Larry Grounding

[joesatch]

Does anyone have diagrams of this? There are several threads online but all are dead when i click on the image. 2204 build

[RadioComm]

From personal www search, here's couple of Marshall links:
https://www.thegearpage.net/board/index.php?threads/69-73-marshall-superlead-larry-grounding-scheme-diagram.2196688/
https://www.thegearpage.net/board/index.php?threads/good-grounding-layout-for-jcm800-2204-style-build-larry-or-star-ground.1821309/

Saw @pdf64 and @HotBluePlates as members on one of the threads at www.thegearpage.net

Also got some results by searching directly in this forum...

Hope this helps... ttfn

[joesatch]

Thanks well i guess this is the best i can find. Not a great shot but some interesting things here. The master and pre grounds are isolated from the tone pot grounds.  The heater CT is grounded to the input jack? huh?

[Willabe]

The master and pre grounds are isolated from the tone pot grounds.  The heater CT is grounded to the input jack? huh?

Who is this Larry?

It may work, but it doesn't make any sense.

Someone just posted here that they learned from Doug, to ground the heaters at the input jacks, I don't recall seeing Doug do that? Maybe he did? 

[joesatch]

The master and pre grounds are isolated from the tone pot grounds.  The heater CT is grounded to the input jack? huh?

Who is this Larry?

It may work, but it doesn't make any sense.

Someone just posted here that they learned from Doug, to ground the heaters at the input jacks, I don't recall seeing Doug do that? Maybe he did?

uncle Doug from youtube? I dont know Larry either . Maybe he's Doug's cousin

[Willabe]

Someone just posted here that they learned from Doug, to ground the heaters at the input jacks, I don't recall seeing Doug do that? Maybe he did?

uncle Doug from youtube? I dont know Larry either.

No, I thought he meant our forum host,  Doug.

Maybe he's Doug's cousin.

[sluckey]

Larry is Darryl's brother. He also has another brother named Darryl. The trio is about as smart as a rock.

[Willabe]

Why do you want to use Larry's grounding, when you don't know who he is or anything about him?


 

[Willabe]

Larry is Darryl's brother. He also has another brother named Darryl. The trio is about as smart as a rock.

"And this is my other brother Darryl."   

[acheld]

No, no no.   

That was Larry!  from Larry, Moe and Curly.

[thetragichero]

paging dr howard, dr fine, dr howard?

[joesatch]

All kidding aside. The Larry Grounding scheme is supposedly the best for Plexi's and JCM's to reduce noise. I just wish i could find a good resource for it. Everything i see online is a several year old thread with broken links.

[acheld]

The Larry Grounding scheme is supposedly the best for Plexi's and JCM's to reduce noise.

Not sure I would agree with this statement.   I am sure it has worked for someone in their build, but don't generalize. You could probably make it work. . .

I just wish i could find a good resource for it. Everything i see online is a several year old thread with broken links.

This, in itself, should tell you something.

Honestly, do yourself a favor and read:  http://www.valvewizard.co.uk/Grounding.pdf     Merlin is a "real" (as opposed to Larry Fine) engineer doing this stuff for a living.     Then, study Doug Hoffmans build documents for his Plexi's.   His grounding scheme incorporates many, but not all, valvewizard concepts.   Doug's scheme has worked well for decades.

[PharmRock]

I've got a JTM45 build that at the moment is basically a pile of parts on my bench waiting to be assembled.  Over the past couple of months I've done some research on various forums regarding this circuit and potential mods, and also came across the "Larry" grounding scheme.  Seems that the Larry scheme started way back in 2009 or so on the Metro forums, where Larry ("novosibir") provides some of his rationale.  Reading through all the threads, a lot of people swear by how quiet the amp is using this scheme.  For many of the threads, a lot of the images are dead links, but I've found a lot of images doing a google search on "Larry Grounding Metro".

Having said all that, a lot of what is mentioned in the "Larry" scheme seems to be very similar in principle to what is covered by Merlin and Aiken.  The only really weird thing about the Larry scheme seems to be grounding the heater CT at the input jack ground point. 

I wonder if a fair amount of the reduced noise from implementing this scheme is actually do to other factors that are implemented when the grounding changes take place, such as tidier wire routing, shielded cable, etc. 

Last spring I built a 1987/2204 that used a ground bus for the preamp section tied to the input, similar to what several people on this forum have posted (e.g. see Sluckey's Dual Lite and Phoenix pics).  I also implemented elevated heaters.  The amp is remarkably quiet at idle. 

[pdf64]

Several, or even multiple connections between circuit 0V and the chassis, and relying on the chassis as a 0V conductor, seems a bit haphazard to me.
A single 0V to chassis connection, with a single 0V wire conductor and all soldered connections to it, seems a better engineering solution.
Mike at Modulus has drawn a layout showing how that might practically be implemented on a Marshall type amp build.

[PharmRock]

Here's another image that may help....shows the various ground points and what goes where.  First post in the thread.
http://forum.metropoulos.net/viewtopic.php?t=31323

[joesatch]

there are some weird things that's doing. Grounding the volumes to a normal spot but then Grounding the tone pots to the power section Cap can but also to the speaker jacks? Grounding the heater CT to the input jacks?  so weird

[Willabe]

Having said all that, a lot of what is mentioned in the "Larry" scheme seems to be very similar in principle to what is covered by Merlin and Aiken.  The only really weird thing about the Larry scheme seems to be grounding the heater CT at the input jack ground point.

There's more than that, he has tone pots grounded in a different place than the volume controls, they should be grounded together.

And he has the speaker jacks grounded to the tone pots.

And he has 5 chassis ground connections. Like pdf64 said, the less chassis connections the better.

[pdf64]

The heater connection is just a reference, no current flows, it could be anywhere that isn’t too noisy, really.
It’s a totally different thing to, eg, the HT winding CT.

[PharmRock]

There's more than that,

I was mainly referring to the general principle that Aiken describes on his website, where one would have multiple ground points throughout the chassis and physically separate them on the chassis "upstream" from one another at a distance that minimizes ground loops: "If more than two star points are used, the additional points should be physically located between the output stage star point and the first preamp star point, and should be located on the ground terminal of the power supply capacitor used for decoupling of that particular stage." (Aiken)

Certainly no expert here, but certain aspects of the Larry scheme seem similar to what I've been trying to educate myself on via Merlin's books and other sites/forums.  But some of the implementation is definitely not in alignment with the resources either.

It begs the question as to how he came up with the scheme.  While there's some aspects that make sense, others don't.  Wonder if he just "played around" with different ground points for different sections and somehow stumbled upon a "magic formula", at least for the plexi-style circuits anyways. A lot of builders who've implemented it (at least the ones posting about it) swear its the quietest they've had. 

As for me...I'll go with 1) what I know works in my experience and 2) what is supported with reliable resources (e.g. Merlin/Aiken/this forum).

[Willabe]

The heater connection is just a reference, no current flows, it could be anywhere that isn’t too noisy, really.
It’s a totally different thing to, eg, the HT winding CT.

Fine, but why would I want to run a PT CT wire all the way across the chassis from the PT end to the input jack?

If it makes no difference, then why not keep heater CT wire as short as possible?

Not very practical.

[Willabe]

I was mainly referring to the general principle that Aiken describes on his website, where one would have multiple ground points throughout the chassis and physically separate them on the chassis "upstream" from one another at a distance that minimizes ground loops: "If more than two star points are used, the additional points should be physically located between the output stage star point and the first preamp star point, and should be located on the ground terminal of the power supply capacitor used for decoupling of that particular stage." (Aiken)

Well, he says; "If more than two star points are used...", indicating a less preferable option. And; "... should be located on the ground terminal of the power supply capacitor used for decoupling of that particular stage." The tone pots and volume pots should be grounded with the same B+ filter cap that feeds that tube. He split them so there not on the same filter cap. And Aiken makes a strong point on dealing with the OT speaker jack ground wire. Larry has the OT grounded with the tone pots, strange. OT secondary has the most current in the amp.   

It begs the question as to how he came up with the scheme.  While there's some aspects that make sense, others don't.  Wonder if he just "played around" with different ground points for different sections and somehow stumbled upon a "magic formula", at least for the plexi-style circuits anyways. A lot of builders who've implemented it (at least the ones posting about it) swear its the quietest they've had.

Very well could be. 

[joesatch]

It begs the question as to how he came up with the scheme.  While there's some aspects that make sense, others don't.  Wonder if he just "played around" with different ground points for different sections and somehow stumbled upon a "magic formula", at least for the plexi-style circuits anyways. A lot of builders who've implemented it (at least the ones posting about it) swear its the quietest they've had.

Very well could be. 
[/quote]

I'm guessing he jumpered sections until the noise stopped FOR HIS BUILD not necessarily applicable to the circuit or other's builds..

[darryl]

Larry is Darryl's brother. He also has another brother named Darryl. The trio is about as smart as a rock.

Hey! Stop picking on my brother's brother.   

[joesatch]

I'm implementing this grounding scheme. Doesn't feel  right running the cap can ground across the chassis but we'll see

[pdf64]

… OT secondary has the most current in the amp.   
…

The 0V connection for the OT secondary’s common is just a reference, ie no load current should flow there.
Due to the voltage sample for the feedback, there will be a tiny bit of secondary current there though.

[Voxbox]

My Name is Larry by Wild Man Fisher.



I heard this on John Peel on BBC Radio1 in the 70s and have never forgotten it for some reason...........
 


Cheers, VB

[sluckey]

...

[joesatch]

i dont know much about the grounding scheme, folks call it Larry. Maybe it was named after Larry Hagman?

[Voxbox]

...

Now I know what y'all are on about 
Never saw this in the UK.

[shooter]

Never saw this in the UK.

Here In farm country MI, it's a normal occurrence to run into one of the brothers at the beerbaitngas