Building a symmetrical psu B1 buffer

[Malka07]

Originally Posted by Salas

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.

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/P...F80_inte_2.pdf

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

Thanks for your Help.

Alon

[DaveM]

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?

[udailey]

Dave,
Since the shunt resistor is of very low ohms in that position you will change the volume but not the 'whole balance of things' by swapping in a lower value resistor for the low volume shunt resistor.
Uriah

[umut1001]

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

[Salas]

Originally Posted by Malka07

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/P...F80_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.

[Salas]

Originally Posted by DaveM

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.

[Salas]

Originally Posted by umut1001

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.

[umut1001]

I do not have much money and i want to have good quality buffer. I think I will use 50k alps RK27 pot.Thank you

[DaveM]

Doh! That is obvious. I should know better. Thanks for reminding me of the obvious.

[TheShaman]

Hmm.. I'm about to place an order @ Partsconnexion.
Takman or PRP ?