Thank you Tinitus.
I´ll use the B1 with 300B monobloc, JE labs schematic. The speakers have 97 db/wm and have a little hum with my dact pasive preamp. Perhaps the problem be in the ground or wire. Without pream, bridge rca don´t have hum. Independently of noise, I hope the sound will be better with the buffer.
Whats transformer do you use with B1? I´m thinking purchase 2x12 30VA
Regards
I´ll use the B1 with 300B monobloc, JE labs schematic. The speakers have 97 db/wm and have a little hum with my dact pasive preamp. Perhaps the problem be in the ground or wire. Without pream, bridge rca don´t have hum. Independently of noise, I hope the sound will be better with the buffer.
Whats transformer do you use with B1? I´m thinking purchase 2x12 30VA
Regards
Attachments
Is this what is happening?
I am in the process of building a B1 Buffer and want to understand what is going on with the JFETs as the CCS is forcing the upper JFET to work at Vgs=0
I got some curves from the generic 2sk170 in LTSPICE and drew what I think is the load line.
Can someone confirm if indeed this is the case?
Link to short animation
I am in the process of building a B1 Buffer and want to understand what is going on with the JFETs as the CCS is forcing the upper JFET to work at Vgs=0
I got some curves from the generic 2sk170 in LTSPICE and drew what I think is the load line.
Can someone confirm if indeed this is the case?
Link to short animation
Attachments
Yes, the lower jFET (the CCS sink) has G connected to S and that sets it up to pass ~Idss when the voltage of Vds is ~10V
This current is pulled through the upper jFET (the amplifier).
When the upper device is selected to have the same Idss as the lower, then when Id is = Idss then Vgs must be zero. That is what you have measured.
Because your input is between Gate and Audio Ground and the output is between Source and Audio Ground, then the output offset is the difference between Gate voltage and Source voltage. If you measure between the DC blocking capacitors you will see that near zero Vgs.
This current is pulled through the upper jFET (the amplifier).
When the upper device is selected to have the same Idss as the lower, then when Id is = Idss then Vgs must be zero. That is what you have measured.
Because your input is between Gate and Audio Ground and the output is between Source and Audio Ground, then the output offset is the difference between Gate voltage and Source voltage. If you measure between the DC blocking capacitors you will see that near zero Vgs.
The supply sets the limit for the maximum output swing.
If the supply is 18Vdc then expect output swing to be <16Vpp.
If you increase the supply to 24Vdc then expect output swing to be <22Vpp.
This is exactly the same as for power amplifiers and for opamps and everything in between.
If you have a buffer that has a gain of ~1, then the max input swing will be <Rail to Rail voltage less a bit.
BUT !
The second harmonic starts becoming enormous as the output approaches the rails.
That's where the voltage overhead gives a big benefit to music reproduction.
I try to get near 20dB of overhead from max signal to max not clipping voltage, in stages preceding the power amplifier. I would suggest a minimum of overhead of 10dB.
i.e. if you use Sources that can output a 0dBfs signal of 2.3Vac, then the Buffer should be able to handle ~7Vdc unclipped and that requires ~21Vdc for ~19Vpp. The DCB1 uses +-10Vdc allowing +9.2dB above 2.2Vac
If the supply is 18Vdc then expect output swing to be <16Vpp.
If you increase the supply to 24Vdc then expect output swing to be <22Vpp.
This is exactly the same as for power amplifiers and for opamps and everything in between.
If you have a buffer that has a gain of ~1, then the max input swing will be <Rail to Rail voltage less a bit.
BUT !
The second harmonic starts becoming enormous as the output approaches the rails.
That's where the voltage overhead gives a big benefit to music reproduction.
I try to get near 20dB of overhead from max signal to max not clipping voltage, in stages preceding the power amplifier. I would suggest a minimum of overhead of 10dB.
i.e. if you use Sources that can output a 0dBfs signal of 2.3Vac, then the Buffer should be able to handle ~7Vdc unclipped and that requires ~21Vdc for ~19Vpp. The DCB1 uses +-10Vdc allowing +9.2dB above 2.2Vac
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Thanks Andrew.
I will be using a dual regulated supply that I found at my local surplus. It is +-15V. That should give me then approx +13db on the 2.2Vac. Initially I was planning to modify the supply voltages to +-9 cause from what I have read on the threads most people prefer the sound of it. I should probably listen to the +-15 before modifying it.
I will be using a dual regulated supply that I found at my local surplus. It is +-15V. That should give me then approx +13db on the 2.2Vac. Initially I was planning to modify the supply voltages to +-9 cause from what I have read on the threads most people prefer the sound of it. I should probably listen to the +-15 before modifying it.
Hi,
I bought a chinese copy of the B1 buffer on the bay:
What could you recommand me to improve its quality?
I think I'll supress the 10 uf capacitor because this cap is only there to protect the input of the amplifier... since my amplifier has already a 2.2uf cap on its input there's no problem to avoid the 10uf and as you know less is more...
For pot I've already a 10k RK40 alps black beauty pot; the best of this type I've heard
So there's only the 1uf to change for a better one: which one could you recommand me?
And what about the serie resistors? is there a better brand you can purpose me?
Have a good week!
I bought a chinese copy of the B1 buffer on the bay:
What could you recommand me to improve its quality?
I think I'll supress the 10 uf capacitor because this cap is only there to protect the input of the amplifier... since my amplifier has already a 2.2uf cap on its input there's no problem to avoid the 10uf and as you know less is more...
For pot I've already a 10k RK40 alps black beauty pot; the best of this type I've heard
So there's only the 1uf to change for a better one: which one could you recommand me?
And what about the serie resistors? is there a better brand you can purpose me?
Have a good week!
No disrespect intended.
I am not holier than thou.
Here are my suggestions.
1) Purchase two (2) very good bottles of Cabernet Sauvignon. (You will use these later).
2) Discard the Chinese fake Pass B1 into the trash. Support the Man who chooses to freely share his hard work and art with us.
3) Go to Pass DIY and buy a real Nelson Pass board with matched JFETs.
4) Bottle One: Include with your payment to Mr. Pass for the board and matched JFETs one bottle of Cabernet Sauvignon.
5) Assemble your real Nelson Pass B1 board using the components he recommends in his writing here: B1 PDF
6) First, power your new Pass B1 with two 9 volt batteries wired in series.
7) Bottle Two: Listen to your new battery powered B1 and enjoy.
7a) If you absolutely feel the need to tweak... There are plenty of opinions in this and other Pass B1 threads.
Recently I found in my toy box a board and matched JFETs I purchased directly from Mr. Pass many years ago.
I assembled it last week and could not be more impressed!
This week I will order another board + matched JFET's and send a properly aged 2005 Napa Valley Cab as a small token of my appreciation.
Best regards,
-BB
I second that!
Yes, I "second" that! I met Mr. Nelson Pass many, many years ago at an audio store in Michigan when he was launching a little company called Threshold. Was impressed with him then and even more so now. He has given generously to this community and deserves our most sincere respect and gratitude. Giving freely of your knowledge is to me, the true mark of a man.
And I'd like to take this opportunity to thank 6L6 for his help with building my B1. I couldn't have done it without his encouragement and help.
This is my main preamp. It just does everything right, and gets out of the way!
Thank you Jim, and thank you Nelson.
Mark
+1. The above is amongst the most appropriate and accurate posts concerning the B1 I have ever read.
Yes, I "second" that! I met Mr. Nelson Pass many, many years ago at an audio store in Michigan when he was launching a little company called Threshold. Was impressed with him then and even more so now. He has given generously to this community and deserves our most sincere respect and gratitude. Giving freely of your knowledge is to me, the true mark of a man.
And I'd like to take this opportunity to thank 6L6 for his help with building my B1. I couldn't have done it without his encouragement and help.
This is my main preamp. It just does everything right, and gets out of the way!
Thank you Jim, and thank you Nelson.
Mark
Attachments
Nice looking B1 Mark.
I am guessing the audio store in Michigan is Audio Dimensions?
-Bill
Mr. Nelson Pass
Hi Bill,
No...it was a crazy name. A store in Kalamazoo called Mr. Toad's Sound Concepts. I swear to God!!!
I'm not making it up!
Nelson had DARK HAIR and was SKINNY!
Mark
Hi Bill,
No...it was a crazy name. A store in Kalamazoo called Mr. Toad's Sound Concepts. I swear to God!!!
I'm not making it up!
Nelson had DARK HAIR and was SKINNY!
Mark
........
Nelson had DARK HAIR and was SKINNY!
Mark
Now you're just picking on the man.... ;-)