B1 Buffer Preamp

[Melon Head]

I am learning LT Spice at the moment.
So I decided to a spice model of the B1.
However looking at the distortion profile, their is mainly 3rd Harmonic distortion with no 2nd Harmonic.
This seems a little strange as I didn't see Nelson talk about their being any 3rd Harmonic.
Anywy has anyone else modeled this circuit?

The way I measured it, was with the following parameters (feel free to correct me on anything):
- Voltage input amplitude of +/- 1V (ie 2V p-p)
- Volume setting at 12 O'clock using 25k linear pot
- Load = 47k resistive load
- DC Power = 18V

I am a little unsure of the CD Player spec. Is it 2V rms, 2V amplitude, or 2V p-p?

Anway have a look at the attachment.

PS This is an awesome tool for understanding circuits.

[Melon Head]

Sorry about the attachment. I'll have to shrink the file size down.

[folkeb]

I've just finished my cardboard box version of the B1, using NP's DIY board. I have mostly used standard components with the exception of my favorite film caps - obbligato. The 10uF are rather large so it doesn't look as neat as the original does, but who cares about looks! The only pot I had laying around was a 50k alps, but I understand that some prefer lower values. I know that my DAC sounds better with 10k than 50k in my aleph P (SE version with 10k on the input).

So far the sound is impressive, and I am not certain if I want to reconnect my aleph P. Now I need to improve the PSU...I've just done it real simple - a 22000uF after the rectifier brigde.

Thank you mr. Pass yet again!

[Salas]

Originally posted by thanh1973
I am learning LT Spice at the moment.
So I decided to a spice model of the B1.
However looking at the distortion profile, their is mainly 3rd Harmonic distortion with no 2nd Harmonic.
This seems a little strange as I didn't see Nelson talk about their being any 3rd Harmonic.
Anywy has anyone else modeled this circuit?

The way I measured it, was with the following parameters (feel free to correct me on anything):
- Voltage input amplitude of +/- 1V (ie 2V p-p)
- Volume setting at 12 O'clock using 25k linear pot
- Load = 47k resistive load
- DC Power = 18V

I am a little unsure of the CD Player spec. Is it 2V rms, 2V amplitude, or 2V p-p?

Anway have a look at the attachment.

PS This is an awesome tool for understanding circuits.

I did run some actual FFT through B1 when I made mine and the even order was dominating odd order in all orders. It also distorted the less, the more I turned the volume clockwise.

CD is about 6V P-P.

[labjr]

Originally posted by folkeb
I've just finished my cardboard box version of the B1, using NP's DIY board. I have mostly used standard components with the exception of my favorite film caps - obbligato. The 10uF are rather large so it doesn't look as neat as the original does, but who cares about looks! The only pot I had laying around was a 50k alps, but I understand that some prefer lower values. I know that my DAC sounds better with 10k than 50k in my aleph P (SE version with 10k on the input).

So far the sound is impressive, and I am not certain if I want to reconnect my aleph P. Now I need to improve the PSU...I've just done it real simple - a 22000uF after the rectifier brigde.

Thank you mr. Pass yet again!

Are there any B1 boards currently available? Or maybe you made your own?

[Melon Head]

Thanks for that Salas.

Did you use LTSpice to do your FFT measurents, or were they real measurements performed with a distortion analyzer?

Anyway here is the attachment.

[jameshillj]

Don't forget that the final SOUND depends a lot on those Series Signal capacitors AND the power supply. [don't skimp this].

[AndrewT]

Originally posted by salas


I did run some actual FFT through B1 when I made mine and the even order was dominating odd order in all orders. It also distorted the less, the more I turned the volume clockwise.

CD is about 6V P-P.

yes.
Upto 2.2Vac = 3.1Vpk = 6.2Vpp

[Salas]

Originally posted by thanh1973
Thanks for that Salas.

Did you use LTSpice to do your FFT measurents, or were they real measurements performed with a distortion analyzer?

Anyway here is the attachment.

Real.

[Melon Head]

Do you have any idea what I might be doing wrong?
Or is this a common problem with simulators?