What's a CHOKE? Is it necessary in a Guitar Amplifier?
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- Опубліковано 27 лип 2024
- In this video, which is the THIRD in our series on this 1959 Guild 66-J guitar amplifier, we will install a choke and change the rectifier tube from a 5Y3 to a GZ34 (5AR4). We'll talk generally about what a choke is and whether it's a benefit to have one in a guitar amplifier. We'll also look at how much a simple change of a rectifier type can affect the voltages inside your amplifier.
Guild Amp PART 1: • Fender Tremolux KILLER...
Guild Amp PART 2: • Finally...a Guitar Amp...
0:00 Introduction
1:59 RCA Radiotron Designers Handbook
8:15 Choosing a Choke
11:21 Chokes Explained on a Whiteboard
15:22 Installing the Choke
20:00 Testing the Choke Effect on Hum
21:09 Comparing 5Y3 and GZ34 rectifier
#Electronics #Repair #Guitar
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That whiteboard session was excellent
You do a really good job of explaining these things in laymen's terms to us newbies Brad. Much appreciated for the work that you do and how you teach us all.
Definitely informative! You filled in a gap in my knowledge that I haven’t gotten around to yet. Been wondering about chokes lately. Thanx!
Fantastic video and very informative. Chokes were always a kind of a mystery to me but no longer.
As with all things guitar, gear forums will worship at the altar of the choke as some magical tone shaping mod when in reality it just lowers noise/hum/hiss
Well duh !🤣😋
In this case, I don't think the hum was lowered. I think that was already about as low as we were able to get it, but a choke will lessen wear on other components in the power section.
It's also a bit of a conditioner is the way I look at them, lowering the noise floor is a benefit.
I'm going to listen to what brads points are just to see what he has to say I don't know everything yet🤣
@@TheGuitologist
You're wicked smart Brad !
Thanks for the layman breakdown.
I get the gist but the serious technicalities is what I lack. I just haven't learned to read schematics yet. The experiential knowledge you have is invaluable. Really appreciate it. 👍✌
Dude, forget the Variac or Phillips 6CA7's... THIS was the secret to Eddie Van Halen's brown sound!
Really good job with the choke lecture. Can see all the effort that went in. Also very good amp stuff, good vibes and all.
I have learned so much from this channel. I feel like I’m almost ready to build me own amp ⚡️ 🎸
EXCELLENT post, Brad. LOVE this stuff. I know that you're enduring or at least HAVE endured past personal issues but THIS video is the reason that I am a follower of yours.
Awesome, informative video!! I'm all choked up!
I learned some more from you man, thanks for sharing....I appreciate you taking time to use the simpler explanations as well as the technical bits.
Awesome white board section, Brad! Editing was excellent and you explained that all so well!
Thanks Jon.
Loved the white board animation section.
Makes the concept of the choke so much easier to understand.
Great lesson.
Enjoyed the white board explanation man! I hope you’ll continue with that kind of break down in future videos. I get kinda cross eyed with schematics some times but watching someone draw things out like that while explaining in simple terms is great!
Great video, Brad. Loved the whiteboard breakdown. Really brought me back to the classroom.
I find these vids of yours very challenging and hard to understand. And i love it! I learn a lot,thanks😁👍
Very informative Brad. Thank you for explaining this to someone who has a keen interest in Valve Amps.
Excellent full featured content. Thanks Brad.
Great Video Brad! Good explanation of chokes.
Brilliant explanation of chokes...
Love this! As an old RADAR Tech the technical aspect enthralls me.
Great series on this amp!
Thanks Brad for showing us how a chock works, please do more of these videos.
Thanks man. Seriously appreciate the refresher choke course. you Just saved me so much time.
Glad you benefited from it.
The whiteboard explanation of a choke/inductor and capacitor is a better explanation of either than I ever got going to school for electrical engineering. I wish I had this video 10 years ago!
HOLY SHIT MAN! Brad your blowing my mind with this stuff. I give you all the props when it comes to this science behind this stuff. Your the amp science guru! All the credit to you! Wonderful video!
Just What I needed just when I needed it! What a great video. Thanks for sharing your book It's really nice! Thanks for reading to me I appreciate it. Very easy to understand the way you showed this. This is really great example of a really difficult subject for me made easy! I could really understand. Thanks Brad! As the days go by I appreciate you more and more! Thanks for putting so much hard work and effort into your channel!
Thanks, Brad, For All That You Do !
Good work and informative. I looked for more information and got some confronting choking content
This is great info. Commenting to goose the channel algorithm.
That was excellent. Best choke explanation on youtube.
Great serial and i like this video as well, thx for sharing and helping musicians.
Great episode..vast improvement..love the use of the old tech books....
I like the explanation of the choke.
Awesome video Brad !!
Great job Brad, very informative.
Great episode, Brad.
Hey Brad this is a great topic you are a really good teacher keep it up!
I just loved the videos you made for this amp. I never get the chance to work on tube based circuits so to me anyways, this type of stuff is just great. I do have some schooling on tube circuits because back in the 70s they were still teaching both types of circuits in high school (3 yrs) but tubes were definitely on their way out. Except for guitar amps and some other exceptions. I don't want to sound like a frickin' 62 yr old fan boi, but I do dig your show. Great Job!
That whiteboard explanation was so nice ! :D
Dude, great timing... I’ve built and modded a number of amps (since I started watching you many years ago), and I’m about to embark on a huge build which will have a choke, and I’m learning what I can about the subject before I order the parts...
The "chokes explained on the whiteboard" section is great! It could stand on its own as a broken out video.
I’ll put it on Channel 2
Love watching you do this stuff. When you were soldering in the choke around the 19:00 mark I had a flashback to my Army electronics school days and the sergeant yelling "NO WATCHES, RINGS OR DOG TAGS!" at us constantly and I had a bit of a cringe when I saw your rings on LOL
best ignore stupid advice...regardless of were or who it came from
@@trillrifaxegrindor4411 ?
Your Sergeant has explained to me why when my wedding ring hit the power supply output on my 100 watt Acoustic 4-10s amp, I saw a flash that looked like a nuclear bomb going off and ended up missing 100 bucks worth of gold off the ring.
This one was very good there Brad.
Really interesting video! I learnt a lot thank you so much 😊
Funny i just acquired a bunch of tvs with plenty of chokes... great timing as per usual brad.. yoy and Uncle Doug just have a knack for answering whats on my mind lol
I know chokes really well but your video was fun to watch!
Nicely done.
U will never get rid of the noise whith the transformer placement. This is why placement and orientation matters . Great job on explaining chokes . Really enjoy your videos
You always outdo yourself
Excellent video.
The 10 henry choke in the tube manual is for a choke input filter. As you correctly stated earlier, that kind of filtering is not used in guitar amps (because of the larger choke). The filters we are used to are capacitor input.
I'd just like to point out something, courtesy of Mr. Blencowe:
The Valve Wizard
"Many Fender-derived amps use a choke-capacitor (LC) filter to supply the power valve screen grids. An LC filter is a second-order filter, so it provides steeper attenuation of ripple than an RC (first order) filter, and a choke has only a little DC resistance so it doesn't drop much DC voltage. Fender was interested in maximising voltage in order to maximise clean output power. These days people like to overdrive their amps, so there is no need to squeeze out every last watt of clean power, so many amps use RC filtering for the screen grids, which is much cheaper than using a choke. The exact value of choke is not critical, but it muct be remembered that an LC filter also resonantes at its corner frequency, which is given by:
f = 1 / (2 pi sqrt[LC] )
If this is not well damped then it can cause the supply voltage to 'ring' when triggered by certain notes or rhythms, so it is usually best to keep the resonant frequency below 10Hz, out of the audio range. This will require a capacitor larger than:
C = 1 / ( L × [2 pi f]^2 )
Since smoothing capacitors are most readily avalable in the range of 10uF to 100uF, you usually see chokes in the range of 20 to 2 henrys."
Merlin is the man. Aiken has some good articles on this stuff too. Great resources.
Man, of all the books I have, “designing tube preamps for guitar and bass” is my absolute favourite. I’ve bought a number of tube amp books over the years, but anytime I’m having to solve a problem, I always revert to that book because any answer I need is in there, and is usually listed in the table of contests too, so it’s easy to find. I actually have the book on my bedside table at the moment, I’m about to do a big makeover of a little amp and I’m going through the book working out what mods I’m going to do, what value resistors and caps, etc. etc. such a great resource.
I literally just added a choke on my latest amp build last week! Excellent video Brad 😊 choke makes such an awesome difference. Cleans up the power supply and I found hat in my amp it tightened up the response and added clarity. Oh, made the amp quiet as well! Have an awesome day dude!
You’re on your way to being an amp builder, Jay. Loved your build video.
@@TheGuitologist Ah thanks man! Very kind of you 🙏 Yep - on my way for sure! I have another two builds planned already! Its addictive! 😃 Have an awesome day!
I just thought this guy was making a joke right? If not he should meet the guy that tunes the pianos at our studio. He talks about theories that make the internet seem reasonable but no one makes the pianos sound like he can. We love when he comes and tells us all his wild stories wether we believe it or not, it's always a day we talk about for weeks after he leaves.
awesome video! Even an amateur tinkerer like me can understand. The before-after noise comparison didn't sound all that different but when you factor in the increase in wattage it actually is a lot quieter! and now I know a choke kind of does what I thought it would do, there's no secondary winding to grab the magnetic field so the primary winding grabs some back? or something? so it has an electrical cushioning effect. well, the important part is it makes the amp louder and less noisy and increases your rectifier tube lifespan.
What an amazing book 🤘🤘🤘!!
Early on when tube amps had electrodynamic speakers they did not use a choke... well, they did, but it was the magnet coil of the electrodynamic speaker that acted like the choke. Once permanent magnet speakers became available the need for a choke arose.
Great video Thank you
Oh Sh!+ ... I just went to school. This is the best vid. Thank you.
Thanks Brad!
Very nice and visual explained! I calculated my self nearly to death in my studies about filters on university, and your video explains it all clearly without using eny Formula. Well done sir!
I feel like if concepts are understood roughly first, the equations make way more sense. Inductors is some tough math though. Everything has a time component. Best understood with graphs.
Great information having a problem with mine on my old house tube amps need replacing (heat) finding parts not easy to get matching part numbers thanks for this info
Excellent discussion, Thanks. You have a great teaching style that takes a complex subject and makes it very easy to understand. Just like my other amp guru Uncle Doug. Oh, and I'll soon be building the Bias probe, probably two of them for push/pull amps.
Add a lead on the cathode to measure plate voltage on cathode biased amps.
@@TheGuitologist Yes, I saw that. Thanks.
Spot on treatise of the choke function!
Given the added advantage we now have of extended component capacitance (and voltage ratings), the choke, these days, adds little but weight. Folks did use that Amp as was, after all. ;-)
That experiment DID show useful, IMHO.
Great video, Brad. A choke is a must in a tube rectifier circuit. Any decent amp would have a Pi filter on the B+. I don't know why an engineer would choose an LC over a Pi, other than cost reduction. The amount of ripple and IMD reduction provided by that second cap is certainly audible.
First time I saw a configuration similar to Fig. 30.1G was in the schematic for a Hammond spinet organ similar to the one from which a Rola field coil speaker had been pulled; the field coil was between circuit ground and the transformer's center tap. If the power transformer is designed to provide, say, 90V more than what you want at your output tubes' plates, and you must use a field coil speaker, this is an elegant way to simultaneously power the field coil and filter mains hum.
You are a lot more knowledgeable about this than I am, when you installed the Choke, I see that both the power transformer and output transformer are both facing the same direction, I always heard one much place the in opposite facing direction, might that have been one of the sources to the hum?
You're never a letdown. 10w!
We got there eventually. Full dissipation.
I most often use 2 chokes, one right off the rectifiers, and another one between the first 2 caps. Doing this you can use a smaller value of inductance on the first choke, as long as the current rating is sufficient.
I’ve yet to choke an amp so this should be informative.
There's something to be said for keeping the originality, but I'll take function over form any day. Changing the caps and adding the choke sure blows originality out of the water. For all the times you've pulled the chassis you should have added a 1/4" jack and plug for the speaker connection. That's not original but it beats the hell out of de-soldering it.
Woo Hoo like number 305! Great and informative video, as usual. Keep up the great work.
The EGO power blower ad was pretty cool and watched it all. I sent you some money Brad... ;)
holy cow what a legend
Love the artwork Brad 😅, I might have paid more attention in electronics class had you been my teacher
Hammond makes some good parts and are really sought after in amps, especially Hammond transformers from the 70s. I have a traynor that has huge Hammond transformers
That was one of the most informative vids you've ever produced Brad! My one question for you is: what do you use to test inductance? I've been needing to get an inductance tester primarily for car audio inductor testing, but I've been hesitant to purchase one of the cheap ones which are all made and sold in China. It seems they're all I can find or perhaps those are all that's available.
Maybe you can build one…
Thanks. Erie PA.!!!!
Howdy. Nice.
Using Solid State rectification the choke may be replaced with large capacitors. Yes. But the transformer current becomes spiky. Spiky current produces lots of reactive power. It may happen that the transformer VA rating is too low. Could explain why burnt out power transformers are sometimes experienced.
Tube rectifiers don't tolerate spiky current. The spec.s will tell the largest allowable input capacitor. More DC filtering is needed and this is why chokes are mandatory.
High Regards.
Hey, good explanation of a choke. I'm loving the a-hole Hank avatar.
4:47 - The filter in the middle is a three pole filter - so the out-of-band roll-off will be steeper compared to the two pole below. You'll get something like 20dB of attenuation per decade (freq) for each L or C. Therefore the pi filter in the middle should get you (at least) 60dB of attenuation out somewhere around 60Hz (assuming the passband ends at 6Hz) whereas the two element filter at the bottom would be in the ballpark of 40dB a decade out. So, the pi filter in the middle is not only cheaper and lighter - it's fundamentally better at rejecting those pulses coming off of the rectifier tubes. "Handbook of Filter Synthesis" - A. Zverev "Microwave Filters, Impedance Matching and Coupling Structures" - Matthaei, Jones, & Young (I'm an engineer in real life - 24 years in Silicon Valley)
This will be interesting.
Great video, Brad. I like the idea of the cathode hookup on the bias probe.
Would you know the benefits of using the 30.1F vs 30.1G wiring or vice versa?
I'm going to add one to my existing probes.
Excellent White Board demo Brad ... Could you do one about the'' Birds and the Bees'' ... Lol ... Great vid as usual ... Thx for sharing ...
I'll need to borrow your wife for the other thing. I'm sure you won't mind.
@@TheGuitologist I'll send her right up ... Lol ...
A quick tube tickling, she’ll be right back, good as new.
mmm made in Canada, EXCELLENT Simthers EXCELLENT : )
Say you did build a guitar amp with a choke input filter, where would you wire in a bleeder resistors say the choke does not arc when you turn the amp off?
What value and wattage resistor might you use?
I actually did build one with a choke input and it’s awesome, but I do have the arc issue.
I just ordered a 5h 200mah choke to use in 5e3 with a solid state rectifier. The amp has 6L6 power tubes (can use both 6V6 and 6L6 with the latter having more headroom witch I like). I'm having trouble with too much hum though and thought I try chokes as well. Should I put it in series between first two caps or replace the first 5k resistor? If i put in series do I still need to add 400-1000 ohm resistors to the power tubes? Thanks
I usually add a solid state rectifier if I'm trying to up the B+. I'm of the opinion that the "sag" that you get from tube rectifiers is overrated. I believe what people hear when they swap out the tube rectifier for solid state has more to do with the B+ change than actual "sag" at any rate. Eddie Van Halen used a variac to lower the B+ and get that same squishy sound. Chokes are a nice way to get some extra volts as well.
So, hum and noise levels wasn´t reduced at all? or am i missing something? I do not hear any improvement after the modification. Am i right?
in this case, hum wasn't affected. The choke was still a good upgrade though because the rectifier and everything else in the power supply will be less stressed because of the choke. In other cases, the affect on hum may be more pronounced.
@@TheGuitologist Oh i see, thanks for your kind answer. I have a 5F1 clone and was considering adding a choke to reduce 50hz hum but i probably will learn to live with it as it is not as bad. Cheers!
I was wondering, what causes chasse buzz, if I spelled that right? When you pushed up on it, it stopped buzzing. Cool video, by the way.
No demo????
See the Part 1 and Part 2 videos of this amp for jamming demos.
16:30 Those are some nice sounding pads in the background soundtrack !! What did you use to get those , Brad?
That’s not my track. It’s from the UA-cam library
The motorboating at 26:00 - how can I get rid of something like that?
Hey there can i suggest to you that you ignore these critics if they know so much why are they watching you ???? really i think you are good at what you do and very good at explaining the works !!!!☮👏🏴☠️
I have 2 accounts on UA-cam - Guitologist and Guitologist Channel 2.
What sort of choke would you recommend for a 5f1 clone?
A question ive always wanted to ask
Not sure if it has been mentioned, but you are at almost 30mA on one channel so that is 60mA for both. The choke is rated at 50mA, did you reach inside and feel if the choke is getting hot?
Many years ago I sent one of my amps to be worked on at a then well known facility who used to sell mod kits. When I got it back it was working but they removed the original choke and substituted them for some resistors; if I remember correctly. I heard it would do the same thing but makes me wonder if the outfit wasn’t that honest and they just confiscated my amp’s choke for their use/gain. Later on I had to buy another choke and get it installed by another tech.
Stuff like that happens. Maybe the choke was open?
@@TheGuitologist Old Parts should always be returned to the person commissioning the repair unless they say otherwise.
@@highpath4776 I had a guitar shop charge me extra on my guitar after having pick ups swapped. Because he took It on himself to replace my pots. Why? What's wrong with my pots? They were bad. Can I have em back? No. Why would you want them?
I'm out of this place. Started trying to do stuff myself after that.
I don't know if it's just the compression in the video but in the comparison section I heard only a VERY slight reduction in hum that was accompanied by a VERY slight increase in hiss, didn't seem to be very effective at all and the overall noise level seemed to be the same. What's up with that?
I think you are correct. I believe in this particular amp, the noise had already been reduced about as much as it possibly could be reduced using other means of virtual center taps and lead dress, ground buss, etc. I did a TON of work to get the amp this quiet. Even with the lack of improvement on hum, which was already pretty damn low, I still think a choke is good for the amp. All the power section components will not wear as fast or be as taxed by inrush currents.
At around the 15:00 minute mark, it took me a second to realize your diagram was not a dead guy and you weren't going to give a warning about voltages. Guess I need some more coffee...