DC blocking cap on VVR?

[azatplayer]

Just installed a VVR on a cathode biased amp, fan-friggin-tastic! I m a convert!

Just a quick one, with the dc blocking cap change on the input jack, does the grid resistor have to go between the guitar and the cap? Can it not stay on the grid pin? Just wondering why its that way.

I pulled the PPIMV out, which i liked, and subbed in the VVR in its place. Was instantly surprised and happy. Its a 2 hole voxish thing, running 335V, well at about 150v its fantastic. Retains all the clarity and brightness and drive, things that the PPIMV struggle a little more retaining.I love it!
Now i gotta make a fixed bias version for my Komet..

[LeeMo]

Trinityamps has some good info in the "resources" section. ayou need to sign up to see that section, but it's painless and they are a great bunch of guys over there.
http://www.trinityamps.com/phpbb/viewto ... 76&start=0

Also: Some people like to vary only the voltage on the power amp or the power amp and phase inverter. Check out 18watt.com for that. Oh and , yep , gotta be a member.
http://www.18watt.com/modules.php?name= ... oad&cid=43

I hope the helps.

LeeMo

Also: just ran across this ( just to confuse e'rybody)
http://www.el34world.com/Forum/index.ph ... ic=11399.0

[UR12]

Just installed a VVR on a cathode biased amp, fan-friggin-tastic! I m a convert!

Just a quick one, with the dc blocking cap change on the input jack, does the grid resistor have to go between the guitar and the cap? Can it not stay on the grid pin? Just wondering why its that way.

I pulled the PPIMV out, which i liked, and subbed in the VVR in its place. Was instantly surprised and happy. Its a 2 hole voxish thing, running 335V, well at about 150v its fantastic. Retains all the clarity and brightness and drive, things that the PPIMV struggle a little more retaining.I love it!
Now i gotta make a fixed bias version for my Komet..

Glad it's working good for you. The resistor needs to be on the side of the cap that connects to the grid of the tube. It is needed to give the grid a dc reference to ground. If you put it on the input (guitar) side of the cap there is no ground reference for the tube.

[azatplayer]

Thanks Dana, it's a wonderful inclusion to this build. I dont mean the 1meg grid reference, but the 33k grid r. I see a lot of folk mount them at the jack, but thought it always best on the pin. I put the cap in last night as per schem, no more dc gees it works well!

[paulster]

The grid resistor should remain on the tube pin or it's not going to be nearly as effective.

[surfsup]

Some questions...I ordered a vvr3 from dana:

As a noob still, the amp I am working on has a ppimv already (I think, the xits x10) so you said you pulled yours out. To me it seems you just wire in the vvr. Why redmoved the ppimv?

Did you scale the whole amp or just the Ptubes?

In dana's pdf instructions that show the original preamp and modified preamp, the 33k grid resistor has the cap between it and the Ptube. Shouldn't the resistor be on the tube as paulster stated?

[azatplayer]

Yes thats my original question, why is the grid resistor on the jack?
I pulled the ppimv cos i figured the vvr would take its place. AND i used the hole
Im very happy with the result, i did the entire amp, with this AC15 style of thing, works amazingly well. I have heard with marshally typology, and expresses, doing the power section only is the go.

[surfsup]

azat, you tried the X10 clone before this Voxy 15W you did right? I can't remember if that was you I was PMing... if so, I posted my latest layout with the VVR in the trainwreck x10 thread but here it is for convenience...I think I have the VVR laid out correctly?

I am still unsure if dana's VVR3 has the "extra" stuff already on the board, or if I have to order another R/C for the input and for the Vol to next grid stage as well. Could you confirm?

[azatplayer]

Im pretty sure Dana's VVR is the control only. You add the dc blocker as needed, as its not needed when doing the power section only.
Cant wait to hear your X10!

[ChopSauce]

Old thread, I know, but this one appeared as the most relevant to ask:

- how mandatory is this (DC blocking cap on input) when scaling the whole amp?

[martin manning]

As I recall it is definitely needed if you are going to run the input stage at low voltage.

[ChopSauce]

Thanks Martin. I'll do that, then.

100nF to the grids shouldn't harm anyway, right?

[martin manning]

100nF to the grids shouldn't harm anyway, right?

You probably have a 1M to ground at the grid, right? If so, the cap will make a high pass filter with that. You could go as low as 22n, where the cutoff frequency would be just over 7 Hz.

[ChopSauce]

Better (using smaller caps) then! Thanks for supporting me & further readers...