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You should check out the "shift" pull switch on the treble knob of a Mark IIB mesa amp. It makes a big difference in tone which is difficult to describe but it's very nice.

Remember the Mantra for moronic guitarists... Tons of filtering in the power sections and Oversized Linear trannies Maketh Fender Silverfaces Garbage but Maketh dumbles GLORIOUS

Listening on earbuds, sounds like it added some bass and maybe fattened up the tone a smidge. Didn't necessarily sound like "pixie dust," i.e. maybe you can get the same result with the existing tone stack?

anyone notice the spider around 15:30 that crawled on to the amp? i think the spider noticed a difference.

Call me crazy, but I hear practically no difference whatsoever. I'll try it in one of the next amps I build to give it a try so I can hear it closer and live. Side note,... try to keep your component leads and wiring only as long as absolutely necessary. It can cut down on hum, noise, and picking up interference in some cases. Good video. Have fun and be safe folks.

Hey, Sir. You & i have some parallelism. we like to tinker on tube amps. i did a similar test w slightly different beasts. 20+ yrs ago i built a 2x6l6 tube rectified amplifier from a kit from Dan Torres. I barely knew what end of the soldering iron to grab. but hey i'm me & me can do anything. so off we went. to epic fail. the amplifier did work but i didnt need to learn any songs because the amplifier hummed them all for me. lol. it was unplayable as it was. I sent it to a tech & he couldnt figure it out so it sat for 20 years. fast vfwd to youtube, uncle doug, & others. w new education i decided to rewire the whole thing & because of my already owned transformers i decided on a 5f6a bassman circuit in a 1x12 combo as i could reuse all the expensive stuff & nonly needed small stuffs. one winter & about 10k hrs later, TADAaaa waaay better results this time. a few small ground loop hum repairs, a few rookie moves corrected, & i've yet to hear a better sounding amplifier. The old torres spec had me with hammond transformers output 1650n. more trans than i needed, with way more current handling capability dual wire-secondaries,( dont ask) ultra linear taps & 8lbs. well, if you want it to distort sooner youd probably surmise that the 5f6a spec'd o/t at half the weight may help that situation. i have in my arsenal a JTM-45 Backbreaker combo re-issued. it has an o/t capable of 2 6l6 in push pull & its half the weight.. so off we go & here we are. I didnt have a lot of expectation that it woul be much different tonally but i did expect it to compress & sag a bit sooner. NOPE. lol to be fair i havent taken it anywhere i can un-leash it so this critique may be a bit premature. i am curious if you weighed the two transformers to see if they were spec'd the same?.. great content by the way. very relatable.

Killer parts, Thordasen, one of THE greatest transformer cos EVER, These guys were born in early 1900s great men, =great parts n engineering!

I think that you did a good job with this video. Just mho, but the Thordarson is a very good tranny. Again, imho the ‘68 tranny is not the same as an aa864 Bassman tranny. If you can acquire a Bassman tranny from 1964, I know that’s not easy, but I think that you’d find it better sounding than both of these. Ask me how I know!

5he blue Sozo sound right for that amp. The red Jupiters are great too but maybe for a Tweed combo for a warmth and rawness? Combining both is a good idea..it could keep you busy for years!

I grew up in Santa Cruz and I had a crazy drummer friend who asked me if I wanted to go watch a guy build amps over in Pleasure Point. I said “why would anybody want to do that?” D’oh!

just think if dumble had done that mod to your amplifier it would be worth 50 grand ..

‘To see one in the wild like that’ 😂 Vintage tube amps are truly living creatures.

OD 715 - 716 are bad in Fender amp, PS series are fine, and 225P is the best. But if you can find old 160P polyester capacitor or di-film Sprague it is the best ! Other fine option are the K-42 russian caps

I've tweaked some amps for a friend. He asks me always to step up the OT, 50W Bassman OT in a 40W Bandmaster, 80W Twin OT in a 50W Bassman... He finds that the sound is fuller with a beafier OT and becomes less muddy when cranked.

Bigger resistors are usually fine, sometimes u can get hiss off them. I use metal oxide in all my blds. I have heard other techs say there noisy. I haven't noticed any difference and 1 watt is fine for everything but powersupply resistors. Ive used 1/4 for like the 1meg resistors on the input to see if it was quieter, i noticed no difference.

how about a 58 triad?

The jupiters are darker I like the sozos.

i dont know if youd welcome any info from someone who is by far an amp tech per se, but you may find it helpful. you should try a hotter soldering iron, or turn the heat up on the one you have. not only will it be easier to work with, its better for the components. its better to get in & out with a hotter iron than to let parts heat soak with a cooler iron. the iron i use melts those solder joints that you were working with instantly. that said, the amp sounds good either way.

IMportant: Difference between what orange drops you use, the ones made from polyester as a dialectic material are the ones you want, sprague 6ps or 10ps(not all values), are the ones you want. "orange drop" 715p are common now, but very bad in comparison.

Sounds great

That’s all he did ?

R1xR2/R1+R2 = R total. Handy equation when dealing with differing resistor values. I wonder if the mod has a noticeably bigger impact at higher volumes. Takes off too much bite for my taste but maybe it would be useful playing in certain situations. These kinds of mods were invented at a time when there was a lot less control over live sound.

Yeah, Santa Cruz! nice video learned a lot. Thanks for posting it.

Nice one thanks

Cool, I knew Jack. I played one at gadget box studios when I lived there.

Is this mod suitable for a solid state amp?

this only makes a difference when cranked up LOUD on moderated levels you need a special ear to hear it and have both playing next to each other .. and switch between them while playing , anyway its fun to investigate once you are aware of it and know your needs then you can decide what to buy the next time, have fun , cheers

HaHaHa - holy shit indeed. I've done that too. I can't hear much of a difference. Definitely not enough difference to pick one over the other listening to TH-cam compressed audio.

I love the sound of P90's I have a set of Dylans and a set of Duncam Phats. I've a set of Mojotone Humbucker sized P90 going into a build in progress. I'd like to try the Fralin's now as well. Nice demo - thanks. Gotta love living in Santa Cruz. I'm in Soquel.

Using chassis as a ground point to components is usually not a good idea. Isolate components from chassis and finally connect ground of that circuit to the exact point of circuit that those components are affecting to.

Good job! Might just be camera angle, to me those 6L6 look huge. Much taller. Are they 6L6?

I've swapped out a couple of output transformers. Mostly for beefier OTs. When played at moderate volume, it didn't make much difference. The difference in sound was what happened when cranked loud. The different transformers had different distortion character

Hey Chip! I grew up in Saratoga. Cool to see someone in Santa Cruz. I'm in Long Beach now. Mom lives in Campbell. For $13, Mojotone has a 1MA CTS push-pull pot that I've used to replace the bright switch since Fender used a DPDT slide switch when they really only needed a SPST for the bright cap. You could re-enable that bright cap with that push-pull if you swapped it out for the original pot. The shaft on the push-pull is a bit longer. It will require some shaving down. Cheers!

My friend recently gave a 65 Bandmaster head. I am planning on going through the amp and replacing electrolytic caps, drifting resistor values, clean pots, etc. Full restore if you will. Now I am seriously thinking about putting this mod on the list! If I do I will let you know how it sounds. Thank you for this!

Thanks for sharing….I see something that needs to be checked… the photos of red covering on tube sockets… the socket furthest right side has a grid resistor which looks cooked to me. That can cause a transformer to fail…. You can look at brown carbon comp resistors on the tube socket those are grid resistors and they need to be 100% to avoid failure. That grey ash looking stuff is carbon and it needs to be cleaned off and that resistor replaced ,,, Those are gonna be old and bad anyway after that long of time…. So you dont want arcing there at all… The others dont look cooked but that means nothing since they were all done at same time… I would check the cap pan look at caps under cap pan dont touch they can shock you badly but take photo maybe or get them to check the caps If bubbled ends or leaking they need replacing also.. CRUCIAL TO MAINTAIN IT…. looks like 1.5k 5% 4.7ohm 2% blue resistors on tube sockets..those close tolerance and flame resistant also….. its pin 5 that might be an arching tube so the entire socket should be cleaned re tensioned all the carbon cleaned off it scraped off and solder cleaned out and part replaced with NOS values…. id do all of them at same time all the brown barrel carbon types on pin 5 …..Id bet once that is unsoldered it is broken through the colors or bands…. they get hot and break that way or blow up entirely breaking in half cooking worse… So you want to tell them to get on that clean all sockets re tension all tube sockets cleaning them alcohol after scrapping that off with solder tool… Id check the main filter caps 1st thing then go ahead and replace all the GRID RESISTORS and if MAIN FILTER CAPS ARE BAD REPLACE THEM and the Dropping strain resistors next to the Main filter caps… Those are also brown barrel types and common in fenders….they filter out noise … Those are all old and drifting at this point.. ** replacing main filter caps after 10 years is crucial anyway and it restores the power in all the ranges…the potentiometers or tone pots really come alive and the amp wont fail…. arching in tube sockets is instant death to a transformer and it might kill the person playing it especially if not grounded well with standoffs and the dang death cap being removed.. Large blue Mallory cap near the standbye switch.. DO NOT TOUCH IT….. DO NOT TOUCH MAIN FILTER CAPS EITHER …. The safe way to discharge those is unplug amp turn off and stand bye off take screw driver cross both positive and negative side of plug without touching screw driver part touching each side you can flip both switches and it will drain the charge from main filter caps so you can remove and replace them and not be shocked. DONT TRY THAT AT HOME IF YOU DONT KNOW WHAT YOUR DOING.. If this is in a shop they should know a tech qualified to do this work. its Crucial to have clean solder connections and pin connections and ive seen tube sockets arch internally between pins and thats bad news while playing the amp…. The mod of removing death cap helps prevent that from happening. I owned a Dumble bassman and it still had original death cap in it. Non grounded plug. I know exactly how to fix this amp and I just described how.. Simple repair crucial to the life of the amp and the overall tone and sound is everything. So you want all filtering caps working 100% and main filter caps also bias caps and diodes. The problem this amp will see is failure on one tube socket and soon as bias drifts to one side its going to roast the transformers and there goes the tone….. So prevent that by servicing this amp at once… Id be sick if that amp burned up or went down or worse hurt someone playing it thats dangerous to neglect so I pointed it out. By replacing Main caps if needed and these filter caps or grid resistors the tubes wont roast either…. you will just keep roasting that one tube till the transformer goes . Might catch fire or electrocute the player so not worth that… Those parts are easily found the brown barrel resistors are cheap quality id put ceramic as grid resistors especially since he upped the transformers to twin style 100 watters… those dissapate heat might put marshall style there… square white ceramic style or green barrel types good parts……. the blue resistors are close tolerance. he wants specific readings on the bias at bias board and at pin 5……you do not want the grids drifting out of tolerance… Id like to see the main filter caps under the cap pan and I spy some other type clay looking tan color caps or resistors mustard colored disk shaped types those and the blue flame retardant close tolerance Dumble would buy in bulk….id need to see the main boards Id bet orange drop or brown drop or blue drops.. Mine had orange drops and some other specific parts which were seen in other builds he did near that time…. mine was not smurfed…. recapping this amp and a tweak on the preamp tubes and even running it with a brown box is essential … The voltage at the wall is everything to a Dumble amp. The preamp tubes and voltages all matter so the parts must be maintained to proper specs and original maker if possible it matters… id not put F &T Caps in this either.. no way harsh and sterile sounding….. been there tried that…. you want specific wall voltage to the amp only way to ensure that is variac or brown box and brown box you can lower % and voltages without having to rebias the amp ! So you do that clean the tube sockets up check and retension sockets clean them out well spray cleaner and pushing tube in and out cleans them out well after re tensioning the sockets… There are some items he used at input and on tone stacks as mentioned. There are some changes on caps or resistors which change the cleans for the better .. a well tuned Dumble should sustain on the clean side straight in…. This amp needs service its dangerous to leave that resistor unchecked it will roast that tube and might take the transformer out. that means output transormer also ! DONT LET THAT SMOKE OUT SMOKEY BEAR SAYS ONLY YOU CAN PREVENT FIRES SAVE THE DUMBLE PUT OUT THE FIRE CHIEF… I can share some tips with tech if needed Im in Texas. I did repair work for major amp shops in Austin Dallas San Antonio and Houston most were sent into Austin to repair and ive done my own work since… This is a simple fix and it will improve the over all tone and reaction of the amp and the brown box and the right tubes will blow your minds. Raspy sounds brittle or to thin and the tone knobs reacting poorly or seemingly not doing much is a tell tale clue it needs caps…. I know it needs them they all do… and this one is roasted on that far right tube socket…. id call them tomorrow and tell them I spotted this and thought I should speak up. Tone is everything and so why not preserve and maintain it… I learned alot studying mine… The red anti arching paint also showed Dumble if the solder joints were tampered with or not if so he would not work on it again…. Mine had a different color on the solder joints. He hid resistors and wires and shrinkwrapped them hiding them beneath the boards to throw off discerning eyes. To see some of it took staring at it for hours and measuring or cross referencing schematics or layouts … Mine was a complete rebuild vs mod… ive seen inside several of these…

Very cool video and amp!

32 seconds?

Hi, thanks for the video. In my opinion(smartphone audio)the tube are the same in High and hi-mid. And RCA Is Better in bass. The Wing are Little more Dynamic and the RCA are Little more compressed. RCA have more harmonics. I prefer for clean music wing and for all the other music RCA. It could be a bias different perhaps increasing Wing bias(more warm) It could be more similar to RCA(only for headroom and bass but not for compress. I dont know for harmonics) best regards Paolo

Sozo's are probably more authentic and true to the originals, but Jupiters sound much better. Listen to that bottom end.

Stupidest shit I've ever heard of. Pansy scared of a soldering iron? So dumb. So fucking stupid.

Most likely a mid-boost and possibly a low end cut, making room for the highs in the signal. The extra output tubes are just that, more headroom. Also, the output transformer could very well be original: Fender Blackface amps & early Silverface amps used cloth covered wire until sometime in 1968

Nice speaker cabinet, the secret to the tone is the lid of shake taped taped to the inside

What makes that a Dumble? It's hard to see in the video, but there don't appear to be many changes.

Just listening to the amp nothing sounds special about what i just heard. Dumble or not. Even an original Dumble is not worth what people are asking for them.

😂 Hahaha, listen to yourself, you sound like a disciple who thinks he's found a holy relic. Man, it's just an amplifier. Chill down. All that Dumble hype is beyond ridiculous. By the way, I also own a 1965 Bandmaster. These sound great without any ominous mods. I even think they sound better stock. I mean, watch your own video: Your Bassman obviously sounds better. My Bandmaster breaks up really nicely at around 7-8 and has much more character than this flat sounding thing in your video. Here's a tip: If you can't help but look for a holy ghost kind of figure to worship, how about Leo Fender? I think he knew a thing or two about good sounding circuits. A BF Bandmaster is very fine as is.

At first glance I see a bunch of stuff going on at the normal channel controls. Can't see what. I know they came wit four tube holes, two with covers.

I lived in santa cruz in the early 70s. Howard Dumble had a shop and worked on amps. He stacked the preamps and put a master volume in a blackface fender showman for me. I'm sure it was one of the first amps he modded. I wonder what it would be worth now with the receipt.

SA is great being so close to syntaur

Amazing

I’ve tried the Orange Drop to Sozos before too in a JTM45 build and a Princeton build, and it as very noticeable. I think this red vs blue is noticeable but very subtle, and which one you prefer will depend on the specific circuit and what tiny shifts you want to achieve. I’m assuming the parts were value matched (within 1%) which is how I’ve done my testing.