Nobelium - tube bass preamp project

I just bought the transformer this evening but still need to get most of the caps and tubes.

Is there any benefit to using long plate tubes here? I don't know if it's the mojo talking but I've read that long plate tubes have better bass response. Just wondering if it's the extra few dollars. I'm buying the tubes for my B-15 at the same time so the extra $40 or so doesn't seem that bad in the cart at Tube Depot 😂
 
Audandash said:
I purchased a handful of the xlr jacks so i have a few i can mess up, lol. I will get that sorted before i solder the transformer. Since i dont usually use those jacks i purchased more as a just in case. Plus i figured like most projects i do i would end up building more than one. One normal and one for mods etc. So it wont go to waste. I do wonder about that board getting held to the side of the enclosure with just two screws. It seems like they are supporting the jack, transformer and switch. And since the switch is board mounted it doesnt really offer support. Does this put a lot of stress on the plastic housing and screws? It seems if you flip the ground switch it will push in a little inadvertently and put stress on the same two screws as well. Have you though about some sort of standoff to give the switch side of the board a little more strength? I apologize if i am rambling. I already took my ambien and i am getting tired fast.
Click to expand...
It's a legitimate question, it's something I've been thinking about. But I'm okay with how it works for three reasons:
  1. The boards fit together with a fairly small amount of room so the daughterboard doesn't have much room to go; if you push too hard on the switch it butts up against the main PCB, offering some support there
  2. I've tested it a bunch and haven't had any issue with it stripping. Part of this I'm sure is due to the fact that Amphenol has that piece of metal in each of the plastic holes, partially for support and partially for chassis grounding connection.
  3. This s how Noble does it too. The original Noble has the D.I. transformer and ground lift switch mounted to a daughter board which hangs off the enclosure by the XLR mounting screws. If it's good enough for Noble, it's good enough for Nobelium.
It seems counterintuitive, but I would actually recommend soldering the transformer first, then you can space the pins of the XLR jack such that it's as snug a fit as possible against the chassis without cantilevering it. Not essential, but it's how I did it. Seriously, I promise I'll have a build doc soon.
peccary said:
I just bought the transformer this evening but still need to get most of the caps and tubes.

Is there any benefit to using long plate tubes here? I don't know if it's the mojo talking but I've read that long plate tubes have better bass response. Just wondering if it's the extra few dollars. I'm buying the tubes for my B-15 at the same time so the extra $40 or so doesn't seem that bad in the cart at Tube Depot 😂
Click to expand...
I'll be honest with you, I have no idea. I'm a big fan of tube rolling and I personally hold that different brands can sound different than others, but I've never experimented with long plate. B-15 is neat, there's a guy on Talkbass that tells me I should use 6SL7 for all of my pedals. I consistently tell him no :P
 
peccary said:
I just bought the transformer this evening but still need to get most of the caps and tubes.

Is there any benefit to using long plate tubes here? I don't know if it's the mojo talking but I've read that long plate tubes have better bass response. Just wondering if it's the extra few dollars. I'm buying the tubes for my B-15 at the same time so the extra $40 or so doesn't seem that bad in the cart at Tube Depot 😂
Click to expand...
whilst long plates will tend to have a mildly 'better bass' response, they are also more susceptible to noise / microphonics than short plates.
but that doesn't mean that all long plate tubes will be terrible or noisy.

i would think that low noise is more important than 'better bass' for this application.

tubes can be a bit of a gamble though, sometimes you'll get a real nice low-noise piece, and then other times you'll get an otherwise identical tube that, for whatever reason, is noisier and picks up heater hum worse than others.
 
LukeFRC said:
Well this was exciting to find last night - and currently costing it up (in U.K.) and weighing up so I need this?!
Click to expand...
*if I need this


it's interesting to see, and follows some of my bass tone geekery - but how much of the "tone" do you think is from the tube circuit and how much is from the transformer? like, ignoring the eq - how different is it sound wise from a Sushibox finally for example?
 
LukeFRC said:
*if I need this


it's interesting to see, and follows some of my bass tone geekery - but how much of the "tone" do you think is from the tube circuit and how much is from the transformer? like, ignoring the eq - how different is it sound wise from a Sushibox finally for example?
Click to expand...
The circuit of the D.I. portion actually isn't wildly different from a Finally. If you're using the XLR output of the Noble then you're actually only using one of the tubes anyway, the second tube is only used in the 1/4" circuit.

Soundwise it really comes down to voicing and tube choice, I use 12AX7 in Finally, Noble uses 12AU7. But if you scrapped his EQ and put a gain control in its place, Noble's XLR section is pretty dang close to Finally.
 
vigilante398 said:
Noble uses 12AU7
Click to expand...
omg how did i miss this. good to know - just assumed it was x2 12AX7.

what's the current limit of the HV supply?
just curious cos 12AU7 draws almost 10 times idle plate current of 12AX7 (10.5ma vs 1.2ma @ 250V)

vigilante398 said:
if you scrapped his EQ and put a gain control in its place, Noble's XLR section is pretty dang close to Finally.
Click to expand...
getting real keen to see the schematic - i'd really like to explore the possibility of doing a mod to lift the treble and bass controls for a 'flat response' option...
 
Do yall have any tube recommendations? From just reading various forum posts, telefunken smooth plates seem to be the magic tube I want but I cant afford a $100+ tube.

Ill most likely get a pair of JJs directly from Noble. There's really no upcharge for whatever testing he does. What are some other good tubes in the $20-$30 range and how does their sound signature differ from the JJs?

Ill put something fancy in the first stage if I ever have some money to burn
 
How much of the DI circuit is on the main board? Could I take the DI daughterboard and use it to add xlr and ground lift to another pedal?
 
So how are y'all pronouncing this Nobelium thing?

(following bold-caps for EMphasis, emPHAsis, emphaSIS...)

No BELL eeum

No beh LEEyum , No BEHL yum

NOB el ee um

No BELLY um

Naw bullEE uhm

...
 
astoria said:
How much of the DI circuit is on the main board? Could I take the DI daughterboard and use it to add xlr and ground lift to another pedal?
Click to expand...
The DI daughterboard is basically a standalone passive D.I., there are pads on it for the unbalanced input and ground, then the D.I. transformer, ground lift with associated passives, and the XLR jack are all on the daughter board. You could add one of those to another pedal as a D.I. output, or you could stick it in a small box by itself with a 1/4" input jack (not sure if it would fit in a 1590A, would be close) and have a very nice passive D.I. box.

Feral Feline said:
So how are y'all pronouncing this Nobelium thing?

(following bold-caps for EMphasis, emPHAsis, emphaSIS...)

No BELL eeum

No beh LEEyum , No BEHL yum

NOB el ee um

No BELLY um

Naw bullEE uhm

...
Click to expand...
/noʊˈbiːliəm/ (noh-BEE-lee-əm)
 
owlexifry said:
omg how did i miss this. good to know - just assumed it was x2 12AX7.

what's the current limit of the HV supply?
just curious cos 12AU7 draws almost 10 times idle plate current of 12AX7 (10.5ma vs 1.2ma @ 250V)


getting real keen to see the schematic - i'd really like to explore the possibility of doing a mod to lift the treble and bass controls for a 'flat response' option...
Click to expand...
Just realized I missed this question, sorry about that. People on the interwebs are divided on the max current of the NE555-based SMPS, I've seen numbers as high as 40mA, but I don't think it's that high. The most I've ever pulled from one (on purpose) was around 20mA, so I'm not sure what the max is. But fortunately we're not running the 12AU7 anywhere near their max, so they're not pulling the full current that they're capable of as an amplifier.
 
vigilante398 said:
The circuit of the D.I. portion actually isn't wildly different from a Finally. If you're using the XLR output of the Noble then you're actually only using one of the tubes anyway, the second tube is only used in the 1/4" circuit.

Soundwise it really comes down to voicing and tube choice, I use 12AX7 in Finally, Noble uses 12AU7. But if you scrapped his EQ and put a gain control in its place, Noble's XLR section is pretty dang close to Finally.
Click to expand...
Cheers - that’s really interesting

Feral Feline said:
So how are y'all pronouncing this Nobelium thing?

(following bold-caps for EMphasis, emPHAsis, emphaSIS...)

No BELL eeum

No beh LEEyum , No BEHL yum

NOB el ee um

No BELLY um

Naw bullEE uhm

...
Click to expand...
Just like the element on the periodic table
 
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