B1 Buffer Preamp

[BFNY]

I've noticed sometimes DC on the wiper of a pot makes it noisy when you adjust the volume. So if you skip the input cap and you hear scratchy noise on volume adjustments, you'll know what it is. A discrete resistor based attenuator may work better in that scenario.

 

[udailey]

Instead of using a 15,000uf cap is there any downside to using 12,000uf? I was going to start building today and well, 12kuf is what I have.
Nevermind, took my own advice and reread the article. Down to 1000uf if I want.

Uriah

 

[avr300]

Hey nelson, Do you think that the B1 Buffer would be good with the Mini A ? I'm currently running the mini a with a passive pot, but a little more gain would be nice

The B1 is unity gain, no amplification or gain if you want.

 

[Salas]

Ready & cool

Here it is. The dual supply no coupling capacitors version of B1.
The offset is no problem. We can null it down to zero by adjusting one PSU side out of opposite balance. The channels keep almost totally together for offset. I used 2x6.9mA and 2x7.1mA Idss 2SK170BL as matched pairs. Because one channel grew a little (1.5mV) for offset when the other was totally null, I adjusted for +/- 0.3mV matched between channels. Had to make the PSUs +16/-15V for that. Watched it for 2 hours. No offset wandering. Then I fed 10kHz & 100kHz 6V peak to peak square waves through it, one channel after another. Could not see any difference from feeding the generator directly to the scope. I fed 6V p-p sine waves too. No deformation or compression. That is 2.1VRMS and the same as the CD output standard. I made it totally point to point and used a 50k Bourns dual Log that I had. Its paralleled with Dale resistors from wiper to ground. There is also a 7sec delay output relay circuit.
Listening tests I will do probably tomorrow, hopefully with the aid of a friend. There is a sequence of tell tale pictures concluding my construction report.

 

[Salas]

.

 

[Salas]

..

 

[Salas]

...100kHz

 

[Salas]

....100kHz close up.

 

[Salas]

.....Steady @ 0.3mV offset for both channels.

 

[Tolu]

Impressive

It would be interesting to compare the no-caps-dual-PS-version against the original NP-B1!

 

[jacco vermeulen]

More interesting to hear the Mastah say why he picked a single rail.

 

[Salas]

Impressive

It would be interesting to compare the no-caps-dual-PS-version against the original NP-B1!

I don't know if all people can detect caps in the signal path, but its a costly affair to employ really good ones. I wanted it small, and cheap.

 

[Zen Mod]

More interesting to hear the Mastah say why he picked a single rail.

I bet he's teasing spoiled kids at least half of time

 

[Tolu]

More interesting to hear the Mastah say why he picked a single rail.

I think otherwise he couldn't keep the planned retail price

 

[Salas]

Rock steady

It's been on for almost 12 hours now, the offset is still the same (vanishingly low, under 0.4mV). Should be safe. I will leave it on overnight just in case and take a reading again.

 

[Nelson Pass]

More interesting to hear the Mastah say why he picked a single rail.

It's just easier. For you, not me. I don't lay awake at night worrying about
the sound of capacitors.




/pass/ Gets a good night's sleep.

 

[Tolu]

@Nelson Pass

Hi,

what about the PCBs for B1? I hate perf boards !

 

[Nelson Pass]

Then you'll have to pony up the big bucks at www.passdiy.com

The boards are still a couple weeks out.

 

[Derekva]

Then you'll have to pony up the big bucks at www.passdiy.com

The boards are still a couple weeks out.

Damn! This is almost as bad as waiting for Christmas day in 1977 when I was hoping for Star Wars action figures!

(polishes Visa card)

-D

p.s. I was 8.

 

[Tolu]

Then you'll have to pony up the big bucks at www.passdiy.com

The boards are still a couple weeks out.

Sorry, I can't find them. Or do you mean: The boards will be out in a couple of weeks?