Thank you Nelson. Thus enlighted, I have tried to find a suitable DC value. Unfortunately I do not have a distortion analyser. I found two points one with R: 13.2V DC and left 18.7V DC giving equal gain at 1KHz. Obviously, this gives a very high distortion and is unlistenably soupy.
I found a different point of R: 9.2V DC and L: 11.3V DC giving equal gain. I will listen to this some more today. Here we should be in negative phase H2 at least for the right channel.
All in all very big changes in DC bias are required to change the gain. If this variation is common in Nutubes, I would suggest to redesign the kit for dual volume controls.
I might try another Nutube at some point as mine is one of the howlers
If anyone has a Nutube that does not ring and has more or less the same gain in both channels, I would love to buy it
Korg Nutube left channel no volume
After some checking I have found the following:
Input signal of 60mV p-p
Q1 input buffer
Left Channel
Source = 0mVp-p
Right Channel
Source 60 mVp-p
Voltage Measurements
Left ch
Q1
D = 21.89V
G = 10.75V
S = 11.89
Q2
D = 11.89V
G = 0V
S = 2.24V
Right ch
Q1
D = 21.15V
G = 10.47V
S = 10.58
Q2
D = 10.58V
G = 0V
S = 1.12V
Resistance
Left Ch
Q1
- +
G D = 166.7ohms
G S = 166.7ohms
D G = OL
S G = OL
Q2
- +
G D = 220ohms
G S = 269.4ohms
D G = 209.4ohms
S G = 254ohms
Right Ch
Q1
- +
G D = 269.7ohms
G S = 166.7ohms
D G = 169ohms
S G = 96.2ohms
Q2
- +
G D = 106ohms
G S = 97.4ohms
D G = 104.3ohms
S G = 96.2ohms
All other T point are with in .5V of expected voltage values
I’m assuming the Q1/Q2 have failed on the left channel input buffer. Any other ideas?
After some checking I have found the following:
Input signal of 60mV p-p
Q1 input buffer
Left Channel
Source = 0mVp-p
Right Channel
Source 60 mVp-p
Voltage Measurements
Left ch
Q1
D = 21.89V
G = 10.75V
S = 11.89
Q2
D = 11.89V
G = 0V
S = 2.24V
Right ch
Q1
D = 21.15V
G = 10.47V
S = 10.58
Q2
D = 10.58V
G = 0V
S = 1.12V
Resistance
Left Ch
Q1
- +
G D = 166.7ohms
G S = 166.7ohms
D G = OL
S G = OL
Q2
- +
G D = 220ohms
G S = 269.4ohms
D G = 209.4ohms
S G = 254ohms
Right Ch
Q1
- +
G D = 269.7ohms
G S = 166.7ohms
D G = 169ohms
S G = 96.2ohms
Q2
- +
G D = 106ohms
G S = 97.4ohms
D G = 104.3ohms
S G = 96.2ohms
All other T point are with in .5V of expected voltage values
I’m assuming the Q1/Q2 have failed on the left channel input buffer. Any other ideas?
Any photos ? What pcb revision ?
Check all solder joints on pcb both sides
Korg pins ? B1 with Korg Triode
Verify resistors values all ok?
Best regards
The Korg B1 is finished and sounds really good, although I can only use it with certain equipment combinations. I'm wondering if it's the grounding of the power supply. The the PS has no reference to ground . Also, If you look at the picture you can see how I thought it should be wired at the power inlet, but I now think this is wrong.
I've used shorter connections from the Korg B1 to the Quad amp and increase the output resistor to 221 ohms but the preamp still rings in this combination. I put the Quad amp on the bench and didn't find much DC on the output.
Using a FW M2X and the Korg B1 with the NuVista Vinyl I get low frequency hum. If use the Korg B1 with the Pearl 2 everything is fine.
Also you'll noticed I wired all inputs and the output with the wrong color RCAs
Other than that everything is great.
Hi, I managed to snag one of the 2nd wave full kits. It went together with no hiccups and is playing as I type through a M2x into a set of Elsinore's MK3. Sounds really good. I put a piece of carpet underlay under the Nutube then some silicone earbud pieces under the pcb leaving the top nut loosely fitted. Seems to be fine no odd noises yet and its siting a bit close to the speaker at the moment playing with settings. Cheers!
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The Pearl II set to 55dB gain with a 4mV MM cartridge will definitely provide a lot of output. So you probably could run it directly into an attenuator and typically drive most power amplifiers to full output. Maybe not as well using a lower output cart.
Unlike the original Pass B1, the B1K is designed to accommodate input switching and attenuation separate from the main PCB and ahead of its inputs. Most builders put the switching and attenuation into the same chassis as the B1K. So building your source selection and attenuation as a separate component could work if you want the Pearl to bypass the B1K. You will still need an attenuator to control Pearl volume. Perhaps there is one built into your power amplifier.
There are other factors, however:
1. The B1K adds its own sound character. I prefer using it for all sources, phono included. So, in that case, there is no advantage to outboard switching/attenuation. I agree with 6L6. Just run all your sources, including the phono preamp, into the relay source selector, then the attenuator and then the B1K.
2. It partly depends on whether you care about absolute signal polarity or not. There are conflicting opinions on this issue. Some say reversed polarity is inaudible. I like to think I can hear the difference and typically prefer my source material in the same polarity as it was produced.
Since the Pearl II inverts polarity and the B1K also inverts polarity, absolute polarity remains unchanged when those two are paired. To my ears it is a match made in heaven. However, switching to a source other than the Pearl would then have its polarity inverted by the B1K.
Most folks who care about B1K signal polarity just reverse their loudspeaker wiring. That would be cumbersome every time you switched sources between the Pearl and something else. I'd say, hook all this up and see if it makes a difference to you. You actually might hear more difference between a 50K attenuator and a 10K attenuator than the signal polarity issue.
I have spent more time playing with psu on my korg B1.
I definitely prefer a linear lm317 supply vs. a switcher. It has a deeper stage, and more precise imaging. Lm317 is also a bit brighter.
Thinking out loud here...is there a better solution for the heaters other than diodes? Lm7809 perhaps? Is a separate heater supply a better solution? Even a battery would work.
I definitely prefer a linear lm317 supply vs. a switcher. It has a deeper stage, and more precise imaging. Lm317 is also a bit brighter.
Thinking out loud here...is there a better solution for the heaters other than diodes? Lm7809 perhaps? Is a separate heater supply a better solution? Even a battery would work.
Are those Jfet measurements with the AC signal off?
Check that the 1k input resistor and the 10uf cap before it for Lch are installed and soldered correctly?
nash
Hi Hikari1,
May I ask what switcher have you been using and where it is located?
On my limited side I found the differences between my wallwart SMPS and a regulated lab linear PS with large power delivery capacity very small, and in fact I wasn't able to tell which one sounded better as more a matter of (small) preference TBH.
But then I used a SMPS that is remote and that has lower ripple and (slightly) higher current than the one recommended, while being similar in price. So at the end one that shall be quiter for the low current needs we have, while allowing to start with marger caps, and not a too oversized unit that may run at idle.
After that, playing with the PS caps on the board brought very small improvements, so sides PS I considered things as settled once I upgraded slightly SMPS specs and caps size.
on the board
So for me, and I am defo not a SMPS fan, Papa's design is very clever and satisfying in that regard. Selected outboard wallwart SMPS and slightly bigger caps proved to be more than fine and playing with that path anyway yeld very small improvement possibilities compared to the caps in the signal path or the right volume pot. In short, as designed it was already say 95% fine.
On the other hand, I could understand one may want to adjust the tonal balance of the B1K playing with various PS, or perhaps one may suffer from other things if using say a traditional very large Meanwell SMPS inside the same casing, hence the question on what SMPS you have been using.
Good luck playing with PS and thanks again for letting us know your findings
Claude
May I ask what switcher have you been using and where it is located?
On my limited side I found the differences between my wallwart SMPS and a regulated lab linear PS with large power delivery capacity very small, and in fact I wasn't able to tell which one sounded better as more a matter of (small) preference TBH.
But then I used a SMPS that is remote and that has lower ripple and (slightly) higher current than the one recommended, while being similar in price. So at the end one that shall be quiter for the low current needs we have, while allowing to start with marger caps, and not a too oversized unit that may run at idle.
After that, playing with the PS caps on the board brought very small improvements, so sides PS I considered things as settled once I upgraded slightly SMPS specs and caps size.
on the board
So for me, and I am defo not a SMPS fan, Papa's design is very clever and satisfying in that regard. Selected outboard wallwart SMPS and slightly bigger caps proved to be more than fine and playing with that path anyway yeld very small improvement possibilities compared to the caps in the signal path or the right volume pot. In short, as designed it was already say 95% fine.
On the other hand, I could understand one may want to adjust the tonal balance of the B1K playing with various PS, or perhaps one may suffer from other things if using say a traditional very large Meanwell SMPS inside the same casing, hence the question on what SMPS you have been using.
Good luck playing with PS and thanks again for letting us know your findings
Claude
Interesting. Since I have a spare (expensive) 24volt Ultra low noise PS board and nothing better to do with it i've ordered up a 2U Galaxy case, nuts, bolts and washers and IEC socket and now waiting for shipping quote on a small Toroidy transformer that will fit in the case.
Mix of shipping countries and couriers so it'll be a while before everything turns up. Happy to spend a few bucks more than an SMPS because I believe tiny changes could make a noticeable difference with 106db per watt speakers at sensible listening levels.
I'll let you know how I get on - first parcel to arrive will be the DIY Audio shop case direct from Italy about 10days to NZ from point of order normally. Fun hobby this
Here you go.. a Coleman style filament supply(45,2A3,211,etc). Isolate the circuit with a dc/dc. Cleanup the dc with a VREG. A resistor to help isolate the supply capacitance from the filament. Finished with a CCS (LT3092) on the backside. Ordering a PCB soon. Should be interesting ��
Congrats on your nutube adventures !
Dwight
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Switching supply is a big meanwell s-240. It is outboard of the chassis, so no problems there.
There is not a difference in noise in linear vs switcher but the presentation is different. Linear is slightly more 3D and refined. Also, the linear supply sounds slightly more dynamic and lit up. It is not a major difference, we are talking about getting the last 1% of performance out the circuit.
Also, for others who are wondering I find that absolute phase is very important.
Iam still auditioning b1 korg vs my solid state preamps. There is no question that the b1 korg lacks slam and the crisp leading edges of my solid state gear. But it sounds so much more 3D in depth and space than my SS preamps. And the soundstage is much bigger. And it has a slight “reverb” like quality that makes some recordings really special. Compared to korg the ss preamps sounds very dry.
I would love to have the soundstage and ambience of the korg with the dynamics and crisp snare cracks on drums of my solid state preamps. Please tell me if this exists...I would pay a lot of money for these two virtues combined.
I have built ba-3 with adjustable harmonics and 2 f5-like preamps where the harmonics can be adjusted. Spent time with analyzer to get harmonics where I like them on those preamps. The effect is not the same. Yes, it can be adjusted but they do not sound like the korg.
Also have an single ended ss pre (Salas dcg3) that does not sound similar although the bass is very satisfying.
Perhaps it’s the triode curves that are special.
Also have an single ended ss pre (Salas dcg3) that does not sound similar although the bass is very satisfying.
Perhaps it’s the triode curves that are special.
Hi Hikari1,
Thanks for your reply...
I found the PPP caps tweak brought more crispness and dynamic than before, as did also reducing the H2 level (so playing with the setting). That brought more speed and edges and reality and a tad "less sirup", while retaining IMHO a fantastic soundstage and still a wonderfull and nice sound.
Regarding the PS, if you are refering to the Meanwell S-240-24 then this unit has more than twice the ripple than the SMPS I use (specs say 180mV p-p vs 80mV p-p) , and IMHO that value is quite relevant although one has to ponder how it is measured, but as mine is a Meanwell aswell (SGA25E24-P1J) I take it that yours has quite a lot more ripple. I can't remember the specs of Papa's recommandation, but wasn't that 120mV p-p ripple?
Admittely other specs of your PS are better, but I am not sure they are relevant to the sound (well, if any specs is, as specs are just specs and not ears so my thoughts might be wrong) plus I am also worried that a SMPS like yours, designed for 10A outputs, might be an overkill that may encounter other difficulties when asked only 60mA (once started) for the B1K, so in fact running at idle or so. My unit was designed for max 1A and has already quite a margin regarding the 500mA specified by Papa (these to enable probably a fail safe start up in various configurations and tolerances, including probably people increasing the PS cap values).
Just thinking loud, it may or not be relevant, but before using your large SMPS have you been using the SMPS Papa recommended, or say a similar upgraded one like the one I use?
Good luck with your fine tuning
Claude
Thanks for your reply...
I found the PPP caps tweak brought more crispness and dynamic than before, as did also reducing the H2 level (so playing with the setting). That brought more speed and edges and reality and a tad "less sirup", while retaining IMHO a fantastic soundstage and still a wonderfull and nice sound.
Regarding the PS, if you are refering to the Meanwell S-240-24 then this unit has more than twice the ripple than the SMPS I use (specs say 180mV p-p vs 80mV p-p) , and IMHO that value is quite relevant although one has to ponder how it is measured, but as mine is a Meanwell aswell (SGA25E24-P1J) I take it that yours has quite a lot more ripple. I can't remember the specs of Papa's recommandation, but wasn't that 120mV p-p ripple?
Admittely other specs of your PS are better, but I am not sure they are relevant to the sound (well, if any specs is, as specs are just specs and not ears so my thoughts might be wrong) plus I am also worried that a SMPS like yours, designed for 10A outputs, might be an overkill that may encounter other difficulties when asked only 60mA (once started) for the B1K, so in fact running at idle or so. My unit was designed for max 1A and has already quite a margin regarding the 500mA specified by Papa (these to enable probably a fail safe start up in various configurations and tolerances, including probably people increasing the PS cap values).
Just thinking loud, it may or not be relevant, but before using your large SMPS have you been using the SMPS Papa recommended, or say a similar upgraded one like the one I use?
Good luck with your fine tuning
Claude
Well this is very interesting. Since I would be modifying the stock pass pcb I can’t use smd parts. But I understand what you are doing. Same thing could be accomplished with chokes and lm7809 on the diyaudio boards I think?
I tried a 32v smps from a laptop followed by lm317. Prefer the linear supply followed by lm317.
My point is not that smps are bad...but rather that this circuit IS effected by pay quality...and that the Onboard RC filters while a good idea are probably not the ultimate solution. Iam not a fan of lm317, I plan to try the jung regulator with more capacitance before the regulator as well.
But to do that I need to sacrifice one of my solid state preamps. Iam close to making that sacrifice...since I can’t seem to stop listening to the korg.
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