3rd gen 50w build

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Fictitiousfreedom
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3rd gen 50w build

Post by Fictitiousfreedom »

Hello my amp obsessed friends!
About three years ago i decided i was ready for a scratch Dumble build. After starting the early work i had a horrible accident and shattered my pelvis, it took me almost a year to relearn to walk ect so i was stuck in a chair, eventually i decided to build the Tweed Overdrive Special from the guys at the EL34world forum. The fact that i assumed that would be an easier build shows that i was not ready for the dumble. I used that amp as a learning tool, its no longer a TOS, keep an eye out for a post soon about the Tweed Super lead special. I digress.

I have never been so patient or careful with any of my projects as i am being with this build. So far only a few tiny errors. I created my own layout which ill post when i know its correct. I have developed a pretty fast way to make to scale layouts which can double as a drill guide for the chassis and boards. I really just blew up tonys layout to fit my chassis and placed everything in Affinity Design. I wanted the handful of changes i made to be on the layout and maybe someone else might find it useful.

I had started to collect some nos parts although the 5uf tvas are all I'm using. I was getting ready to buy 2 sets of resisters from jelle last week when i received the news that the owner of the business I've managed for 15 years hasn't been paying his taxes. Lets just say ill have some free time to sort my modern production equivalents. 🙃 i mostly have current Dale CMF60, Ohmite OM series CFs, and a few KOAs. Im using CDE filter caps because the Spragues are like 18$ a piece now!!!
ODs are all the polyester variants and ceramics are all Vishays.

The first mistake i made was my first order, i somehow saw the relay as a 3PDT. Im using an “ice cube” style so i bought the socket, mounting plate, and metal strap. Im pretty sure its fine and will work but im scared to look deeper into it. Although Im at the point where i need to know 🤞🏼 also I can’t think of a use for that third switch but if anyone else can let me know.

The second mistake i made was with the foot switch jack. I bought a 5 pin nos neutrik xlr jack and plug awhile back. Cant find the data sheet for the mounting hole, it is a wonky shaped jack and so i just drilled a big hole and filed in the notches. Not much of a mistake but the ugly hole bothers me. Im aware its not necessary but i plan to keep the possibility for more relays open.

The only other thing so far has been when i had my face plate made, “front panel express” i ignorantly made all of my holes exactly the same size as the shafts ect. Luckily i was maniacally anal when machining my chassis so everything fit perfect.

I chose slide switches because i like them and i have a ton. I added the FX return because i have a d’lator. I plan to add an fx loop bypass relay and add a switch on the pedal once everything works. I bought the chassis on Reverb from Synaptic amplification, i asked him to make it as big and wide as possible, i ended up with a chassis that measures 21” x 10” x 2 3/4”. Lets just say for once i have a lot of room. I had him add the iec, power xformer cutout, and mounting nuts because he offered that service for not much more. Im very satisfied.

The head cab will be based on the typical Dumble style scaled up for my chassis. Im using solid pine, dovetailed, covering will be black suede and im using orange leather instead of grill clothe. My thought was to make it as close to an original ODS as possible at first but to make it look and sound like what I would have ordered from Dumble in the 70s if i had been able to. Although idk if he would've done a black and orange faceplate 🤷🏼‍♂️. I want to do a SSS in the same fashion at some point.

Its said often but cant be understated how incredible this forum is. I believe in the future it will probably be archived and used as a historical as well as an educational resource. I don’t know of anywhere else with people that are so gracious with their time and experience and i for one feel lucky to even be a tiny part of that.
Thanks for checking out my build guys!
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Camden

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Fictitiousfreedom
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Re: 3rd gen 50w build

Post by Fictitiousfreedom »

Also forgot, i somehow managed to not order the 22k for the first grid of V1 so i subbed a 33k until i get the correct value. Same with the two 270k, i had CCs so thats what i have in for now.
Camden

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ijedouglas
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Re: 3rd gen 50w build

Post by ijedouglas »

Looks great!
Ian
Fictitiousfreedom
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Re: 3rd gen 50w build

Post by Fictitiousfreedom »

ijedouglas wrote: Tue Apr 02, 2024 7:12 pm Looks great!
Thanks man! Ill post my progress as i go, probably only a few days of work on the amp and a few more on the head left. Cant wait to fire it up!
Camden

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Fictitiousfreedom
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Re: 3rd gen 50w build

Post by Fictitiousfreedom »

Alright, i still have some work to do on the head cabinet. I opted for solid pine because i like dovetails and i can do them quicker than most else. Its gonna be heavy! Im going to attempt to make a handle and the corners from the leftover orange leather but it needs to be strong.

First time turning it on i got a very loud hum. Missing ground for the power supply filter caps 🫠 after adding it everything works as expected. It sounds great! Like really really great, i was kinda shocked. Maybe you guys can relate but after a year of planning and obsessing it feels weird that it works so well, its a difficult feeling to express.

The bright switch is almost always too bright which is a shame because it is needed sometimes. The deep switch is very useful, i personally love the accent switch, and despite hearing it wasn't great in this circuit if i place the rock jazz switch in between the two i get the PAB boost and it also sounds great! I am very surprised at how different the character is from just bypassing he tone-stack vs the Rock/jazz modes. I plan to just sit with the amp like it is for at least a month before altering anything at all but i for sure need the bright mellowed just a tiny bit. I also have been toying with the idea of the PI trimmer, i almost included it but i wanted it as stock as possible. I also may add an impedance selector switch. Im running it on the 4 ohm tap but with an 8 ohm load, i read that was the way it was intended to be ran and after trying both it was clear. I have a live room with my cabs in it and i like to run another cab in the control room sometimes so ill need the switch.

My foot pedal is an old acoustic brand that ive had forever, it was basically perfect. I could've even used the original connector but didnt.

One thing that i don't like is the volume difference between clean and overdrive. Clean is much much louder and the only way to balance it is by turning the OD up which isn't ideal. I assume this is why people add the master volume but wanted to see if this is in line with how it should be.

Lastly, my FET is not working, it makes sound but its very very quiet and distorted. I biased my FET via Martins document but i still dont know what is up with it.

Ill post sound clips soon as well as more pics when my cab is done. I also am including my layout, i went over it a lot but im sure i missed something, i noted in the layout that my FET isnt working but its the same as Tonys layout so it should be good. If anyone spots something ill revise it.

Thank you to all of you incredible people! This year has beaten the dog shit out of me and Ive dreamt of owning or playing an ODS basically my entire life and if it wasn't for this community that would have not been possible 🥺 so again THANK YOU!
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Camden

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Fictitiousfreedom
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Re: 3rd gen 50w build

Post by Fictitiousfreedom »

Here is my layout.
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Last edited by Fictitiousfreedom on Fri Apr 12, 2024 6:50 pm, edited 1 time in total.
Camden

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xtian
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Re: 3rd gen 50w build

Post by xtian »

Fictitiousfreedom wrote: Thu Apr 11, 2024 10:56 pmThe bright switch is almost always too bright
By all means, choose a smaller bright cap!

Nice work!
I build and repair tube amps. http://amps.monkeymatic.com
Fictitiousfreedom
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Re: 3rd gen 50w build

Post by Fictitiousfreedom »

xtian wrote: Thu Apr 11, 2024 11:20 pm
Fictitiousfreedom wrote: Thu Apr 11, 2024 10:56 pmThe bright switch is almost always too bright
By all means, choose a smaller bright cap!

Nice work!


Thank you! Good point, my inner urge to start going mad scientist is very strong at the moment so i was trying to abstain from any modifications. I had almost forgotten what abstinence normally leads to……. :twisted:
Camden

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xtian
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Re: 3rd gen 50w build

Post by xtian »

Fictitiousfreedom wrote: Fri Apr 12, 2024 6:43 pmwhat abstinence normally leads to……. :twisted:
Abstinence makes the fart grow stronger?

Anyway, yeah, building a one-off amp from a recipe is only the first step! There will always be tweaking after the build is completed, whether to meet the tastes of the builder or the client.
I build and repair tube amps. http://amps.monkeymatic.com
Fictitiousfreedom
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Re: 3rd gen 50w build

Post by Fictitiousfreedom »

xtian wrote: Fri Apr 12, 2024 6:46 pm
Fictitiousfreedom wrote: Fri Apr 12, 2024 6:43 pmwhat abstinence normally leads to……. :twisted:
Abstinence makes the fart grow stronger?

Anyway, yeah, building a one-off amp from a recipe is only the first step! There will always be tweaking after the build is completed, whether to meet the tastes of the builder or the client.
Yes, until eventually………

My last build i tweaked until it was a completey different amp. I changed basically every component and i learned an insane amount of theory through that process. It was a tough one, it had a parallel gain stage with pot, and a pentode gain stage. Using merlins book along with load lines was so educational. That being said, it is a dumpster fire. I have pretty bad OCD so this one being so pristine makes me feel good every time i look at it.

I swapped the bright cap for a different brand of the same value. I believe it is an ohmite ceramic, it helped a lot but still a little bright. I may try a 250-370pf tonight.
Camden

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