Ground Schemes | Part 1 : The Ideal vs Good Enough vs Vintage Marshalls

This might ruffle some feathers. So be it.
Merlin's excellent site:
www.valvewizard...
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[@SkyscraperGuitars]

I've NEVER heard it explained this way... Everything you said makes sense and you put it into terms and diagrams that make it easy to understand conceptually. Thank you for taking the time to break it down for guys like me who aren't amp techs... I'm slowly starting to understand how these circuits work and why some are good and others are better.

[@shanedolman1368]

Excellent introduction to a massively important and often overlooked subject. Great stuff lyle!👍😀

[@theguitaramptech]

Thank you for this excellent explanation of Grounding schemes, Lyle. I appreciated your differentiating between IDEAL and PRACTICAL.

[@biggstile]

Thank you for your efforts to be a trusted resource for people to keep quality amps alive.

[@artysanmobile]

Your hitchhiker metaphor is an excellent way to explain AC coupled audio amplifiers to the lay person, who has no need to know more.

[@kwgm8578]

The hitchhiker metaphor sounded good, even to this old, retired electrical engineer, who, is trying to relearn how this stuff works (, but often doesn't.) You are a most patient teacher, Lyle. Thank you for sharing the bench with me.

[@scottdunn2178]

Having just turned 55, it makes me feel old to remember back in 80's buying JMP or JCM800 heads for $400 give or take. Early 70's metal face for $750, and plexi's for around a grand. 3 grand for a JCM800 reissue? No thanks.

[@scottdunn2178]

@Nicko Lps Even figuring in inflation... Marshalls were much cheaper then than they are now. People and the market have gone crazy about these old amps that just doesn't justify the outrageous prices some of these amps are fetching nowadays.

[@jrg770]

I bought a used 2203 JMP... JCM 800 master volume (before the logo read JCM 800) for $395 Canadian in 1993 lol. I sold it for around $500 some years later. And today ? The first one that appears at reverb is $4,600 Canadian lol. Gas was roughly .50 now 1.15.

[@scottdunn2178]

@@jrg770 Yes, a 2203 is the exact same circuit... whether a JMP or JCM800. Just the head cabinet style is different. I wish I had every single plexi or early 70's I could have bought back in the day dirt cheap... everybody in Phoenix played metal, so everyone wanted a Master Volume Marshall with a stomp box in front.

[@hkguitar1984]

I hear ya Sir. When I was 16 years old I'd saved up enough to purchase a brand new Fender Twin Reverb, the year then was 1976. I still have that Twin Reverb, it cost me $400 brand new. At the time I'd wanted either the 50W or 100W Marshall sitting next to the Twin at the music store but I didn't have enough money for the head and then a cabinet. Yeah, I do wish I'd have kept all the gear that has been through my hands over the years.

[@deanallen927]

In '84 I bought a '73 Major for $689 with what I later found were "Blackmore Mods" or similar. Now anything any good that is not new is considered "vintage" and priced way too high.

[@newtoneer01]

I found this the best explanation of this subject on KZbin. Your extensive knowledge of amplifier circuits added to make this superb viewing for any amplifier nerds.

[@soapboxearth2]

This was very helpful in a trainwreck express build I did. I also like the placement of the 100r on the v4. There's always something to pick up in your videos!

[@GrrumpDaddo56]

Many thanks for taking the time to give us this info in and amongst your repair work !

[@JEmilioJNava]

This is solid gold in its YT video form.

[@leiferickson3183]

Wow! This is a very clear description of how grounding works. Awesome! Content like this is pure gold for anyone who is wanting to really get what is going on in an amplifier. Keep it up - it is very entertaining to watch too.

[@Rico_G]

Thank you. You've definitely cleared up some of the confusion floating around in my head. It is very easy to get into and maintain a "ground is a ground" mindset. I've always had trouble with wrapping my head around why one ground scheme would be superior over another. This video helped more than any other I've seen.

[@IL2TXGunslinger]

Such a great episode for many reasons - thanks for the links. On the alpha pots, I find it incredible that somehow in this day and age people still hold on to brand loyalty as yet another “identity”. While there are a tiny number of exceptions - I find that I must continually evaluate products I receive for their actual quality and not their perceived quality. It’s constant now - as companies are bought and sold - along with trademarks etc…

[@Mikexception]

Just my last experience with my MIDI keyboard shows that keeping with vintage pots may be good idea. To old potentiometers we need only to make conservation, not replacement. I use today still my parents radio with double potentiometer and whole my life I cand remind any crack form it. It works still perfect and I have no idea how many times it was turned but sure thousands . Never dismanted It was produced in 1939. Also all switches work. On other side my MIdi keyporard was produced in 2004 in China and there are assembled 10 potentiometerswhich I had to treat few times with lubrication and two of them controlling linear pitch which I used may by ony 50 times totaly broken - I managed to dismantle them and repair them with conducting compound My mixer using may 24 "new" potentiometers made in Chia in 2004 all are already full of cracking sounds. t I replaced volume potentiometer in my Bell 60 years old tube amplifier but only on reason that stereo pair weren't exactly following each other. No cracks with turning anyway.

[@dan_perry]

I've always used the Alpha pots, easy to rebuild and generally their tolerances are pretty spot on plus they have a lot of odd ball values.

[@russellesimonetta3835]

Grounding , understanding it, was my biggest challenge! Love your channel,, I'm learning tons from you.

[@markcaruana7233]

This is the best explanation and visual for grounding that I have seen. From watching/subscribing to your channel I can realize just how particular and precise your standards are to the world of valve amps. I am the same way and as a hobbyist amp builder/tech I constantly look for the best practices using years of electronic theory applied with common sense to design, prevent and solve tough noise issues. Again thanks for the bullseye. Mark

[@theoldbigmoose]

This tutorial is THE heart of getting the noise out of amps... corporate sent us to month long courses to learn how to design proper ground systems in avionics.

[@davidfilley3984]

Thank you for your professorial analysis of this subject. I am learning about building amps and the grounding issues (especially based off marshalls) and your channel is incredibly helpful and I will site you as an invaluable resource, thank you thank you thank you! Cheers from Maine.

[@rodprod8522]

love this channel - just found it and really appreciate no nonsense and fantastic info. Thank you!

[@charlieplate9687]

Years ago when I was a runt, in an attempt to make my first diy super lead quieter and more stable I switched to a Larry grounding scheme . Whilst it was in fact better in those regards , but I no longer heard or felt what I wanted from the Marshall circuit . Whereas I generally prefer a properly designed ground scheme , there is no accounting for taste if you like “All the buzzes” lol. Some people would also rip out all if those beautiful Phillips capacitors and iskras and pihers and shotgun blast the circuit with metal film resistors and orange drops . Great video as always Lyle , always appreciate your experienced insight

[@sgt.grinch3299]

My first electronics class. So much to learn.

[@crucifixgym]

What an amazing and concise breakdown, and a beautiful amp at the end 🔥🔥🔥

[@hallanvaara6106]

I did this to my TAD Super Lead. I couldn't get all the info I neededfrom this video so I had to study Larry's ideas too. Anyway, the amp is reasonably quiet now. So thanks for the knowledge!

[@jasonktong1]

Really great video Lyle, superb.

[@tedmich]

Nice video! I believe Randall Aikin also soured on the PEC pots since they cost $$, and do get noisy but couldn't be easily cleaned.

[@hardball107]

Thanks for the video. I like to build single ended practice amps for the kids and have been very lucky with noise levels and tone. I just built a 4 watt amp head in an ammo can for travel and camping use with a 6AQ5 and a 12AX7 diode rectified and used a bus bar grounding scheme with the power grounds at one point and the signal grounds on the bus bar. I guess I could have done it simpler with just chassis grounds but I'm just a hobbyist and it worked. I love the fact that I'm always learning, thanks for the help.

[@nickrundall]

Great explanation Lyle - absolutely hooked to your channel now! Thanks for the knowledge

[@stuartukguitarampguy5830]

Interesting stuff thanks. Just finished chasing hum on two vintage Marshalls!

[@billmckenna7056]

Nice discussion I learned a bunch. I have a 74 Ampeg B15 that I recently capped and it developed horrible hum after I went away from can cap to internal. I clearly made the mistake of merging ground nodes onto one bus of all the filter caps. I fixed it by floating ground on the input but I still hear some hum in the background. Think with this video and the pdf from the valve wizard I'll get it sorted properly and be able to go back to the factory input jack style. Agree with your comments on Alpha. I have used them for years before recently cutting to CTS and noticed the curve on the A taper kind of sucked. Glad to hear I'm not going nuts :)

[@richclayton5785]

Actually, I have read his book…honestly most of it over my head. So this is a nice review.

[@tracyc7813]

I use Alpha pots quite often myself and I have no complaints. They are fine. What you are doing here is a really good thing. Thank you. :o)

[@jernejkurincic9050]

I was so happy to find this video. I have read Valve Wizzard's essay quite some time ago and recommended it to many, but never seen it mentioned on YT. People would be just copying old designs, which were clearly compromised (eg. pot casings ground bus ). Also, I've always wondered how to put it in practice. My own designs were made on its base, but what to say about others'? I still tend to use the chassis just for shielding (having all jacks insulated) and run decent gauge wires instead (joining at the first stage filtercap negative).

[@judges69]

sad its getting hard to get resistors and capacitors now. i have a Marshall i am building but don't have all the parts yet. perfect timing for this grounding video for me. thank you

[@paulcargo4233]

I work mainly on old Ampegs for my own use. Not only is the chassis area so small and its like building a ship in a bottle but there are a bunch of bogus schematics all over the internet But the the biggest issue is the grounding scheme and its variations from amp to amp. Please include early 60's Ampegs if you continue this series. Thanks

[@PsionicAudio]

'60s Ampeg grounds are just random from what I can tell. Depends on how drunk the assembly line was that day. Seriously, folks, Ampegs have the worst wiring.

[@barnyardstory]

@@PsionicAudio Sunn is in that club too.

[@gutsanglory1]

HAHAH...Whipping it out and measuring....LOL. Too funny. Very interesting topic, way more than I know about it already. Amp is looking very clean and organized. Cheerz!

[@gregorypinkowski7809]

Thank you for sharing, this is gold. Makes me wonder what Nik does in his clones. I've worked on few Marshalls. But...I started as a live sound hum-head so I take noise reduction to heart.

[@jett7530]

Great conversation about ground practices. It took me a few experimental layouts for me to learn some of the things you are discussing to get noise down, I just didn't understand things as well as I could have at first. Also I have been using CTS pots in my last few amp builds, but I have had a number of issues with them, many you discussed. I was considering trying bourns, but maybe I should just try a bunch of alphas. Thanks you for your channel.

[@GL64]

I'm gonna go ahead and hit like before I even watch it. I'm a noob but a believer in good grounding. Been looking forward to this.

[@TheAxe4Ever]

All great information. But the very last little bit on this video is absolute gold! It’s those types of “look how smart I am” attention seekers that keeps me off of various forums. They have no idea about level of conversation when you try to just quickly explain something without getting too far into the weeds with unnecessary terms that have nothing to do with the context.

[@faustoneamps]

Thanks for another great video Lyle, I'm learning a lot from you! I've noticed that you observe polarity on the coupling caps, I would love a video on that when you have the time. Greetings from Spain!

[@PsionicAudio]

¡Gracias! I do when the outer foil is marked. On very finicky circuits I will find the outer foil, but for most lower gain amps it doesn't make a huge difference. Until it does. ;) Note that Fender did it.

[@ashscott6068]

@@PsionicAudio I don't understand how the orange drop caps have the outer foil attached to a random leg in relation to the printing on the outside. It shouldn't be too hard to keep them in the same orientation through the whole process, so you can use the writing to find the outer foil. For some reason, the caps are getting all jumbled up, and then they need a machine to pick them up and orient them again so the machine that does the printing can find them. I guess it's because the machines are built separately with no thought for handing caps directly from one machine to the next. It's a shame, cus it definitely makes a difference if you accidentally get all your caps with the inner foil connected to ground vs the outer one. Or maybe they're consistent now. They weren't before, but I heard that Sprague doesn't make them anymore, someone else does

[@viktor86bt]

Very educational. Even stuff not mentioned by Merlin. How to make the best of these old amps without rebuilding them completely. I wish I could find amp kits designed with thought out grounding schemes instead of copied old vintage boards.

[@sstorholm]

I’ve never understood the idea of grounding everything to the back of pots, it’s a pain to do, it’s unnecessarily heating the pot, and it either creating ground loops or you’ll have very questionable grounds relying on the star washers under them. So why not ground it to a good solid ground instead, using a proper wire, and let the star washer handle the ground connection for the shell? These vintage cost cutting methods never ceases to amaze me, or am I missing something? Anyway, thanks for a very nice video, as usual, lots of good points and some new insights, I had never thought about the implication of ground currents, and especially the direction of them, moving them to a single point at the input is an interesting idea.

[@ThiagoSforcin]

Star ground is also a good choice for high gain amps, isn't that? I enjoyed a lot this video, great content and awesome explanation!! Keep on rocking!! Cheers from Brazil.

[@PsionicAudio]

Not really. Star grounding would only be perfect in a circular chassis design. The approach here is sometimes called a "localized star ground" or "galactic ground." IME it is superior.

[@Billywagner22]

I'm enjoying these videos Lyle.

[@Johnsormani]

What a nice lesson on ground schemes this is. Thanks.

[@johnwilliamson467]

Per the RCA red book (1941) raising the heaters off ground 45 volts does lower noise a good bit. Check with Merlin B. it is also in his books . Fine video to help many with these problem. Bravo

[@jimjewell2151]

ive got a Plexi kit amp that has been through 2 different builders before i wound up with it. ive been building my own amps (of my own design... i like the oddballs) for about 6 years now, and i started using Merlins Ideal ground scheme fairly early on. im having to practically rebuild this Plexi clone, and im definitely implementing these changes to the ground scheme.

[@csxblackmusic]

This series is AMAZING. THANK YOU.

[@markarita3]

35:09 "I have tried every brand of pot out there"...insert Beavis & Butthead reaction here. That amp will be so quiet, it'll have to ask you permission to make noise! Nice lesson Lyle.

[@tomh6000]

Lyle, these videos are great, really informative and accessible. I have a Hayseed 15 that you repaired/modded for the previous owner and it’s fantastic! Now I know why…. Please keep them coming.

[@PsionicAudio]

Thanks Tom! I remember that amp. Hayseed lived up to their name - one of the worst "commercial" amps I've ever encountered. Took a lot to undo the stupid. But it was worth it!

[@tomh6000]

I never had a chance to hear my Hayseed before you did the work, but you once called it “dangerous” in an email. Coming from you, that’s sobering. Now it’s one of the sweetest, quietest AC15-style amps I’ve ever played. The EF86 channel is just magic! I’ve been watching the development of the Excalibre 15 with great interest. After you’ve finished the prototype will you be posting info about possible ordering options?

[@Curranproducer]

I LOVE this video sir!!!! thank you for stripping back the snake oil, and getting this into my brain hole!!!! Snow Pants!

[@blainewhelan8289]

Nice discussion. I've built a 5e3 with this ground scheme and a Deluxe Reverb with a ground bus along the back of the pots. Both amps were much quieter than Fenders. If the grounds come to the right locations on the bus I don't see a problem with this method. There ishould be no current in the bus or through the chassis, so no buzzes

[@simonkormendy849]

I've always thought that the so-called Star-Grounding system was the best one to use in audio amplifiers, whether they were Tube or Solid-State, by Star-Ground I mean a grounding system where there's one ground-point on the chassis and then you have grounding wires radiating from it to ground connections on various circuits in the amp, the whole idea is to eliminate hum-noise caused by voltage-drops along ground wires, sure the wires usually exhibit very low resistance but that low resistance can still cause a voltage-drop.

[@buffdoc46]

Very comprehensive and helpful. Impressive for sure.

[@oldguy5381]

That board is very impressive, thanks for the looksee

[@AndyK.23]

Super interesting stuff! And it's great to know about the Alpha pots! Although, now I am sad because the Rockit Retro Plexi I have has the bus wire connecting all the pots.

[@PsionicAudio]

Lots of clones copy mistakes. Hint: Germino fixes this mistake in his amps. Greg isn't a copyer.

[@matthewridgeway9250]

Thanks for this. I think I understand. Share the ground for first two stages, and then the phase inverter and driver stage. I will review what you have shown as I go. I just bought a brass bus bar with eight screw terminals. I was goung to run all my ground wires to that, but now I have a clear directive. Try at best to eliminate/reduce ground loops, and bring the grounds per stage form output to input sequence. I was going to put this brass bus terminal strip between the mains transformer and the turret board. I will probably run three ground wires under the turret board behind the control knobs to that brass bus terminal strip. Then put the input ground next to the mains grounding wire from the IEC socket I will use, then add each other ground wire sequncially. Thanks for a great video. I will look into my build with even more vigelance as I go now. I am building a JTM45 with Hammond transformers and EL34s. I inirially was going to fit the plexi face plates, but I painted the chassis with hammer finsh paint in blue. Looks fantastic. Si I am not going to fit the plaxiglass now. Marshall didn't build it, so why pretend Marshall did? Making it my own. Anyway. Thanks again. Excellent video.

[@curtisprice9806]

THANK YOU SO MUCH FOR THIS INFORMATION!!!! LOVE THE CLASSIC AMPS!!!!👍👍👍😄

[@matthewf1979]

I take apart those 1M linear split shaft CTS pots for their wafers to throw in a solid brass shaft 1M audio case. I *HATE HATE HATE* modern CTS audio taper too. You’d think with all of the custom order “vintage taper” guitar pots out there that someone would do a custom J taper or regular linear custom CTS pots for amps. There’s just something about a brass shaft and ferrule that I prefer.

[@christophersambuco9414]

This is super interesting. Thanks for sharing your knowledge. And don't worry about me trying to show off how smart I am...I'm a dope. The whole grounding scheme thing is in many ways opposite to what I expect. I had in my mind that grounding to one star point with individual wires all going to that one point would be the best way to go. Maybe not.

[@jamiemascola6614]

The dark art of grounding. One of the most misunderstood topics in analog electronics. One point that I would like to add, that always helps me with my grounding schemes, is that conventional current flow is bass-ackwards. Electrons, in reality, follow the orthodox current flow principle. They flow from ground to source. So when considering schemes like chassis-drop grounding, try to imagine using the shield for your B+ rail, and not incurring noise from stray fields, cosmic rays, LED emssions, etc as a result. It seems ridiculous doesn't it? Well guess what... That's exactly what is happening. Use the chassis as a shield. Not as a conductor.

[@thomasbailey9605]

Yes--- stopped using PEC as well. Had many brand new that were scratchy.

[@mantas68]

Funniest thing I've heard all week: You calling potentiometer audiophile snobs "cork-sniffers". LOL! This might have been aided by the fact that my juvenile humor thought that you said "cock-sniffers" at first. LMFAO!!! Keep up the good work and thanks for posting these very educational videos. I'll admit, at my current skill level that a lot of this stuff goes over my head, but what I can understand is helping me to build a pretty sweet knowledge base for now. I keep most of my work under 24 volts, like pedals and such. With what I'm learning here I hope to eventually move up to higher voltage projects. :)

[@alancaldwell5029]

My apologies, In my earlier comment, I meant to refer to Your Excalibre 15 as a potential kit, not the Marshall. I would be very excited to have the opportunity to build Your Excalibre 15, as your kit, or even from a preferred parts list, schematic, and layout. Again, thanks for your great videos.

[@PsionicAudio]

Thank you but no, I will not be making any kits available.

[@goodun2974]

Worth noting that hum, buzz and borderline oscillations are always super-imposed onto the signal from the guitar, and therefore the beginning and end of every note is marinated in all these artifacts. A metal player might not notice, or care, but if you are playing on the edge between clean and dirty and want the amount of distortion to be determined by how hard you pick, getting rid of ground loops and extraneous circuit-generated noise is desirable. The first, self-taught, electronics repairs and mods I ever did, as a pre-teen, were replacing selenium rectifiers and filter caps in my dads' radios, and recapping his HarmonKardon hifi amp (5408 output tubes, similar to 6V6's), followed by modding my own portable record player, and uggrading it from a ceramic cartridge to a magnetic cartridge. If you want to see some really stupid grounding schemes, look at most turntables, vintage or modern: for lowest possible hum or buzz, the grounding or bonding of all of the metal parts ---- tonearm, platter & bearing, motor housing, and the power-supply ground if it has any motor-drive circuitry ---- should ideally be kept electrically separate from the audio grounds/shields of the phono cartridge, and the ground wire connected to the phono preamp or receiver chassis (the RCA plugs' audio grounds are typically isolated from the preamp/amp chassis by capacitors); but many turntable designs stupidly tie the audio ground to the bonding ground internally at one or more points,, making the phono pickup susceptible to hum, buzz, and RF interference (typically worse on one channel, usually the left channel, sometimes due to a jumper wire on the headshell wiring or a ground strap on the cartridge body itself). I've separated out the grounds on many a turntable being serviced, lowering noise and hum; and yet, I've seen vinyl junkies and turntable collectors on KZbin intentionally removing the ground wire and tieing the audio and bonding grounds together jnside the turntable, saying, and I quote, " I hate ground wires"! 🤔

[@joelbates87]

This was such a helpful video for me. Thank you for making this!

[@RecordingLounge]

Can we get an updated video Part 2 with the final product / demonstrating the Larry ground in a finished amp? Love your channel. You should set up a PayPal donate feature! People would donate!

[@PsionicAudio]

I've done several. After coffee I'll try to remember to put a link. If I forget, see the playlists for Marshalls. I don't feel right with a "tip jar" etc as I'm already paid for the actual work. The videos aren't my income. I don't want to seem crass or desperate.

[@GregoryHillSr]

Soaking this all in....👍

[@goevo1]

Thanks Lyle! There was a lot of great info there…it would have really helped me understand more clearly if you could have used a pointer to show the locations as you were explaining the connections that needed to be changed.

[@goevo1]

…@29:56 in the vid, I feel that pointing to the ground being discussed would be beneficial to quickly understanding it.

[@timmaa6469]

Larry = Helmut "Larry" Grohmann is his name. Larry Amplification his amp company. He is indeed brilliant. I have a Trainwreck Clone from him ... what an amp :-)

[@NoOne-sn2si]

Ha ha ha! Great title and so very accurate. Looking throughout Marshall's history, I think many of their great sounding amps came about because of sheer luck, because their engineering decisions are about as bad as Jaguar's. Lol!

[@chrisdelacerda4719]

Love the detail and the mention of the Valve Wizard. I am in the process of building a 5F1 Amp. I am curious how you would approach grounding this circuit. I am becoming a regular viewer and thanks for your insight! 😊

[@PsionicAudio]

The stock 5F1 has a pretty good ground scheme. While it can be improved, the improvement is almost theoretical. Almost. ;) Anyway, I don't have time to go into the changes right now but you can copy the existing Fender layout, but pay attention to separating the Va and HT CT grounds from everything else.

[@antonix_81]

thanks for this great video , i hope i will see more on this subject ....i probably made/make the mistake of the ground bus (like many dyers), preferring that solution and using a star point where i solder all the grounds, but honestly this makes more sense...i mean,i probably get away with that (or maybe my ears can't hear the noise 😁) but better to improve designs if possible👍🏻

[@christophersambuco9414]

I had to rewatch this because I'm about to try a one-off oddball mix and match type of build. I hope to not screw up the grounding too bad

[@MartinMacGill]

Great video! Thanks for information too as it looks like a black art at the best of times

[@wtipton]

Well, you just changed how I will build my next Marshall style amp.

[@tjminasi1442]

Good 25’ description without complex Math involved. Awaiting the next segment, then we can talk about this noisy ‘72 Musicmaster. It’s … dreadful but has potential.

[@imagemaker5150]

I own 2 Marshall amps. A model 1959 and a model 1987. These are not vintage 1960 amps. Both are from the 90's. I would be very interested in learning how to improve the ground scheme on these amps. Please advise how that's done if it's possible for a novice to perform. Thanks so much for your great videos. Looking forward to hearing from you !

[@jasonmcbride2737]

Lyle, I enjoyed this video and think you presented the info really well and made it easy to follow. I love Merlin's stuff...my copy of his book is well worn. I am about to re-read the chapter on grounding and will re-watch this to soak it all in. Thank you for sharing this information with us! Question: Marshall uses Cliff jacks for the outputs which isolates the jack from chassis and Fender uses standard Switchcraft jacks which are non-isolated. Does it matter or is one method better than the other?

[@PsionicAudio]

An isolated input with wired ground is the most controllable, but there is certainly nothing wrong with a metal frame chassis-tied Switchcraft. Basically, choose the jack method carefully and be mindful.

[@overtone85]

When I rebuilt my superlead from scratch 3 years ago I followed the merlin grounding to the letter. Without using the chassis as a buss. Just one point at the input jacks. It is super quiet. Unfortunately the PT (from a renowned transformer replica maker in San Diego) is buzzing a lot acoustically that it is slightly noticeable through the chassis/OT output. But it’s good enough for me, maybe one day I’ll replace the PT.

[@tonyduncan9852]

Rusty atart - but fine finish. Cheers. 😎

[@gregweber6237]

I have watched this excellent video multiple times and really appreciate the explanations. If I am seeing the ground points correctly, you have 5 grounds points...(#1) By the Input, (#2) By the Presence Pot, two more over by the can capacitors, and one at the wall voltage coming in. Is that correct that you have 5 total? It was very clear what you have connected to (#1) and (#2), and I heard you say you like to do the heater CT at the screen node. Which one are you calling the screen node, the one by the front or back of the amp? Could you please explain what exactly you have connected to nodes (#3) and (#4)? I am going to try this grounding scheme on a 68 Plexi 12xxx build I have just started. Thanks for this great content and all of your videos!

[@SeQFreQ369]

Excellently explained, thanks, just subscribed ;) Wouldn't mind one on safe, maybe even legal, though that never stopped any hobbyist amp builder I know, lol, "do-able at home without TIG welders" grounding in an aluminium... er... aluminum chassis. ;) Cheers.

[@npet6842]

Superb lecture . Thank you !

[@chrisdelacerda4719]

I am curious, what pieces of hardware like bolts,nuts,and washers do you use to mount components to chassis? And are you using something like loctite on ground points ? Thanks for all your help and awesome content ! Much appreciated!

[@Satchmoeddie]

CTS went to **** about 20 years ago. CTS lost a whole boatload of money from legal actions due to a batch of bad automotive pots used to control the throttles in a bunch of GM vehicles. Having your car lunge into a building or out into traffic is not a very good thing. Mallory used to make good pots, as did Stackpole, TRW, CTS, Allen Bradley, Ohmite, Clarostat, Centralab, RCP (Canada), Alps (Japan), Rohm (Germany). I think Tyco bought up 3 or 4 of these companies before they became TE Connectivity. I know have I forgotten at least half a dozen other old names, all of which are long gone now. No more competition means they don't have to try to make quality products anymore.

[@jeffkellogg76]

I’m putting a StewMac ‘62 BRIT-PLEX 45w amp kit. I read, skimmed, the article that you referenced at the start of this post and I am considering using a dedicated ground lug especially for the power cord . I have never built an amplifier so I’m wondering if this is something that you would recommend.

[@steakncheddar]

If you were using a Marshall Chassis, with a Marshall filter capacitor layout, and this amp was going to be a little higher gain than a jcm800, would there be any benefit in trying to implement a bus bar approach instead of the chassis approach? The Marshall cap layouts are pretty far from where the bus bar would be (I imagine it close to the pots but on the board instead). It seems it would get messy, for example going from the preamp cathode to the preamp filter cap then back to the bus bar would be wire doubling back and forth, would that make the effort meaningless?

[@PsionicAudio]

Yeah. What I've shown here is the best option with the stock chassis and filter cap locations.

[@dlamoro1]

Can you please post a schematic of you ground scheme? I have a very original 1970 SLP. I would like to implement your grounding scheme in this amp. This appears to be a better method than the Larry method. I don't se a follow up for this particular video.

[@lespaulnmarshall]

Amazing video, Lyle! For me this raises a question. With Larry grounding, as you reference in the video, you state that you almost completely agree with his findings. Now, I built an amp with Larry grounding (JTM45), but with a multi section can cap for the PI and preamp, so there is a shared ground connection for the PI and V1 and V2. Does it matter much whether you connect this ground together with point number 3 (speaker jack, presence pot and mid pot) or point number 2 (V2 cathode and volume pots)? Or would you perhaps just connect them all together in this case to one big ground point?

[@PsionicAudio]

I would wire things to their cathodes and have the cathodes go to the cap neg, then a wire right by the input jacks.

[@lespaulnmarshall]

@@PsionicAudio only saw this now! Thanks!!!

[@hrsey71]

great info! im diving into my 76 JMP 50 watt lead, and trying to make it sound as good as it can be without molesting it too much. what is your take on components? like cap brands/types and resistor brands for replacement?

[@jasonktong1]

Lyle, I often come back to this clip. Thanks again for posting it. How thick would you recommend board traces be for the ground in the single ground at input method? I.e the John Suhr example that you mention. Assuming 2Oz copper.

[@PsionicAudio]

Gets complicated. I’ll PM you when I have a little bit of time.

[@williambock1821]

Great tutorial! If a chassis is fairly small or just plain small,like 10x5 inches, would it make much difference if the phase inverter was grounded via a buss along with the preamp stages towards the input?Like 2 triodes for preamp and a single triode phase inverter? The power tubes/caps have their own buss towards the transformer. I have it grounded that way and don’t hear a lot of noise but it’s hard to tell if the noise I do hear is because of the p90’s in my guitar(which does quiet down when the guitar is at a different angle. The amp isn’t noisy ,generally speaking but a second opinion from someone who actually knows what they’re doing would certainly be of value! Thanx!

[@nathanbouton6700]

There is the Tao that can be spoken and the Tao that cannot be spoken.

[@Beizeiten78]

Sorta off topic and late to the game, but can a solid state Marshall, like a Lead 20, have a speaker jack added that grounds at the chassis, like an old Fender? Or does a solid state amp need to have an isolated output jack? Thanks.

[@diedraak1]

Great work Lyle as always!!! Question: what are the two grounds to the left of the amp (not the safety earth) One is near the power switch. The other is near the bottom left capacitor? Thanks!!!

[@PsionicAudio]

Thanks! Bias ground node and reservoir/HT CT ground node.

[@deanallen927]

What's your opinion of the "star ground" I've read a little bit about? where everything possible is grounded to one spot? New subscriber, REALLY like the videos.

[@PsionicAudio]

Thanks! Full star grounding can work but it can also introduce new issues. It usually leads to long ground wire connections and a CF of wires. Much better in theory than in practice. Ironically, the best way to achieve it is with PCB, which makes people turn their noses up.

[@TheStimpy60]

Man I’ve learned a lot from this video. Thanks again Lyle. Do you think I could do something like this on the Mojotone 18 watt Marshall combo amp kit I am going to build for a friend ? Your thoughts would be appreciated. I would like to avoid soldering that bus wire to the back all the pots- and you’ve given me a great excuse.

[@PsionicAudio]

You can use these principles. The 18W layout is different. Avoid the bus wire on the pots. In the next few days I'll have part 2 up with the AC15-derived Excalibre 15. And the AC15 is laid out similarly to the 18W.

[@TheStimpy60]

@@PsionicAudio - many thanks- I’ll look forward to watching it. I like the way you present the more esoteric things clearly with seriousness and humor.

[@joeltunnah]

The pot cases *should* all be grounded... BUT... all the pots and jacks should be "floating", ie insulated from the chassis, which most guitar amps never bother with. Good hi-fi amps do. Otherwise you're making multiple ground points to chassis at each jack/pot. Not good.

[@cloudconnect]

I'll answer part of my own question, here, after doing some further research. It would be nice if this type of info was more available to the consumer or repair guy so we stop doing things wrong. It seems that the regulation to keep the ground wire short as possible, and on its own fixing post, is so that it never gets disturbed or damaged. A shorter wire is conveniently out of the way. The bonding post being on its own, is likely to ensure that after that nylon locking nut, or double nut, is secured, it won't be dis-lodged by affixing another wire to it. Sort of like a "set it and forget it" type of theory which might make sense knowing that amps may be serviced and those grounds disturbed when removing a board, or something of that nature. The colouring of the wire probably signals it's importance in the circuit, and the logic around designing the input voltage areas correct and safe at first. Another important safety reg is to properly solder the ground tabs to the post as well as to the IEC connector. Although some have spade tabs, you are actually advised to not use those slip on connectors for a safety ground. Only soldered connections. Interesting and smart, I think.