Putting the B1K aside for a while an moving on to the F5. But will need the Chassis to become available now. But making progress on the build anyway.
I would also like to be sure the solder joints are looking like they are suppose to. So far everything I've done works, but thought I'd at least have the experts comment. I am using Kester 44 solder recommended in the "Solder 101" article.
I would also like to be sure the solder joints are looking like they are suppose to. So far everything I've done works, but thought I'd at least have the experts comment. I am using Kester 44 solder recommended in the "Solder 101" article.
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Going back through the thread, I think my numbers are in line with others. So I decided to hook up to ACA amplifier and 93dB speakers. Now this is just a bench test of the Korg B1. It is not in a chassis and there is loose cabling strewn about. I have the ACA and Korg B1 temporarily connected to same the SMPS.
Test 1: The source is a Parts Express DAC using the headphone output so volume pot control can be employed. A crazy loud buzzing is being produced with volume at zero. So loud that I have to shut down the amplifier immediately at startup.
Test 2: If I entirely remove the Korg B1 from the signal path, the amplifier from DAC plays perfectly fine.
Test 3: If I use my television as source, the same buzzing does not occur. Though there's extreme static or something. It feels like the noise floor is being raised way too high.
So I am a bit worried right now. The Korg B1 is definitely doing something undesireable from multiple sources. These are sensitive speakers, but not too much. Maybe ground loop could be a factor, but I don't think that explains entirely. Is this a microphonic tube? Shocked if that's what I am hearing, but maybe. And yes, I am well aware my testing methods sound a bit ridiculous... this is what I have on hand at the moment.
Test 1: The source is a Parts Express DAC using the headphone output so volume pot control can be employed. A crazy loud buzzing is being produced with volume at zero. So loud that I have to shut down the amplifier immediately at startup.
Test 2: If I entirely remove the Korg B1 from the signal path, the amplifier from DAC plays perfectly fine.
Test 3: If I use my television as source, the same buzzing does not occur. Though there's extreme static or something. It feels like the noise floor is being raised way too high.
So I am a bit worried right now. The Korg B1 is definitely doing something undesireable from multiple sources. These are sensitive speakers, but not too much. Maybe ground loop could be a factor, but I don't think that explains entirely. Is this a microphonic tube? Shocked if that's what I am hearing, but maybe. And yes, I am well aware my testing methods sound a bit ridiculous... this is what I have on hand at the moment.
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Other considerations:
All caps are rated for 35V.
Computer nearby. TV and computer on same power strip.
I have no volume pot attached to Korg B1. I have no intention of controlling volume with it, but rather control at digital source. Does the volume pot provide something I am missing?
My values all match silkscreen. Caps and diode oriented correctly. All solders look good. I see no evidence of bridges. Though it did look like a bridge between F1 pads on top... but this appears to be bare copper where solder mask is missing from PCB. Looks like F1 pads connect anyway, so fine?
I fear the zener diode is the one component I did not test. As I may not have figured out how to do it. Or perhaps did not realize what was beyond acceptable tolerances.
I will try operating Korg B1 and ACA with no source connected. I did not think of this, but it might help to isolate where issue is emanating from.
All caps are rated for 35V.
Computer nearby. TV and computer on same power strip.
I have no volume pot attached to Korg B1. I have no intention of controlling volume with it, but rather control at digital source. Does the volume pot provide something I am missing?
My values all match silkscreen. Caps and diode oriented correctly. All solders look good. I see no evidence of bridges. Though it did look like a bridge between F1 pads on top... but this appears to be bare copper where solder mask is missing from PCB. Looks like F1 pads connect anyway, so fine?
I fear the zener diode is the one component I did not test. As I may not have figured out how to do it. Or perhaps did not realize what was beyond acceptable tolerances.
I will try operating Korg B1 and ACA with no source connected. I did not think of this, but it might help to isolate where issue is emanating from.
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Hi,
I will leave the experts properly reply, but I read somewhere in the numerous pages that the B1 Korg needed to be loaded - by a potentiometer for example, say at least 10k, recommended are anything between 20 and 50k. So that is something perhaps worth considering before going further? Saying that as you posted 'no volume pot attached' so I presume load is very few as outputstage direct, probably less than 1k ?
If no help, is that buzz a PS buzz (say anything quite low frequency, hence looking into connections and ground), or rather high frequency pitch etc.?
I will leave it to the real experts from there on
Claude
I will leave the experts properly reply, but I read somewhere in the numerous pages that the B1 Korg needed to be loaded - by a potentiometer for example, say at least 10k, recommended are anything between 20 and 50k. So that is something perhaps worth considering before going further? Saying that as you posted 'no volume pot attached' so I presume load is very few as outputstage direct, probably less than 1k ?
If no help, is that buzz a PS buzz (say anything quite low frequency, hence looking into connections and ground), or rather high frequency pitch etc.?
I will leave it to the real experts from there on
Claude
A fellow DIYer has kindly passed me his Korg to fix my preamp up first. All the test points are within 0V5. Here's the puzzling thing, I get a loud buzzing sound which I did not get from my earlier NuTube and the T7 and T8 are measuring 20V.
Looking at the schematic, the only possibility is Q1 and Q2 are fried.
Any way for me to check with the components in place on the PCB?
Looking at the schematic, the only possibility is Q1 and Q2 are fried.
Any way for me to check with the components in place on the PCB?
Thanks ZM. Yes I used Papa's guide and compared. I stared at my connections further and am too embarrassed to tell you that I have missed connecting 2 lines from the NuTube. I am now able to bias it to 9V25 on both sides. So embarrassing. Sorry.
T4 is a little high (probably not the source of your problem though). I bought 10x 9.1v zeners and they varied quite a bit. I chose the closest value to 9.1v.
As to your main problem, have a read around this area for some nuggets regarding loading the input:
B1 with Korg Triode
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) to temper the output. Then either connect up to sacrificial headphones or try through your amp again with the preamp inputs shorted.
Basically, set it up per the schematic and get it to work, then start to modify from there. Good luck!
Also, consider uploading photos of your boards so that you might have a 'second set of eyes' go over your board, so to speak.
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For anyone else who plan to do what Dirk and I did, i.e. extend the NuTube to a display window, it might wise to mount the NuTube to an external PCB so provide more rigidity for the connection to the pins. My first NuTube was connected to the pins directly and they flex any too much. Slight movement of the wires will cause the pins to touch if they are not heat shrinked properly for insulation.
I decided to make this project using as many of the components and parts that I already had as I could. I am glad that I didn't toss the enclosure that was from a dead DAC.
I did the "stuff a fat lady into a girdle" thing and was able to get those ridiculous, large caps glued into place without fouling anything.
I placed a sheet of Sorbothane beneath the Nutube and also beneath the board, on top of some washers on the stand-offs. The top and bottom of the case also have sheets of Deflex. Tapping the enclosure stoutly with my finger does nothing.
All the volts are within spec, and I am getting used to it now. I look forward to comparing it to my current preamp, which is an AKSA-Lender that I am very happy with.
I did the "stuff a fat lady into a girdle" thing and was able to get those ridiculous, large caps glued into place without fouling anything.
I placed a sheet of Sorbothane beneath the Nutube and also beneath the board, on top of some washers on the stand-offs. The top and bottom of the case also have sheets of Deflex. Tapping the enclosure stoutly with my finger does nothing.
All the volts are within spec, and I am getting used to it now. I look forward to comparing it to my current preamp, which is an AKSA-Lender that I am very happy with.
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Haha! I should have called it "spares-tin version", as that is where I keep all my parts.
I haven't used this version PIO before. I've got a very slight, medium-pitched warbling right now that seems to be caused by the input caps. Grounding the Input capacitor cases attenuated the warbling a bit. I'll be swapping them out for others until I find the combination that I like best. I put some K40-Y9s in a Marantz 7 once and was dismayed to hear that it lost some clarity. I was told to sit on my hands for 200 hours. The "snap" of real music finally came back (or my brain manufactured it) after about the 200 hours mark.
Today I have just been jumping through my music collection enjoying the different sound of this preamp. I was listening to the sound stage wrapping around to a point directly parallel to my ears at one point. These speakers had never done that before. I really like that!
I haven't used this version PIO before. I've got a very slight, medium-pitched warbling right now that seems to be caused by the input caps. Grounding the Input capacitor cases attenuated the warbling a bit. I'll be swapping them out for others until I find the combination that I like best. I put some K40-Y9s in a Marantz 7 once and was dismayed to hear that it lost some clarity. I was told to sit on my hands for 200 hours. The "snap" of real music finally came back (or my brain manufactured it) after about the 200 hours mark.
Today I have just been jumping through my music collection enjoying the different sound of this preamp. I was listening to the sound stage wrapping around to a point directly parallel to my ears at one point. These speakers had never done that before. I really like that!