Building a symmetrical PSU B1 buffer

Cheers. Up your 220k across audio input to 560k if you are to use the 50k pot enough more.

Hi Salas,

Does this also apply to the NP B1 Buffer? R105 and R205 are 221k but on the outputs not inputs...reason i ask is i currently have a NP B1 buffer using a 50k alps pot in shunt mod using 47k series resistors. Sounds good, but i am wondering if using a 20k pot with 18k series resistors would sound better.
Also, i would like to try your version of the b1 buffer. As i already have a p2p version of NP B1 would it be easy enough to remove the caps and p2p the power supply for it? I cant seem to find the schematic for your version.

Thanks

Alon
 
So tonight I tidied up my wiring and swapped out that 220K for 2x 270k in series = 540k. So, most of the sibilance is gone, I've spent the last few hours listening to all my usual tracks and while theres a hint of it there, its much reduced. I found some dale 221R in the box tonight so I might sub those in for the xicon and see what the difference might be.

Theres incredible depth to this preamp. I'm getting some of the best sounds ever from my system with this right now. I think that if I can make it just a shade smoother....

Bear in mind i'm using fostex speakers in a horn so they will be absolutely merciless when it comes to sibilance or harshness. If you have a fabric dome tweeter or similar, you most likely won't ever notice anything.

Its quite a preamp - really something else. Just to underline my comments, its obvious that the bit of sibilance is a characteristic of my build rather than the DCB1 per se.


Fran
 
diyAudio Chief Moderator
Joined 2002
Paid Member
Thanks for reporting your steps. This is very useful to the ones who gonna build. In a system concept much can interact, tone up, or mute enough. Especially on speakers with some break up modes around 5-10kHz, you must be careful with all those details we discussed. The DCB1 has been through proto testing so to know from enough people if there is some characteristic issue or not. That gives us the information to know what too look for or not in the first place. Since you are at a good point, even when you are accustomed in using a Lightspeed in a regular B1, not applied in your DCB1 yet, that is a good sign. Even if you did not like it at all, no worries. No egos here. Just DIY.:)
 
diyAudio Chief Moderator
Joined 2002
Paid Member
Hi Salas,

Does this also apply to the NP B1 Buffer? R105 and R205 are 221k but on the outputs not inputs...reason i ask is i currently have a NP B1 buffer using a 50k alps pot in shunt mod using 47k series resistors. Sounds good, but i am wondering if using a 20k pot with 18k series resistors would sound better.
Also, i would like to try your version of the b1 buffer. As i already have a p2p version of NP B1 would it be easy enough to remove the caps and p2p the power supply for it? I cant seem to find the schematic for your version.

Thanks

Alon

In posts 10,11,12 here in this thread you can find the schematics. The original B1 has 1Meg resistors across input, before the wiper to ground nodes. For other reasons than here. Its 221k resistors across output do not interact with an input pot as shown on its schematic. I don't think that big series resistors after the pot, in line with the wiper help you at all. B1 has 1k gate stoppers that you must connect short and straight to the Jfet gates in p2p construction you use.
Whatever p2p you make, be careful if there is no input capacitor in your amplifier. If you miss something with DCB1 when p2p, you can even feed your amp with DC from 4-5V up to rail.:dice:
 
In posts 10,11,12 here in this thread you can find the schematics. The original B1 has 1Meg resistors across input, before the wiper to ground nodes. For other reasons than here. Its 221k resistors across output do not interact with an input pot as shown on its schematic. I don't think that big series resistors after the pot, in line with the wiper help you at all. B1 has 1k gate stoppers that you must connect short and straight to the Jfet gates in p2p construction you use.
Whatever p2p you make, be careful if there is no input capacitor in your amplifier. If you miss something with DCB1 when p2p, you can even feed your amp with DC from 4-5V up to rail.:dice:

Thanks for the reply Salas,

Here are details on the shunt mod that i did.

Shunt Pot Volume Control - World-Designs-Forum

It does sound good, but im not sure if it is suited to the b1 application. I guess the only way of knowing would be to swap it out for a 20k pot and have a listen. Then again maybe i should just get a DCB1 Board and build that. Are there any DCB1 boards available? I like the idea of a capacitorless b1...my power amp is a wad kat34 and im sure it has 1uf input caps.
Here is the schematic to the integrated version, the Kit34.

http://www.simpletube.com/databank/PushPull/EL34_ULPP_ECF80_inte_2.pdf

Do you think the DCB1 could be used with the Kat34?

Thanks for your Help.

Alon
 
so, just one more update on my build. I upgraded to a 25k stepped attenuator and takkman resistors. I ended up with one pair of cardas and 5 sets of connex input RCA's and Cardas for the output RCA's. Wiring was all done with yada yada wire. I am quite happy. The sound is first class. Beats the heck out of anything else I have around. I plan to tote it around to friends houses and try and get some comparisons when time allows. One small issue I am having is simply that the first step of the attenuator is too loud for my wife's taste. What would be the simplest method for dropping the output by a few db's and not screwing up the whole balance of things?
 

Attachments

  • 28.jpeg
    28.jpeg
    34.1 KB · Views: 830
diyAudio Chief Moderator
Joined 2002
Paid Member
Thanks for the reply Salas,

Here are details on the shunt mod that i did.

Shunt Pot Volume Control - World-Designs-Forum

It does sound good, but im not sure if it is suited to the b1 application. I guess the only way of knowing would be to swap it out for a 20k pot and have a listen. Then again maybe i should just get a DCB1 Board and build that. Are there any DCB1 boards available? I like the idea of a capacitorless b1...my power amp is a wad kat34 and im sure it has 1uf input caps.
Here is the schematic to the integrated version, the Kit34.

http://www.simpletube.com/databank/PushPull/EL34_ULPP_ECF80_inte_2.pdf

Do you think the DCB1 could be used with the Kat34?

Thanks for your Help.

Alon

You use a variable Lpad in essence. No, it ups the source impedance quite a lot in exchange for a fixed resistor quality advantage. Use a normal pot, or even one of those nice stepped attenuators on offer, and it will bring you back some hindered dynamic range. As for boards I don't know, PM the GB manager. I haven't got the finals myself even so to leave surplus for members. Really. It proved extremely popular.

DCB1S is quite nice for the 34 kit you linked. Just delete its 100k input pot, no use.
 
diyAudio Chief Moderator
Joined 2002
Paid Member
so, just one more update on my build. I upgraded to a 25k stepped attenuator and takkman resistors. I ended up with one pair of cardas and 5 sets of connex input RCA's and Cardas for the output RCA's. Wiring was all done with yada yada wire. I am quite happy. The sound is first class. Beats the heck out of anything else I have around. I plan to tote it around to friends houses and try and get some comparisons when time allows. One small issue I am having is simply that the first step of the attenuator is too loud for my wife's taste. What would be the simplest method for dropping the output by a few db's and not screwing up the whole balance of things?

Congratulations. Glad that you like it. As for the first scale, what Uriah said.
 
diyAudio Chief Moderator
Joined 2002
Paid Member
hi.do you know somewhere that i can find high quality 20k alps pot or as quality as alps? I have RK27 motorized 50k pot but I heard that 50k is not suitable for B1 buffer.is it true ? thanks

20k I recommend on transparency grounds. It suits the DCB1 better. There is no technical reason that a 50k pot will not work on the other hand. I repeat, you must up the across input 220k resistors to 560k or 680k if to use a 50k pot. As for Alps or alike vendors, Google is your friend.