My Take on X-BOSOZ

Jump to Latest
#921
chipco3434 said:
More OT!



Cut it out? As in removed it? Gone - nada- nothing?
Click to expand...



Yep. Actually it's pretty common to do as long as you can take the heat away. I simply forgot to do it! My mini has no r13 and my speaks dip to 4R so the more bias the better. When you increase the value of that R you increase bias. Removing it simply maxes the current configuration out.

That's r13 Briangt (r17? nelson).

OK...as you were:clown:

Russ,
I'm running out of space in my pre as it comes together. I'm gonna need you to design a fully integrated attenuator about half the size of the twisted!:clown: ...or maybe I just need a bigger hammer@! Why do I pack things so damn tight all the time....?
 
#922

Attachments

  • _mg_3274-2.jpg
    _mg_3274-2.jpg
    92.7 KB · Views: 703
#926
mpmarino said:
WOW!😱

That's a lot of hardware in that chassis! How does it sound? Looks like your taking the dcx2496 concept as far as possible...I'm interested to see how it all works out.

regards..
Click to expand...

Yea a lots of wires as well and I hate wires.
:dead:
I have been toying with DCX for a long time and tried many combinations. Based on this preamp, you will laugh when I say that less is always better. Opamps in the output of DCX and that whole circuitry is bad and really destoys the sound. Cutting it out is best solution. Than the question is what than. AKM DA converters already give you plenty voltage out with plenty of DC as well. You could opt for some kind of Low pass filter that will include caps in order to cut DC and HF noise above 50K. For ballanced 6 channel operation that is 12 high quality caps. Price wise not too far from 6 ballanced Lundahls that will do exactly what filter will do but without cap in the signal way.
For some amps I had, just having Lundahls before amps was quite sufficient and really my prefered way of running it. It has outstanding clear, detailed and open sound. The best out of all. But since I introduced Aleph 30 to my system I really needed some preamplification. I made preamp with OPA627 and BUF634 and that was OK. With XBosoz I could hear minimum interference and change in the signal. It is almost like having nothing in the way of the signal. Keep in mind that I still have two channels without XBosoz - just Lundahls and I could easily compare. So far XBosoz is exeptional. If you have to have preamp in the chain have a XBosoz!
 
#928
Not even close to done. I still have to build my twisted log atten. Also my remote control to run the motorized pot will come from a toy I'm waiting to come in (dang thing is costing me six bucks!:dead: 🙂 ). Still need to scrounge for connectors and that .5" alu is a son of a blank to shape. All I can say is that it warms up so far....

OH...and I forgot about a power switch! Gutta figure out something in mara...the same wood the knobs are made of.
 
#930
My first thought is a bad FET(probably Q2 or Q4). I had a channel go bad on me after a static disharge while doing some temp check while the amps were on my bench playing. One second there was music, one second later zap, then silence on one channel. Man was I bummed. 🙁 I replaced the bad FET and all was well again.

Since then I have been much more careful about ESD.
 
#931
It's not Q4, so will try both on this go around. Did you add bleeders at any point that are not on the board? I notice the R2, R7 and companions stay at 60 Volts for a long time after powering everything off.

And of course, the other channel quit and I did not even touch it while doing this work.
 
#932
Hmm, well at first when I was playing with the PS I used 10K 3W bleeder resistors between the leads of the big caps, but I took them out after I was done fiddling. The preamp will play for 10 seconds or so after flipping the switch. 🙂

When I zapped my channel, because I did not trust my method for testing FETs, I just replaced all five of them. Since then I have learned how to test FETs, but it can very difficult (if not impossible) to do it with them in situ.

Very sorry for your frustration, I hope you can get it sorted out.
 
#935
I am using Terry's switch diagrams from the thread listed below and the same switch part from Digi-Key he lists there.

diyAudio Forums > Top >Amplifiers >Pass Labs >BOSOZ I/O and Switching Recommendations

Sorry I don't know how to make it a hot link.

The square silver box is a 2VR1 Corcom line filter.

Fets are isolated with grey berquist pads like on your Kook kit and nylon mounting bolts.
 
#937
Partial Success

Russ,

You steered me in the right direction. I checked resistance of FET case to heat sink and found a couple of burrs. Clean it up, change FETs and insulators and now both channels work, sort of.

The original dead channel puts out 4 V pp with a 100 mV sine wave in. The other channel only puts out .5 V pp for same input, so I have a 3 dB or so problem still to chase.

Thanks for the help so far.

Craig
 
#938
Totally OT

Well, debugging an XBOSOZ is a cinch compared to this baby. 🙂 This is my '81 Triumph TR8 which I just had to figure out why the AC would not come on. Turned out to be a 25 year old fuse in an obscenely hard to reach spot.

Right as rain now. 🙂 Well lets hope it does not rain while the top is down. 😉
 

Attachments

  • picture 057s.jpg
    picture 057s.jpg
    91 KB · Views: 570
#939
The selector switch is not tracking correctly, so I have something else to chase down. And to think I did this instead of doing my taxes.

And I would guess to avoid a lot of off topic posts, that I should not make any comments about British automotive engineering.
 
You must log in or register to reply here.
Top Bottom