Nelson Pass - First Watt - B1 Buffer
It's been a really long time since I have had an electronics project to work on. The last few projects were fixing some broken audio equipment shortly after school, before that is was an engineering class, and before that it was probably fixing something around the house with my dad.
I decided it would be fun to build a First Watt B1 Buffer Preamp (http://www.firstwatt.com/b1.html). I was a preamp short after selling my TACT RCS-2.2XP and Benchmark DAC1 HDR earlier this year. And having never owned anything designed by Nelson Pass, I figured it was about time.
The B1 should be perfect for my needs since the amplifier it will be paired with is a Bryston 4B-SST with 29db of gain (1v input sensitivity). And my sources are a Logitech Transporter and PS-Audio GCPH, both of which have plenty of output voltage to drive the Bryston... No need for additional gain at the preamp.
Since it's been so long since I last worked on any electronics projects, the first step was to make sure I had the appropriate tools. And I just like tools.
Soldering Iron (Or Station)
Wire Cutters and Precision Pliers
Knife
Something to Hold Circuit Board While Working
Electrical Meter
1-Channel Oscilloscope
Signal Generator
I could have gotten away with the stuff I already had in the garage, but I have always hated that old radio shack soldering pencil.
After spending far too much time researching. I ended up getting a Hakko FX-100 Curie-Point Soldering Station, if you're not familiar with the curie effect - spend a few min reading about it, its cool (or rather hot) stuff. I also picked up a fluke True RMS meter, mostly because I have always wanted one.
The oscilloscope and signal generator are entirely optional, but they are really nice to have around to be able to confirm things are working as expected. I purchased some inexpensive kits off of Amazon (about $35 for both).
Sourcing parts for the B1 was relatively simple. My suppliers were:
DigiKey
Parts-Express
PartsConnexion
DIYAudioStore
PassDIY
NOTE: DigiKey didn't ship a couple of the parts ordered, but their customer service was great and had the parts to me within 48 hours of being alerted of the mistake. If you order from DigiKey, check your order carefully... More on this further down.
I chose to use "better" parts than FirstWatt chose for the production B1. Some of the "better", or at least more esoteric bits include Kimber RCA jacks, Silver/Gold and OCC Copper hookup wire, Sealed high current toggle switch, Alps Blue Velvet Volume Potentiometer, Cardas solder.
Because of the simple design of this preamp, certain parts such as capacitors and resistors in the signal path have a particularly audible impact on the design... So using quality parts is particularly important. I used all Vishay-Dale Resistors, and a mix of Vishay and Jantzen Metallized Polypropylene Film Capacitors.
I also chose to use a really nice case purchased from DIYAudioStore. This added quite a bit of expense since I also then needed to have the case machined (since i didn't have the appropriate tools). The guys over at American Prototype (http://www.americanprototype.com/) did some great work with quick turnaround time off of nothing more than a sketch on a piece of paper.
Since much of the work in building the B1 is in sourcing good parts, I decided to build 2 at the same time. One to keep and one to share.
Once I had all the parts, assembly was uneventful. Unfortunately, when I plugged them into the wall-wart DC power supplies purchased from DigiKey, disaster struck. The power supplies were labeled center positive, but they were mislabeled. I alerted DigiKey of the issue, they promptly checked their inventory, found there was a labeling issue, and shipped me the correct parts.
While waiting for the correct parts, i dug through the wall-warts in the garage and found a suitable donor part. Hooked up the B1 and... Sounds like the Transistors got fried.
I ordered up 20 more LSK170's in order to have enough stock to match the Idss of the transistors. And a few other parts to build a transistor tester.
Once the transistors were swapped out, I was finally able to install the B1 into my system. Wow, this thing is really good. The system sounds ever slightly better than it did without the B1, which was actually a bit of a surprise, yet does nothing to change the overall character of things.
I decided it would be fun to build a First Watt B1 Buffer Preamp (http://www.firstwatt.com/b1.html). I was a preamp short after selling my TACT RCS-2.2XP and Benchmark DAC1 HDR earlier this year. And having never owned anything designed by Nelson Pass, I figured it was about time.
The B1 should be perfect for my needs since the amplifier it will be paired with is a Bryston 4B-SST with 29db of gain (1v input sensitivity). And my sources are a Logitech Transporter and PS-Audio GCPH, both of which have plenty of output voltage to drive the Bryston... No need for additional gain at the preamp.
Since it's been so long since I last worked on any electronics projects, the first step was to make sure I had the appropriate tools. And I just like tools.
Soldering Iron (Or Station)
Wire Cutters and Precision Pliers
Knife
Something to Hold Circuit Board While Working
Electrical Meter
1-Channel Oscilloscope
Signal Generator
I could have gotten away with the stuff I already had in the garage, but I have always hated that old radio shack soldering pencil.
After spending far too much time researching. I ended up getting a Hakko FX-100 Curie-Point Soldering Station, if you're not familiar with the curie effect - spend a few min reading about it, its cool (or rather hot) stuff. I also picked up a fluke True RMS meter, mostly because I have always wanted one.
The oscilloscope and signal generator are entirely optional, but they are really nice to have around to be able to confirm things are working as expected. I purchased some inexpensive kits off of Amazon (about $35 for both).
Sourcing parts for the B1 was relatively simple. My suppliers were:
DigiKey
Parts-Express
PartsConnexion
DIYAudioStore
PassDIY
NOTE: DigiKey didn't ship a couple of the parts ordered, but their customer service was great and had the parts to me within 48 hours of being alerted of the mistake. If you order from DigiKey, check your order carefully... More on this further down.
I chose to use "better" parts than FirstWatt chose for the production B1. Some of the "better", or at least more esoteric bits include Kimber RCA jacks, Silver/Gold and OCC Copper hookup wire, Sealed high current toggle switch, Alps Blue Velvet Volume Potentiometer, Cardas solder.
Because of the simple design of this preamp, certain parts such as capacitors and resistors in the signal path have a particularly audible impact on the design... So using quality parts is particularly important. I used all Vishay-Dale Resistors, and a mix of Vishay and Jantzen Metallized Polypropylene Film Capacitors.
I also chose to use a really nice case purchased from DIYAudioStore. This added quite a bit of expense since I also then needed to have the case machined (since i didn't have the appropriate tools). The guys over at American Prototype (http://www.americanprototype.com/) did some great work with quick turnaround time off of nothing more than a sketch on a piece of paper.
Since much of the work in building the B1 is in sourcing good parts, I decided to build 2 at the same time. One to keep and one to share.
Once I had all the parts, assembly was uneventful. Unfortunately, when I plugged them into the wall-wart DC power supplies purchased from DigiKey, disaster struck. The power supplies were labeled center positive, but they were mislabeled. I alerted DigiKey of the issue, they promptly checked their inventory, found there was a labeling issue, and shipped me the correct parts.
While waiting for the correct parts, i dug through the wall-warts in the garage and found a suitable donor part. Hooked up the B1 and... Sounds like the Transistors got fried.
I ordered up 20 more LSK170's in order to have enough stock to match the Idss of the transistors. And a few other parts to build a transistor tester.
Once the transistors were swapped out, I was finally able to install the B1 into my system. Wow, this thing is really good. The system sounds ever slightly better than it did without the B1, which was actually a bit of a surprise, yet does nothing to change the overall character of things.
For those interested in building one themselves, here are links to the parts i used:
Board:
Solder:
Cardas Quad
Power Section:
(1) 1ohm 3 Watt Resistor
(2) 10k Resistor
(1) 1uf bypass Capacitor (aka filter capacitor)
(Depending on ripple coming from power source, can play with size or even add other sizes in parallel to further clean power)
(2) 15000uf Electrolytic Capacitors
(as long as these handle 25v get the most capacitance you can fit on the PCB)
(1) 15k Resistor
(1) 1n914 diode
(this is just used to drain the electrolytic caps when the unit is turned off, quality doesn't matter)
(1) 2.1mm barrel power jack
(This connector connects - to chassis, you may want to consider a connector that is isolated from chassis)
(1) DC Power Supply
(Any 18-24VDC 0.02A or greater regulated PSU will work - consider switching and linear types or build your own - 2.1x5.5mm barrel connector)
(1) LED:
Audio Section:
(6) 1M Resistor
(4)1k Resistor
(2) 221k Resistor
(2) 1uf Polypropylene Capacitor
OR
(The same as the bypass capacitor)
(2) 10uf Polypropylene Coupling Capacitor
(1 or 2) 20 - 25k Volume Potentiometers (Use Stereo Or Mono):
OR
(NOTE: this sets the input impedance of the preamp)
(1) DPDT Toggle Switch for Input:
(1) Enclosure (230x230mm):
(3 Sets) RCA Connectors:
(1 or 2) Knob
(1/4) Chassis Damping Material
22awg Hook-Up Wire
PTFE (Teflon) Tube For Insulating Capacitor Leads
(4) Circuit Board Standoffs
AND
#6 Screws, Nuts, and lock-washers
Wire management
2mm Wire ties
1/2” Self-stick tie blocks
N-Channel JFET’s
2SK170’s, LSK170’s or 2SK370’s
(Buy with Board or from DIYStore or trendsetter.com)
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