Grandpa's Tube Karaoke Machine Becomes Smokin' Guitar Amp
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- Опубліковано 29 вер 2024
- This is a 1950 Webster Chicago Model 166-1 Portable PA 110 Combo. A customer brought me this thing and basically said "do your worst". He may have even used the phrase "make it breathe fire"...so I did. Here's the entire conversion process followed by a demo, including my crappy impromptu rendition of Prince's "Purple Rain"! For this conversion, we rely heavily on the RCA Receiving Tube Manual to convert the preamp input from a single 7-pin 6AT6 triode to a 6AU6 pentode. Click here to get Tube Amp Repair Essentials, including the RCA Tube Manual used in this video: kit.com/TheGui...
I get lots of emails and messages about this, so click here to get Tube Amp Repair Essentials, including the RCA Tube Manual used in this video: kit.com/TheGuitologist/tube-amp-repair-essentials
Awesome as always! I'm waiting for the kitchen blender guitar amp... lol
The Guitologist: Excellent job on the amp. Those humbuckers really pushed that front end nicely. The one setting with the Tele sounded really nice also! The "kit" link is a great addition. Thanks!!
Thanks, y'all. I appreciate the comments. The humbuckers definitely were the winners here. It's usually the single coils on these old amps. Nice to see hums get a win for a change. ;)
Yeah... I was surprised how it "growels" on the 'buckers... That is a rare thing for this old amps, radios, PA's and just about everything you find with tube inside it and convert it... But the speaker played a great roll here. And BTW great video, because conversions are my kind of thing
Hey Brad, thanks for this link. I came here to ask you the current rating of the variac you use ... found it on the linked site. Thanks
Oh good lord!
I can't believe you got that thing to sound like that. Bravo!
Rewire,explanation,test,info,demo.All good bro.
1990's Food Processor Becomes Smokin' Guitar Amp
That's next week. Then we turn the microwave oven into a microphone.
What about a Talk box outta found objects?
I've got one of those that was given to me. I found a connection from the factory that was never soldered. The amp had been passed around because it would quit working at times. After fixing the bad connection, it makes a great amp. Creamy break-up.
The tubes that are in it are the best from the 50's and still work fine.
Great sounding amp. That ending was too damn cute. Another great video, sir!
I understand your point about the placement of the tone control, Brad, and it's not like a Fender, but look at it this way: the original Gibson LP amp had a similar placement, and then there's the Cut control on the AC30s...bleeding off treble frequencies just before the signal goes to the PTs allows the player to retain all the harmonic richness right up to that point, and it's those frequencies that really make harmonics and other overtones jump out of the mix, giving that lively stew of 'gronk' that we all know and salivate over...and you wouldn't want all amps to be just like Fenders now...would you? Just MHO...
I dislike homogeneity also, but since I was changing the phase inverter also, I wasn't sure how the tone control would react where it was. The chassis on this thing was really too cramped, not conducive to experimenting really. You needed to have a game plan on what components to replace first/last, because some stuff will end up getting buried under other stuff.
Please don't think I was being critical; I'm constantly impressed by your ingenuity. I just wanted to offer an alternative PoV about the pros/cons of that TC placement. The LP amp used a paraphase driver, with the TC post-anode on the input, so the inversion phase would have amplified whatever was left after the treble had been bled off, and it worked, but wouldn't have phase-cancelled as well as a long-tailed driver (but they really cranked!)...great job on getting this amp to sing out, BTW...
I didn't take it that way at all. I appreciate this kind of critique. Keep it coming!
Brad, what is that thing measuring the amps, volts, etc that you've attached to your variac? I need to get a few of those...one to add to the raw power source, one on the variac, and one for my isolation transformer. Also, did I still hear some 60 cycle hum in the earlier part of your post-fix test drive? Was that the guitar pickups?
amazing sound,great show;singing as well- i tell the ghost of beethofen your greets -but he's
a deaf numb-i go to mozart ;he tell me you play like j.s.bach! a rockn rolly
SERVUS from vienna!!!
Wow. Great work. I'm curious, what is your electronics training? You seem to not only have "book" knowledge, but you are very intuitive as to what values of components are required.
P.S. You guitar skills are equally amazing.
Wondering why not also use the 2nd channel for a mic inpu?
holy smoke - i want one !
Okay MacGyver, I bet you could.turn a matchbook into guitar amp. And I still desperately (haha) want to talk to you. Do you have a contact email?
Best wishes, Keith
Machista jajaja
One of the best overdriven tones I even heard from your videos.
Thanks for sharing man
Thanks, buddy. I appreciate that.
Hey, I didn't see the very end until now, your daughter giving you a guitar. She is so precious. I just about teared up. I've a granddaughter the same age, almost seven, that I adore. You are a lucky man.
Totally. I am blessed more than I deserve. That fact is not lost on me, and I thank the Lord in quiet moments for all that I have. Thanks for the comment, Buddy.
I have a wife, 4 kids 2 boys and 2 girls, all grown now and 10 grandkids I'm blessed as well, but you can't ever show your weak spot what ever you do! My oldest grandson picks on me, he's 6'4" 330lbs 16 years old, so cute... He's a linebacker and wrestles, but I never showed all of my goodies! I trained him never knowing his nickname would be Kong... He took me out on the front yard to show me who's boss. I'm only 6'1" 240lbs and 56, I tried to tell him I wrestled my whole life, but he had to get some, telling me I'm old and he's right. I couldn't get him off the ground to save my ass!
hahaha. I guess it's not all in the training.
My fondest memories is the pride my grand-daughter showed when she sat beside me with the band in church.
Quite possibly one of the most unique amplifier rebuilds/mods the world has ever seen. I'm glad I hung on to my 7-pin TV tube collection. Maybe one day there will be a schematic for this amp, it sounds phenomenal.
Thanks for the comment, Joel. Glad you like it.
Is she English?
Awesome Brad... thanks for diving in and actually showing us your thought process and design. I am trying to learn some amp repair so I can service my own amps and maybe build/ convert as a hobby. Between you and Uncle Doug there really isn't any better teachers available in this format that I have found. You have a nice family by the way. Thanks again
Scott Waters Same. Uncle Doug and Brad have been pretty much my teachers in amp repair. Been able to do basic repairs because of the videos they put out.
Thanks for the comments, guys.
As somebody who has no electronics experience, I had no idea what you were talking about, none the less, your video made more sense than my AP European history class.
European history in a nutshell.... Greeks kicked everyone's ass, then Romans kicked everyone's ass, then Byzantium kicked everyone's ass, then the French kicked everyone's ass, then the Dutch kicked everyone's ass for a minute until they bankrupted themselves over a flower, then the French kicked more ass again, then the British kicked ass for a while and launched an Industrial Revolution in the process, and eventually the Germanic tribes, who had been pushed and kicked and beaten for a could thousand years, got pissed off and kicked ass for a couple years until everyone got together and kick their ass and shame them into all becoming castrati shadows of their former selves. Also in there, people mistakenly thought attacking Russia with winter approaching was a good idea. It wasn't a good idea.
As a proud European, you pretty much nailed it.
As another proud European, I second that.
The Guitologist As an American, I am fat.
Wait, I remember this History crap, you missed the part about Hot Queen letting the peasants eat cake, and twins gone missing in Scotland Yard (which is in England, NOT Scotland???) turning up 4 century's later in a parking lot!
That amp is a monster! Great Work on it!
Great Job! Nice to see you stick with the 6AU6 most would just slam a 12AX7 in. But you got it to sing out nicely. The RCA Tube Manual is the bible. I fond it useful for using some Hi Fi Tube amp noise reduction techniques on guitar amps. You don't need a Noise gate Metal heads you just need a better amp.
Was really cool hearing your wife giggling in the background and you chuckling. Cool amp.
This is the best damn inside view I've ever seen.. This guy seems young but has GREAT old knowledge.. Hey can we keep in touch.. I have a year or two left...till I die..
RMA 375 sounds like it is Webster Chicago calling out their Radio Manufacturer's Association code (pre-cursor of EIA). 375 matches the prefix of the "Prod No" on that label inside the cabinet. See www.triodeel.com/eiacode.htm for a mention oif EIA to RETMA to RMA.
Thanks for the comment, Tim. I believe you are right. The RMA did jog a memory, but not loose enough to get any information out. Too many cobwebs up there.
No probs. Cool project. I had not seen you go that far in a mod!
Double the danger, double the crap. It's the statement of the great risk of double-death-cap.
I love Guitologist videos, have watched many of them.I don't even work on or use guitar amps, I troubleshoot and fix entirely different types of equipment.But there are many similarities. I just find Brad to be fun to watch and listen to. He's really cool in my book.Just sayin'.
Your wife seems pretty cool
Don't encourage her, Ed.
Does your wife even like what you do...
How does she stand all that geetar amp noise and loud playing...
Two words: padded room. :P
Padded room...for her or for you?,!
Hey, at least the tube sockets and pots are original!
What more from a vid that restores, rebuilds and reengineers an amp. Then plays riffs from all genres. Even my favorite metal rock crap. Lol Your daughter was just whip cream to great cake and ice cream. Thanks Brad
Your videos gave me the confidence to modify a Mint Blues Deluxe Reissue I picked up last week. Put in the Fromel full kit and wouldn't you know I turned it on and nothing. I was able to find my bad solder joint using the lessons learned here. Thanks
Cool! I'm glad you got something useful out of watching my channel.
Hey Brad, great work on this conversion! Your sense of detail is astounding on this - let the use of the RCA bible be of note to the young and home-gamers! I think I'll borrow the idea of the 1482 output section for my Bell & Howell conversion! It's got a 12SJ7 and 12SN7 - should be a beast!
The RCA manual should be on everyone's shelf. It's one thing you really can't PDF. Books are not dead!
That tone circuit is almost exactly what a VOX cut switch is. You should try leaving it. Fender did the same tone on there very first amp the Model 26 Deluxe. Also the 6au6 is a miniature 6sj7. So you can copy the First Fender Champ Input or many others that used a 6sj7. You can even go close to a ef86 style input but the ef86 and 5879 are way better pentodes for audio.
I apologize for the schizophrenic playing at the end. :P
The Guitologist
It's probably good that you get that out of you. It might be just what you need to give you steady hands for the next repair. Wish I understood tube amp repair. I have an old Masco MAP18 hat needs a complete rebuild. That amp sounded great then one day the output dropped to about 50% but it still worked. One of the tube sockets was broke and the tube was loose. Started cutting in and out while playing so I pushed down on it a little and it went quiet. It didn't make any pops, no buzzes, no mad scientist noises, no burnt smells. Nothing. Of course that I unplugged it right away and it's been collecting dust since. Maybe someday I'll buy all new parts and go for it myself. LoL. I might.
Webcor Chicago Pulaski street. my father was a supervisor back when I was filling diapers there.
That’s a monster right there. Great job sir ... like holy frickin hell man watta beast
Even high priced high end amps have mistakes Non Soldered Incorrect parts all missed by inspection . Like the Mesa Boogie Quad preamp I just finished Had the Incorrect Master Volume Pot a 10K instead of 1Meg. 29 Years with out someone finding it, the original owner probably never used Ch2.
Wow! That would make an enormous difference too!
This video is pretty ugly until 59:06 and I don't care who knows it. ;-)
It would be cool to play that amp going through that 4x12 it's sitting on, but with a tube screamer used as a boost, or just a boost in front. So you have this little amp that was used at some hazard county pumpkin fest in the 1950s and now you're playing Racer X's scarified through it. hehe fun stuff.
LOL, chives are looking to luscious. Tell your wife to water the chives. . then duck.
She thinks she can keep plants, but obviously, it's a waste of time and money. I've given up trying to speak reason to her. She's red-headed, and the reason just gets filtered out on the way to her ears.
daughter and wife are both beautiful.. Just keep doing what you're doing... Thanks for sharing.
Billy Gibbons would love this...
DAMN THAT "LITTLE BASTARD" ...LOL ... THING SOUNDS VERY SWEET ,... EXCEPT I NEED ABOUT 20 WATTS FOR A GIG TYPE SETTING ... ))) ... NICE WORK
Thanks, man. It's about 12 watts, but slap a mic in front of it and send to the board and pretend you got a Marshall stack. ;)
Just picked up a working one today for $123 (OK, and $30 shipping) 😊
And thanks for the schematic and mods/fixes.
You may want to do something different with yours, but hopefully my experiences give you some directions to consider. Good luck!
Those rivets are Rivet Nuts. I've never seen them for wood, only for metal. If you want to assemble sheet metal pieces with machine screws instead of self-tapping screws, you use Rivet Nuts.
They can clearly be rounded off at the other end with the proper tool.
Hi Guitologist. Please can you do a video on a 5F1 circuit with the schematic and a wiring diagram? I'm only learning and I know there are a lot of videos explaining the 5F1 circuit but if you did it with a wiring diagram as well, it might be a little easier to understand. It would be great to be shown what resisters and caps affect the tone, voltage readings and so on. I love your videos so much. You and uncle Doug have some of the most informative videos on UA-cam. Now he has retired your the only one carrying the flame.😀😀😀. Thanks again for all the time you give up to show us how amps work and sound. Cheers from Australia. Daniel.
Thanks for the compliments and suggestion. I have no plans on a 5F1, but you never know what will come.
I got my hands on a reel to reel tape recorder with an ef86 and 12ax7, maybe I can make something like this as a small practice amp. Thanks Brad
Cool. Outta be a good one!
purple rain. that was goooood.
RMA was the Radio Manufactures Association, later RETMA - Radio, Electronics, and Television Manufacturing Association. They set standards for parts, safety,, publications (schematics and manuals) and other things related to a common standard for members.
Webster Chicago made wire recorders, tape recorders, record changers, PA amplifiers, and complete systems (record players/radio consoles) etc. They became known as Webcor around 1955. They faded in the 60s and the brand ended in the 70s after that being slapped on pre-made stuff from other manufacturers. Once public domain the name appeared once in a while on off-brand imported junk like Crosley did in the 80s.
How come the amp makers can't make one like this that's all we want.
I think I preferred what looks like a hum-bucker guitar... the red one through that amp... just my personal preference... amazing stuff...
I think I agree in this case.
Magnavox speaker, and I'm sure it's newer than the amp.
The 6AT6/12AT6 was designed for use in the second IF of radio receivers. It was replaced in most applications by the superior 6AV6/12AV6. 45V is quite a low plate voltage; typically those run with 100-250v plate voltage.
Wish I knew a guy like you over here in the Netherlands, lol, bet there are a few though.
I got this '64 Philips portable record player with two ECC83 and two EL95 tubes in it.
Would love to have it converted to a little guitar amp and put it on the table or something...
You think the thing has potential?
www.radiomuseum.org/r/philips_ag4956ag_495.html
That would probably make a good conversion, but if I were you, I'd do the conversion discreetly and keep the phonograph intact. make it a dual guitar amp/phono.
Yeah, that would be nice.
Thanks for the reply.
freaking awesome channel you have sir!
The 6AU6 is a good choice since it is very much identical electrically to a 6SJ7. The 6HR6 will give even more gain but nowadays is rare and expensive due to its use in the FM section of high-end Fisher receivers.
Absolutely love watching your vids, I'd be intrigued to see what happens if you get a Carvin Belair or Nomad combo and indulge your creative licence modding them. :)
Great video.
The knowledge you have of amps and modding them is awesome.
Love the purple rain and your daughter is so sweet.
Enjoyed it Thanks
That Roadstar sounds great with that amp!!!
Comment made at 13:24.... I bet the cathode bias setup is also the negative feedback circuit. Off to watch the rest and see if I spoke too soon.
You must have a GOOD WOMAN Dude !
I had to screen shot the cathode bias bit. WTF, OVER?
(For the new viewers below)
Paraphrase inverters have more gain than a Long Tailed Pair but are hard to balance. The GA-40 is a perfect example for a single pentode driving a PPI 12AX7 and two 6V6's.
And GA-20T. Same as GA-40 on Channel 2. This was in the back of my mind on this one.
The Guitologist I tried messing around with large value screen bypass caps, what a difference it makes in gain levels. 680nf with a 25uf cathode bypass is better than 220k or 470k plate load resistors and half the bypass cap values. I think pentode sound better when run at higher voltage too, 220k resistors drop a 330v node to under 100v. 100k only drops about 100v.
The Guitologist I tried messing around with large value screen bypass caps, what a difference it makes in gain levels. 680nf with a 25uf cathode bypass is better than 220k or 470k plate load resistors and half the bypass cap values. I think pentode sound better when run at higher voltage too, 220k resistors drop a 330v node to under 100v. 100k only drops about 100v.
That output is very clever I think the old tube mcintosh amps used something like that.Basically the cathode voltage is in series with the output out of phase so its acting as negative feedback.
I had bad surprises with using tube-socket terminals as terminals for other parts. Some tube-manufacturers connect "unused" pins internally for other purposes...Had some surprises with 6BQ5´s of different manufacturers! So watch out when changing the tubes.
Never had that specific problem, but definitely watch out what you read online about this or that tube being compatible with this or that socket because if the manufacturer tied something to the unused pins and the different sub tube uses those pins, you might be listening to Dragonforce...and in "Through the Fire and the Flames".
Absolutely!
The specific problem occurred, if i remember correctly, when i tied pin 1 to pin 3 to be able to use 6P15P in the same circuit without changing a lot. It was kind of a test-bed circuit... Long story short, the RCA and Telefunken/Valvo 6BQ5 's have pin 1 connected to grid 1. JJ 6BQ5`s and Tungsram 6BQ5 `s don`t...Did cost me a Valvo one.
The Guitologist and what would be wrong with some through the fire and flames?
Another handy book to have is, "Tab Guide to Vacuum Tube Audio" (ISBN: 978-0-07-175321-0) All the projects have full schematics and parts lists, and several chapters at the beginning that explain the electronics of vacuum tubes, construction techniques and tools, some tube pinouts, etc...
My grandfather took the mail order electricians course from GE in the 40/50s. He had several tube radios he had built in his little shop. Man the tubes that laid around that place would be with a fortune. Not too mention the knowledge I let slip away. I had a Champ back then and he would repair it for me using all he same books I see you use. He good old days...the funny part is your resemble him in his ukulele her days!✌🏻thanks for the video
looks like grandpas space heater
haha! It totally does. What's funny is, I often look at those old metal space heaters in flea markets and such and say "I wonder..."
The cathodes of the output tubes connected to the center-tapped secondary may be some sort of negative feedback, or a hum-canceling arrangement. The 6AT6/6AV6 (or the 12-volt cousins) are usually the detector/1st-AF tube in All-American-5 tube radios; weird choice in a PA/guitar amp.
Made in Chicago 39, Illinois.... That's back in the day before zip code.... 2 digit numbers were called ZONE.... JS
Do what I got to tell you something besides being a serious guitarist you are an amazing technician and I'm a bass player but I'm about sound and I'm about old amplifiers and I have a few Little Gems here and people always say to me why do you like these low powered amplifiers because they are your best friend in a recording studio especially that I play an elaborate style of fretless bass but then I left my ass off of some of the things you say but it's a total learning experience as well thank you man, for making some of this Mayhem public!!!!!!
You guys get all the cool stuff in the US here in Blighty it's mostly crap solid state modeling amps. I would be grateful to have that little Bastard your having a look at, it looks great, front and back. Definitely cool.
I love the amp,and especially the Ibanez RS 1000 ,great video!!!
I see from your username you're a fan. Very cool, brother. Thanks for watching! I feature that guitar in several of my newer vids.
I have an 83 Roadstar RS 1000 ,I bought it in 1984 , the pickups were already changed to Dimarzio X2N and a Super Distortion for the neck pickup, coil taps , shielded , I've been dabbling in the electronic world Myself ,but not to the extent that you are... much respect!!!
The double death cap, aka peter griffins bunker busting mega ultra super death cap. Like stickin a bunch of m80s together. Holy smokes that thing sounds soooo killer.
Speaker has DC bias voltage across it? Weird output indeed. Set that speaker free from bondage!
Sounds killer with the redesign! Nice amount of usable grit! Nice Gritar work by the way.
Where can I get the probes you were using with plunge mini grabber ends???? Looked can't find..
Link is broken again. Sorry to remind you of it. Any chance to get that fixed? Haha bet you didn't think this video would have such long legs. Appreciate the help. Videos are good! Just wish you could show the actual work instead of just the before and afters. Just a major novice here. Thanks!
When I was a kid I bought an Ibanez Rickenbacker copy but couldn't afford an amp. Soon I grew tired of playing without an amp and I cast my eye on my Dad's HMV valve radio. Sat down with a lead plugged into my guitar and bare wires at the other end testing each wire in the radio until I got sound. Installed a 1/4 inch input socket and an extn speaker into the radio and BINGO my first all tube amp. It sounded great with lots of overdrive when the tubes got hot.
Jesus, that playing tho.
Interesting amp. I don't know where you pick theses units up ,so cool. I bought a epiphone senior amp fro a pawn shop, it was working good but I put a new set to tubes in it. This amp is so loud but has a great clean sound. The problem is still the reverb. Only worked couple times. I don't know how to fix amps but I cleaned it up good. What do you think of these amps.I would apr. you comment,and I wish you could do a vid. On them. Love your vids. Thanks
I had one of these. They were used with movie projectors, phonographs and as portable PA systems for cattle auctions in the Chicago stockyards. I did a trade for one at a guitar show that had low output but was clean and complete. It sat around for a few years until I found a website by a guy that had a collection of 150 small tube amps and he said this was his favorite. Brought it to a friend of mine who's really good with old crap and he got it working great and I used it for many gigs and rehearsals. Awesome amp that's fairly easy to find on Ebay. I'd highly recommend one for recording, harmonica or guitar. I'd love to hear it plugged into a 12" cabinet with a Jensen.
Silly question * 100^50000. Does anybody ever drill out the old caps put the new caps in and fill em with beeswax or similar. The old caps are always so pretty looking on the outside compared to the new ones. Delicious coloured treats !
I was fortunate I suppose, that an RCA Receiving Manual was included, when I acquired my !st lot of tubes +tester from an obsolete powerhouse that we (my job) were doing a demo on. It was built in 1957, many nos tubes I saved from the garbage, but the most valuable thing was that manual. Lots of information (as you showed), that you just can't find anywhere else. Great job Brad, on that little amp, I love the pentode tube. Don't know why, but the pentode's always have a dirtier, grittier sound when pushed to me..[[[
Most of the other books you'll ever buy on the subject of tube amplifiers are just re-wordings of the RCA Manual. Even if you don't use the tube data, just read the opening chapters and learn a ton.
That's some way strange way of doing negative feedback with that output transformer!
Also a paraphase inverter, old school.
I'd throw cloth wire junk away, anything modern is superior where it comes to safety.
Hey brad man I recently bought this very same amp. And was thinking of doing some mods to it. Of course a given with these old death cap amps is you have to switch to a 3 prong chord you don’t want to have an electrified chassis. Anyway instead of running the cable itself to the power supply I was thinking of installing an IEC inlet. This is a lot more practical than having the outgoing speaker and power cord spilling out like guts when the little door slips open. Anyway this would free up the whole top panel and I was thinking of doing some mods. The first I’d split the one tone knob at the bottom into a bass and treble. And at the top design an overdrive channel that you can turn on and off with a toggle switch. And a gain knob. Please tell me if this is a good idea or even possibly provide some schematics to base it off of. I’d be willing to pay. U have Patron?
Crumbs. Could you fix my Roland W30? And fill in my crap lead samples? soundcloud.com/jazzroc/never-over-eight-1
This is an older video now. But it's funny how things go full circle. The threaded pop rivets in the Amp are now an as seen on T.V. thing I've seen these days. As usual awsome video thanks for sharing 👍.
I wonder if some of that weird circuitry has something to do with EQ, something along the lines of RIAA equalisation. Given this was primarily a phono amp is it possible that was why it was designed like that? en.wikipedia.org/wiki/RIAA_equalization
RMA = Radio Manufacturers Association number 375, i expect you knew or know that?
A Bogen K10 has a 6AU6 input 12AX7 PI and PP 6AQ5s (6V6s little 7 pin twin brother) check it out if you want. In its original PA configuration it is mild, but with some slight modifications, it becomes a wild beast of a guitar amp. LOL With our tube amps it is always best to work backward. That is to start with the PS and output sections and then work on pre-amp and input sections. The cathode biasing of the 6V6s is unusual but it does sort of make sense if you consider that it is providing a NFB (negative feedback) loop to the output tubes instead of the PI or input sections. ;^)
Good call on the Bogen. Might have been helpful had I known that in advance. On the cathode biasing thing...I think it might also be changing the bias slightly as the tubes begin to conduct more, resistance will increase in the secondary winding, because inductors are dynamic, and therefore, the bias will fluctuate...almost a sort of compression or limiter. But yes, some NFB going on there too. In hindsight, I probably could have played around with converting it all and leaving that in place, but the amp is pretty cramped to work in. Made more sense to remove it and go with what I know will work.
Mirroring the K10's 6AU6 input configuration and TS might be something to consider if your customer is not completely satisfied. ;^) LOL Nice job!
heheheh...never know, may have to.
I've also read many complaints about the 6AU6s microphonics etc. But I've got a massive inventory of them in my salvaged tube stock. All manufacturers and production eras are present in my stock. LOL I have not personally experienced much microphonics from them in my circuits. And to tell the truth, I personally really like the sustain/gain and distortion this little pentode produces as an input tube. The other input pentode I sometimes use is the 5879, even worse microphonics IMO, and more expensive. Almost everyone uses 12A_7s in the input/preamp stage. The input pentodes sound different and not like all the other amps. LOL Another input tube that may just be my favorite yet is a 6DJ8 (low mu twin triode) in a cascode (Totem Pole) configuration. You won't see that in any guitar amps that I know of. It is mostly found in Hi-Fi phono preamps, but its clean clear output and frequency response are outstanding IMHO.
You'll notice in the video, I am biasing the front end to squeeze the most voltage gain from the stage, so I think that contributes to microphonics at higher volumes. There are no problems at all at lower volumes, and the clean tone is very nice and sparkly.
I saw what you did there... Pointing with your middle finger at 18:35... I do that too.. Except I turn it upwards and usually throw an empty beer can at said device that I'm working on...
It's not dancing in the actual rain in the Superbowl halftime with two long-legged lovelies in eight-inch heels but by golly. Wasn't expecting _that._
ı say there is definitely a market for amps this size that sound like this, Every electric player needs one. Big cograts :))))
The ending is AWESOME so beautiful! They grow up so fast, enjoy every second. THanks
33:00 Pretty cool the way the leads glow like that. not sure which kind of lighting you were using back then, but makes for a cool effect.
Blind Nuts is what they are called I believe, and you're a braver man than I shushing a female. Would that thing have the output for the 4x12 it's sitting on?
Yes. It would push it, not hard, but it would push it.
Lol let the wife speak 😂
Damn that sounds sweet! No high gain amp or any pedals can give that kind of tone!
And yes, pentode preamp tubes fell out of favor for the dual triode due to the difficulty in finding ones that were not microphonic. Unfortunately, although easier to find, the dual triode doesn't touch the tone of a good preamp pentode.
I agree. A pentode up front gives a certain rawness and sparkly character on the top end. It's more...ALIVE.
Those plastic coated capacitors are still a paper type in a fancy case rather than a heavily waxed outer layer. The little bastards are such notorious leakers the usual approach is to shotgun them. At worst they can cause the output stage to self destruct by putting a positive voltage on the 1st grid of the o/p tubes.
Awesome little vintage amp and sounds pretty good, what did you ever decide to do with that Washburn that you repaired the head on? Do you ever sell any of these things that you repair and or fix ?
That biasing of the output tube cathodes via the transformer output centre-tap is just a simple way to do local negative feedback on
the output stage. After all its a PA amp so was designed to be low distortion.
+Mark Tillotson I agree
The ending was the icing in the cake. What a touching moment. My two kids are grown and its moments like that when a parent wishes their children were that age again when you have to bend over with open arms for that great hug. Enjoy these moments as much as you can, they grow up fast. Rock on brother.
Thanks, Gil. I don't deserve her. That's for sure.
It's Mega Death,,, hahahaha
I own one of these amps. Excluding the value of the amp,what did this build cost? I want to get my amp built.
They aren't rivets, they are nut-serts/inserts. 🙄
Yeah. I am pretture sure the backs could be rounded down with a proper tool to hold like a rivet too.