Obsolete DIY Audio (Part 2) First Watt B1 Buffer Preamplifier

I continue this topic about what certain do it yourself (DIY) audio that obsolete, means it used to be good but not for today standard.

The First Watt B1 Buffer preamplifier are published around 2008. It is very popular buffer preamplifier among DIY audio at that time and I am the one who also praised it very much. You might probably know the buffer function in audio system, in the First Watt article about this B1, it is explain the function completely by the audio guru, Mr. Nelson Pass. In short, this buffer function is for impedance matching between input and output, from the source to the amplifier.

I always said this is just like a preamplifier but without additional gain. I have made this B1 buffer 3 times in the past and they makes me smile. Mostly I combined this B1 buffer with the Gainclone amplifier. This makes the music more deeper in sound-stage and reveal the details.

For that reason, I will make it again right now.

My initial design for this B1 build is should be small enough that I can hide behind my audio system. I will not put any potentiometer in B1 for volume control for simplicity reason. Then I just using the volume control in the amplifier instead. The challenge with this B1 is require quite high voltage about 18 volt DC power supply. That is why I am now using low noise SMPS from old printer. It is rated 22 volt DC output, then regulated with IC 7818 to get 18 volt fixed output. This SMPS also recommended in First Watt B1 article since the circuit design itself already good at noise rejection.

I am using the universal PCB. It is cut to fit inside this casing perfectly.

The front face plate of the casing will be the mini jack for signal input and output. Recently I like this kind connector instead of RCA because of the simplicity and cheaper.

After all this casing works done, right now I can populate the components to build this B1 buffer.

The first things I put on the PCB is always at the signal input first. This 1uF Capacitor input is the MBM capacitor. As you can see the value marked on the capacitor label is only 0,5uF but when I measured them one by one, I get the value more than 1uF.

All connection is done by point to point wiring using each components leads. The reason for this is because this is the very good way to connect between components. The copper materials on the components are high quality and sometimes they are magnetic free. This method is so much better compares to mediocre PCB build.

Another concern when build this B1 buffer is finding the K170BL JFET transistor that already long gone. I still have few of them from the previous project.

After I assembly one part to another part, I end up with complete B1 circuit. This B1 is very simple and more fun to built in this method. Then comes to anther challenge is choosing the DC filter capacitor.

The B1 buffer datasheet recommend 2 x 15,000uF but with Nelson Pass give a note that you can use as low as 1000uF. So with the limitation of the space inside this tiny casing, I will only using 7 Panasonic FC in parallel, each of them is 22,000uF. So in total they would become 154,000uF. Good enough I think.

I populate them inside this PCB and they are fit enough along with the power supply circuit.

And this how I make this B1 buffer preamplifier in the tiny case.

Recently my audio system is consist of Gainclone LM3886 amplifier and the source is Clarion DRX9255 or HX-D1 or Nakamichi DAC-101.

I was hoping this B1 buffer gives the positive impact to the music like I experienced in the past, but sadly it is not.

I am playing music in my audio system by using or not using this B1 buffer, this end up with no B1 buffer at all.

This B1 buffer just like a bottleneck in my audio system. The vocal is now more forward but the instruments are much attenuate, makes it not reveal the music at its full resolution. It just like strengthen in the vocal side only but throwing all others frequency behind. The music presentation feels boring and less impact to the me as the listener. The other aspect is the treble performance with this B1 buffer seems roll-off very quick but bounce back at very high frequency. This is not very pleasant to hear at all.

I also let the components inside this B1 buffer to break-in for a while, but this B1 still cannot shines my audio system. It cannot reveal the detail and soundstage compares to not using it. So I think I should remove this B1 buffer out from my audio system from now on.

I can make an improvement from this circuit for sure, like using linear power supply, or even a packs of batteries, or even changing the input/output capacitor, but perhaps the improvement will be no beneficial compare to the cost I spend.

Actually there is one post about this obsolete DIY project topic that I want to share for the part 3. But well I guess I make this as the last part. I know this topic might be debatable because maybe some of you experience it differently.

So I end up this part 2, cheers.

Disclaimer: Any statement and photos in this article are not allowed to copy or publish without written permission from the writer. Any injury or loss from following tips in this article is not under writer responsibility.