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B1 with Korg Triode
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Old 16th November 2019, 10:00 AM   #3671
ClaudeG is offline ClaudeG
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Join Date: Jan 2015
Hi Rich,

Great, please let us know your findings... is there anything you can arrange regarding the cap in the signal path that is in the middle, shouldn't be too difficult to address that one aswell?

Regarding my findings posted back then, replacing only the 1st and 2nd cap in the signal path (at that stage, before going PPP for all 3 x 2 = 6 of them) while the TOCOS was already in:

And here are the result :
- The PPP caps didn’t alter the sound in terms of sonic balance, caracter, frequencies… it is all nearly the same, but even better !
- The PPP caps definitely added even more kick and extended bottom frequencies, the extra kick not being a problem as all remained balanced and in fact more differentiated between bass notes
- the PPP caps outlined another dimension in terms of precision, grain / resolution, both opening a curtain in transparency while also taking a slight veil out
- All frequencies seem better balanced, no more of the slight mid-bass exageration
- It all sounds very pure but also flows much better, intergration of music is better, making a very enjoyable whole – so addictive I must say that carrying listening tests is difficult, you get carried away !
- Frequency range seems a bit extended, deepest bass being now clearly as well representated than the other frequencies, both energic and subtle, I also believe that the highest treble is a bit better
- Noise floor seems lower, lowest sounds more natural, easier to follow and better integrated

So it might indeed be your hypothesis could be right re Tocos + PPP caps combo, but then I don't want to bias you before you carry your independant listening tests.

Just for note, I adjusted my favourite voltage also indeed after all the mods I did

Good luck tweaking further an already excellent unit

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Old 16th November 2019, 11:09 AM   #3672
nicoch58 is offline nicoch58  Europe
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Originally Posted by rhing View Post
Just received a 50k Tocos Cosmos volume pot from the eBay seller ClaudeG referenced. I am also going to switch to Polypropylene film caps for the inputs. For the output caps, I might bypass the stock 10uF Nichicon FW right.
the bipolar nichicon ,the green ones , are quite good
Humble Homemade Hifi - Cap Test
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Old 16th November 2019, 11:22 AM   #3673
rhing is offline rhing  United States
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Thanks for the suggestions. I left my B1 Korg NuTube with a buddy in California after attending the recent Burning Amp Festival. My friend is just blown away with how this preamp sounds in his system. I think ClaudeG’s tweaks will extract extra performance from the preamp. Can’t wait to get it back to install all the caps and volume pot. The 1U chassis will force me to be a little more creative in fitting the 1uF caps.
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Old 20th November 2019, 12:43 AM   #3674
irishpatrick33 is offline irishpatrick33  United States
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Originally Posted by avtech23 View Post
I would pop in a couple of resistors at the front end of the circuit in a voltage divider (or a 50k pot if you have it)
After months of waiting for powder coating (long story), I am ready to complete my amplifier. It's been a while since I last touched it. I am looking for some advice on setting up the voltage divider portion (mine is a hybrid amplifier with no volume control).

For testing, I hooked up a 50K pot (backwards) and determined the maximum volume occurs at the 35K/15K split. I bought some 15K and 34K resistors. Logically I would assume the 15K is R1 and 34K is R2. Is that correct? Also does it matter where I ground R2?
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Old 20th November 2019, 12:56 AM   #3675
irishpatrick33 is offline irishpatrick33  United States
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Originally Posted by Nelson Pass View Post
If you put a volume pot after the Korg, you do have some control over the amount
of distortion, that is to say you can increase it, as it goes up with level before the
pot. If you put gain after the Korg, or use an amplifier with more gain, you will
decrease the distortion.
Could you please provide some more info on this option?

I am making a hybrid amplifier, that includes Nutube B1. There will be no volume control, so I will employ a voltage divider. The amplifier portion has 20+ dB of gain. Cosmetically speaking, I think having the divider directly between preamp and amp portions would be elegant design. Are you saying there is a sonic benefit to this variation?

Thank you

Last edited by irishpatrick33; 20th November 2019 at 01:06 AM.
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Old 20th November 2019, 03:35 AM   #3676
brian92fs is offline brian92fs  United States
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B1 with Korg Triode
The B1K article indicates that he designed the distortion profile around a 1V output. Distortion increases with output voltage. So in theory running 1V through it and placing the volume control downstream adds more control and meets the ideal design criteria. However, real music is dynamic so it’s unclear how much benefit it would actually provide.
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Old 20th November 2019, 05:56 AM   #3677
ClaudeG is offline ClaudeG
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Hi Irishpatrick,

Yes, R1 and R2 are as you stated.

R2 goes to signal ground, idealy the one at the input.

I hope this helps

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Old 20th November 2019, 08:14 PM   #3678
Rewind is offline Rewind  Sweden
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B1 with Korg Triode
Here is my attempt. Was pretty easy to dial in the 9.5 V om T7 and T8 (after flushing all the solder points). I used velcro to dampen the piece of plexy glass it is glued to, behind the front front plexy glass. I can still hear some microphonics, but only when smashing two pieces of wooden toys together, which happens surprisingly frequently in my home.
Sound is warm and open, but the tube saturation is more towards a fuzz guitar pedal than a tube preamp. I use it with an F5 amplifier, and it has never sounded better. I used a B1 preamp before, which now is used with an integrated Sun Audio 2A3 replica amp. This gave me the opportunity to try the Sun Audio amp on max volume with B1 as a volume control, and it became overwhelmingly FAT! Had to tone it down a little. I use the B1 + tube amp on 15" JBL woofers, and the B1 Triode + F5 on my mid and high horns. All I can say it is that it is better than before, but I wonder if I should use a real tube preamp with the F5. I thought the Sun Audio replica amp is too imprecise for mid-range, here the F5 is more accurate, but the F5 was always it bit hard sounding, but not any more thanks the B1 Triode. I may add some decorative flourescent volt meters for T7 and T8 in the future, with an off switch, just to fill that empty hole in the middle of the chassis.
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File Type: jpg IMG_20191109_202459__01.jpg (290.3 KB, 206 views)
File Type: jpg IMG_20191109_202519__01.jpg (610.0 KB, 204 views)
File Type: jpg IMG_20191109_101105~2.jpg (468.5 KB, 202 views)

Last edited by Rewind; 20th November 2019 at 08:19 PM.
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Old 20th November 2019, 08:54 PM   #3679
cubicincher is offline cubicincher  Germany
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Hello rewind,

nice work!

Now you can play going up and down around the 9.5V,

Invert your loudspeaker polarity - interesting results....
Can sound better or worse,

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Old 20th November 2019, 09:06 PM   #3680
gigigirl is offline gigigirl
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Hi rhing, the easiest way to firm up & deepen the bass output is to put magnets behind the Korg Nu tube. It also help to stop the microphic nature of the unit.

Cheers Derek
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