So just to be clear - the schematic has the error, but the PCB has it right. So no correction needed? 😱
I built mine off the PCB screen print values as it all looked OK (I ignored the schematic/s)
I's an easy build really, populate the PS and check voltages at TP's prior to populating the rest of the board and set up... worked first time and sounds superb.
As always NP has a great article at his First Watt site which outlines why and how in plain english.🙂
It may be a good match for M2X?
The Korg pre needs a power amp with some gain and a power amp which is not very dominant 2nd harmonic.
For MoFo and ACA I will use BA3-pre.
The Korg pre needs a power amp with some gain and a power amp which is not very dominant 2nd harmonic.
For MoFo and ACA I will use BA3-pre.
Waiting for DIY store to get PCB kit together for sale. Got chassis ready. Got NuTube.Wired inputs to volume pot, have separate external potentiometer to use for tube bias pots. Prepared PCB alter. Have poly caps for signal path. May change volume pot to better precision later if I can get this to circuit to work.
Figured out how to use oscilloscope to measure power supply. It's spec'd at 5mV Ripple. My little handheld osci goes down to (lowest) 5mv per division and measured 24 V DC perfect, AC at 1mV, which is better than spec.
Question is if the power supply vibrates too much or radiates noxious fields to PCB when mounted. Have silicon gel under PS and a piece to put under PCB when done with loose screw mounts.
Again, this is my first DIY project, so if it succeeds, it will be cool. If not, I guess I can just keep chipping away at it.
I have ordered the passive components but don't know yet which project is first in the pipeline.....Whammy, Korg, MX2 (including universal 2 x 25 V PSUs). I also need to measure BA3-pre and adjust distortion using the ARTA software. Probably BA3-pre is first to finish this project.
Looks like you're off to a great start.
Pete Millet's Nutube buffer was my first project last year and I will never forget the thrill of plugging it in, seeing it glow and hearing sound coming out.
Good luck with the rest of the build.
Pete Millet's Nutube buffer was my first project last year and I will never forget the thrill of plugging it in, seeing it glow and hearing sound coming out.
Good luck with the rest of the build.
I'm busy bringing a new ACA build online; will be posting on that after I've had a chance to listen to it.
The B1 Korg is going to be an interesting build. I'm tempted to couple it with one of my ACAs as a two-box integrated amp, with the main power coming from the ACA before being filtered by the B1.
The B1 Korg is going to be an interesting build. I'm tempted to couple it with one of my ACAs as a two-box integrated amp, with the main power coming from the ACA before being filtered by the B1.
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I just finished testing a Salas BiB v1.1 regualtor to use with my Korg build. I picked up a 24v 2A linear plug-in transformer from Jameco a short while ago that puts out 31v unloaded and about 28.5v loaded with the regulator set to 400mA of current delivery. I'll start soldering parts in the Korg PCB tonight. It will have to live for a little while without a chassis...
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Because I didn't have that specific power resistor laying around 😉 Right now I'm in "make it work with parts on hand" mode...
no use of burning more than twice load's current in shunt part of reg
more is just useless heat**
and ..... that's speaking World's Greatest Proponent of shunt regs ...... 🙂
**at least when we are dealing with A class load ...... (why even bother with something not being A class , in first place
)
more is just useless heat**
and ..... that's speaking World's Greatest Proponent of shunt regs ...... 🙂
**at least when we are dealing with A class load ...... (why even bother with something not being A class , in first place
)
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Yep, once it's working, it'll get a more permanent home and I'll dial things down a bit. For now, I just wanted to make it work. No sense making *ALL* of the little black boxes space heaters.
Nice work, it's shaping up really well. Is that a Galaxy case?
Can I ask a newb question?
What are the resistors for between live and ground on the RCA inputs?
Can I ask a newb question?
What are the resistors for between live and ground on the RCA inputs?
Is this likely to be too much of a good thing to be a decent match to the 1.6 ACA?
Thanks,
Ken
Thanks,
Ken
Thanks! Yes, the case is a Galaxy 2U with steel covers. The 1 meg resistors on the RCA jacks are to reduce clicks, pops and thumps when switching inputs.
I'm extremely happy with this preamp and it mates very well with my M2x. No rough edges but plenty of extension at both ends of the spectrum with excellent definition and imaging. Oh, and reversing speaker polarity did make a slight improvement on soundstage depth. Thank you Nelson!
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Nice work, WKCox!
I have a working Nutube and PSU now. Still trying to decide what kind of a nice volume pot to use and what type of a case to put it in.
The regulator is a Salas BiB v1.1 biased to about 200mA. After letting it warm up a little and adjusting it to 24.00v, I get the following measurements on the board:
T1=24.00v, T2= 23.3v, T3=22.63v, T4=9.67v, T5=0.704v, T6=0.706v, and T7 & T8 are presently adjusted to 10.0v. It looks like T4, T5, and T6 are reading a bit high.
The CRCRC are 2200uF and the remaining ones are 1,000uF. The signal resistors leading to the first jFet buffer are 620R tantalum left over from a previous project and the signal resistors from the NuTube into the second jFet buffer are 1k tantalum.
Haven't had the chance to listen to anything yet...
I have a working Nutube and PSU now. Still trying to decide what kind of a nice volume pot to use and what type of a case to put it in.
The regulator is a Salas BiB v1.1 biased to about 200mA. After letting it warm up a little and adjusting it to 24.00v, I get the following measurements on the board:
T1=24.00v, T2= 23.3v, T3=22.63v, T4=9.67v, T5=0.704v, T6=0.706v, and T7 & T8 are presently adjusted to 10.0v. It looks like T4, T5, and T6 are reading a bit high.
The CRCRC are 2200uF and the remaining ones are 1,000uF. The signal resistors leading to the first jFet buffer are 620R tantalum left over from a previous project and the signal resistors from the NuTube into the second jFet buffer are 1k tantalum.
Haven't had the chance to listen to anything yet...
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