Oh, good, a rumble filter!
Thank you for the response.
Also, since my power supply is an already rectified, regulated and filtered transformer based linear power supply, can smaller caps be used in the series caps aka 330 be subbed for the 2200/1000 in the power supply section only?
I assume the more aggressive filtration assumed the SMPS wall wart source?
Last edited:
My board and Nutube package has arrived today.
Many thanks to Nelson Pass, bk856er and Soundhappy.
Ditto, my board/NuTube package also arrived today and my board components arrived from Mouser today as well. Vishay/Dale resistors and Elna silk coupling caps. Mucho gracias to all and ready to drill chassis and stuff board tomorrow!
To preserve the good sleep of the good DIY’er he or she can always parallel the 10uF with some 100nF - 1uF plastic capacitor on the PCB solder side.
I started my “career” by doing so on my venerable Hafler DH-101 in the old days.
I watched You Tube video on measuring PS ripple. I have a small handheld oscilloscope (haven't much learned how to use it yet), so I can put large resistor on the PS output, turn it on, then measure the output for amount of AC. If it is large, then larger caps. If it is very small, then smaller caps OK for the basic PS filter part I would assume. I think I can muddle through that.
What ripple goal for 24V DC in a linear power supply in Korg B1?
Although I have never put anything together yet, I have a box full of stuff from teardowns that I accumulated from audio elephant graveyard, including a bunch of perfect looking 330 microfarad electrolytic caps. Voltmeter has measured them at spec. Also, guts of B1 that I bought have a couple of larger caps when it arrives.
I guess some of the signal path caps are du jour, to prevent DC in the signal path, with bottom frequency response rolled with lower values as stated.
Hmm. already doing the junk drawer thing with it and haven't even got it yet.
The filter consisting of two cascaded RC networks of 10 ohms and 1000 uF
attenuates about 36 dB at 120 Hz and and about -76 dB at 1 KHz.
The rejection of the Nutube added to this is about 6 dB.
I measure about 1.6 mV (rms, wide band) coming out of the specified supply,
so assuming worst case of 120 Hz, we would expect around 10 uV noise at the
output of the Nutube. YMMV.
attenuates about 36 dB at 120 Hz and and about -76 dB at 1 KHz.
The rejection of the Nutube added to this is about 6 dB.
I measure about 1.6 mV (rms, wide band) coming out of the specified supply,
so assuming worst case of 120 Hz, we would expect around 10 uV noise at the
output of the Nutube. YMMV.
Pass DIY Addict
Joined 2000
Paid Member
If I build two Korg's to have a real dual mono setup like I have with BA3-pre using two external PSU's would it be possible to try out bridged mode of the Korg?
I guess it could be configured like the ACA's in bridge mode?
The other thing…...would it make sense?
To me it could make sense having higher output with a little less 2. harmonic distortion. Then I could try using the Korg's with MoFo's. I know that the signature of the Korg is 2nd harmonic so my goal is not to change that….just "adapt" it a bit...
I guess it could be configured like the ACA's in bridge mode?
The other thing…...would it make sense?
To me it could make sense having higher output with a little less 2. harmonic distortion. Then I could try using the Korg's with MoFo's. I know that the signature of the Korg is 2nd harmonic so my goal is not to change that….just "adapt" it a bit...
So in my power supply query, I guess looking at online calculators, 1000 micro farad caps have a 10db rejection advantage over 330 micro farad caps.
If the linear, rectified, voltage regulated power supply has already a 10 db ripple noise advantage over the customary SMPS wall wart, which doesn't seem an unreasonable expectation, then the general effect of 330 micro farad power supply filter should be similar.
I guess I will use my little hand held oscilloscope to attempt a ripple measurement of the power supply when I get it.
Otherwise, 2.5 microfarad bypassed input caps, polypro 10 microfarad signal path caps. 25K potentiometer at first, but will get an alps later.
I think I will route the 10K adjustable pots to external knobs on the chassis. That way I can use headphone adaptor and headphones on the output to adjust and listen by ear (if the output is sufficient for sensitive headphones about 80 ohms), since I have no harmonics or distortion analyzer.
With my lousy soldering skills, it will probably look strange and fugly, but maybe it will work.
If the linear, rectified, voltage regulated power supply has already a 10 db ripple noise advantage over the customary SMPS wall wart, which doesn't seem an unreasonable expectation, then the general effect of 330 micro farad power supply filter should be similar.
I guess I will use my little hand held oscilloscope to attempt a ripple measurement of the power supply when I get it.
Otherwise, 2.5 microfarad bypassed input caps, polypro 10 microfarad signal path caps. 25K potentiometer at first, but will get an alps later.
I think I will route the 10K adjustable pots to external knobs on the chassis. That way I can use headphone adaptor and headphones on the output to adjust and listen by ear (if the output is sufficient for sensitive headphones about 80 ohms), since I have no harmonics or distortion analyzer.
With my lousy soldering skills, it will probably look strange and fugly, but maybe it will work.
Last edited:
Quick update for Europe Christmas group click here
Boards arrived today, eventually. Shipping starts tomorrow...
Boards arrived today, eventually. Shipping starts tomorrow...