Nelson Pass B1 preamp build

[337alant]

Ah I see, sorry miss read the thread
excellent switches the Elma, I use them myself
Alan

[Bigman80]

Ah I see, sorry miss read the thread
excellent switches the Elma, I use them myself
Alan

No worries!

I had one in the Slagle and it was quality so why go anywhere else!

[Jazid]

If I'd kept it I'd have been keen to try upping the bias, but for that you'd want a bigger trafo and heatsinking. I'm pretty sure you have also got a bunch of audio note silver phono sockets on there as well, it's a nicely made bit of kit. And it never hummed at all so the trafo must be well enough shielded.
Wish I could remember which chap sold it to me. Anyone recognise it?

Sent from my BLA-L09 using Tapatalk

[Bigman80]

If I'd kept it I'd have been keen to try upping the bias, but for that you'd want a bigger trafo and heatsinking. I'm pretty sure you have also got a bunch of audio note silver phono sockets on there as well, it's a nicely made bit of kit. And it never hummed at all so the trafo must be well enough shielded.
Wish I could remember which chap sold it to me. Anyone recognise it?

Sent from my BLA-L09 using Tapatalk

Gave it the once over today and there's a quite a lot of "build up" on the sockets and which looks like it's in the sheath of the wires too.There's also some on the RCA sockets. Nothing a good clean won't fix.

I decided to replace them and get some of the best quality copper wire known to man!!!

Upping the bias may be possible BUT as it will require a new TF I leave that for now.

I may end up having to remove the TF to fit everything in so if I do I will go bigger on the TF too.

[Yomanze]

Here's a quote from Nelson Pass himself, taken from his page about the B1:
"The preamp typically draws fewer that 0.02 amps, so current is not much of an issue."
That transformer will deliver 20mA easily. There's no need for anything bigger.

This unit (DCB1) uses shunt regulators, so has much higher current draw. Some people set the bias really high, over an amp, and big heatsinks.

[Bigman80]

Here's a quote from Nelson Pass himself, taken from his page about the B1:
"The preamp typically draws fewer that 0.02 amps, so current is not much of an issue."
That transformer will deliver 20mA easily. There's no need for anything bigger.

I read that too. Was just about to look into the merits of upping the bias. Won't bother

[Bigman80]

Why?

This unit (DCB1) uses shunt regulators, so has much higher current draw. Some people set the bias really high, over an amp, and big heatsinks.

[sq225917]

Me neither, but I'd design it so that it offered the ability to shunt as much as the rest of the circuit consumed.

[Yomanze]

Shunt regulators? Does that mean they're like zeners?
Personally, I wouldn't design something that had the regulators drawing more current than the amplifier does.

Yep, similar, except an LED voltage reference is used in place of a zener.

[337alant]

The PFM B4 is a good bootstrap buffer stage as well no gain though
I replaced mine with 2 x Avondale Audio 821A boards (4x gain) and am very happy with it

Alan