Nobelium - tube bass preamp project

[vigilante398]

My first build had a "Lightning Boy" transformer in it, all pedals since have had the Unagi E4305 transformers in them, I think I have 3 spare Unagi transformers in the parts draw for future builds or maybe to fit into an amp I build.
I prefer the the tone of the Unagi.

I obviously profit when people buy Unagi, but I have no issue recommending the Lightning Boy MC15, Mike (the owner/builder) does excellent work and is great to deal with.

 

[riverp]

My first build had a "Lightning Boy" transformer in it, all pedals since have had the Unagi E4305 transformers in them, I think I have 3 spare Unagi transformers in the parts draw for future builds or maybe to fit into an amp I build.
I prefer the the tone of the Unagi.

Same here. Both the Lightning Boy (also in in my original Nobelium) and the Unagi trafos used since the first Nobelium are great.

Sad to hear that Cinemag as a company was such crap to deal with. Too bad, I got Unagi.

 

[XjFred]

To make the HPF switch have 2 values you have to replace the ON-ON switch with an ON-OFF-ON 3 position switch, remove a small copper trace on the switch side of the PCB that connects terminal 2 to terminal 3 of the switch and then put another capacitor from terminal 1 to terminal 3 of the switch. BE VERY CAREFUL cutting into the PCB when removing the track between terminal 2 and 3 on the switch, use a very sharp knife and score it next to the pads and gently lift it out, remember the PCB is most like multilayer and we do not want to cut into any internal copper layers.
SamuelG might know the best value for the extra capacitor, I just add another 4n7 capacitor when I do it.
In one of the pictures it says please remove track between switch legs 1-2, it should say 2-3. I think the pictures explains it easy enough.

The original circuit has C8 always in the circuit and when you turn the HPF off you simply short C8 out with the switch and the signal goes straight past the capacitor.
When you turn the HPF on the switch opens and the signal goes through C8, all the mod does is add another capacitor (C8a) in parallel with C8 to increase the capacitance and thus lowering the HPF frequency.
In the switch left position C8 is shorted out, in the middle position the signal goes through C8 and in the right position the signal will go through C8 and the extra capacitor (C8a)
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Thank you very much ! Now I have to figure out if I can unsolder the SPDT.. or build another Nobelium.

 

[SamuelG]

Thank you very much ! Now I have to figure out if I can unsolder the SPDT.. or build another Nobelium.

I haven’t even tried to remove those switches but a reflow gun and a good board mount would be my strategy after removing as much solder with copper braid.
In my builds I use a black On-Off-On switch to easily identify my 3-stage HPF builds. These are available at Tayda.

 

[LukeFRC]

That's one of the main reasons I started buying the Unagi transformers, everyone else worth having was either difficult to deal with, prohibitively expensive, or both. I was able to get a couple Jensens when I first started doing D.I. builds, but it quickly started feeling like they didn't think I was worth their time. I tried Cinemag after that, but they took my money and ghosted me, it took a paypal dispute to get them to respond to my emails.

I was wondering what the story behind Unagi was - it was like overnight they appeared on sushi box stuff - I thought you had taken up a sideline in transformer winding, alongside the sushi, c2c and everything, oh and the day job!

 

[vigilante398]

I was wondering what the story behind Unagi was - it was like overnight they appeared on sushi box stuff - I thought you had taken up a sideline in transformer winding, alongside the sushi, c2c and everything, oh and the day job!

Yeah it took some effort but Unagi were custom wound to my spec by a Chinese company. So I designed them, but I don't build them. Part of their team (it's a large company) are actually traveling to Chicago next week, we're going to hang out.

So cost was a big factor, but also getting exactly the spec (impedance, frequency response, etc) that I wanted was another. Also availability is important, I need to be able to say "Hey can you send me 800 of these ASAP?" and have someone that says "we gotchu fam". They build them and ship them to me, I (or my kids, they like that job) slap labels on them.