Metropoulos Forum

Hi guys.. I have a 90% built 12XXX that has already been grounded using the normal locations provided by Metroamp. I have been reading about "Larry Grounding" and I would like to do this if possible without alot of work. My pots are the assembled Metro set that have the buss wire ground across all pots. Should I keep this setup and just ad a ground from the pot terminal to the appropriate position on the chassis or should remove the "terminal to buss wire" connection on each pot and go direct from pot to chassis? Thanks for any input.

BTW.... I have the V1, V2, 32uf board cap, and the bias cap grounds going to the 2 lugs on the extra 12ax7 cover plate screws.

wrea398 wrote:My pots are the assembled Metro set that have the buss wire ground across all pots. Should I keep this setup and just ad a ground from the pot terminal to the appropriate position on the chassis or should remove the "terminal to buss wire" connection on each pot and go direct from pot to chassis? Thanks for any input.

The "back of the pot" grounding can cause ground loops(the pot back is already attached to the chassis). It would be best to elevate the buss wire up above the pots? At the very least the volume pots should be separated from others.

wrea398 wrote: BTW.... I have the V1, V2, 32uf board cap, and the bias cap grounds going to the 2 lugs on the extra 12ax7 cover plate screws.

The idea of all of this is, that starting with the first preamp tube certain voltages/currents are very small, and become exponentially larger as you move down the chain. You should follow the grounding points as indicated.

Thanks VH. My board grounds are all grounded to the extra 12ax7 hole cover plate right now. They can easily be desoldered and moved. All the other grounds listed in the Larry setup wont be an issue to do it. On the pots, I will just desolder the buss leads and run wire to thier respective locations. Thanks for the info.

vh junkie wrote:

wrea398 wrote:My pots are the assembled Metro set that have the buss wire ground across all pots. Should I keep this setup and just ad a ground from the pot terminal to the appropriate position on the chassis or should remove the "terminal to buss wire" connection on each pot and go direct from pot to chassis? Thanks for any input.

The "back of the pot" grounding can cause ground loops(the pot back is already attached to the chassis). It would be best to elevate the buss wire up above the pots? At the very least the volume pots should be separated from others.

wrea398 wrote: BTW.... I have the V1, V2, 32uf board cap, and the bias cap grounds going to the 2 lugs on the extra 12ax7 cover plate screws.

The idea of all of this is, that starting with the first preamp tube certain voltages/currents are very small, and become exponentially larger as you move down the chain. You should follow the grounding points as indicated.

My 12000 with the stock grounds is noisy with hiss. That's the deal though. That's how they all sound done that way. It's not 1968 however, Larry those grounds, and get rid of that bus wire on the pots. With the pots grounded on the front of the chassis already as Junkie has said, the bus wire on the pots sets up 5 potential ground loops alone. Spreading out the voltage within the chassis will do wonders.

hiss is not a ground noise.

i don't know i have been around the block with changing the grounds( for years now) from what marshall did and have resumed doing it as they did.

the part that is effected by grounds would be ghosting and not hiss unless that hisss sounds like a ground noise to you. (buzzzzz)

hisssss is one thing.... buzzz is another which would lead to a bad ground/bad grounding scheme, but a gain the only reason for me to change the grounding scheme would be ghosting.

further more to go over board in a 2 gain stage circuit like a plexi is over kill. start worrying about grounds when you have 3 and 4 gain stage circuits.

thats my 2 cents,

Mark

I say go Larry. Even if the stock scheme can work OK and not have much ground noise, to my ears a full-on Larry-style grounding scheme makes the amp sing more effortlessly and have even more fluidity. I say this because I had a 45/100 with a stock (almost) grounding scheme, where I had trouble with ghosting. I changed it to a Larry grounding scheme, and not only was ghosting greatly reduced, it also sang even more cleanly and fluidly.

Do not read that as saying it changes the sound of the amp - the overall character and voice of the amp is exactly the same, it just sounds like an even better version of the same amp.

However, it does not remove the hiss that will be inherent to the amp.

I believe that I will leave it "as is" and will see what happens. After I fire it up, I may decide to only re-do the pot grounds as they are easily changed, just to see what happens. I am doing a '69 S/L as we speak and will do the Larry grounding on it. The Marshall hiss does not bother me as I have 2 early Superleads, and yes, they do hiss a bit. It's normal to me.

One man's hiss is another man's buzz.

But seriously, we don't want to disinfect everything about the 1959 circuit that makes it so potent! All these tweaks might leave us in the same place the Floyd Rose left the guitar in the 80's: an inbred tone nightmare

Agreed. My 69-70 Super lead hisses a bit but my "Decimator" noise supressor takes care of it without changing the tone much if any....

vanhalen5150 wrote:One man's hiss is another man's buzz.

wrea398 wrote:Agreed. My 69-70 Super lead hisses a bit but my "Decimator" noise supressor takes care of it without changing the tone much if any....

vanhalen5150 wrote:One man's hiss is another man's buzz.

Best pedal I ever bought. Does wonders on a Plexi.

Strat78 wrote:But seriously, we don't want to disinfect everything about the 1959 circuit that makes it so potent! All these tweaks might leave us in the same place the Floyd Rose left the guitar in the 80's: an inbred tone nightmare

Who cuts your hair Strat78?

How does your new amp compare to the last without the Larry grounding.

vanhalen5150 wrote:

Strat78 wrote:But seriously, we don't want to disinfect everything about the 1959 circuit that makes it so potent! All these tweaks might leave us in the same place the Floyd Rose left the guitar in the 80's: an inbred tone nightmare

Who cuts your hair Strat78?

How does your new amp compare to the last without the Larry grounding.

Done fall out I reckon.

Anyway, with the grounding it seems less squirrelly and there is no hum whatsoever, just allot of buzz from the fluorecent bulbs I think.