Can’t wait to see one of your finished Pass DIY power amps. Hopefully, it will have the same design details as your B1 NuTube preamp.
Wow the final result is really cool, I like how it turned out! 🙂 Next time you should have us print other colors as well 😛
Thanks Kevin! Completely understand your logic 🙂. At full output with 1Khz test I downloaded I was getting 366mV, with the 50Hz test track from the Dayton Omnimic kit I get 466mV. So the 1Khz test track was created at a lower level. With the alps pot at full volume I get full voltage at both channels at the input block on the board. With music it goes way higher - the Dragonfly v1.2 is capable of 1.5v output.
My B1 Korg build...
For a friend. Testing it now. Sounds wonderful! All voltages were as supposed to be with a smidge touch of the pot dials. Have to organize better the wiring. Big soundstage and dynamic. I’ see how it compares with my ba3 LS. Cd transport 47 Lab Shigaraki, dac Twisted Pear Audio B3 SE, Pass xa25 and F4 amplifiers. Spatial Audio M4’s TM and diy pair of Ripole subwoofers.
For a friend. Testing it now. Sounds wonderful! All voltages were as supposed to be with a smidge touch of the pot dials. Have to organize better the wiring. Big soundstage and dynamic. I’ see how it compares with my ba3 LS. Cd transport 47 Lab Shigaraki, dac Twisted Pear Audio B3 SE, Pass xa25 and F4 amplifiers. Spatial Audio M4’s TM and diy pair of Ripole subwoofers.
Attachments
If I set T7 and T8 to 10Vdc and input a 1Khz sine wave at 366mVac this is what I get at the outputs:
Right = 2.70 Vac
Left = 2.74 Vac
That's a gain of ~17dB
Hy guys,
I started only today to assemble the kit received in September. After soldering a few components, I saw that the JFETs Q2 set consists of three J113s and one J112 ... is this normal?
Sorry for the "stupid" question but I'm just a decent assembler and mechanic, I know how to hold a soldering iron in my hand and I remember something electronic from school, nothing more but I have a great passion that you all have transmitted to me through this forum.
Many thanks,
Mauro
I started only today to assemble the kit received in September. After soldering a few components, I saw that the JFETs Q2 set consists of three J113s and one J112 ... is this normal?
Sorry for the "stupid" question but I'm just a decent assembler and mechanic, I know how to hold a soldering iron in my hand and I remember something electronic from school, nothing more but I have a great passion that you all have transmitted to me through this forum.
Many thanks,
Mauro
If I understand correctly, according to a previous post (see post 2205 and the related 2206), sometimes J112's get swept into certain piles of J113's by accident. If you were able to test the J112 to see if it falls into the same Idss range as your J113s you could use it, but if not, email Nelson and he would send you replacements.
Korg NuTube preamp board left channel issues
I just completed the B1 with Korg NuTube preamp board (not the complete kit). I installed it in a chassis with a ClassDaudio CDA-120 Class D 2 channel amplifier. I had incorrect connected the + output on the left channel to the - input of the power amp. The left channel doesn't work. I checked for signal with a scope and it seems the Korg Nutube output on that channel is missing or low. Wouldn't the buffer output FET's protect the Korg? Is it more likely for the FET to blow than the Korg? I'm going to check my soldering and all voltage levels tonite maybe its a construction issue.
I just completed the B1 with Korg NuTube preamp board (not the complete kit). I installed it in a chassis with a ClassDaudio CDA-120 Class D 2 channel amplifier. I had incorrect connected the + output on the left channel to the - input of the power amp. The left channel doesn't work. I checked for signal with a scope and it seems the Korg Nutube output on that channel is missing or low. Wouldn't the buffer output FET's protect the Korg? Is it more likely for the FET to blow than the Korg? I'm going to check my soldering and all voltage levels tonite maybe its a construction issue.
Many thanks Steve,
yes you understood correctly ... sorry but I use google translator ...
After your reply and after reading the posts indicated to me, now I feel more relaxed.
The next step will be to test the JFETs, I have to do it.
yes you understood correctly ... sorry but I use google translator ...
After your reply and after reading the posts indicated to me, now I feel more relaxed.
The next step will be to test the JFETs, I have to do it.
Do I understand the situation correctly...the channels started off in balance (on first use) and then the one channel became weaker over time?
Well, now that it has been like two weeks, I can't say exactly how the channel balance was upon first use, what I recall the most was the imaging wasn't as good as my current preamp. Clearly channel balance can affect that, so yes, it probably never worked right from first use. I do remember listening to White Stripes on the second day and wondering why Jack and his guitar were sitting just inside of the left channel instead of exactly center lol! Still sounded good 😛 The very first thing I listened to was Pink Panther and I didn't notice the imbalance, just that it wasn't imaging properly.
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That thing has a poop load of gain (~26db). So if you put 1mV input to the Korg B1 (gain of 15.3dB right and 16dB left) by the time it gets through the amp to the speaker binding posts there will be about 1V difference between the channels (11.6 right and 12.6 left). Someone please correct me if i'm wrong (my math skills aren't that sharp). Makes sense you're hearing Jack and guitar to the left of center.
I know this isn't helping resolve the issue, just helping me get my head around it. That's about all the help I can give right now...my preamp is at the machine shop with all the guts still inside it
I ordered some new heater resistors (510 ohm) just to bring the heater voltage closer to spec, I had to order other parts anyway, we'll see what happens. Yes, that math sounds like what I am hearing.
What are you making for your B1K case Kevin? Machine shop works sounds exciting if it means custom work 😉
What are you making for your B1K case Kevin? Machine shop works sounds exciting if it means custom work 😉
It's not all that exciting. It's just a Galaxy chassis from the store. I suck at metal work and I have a friend with a small machine shop behind his house. He cuts hole for the rca's, power entry, attenuators/selector...nothing too fancy. I'll be posting pictures.
Did you ever test your JFETs for IDSS?