Hi,
Came across the JFET buffer design paper pointed out in the link. Nice and simply. I would like to design that one and compare it with my B1 buffer. But, I am not able to find out the values for the following items -> Cc, RIN, RL. an someone let me know the correct values to be used ?
Best regards,
Bins.
Came across the JFET buffer design paper pointed out in the link. Nice and simply. I would like to design that one and compare it with my B1 buffer. But, I am not able to find out the values for the following items -> Cc, RIN, RL. an someone let me know the correct values to be used ?
Best regards,
Bins.
for folks that want to read about design of the jfet single ended buffer, i wanted to share again this article from dennis feucht.
i first saw this circuit in the early 70's (yes, i am an old phart) in some old (even back then) national semiconductor datasheets showing test circuits for some of their parts.
i don't have access to an audio precision (maybe mr. pass can share some data at some point), but you can get pretty good performance from this circuit using some cheaper, easier-to-get jfets like the 2N5484, etc. so, save your 2SKxxx for your phono preamps.
enjoy!
mlloyd1
Hi,
I built the Pass B1 using the BOM here: Nelson Pass B-1 preamp kit
Using Passdiy's board, JEFTs, Alps 50K pot, ...
I put the board on a MDF and lift it so no direct contacts with the board from the bottom (picture below) and...
The situation is now like this: When I hook it up (Class D amp), I turn the volume to minimum, input switch to the correct input (either 1 or 2), and there will be "Buzz or Hums" from the right channel. When I turn the volume to maximum, "Buzz and Hums" will come out from both channels. If I touch the bottom of the left most resistor right next to the cap, there will be big hum/buzz from the left channel (regardless of whether there is input signal or not).
When music is coming from Input 1 and I set the input switch to "Middle" or "input 2", if I turn the volume all the way to maximum, I can hear the music playing in low volume along with big hum/buzz. I feel like the sound is "leaking". Is that normal aside from the buzz/hum problem?
I added the LED and it is working correctly - it will light up when the power is on.
Any helps are appreciated!!!
I built the Pass B1 using the BOM here: Nelson Pass B-1 preamp kit
Using Passdiy's board, JEFTs, Alps 50K pot, ...
I put the board on a MDF and lift it so no direct contacts with the board from the bottom (picture below) and...
The situation is now like this: When I hook it up (Class D amp), I turn the volume to minimum, input switch to the correct input (either 1 or 2), and there will be "Buzz or Hums" from the right channel. When I turn the volume to maximum, "Buzz and Hums" will come out from both channels. If I touch the bottom of the left most resistor right next to the cap, there will be big hum/buzz from the left channel (regardless of whether there is input signal or not).
When music is coming from Input 1 and I set the input switch to "Middle" or "input 2", if I turn the volume all the way to maximum, I can hear the music playing in low volume along with big hum/buzz. I feel like the sound is "leaking". Is that normal aside from the buzz/hum problem?
I added the LED and it is working correctly - it will light up when the power is on.
Any helps are appreciated!!!
Attachments
I had a couple power supplies around and figured why not try to put them to use? I head that laptop power supplies are pretty quiet and this keeps build cost and complexity to a minimum. In theory...
After a few experiment, the noise will change if I move the location of the pre-amp. It tends to get smaller if I lift it higher. The Class D amp is on the ground residing in a MDF box.
If I use a different amp (HK 635), the noise will change - smaller in this case.
Am I having EFI or something similar? Would grounding help? How to ground the Pass Preamplifier?
If I use a different amp (HK 635), the noise will change - smaller in this case.
Am I having EFI or something similar? Would grounding help? How to ground the Pass Preamplifier?
Everyone should give the Lightspeed a try as replacement of the B1's volume pot. It varies from 55R to 30k with a 5.5V supply. I have it connected directly to my amp which already has a buffer so I'm not building a B1. Highly recommended...here's the link to my post at the LS thread- http://www.diyaudio.com/forums/anal...uator-new-passive-preamp-320.html#post2164061
Of course DCB1 builders should try it too...so simple and cheap!
Of course DCB1 builders should try it too...so simple and cheap!
Looks like noise pickup. Check your grounding, put the pcb in a grounded metal box, and keep it away from an unshielded
Class D amp.
Hi guys, here is a picture of my B-1, as you can see it is a "plywood wonder" for now! I am planning on creating a nicer case for it, as well as making it into a balanced version. For now I am just enjoying it, sounds great!
Thank you Mr. Pass
P.S. if anyone has a leftover B-1 board from the peranders group buy, please e-mail me.
Thank you Mr. Pass
P.S. if anyone has a leftover B-1 board from the peranders group buy, please e-mail me.
Attachments
Did I see a grounding wire in the up-right corner of the board?
I am using a MDF box and was thinking how can I ground the PCB. It's picking up noises...
I am using a MDF box and was thinking how can I ground the PCB. It's picking up noises...
Hi guys, here is a picture of my B-1, as you can see it is a "plywood wonder" for now! I am planning on creating a nicer case for it, as well as making it into a balanced version. For now I am just enjoying it, sounds great!
Thank you Mr. Pass
P.S. if anyone has a leftover B-1 board from the peranders group buy, please e-mail me.
Looks like noise pickup. Check your grounding, put the pcb in a grounded metal box, and keep it away from an unshielded
Class D amp.
I did not do any grounding. If I place B1 in a MDF box (don't have any metal box), or wood board, could I use the four corners of the PCB to do grounding?
I saw a guy putting B1 in a cigar box, using four mounting screws lifting the PCB up, place copper tapes on the wood, and put mounting screws on copper tapes. Would that work in my case?
Thx!
That's better than messing up the kitchen table and that where most projects end up being assembled...
Ask Mr. Pass... LOL
I use a large cookie sheet / pan. Low side walls.