My troublesome Bride of Zen

[jdg123]

Before I rip her apart I have to ask is this bride fixable:

I have checked the PS...it makes a good 59.5VDC

But...when I hook up the rest of my BOZ the voltages get screwy - the 20+ figure of the schematic is the only one I hit. Voltage that should be 8+ is 2.5+ and the 15+ is also 2.5+

Also the PS drops and holds at 35VDC

I have been over and over and over they layout, connections/polarity, insulation...I can't find an error. Is it possible one of my active devices has failed?

 

[Zen Mod]

pics , please

though - if you pull sole mosfet from gain circuit , PSU voltage must stay pretty same as without load

 

[jdg123]

my bride is showing

I don't know how informative these pics can be.

Yes, I suspect my own breadboarding but I have gone over this thing five ways from Sunday and follows the schematic.

Unless...

I have in two places brought leads together in a single point but only where all the normal connections would be along a single trace. If this is a no-no, I am guilty.

At least I have tried to implement the super skinny lead wire on the input RCA's

 

[Zen Mod]

oh boy ......



what can I say - be patient

 

[jdg123]

I have added some graphics to assist...

The red circles are the 10uF/100 and the black are the 1000uf caps. I only indicated one side's 1uf and 10 uF non polar caps. Hopefully you see no errors or I'll feel a fool...

 

[mjf]

hello.
.....is R102 22 ohms?

 

[jdg123]

No! cripes! It is 2212F or 2.21K

That is SO cool of you to spot!

Thanks!

I'll get a 22 ohm in there tomorrow

 

[HIPCHECK]

hello.
.....is R102 22 ohms?

BRAVO!!!!

 

[jdg123]

Thanks!

Bride works fine if you feed her the right numbers

Thanks mjf! Good eye (and I'll keep a sharper one in the future)!

 

[mjf]

fine!
.....and keep your eye on the heat dissipating parts, irf610 and res 1k.......

 

[jdg123]

Yes sir! I played the unit for a few hours last night. The heat sinks on the IRF610 and the 5W1K resistor were A-OK; I tried to give them plenty of air space.

The BOZ is a little miracle. I don't know why but even at seemingly identical volume levels to the DAC straight into my Aleph J...with the BOZ the sound is now sweeter and for sure I can get to higher SPLs now driving KEF 104/2 speakers. The sound is a bit fuller and bass is improved. It could be some kind of filtering I guess as I have added devices to the circuit but it is a happy thing in my case. Many thanks!

 

[vdi_nenna]

Not trying to spoil your party, but if you like this pre, you should try the BOZ-J next.

 

[jdg123]

BOZ-J?

vdi-nenna,

I have not heard of the BOZ-J. May I assume it remains a single stage preamp (using a JFET instead of a MOSFET)?

I have seen a piece of thread by you saying you have sold your BOSOZ and your BOZ? Do you use a BOZ-J now?

I am all ears ;-0

 

[vdi_nenna]

I use it now. Sold bosoz. Still have the boz in a box

Yep. Single Jfet. Easy to build. Sounds great.

Just search for it in the pass forum

Vince

 

[vdi_nenna]

http://www.diyaudio.com/forums/pass-labs/103050-jfet-boz.html

 

[jdg123]

Hey vdi_nenna,

I found the thread last night so only got 25 pages in. I am hoping to find some resolution amongst the participants as to resistor values and power supply...

You bet I'll give it a try! I'm just contemplating where to get the materials and from whom.

Thanks for the leg up! May I PM you when I am done reading if I have specific unanswered questions?

 

[vdi_nenna]

May I PM you when I am done reading if I have specific unanswered questions?

Yeah, no problem. There are some specifics on getting the best sound from it, but it so not complicated. If you like point-to-point (p2p) wiring, this is an easy project. I run this p2p and I don't like p2p only because it takes so long. BOZ-J is too easy.

From what I remember, 16v is a recommended power supply (PS) for this project with a 22 ohm source resistor. Double check that please.
Go with at least a 337/317 or LT1033/1085 regulated PS. Even better, Jan Didden has put together a super regulator board for sale in the store. Worth checking out.
You might even want to redesign the BOZ power supply to the correct voltage by using the correct amount of zener diodes. Your oyster.

I used dual LM317/337 PS- two +16/-16 for mine. Might be over kill, but it helps. One of the best tips I ever got was to use higher than normal VA ratings on preamp transformers (a la John Curl). Don't go too crazy, but if it requires 100mA, just get 1A transformer or better. Just be sure it fits in the case and you fuse it correctly.

More importantly, try to enjoy what you have right now. It easy to get caught up in building the next great thing and never enjoy the music.



Vince

 

[jdg123]

Thanks!

I am still reading just to pay my respects to all in that JBOZ thread.

Step one (beyond the research) is finding the right JFET. DIYaudio store only has high Idss grade "C" unmatched...

I think I am going to go batt power but one day will try that Jan Didden super regulator. I have SO much to learn...and those JFETs to procure.

Cheers!

PS Yes I am pretty sure at page 80 of 120...that I am going to start with those numbers you recall: +16V and source resistor 22R. I might even learn how to play with them

 

[vdi_nenna]

I think you need a B grade jfet and a Idss of around 8-10.
If I have a couple I can send them to you. I'll have to check.
PM is interested.

Vince

 

[vdi_nenna]

I realized I made a mistake. BOZ-J has a positive power supply only. I was thinking about my BA3-pre by mistake. You should still use a good regulator for the postive side.
It's that much simpler now.