[BradJudy]

As I type, I'm listening to music on my computer via my newly finished PassDIY B1 pre-amp (to a Trends TA-10.1 with the pot bypassed).  It seems to be working well and is sounding very clear.  I might have to swap in a log pot - I tried a linear one because I had a 50k one sitting around and Nelson spec'ed a linear because he felt the adjustment range wasn't needed with unity gain.  For now, I just lowered the computer volume so I have a more usable range. 



Listening to Happy Holidays from KBCO 2003 - my favorite Christmas album is still one I got for free - great performances and very good quality. 

[HAL]

Brad,
The Pass DIY B1 looks very good.

It will be interesting to give it a try!

Glad to see you like the sound quality.

[BradJudy]

Rich - did your package arrive yet?  If not, it should be there shortly. 

[HAL]

Brad,
Ooooh, a package! 

Not package yet, but did get the NEO2X baffles today! 

[Folsom]

If you are using a PC will you be better off with the volume all the way and a log pot. Bits drop when the volume on the PC drops. However altogther I would recommend I2S or even USB out to something first.... I would put the pot BEFORE your pre-amp so that the impedance to your amp is not so high.

Those JFET circuits... the better the PSU and film caps you have the better it will sound. They could compete with Burson's or even higher grade stuff (which might be using them) with the right parts used.

I am sort of curious why this circuit went to all the trouble to have film caps in the signal path. Well maybe the whole setup is dependent on the simple 18+v in, no 18- . got me.

[richidoo]

I heard the preamp at RMAF, sounded good!  Thanks for letting us know the PCB's are available.

http://www.passdiy.com/order.htm  -  oops! already sold out!

Rich

[BradJudy]

If you are using a PC will you be better off with the volume all the way and a log pot. Bits drop when the volume on the PC drops. However altogther I would recommend I2S or even USB out to something first.... I would put the pot BEFORE your pre-amp so that the impedance to your amp is not so high.

Yes, as I said, the lower volume on the PC is what I'm doing for the moment while there is a linear pot in there. 

The pot in this circuit IS before the buffer, so there's no worry about impedance issues with the amp. 

[BillB]

Awesome Brad!! I would love to hear this next to the Aikido some time.

[SetterP]

Very nice work Brad.  I'd like to give it a listen sometime.

[HAL]

If you are using a PC will you be better off with the volume all the way and a log pot. Bits drop when the volume on the PC drops. However altogther I would recommend I2S or even USB out to something first.... I would put the pot BEFORE your pre-amp so that the impedance to your amp is not so high.

Those JFET circuits... the better the PSU and film caps you have the better it will sound. They could compete with Burson's or even higher grade stuff (which might be using them) with the right parts used.

I am sort of curious why this circuit went to all the trouble to have film caps in the signal path. Well maybe the whole setup is dependent on the simple 18+v in, no 18- . got me.

The B1 has a single ended +18VDC power supply. 

[Russtafarian]

I just got a box of parts from Mouser to build up a few of these.  I'll be breadboarding it since I missed getting a PCB before they sold out.  I want to try it as an output buffer for the voltage DACs in my SB3 and Oppo DV-970.

What are you using for a power supply?

Russ

[BradJudy]

What are you using for a power supply?

I'm using one of these running at 24V because I already had it for my headphone amp.  Eventually I'll buy or make a power supply for the B1, but this was the easiest and cheapest approach for now.

http://tangentsoft.net/elec/teps/

[nodiak]

BradJudy, curious if you have an update on the B1's performance with your gear. Also any price range for parts? I generally use 92db+ speakers so like the idea of no gain. How many sources is yours set up for? I may want to try this rather than integrateds.
Don

[Russtafarian]

I'm still plugging away at building my B1 clone.  I'll call it a clone because I'm using BF245A buffers instead of the 2SK370's specified by Pass.  I'm about ready to hook up the audio connections and power supply.  I'm building it as a balanced system (4 channels for L+,L-,R+,R-) that will feed Lundahl output transformers rather than use output coupling caps.

I have a question about input impedance.  I'm not putting a volume control potentiometer on the input because I plan to use the B1 with SB3 and Oppo players that have digital volume controls.  The schematic http://www.passdiy.com/pdf/B1%20Buffer%20Preamp.pdf specifies a 25k pot which sets the input impedance.  Should I substitute a resistor in it's place?  I don't have a 25k resistor but I can use two 10K in series for 20k or use a 100k.  What's preferable, 20k or 100k for input impedance?  The SB3 and Oppo both have 10k across their cap-coupled outputs.

Also, since this is balanced, should the input impedance resistor be put across the + channel and the - channel?  Or should there be two input impedance resistors, one from the + channel to ground and the other from the - channel to ground?

Thanks for the help.  I'll post picture once I get it up and running.

Russ