B1 builders thread

[wintermute]

Hi Gaetan, note that I have no idea what I'm doing but try increasing R9 to 20K and R10 to 5.6K I think you should see a big improvement in your distortion

Note I modified the circuit on the B1 side to be closer to the original, but that had very little effect (if any) on the distortion, so I turned to the gain stage. That dropped the THD from 0.17% to 0.05%

Attached is from your original circuit with only the two mentioned resistors changed.

fourier output for modification below:

Fourier components of V(out)
DC component:-0.00144491

Harmonic Frequency Fourier Normalized Phase Normalized
Number [Hz] Component Component [degree] Phase [deg]
1 1.000e+03 3.428e+00 1.000e+00 179.76° 0.00°
2 2.000e+03 1.740e-03 5.076e-04 77.96° -101.80°
3 3.000e+03 1.565e-04 4.567e-05 -145.84° -325.60°
4 4.000e+03 1.255e-05 3.660e-06 -124.45° -304.21°
5 5.000e+03 1.556e-06 4.539e-07 50.03° -129.73°
6 6.000e+03 1.332e-07 3.884e-08 44.86° -134.90°
7 7.000e+03 4.876e-08 1.422e-08 -153.42° -333.18°
8 8.000e+03 3.334e-08 9.726e-09 177.73° -2.04°
9 9.000e+03 2.812e-08 8.203e-09 171.55° -8.21°
Total Harmonic Distortion: 0.050964%


Date: Fri Feb 08 23:31:43 2013

fourier output for unmodified output below:

Fourier components of V(out)
DC component:-0.00535448

Harmonic Frequency Fourier Normalized Phase Normalized
Number [Hz] Component Component [degree] Phase [deg]
1 1.000e+03 3.299e+00 1.000e+00 179.97° 0.00°
2 2.000e+03 5.639e-03 1.709e-03 89.41° -90.56°
3 3.000e+03 4.213e-04 1.277e-04 -178.57° -358.54°
4 4.000e+03 3.495e-05 1.059e-05 -91.62° -271.59°
5 5.000e+03 3.108e-06 9.421e-07 2.08° -177.89°
6 6.000e+03 3.431e-07 1.040e-07 110.15° -69.82°
7 7.000e+03 1.465e-07 4.439e-08 -177.64° -357.61°
8 8.000e+03 1.041e-07 3.155e-08 -179.89° -359.85°
9 9.000e+03 8.890e-08 2.694e-08 176.92° -3.05°
Total Harmonic Distortion: 0.171381%


Tony.

[gaetan8888]

Hello wintermute

I'm surprise, I have simulated your suggestion and despite that the input Jfet do receive only 669 micro amp of DS current, the thd are lower !!

Any explanation about it ?

Thank you

Bye

Gaetan

[wintermute]

Hi Gaetan, As I said I have no Idea what I am doing, so any explanation will be speculation on my part... I tried isolating the gain stage from the buffer stage, in case it was an interaction between the two cricuits but it didn't change things, so it appears that the distortion is directly related to the amount of current flowing through the fet (I also simmed with 10K and 2.8K first and it was higher in distortion).
Although the gain stage is about as simple as it gets, I unfortunately do not really know enough to say how and why things affect the distortion, I just had a hunch that increasing the resistance may help.

Tony.

[richluvsound]

Can anyone help me wire this to my BI please ? thank you , Rich

44D30-01-2-AJN Grayhill Inc | GH4402-ND | DigiKey

[bassnkeys]

Purpose? As a source selector? Output selector? As a wild and crazy volume?

[richluvsound]

Cheers Bass ,

I want to use it for input selector ..... 3 inputs ?

numbers 1 to 12 on the back .... how do I figure out which is + and - ?

I guess the pins closer to the chassis are the output to L1 and R1 ?

thank you , Rich

[bassnkeys]

I would start by planning to insert it in place of the input 2 on the B1 board... I'm assuming you're using Pass boards. I find that the signal path traces for the input 2 are a tiny bit more direct... probably makes no difference but...
Of course you could still use the board supplied traces for two inputs and using your switch and another single switch wind up with 4 total. Tie the grounds (all the inputs on the board share the common ground) and use the switch to select 1 of 3 pair hot leads!
30°f and dark in Minnesota

[6L6]

You will have to use your DMM and ring out the connections in the various switch positions to determine which pins are the switched inputs and which are the outputs. Once you have that done, then connect via this sketch -

[richluvsound]

I think I have a problem with the selector .... can't get any continuity with the DMM .

Can I use this instead ? 7203L1YZQE C&K Components | CKN1150-ND | DigiKey

I need only 2 inputs for DAC and Phono .

Rich

[Marra]

That will do nicely Rich its how I did my DCB1.Don't forget to cross over the wires so to speak so that the input corresponds to the switch position.
There is also a nice one from Farnell

5646A9 - APEM - SWITCH, DPDT | Farnell United Kingdom