'64 JMI AC10 | Part 3 : What It Takes to Do It Right (for true amp geeks only)
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- เผยแพร่เมื่อ 7 ก.ย. 2024
- For those lamenting the recent spate of shorter videos, here's a long detailed one for you.
I'll be interested to see what percentage of viewers watches the whole thing.
Percentage watches? Percentage watch?
For that matter, how many people actually read these descriptions. Banana milkcow longform magisterium.
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These are things I get asked about a lot :
Amp Tech Gear Used :
Hakko FX-951 soldering station
Weller SPG 80L soldering iron (chassis work)
Rigol DS1054Z digital oscilloscope
Thsinde 18B+ digital multimeters
Kester 60/40 solder
Techspray #4 No-Clean Desoldering Braid
Below are things that make this channel possible that people don’t usually think about. If any of these companies want to send me new and wonderful toys, I’m open to that. I can’t take free stuff when it comes to the amps I review, etc, but for the stuff below, bribe away!
Microphones/Audio Equipment :
Guitar Amps : Royer R-10 Hot Rod and/or Shure SM57 (noted in videos)
Voiceover Bench : sE Audio sE8 (small diaphragm condenser)
Voiceover Streaming : Shure SM57 with shockmount and windscreen
Voiceover Mic Arms : Elgato Wave Mic arms
Guitar Mic Stand : Gator Frameworks short weighted base stand with boom
Mic Cables and Guitar Cables : Mogami/Neutrik
Mic pre : MOTU M2
DAW : Logic Pro X on MacBook Pro 16 running Sonoma 14.0
Plugins : No effects other than level matching/normalization unless a recording
specifically has reverb etc added in post (rare, various Waves plugins)
Monitors : Yamaha HS7s
Monitor Stands : Gator Frameworks Desktop Clamp-On Stands
Monitor Isolation Mounts : IsoAcoustics Iso-Puck Minis
Headphones : Beyerdynamic DT 770 Pro (main)
Headphones : Sony MDR-7506 (alternate)
Video Equipment :
Camera : Sony ZVE-10 with SmallRig Cage (main)
Lens : Sigma f2.8 18-50mm (main)
Lens : Sony ZVE10 kit lens (rarely used)
B Camera : Apple iPhone 13 Pro (rarely used)
Tripod : SmallRig 71” with SmallRig Fluid Video Head
Streaming Mount : Elgato Master Mount S with SmallRig Ballhead
Bench Light : SmallRig RC 120D
Bench Light Diffusor : SmallRig Lantern Softbox
Bench C-Stands (light and overhead camera) : Neewer Pro SS Heavy Duty
Streaming Light : SmallRig RC 120B
Streaming Diffusor : SmallRig Parabolic Softbox
Streaming Light Mount : SmallRig 148CM Wall Mount Boom with Triangle Base
Various Other Lights : Neewer LED Panels with Neewer Softboxes
Video Software :
Davinci Resolve 18.6
Paul Leeming LUTs
Adobe Illustrator 28.0
Adobe Photoshop 25.0
Ecamm Live (streaming software)
Just got ready to go to bed, watching from Scotland, Always enjoy your videos, as ever meticulous work Lyle,. Don't hide your light under a bushel, you are the best tech on TH-cam. Looking forward to your next Live Chat.
Great to see your safety earth wire left longest. Exactly what I was taught over 40 years ago - if that mains lead gets pulled it’s the last wire to break.
One of the best sounding amps on the planet, right here ...
The science of sound is fascinating. Thank you for explaining your work.
The 6U8 is the equivalent American version of ECF82. Other pin-out compatible triode-pentodes (although with slightly different characteristics) are 6EA8, 6GH8, and 6KD8; and I've seen tubes with as many as 3 of these numbers printed on the tubes and cartons! All of these were used in classic late 1950's hifi gear such as Scott and Fisher, typically for the tuner section and as phase-invertor/driver tubes.
Sorry if my watch habits strewed the watch stats. I watch your long and short vids start to stop, but maybe not in one sitting. Life is full of surprises and interruptions. I visit and revisit your vids often for review and to learn something new thoroughly before going off “half cocked”.
Thanks as always for all you have taught me and what I continue to learn from you.
Nice rig. A friend of mine who owns a music store has a 1963 AC30 with the add-on Top Boost hacked into the back of the amp. What a thing of beauty. I think these old classic Vox amps are the coolest ones out of the vintage amps.
See yesterday’s video. ;)
Yep, mine is the same with the trem + adding more gain on the EF86 channel when turned all the way up. Mine appears 100% original
Speaking of amp geekery, it looks like the paint dabs on the pot connections match the color of the faceplate. Schweet!
Very interesting. I love seeing a master of his skill work.
I just love looking at expertly built guitar amps.
Lovely work man! I would worry about those two chassises, chassisees? Chasi? ...anyway I'd worry about counting on the mating surface of the two for ground connection. You would think they'd use a wire or a braided wire connection 🤔 I guess it works for all the ac30s out there
Thanks so much for sharing your vids about the AC10, I have a ‘64 AC10 and it needs a thorough cleaning and parts replacement. You videos are always educational and entertaining, thanks for taking the time to lake them!
Very nice work and the amp sound fantastic.
I was just starting to type this as your spoiler came up - but yeah that’s how the vibrato works on the AC-10, backwards as it seems. Only reason I know is my friends got one. Beautiful little amp
Love the longer videos! Banana milkcow longform magisterium
Hi Lyle. Great work as always👏🏽 Love the Sound of these Old AC10s…😀
But I must admit i don’t understand why inserting a pair of 100 Ohm resistors in series with the plates on the output tubes suddently would make these run as triodes?
Usually, if you (for some reason) would want to run pentodes as quasi-triodes, you would connect the screen grid to the plate of the tube. But this is definitely not the case here..?
I would have guessed that Vox installed the 100 Ohms on the plates as a kind of protection fuses for the output tubes: If an output tube shorts out, the resistor will burn and open preventing that the increased current through the tubes blows the output transformer.
Yeah, I didn’t explain that very well. I’ll expand in the next video.
Excellent tech work as usual.
You do very nice work. I appreciate this video.
I need to get a couple of my amps to you, but it looks like you are up to your elbows in amp work already.
Thank you.
I've subbed to your channel for years, and just love the amount of knowledge you pass on to your viewers. Can I correct you on a pronounciation? The Welwyn resistors are named after the town of Welwyn, which in the UK is always pronounced "Wellin". I have no intention of being a fusspot, but I know how you like to get things right.
Thanks! I do like to know such things, and English place names are tricky without local guidance. I remember cringing when my ex asked a cabbie to take us to “lie-chester square”…
Yes. I read the banana milk cow longform magisterium.
Thank you for the longer form video.
No more charlie foxtrots. Nice use of the pretty Hakko tip cleaner.
Wow Lyle. Ive never seen the guts of a vintage Vox or any Vox for that matter. Seems like posts would have been more durable compared to this tag style board. Love watching all the amps you work on.
Have one of these in fawn I am slowly going through... Mercury is rewinding the dead choke when it returns it will be time to fire it up and start the troubleshooting... This is very helpful, not a lot of info on these out there...
Great video but still trying to figure the milkcow and magisterium references... 🙂
Great vid!
The «reverse» wiring seems to be a Vox thing. Their british made guitars have that same reverse wiring on the tone pot.
Lyle, would you say the statement about solder not being structural is aspirational rather than definitive? I suspect there's many instances where it is used as structural which is hard to avoid and/or reasonable practice. Thinking chassis grounds, SMD, etc. I'd have thought you'd always prefer to avoid that where possible, but accept it as necessary under the right circumstances. Last point seems critical and something you often learn on other's behalf...
Great video! I noticed that the guitar cable used to test the amp has a Neutrik "Silent Plug". Shouldn't this go to the guitar instead of the amp? Banana milkcow longform magisterium.
I have those on each end of this cable. Straight and right angle ends for different guitars.
You need to put a preview for your next episode at the end so people will watch the entire video 😆 You gotta play the game
That’s a great idea. Hmmm….
Except for the people who would just skip to the end. I don’t know if that helps the algorithm…
Lyle, I watched all 3!! Thank you for the detail you did go into. As a guitarist, not a tech...and as a physical science teacher, I recognize that I do not know nearly enough to even be dangerous. I respect your knowledge and work. What do you suggest as a good first book to read to begin to understand the basics of amplifier builds/design? I need to pad my Christmas list. Many thanks for all of your excellent content.
Thanks. Merlin’s books at valvewizard.co.uk
And you might brush up on ohm’s law and basic electronics and wiring techniques as well. Melvin is a fairly deep dive into the end of the pool. Hold your breath! And read everything twice!
@@tjminasi1442 thanks!
@@PsionicAudio thank you!
Interesting ... the "amplitude" designation would suggest to use "frequency" instead of "speed" which goes better with "depth" or "intensity".
ecf82 EURO and for USA 6u8 good triode /pentode tube. used a good bit in HIFI.
Yup. 6EA8, 6GH8, and the less common 6KD8 all have the same pin-out as the 6U8, with slightly different characteristics. All except the 6KD8 were commonly used in old Scott and Fisher hifi, both in the tuner and as driver/phase invertor tubes. For guitar amps, where choosing the right tube in order to achieve the lowest possible distortion isn't so critical, any of them would likely work.
@@goodun2974 Have about 50 of the rca 6gh8 if Lyle want to play with them .
Surprised to see all these various ground points on the chassis... a big no-no, IMO. I use a single point ground for everything in the amp. That's how I was taught, and how most hi-fi amps are done.
Vintage guitar amps were virtually never star-grounded ---- and, as many techs and homebrew amp builders have discovered, star-grounding a guitar amp can sometimes create problems (noise, oscillation, instability) rather than prevent them. The concept and implementation being used nowadays is sometimes referred to as "ground steering".
@goodun2974 vintage amps also used death caps and other unsafe practices nobody should emulate. Using the chassis itself as a ground return isn't a good idea, and I've not heard of star grounding causing problems (probably a layout issue)... but you do you.
@@joeltunnah , guitars have antenna-like pickups, are often poorly shielded, use unbalanced cables to the amp, and are often used in a high-RF environment; and the amps have high input impedance, on-board effects such as tremolo and reverb, tone controls that typically lose gain, and lots of gain stages to make up for the other lossy parts of the signal path ---- plus they're often operated well into clipping. It's a very different scenario than a hifi tube amp! Typically a somewhat better-designed vintage guitar amp will use several ground planes ---- old Fenders with a brass plate for the pot mountings being a good example ---- but it gets trickier with modern higher gain amps aimed at the metalhead and shredder market, where extending ground lines to one theoretically "ideal" central point actually creates problems instead of minimizing them. Anyway, you might try reading up on the subject before issuing a blanket condemnation.
@@joeltunnah , ps, no modern manufacturer that I know of uses polarity switches and/or "death caps" nowadays ---- polarity switches are against electrical codes, and any capacitor connected directly to the AC line (to filter voltage spikes and RF) has to be a special X or Y class safety cap that won't short or leak voltage ---- and good techs always install a grounded cord into vintage amps and remove the death cap ( I've been repairing electronics for 45 years). It's silly to compare electrical practices of the 1940's to the early 1960's to the practices and code requirements of today, because they didn't have 3-prong grounded outlets in most homes in the 1950's.
@goodun2974 I'm not comparing them, you were. You said "vintage amps never used star grounding", seemingly implying that vintage techniques should be followed when building or repairing them.
And since hi-fi amps are flat from 20Hz-20kHz, and have speakers that can actually reproduce that range or close to it, the build and layout is even more critical, not less. A guitar amp+speaker can barely do 60Hz-8kHz, hum is attenuated just by the poor reproduction of the system.
And I have read up on it, and have a lot of experience actually building tube preamps, stereos, and guitar amps, thanks.
I'm new to amp work (and primarily working on a Hammond D-152 rebuild, similar but different) and find myself constantly ordering parts in short runs. I've noticed a few times you mention ordering parts; do you intentionally keep your stock lean, or is it challenging to keep a stock of parts that would handle "everything" that might come across your bench? For my MCI console, I could buy many parts in quantities of 100-300 from Mouser for amp parts, but I'm finding that less practical for amp parts.
I stock an awful lot. But for this amp I need a few rarely used values and I’m out of 330Ks. I’m ordering 200 330Ks but only 10 750Ks for example.
@@PsionicAudio thanks! that makes me feel better that I'm not "going it wrong" as it seems hard for anyone to keep a complete stock. Love the videos!
I had this very amp, the vibrato makes a loud "pop" when engaged and also starts thumping when pushed to go fast.
Is that a major/costly problem to remedy?.
I've already spent a small fortune on it and it's never really lived up to my expectations of what a JMI era Vox should sound like, I wish I could get it into your bench!.
It shouldn’t do either of those things but I can’t estimate the cost without seeing your amp. Where are you located? I might be able to recommend a good tech.
@PsionicAudio
I'm in Glasgow Scotland.
Thanks.
I can recommend Roland Lumby in Manchester and Dave Hunter in Nottingham. Closest ones I know, sorry. Paul Stafford Cook has a tech he likes, I think in Glasgow. You could ask him on his channel, or contact Dave or Roland and see if they can recommend someone closer to you.
@PsionicAudio
Ok, thanks.
It's a shame that it's not running at It's full potential, I know there's a gem under all the dirt!.
Always enjoy your content btw, it's always a pleasure to see a man who's not only talented but passionate about his work!.
Banana milkcow longform magisterium? Lol
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😎✌👍❤🖖