ODS - any advice?

[norburybrook]

I've just built an ODS combo with a built in dumbleator. It's an extra tube and some parts to fit in but makes for a grab and go amp.

You have to remember your real master volume though is now on the back panel


M

[Stephen1966]

That's great M. Do you have any pics/schematics? I'm pretty sure I want to build the Dumbleator and it was the plan to partner it up with the ODS when I first thought about this project. I guess the advantage of the rack unit (thinking of Martin's mini-me) is that you can plug it into any passive looped amp and I was thinking about that for the Tweedle-D but I really like its rugged simplicity and I'm loath to modify it much further beyond its original conception. Though being a 5E3 base, it's already been modified. Modest changes really. The ODS is a different kind of beast though and it seems worth forsaking that kind of rack/cab modularity for an amp which is practically speaking, self-contained and dynamic.

[FUCHSAUDIO]

Nice to hear from you again Andy.
As far as how break in changes the sound of the amp, I have also become a big believer in this. Ever since I have been running my new builds with a signal generator and a dummy load I have also noticed an increase in warmth in the sound of the amps. When I compare the new build that has almost no playing time to the ones that have been running for 15- 20 hrs the difference is noticeable.

Cheers

Guy

Try simply running the amp into a load with the randomness of a radio, for a few days........

[drew]

I've just built an ODS combo with a built in dumbleator. It's an extra tube and some parts to fit in but makes for a grab and go amp.

You have to remember your real master volume though is now on the back panel

Or build it this way:

https://ampgarage.com/forum/viewtopic.php?f=4&t=20551

[Guy77]

Nice to hear from you again Andy.
As far as how break in changes the sound of the amp, I have also become a big believer in this. Ever since I have been running my new builds with a signal generator and a dummy load I have also noticed an increase in warmth in the sound of the amps. When I compare the new build that has almost no playing time to the ones that have been running for 15- 20 hrs the difference is noticeable.

Cheers

Guy

Try simply running the amp into a load with the randomness of a radio, for a few days........

Thanks Andy! I think I read about that method on this site as well.
I saw a video were Dr Z burns in his tubes and the amps they are in for 48hrs on a pink noise signal generator.

Guy

[Stephen1966]

Talbany wrote

Reverb/Built in loops/ and other mods and tweaks that the general public perceives as a more flexible/Marketable/ user friendly amp all the while straying further away from the sound of the original design. Many of these builders will get around this by saying "I have my own sound" I am after.(Ya Think!)

It's true, I have my own sound, and this is something like a springboard. A concept amp, with tone and frequency richness, for want of a better word... I was listening to some guy demoing a Dumble clone against pedals, I wasn't enamored with the pedals even with EQ tinkering. But the amp itself (sorry, don't know which serial number it was based on) has something quintessential going on, I can't put my finger on it. Clear, yet warm, deep but not muddy. I think it resonates with the kind of music I like to play. Rock and blues. I like the SRV SSS vibe as well, but that isn't where I go musically. I'm not sure marketability has anything to do with it, I'm not making amps for anyone but myself. I think you're right about the possibility of it all going south when more mods are added, but it really makes sense to me to have a little bit of forward thinking about this and design in features that I want to use. That may result in a less desirable sound initially, but the good thing about putting your own amp together is that you can change your mind on some aspects of the circuit and try different approaches if it isn't up to snuff the first time. No warranty to void!

[Stephen1966]

Norburybrook wrote

I've just built an ODS combo with a built in dumbleator. It's an extra tube and some parts to fit in but makes for a grab and go amp.

You have to remember your real master volume though is now on the back panel

Marcus, this may be a schoolboy question, I confess, I haven't done my homework on this, but is there any reason that a dumbleator "master volume" couldn't go on the front panel? Courtesy of a switch connected to the loop and the master volume there? I'm not afraid of making my own chassis, laser etched front panels are easy enough to source if it involves any extra controls.

[Stephen1966]

I'm putting a link to this thread here... for future reference.

https://ampgarage.com/forum/viewtopic.php?f=4&t=30186
https://tubeamparchive.com/viewtopic.php?f=4&t=29813

[Edit: these are references to onboard dumbleator and reverb circuits]

[norburybrook]

Norburybrook wrote

I've just built an ODS combo with a built in dumbleator. It's an extra tube and some parts to fit in but makes for a grab and go amp.

You have to remember your real master volume though is now on the back panel

Marcus, this may be a schoolboy question, I confess, I haven't done my homework on this, but is there any reason that a dumbleator "master volume" couldn't go on the front panel? Courtesy of a switch connected to the loop and the master volume there? I'm not afraid of making my own chassis, laser etched front panels are easy enough to source if it involves any extra controls.

well, I'm far from being an expert on these things so take this in that spirit. In theory there should be no reason you can't fit the pots any where you like, howver when building my amp I wanted to have a bypass switch as the dumbleator is permanently in line but regardless of how I wired it it added significant noise to the amp. I tried Shielded cables, various runs to and from the switch including flown leads , long runs on the chassis edges, short direct runs but in the end had to give up. Yes the switch worked as expected but the cabling added noise.

M

[Stephen1966]

Norburybrook wrote

I've just built an ODS combo with a built in dumbleator. It's an extra tube and some parts to fit in but makes for a grab and go amp.

You have to remember your real master volume though is now on the back panel

Marcus, this may be a schoolboy question, I confess, I haven't done my homework on this, but is there any reason that a dumbleator "master volume" couldn't go on the front panel? Courtesy of a switch connected to the loop and the master volume there? I'm not afraid of making my own chassis, laser etched front panels are easy enough to source if it involves any extra controls.

well, I'm far from being an expert on these things so take this in that spirit. In theory there should be no reason you can't fit the pots any where you like, howver when building my amp I wanted to have a bypass switch as the dumbleator is permanently in line but regardless of how I wired it it added significant noise to the amp. I tried Shielded cables, various runs to and from the switch including flown leads , long runs on the chassis edges, short direct runs but in the end had to give up. Yes the switch worked as expected but the cabling added noise.

M

That is interesting. It really sounds like you spent many hours trying to figure this problem out. To give up must have been bloody annoying. It sounded like a good idea in principle. It still sounds like a good idea. But the cable! Even shielded cable. You know this may have been why Dumble didn't include the dumbleator in his ODS. When you say 'noise' though, are you talking about the 60Hz kind? Or something more exotic? I ask because when I first thought of this I was thinking it might be an idea to put the filter caps in a doghouse but it sounds like you've investigated all the options. A picture, if you have one, might tell a thousand words. The cable run through a bypass switch itself can't have been very substantial, even the long runs so I guess it rules out impedence in the cable as a source. You got it to work though, that's something.

[norburybrook]

check out my build thread.


https://ampgarage.com/forum/viewtopic.p ... &start=165



here's the page with the bypass switch episode.



M

[Stephen1966]

check out my build thread.


https://ampgarage.com/forum/viewtopic.p ... &start=165



here's the page with the bypass switch episode.



M

Thanks Marcus, that's a lot of information. It's going to take me some time to understand it all. But you gave up on the bypass switch in the end? Looking at the photo, that cable was pretty substantial and while routing it removed some of the noise it didn't remove the background hum if I understand correctly. You did mention that your signal through the loop had (has) a higher gain though. Did you consider that the noise may not be coming entirely from the position of the cable, that it's present already in the clean channel and that the increase in gain might only be amplifying it to an audible level? I guess it's all water under the bridge for you now but you clearly know that even if we say, 'that's it, I'm finished,' we can't leave this stuff entirely alone. The noise came from somewhere. To me, it doesn't seem that choice and run of cable was the whole story. It's an intuition, you understand, I don't have the technical know-how that many of you have.

[norburybrook]

I think there's a reason Dumble never put a Dumbleator inside the ODS


I tried but couldn't make the bypass switch work without added noise. YMMV of course,

I seem to remember TAlbany mentioning a similar experience.



M

[martin manning]

If I were doing this, I think I would keep the master volume electrically at the power amp input, and physically on the front panel. That would mean adding a fixed attenuator in front of the D'lator send buffer stage, so the MV would replace the "recover out" pot on the D'lator. The send level and recover input pots in the D'lator would be preserved, and located on the back panel. A bypass switch could be used to jump over the whole thing (the fixed attenuator and the loop), connecting the preamp output directly to the MV, same as in the case when the loop is not being used in the original circuit.

[Stephen1966]

If I were doing this, I think I would keep the master volume electrically at the power amp input, and physically on the front panel. That would mean adding a fixed attenuator in front of the D'lator send buffer stage, so the MV would replace the "recover out" pot on the D'lator. The send level and recover input pots in the D'lator would be preserved, and located on the back panel. A bypass switch could be used to jump over the whole thing (the fixed attenuator and the loop), connecting the preamp output directly to the MV, same as in the case when the loop is not being used in the original circuit.

Hi Martin, I'd be willing to try that! Would any fixed attenuator do the job?