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B1 with Korg Triode
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Old 13th March 2019, 11:41 PM   #1781
ClaudeG is offline ClaudeG
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LOL, thanks Zen Mod, no doubt Papa knows what he does... and more :-)
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Old 14th March 2019, 05:26 PM   #1782
cjfrbw is offline cjfrbw  United States
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I tried Pass Korg build with First Watt M2 for several hours: digital source to Pass Korg to First Watt M2 to 4 ohm crossover-less panel speaker.

In switching the polarity of the speakers back and forth, I preferred the H2 negative slightly (speaker polarity reversed) with M2.

I think Pass Korg and First Watt M2 are an excellent combination. I am a little miffed because I think the Pass Korg build does better than my beloved tube rectified DHT gain stages in this regard.

I let the First Watt M2 warm up for several hours. I would say the sound is pushed about 30 to 50 percent toward a VFET type sound, without sacrificing the organic whole-ism and energy that are M2 predilection. The combination of Pass Korg and M2 produced outstanding separation while retaining body, tone and timbre. Imaging is huge and deep.

It is very strange to me that two components i.e. M2 and Pass Korg, both with higher distortion profiles, no feedback, etc. rather than ‘the point 0000 etc.’ distortion type components, can nonetheless sound surpassingly transparent through speakers when played together. So I guess the psycho-acoustic mysteries of the distortion profiles prevail.
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Old 15th March 2019, 04:43 AM   #1783
wineds is offline wineds  Australia
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My Nutube is up and running on the bench.
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Old 15th March 2019, 10:28 AM   #1784
ClaudeG is offline ClaudeG
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Thanks to all the kind contributors here I digged into the schematic and a lot of unknown concepts to me (cathode bypass, collector decoupling)... and learned a lot -no wonder starting from scratch :-). Many thanks, that's entertaining!

I undertsand now why some caps that don't seem to be in the critical sonic path are in fact... and that the choices of course wisely advised by Papa are best followed and left alone! Clever cooking of course...

I have though one last question, if you guys don't mind.
To my knowledge no one yet mentioned if this pre could drive a high impedance headphone. Of course, given the high pre-output impedance I was only thinking of a (highish) nearly constant 600 Ohm impedance headphone. Of course, if that's the case, the last output cap would probably need to be upgraded from 10uF to say 22uF or whatever to avoid low frequency cutting (as said I did my homework)

I am not looking for a quality phone amp, more "an OK monitoring simple add-on solution", in parallel to the "regular outputs driving the power amp" (say with some 100R line decoupling to avoid interferences between these, and both would anyway never be used at the same time)

Silly idea or feasible? Headphone is Beyerdynamics DT990 from several decades, I am not listening loud... felt worth asking, sorry if stupid thought

Many thanks again

Claude
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Old 15th March 2019, 10:30 AM   #1785
Zen Mod is offline Zen Mod  Serbia
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B1 with Korg Triode
of course that you can try , even use it if you like it

nothing's gonna burn in flames , no worries
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Old 15th March 2019, 11:07 AM   #1786
ClaudeG is offline ClaudeG
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Many thanks once again Zen Mod!

Enjoy your WE very much

Claude
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Old 15th March 2019, 12:32 PM   #1787
R-K Rønningstad is offline R-K Rønningstad  Norway
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Quote:
Originally Posted by ClaudeG View Post
Thanks to all the kind contributors here I digged into the schematic and a lot of unknown concepts to me (cathode bypass, collector decoupling)... and learned a lot -no wonder starting from scratch :-). Many thanks, that's entertaining!

I undertsand now why some caps that don't seem to be in the critical sonic path are in fact... and that the choices of course wisely advised by Papa are best followed and left alone! Clever cooking of course...

I have though one last question, if you guys don't mind.
To my knowledge no one yet mentioned if this pre could drive a high impedance headphone. Of course, given the high pre-output impedance I was only thinking of a (highish) nearly constant 600 Ohm impedance headphone. Of course, if that's the case, the last output cap would probably need to be upgraded from 10uF to say 22uF or whatever to avoid low frequency cutting (as said I did my homework)

I am not looking for a quality phone amp, more "an OK monitoring simple add-on solution", in parallel to the "regular outputs driving the power amp" (say with some 100R line decoupling to avoid interferences between these, and both would anyway never be used at the same time)

Silly idea or feasible? Headphone is Beyerdynamics DT990 from several decades, I am not listening loud... felt worth asking, sorry if stupid thought

Many thanks again

Claude
There are lots of headphone PCBs on eBay and elsewhere. Based on simple headphone amp ICs or more “advanced” designs. You could pop in the simplest of those especially if you quality sound requirements are not stellar.
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Old 16th March 2019, 10:50 AM   #1788
manniraj is offline manniraj  India
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Join Date: Nov 2012
A quick question on the 475R resistor on the Christmas board that I have. Can I use a 470R 0.125W resistor instead of 475R? Does the difference of 5R makes an impact as 475R is not a regular resistor easily available locally and I had to order them either from RSDELIVERS or some other overseas site.

Thanks
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Old 16th March 2019, 11:37 AM   #1789
cubicincher is offline cubicincher  Germany
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Join Date: Mar 2016
Location: Hechingen, South of Germany
Default answer to manniraj #1788

Hello manniraj,


shouldn´t make a big difference. If you buy a 475 Ohm resistor with a tolerance
of 1% it will be anywhere inbetween 472 and 477 Ohm (approximately).
I think Nelson Pass mentioned that 0.6 W resistors should be used?

But perhaps our Professor Nelson can answer this? Or anybody of the experienced members here.

Greets
Dirk
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Old 16th March 2019, 12:30 PM   #1790
Dennis Hui is online now Dennis Hui  Canada
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B1 with Korg Triode
It looks like you need something with a higher wattage. Per Papa's document,
the 475 ohm resistor is across T4 and T5/T6. T4 should be at round 9.1V
and T5/T6 around 0.6V. The 8,5V drop works out to a bit over 0.15W.
So you'll definitely want something rated somewhat higher than that.
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