PCB layout to make them work with LIO and he used green to match.  I do want to migrate to all red, but it might not happen until the upcoming AVC/Tube module (below):

If you buy the AVC module now, and later want the AVC/Tube module down the road, I DO intend to offer an upgrade program of some sort for all LIO customers.  You would pay the difference + shipping.  It will be very easy to upgrade.  Details will be available in time...


Hi RDavidson,

Yes, the AVC is more transparent overall than the RVC + Tubestage. 

Quote
Given this info, it really makes very little sense to add a tube buffer after an AVC.

For those who love the RVC + Tubestage, the combo AVC / Tubestage board that we hope to offer later will be be a
"step-up" (no pun intended) in performance.  I will explain more about it and how it compares to all the other
options that we currently offer when I at least have a working prototype board (everything on one board and when we
confirm that we can get it all to fit - but I'm confident that it will happen).  More on that later...

Quote
Adding a buffer after the AVC is really unnecessary inless you want more electronics in the signal path or need a little bit of voltage gain that a buffer can provide, beyond the little bit the AVC provides in its upper last few volume steps.

Just to avoid confusion...

The LIO Tubestage after the AVC would add current gain (not voltage gain, as the LIO Tubestage is unity voltage gain).
But compared to the RVC + Tubestage, the LIO AVC actually offers voltage gain (at max volume, it is +7dB) and the RVC does not (at max volume, it is 0dB = unity gain).

Hi WireNute,

Looks like brh beat me to it and answered all your questions (thanks!)  :thumb:

Vinnie