I received the full-kit during the week, but was busy so...
I built it over the weekend. Saturday for the board and components, Sunday for the hardware and the hookup of the teensie-weensie little wires. Boy, I hated stripping those!
Two mistakes:
Digital source through Korg Nutube into recent F6 build out (with speaker cables phase reversed) to my Hsu HB1 Mk2 bookshelves+sub combo (speaker level in on the sub). The Hsu bookshelves are an interesting little directivity-controlled horn and 6" woofer imaging machine with incredible timbre. Really worth looking into.
I enjoyed having Ella Fitzgerald in the living room so much that I asked my wife to come in and meet her. I played Our Love is Here to Stay off of the American Songbook collection for her and got a genuine "wow!" out of my wife. But seriously, the combination simply, easily defined the size of the recording studio, and Ella was front and center and up and present. Throughout the evening the setup would simply point out things, ever-so-evident, in recordings I thought I was intimately familiar with, that I had never noticed before.
What fun!
I built it over the weekend. Saturday for the board and components, Sunday for the hardware and the hookup of the teensie-weensie little wires. Boy, I hated stripping those!
Two mistakes:
- One of the volume pot wires popped off when I was soldering the other end to the PCB, so I soldered it right back on- in the wrong spot. Let me tell you, when you bypass the volume pot on a channel, IT PLAYS REALLY LOUD FOR A FEW SECONDS WHILE YOU PANIC AND FIND THE AMP'S POWER SWITCH! KILL SWITCH! KILL SWITCH! My kids got a good laugh at me.
- I swapped left and right channels from the input selector switch to the volume pot A&B in connections. At first I was blown away because I could swear Bonham's high-hat at the beginning of Good Times, Bad Times was on the other side of the room. Wow, this little tube alters space and time! Easy enough to repair.
- I wanted to experiment with the varying voltage levels to see what difference settings made, so I left the cover off and had a voltmeter and trimmer screwdriver handy. Yes, tapping the side of the unit or flicking a selector switch would definitely ring for a few seconds. While playing music you could hear a sharpness to the sound, which I'll assume was it resonating around that 5k peak. It was definitely there, and the unit wouldn't be useful until eliminated.
- That said, I gave it an hour or two with it set at 12 volts, which yielded detail, but no depth, no joy.
- Setting it down to 9.5: voila! depth, joy!
- As for damping. I used the supplied double-sided foam tape under the tube when mounting to the PCB, then took the soft foam block from the box the tube came in, flipped it sideways, and stuck it to the bottom of the case's top cover with a layer of double sided foam tape. This was just tall enough that the cover was putting light, holding pressure onto the tube. Cover on, little rubber feet attached, set it on about 100lbs of solid amplifier stacked and listened. Ring is gone from sound bouncing off it, but clearly there and damped when a switch is flipped or the case is tapped. It disappeared from influencing the sound as best my ears can tell; I forgot all about it and enjoyed the music.
Digital source through Korg Nutube into recent F6 build out (with speaker cables phase reversed) to my Hsu HB1 Mk2 bookshelves+sub combo (speaker level in on the sub). The Hsu bookshelves are an interesting little directivity-controlled horn and 6" woofer imaging machine with incredible timbre. Really worth looking into.
I enjoyed having Ella Fitzgerald in the living room so much that I asked my wife to come in and meet her. I played Our Love is Here to Stay off of the American Songbook collection for her and got a genuine "wow!" out of my wife. But seriously, the combination simply, easily defined the size of the recording studio, and Ella was front and center and up and present. Throughout the evening the setup would simply point out things, ever-so-evident, in recordings I thought I was intimately familiar with, that I had never noticed before.
What fun!
DNic
Not really. Theoretically you don't need any resistors at all unless one of the two downstream inputs is loading things down somehow. It would be helpful to know the input impedance of each connected device. You typically want to keep the paralleled inputs combined impedance above 10K.
What you have shown in your photo provides 1K of isolation between the two downstream inputs, no isolation between the B1K and input #1 and 1K of isolation between the B1K and input #2. You may need that, or nothing, or more depending on the device inputs, their impedance and capacitive loading characteristics.
Any resistance will cause some signal loss but input circuits do have the slight possibility of interacting in some strange ways. Safest solution is separate active buffered preamp outputs but that can have drawbacks as well, depending on the quality of the buffers.
Not really. Theoretically you don't need any resistors at all unless one of the two downstream inputs is loading things down somehow. It would be helpful to know the input impedance of each connected device. You typically want to keep the paralleled inputs combined impedance above 10K.
What you have shown in your photo provides 1K of isolation between the two downstream inputs, no isolation between the B1K and input #1 and 1K of isolation between the B1K and input #2. You may need that, or nothing, or more depending on the device inputs, their impedance and capacitive loading characteristics.
Any resistance will cause some signal loss but input circuits do have the slight possibility of interacting in some strange ways. Safest solution is separate active buffered preamp outputs but that can have drawbacks as well, depending on the quality of the buffers.
Agreed. Also, the output buffer will drive about 3k without burping. Second harmonic is higher, but that's what you stopped worrying about long ago...
Hi, I have a problem with my korg nutube B1.
There are some random crackling noises on the left channel.
I built it in December 2020. The only thing I changed since then was to add two 7.5kOhm resistors before the power led.
But I think that is not the problem because the crackling noises started a while after that.
I tried different cables, checked the rca connections, tried it with my stereo system and with my Computer Speakers, and also from inspecting the inside I can't find a problem. The measurments are also right:
T1 = 24V, T3 = 23V, T4 = 9V, T5 and T6 are at 0.6VDC, T7 and T8 are at 9.5VDC.
The crackling noises are there even when no music is playing.
I think maybe it's a faulty korg nutube?
Before ordering a new korg nutube I thought I post my problem here.
I hope you can help me with this.
There are some random crackling noises on the left channel.
I built it in December 2020. The only thing I changed since then was to add two 7.5kOhm resistors before the power led.
But I think that is not the problem because the crackling noises started a while after that.
I tried different cables, checked the rca connections, tried it with my stereo system and with my Computer Speakers, and also from inspecting the inside I can't find a problem. The measurments are also right:
T1 = 24V, T3 = 23V, T4 = 9V, T5 and T6 are at 0.6VDC, T7 and T8 are at 9.5VDC.
The crackling noises are there even when no music is playing.
I think maybe it's a faulty korg nutube?
Before ordering a new korg nutube I thought I post my problem here.
I hope you can help me with this.
Noise the same with shorted inputs? Could you try shorting the left channels inputs @ the PCB, and report findings.
is the noise there/the same on both inputs?
I think I would recheck the 7R5k solder joints, but maybe more relevant are your JFETs.
do you own a scope? If so, scoping your way down the signal chain referenced to gnd could enable you to narrow it down quite a bit.
I have experienced this only once. It was due to a scratch in the PCB under a SMD JFET and/or fried JFET or cold solder joint (never narrowed it down 100% really) In other words not very visible 🙂
Regards,
Andy
Thank you for your quick answer.
Can you explain what do you mean by shorting the inputs @ the PCB and how I can do this?
The noise is only on the left speaker. Not on both.
I checked the solder joints of the resistors and of the jfets. Can't find a problem with them.
I dont know the term "scope". Do you mean with scope a multi meter?
EDIT: Sorry, i misunderstood the question. There is noise on both inputs yes, and it's the same. It is not dependent on the input.
EDIT 2: I found something. When there are no cables connected to the inputs. There is no crackling noise.
SOLVED: Cleaned the pcb a little bit and there is no crackling noise anymore. Thank you, andynor for your help.
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Nice stuff... but I got to slow down. I just put down the first tranche of money for the A2 build.... just paid for the rebuilds of the Marantz 2325 and Sansui G-7500 and I got the Akai AS980 being worked right now.
I "broke" the news to my wife about the A2 build today.... I made her a very nice cappuccino (I'm really good) and non-chalantly I told her about it. My excuse is that I can't find a pair of OEM Aleph 2s and she knows if I ever find them it will cost about $5K after taking them to the factory for refurbishing... (*) so the A2 will be cheaper and is being done by a DIY'er who knows what he does ( and does it very well). He rebuilt my A5s and my wife agrees they sound fantastic, just not quite enough oomph for the Maggies.
However, the wife did mention that I've been "spending a lot of money on the stereo" lately... so she hopes this is the last.... I don't know how I'm gonna hide the new pair of speakers. I think I'll need to sell some stuff.
Anyone want to buy a fully rebuilt Marantz 2325 receiver? Honestly, time does move on and it sounds like vintage. I dunno why people like those things... now I know why in '76 I traded my Marantz SR2220B for a Kenwood KA-3500 (I still have that one)... I mean, the Marantz sounds as good as ever, but it sounds... dark. The Sansui, OTOH, has pace. That's a keeper for sure.
(*) One of the reasons why she likes the idea of my getting the OEM Aleph 2s is that we'd get to spend some time in Reno (on the trips to the factory). She likes the machines, I like smoking cigars indoors.
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At the risk of hi-jacking this thread, I will simply say that the KA-23500 was my first amplifier in college (1975) and I would NEVER, ever go back to that, much less buy it and restore it. Right now, I am using a Scott 200 integrated tube amp, which I bought used for $200 in 1996. It needs more work (I've had it in the shop for refurbishment once in the mid 2000s - taking off the case and then re-attaching it seemed very difficult without special jig).
I've decided to build F5 Turbo with 32V rails, no Vishay diodes, dual mono PS, Neurochrome speaker protection for amp. Right now, am collecting parts for a B-1 build with Pete Millet output mute, line AC filter per Bottlehead Audio, and 24V regulator from TubeCAD/Glassworks (I also will be using their A3 attenuator). For me, the music is the final objective and spending ungodly amount of money and time moving from piece of kit to another makes no sense to me. For the record, I've built stuff since college, starting with Dynaco and moving through Marshall Leach; and upgraded several Magnavox CD players per Audio Amateur articles, so its not like I don't like DIY (why am I here anyway, if not basically DIY at a rudimentary level).
I've decided to build F5 Turbo with 32V rails, no Vishay diodes, dual mono PS, Neurochrome speaker protection for amp. Right now, am collecting parts for a B-1 build with Pete Millet output mute, line AC filter per Bottlehead Audio, and 24V regulator from TubeCAD/Glassworks (I also will be using their A3 attenuator). For me, the music is the final objective and spending ungodly amount of money and time moving from piece of kit to another makes no sense to me. For the record, I've built stuff since college, starting with Dynaco and moving through Marshall Leach; and upgraded several Magnavox CD players per Audio Amateur articles, so its not like I don't like DIY (why am I here anyway, if not basically DIY at a rudimentary level).
Interesting.. I assume the KA-3500?
I got a collection of stuff and I'm getting rid of some, rebuilding the few I will keep. I'll keep the 3500 because I've had it since new, and I got the matching KT-5300. I also got the carrying handles... including the box they came with! So, that one is sentimental. I'll get it cleaned up and then I'll keep them on a shelf in my office, mostly as part of the display collection. Powering it up every so often to keep it honest.
I agree that when it comes to vintage, stuff in the 70s and before, pretty much it's up to tubes, VFETs and whatever Nelson Pass was doing at the time.
Although, I gotta tell you that my Sansui G-7500, fully restored to original spec (those power transistors were VERY hard to get.. ended up with used ones) sounds very good. it doesn't project much depth in the soundstage, it's mostly 2D, but the musical picture it presents is very broad with solid instruments and really nicely balanced.
The F5 Turbo.. funny, I was planning on getting a F5 Turbo V3 built, dual mono configuration, but at the last minute I decided to go with the A2's first because that's the amp I've been lusting for years and the A5 monos make my Maggies sing.. so I figure the A2 will sound even better.
I'm planning on getting the F5 Turbo V3 built sometime this fall. These amps will replace my current F5 and A5 monos (all DIY). I might sell those two then... who knows?
Oh, It's been a long time since I built serious stuff... like Heathkits and Dynacos. I can fix small things with my iron but I don't have a scope or function generator anymore. But, I can read schematics... let's say I'm a typical engineer when it comes to such... I let the technicians do the build and then I smoke it when I test them with 100VDC.... ooops!
That's also why I like the DIY world. I can appreciate it and understand the designs and build quality. So, commercial stuff is fine for doctors, laywers, accountants, anyone with a Bachelor of Arts or Business or something like that. I prefer the value of DIY and have no problem opening the box and troubleshooting a bit... I can easily detect smoke! ;-) Besides, it doesn't entail ungodly amounts of money.
Oh, this is the B1Korg... One thing I have wished for in the B1 is three inputs, a tape monitor and either a balance control or dual volume pots. My B1 and B1K are standard (OK, the B1K is not, it has the additional power supply filtering and the floating mount for the tube). I mean, I love they way they sound, but they can not work in my main stereo because I have an AD/DAC as a digital tape deck, plus tuner, another DAC in the AUX and a turntable... that's three inputs plus a tape!
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I’m using the tape monitor out of my current Nakamichi CA5 pre-amp to feed my B1K. It’s basically a selector switch that can stay off unless I want to use the phono stage.
this also lets the kids use the Naki and another amp/speaker combo for the TV, and I get the B1K+F6 and speakers for me. I have a spare input on the B1K!
But that puts the Nakamichi in the chain! I mean, yes, it's a good sounding unit, but don't you think it colors the sound?
In my case, I got a fully upgraded (Teflon caps, etc..) CJ PV9... it has two line level outputs. One set goes to the A5 and Maggies, the other to the F5 and ADS L810s ( or recently the Sansui/Marantz receivers ). So, I normally put the B1K ahead of either amp, but that's not full time. In my main audio system I want to hear the CJ... so I'm thinking of building another system around the B1K. But I don't know where to put it...
I ought to note that the CJ/B1K combo is very good... and just think... two volume controls, two power switches, a more complex power ON/OFF sequence. More cables, more lights...
Well, when the Naki is off, it's simply a selector switch. No signal is amplified going out the tape monitor, so no real chance to color the sound other than more wire and connections.
I suppose I could look to the Naki schematic and see how it routes whichever input is selected into the amplification circuit, but since everything works conveniently, no real need.
It is a good sounding unit, especially the phono stage. The B1K is teaching me new things entirely. At some future date I'll open up the Naki and see about its (almost guaranteed to be original) components and do a refresh on it. But I've got some other projects lined up first.
Yup, that has been my mode of operation as well before the B1K: one pre, two outs, two amps, two speakers. Of course I now have 5 amps to play with.
Having two pre-outs sure does make it easy to compare and contrast. What I really need to do is build a multi-source-multi-amp-multi-speaker set of selector switches (probably with volume leveling pots in them) so I can sit and flick from one amp to the next, choose the speakers, choose the pre, choose to...
Or maybe I could just listen to the music and enjoy. 🙂
All this and not a remote to be found for volume or selection. Good thing I have kids!
I believe in complexity... boxes, lights, cables, switches, knobs, things that spin, plug, twist... Rube Goldberg would love my ideas...
As far as switching cables, though, I prefer to reach over and unplug and plug. I mean, no switch is the best switch... inconvenient.. you betcha.
Awesome.
You ought to see me... hit the laptop or tablet to play music... nothing comes out.. hmm... volume and switch in the PC/tablet, DAC, preamp 1, preamp 2... cables... etc...
So, for remote, since I use a laptop to play the music in the network and an Android tablet to do Tidal.... well, I use the Wifi in the house to connect from my PCs or other tablets as a remote via Remote Terminal.
Of course, you just know that my turntable has to have an external power supply! The Lingo has its own power switch with a hidden front panel ON/OFF light... why did they recess it so much? Maybe they had too much haggis for lunch that day and they screwed up the mechanical drawing...
Now, in terms of complexity, I think I'm at the Rube Goldberg Audio Apex.
I must say, however and quietly, sotto voice, that I've been listening to the Sansui G-7500 I just had rebuilt. I got two pairs of speakers on it.. .so I can use the A, or B speaker selector... it has a loudness control.... oh, oh....
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Hi everyone, sorry I have to bother you guys with a problem I am having. I just build the Korg B1 with the JFET set from the diyaudio store. Everything went fine, Voltages T1 to T6 all check out perfectly. T8 is also adjusting fine.
T7 however, I cant get the bias to go any lower than 14.3V. The left tube is visible brighter as well, accordingly.
I checked all the resistors before putting them in, and after again. Caps are all oriented correctly.
I changed out the left pot and the 10uF cap next to it, to no avail.
Going through the above posts, the Voltages across the R1 resistors all check out symmetrically. The 33.2K resistors differ in their voltage drop, but that is down to the pot adjustment, right... I can adjust the pot to match the the right channel, and the pots end up in roughly the same position. However T7 is 14.57V while T8 is 9.49V.
Any hints as to what might be the problem? could it be the nutube? Or could there be a transistor problem? Thank you so much, I don't have much of an electronics background, and this is my second project (after an ANK Dac many years ago). I am at a loss here... 🙁
I'd suggest posting some good pictures of your board, it's always helpful to have another (few) extra pairs of eyes to check your board for anything that you may have missed 😉
Ok here goes it comes:
It's not much, but it is mine 😅
On the plus, in a brief right channel test, absolutely zero microphonics.
Thanks to everyone
It's not much, but it is mine 😅
On the plus, in a brief right channel test, absolutely zero microphonics.
Thanks to everyone
Hello sti571,
are you absolutely sure that no 33.2kOhm- resistor was confused with a 332kOhm - resistor?
Did you measure the resistors before inserting? I believe that you checked.
Did you check by numbers (if you used DALE-resistors) and / or the colourrings?
Sorry for my questions! You would not be the first.
And as seipersei wrote: a few pics of the top and the bottom of the pcb could help.
On this forum are a few 'eagle-eyes'. Not me...
Cheers
Dirk
are you absolutely sure that no 33.2kOhm- resistor was confused with a 332kOhm - resistor?
Did you measure the resistors before inserting? I believe that you checked.
Did you check by numbers (if you used DALE-resistors) and / or the colourrings?
Sorry for my questions! You would not be the first.
And as seipersei wrote: a few pics of the top and the bottom of the pcb could help.
On this forum are a few 'eagle-eyes'. Not me...
Cheers
Dirk
Hey Dirk, yeah I am sure. I measured the resistors with a multimeter 😬 thank you anyways. I'll post a photo of the bottom as well..Hello sti571,
are you absolutely sure that no 33.2kOhm- resistor was confused with a 332kOhm - resistor?
Did you measure the resistors before inserting? I believe that you checked.
Did you check by numbers (if you used DALE-resistors) and / or the colourrings?
Sorry for my questions! You would not be the first.
And as seipersei wrote: a few pics of the top and the bottom of the pcb could help.
On this forum are a few 'eagle-eyes'. Not me...
Cheers
Dirk