Interesting thought....I'll have to try it the other way around ... the iron pre driven by the B1K... just because
Hello to everyone and a special thanks to @ClaudeG for the many posts regarding capacitor values in the Nutube preamp.
That said, I want to replace the existing six (3 per channel) 10uf capacitors in the Korg Nutube Preamp according to the ClaudeG references (yes, I did use the Search Function!). I would do 0.22uf for the first one, 1.0uf for the second, however, I'm hoping for guidance on the third one.
For ease of capacitor placement on the PCB, I'd like to use a smaller physical size (and lower value uf) for this 3rd capacitor. According to the Digikey calculator a 0.22uf capacitor gives a 9.6Hz cutoff frequency. I have a Threshold Cas 2 amp with 75,000 Ohms input impedance. I can only assume that the .22uf value is appropriate in this scenario to maintain sound quality. I'm guessing here that frequencies below 9.6Hz would not be passed from the preamp to the amp but all frequencies above 9.6Hz are passed on, is this correct?
I've attached an image from the Digikey site for calculating cutoff frequency. I'm new to the technical side of the audio world so please forgive any obvious errors or incorrect references. Thanks in advance for any help.
That said, I want to replace the existing six (3 per channel) 10uf capacitors in the Korg Nutube Preamp according to the ClaudeG references (yes, I did use the Search Function!). I would do 0.22uf for the first one, 1.0uf for the second, however, I'm hoping for guidance on the third one.
For ease of capacitor placement on the PCB, I'd like to use a smaller physical size (and lower value uf) for this 3rd capacitor. According to the Digikey calculator a 0.22uf capacitor gives a 9.6Hz cutoff frequency. I have a Threshold Cas 2 amp with 75,000 Ohms input impedance. I can only assume that the .22uf value is appropriate in this scenario to maintain sound quality. I'm guessing here that frequencies below 9.6Hz would not be passed from the preamp to the amp but all frequencies above 9.6Hz are passed on, is this correct?
I've attached an image from the Digikey site for calculating cutoff frequency. I'm new to the technical side of the audio world so please forgive any obvious errors or incorrect references. Thanks in advance for any help.
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Your use of the low pass filter is incorrect. Only frequencies below the cutoff are present. You want to use the high pass filter.
Also the capacitor is working inconjunction with the 33.2k resistor at the B1 Korg output.
Also the capacitor is working inconjunction with the 33.2k resistor at the B1 Korg output.
Hi Silver Sawder,
Thank YOU for your kind post 🙂
The third cap value forms, in conjunction with the input impedance of the following stage -your power amp - a high pass filter.
To determine how small and non expensive that cap can be, you have to know the input impedance of your power amp. It can realisticaly nowadays be anything between say 10k (worst case for yoru cap) and 100k. I assumed "this" worst case when I went for my 3rd cap, to make sure my B1K would be compatible with anything non to exotic etc.
Now if you stick to your Threshold Cas 2 amp with 75,000 Ohms input impedance, and you want to aim for say Fc = 5Hz. I recommand that value because sadly these filters are not "Go or no go", but more complex in their frequency response... and also with their important phase response. Many to read on the internet, first order RC high pass filter are your key words, response in frequency and phase...
Now assuming all that I believe you could go for 0.4uF or higher for your thrid cap. That should be reasonable. Of course, if you have LS that don't produce any low bass frequencies you could perhaps seek for lower values but I would just stick to 0.5uF or so depending on what fits all your needs.
I hope this helps
Claude
Addition: yes, there is that 221K resistor at the output in parallel etc., but let's ignore that... itdoesn't change the world... eg it shifts Fc to 5.6Hz with 0.5uF... so just take 0.5uF or higher, whatever convenient to you...
Thank YOU for your kind post 🙂
The third cap value forms, in conjunction with the input impedance of the following stage -your power amp - a high pass filter.
To determine how small and non expensive that cap can be, you have to know the input impedance of your power amp. It can realisticaly nowadays be anything between say 10k (worst case for yoru cap) and 100k. I assumed "this" worst case when I went for my 3rd cap, to make sure my B1K would be compatible with anything non to exotic etc.
Now if you stick to your Threshold Cas 2 amp with 75,000 Ohms input impedance, and you want to aim for say Fc = 5Hz. I recommand that value because sadly these filters are not "Go or no go", but more complex in their frequency response... and also with their important phase response. Many to read on the internet, first order RC high pass filter are your key words, response in frequency and phase...
Now assuming all that I believe you could go for 0.4uF or higher for your thrid cap. That should be reasonable. Of course, if you have LS that don't produce any low bass frequencies you could perhaps seek for lower values but I would just stick to 0.5uF or so depending on what fits all your needs.
I hope this helps
Claude
Addition: yes, there is that 221K resistor at the output in parallel etc., but let's ignore that... itdoesn't change the world... eg it shifts Fc to 5.6Hz with 0.5uF... so just take 0.5uF or higher, whatever convenient to you...
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@ClaudeG, sorry, you posted as I was typing up my reply to Ben Mah. I changed the values: (33,2Kohm resistor in Nutube Preamp) + (75Kohm input impedance of Amp) = 108,200 Ohms. Please see attached image for the new calculation. It seems 0.33uf Cap achieves the Fc=5Hz (I do acknowledge your 0.5uf recommendation but I'm trying to understand the process). Unless I am not supposed to be adding the resistor value in the preamp to the equation??
My connections from Nutube preamp outs are as follows: right channel has Y-splitter cable feeding Threshold Amp and SVS 3000 Micro subwoofer AND left channel Y-splitter has same amp and woofer.
My connections from Nutube preamp outs are as follows: right channel has Y-splitter cable feeding Threshold Amp and SVS 3000 Micro subwoofer AND left channel Y-splitter has same amp and woofer.
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Err, where does that 33.2K resistor come from? What refrence on the schematic? It has been years I didn't look into that...
The 221k I mentioned is in parallel to your 75k input impedance, you may want to look into equivalent resistor value when 2 resistors are in parallel... if really willing to dig into all that
Off to bed, will come back if needed next eve, but sure enough others will shime in with more details meanwhile!
Good luck!
Claude
The 221k I mentioned is in parallel to your 75k input impedance, you may want to look into equivalent resistor value when 2 resistors are in parallel... if really willing to dig into all that
Off to bed, will come back if needed next eve, but sure enough others will shime in with more details meanwhile!
Good luck!
Claude
Err, if you put other devices in parallel to the B1K output you need to know their input impedance and work out the equivalent impedance load seen by the B1K! See post above for 2 R in parallel... you will then need more than 0.5uF caps as the impedance will be reduced whatever...
The 33.2k resistor is in parallel with the input impedance of amplifier(s) connected to the B1 org output. Since the 100 Ohm series resistor is a small value relative to the 33.2k and to the input impedance of the amplifier(s) you can ignore the 100 Ohm resistor when you calculate the net impedance for use in the high pass frequency calculation.
Paralleled resistance calculation R = (1/R1 + 1/R2 + .......)^1
https://www.wikihow.com/Calculate-Series-and-Parallel-Resistance
OK, thanks to Ben Mah (hello!) I realised it is the store kit with the 33.2k output indeed. Sorry, there were many schematics around the B1K...
So at the output you have 33.2k in parallel to 75k in parallel to 16k (if I am not mistaken on the input impedance of your woofers). Sounds lowish for a woofer RCA input but no time tonight to search further into the specs. That's your's if you fancy. And yes ignore the 100R...
Bottom line, your cap at the output forms with the equivalent resistor value (these 3 impedances in parallel) of 9.44k a high pass filter.
I am afraid you are in my worst case of 10k impedance and you have to stick to the minimum value I chose for the third cap. That is due to your Y split. Would be pity to seek for higher Fc as you have these subwoofers able to deliver some bass.
'night all
Claude
So at the output you have 33.2k in parallel to 75k in parallel to 16k (if I am not mistaken on the input impedance of your woofers). Sounds lowish for a woofer RCA input but no time tonight to search further into the specs. That's your's if you fancy. And yes ignore the 100R...
Bottom line, your cap at the output forms with the equivalent resistor value (these 3 impedances in parallel) of 9.44k a high pass filter.
I am afraid you are in my worst case of 10k impedance and you have to stick to the minimum value I chose for the third cap. That is due to your Y split. Would be pity to seek for higher Fc as you have these subwoofers able to deliver some bass.
'night all
Claude
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@Ben Mah, @ClaudeG, thank you for helping me understand. Yes, back to the minimum value recommended. You're much faster to arrive at these conclusions and post them but I'll attach the calculations and my (slow to articulate) thoughts below to maybe help someone in the future.
After typing out my preamp>amp connections I did realize I need to account for the input impedance of the SVS sub amp as well as the Threshold power amp. So: SVS Sub Amp = 16Kohm & Threshold Amp = 75Kohm & Nutube Preamp resistor = 33.2Kohm in parallel. Digikey calculations and a schematic of the preamp for reference.
Based on the new insights and size and price I'm right back at ClaudeG's original suggestion to use 3.3uf caps in the 3rd spot. OMG. My apologies for any waste of time. I really am trying to do these things on my own but I have a lot to learn and many hours of research before I'll be able to connect all the dots.
After typing out my preamp>amp connections I did realize I need to account for the input impedance of the SVS sub amp as well as the Threshold power amp. So: SVS Sub Amp = 16Kohm & Threshold Amp = 75Kohm & Nutube Preamp resistor = 33.2Kohm in parallel. Digikey calculations and a schematic of the preamp for reference.
Based on the new insights and size and price I'm right back at ClaudeG's original suggestion to use 3.3uf caps in the 3rd spot. OMG. My apologies for any waste of time. I really am trying to do these things on my own but I have a lot to learn and many hours of research before I'll be able to connect all the dots.
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A question about Power supply capacitors. I have always just followed a BoM and I now have a stock pile of spare parts.
I noticed the power supply says 1000uf plus, how much plus can I use? I have several 2200uf, 3000uf, and 4000uf from a previous project, can I freely use these? In all the 1000uf spots or just the power supply?
Thanks,
Brian
I noticed the power supply says 1000uf plus, how much plus can I use? I have several 2200uf, 3000uf, and 4000uf from a previous project, can I freely use these? In all the 1000uf spots or just the power supply?
Thanks,
Brian
@ellingboe, I am no authority but please see the two links below.
Post #4942 by 6L6
Post #5742 by ClaudeG
Post #4942 by 6L6
Post #5742 by ClaudeG