Understanding Vacuum Tube Amplifier Schematics - Grounding - Part 6
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- Опубліковано 5 лип 2024
- BG144 - An explanation of various grounding techniques seen in tube amplifiers and how they are represented via schematics (not often so accurately). We cover star ground, buss (bus) ground, and combinations of the two as well as earth ground.
- Наука та технологія
Mark, Thanks yet again for another well-explained video on the basics. I've just finished watching all seven videos (so far) in this playlist/series. I'm looking forward to another one -- now I need to look at all of the videos you've made to see which would most benefit me at this newbie stage of my tube amp troubleshooting/repair career (something to do when I retire). I hope that if you haven't already done so, that you'll make a series of videos on the basics of troubleshooting & repair, and then, possibly one or more troubleshooting & repair series for _more_experienced_ "Amp Techs."
Fantastic work! I didn't even realize this playlist existed... Looks like I'm set for the weekend 😁. Thanks very much for sharing.
Awesome! Thank you so much for these different series videos.
Thank you Mark, I'm WELL overdue some refreshers on tube circuits they have fallen by the wayside somewhat since changing to sloid state, I've been thinking of doing much more with tubes now so this is great for me, thank you again for your time and great presentations.
I wish this video was around a few years ago when I built my first amp, I'm getting ready to build another tube stereo soon and cant wait to see how your amp sounds.
Mark, another great video. Thanks and keep up the great content.
Great series to learn from! Watched 1-6. I know these video series was done awhile ago. Would be nice to see it keep going with other topics.
Thanks for the Video!
I've been struggling for some weeks on the grounding of an high-gain guitar amp that I'm designing, it's a puzzle that I can't solve.
I plan to make every tube stage as its own star, but instead of connecting them to ground I'm connecting them to a bus wire, which is connected to the chassis only at the input jack.
The problem is the following:
My pre-amp ground bus has the following scheme (I also indicate the PS rail they are fed from):
(Input - Chassis ground) -> (Preamp Stages - HT) ->?? (Solid State EQ - 24V, relay bypass) ->?? (Phase Inverter - HT) -> HT Reservoir ground
Power Amp HT will be wired in parallel to the pre-amp with two dedicated wires (due to additional circuitry constraints).
The problem is that the EQ is powered by 24V, which comes from a different winding of the same transformer and it has its own dedicated reservoir capacitor.
The EQ is actually a well known graphical EQ circuit, but implemented using BJTs instead of opAmps (I'm replicating a real piece of equipment).
My power supply ground has the following bus scheme [brackets are the windings that power the rails]:
[(HT Reservoir / HT CT / Heaters CT)
Thanks, clearest explanation on grounding I've seen!
Very very good content on grounding. Thank you!
Thanks, you always bring up something new that I was not aware of. ........
the unclear aspect to me is the discussion of chassi ground with the scope of completing the circuit mentioned at 3:15. isn't the neutral plus hot sufficient to complete any circuit? the point is that the neutral wire is use in input transformer and not available anywhere else inside of the amp circuit. so to from the transformer secondary to all of the inner circuit of the amp the only way to complete circuits in there's are with connections to the ground . but does that also not mean that there is always a large current eg 1 amp or more of current flowing to ground? we simply do not get schoked when we touch the chassis because the wiring to ground is of infinite less resistance than our skin correct? but still the idea of ground being used to close circuits instead of the neutral is very counter intuitive. on is used to thinking of ground as a safety tool to kick out current from electric components that normally not be electrically charged. thanks for your feedback
Great video, thanks for all the advice.
Learned a bunch there. Can see some mistakes in my past. Particularly the RF coupling from input/output coax.
Coax has advantages. We forget why it was invented. It came alone well after the audio tube world. Using it foolishly, well, gets you what you deserve.
Big, big help. Thank you.
You answered so many of my questions. Thanks. Liked and subscribed.
Thanks Mark for these. I have watched them more then once. If you want to do one on buffering stage. That would be great.
Excellent video Mark! I've built several amplifiers over the past few years utilizing the techniques you've discussed in this video but I never really completely understood why I had to wire the grounds the way I did other than I was told it prevented ground loops. This video went into excellent detail and really explained the reasoning behind it. I'm going to have to back into my prior amp builds and re-examine my ground wirings! Thanks again for some really great info!
Great series. you clarified to me so much. I am not going to be and expert yet, but after your explanation my first kit assembled seem easy to TS or upgrade, if it was necessary. Many thanks to take the time to recorder and share it.
Great vid. You help me a lot.
Great advice, even if I already learned a lot of it the hard way!
really great info, thanks!
On shielded signal wires through amp, you said ground one side only, however, I'm wondering if it also matters how all the single signal shield grounds are connected? Can they each go to chassis, together at a point, or to the same point as the input jack? Excellent centralization of all this info! Thanks.
One thing I don't understand: if you have your B+ going back to the transformer via the chassis... wouldn't this electrify the chassis at -600V as well?
Also differential switches: they are mandatory everywhere in EU. If you have starpoints connected to chassis as well as earth ground, wouldn't this make the differential switch pop if another device in the house leaks current into earth ground?
In general: is it desireable to have your chassis used as mass ground? Wouldn't it be more safe to have your ground "float" from your loads up to your transformer/bridge rectifier?
If you use a bolt to connect your safety ground to the chassis, use an extra nut as a lock nut for extra security.
Very well explained.
I plan to make a single point ,star ground system, in a amplifier using a linear transformer power supply. So the chassis is connected to earth ground at the shortest point to the iec. Is point of the star ground connected to the chassis at a point close to the first power supply cap? Or is that star ground point left isolated from the chassis ? Great videos btw
What brand was the amp at the end. Definitely worth aspiring to.
Thanks a lot for this. I built a tube amp a few years ago but could never quite get it hum-free. Based on this video and some other places I finally decided to make a star ground and run lots of wires to it from all inputs/outputs/psu/amplifier circuit, and it fixed it entirely, amp is completely quiet now when theres no signal. I knew star grounding was a thing, I was just too stubborn to believe it would be neccesary, I guess I was wrong. Great video.
Just read your comment. I’ve got an amp that’s oscillating and motor boating both. Haven’t paid attention to grounding. “Grounds” (so I thought) everywhere in random spots. I’m bout to star ground or buss ground it. I’ll try to remember to report back.
Buss grounding fixed it. However, I forgot to ground one end of the buss. It was horribly noisy until I grounded one end…. The ground on one end cleared up nearly all the noise….. still sounds tiny, but I think it’s due to the voltage being too high on the preamp tubes. At least I can work with it now! This guy’s channel is awesome!!
Thanks!!
Did you ever make the “guitar amp” part in this series? It was noted as coming soon in the lat video.
Btw, thank you for sharing your knowledge!!
On the slide on 15:45, first bullet for the star ground point is «Do not tie this to same point as earth ground, that should be it's own connection». Could you elaborate on that? Why this should be a different connection? This separate star point connection will be connected to the earth ground via chassis, doesn't it make sense to have this star point connection as close to the earth ground connection as possible (in the same point)?
Brilliant. The fog lifts...
I'm probably not be understanding this right. In this video, you said not to tie the output jacks to the chassis ground at all. But in another video (I think it is the single ended build), you connected the output jack commons to the chassis star ground. Please clarify. Thanks.
It was the KT88 single ended build, episode 6.
@13:00, you show an example of power xformer with black/white/green leads. I have an older power xformer, no green, two black for AC in. How do I determine which black wire is supposed to be the white wire?
It makes no difference either way.
Is it possible to make pdf's available for the notes in this video?
Why the output jacks should not be tied to chassis ground?
Grounding outside of the amplifier can be your biggest problem too, example your amplifier and preamp arent grounded to the same outlet this can create a huge ground loop going through the walls of your house
Thank you for the info, 21
Sorry that i only can give one thumps up ;)
Understanding Vacuum Tube Amplifier Schematics - Guitar amps - Part X
never happened? :(
I know little electric theory, I want to get my tube amp, to sound perfect. thank you
It is expensive to build a stereo tube amp. Power tranformer, 2 output transformers, vac tubes, caps etc for a 50 watt amp will be in excess of $ 1500.00. Tools to make chassis, tube sockets for point to point wiring, no circuit board, like in the 60's. Or you can buy a Macintosh amp for $4500.00.
I build a soldano sl100 based guitar amplifier boosted to 120watt for around 1500$ and its has only one output transformer (one big ass tho)
I mistakenly hit the thumb down cleaning my screen. Sorry
Kevin Ski - you do know what you can just click the thumbs down a second time to "clear" it, right?
Håkan Berg Thanks, it's always the simple stuff that trips you up...like grounding
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