Jfet BOZ

[Vix]

Seems that I was too quick to conclude that you're going there this year. You know the local saying: "Sto je babi milo, to joj se i snilo" ...

[Zen Mod]

Originally posted by Vix
Seems that I was too quick to conclude that you're going there this year. You know the local saying: "Sto je babi milo, to joj se i snilo" ...

literally translated :

"what GrandMa wants , that GrandMa dreams off "

[hihopes]

I am trying a "Shiny" type reg. Ive built the prereg and fetlington so far. At first, the voltage wandered around by about 20mV, but after a while it settled down. It is now powering the jfet boz (minus the shunt darlington) and I have to say, it sounds better than the Ni-Mh battery supply I was using. I will add in the shunt stage soon and see how it sounds. I can't believe it will sound any better, but I have to satisfy my curiosity.

[Zen Mod]

Originally posted by hihopes
I am trying a "Shiny" type reg. Ive built the prereg and fetlington so far. At first, the voltage wandered around by about 20mV, but after a while it settled down. It is now powering the jfet boz (minus the shunt darlington) and I have to say, it sounds better than the Ni-Mh battery supply I was using. I will add in the shunt stage soon and see how it sounds. I can't believe it will sound any better, but I have to satisfy my curiosity.

"fetlington" ?

you mean on mosfet&bjt based CCS , right before shunt darlington ?

if yes - I'm curious where excessive current ( not needed for Jboz itself) is drawn .....

[hihopes]

That is a very good question. I have absolutely no idea, but nothing is getting hot. I had it running for some time without any load as well, and I kept feeling the heatsink behind the lm317's and the mosfet and it wasn't even the slightest bit warm. But it sounds pretty fine, even though the caps haven't even run in yet. But then I took a lot of care with everything upstream from the pre-reg/CCS. Do you have anything you would like me to measure?

[Zen Mod]

Originally posted by hihopes
That is a very good question. I have absolutely no idea, but nothing is getting hot. I had it running for some time without any load as well, and I kept feeling the heatsink behind the lm317's and the mosfet and it wasn't even the slightest bit warm. But it sounds pretty fine, even though the caps haven't even run in yet. But then I took a lot of care with everything upstream from the pre-reg/CCS. Do you have anything you would like me to measure?

nope , in fact ......

just finish Shiny as it meant to be , then listen ;

shunt darlington is really vital part .........

[hihopes]

Built the shiny using Zetex ZTX614 Darlington. Sounds very different to what it did. Whereas before it was quite rich and woody sounding, now it has a great deal of high frequency information coming through. It is still not as smooth in the highs as I would like. I think I will experiment with a few different darlingtons.

[Zen Mod]

Originally posted by hihopes
Built the shiny using Zetex ZTX614 Darlington. Sounds very different to what it did. Whereas before it was quite rich and woody sounding, now it has a great deal of high frequency information coming through. It is still not as smooth in the highs as I would like. I think I will experiment with a few different darlingtons.

leave darlington as is - it's not weak link ;

try few other caps ( including different values ) in paralell with darlington ;

try also snubberized bypass

[hihopes]

Glad for the info. As it happens, I woke up this morning and remembered I still had a cheap 2200uF cap in the power line from when I was taking power from a cheap wall-wart for charging batteries. Removed it. I now have a 6uF paper n oil cap there instead. it will probably take weeks to run in, but it is already much better.

I noticed something that worried me a bit today. When I measure the voltage it is not steady. It fluctuates by about 20mv, whether it is playing or not. It did that for a few minutes when I first tried it, but it soon settled down to a rock-solid voltage.

What do you mean by a snubberised bypass? Is that a snubber across the output or something more complex? Is there anything about this specific design on the forum?

I want to make a dedicated 5v power supply for my DAC. Would you suggest a shiny or something different?

[Zen Mod]

I meant on final cap in Shiny - that cap which is in parallel with darlington shunt ;

what you have in initial PSU , meaning on bridge/cap filter before Shiny is important , but not as important is that final cap ;

snubberized - that's nothing else than RC chain ( resistor and film cap) in parallel with that last electrolytic ;

try searching here for snubberized , CarlosFM etc .

stability issues - dunno , probably issue with your actual physical arrangement of circuit ;

few pictures can't kill anyone ....... don't you think ?