B1 Buffer Preamp

[Spe@kerBox]

Here are some images. Yes a little crowded - but works perfectly. Still have to add the safety bridge between earth and signal ground.

 

[sarathssca]

One of the keys to good performance with that chip is an
extremely high impedance load.

Can we use these digital pots (ds1802/ds1882) for tone controls like baxandall tone control circuit and replace mechanical pots with these digital pots? For volume control these can be followed by a high impedance opamp buffer. But for tone controls this may not be possible as its wiper output will be connected to a resistor or a capacitor which may not be as high impedance.
Please suggest if we can use these or other digital pots for tone control in a pre-amp?

thanks and regards
S Sarath

 

[Rewind]

Could two B1 preamps be used to match the impedances of a minidsp digital crossover unit and a 2A3 tube amplifier, so that I can split the signal with a RCA Y-cable and keep one of the channels pure analog, and use a digital XO on the other simultaneously? I want to correct the bass while listening to pure analog on the mids and tweeter horns.

 

[2 picoDumbs]

Can you draw the idea on paper showing all components in the chain.

 

[Rewind]

Can you draw the idea on paper showing all components in the chain.

I would like to use the Pass B1 as a buffer AND a splitter. I don't think most active splitters are as gentle as the B1 Buffer Preamp is on the signal.
I can't use my Minidsp 10 output digital crossover with my tube amp, that powers mid and high horns. I would however like to use the Minidsp with a Firstwatt F5 for midbass and a Bittner Audio 800W amp for subwoofers. I want to be able to correct the bass easily with digital EQ, and maybe even with Dirac room correction further on. But I want the tube amp to be completely analog, even when the source is not.

We are discussing it a bit here. http://www.diyaudio.com/forums/mult...ctive-digital-xo-sub-midbass.html#post4477937

 

[AndrewT]

Splitting one signal to feed two receivers is easy. Just attach two output resistors to the B1. One resistor feeds one receiver.

Splitting phase cannot be done by the B1.

 

[Rewind]

Splitting one signal to feed two receivers is easy. Just attach two output resistors to the B1. One resistor feeds one receiver.

Splitting phase cannot be done by the B1.

Sounds good, as long as I don't need to split the phase. Is that preferable in this sitaution where I want two identical signals from the B1?

 

[noelectrix]

does 1 need regulated supply?

I have been given a nice PCB file with the ACA-amp and B1 buffer on one board. I want to have a Pot on ACA and a buffer was recommended.

Since i want to make a normal unregulated simple C-R-C PSU the Buffer will have same unregulated current/voltage. Both (ACA and B1) use same19 VDC.

most Preamps do have regulated supplies, Nelson has mentioned B1 has some tolerance concerning fluctuation...



thanx,
stefan

 

[noelectrix]

headline should say "does B1.."

 

[Spe@kerBox]

headline should say "does B1.."

I used a simple zener voltage reference with a follower on mine. Lots of filtering too - but it sounds fantastic!

 

[noelectrix]

cwmartin, is there something to read about your built here? If not do you have a schematic?

best´n tnx,
stefan

 

[noelectrix]

could it be that simple? it is of course too complex for me to calculate the R´s and the current ratings
but since there is a 18V zener and a expected PSU DC output of about 19,5V there would be some headroom.

An externally hosted image should be here but it was not working when we last tested it.

 

[Spe@kerBox]

cwmartin, is there something to read about your built here? If not do you have a schematic?

best´n tnx,
stefan

Stefan - sorry but I don't have a schematic mainly because it is such a simple circuit. If you search for "zener follower voltage" you will find a plethora of examples everywhere.

Regards, Craig

 

[AndrewT]

Pass has a Zener Follower on his site.

 

[MNYankee]

Hi, I am new here and I am a newbie when it comes to diy and elctronics although I do have decent soldering skills and have rebuilt some electronics in the past. I am building a B1 for my son with upgraded parts- Tx2575 resistors in input section, Riken Carbons in the output and the rest will be Audio Note Tantalums and Dale-Vishay.

I like a warmer sound with good air and transparency. I am trying to decide on caps. My son's amp is one of my hand me down's, a Parasound A21 which needs some warmth and transparency.

I am considering Obliggato Premium Gold 630v, Mundorf M-Cap Supreme 600V or Clarity 630v caps for the 1uF and 10uF caps.

Can any one recommend any of these caps? Can I mix a Mundorf with the Obbligato or Clarity's?

Any help would be much appreciated.

Thanks,

Larry

 

[LBHajdu]

B4(buffer) v.s. B1

I notice that the B4 crossover which came out in 2011 is DC coupled verses the B1 which came out in 2008 and uses cap coupling. They both use the laptop power supply so I am assuming that a virtual ground is constructed most likely by using two resistors of equal value with two caps across them. Now it goes without saying that we audiophiles lay awake at night worrying what we’re missing with those caps in the signal path. So if the B1 had to be redesigned today would it be designed in this fashion?

My thinking on this is that the B1 was partly designed as a DIY project and if one of the said diyers has a laptop power supply in which the negative output is connected to earth ground a virtual grounding system would release the magic smoke because the case with the RCA jack would be floating halfway between the rail and earth ground and this would flow via the shield of the RCA connector to upstream and downstream components. My guess is this can only be mitigated by making sure the laptop power supply is not replaceable (permanently connected), my guess is this is the case in the case of the case of the B4. I was wondering what users opinions are on using virtual grounds from laptop power supplies?

It’s really neat that one could have a whole audio system (amp camp amp and a preamp) both running off a 19v laptop supply. I have noticed you could also have supplies up to 42V, seems like that would offer room for active regulation. Also with the virtual grounding system the jfets can be run at higher voltages because both rails will rise at the same time from the virtual zero, so at power on there will not be a large startup voltage.

 

[mach1]

You obviously need one of these:

Ground Boxes | Entreq

no need to stay awake at night any more.....

 

[mach1]

Maybe go for the de-luxe electrolyte enhanced model ?

http://yourownvet.com/wp-content/uploads/2012/06/cat-straining-in-the-litter-tray.jpg

guaranteed to give liquid mids and highs.
http://yourownvet.com/wp-content/uploads/2012/06/cat-straining-in-the-litter-tray.jpg

 

[LBHajdu]

The solution(s) is not valid, even if the case is insulated the RCA connector still has a ground shell which it needs to connect the signal grounds together. If one is at zero volts to ground and the other is at 10v or 20v you still get magic smoke.

 

[Nelson Pass]

I have yet to see a laptop or other little appliance switching supply that
shares AC ground with the output.

You can always check for it with an ohmmeter.