Beautiful build, Allvey!
I have a suggestion if I may. I see that you have male connectors for power out. For safety reasons and also to prevent accidental shorting of the power supply, female connectors would be my choice (and perhaps a electrical code requirement).
NAC3FPX-WOT-TOP | Neutrik
A male connector would be used at the preamp end to receive the live end of the power cable, which would also have a female connector.
that's your call
Like this: (it's an ugly markup I know especially since the grounding at the input jack is not addressed correctly)
As for the gentleman that previously suggested separate boxes, if wired as shown, a DPDT could be added as an active passive solution in the same box.
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R1 resistors and green led question
I gather that the 4 - 221R resistors I got are R1?
And what is the green LED for.
I gather that the 4 - 221R resistors I got are R1?
And what is the green LED for.
here's a quote from earlier in the thread:
"Thanks to Zen Mod, I realized that these 3 caps act as part of a high pass filter, meaning in practice that altering their value would affect the band pass in the bass. The smaller the cap, the higher the high pass cut frequency."
Can the input cap go away leaving only the RC coupling at the output? If so, what is the appropriate value?
"Thanks to Zen Mod, I realized that these 3 caps act as part of a high pass filter, meaning in practice that altering their value would affect the band pass in the bass. The smaller the cap, the higher the high pass cut frequency."
Can the input cap go away leaving only the RC coupling at the output? If so, what is the appropriate value?
yup, that would be OK
F=1/(2 x Pi x R x C) , where R is Rin of stage (roughly 33K2) and C is size of coupling cap , which you need because input grid is on pos. voltage potential
for F shoot for no more than few Hz
Hmmm....
If my algebra (arithmetic) is correct:
- 10uF produces a cutoff ~.5Hz
- 1uF produces a cutoff ~5Hz
- 2uF produces a cutoff ~2.4Hz
Looks like anything 1uF or above given the fixed R value is likely good. (Which is what NP said in his writeup anyway...)
And for clarity, the input cap IS required?
If my algebra (arithmetic) is correct:
- 10uF produces a cutoff ~.5Hz
- 1uF produces a cutoff ~5Hz
- 2uF produces a cutoff ~2.4Hz
Looks like anything 1uF or above given the fixed R value is likely good. (Which is what NP said in his writeup anyway...)
And for clarity, the input cap IS required?
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Yes the resistors you received in the kit are for R1. Green LED??? not in this build.
Well I tried another round of voltage testing trying to narrow down the problem in my channel imbalance. I previously thought A1 and A2 on the Nutube had identical output voltage (AC) but today I see that A2 exhibits the voltage drop that I am seeing on the board output. I still am seeing identical input voltages, so the problem is maybe the heater section? T5 and T6? T5 (L) is .683v while the quieter channel T6 (R) is .692v. Would the higher voltage heater cause less output voltage?? That can't be....
I would change the 475ohm resistors to maybe 510 to bring the heaters closer to .6 but I only have 560s in my collection. I will order some if you think it makes a difference.
I would change the 475ohm resistors to maybe 510 to bring the heaters closer to .6 but I only have 560s in my collection. I will order some if you think it makes a difference.
Hi Steve,
So I went back and read your previous posts. The channel imbalance is audible, correct?
Would you hazard a guess as to how many dB the one channel is down from the other when you're listening?
So I went back and read your previous posts. The channel imbalance is audible, correct?
Would you hazard a guess as to how many dB the one channel is down from the other when you're listening?
Hey Kevin - yes, definitely audible, center images are now more than half way to the left of center.....but probably 1-2db at the most. Measured at T8 or board output, when T7 is 1v T8 is .95V. When T7 is 12mV, T8 is 11mV. This is on a steady 50hz sine wave test tone. No amp connected.
Your volume potentiometer is stereo ? Maybe both channels resistances are the same, little or more different ?
In 9, 12 and 3 o clock positions..
In 9, 12 and 3 o clock positions..
Resistance measurements between channels:
9: L 333.5 R 331.5
12: L 4.71k R 4.63k
3: L 12.78k R 12.60k
Running 1Khz sine wave about 12 o'clock
Input on board: L 30.8mV R 30.8mV
T7/T8: L 205.2mV R 188.1mV
9: L 333.5 R 331.5
12: L 4.71k R 4.63k
3: L 12.78k R 12.60k
Running 1Khz sine wave about 12 o'clock
Input on board: L 30.8mV R 30.8mV
T7/T8: L 205.2mV R 188.1mV
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Volume measurements should be resistance measurements...oops lol.
Those are ohms between L output, R output and Ground
Why does the resistance get higher when I turn the volume up? Voltage goes up.....
Alps volume pot is weird to me....at really low volumes its low resistance then goes higher, its highest resistance is half way then goes back down to almost wide open at highest volume.
Those are ohms between L output, R output and Ground
Why does the resistance get higher when I turn the volume up? Voltage goes up.....
Alps volume pot is weird to me....at really low volumes its low resistance then goes higher, its highest resistance is half way then goes back down to almost wide open at highest volume.
Steve, what are you using as a source? CD player, phone...? Lets get to the point where you have a 1V 1Khz signal coming into the board.
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For these tests a Mac mini -> Audioquest Dragonfly. The channel imbalance is heard on all sources via any input. CD, Phono, Computer.
What voltage does the dragonfly put out running a 1K sine wave? My point is we have to be running the same signal into the board, then we can compare voltages at different points on the board.
edit: Not sure if I'm making sense to you, but I would like to get to the point that we're both running a standard (of our choosing) signal on the inputs of the board...then we can start to make comparisons. I'm going to bed now, but I'd love to work on this with you sometime tomorrow.
edit: Not sure if I'm making sense to you, but I would like to get to the point that we're both running a standard (of our choosing) signal on the inputs of the board...then we can start to make comparisons. I'm going to bed now, but I'd love to work on this with you sometime tomorrow.
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Thank You for making a suggestion for a further option to be considered.
I am forwarding this suggestion for a DPDT onto the Builder of the Korg B1,
who is making the Modular Version.
Power switches: Anodised Aluminum Switch 2NO2NC 250V 3A O16mm Black - Audiophonics
Chassis and customizations: HIFI2000/Modushop (Modushop by Hi-Fi 2000 | Contenitori per Elettronica | Electronic Enclosures | Hi Fi Chassis)
