# B1 with Korg Triode

#### Nelson Pass

Paid Member
What is the maximum output impedance you can accept and how much gain do you want to lose?

#### sinski

Papa Nelson,
I don'tknow what is the maximum output impedance I can accept. I am using different power amps with input impedance from 10k to 22k. (Heed Canopus 10K, Heed Obelisk 22K). I am thinking about building two ACA (bridged monos).
How much gain i want to lose ? If -3dB will be not enough, than -6dB.

1 user

#### sinski

I checked it and I need at least -6dB gain reduction.

#### Nelson Pass

Paid Member
The output of the B1 will drive 10k, so you could use a divider consisting of 2 resistors at about 5k or so. This would give a 10k load for the preamp, 6 dB attenuation, and a 2.5k source impedance for whatever follows.

1 user

Like this ?

#### Nelson Pass

Paid Member
Glad you asked - No, the 4.7K to ground is after the 4.7k at the output.

Like this ?

#### Zen Mod

Paid Member
yeah, like that

just use Kiloohms, instead of Ohms

#### sinski

Papa Nelson and Zen Mod thank you so much for your help
Yes, of course Kiloohms, not Ohms
One more question - I was reading a lot about B1K and 0,22uF at the input seems to be enough (I had one left from some speaker project).
Is it really enough, or should i better take 1uF or more ?

#### Zen Mod

Paid Member
if you read it's enough, that's it

whoever wrote that, probably gave calculus to confirm what's corner frequency

#### sinski

It was around #2610 by ClaudeG, he calculated it, I assume it was correct.

#### Surf21

Success!

Sounds great and loving how it plays with my setup. Thank you for the @Ben Mah for the help identifying my issue with the JFET. Also, thank you @ClaudeG for the details on your build. This was my first and won't be my last. I'm organizing leftover parts to put another one together for a second system. Fun Stuff!

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3 users

#### drjlo

Success!

Sounds great and loving how it plays with my setup. Thank you for the @Ben Mah for the help identifying my issue with the JFET. Also, thank you @ClaudeG for the details on your build. This was my first and won't be my last. I'm organizing leftover parts to put another one together for a second system. Fun Stuff!
Is there a reason you placed different sized caps at the locations they are at or just randomly picked one of three "10uF" marked sites?

#### Surf21

@drjlo Check out post #2,606, I followed the build tips of folks that are smarter than I am and who have shared their knowledge here. I started with the standard build and then switched it up with mods to the "10uf". Sounds lovely.

1 user

#### kosva

Hi
I am sending a few pics of my new NUTUBE B1. It is build on a PCB which was desighned by COREL DRAW.
Excellent sound, full of music, with very pleasand listening and much better than the DC B1 or my Grounded Grid tube preamplifiers. The power amps are two DIY Pass Aleph 30 monoblocks.
I placed the PCB on the mother board of my old AlephL and DCB1 enclosure and is powered by two (in series) 12v acid lead batteries .
I have a lot of 2SK389 on my shelf so as I made the pcbs for them and I also use MUNDORF 4.7 uF capacitors and WIMA MKP 2.2 uF parallel with
ELNA Silmic 10uF.
The T7,8 voltages was finally adjusted at 9.5V. After playing for more than 100 hours the voltages are remaining at 9.55-9.57 V .
Because of the 2SK389 I didn't use the R1 resistors.
I want to thank Nelson again for sharing his designs with the DIYAUDIO community all these years.

Kostas A. Vazakas
Egio, Greece

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5 users

#### Dneu2011

I’m currently trying to finish another one of these preamps, but no sound on the right channel.

All voltages check out and I confirmed all voltages on the good channel vs bad channel match.

I bypassed the input selector and pot and confirmed it’s not either of those

i bypassed the board on that channel and determined my output rcas are wired fine.

I reflowed all solder on that side.

I’m now thinking the tube could be faulty. Is there a way to check continuity?

#### ghitus

Check the filament integrity...

#### Dneu2011

Is there a way to do this with multimeter?

#### Ixnay

If I understand correctly, yes, you would use the ohms setting of the meter and check for not just continuity but also to see if there is a reading that is higher than the filament resistance. Spec sheet may specify the correct resistance.