Thanks WKCox, looking at the picture the red/yellow ground wires from the volume to the Korg board are basically floating kind of grounds. As your input grounds are connected together but they are not grounded to the chassis and neither the output grounds as well. So does not seems to be the grounding rule as there is no return ground connection anywhere in your chassis as per the pictures. Can you please provide some inputs.
The reason I am asking is that your volume pot is not connected to the chassis for grounding.
Thanks again.
The reason I am asking is that your volume pot is not connected to the chassis for grounding.
Thanks again.
Hi Soundwave, I did see that. I was looking for the explanation that Nelson gave and the notation of the revision so I can read up on it. The link that WKCox provided is for the B1 Buffer without the Korg Nutube.
That's a bit harsh and not at all true.
6moons: audioreviews FirstWatt B1 with Nutube
The problems people have stem from the variations on the original design as reviewed above.
1 The original had two mono volume pots enabling any channel variations to be compensated for.
2 It came in a case with no ventilation holes reducing the chance of microphonics.
3 It was supplied with an external power supply. DIY audio kit supplied one is the wall wart type so most peoples pre amps will be a meter or more away from any problems that might be caused by that.
The Korg B1 is definitely worth building. It's simple yet produces a very enjoyable sound. Steve is right, there are many who have built and have been very happy like me. No regrets.
We thank Papa Nelson for generosity.
We thank Papa Nelson for generosity.
Microphonie is not a issue for me. It is just to bright sounding. More like a class D then Class A sound is my closest explanation.
My only audition to date, is one built with a off board PS, and much thought gone into the managing the microphonics.
As stated before my ears were off balance on the day, due to a chest / respiratory illness.
I heard it played through a Sansui AU111 and Stacked 57's.
I picked up on a Clarity/Lucidity not usually presented, and a expansion of the Soundastage, with a pronounced detail being perceived.
I do not at any time, feel the term 'bright' was a word to be put into the description.
The audition has left me wanting to audition it further, especially now my hearing is back on Par.
As stated before my ears were off balance on the day, due to a chest / respiratory illness.
I heard it played through a Sansui AU111 and Stacked 57's.
I picked up on a Clarity/Lucidity not usually presented, and a expansion of the Soundastage, with a pronounced detail being perceived.
I do not at any time, feel the term 'bright' was a word to be put into the description.
The audition has left me wanting to audition it further, especially now my hearing is back on Par.
Volume pot is grounded at the board. Star ground is the large trace at the back of the board where inputs, output and power are grounded, as well as a single ground wire to the chassis. The pot is grounded through a dedicated trace on the board -- single ground path so no potential for current flow resulting in hum.
Even though I have had problems with microphony, my B1 Korg built in stock form with the pioneer kit (except the hookup wire) sounds exceptional. I’ve used this preamp in my two systems and in two friends’ systems where everyone was very impressed with the midrange tone, soundstage depth and imaging. If anything, the sound is very smooth and musical. I cannot think of too many $300 tube preamps that sound this great. It certainly gives my more expensive Audio Research LS7 tube line stage preamp some competition.
That all said, the microphony was a problem until I mounted the PCB on vibration isolating standoffs used in drones, and closed up the chassis vent slots with vibration damping sheets. I have mentioned that the diyAudio store sell the B1 Korg with a chassis without vent slots and include the vibration damping standoffs.
I still have yet to install film caps on the signal inputs and outputs and a Tocos Cosmos volume pot. I am enjoying the preamp as-is so much, I just want to listen to music. I really have to credit Nelson Pass, Jason and Jim for putting together such an impressive kit.
That all said, the microphony was a problem until I mounted the PCB on vibration isolating standoffs used in drones, and closed up the chassis vent slots with vibration damping sheets. I have mentioned that the diyAudio store sell the B1 Korg with a chassis without vent slots and include the vibration damping standoffs.
I still have yet to install film caps on the signal inputs and outputs and a Tocos Cosmos volume pot. I am enjoying the preamp as-is so much, I just want to listen to music. I really have to credit Nelson Pass, Jason and Jim for putting together such an impressive kit.
I need learn more about grouding and good chassis for such tube preamp, it's not Korg is my fault
What voltages You get at T7 , T8 is 9.5V and lot of H2 ?
With trimmers You can adjust to Your taste.
What capacitors in the signal path ?
My are mixture of Elna Silmic and pair of Nichicon Fine Gold in the middle nothing fancy
and B1 Triode sound are wonderful on every style of music. Bass is full not short tnx to Nichicon.
Fascinating audio experience together with class A amplifiers.
I have two older triodes preamplifiers Decware Triode Zen and SRPP Anzai.
B1 Korg is different and have his own audio charm:
extraordinary deep music stage, smoothnes and touch of warm with precision
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B1 Korg is different and have his own audio charm:
extraordinary deep music stage, smoothnes and touch of warm with precision
+1 🙂
I’ve just ordered the pioneer kit and hoped to migrate to a motorized potentiometer and remote volume control. What would be a recommended pot for this application. Is there any reason I shouldn’t do this?
Well, I thought these were great news!
I really long for the day when we live in a truly 'global' world. For me, a $299 kit costs $161 to ship to Ecuador. More than half the price of the unit in shipping. And then import fees and customs... it would end up being a $550+ kit.
It may still be worth it, but at almost twice the price, it's certainly not an easy purchase.
Big hug on these holidays and happy new year!
Rafa.
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The jfet buffer stage circuit is quasi the same in both preamplifiers
just solder 1M resistors at the inputs selector like on this schematic # 395: B1 with Korg Triode 🙂 Cheers
Korg two channels level and wave shape
After my errors bugs correction wave shape , amplitude and distortion are better now
1V output distortionTHD are L = 1.14 % and R= 1.17 % Signals clip at maximum volume = 7 V see on the last pic.
If I play music on my Hi-Fi volume potentiometer are in 9 o clock position and THD = 0.02 ~ 0.03%
After my errors bugs correction wave shape , amplitude and distortion are better now
1V output distortionTHD are L = 1.14 % and R= 1.17 % Signals clip at maximum volume = 7 V see on the last pic.
If I play music on my Hi-Fi volume potentiometer are in 9 o clock position and THD = 0.02 ~ 0.03%
Attachments
Hmm, might be tired, but THD 0.02% sounds very low to me... what output level is that in terms of V?
It is an interesting Multimeter with THD measurement?
I think 0.03% THD is correct during "normal" use and listening level. If sensitive speakers and a power amp with some gain the output voltage needed from Korg is quite low. Also the reason I found Korg more neutral sounding than expected (positive for me)…..and also therefor Korg was a very good combination with MoFo in my setup.
I think 0.03% THD is correct during "normal" use and listening level. If sensitive speakers and a power amp with some gain the output voltage needed from Korg is quite low. Also the reason I found Korg more neutral sounding than expected (positive for me)…..and also therefor Korg was a very good combination with MoFo in my setup.