The Ampeg circuit is two channels with one tube each. I have no intention of doing a two-channel B-15 preamp.
EF86 is a single pentode stage, not a dual triode, so it wouldn't be a direct replacement in the circuit. 6SL7 could be made to work.
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The Sushi Box FX Secret Society
- Thread starter kranahan
- Start date
- Feb 16, 2008
- 21,240
- 23,636
- Disclosures
- John K Custom Basses
i gotta say that the nobelium sounds REALLY GOOD (it sounds HUGE)! IMO, it's a great design. it's basically flat with the bass & treble fully counterclockwise, but you can engage the low cut switch and roll up the bass control to make it sound pretty flat too. it draws almost 500ma fully warmed up. it's also very quiet as far as noise goes. i haven't tried the xlr out yet, but i will soon. mine has the lightning boy transformer.
I really liked the one I built but it was redundant for me so I sold it. I AM available to build one for someone interested but without the skills. PM me, we can chat about cost if you want…
Also, Nathan was a huge help to me with my build in private, not public, so cheers for behind the scenes hand holding, thanks!
I've already committed to a limited run of built-by-me Bassdudes, I'm considering a run of Nobeliums as well. I have a redesigned D.I. board that will handle an Unagi transformer, which I think would be cool in a Nobelium.
Gotta start supporting payment plans
Damn you.
They won't be pink though, yours will still be one of a kind.
So I have and really enjoy my Finally V2. I’ve been using the Regal model on the HX One as a preamp into the Finally and it is great. My question is, do you think having a Nobellium and a Finally would be overkill since it has a DI and similar type HPF or would they go well together?
A considerable amount. Bassdude is based on the tweed Bassman, which runs a pair of 12AX7 for a delightfully rich, warm sound with a nice bite and a fair amount of gain on tap. Nobelium is based on the Noble, which uses a pair of 12AU7 for a completely clean, no dirt, largely transparent preamp.
I mean I would generally consider having two DIs on the same board overkill, but I guess if you're using one as a preamp for flavor and the other as a DI that also happens to have some flavor, I could see it making some sense if you're using them together with a modeler.
You say that with the conviction of a man who already has it in his shopping cart...
I would like to preemptively claim one of these aforementioned bassdudes whenever they should appear.
my b15 has one preamp tube per channel and an inverter tube. the two preamps can also be linked in parallel, before the inverter.
a thought here could be that you squish a "6sl7 MORE" circuit in there too, to make it MORE your own. ;-)
I have a space for a grand slampegg on top of something like a Straight Ahead amp with 1000w (homemade). its all I need for most gigs, especially upright gigs, and replaces a WWUltra and an Acoustic Image, but lacks the variable HPF which is often needed for upright gigs.
using 2 EA Wisy110s - one on each side of the drummer or stage, whichever is more desirable.
I modded my Slampegg to be switchable between 1 and 10Mohm, though some DB guys seem to like 5.7
FWIW
full,full
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whilst in the studio now, I'm using the finally (with an old RCA 12au7/ECC82) and a thought occurred to me: the HPF for other devices could be not sweepable, but switchable between 60, 90, and 120hz (not sure when you'd need 120 but perhaps one needs this) @6db/oct as before.
sometimes 90 is too much or too high.
I think you mentioned you were working on a sweepable HPF, so thats where this idea is coming from.
if it is sweepable it could be even steeper, perhaps even 18-24db/oct.
as always, happy customer here, with some ideas for the thinktank.
sometimes 90 is too much or too high.
I think you mentioned you were working on a sweepable HPF, so thats where this idea is coming from.
if it is sweepable it could be even steeper, perhaps even 18-24db/oct.
as always, happy customer here, with some ideas for the thinktank.
So I was watching this Dr. Z video, which makes me have a question (maybe relevant to this thread, maybe not, a mod can move it if it's too tangential):
Is there some literature about why you'd choose one preamp tube over another? It feels like the answer should be obvious (this one sounds good in this circuit), but most preamp tubes these days seem to be 12AX7s or from that same family. What's the motivation to use a single 6SL7? Or, like in the Noble and MORE, 2 x 12A_7s ? I feel like this answer should be obvious to me, but this also makes me wonder why a company like Ampeg would go from using the 6SL7 in the B15 to using 12AX7s in the PF20T/PF50T. Part of the reason I'm asking here is because there are people who design tube circuits in here, so for those people, what is the motivation for one tube over another?
Is there some literature about why you'd choose one preamp tube over another? It feels like the answer should be obvious (this one sounds good in this circuit), but most preamp tubes these days seem to be 12AX7s or from that same family. What's the motivation to use a single 6SL7? Or, like in the Noble and MORE, 2 x 12A_7s ? I feel like this answer should be obvious to me, but this also makes me wonder why a company like Ampeg would go from using the 6SL7 in the B15 to using 12AX7s in the PF20T/PF50T. Part of the reason I'm asking here is because there are people who design tube circuits in here, so for those people, what is the motivation for one tube over another?
D
I think there is one in the classifieds right now, built by JohnK. No affiliation.
Step one is always the amount of gain. Every tube has an "amplification factor" (abbreviated mu or µ) based on how much that tube can amplify. In common audio tubes they range from 20 (12AU7) to 100 (12AX7). There are plenty in between like 60 (12AT7) and 70 (6SL7, 5751).
Step two is trickier, and it has to deal with tonal characteristics. There are electrical characteristics like plate resistance and transconductance that affect this, but these are seldom talked about in audio because it's easier to say "___ tube sounds like ___".
If you compare two tubes with identical amplification factors like 6SL7 to 5751, there are differences in plate resistance and transconductance that result in different tonal characteristics that are sometimes difficult to describe, but the general consensus is that 6SL7 sound "warmer" or "bigger", and that's part of what gives the original "B-15N sound". I could build a B-15N preamp with a 5751 and it would be very similar, but it wouldn't sound 100% the same.
A lot of comparing one tube to another gets into subjectiveness so I try not to dive too far into it, but there are measurable factors that can affect the characteristics of how a tube will sound, and as an engineer, measurable characteristics are the best characteristics.
I think that JohnK unit is solid state, but I think he has built tube versions.
- Feb 16, 2008
- 21,240
- 23,636
- Disclosures
- John K Custom Basses
yep, that one uses jfets-no tubes, although i did sell a Bass Dude that i made on reverb.
