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B1 with Korg Triode
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Old 7th May 2019, 05:42 PM   #2291
Nelson Pass is offline Nelson Pass  United States
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B1 with Korg Triode
Quote:
Originally Posted by Enochrome View Post
I was not sure where to post this question,
but I have a Millet NuTube buffer board and when completed and hooked
up to a 12v 5ah battery I get a loud buzzing sound. Could this be a ground
issue?
Possibly related - I recall that Pete Millet has posted that there have been
instances of oscillation in the bipolar followers, and so recommends a
base stopper resistor. I don't recall the value, but 1K would be safe.

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Old 8th May 2019, 05:31 AM   #2292
cubicincher is offline cubicincher  Germany
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Default to andreasw #2287

Beautiful work!


Greets
Dirk
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Old 8th May 2019, 06:20 AM   #2293
avdesignguru is offline avdesignguru  United States
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Enochrome:
I have built both the Nutube Buffer and the Nuhybrid headphone amp with the recommended 1K base stopper resistors and have had no problems. Both of mine are using a 24v supply, not 12v.

I've attached a photo of how I stuck one leg of the input cap (changed to a 10 ufd electrolytic) into the + input pad, air wired the input to the free leg and commandeered the input cap pads to insert the 1K resistor mounted vertically.

I also replaced Pete's recommended 475K plate resistors with Papa's recommended 332K resistors and used Papa's recommended 9.5V plate voltage settings. I think that both devices sound much better for the changes. For the headphone amp, I also changed the power supply input buffer voltage divider resistors from Pete's 475K to Papa's B1 Korg circuit values of 332K, although I'm not sure that matters.

In comparing the Nutube Buffer (Mosfet inputs) to the Headphone Amp (Bipolar inputs) to the Korg B1 (Jfet inputs) the Nutube pretty much dominates to the sound. Once everything gets 332K plate resistors and a similar 2nd harmonic level, they all sound pretty close to each other. Papa's B1 Korg does win the shootout for being quieter and smoother sounding while perhaps a bit more open at the same time. Probably a combination of better power supply and the Jfet buffers.

All of these circuits invert the input polarity, which happens at the Nutube. Some listening to the headphone amp with the inputs reversed by some isolation transformers has convinced me that proper phase at the transducers is critical. Easy to do with loudspeakers but the headphones required the transformers due to their common ground connection.

My next step is to A-B the $6 Triad TY-250P input transformer against some $75 Jensen JT-11-P-1 transformers. No doubt the Jensens will win but I am curious to see how close the Triads get.
Attached Images
File Type: jpg Nutube Buffer.jpg (213.6 KB, 499 views)
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Old 8th May 2019, 08:36 AM   #2294
ClaudeG is offline ClaudeG
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Please post your findings regarding the Triad here, that could be an interesting solution indeed for headphones :-)

Claude
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Old 8th May 2019, 08:53 AM   #2295
dvb projekt is offline dvb projekt  Germany
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B1 with Korg Triode
Quote:
Originally Posted by andreasw View Post
Hello,

here is my finished Korg
Click the image to open in full size.

I got the PCB of a friend. It has a separate PCB for the Nutube, a lot of space for Caps (I took small Black Gates ), two PSU connectors (wall wart or S11) and the option for a Mute switch (I don´t need it).

Click the image to open in full size.

The S11 PSU has two output voltages. A 24V and a 9V which supplies directly the Nutube.

I took a 50K TKD volume pot which works very fine.

Click the image to open in full size.

I dont´t like screws in the bottom so I always install a second bottom plate for fixing the PCB and other screws etc. .
This second plate is mounted with the feets

Click the image to open in full size.

Thank you Mr.Pass for this very well sounding Pre-Amp!!!

Kind regards
Andreas
Wow! Sehr schick Andreas...
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Old 8th May 2019, 02:18 PM   #2296
Marra is offline Marra  United Kingdom
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B1 with Korg Triode
I have some 2SK170's with idss of 6.8ma and 7.7ma. are these suitable to use?
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Old 8th May 2019, 02:39 PM   #2297
Zen Mod is offline Zen Mod  Serbia
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B1 with Korg Triode
yup
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Old 8th May 2019, 02:50 PM   #2298
avtech23 is offline avtech23  Australia
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B1 with Korg Triode
Quote:
Originally Posted by ClaudeG View Post
Please post your findings regarding the Triad here, that could be an interesting solution indeed for headphones :-)

Claude
+1 definitely interested to hear your results.

Can anybody point me in the right direction as to what I should look for when selecting an audio transformer to couple with 32ohm headphones?
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Old 8th May 2019, 03:44 PM   #2299
Marra is offline Marra  United Kingdom
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Quote:
Originally Posted by Zen Mod View Post
yup
Thanks Zen. I can use with just a jumper soldered in place; no resistor needed?

Last edited by Marra; 8th May 2019 at 03:48 PM.
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Old 8th May 2019, 03:57 PM   #2300
Zen Mod is offline Zen Mod  Serbia
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B1 with Korg Triode
clarify - what jumper , what resistor?
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