installing VVR2 in rocket

[vibratoking]

IME, coupling caps are necessary to avoid scratchy pots. Even for a modest amount of attenuation. You found that out. Follow Dana's instructions as they are correct.

I have also found that the chassis is often not a good enough heat sink, although, that depends on the chassis alloy, configuration and finish - chrome, paint, etc... I have normally needed an external heat sink bolted to the chassis through the FET attachment point. BTW, if the FET fries, the amp runs at full power and no attenuation is possible. The amp continues to function, but the VVR does not.

[norburybrook]

yes I've been looking at Dana's instructions now I 've found them.

can I ask why it's necessary to move the 1M resistor on the input 'After' the newly installed cap? and where's the best place to ground it?

mine is obviously still before and seems to work although not 100% scratch free.

there also mention of another cap between the volume and the grid.



Marcus

[xtian]

can I ask why it's necessary to move the 1M resistor on the input 'After' the newly installed cap? and where's the best place to ground it?...there also mention of another cap between the volume and the grid.

The 1M is needed as a grid-to-ground reference, so it has to go on the tube side of the new DC blocking cap.

In my two Rocket builds, I added this input arrangement to accomodate the VVR, but I did not add the second blocking cap after the volume control. It worked out OK--no scratchy pots.

[vibratoking]

yes I've been looking at Dana's instructions now I 've found them.

can I ask why it's necessary to move the 1M resistor on the input 'After' the newly installed cap? and where's the best place to ground it?

mine is obviously still before and seems to work although not 100% scratch free.

there also mention of another cap between the volume and the grid.

Marcus

The 1M resistor is necessary to bias the grid. The grid should have a reference voltage. See this link from Aiken's site:http://www.aikenamps.com/index.php/desi ... amplifiers

Leave it grounded where it was or you can experiment with grounding it at the input jack or at the first stage. IME, not much difference in a Rocket.

The 'extra' cap and resistor after the cap are sometimes necessary to avoid DC on the volume pot. The issue here is the same as on the front end - DC on the pot.

[norburybrook]

thanks Guys, I'll do it tomorrow when I get back to the studio




Marcus

[norburybrook]

moved the 1m resistor from the input socket to after the 0.1uF cap and grounded it back to the input.

No scratchiness anymore

job done.

thanks everybody. A simple thing to do in the end but a really worthwhile addition to the rocket.


Marcus