Nobelium - tube bass preamp project

[Tassieviking]

Try this calculator :http://sim.okawa-denshi.jp/en/CRhikeisan.htm
It's a great place for calculators but it can get a bit techy.
The Nobelium does have a 6dB/octave HPF, my mind is playing tricks on me again.(Fixed above post)
I thought that the frequency should be at the -3dB mark when specified, but I can be wrong (again)

https://www.electronics-tutorials.ws/filter/filter_3.html

What I am sure about is that my mod will work and give you 2 different HPF settings.
Switch to left = shorted C8 so it is bypassed and no HPF
Switch in middle = signal through C8 so normal HPF
Switch to right = signal through C8 and C8A in parallel so lower HPF frequency
Capacitors in parallel is just adding the 2 values together for total capacitance
I usually use this frequency calculator :http://www.learningaboutelectronics.com/Articles/High-pass-filter-calculator.php
I used to not need any calculators when I was younger, I even went to uni for EE but being an electrician paid me so much more so I kept working as a tradie most of my working career.

 

[JimD_190]

What are other folks seeing for the plate voltages in Nobelium. With a B+ of about 240 vdc, I'm seeing about 61 vdc on the plates of V1 and V2. I'm used to seeing higher plate voltages in Fender style circuits, just wondering if this is part of the design of the Noble/Nobelium, or if I've got an issue.

 

[Valiesh]

What are other folks seeing for the plate voltages in Nobelium. With a B+ of about 240 vdc, I'm seeing about 61 vdc on the plates of V1 and V2. I'm used to seeing higher plate voltages in Fender style circuits, just wondering if this is part of the design of the Noble/Nobelium, or if I've got an issue.

With a B+ of 252.6 VDC I have 69.5 VDC for V1 and 197.1 VDC on V2 (plate voltage measured at pin 1).

Have you already double-checked the value of R11 (V2 plate resistor)?
Is it 18K?

 

[JimD_190]

Thanks... you're right, I was measuring V1A and V1B plates at R9 and R10. V2 is about 190 and R11 is correct 18K, so no issue.

 

[matmonster58]

I'm going to stick in a 10uF in for C8 and see what happens. It was the next biggest value that Tayda had wima caps for.

I know I want the HPF to be lower (based on my experience with the HX stomp emulation) but I don't have a specific target frequency in mind. Ill try to take measurements of all the eq curves after I get mine built.

I'm setting my deadline as the end of the month, hopefully...

 

[Tassieviking]

I'm going to stick in a 10uF in for C8 and see what happens. It was the next biggest value that Tayda had wima caps for.

I presume you mean 10nF and not 10uF, I get 72Hz with that value.
Here are the frequencies I worked out for my mod in post 239, best to do your own calculations in case I am wrong though.
C8 value in yellow column and the frequency is next to it.
I am really interested in what you find out.

 

[matmonster58]

I'm finally making some progress. These Vishay resistors are significantly larger than typical resistors. It makes for a tight squeeze in some spots

Im still waiting for an order from taydas and I may need to place another mouser order to get some parts I missed but I'm exited to get this done

 

[Mentaltossflycoon]

View attachment 72491
I'm finally making some progress. These Vishay resistors are significantly larger than typical resistors. It makes for a tight squeeze in some spots

Im still waiting for an order from taydas and I may need to place another mouser order to get some parts I missed but I'm exited to get this done

 

[100WChris]

Hi,
my name is Chris, im a bass player from Germany and ordered a Nobelium Kit from Musikding today! juhu
Musikding is selling the kit with an BB enclosure. Does anybody have a drill template for BB? I only found one for 1590XX…
Or is BB the wrong size?
Perfect would be a dxf as I planning to mill the enclosure on my cnc.
sorry for my bad English …(
best regards
Chris

 

[vigilante398]

Hi,
my name is Chris, im a bass player from Germany and ordered a Nobelium Kit from Musikding today! juhu
Musikding is selling the kit with an BB enclosure. Does anybody have a drill template for BB? I only found one for 1590XX…
Or is BB the wrong size?
Perfect would be a dxf as I planning to mill the enclosure on my cnc.
sorry for my bad English …(
best regards
Chris

Whoa, BB is definitely the wrong size. These should be in a 1590XX.

 

[Tassieviking]

Here is the drill template from Tayda, all dimensions are from the middle of each side.