B1 Buffer Preamp

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#2,901
Mark2727 said:
Hello,

I'd like to ask some questions of a few of you fellows who have actually built this (using Nelson's boards). Here are some questions to start off:

1) Is there a parts list (with suppliers) posted anywhere?
2) As I understand it, I only need a single board? Is this board for audio only or does it cover the power supply also?
3) What about a easy to understand schematic for using a toroid rather than a so-called "wall wart" power supply?
4) Or, would a "wall wart" power supply be just fine?
5) Does anyone have an online source for the PEC volume pots?

I realize I'll need "extras" such as an enclosure, RCA jacks, a selector switch and the volume pot. Anything else I might consider ordering? I though of standoffs for the board.

Maybe more questions down the line too. I'd like to build one. Just so you know I am an amature, although I have build several Bottlehead kits with success.

Thanks in advance for you help! I'm sure some of my answers appear in this very lengthy thread, which I will attempt to read in its entirety.

My e-mail is ms_williams@hotmail.com if you need it.

Mark
Click to expand...

I've never built anything before and was able to put it together and worked right the first time. There is a nice step by step instruction and answers to your questions in this thread here:

DC-Coupled B1 Buffer Build

It had become my reference preamp now replacing a more expensive tube preamp 😀
 
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#2,902
Thanks for the information

Hello,

Thanks to you and all the fellows who have posted so far! Wow.

I need to find out if these power boards are still available.

You guys have been great. I'm sending off my order to Nelson Pass today for his board with fets.

Mark
 
#2,906
parodielin said:
I have a B1 and am thinking to change the volume pot. I ran into this:

Balanced Attenuator

Would this work on the B1? I don't know the difference between "Balanced Volume Pots" and "unbalanced volume pots". I guess the B1 is an unbalanced for volume on left and right channels?

Thanks!
Click to expand...

that looks like its used for balanced signals. try the other one if your not running balanced. I use it and sounds great with B1
 
#2,909
I have a problem with my B1 after removing C100 and C200... My B1 is a production version bought from Reno. Because my DAC has coupling caps at the output and I measured almost no DC at the output, I thought I could remove the coupling caps at the input of the B1 without a problem. However, now I have a very distorted sound... Sounds like a clipping amp, even at lower volume level... I didn't put the caps back to check if it's O.K. again, but I am quite sure I didn't make a mistake. (except for removing the caps perhaps...) ;-)

Is there an explanation for this behaviour?

Thanks in advance,

Mark.
 
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#2,910
#2,911
Mark Verhoeven said:
I have a problem with my B1 after removing C100 and C200... My B1 is a production version bought from Reno. Because my DAC has coupling caps at the output and I measured almost no DC at the output, I thought I could remove the coupling caps at the input of the B1 without a problem. However, now I have a very distorted sound... Sounds like a clipping amp, even at lower volume level... I didn't put the caps back to check if it's O.K. again, but I am quite sure I didn't make a mistake. (except for removing the caps perhaps...) ;-)

Is there an explanation for this behaviour?

Thanks in advance,

Mark.
Click to expand...

It puts out 9V DC towards your source, that is why. Put them back.
 
#2,914
M_Balou said:
you´re right. i used on of these for my best friend´s tube-buffer.
nice quality and a good idea to use SMD-resistors, leads to short
signal path.
And i´m going to use on of these for my B1, too
but doesn´t the B1-Manual says the pot should be linear ?
Click to expand...

Yes linear pots are what is listed.I used PEC linears when I built a B1 and swapped them into a DCB1 but they give limited movement of the pot going from quiet to loud in a quarter of a turn. Someone on the forum mentioned a Goldpoint style attenuator they'd found on ebay so I bought one and have not regretted it. The DCB1 is a class act.
 
#2,918
Unbalanced Right and Left Channels

I know this would sound old because I have that problem long time ago. There was a time I thought I had solved this problem.

The issue: My B1's left channel is 3-6 dB lounder than the right channel.

This is confirmed last night by the new SPL measurement tool as with my ears.

What I've done:

- The issue is with B1. I've switched channels, switched pre-amp, using the same test tone from the same amplifier and the etc. This is not my room has more reflective on the left side. The measurement was taken from the same position (Speaker was placed in the same position).

- Checked all resistors. The stereo volume pot has the same resistance on both channels. There are two resistors next to diodes that I cannot get a reliable readings.

- All grounds are zero. I did a chasis ground in a metal enclosure.

- I used the PCB and matched JFETs from Pass.

I have a DMM and a LCR. What should I check for where the problem might be? I switched back to HK 635 as the preamp. The B1 sounds way better so I think I'd like to work on this issue again.
 
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