The PPIMV (Post-PI-Master-Volume) thread.

rockstah · Post by **rockstah** » Wed Nov 08, 2006 12:27 am

novosibir wrote:
rockstah wrote:i dont hear any PO but it has no gain... well barely any - maybe has to do with the last time i tried it i used a 500k dual... or was it 1M dual pot.. anyway
That's impossible, when you have choosen the 'right' resistor values!

The resulting resistance with the pot dimed is about the same as with a 500K pot and 470K bias fed resistors - and even more as with the 500K pot and the stock 220K bias fed resistors.

Check your above mentioned 2M resistors! Maybe you took by accident 2K ? That could explain the "has no gain... well barely any"

Larry

i used a 2M ( red black green )and a 220k (red red yellow) IN SERIES FOR 2.220M - It has gain just not that of a 3 stage amp.

i do see now that the resistors make the pot = 220k when dimed - which means to me this PPIMV should sound the same when the amp is dimed as if you didnt have a master at all!

so what is the purpose of the resistors and how do they benifit this PPIMV? something about if the pot fails?

Mark

MacGaden · Post by **MacGaden** » Wed Nov 08, 2006 8:51 am

I read in an earlier post that if the pot fails you have no bias, and your tubes would die. Quickly. Added benefit: Same sound as without it on 10.

Could someone sum up this latest version of he PPIMV, and maybe draw a schematic for it ?

Brentsp · Post by **Brentsp** » Wed Nov 08, 2006 10:39 am

I've hear of a lot of guys replacing the 220k resistors for 150ks in their NMV Marshalls for a browner tone. So if the PPIV with 220k's will end up be around 150k maxed than thats not really a bad thing.

novosibir · Post by **novosibir** » Wed Nov 08, 2006 10:56 am

rockstah wrote:i used a 2M ( red black green )and a 220k (red red yellow) IN SERIES FOR 2.220M - It has gain just not that of a 3 stage amp.

You can check the pot w/ the resistors on it w/o unsoldering anything. Measure the resistance between the output lug (where the bias voltage is applied) and the wiper with the pot dimed! When the pot's value is exactly 250K with a 2.2M resistor soldered to, you should measure about 225K - what's about the same value you have in an amp w/o PPIMV due to the bias feed resistors.

If you'd measure significant less, then you've confused the resistors.

rockstah wrote:... so what is the purpose of the resistors and how do they benifit this PPIMV? something about if the pot fails?

The benefit of the 250K PPIMV as opposed to a 500K PPIMV is when you've backed off the pot, you don't loose that much highs, because the input capacitance of the output tubes is creating a low-pass/hi-cut filter with the entire resistance from the previous coupling cap to the grid.

Another benefit is, that the signal flow from the PI to the output grids with a 250K pot (backed off) is only half as sensitive for receiving shit out of the air as with a 500K pot.

The 2.2M actually only is for safety, because if the pot's wiper fails, then w/o this resistor the output tube outright would be w/o bias voltage and die immediately. With the resistor applied and a failing wiper shure no signal voltage will reach the output tube, but the output tube will be supplied with bias voltage furthermore through the 2.2M and survive

Larry

rockstah · Post by **rockstah** » Wed Nov 08, 2006 12:35 pm

novosibir wrote:
rockstah wrote:i used a 2M ( red black green )and a 220k (red red yellow) IN SERIES FOR 2.220M - It has gain just not that of a 3 stage amp.
You can check the pot w/ the resistors on it w/o unsoldering anything. Measure the resistance between the output lug (where the bias voltage is applied) and the wiper with the pot dimed! When the pot's value is exactly 250K with a 2.2M resistor soldered to, you should measure about 225K - what's about the same value you have in an amp w/o PPIMV due to the bias feed resistors.

If you'd measure significant less, then you've confused the resistors.

rockstah wrote:... so what is the purpose of the resistors and how do they benifit this PPIMV? something about if the pot fails?
The benefit of the 250K PPIMV as opposed to a 500K PPIMV is when you've backed off the pot, you don't loose that much highs, because the input capacitance of the output tubes is creating a low-pass/hi-cut filter with the entire resistance from the previous coupling cap to the grid.

Another benefit is, that the signal flow from the PI to the output grids with a 250K pot (backed off) is only half as sensitive for receiving shit out of the air as with a 500K pot.

The 2.2M actually only is for safety, because if the pot's wiper fails, then w/o this resistor the output tube outright would be w/o bias voltage and die immediately. With the resistor applied and a failing wiper shure no signal voltage will reach the output tube, but the output tube will be supplied with bias voltage furthermore through the 2.2M and survive

Larry

thank you once again!

rockstah · Post by **rockstah** » Thu Nov 09, 2006 11:11 am

MacGaden wrote:I read in an earlier post that if the pot fails you have no bias, and your tubes would die. Quickly. Added benefit: Same sound as without it on 10.

Could someone sum up this latest version of he PPIMV, and maybe draw a schematic for it ?

like this!

from the caps on board red, right lug - front side of pot( closest to chassis),
black right lug back side.
sheild grounded to left lug.

from pot, center lug, red front side ( closest to chassis), to v6 and v7
from pot, center lug, black, backside of pot , to v4 and v5
shield grounded to left lug

used a 2meg resistor and 220k in series to make up the 2.2m resistor
2.2meg center and left lug back side of pot
2.2meg center lug and left lug front side of pot

rockstah · Post by **rockstah** » Thu Nov 09, 2006 8:48 pm

i thought i should post this PPIMV clip. recorded late last night.

using the post phase inverter master type 2 - using a dual 250klin pot -
sylvania long plates in the pres and jj e34l's outputs.
Strat with a darkburst with an A2 magnet in the bridge and a dimarzio vintage 54 in the neck

this was recorded at 2am - everything dimed - master at 1 - (bedroom level.)

please excuse the performance on it. i have been sniffing alot of solder lately.

http://www.soundclick.com/bands/songInf ... ID=4647605

comments welcome!

Mark

novosibir · Post by **novosibir** » Thu Nov 09, 2006 9:24 pm

Hey man

That really sounds killer - nearly unbelievable, that this sound could be realizable with the master merely set to ONE

You meant ONE - and not 1 o'clock - right?

And absolutely no RF artifacts audible in the sound

Although from about 1:30 onwards I could hear a slightly fizz in the tone, but though don't believe, that's been RF

You may name it 'Larry's PPIMV'

I'm proud on you, Mark! You did it great and made it sound killer

Larry

rockstah · Post by **rockstah** » Thu Nov 09, 2006 9:27 pm

novosibir wrote:Hey man

That really sounds killer - nearly unbelievable, that this sound could be realizable with the master merely set to ONE

You meant ONE - and not 1 o'clock - right?

And absolutely no RF artifacts audible in the sound

Although from about 1:30 onwards I could hear a slightly fizz in the tone, but though don't believe, that's been RF

You may name it 'Larry's PPIMV'

I'm proud on you, Mark! You did it great and made it sound killer

Larry

thank ya sir!

i was very impressed with it - no Parasitic O and it doesnt even happen when you turn it up either! yes it was ONE - bedroom level.

my "'Larry's PPIMV" rocks!

thanks for everything you do Larry!

Mark

Tone Slinger · Post by **Tone Slinger** » Thu Nov 09, 2006 9:35 pm

Sounded great man ! It sounded like you had the amp cranked. The "Somebody get me a Doctor" lick was right on. Was that really recorded with the master on one ?

rockstah · Post by **rockstah** » Thu Nov 09, 2006 9:36 pm

Tone Slinger wrote:Sounded great man ! It sounded like you had the amp cranked. The "Somebody get me a Doctor" lick was right on. Was that really recorded with the master on one ?

bedroom level. i recorded it at 2am in my apartment.

if u listen close you can hear my guitar acoustically in the room.

Tone Slinger · Post by **Tone Slinger** » Thu Nov 09, 2006 9:47 pm

That's the Circuit I'm gonna use when I get my 69 kit ( as well as get the extra's to convert to 12 series spec) Thank's for that clip.

robert · Post by **robert** » Thu Nov 09, 2006 9:47 pm

Hi Mark,

sounds great, my compliments!
Did you use a dual log. or a lin. taper pot?

Regards

Robert

rockstah · Post by **rockstah** » Thu Nov 09, 2006 9:49 pm

Tone Slinger wrote:That's the Circuit I'm gonna use when I get my 69 kit ( as well as get the extra's to convert to 12 series spec) Thank's for that clip.

there ya go! is why i posted it - i had the other master that has the 220k's on the board in place and uses a 500k dual pot and it didnt even sound as good to me here playing it.

its a dual 250k lin pot.

rtcook · Post by **rtcook** » Thu Nov 09, 2006 10:34 pm

Mark,

I know you like the PEC pots, but they don't have a dual 250K linear pot. What brand did you use and where did you get it?

This PPIMV has come about at a great time. I am just putting together my 69 board and I have the dual 500K setup with the 430K resistors in place of the 220K ones. If I am reading this correctly, I can just use this dual 250K pot and put in some 2.2M resistors in place of where the 220K ones originally were? Sounds too simple. Did I miss something?

Thanks,

Roger